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41. |
Synthesis of Dihydrophosphepin 1-Oxides by Ring Enlargement† |
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Journal of Chemical Research, Synopses,
Volume 0,
Issue 4,
1997,
Page 210-211
Gyoergy Keglevich,
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摘要:
Synthesis of Dihydrophosphepin 1-Oxides by Ring Enlargement$ Gyo�â rgy Keglevich,*a Hoang Thi Thai Thanh,a Krisztina Luda�Ê nyi,b Tibor Nova�Ê k,a Ka�Ê lma�Ê n U�Ê jsza�Ê szyc and La�Ê szlo�Ê To�Ê �Ê kea aDepartment of Organic Chemical Technology, Technical University of Budapest, 1521 Budapest, Hungary bCentral Research Institute of Chemistry for Hungarian Academy of Sciences, 1525 Budapest, Hungary cDepartment of General and Inorganic Chemistry, Eo�â tvo�â s University, 1518 Budapest, Hungary Dihydrophosphepin oxides were prepared by the ring enlargement of 1,2,3,6-tetrahydrophosphinine oxides.The phosphepin derivatives constitute a representative class of P-heterocycles.1�}3 P-Substituted phosphepin oxides are easily available by the dichlorocarbene ring enlargement of 1,2-dihydrophosphinine oxides.4 In this paper, the preparation of new dihydrophosphepin oxides from 1,2,3,6- tetrahydrophosphinine oxides is described. Tetrahydrophosphinine oxide 1a was reacted with dichlorocarbene generated from chloroform by aqueous sodium hydroxide under phase-transfer catalytic conditions. The work-up procedure, including column chromatography, a€orded the expected dichlorocarbene adduct (2a) in 71% yield, whose structure was supported by 13P and 13C NMR, as well as MS and HRMS data.The spectral data available do not justify a judgement on the sterostructure of phosphabicycloheptane 2a. Thermal examinations (TG and DTG) showed that adduct 2a su€ered cyclopropane ring opening in the temperature range 220�}250 8C.The preparative scale experiment was carried out at 220 8C for 12 min. Column chromatography of the crude product so obtained furnished 2,7-dihydrophosphepin oxide 3a in 67% yield (Scheme 1). The structure of product 3a was suggested by the 13C and 1H NMR, as well as the mass spectra. The 13C NMR spectrum revealed all skeletal carbon atoms including two methylene carbons adjacent to the phosphoryl group and four sp2 carbons of which two were CH1 units.The 13C NMR assignment shown in Table 1 was conRrmed by a spectrum obtained by the Attached Proton Test technique. Proton signals of the C50H and C60H moieties at d 6.21 and 6.09, respectively, are coupled by 10.3 Hz. The dp of 78.7 (CDCl3) for 3a is the most downReld shift ever recorded for the di€erent derivatives of phosphepine oxides. The dp values of partially or fully saturated phosphepin oxides fall in the range d 26.0�}40.7.2,5% The dp of 76.1 obtained in C6D6 for 3a eliminates the possibility of a solvent e€ect.The exact reason for the anomalous dp of 3a must wait for an explanation.} The addition of dichlorocarbene to the double bond of tetrahydrophosphinine oxide 1b led to the formation of phosphabicyclo[4.1.0]heptane 2b; partial opening of the cyclopropane ring to a 4,5-dichloromethyl-1-phenyldihydro- phosphepin oxide (m/z= 286) also occurred under the conditions of the cyclopropanation as was indicated by the 31P NMR and GC-MS spectra of the mixture. The 13C NMR spectrum of a fraction with ca. 85% purity suggested the 2,3-dihydrophosphepin (4) structure (Scheme 2). Beside the 13C NMR data (Table 1), product 4 was also character- ized by 1H and 31P NMR, as well as mass spectra. This time, the dp for the dihydrophosphepine oxide (4) is 21.3. In contrast to the mass spectrum of 2a, that of 2b did not contain the corresponding molecular ion. We could, how- ever, conRrm the molecular weight by the CI-MS technique (M a H = 323).Moreover, the correct elemental compo- sition was supported by CI-HRMS. In the last experiment a fraction of adduct 2b with a purity of ca. 80% was subjected to thermolysis at 220 8C. Flash chromatography of the crude product resulted in a fraction that contained a species with dp 78.6 as the main component.} The 13C and 1H NMR data, along with the J. Chem. Research (S), 1998, 210�}211$ Scheme 1 Scheme 2 $This is a Short Paper as deRned in the Instructions for Authors, Section 5.0 [see J.Chem. Research (S), 1998, Issue 1]; there is there- fore no corresponding material in J. Chem. Research (M). %The dp shift of 78.7 could be in accord with the structure of 7-chloro-1-methyl-3-phenyl-3-phosphabicyclo[3.2.0]hept-6-ene 3-oxide that is isomeric with dihydrophosphepin oxide 3a; this possibility should, however, be ruled out on the basis of the 13C and 1H NMR data (see Table 1 and Experimental section).*To receive any correspondence (e-mail: keglevich@oct.bme.hu). }Deoxygenation of phosphine oxide 3a by trichlorosilane at room temperature a€orded the corresponding phosphine with a downReld dp of 45.8 (C6D6). Oxidation by a slight excess of 30% hydrogen peroxide at 0 8C regenerated 3a [dp 78.6 (CDCl3)]. }According to 31P NMR spectroscopy, the thermolysis of adduct 2b gave the product with dp 78.6 quantitatively. The impurity that was essentially dihydrophosphepin oxide 4 remained unchanged during the pyrolysis. 210 J. CHEM. RESEARCH (S), 1998mass spectrum justi¢çed again the formation of 2,7-dihydro- phosphepin oxide 3a (Scheme 2). A possible explanation is that 3a may be formed from 3b by disproportionation at 220 8C. The formation of 3a was accompanied by that of a polymeric by-product that is of unknown nature. Experimental 31P, 1H and 13C NMR spectra were obtained on a Bruker DRX- 500 spectrometer (at 202.4, 500 and 125.7 MHz, respectively) with 85% phosphoric acid (external) and TMS (internal) standards in CDCl3 solutions.Coupling constants are given in Hz. Mass spectra were recorded on a MS 25-RFA instrument at 70 eV. Tetrahydrophosphinine oxides 1a and 1b were prepared as described earlier.6,7 7,7-Dichloro-1-methyl-3-phenyl-3-phosphabicylo[4.1.0]heptane 3- Oxide (2a).�¢The solution of tetrahydrophosphinine 1a (0.38 g, 1.84 mmol) and triethylbenzylammonium chloride (TEBAC) (0.14 g, 0.615 mmol) in alcohol-free chloroform (25 ml) was treated with a solution of sodium hydroxide (7.5 g, 0.188 mol) in water (7.5 ml) and the mixture stirred at the boiling point for 5 h.After ¢çltration, the organic phase was separated and made up to the original volume. After the addition of TEBAC (0.14 g, 0.615 mmol), the solution was treated with a second portion of 50% sodium hydroxide solution as above. The mixture was ¢çltered and the organic phase concentrated to give 0.38 g (71%) of 2a after column chromatography (silica gel, 3% methanol in chloroform).p 31.9; c 17.4 [JPC 5.4, C(5)], 23.3 [JPC 71.2, C(2)], 24.9 (Me), 26.3 [JPC 5.9, C(1)], 29.1 [J 66.4, C(4)], 32.0 [JPC 17.0, C(6)], 71.4 [JPC 12.3, C(7)], 128.6 [JPC 11.8, C(2)], 129.6 [JPC 9.4, C(3)], 131.5 [C(4)]; m/z (rel. int.) 288 (Ma, 6), 253 (M¢§ Cl, 100), 225 (M¢§ 28, 28), 125 [PhP(O)H, 47], 91 (22), 77 (36) (Found: Ma 288.0195, C13H15Cl2OP requires Mr 288.0238 for the 35Cl isotope). 4-Chloro-3-methyl-1-phenyl-2,7-dihydrophosphepin 1-Oxide (3a).�¢ A sample of adduct 2a (0.17 g, 0.588 mmol) was heated at 220 8C for 12 min.The crude product so obtained was puri¢çed by column chromatography (as above) to yield 0.10 g (67%) of 3a. TLC showed no impurity. P and C, Table 1; H 2.1 (s, 3 H, Me), 6.09 [dt-like m, 1 H, C(6)0H], 6.21 [d, 3JHH 10.3, 1 H, C(5)0H], 7.46¡¾7.86 (m, 5 H, Ar); m/z (rel. int.), 252 (Ma, 88), 217 (M¢§ Cl, 100), 125 [PhP(O)H, 40], 91 (39), 77 (51) (Found: Ma, 252.0419, C13H14ClOP requires Mr 252.0471 for the 35Cl isotope).Reaction of Tetrahydrophosphinin Oxide 1b with Dichloro- carbene.�¢Compound 1b was reacted with dichlorocarbene as described above for 1a. Four portions of 50% sodium hydroxide were used. The crude sample contained 72% of 2b and 28% of 4. Column chromatography a€orded a fraction consisting of ca. 80% of 2b (36%). Another fraction contained 4 in a 85% purity (15%). 2b. dP 30.9; CI-MS, m/z 323 (M a H); CI-HRMS, Ma H (Found: 323.0018, C13H15Cl3OP requires 322.9926 for the 35Cl isotope). 4.dP and dC, Table 1; dH 2.38 (s, Me, 3 H), 5.96 [d, 2JPH 8.7 Hz, C(7)0H]; m/z (rel. int.) 286 (Ma, 48), 258 (M¢§ 28, 25), 251 (M¢§ 35, 100Found: Ma 286.0134, C13H13Cl2OP requires Mr 286.0081 for the 35Cl isotope). Thermolysis of Adduct 2b.�¢2b obtained above (0.16 g, 0.40 mmol, purity ca. 80%) was thermolysed as described above for 2a. Repeated column chromatography (as above) yielded 0.027 g (24%) of 3a in a purity of 90%. OTKA support of this work is acknowledged (grant.no. T 014917). Gy. K. is grateful to Professor Louis D. Quin (University of Massachusetts) for giving advice. Received, 11th September 1997; Accepted, 17th December 1997 Paper E/7/06625B References 1 M. Pabel and S. B. Wild, in Comprehensive Heterocyclic Chemistry II, ed. A. R. Katritzky, C. W. Rees and E. F. V. Scriven, Elsevier, New York, 1996, vol. 9(ch). 2 L. D. Quin, in The Heterocyclic Chemistry of Phosphorus, Wiley, New York, 1981, pp. 181¡¾191 and pp. 256¡¾257. 3 Gy. Keglevich, Synthesis, 1993, 931. 4 Gy. Keglevich, F. Janke, J. Brlik, I. PetnehaA zy, G. ToA th and L. ToA A ke, Phosphorus Sulfur Relat. Elem., 1989, 46, 69. 5 T. J. Katz, C. R. Nicholson and C. A. Reilly, J. Am. Chem. Soc., 1966, 88, 3832. 6 Gy. Keglevich, T. NovaA k, Tungler, L. HegeduA A s, A A . Szo E lloA A sy, K. LudaA nyi and L. ToA A ke, J. Chem. Res. (S), 1997, 290. 7 Gy. Keglevich, Zs. Bo E cskei, K. U A jszaA szy and L. To A A ke, Synthesis, 1997, in press. Table 1 31P and 13C NMR data for the dihydrophosphepin oxides dC (JPC) Compound dP C(2) C(3) C(4) C(5) C(6) C(7) Me C(1')a C(2')a C(3')a C(4')a 3a 78.7 31.6 125.9b 129.4b 131.7c 126.0c 38.1 22.4 132.4 128.7d 129.8d 132.4 (63.6) (6.0) (9.2) (4.5) (10.6) (65.6) (86.1) (10.8) (8.6) (2.2) 4 21.3 28.4 29.4 121.2 134.6 153.5 122.8 25.2 128.8d 130.3d 132.1 (69.3) (5.7) . (12.1) . (93.9) (11.9) (12.1) (10.4) . aPrimed numbers represent the aromatic carbon atoms. bC(3) and C(4) may be reversed. cC(5) and C(6) may be reversed. dC(2') and C(3') may be reversed. J. CHEM. RESEARCH (S), 1998 2
ISSN:0308-2342
DOI:10.1039/a706625b
出版商:RSC
年代:1998
数据来源: RSC
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42. |
Solid Supported Reagents and Reactions. Part 21.1Rapid and Clean Synthesis of Thiols from Halides Using Polymer-supported Hydrosulfide†‡ |
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Journal of Chemical Research, Synopses,
Volume 0,
Issue 4,
1997,
Page 212-213
Babasaheb P. Bandgar,
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摘要:
Solid Supported Reagents and Reactions. Part 21.1Rapid and Clean Synthesis of Thiols from HalidesUsing Polymer-supported Hydrosulfide$%Babasaheb P. Bandgar*a and Sanjay B. PawarbaOrganic Chemistry Research Laboratory, School of Chemical Sciences, Swami Ramanand TeerthMarathwada University, Dnyanteerth, Vishnupuri Post Box No. 87, Nanded-431 602,Maharashtra, IndiabDepartment of Chemistry, R.B.N.B. College, Shrirampur-413 709, IndiaA variety of thiols are prepared from corresponding halides using polymer-supported hydrosulfide in excellent yields.Isolation of pure products by simple filtration and evaporation is an important feature of this method.Thiols are important not only for their use in the synthesisof organosulfur compounds but also for their roles in cellbiochemistry. Therefore, many synthetic methods have beendeveloped.2,3 Although direct preparations of thiols fromalkyl halides and metal suldes would be straightforward,direct methods give only a moderate yield of thiolsaccompanying a considerable amount of dialkyl sulde.2Therefore, indirect methods involving thiourea,2 xanthate2and thioacetate2 are commonly utilized for the synthesisof thiols and other new indirect methods have beenreported.4¡Ó9 These indirect methods usually give around80% yield and no dialkyl suldes or other undesired by-products; however, intermediates have to be transformedto thiols by hydrolysis with base5¡Ó9 or by reduction withlithium aluminium hydride.10,11 Recently thiols have beenprepared in quantitative yield from the corresponding thio-acetates via Pd-catalyzed methanolysis with borohydrideexchange resin under mild and neutral conditions.2We now report on an exceedingly simple method for thedirect synthesis of thiols from halides using hydrosuldeexchange resin (Scheme 1).It is important to note that thismethod produces thiols in excellent yields (93¡Ó98%) withoutany trace of dialkyl suldes.3The synthesis of thiols from alkyl halides and NaSHalways results in the formation of dialkyl suldes12because any alkyl thiols formed initially further react withexcess alkyl halides.However, Tulsion A-77-supportedhydrosulde has more nucleophilic character than NaSHand therefore alkyl halides react with hydrosulde exchangeresin much faster than NaSH giving corresponding thiolswithin a very short time (15 min) at 25 8C. Thus theformation of dialkyl suldes as by-products is avoided.Tertiary alkyl halides (entries c and d in Table 1) are alsosmoothly converted into corresponding thiols at 25 8C.These reactions not only proceed with unique chemo-selectivity but also give excellent yields of thiols comparedto those prepared by indirect methods.4¡Ó9 The isolation ofpure products by simple ltration and evaporation is animportant feature of this method.The recovered resin canbe recycled in the process after regeneration by treatmentwith dilute HCl.ExperimentalAll reactions were conducted in oven-dried asks.Solvents weredistilled before use. All chemicals were of analytical grade.Reactions were monitored by TLC. The strongly anionic exchangeresin, Tulsion A-27 (Cl£¾) was procured from Thermax Chemicals,Pune.Preparation of Hydrosulde Exchange Resin.To a solution ofNaSH (50 mmol) in MeOH (50 ml), Tulsion A-27 (chloride form)(10 g) was added and the mixture was shaken for 1 h. The resin wasltered o and washed with distilled water until it was free from Cl£¾and excess NaSH.The resin was then washed with methanol,diethyl ether and dried under vacuum at 50 8C for 2 h. The capacityJ. Chem. Research (S),1998, 212¡Ó213$Scheme 1Table 1 Synthesis of thiols from halides at 25 8CYield mp/bp (Torr)Entry Halide Product (%) (Lit.) (8C)a Me[CH2]2CH2Br Me[CH2]2CH2SH 98 97 (760mm)[96¡Ó97(760mm)]13b Me[CH2]2CH2I Me[CH2]2CH2SHa 93 97 (760mm)[96¡Ó97(760mm)]13c Me3CBr Me3CSH 96 63 (760mm)[61.60(700.8 mm)]14d Me3CCl Me3CSH 95 63 (760mm)[61.60(700.8 mm)]14e 98 194 (760mm)[192¡Ó194(760mm)]11f 93 103 (12mm)[105(10 mm)]15g 97 121 (14mm)[123¡Ó125(10 mm)]15h 97 58[58]16i 96 43[44]17aThe reaction was carried out at 0 8C.$This is a Short Paper as dened in the Instructions for Authors,Section 5.0 [see J.Chem. Research (S), 1998, Issue 1]; there is there-fore no corresponding material in J. Chem. Research (M).%This paper has been dedicated to Professor M. S. Wadia(University of Pune) on the occasion of his 60th birthday.*To receive any correspondence.212 J.CHEM. RESEARCH (S), 1998of hydrosul¢çde exchange resin was found to be 2 mmol g¢§1 of dry resin. General Procedure for the Synthesis of Thiols from Halides.�¢A mixture of halide (10 mmol) in acetonitrile (20 ml) and hydrosul¢çde exchange resin (5 g for monohalides and 10 g for dihalides) was shaken for 15 min at 25 8C. The reaction was monitored by TLC. The resin was ¢çltered o€ and washed with ether (310 ml). Removal of the solvent under reduced pressure gave thiols in excellent yields.We thank Thermax Chemicals, Bhosari, Pune for the generous gift of Tulsion A-27 (chloride form). Received, 7th October 1997; Accepted, 22nd December 1997 Paper E/7/07241D References 1 For part 20, see B. P. Bandgar and M. M. Naik, Synth. Commun., accepted for publication. 2 J. Choi and N. M. Yoon, Synth. Commun., 1995, 25, 2655. 3 J. Choi and N. M. Yoon, Synthesis, 1995, 373. 4 K. Hojo, H. Yoshino and T. Mukaiyama, Chem. Lett., 1977, 437. 5 M. Yamada, K. Sotoya and T. Sakakibara, J. Org. Chem., 1977, 42, 2180. 6 K. Inomata, H. Yamada and H. Kotake, Chem. Lett., 1981, 1475. 7 P. Molina, M. Alajarin and M. J. Yillaplana, Tetrahedron Lett., 1985, 26, 469. 8 D. N. Harp and M. Kabayashi, Tetrahedron Lett., 1986, 27, 3975. 9 M. Gingras and D. N. Harp, Tetrahedron Lett., 1990, 31, 1397. 10 C. Ganter and N. Wigger, Helv. Chim. Acta, 1972, 55, 481. 11 P. A. Bobbio, J. Org. Chem., 1961, 26, 3023. 12 L. M. Ellis Jr. and E. E. Reid, J. Am. Chem. Soc., 1932, 54, 1674. 13 B. C. Cossar, J. O. Fournier, D. L. Fields and D. D. Reynolds, J. Org. Chem., 1962, 27, 93. 14 S. Mathias, J. Am. Chem. Soc., 1950, 72, 1897. 15 M. Kulka, Can. J. Chem., 1956, 34, 1093. 16 W. J. Horn, J. Am. Chem. Soc., 1921, 43, 2603. 17 J. J. Mayerle, S. E. Denmark, B. V. DePamphilis, J. A. Ibers and R. H. Holm, J. Am. Chem. Soc., 1975, 97, 1032. J. CHEM. RESEARCH (S), 1998 2
ISSN:0308-2342
DOI:10.1039/a707241d
出版商:RSC
年代:1998
数据来源: RSC
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43. |
Steric Reversal of theendo-Selectivity Effect in 1,3-Dipolar Cycloadditions of Phthalazinium-2-ylides withN-Substituted Maleimides:endo- andexo-1,2-(Dicarboxy-N-substituted imido)-1,2,3,10b-tetrahydropyrrolo[2,1-a]phthalazines† |
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Journal of Chemical Research, Synopses,
Volume 0,
Issue 4,
1997,
Page 214-215
Richard N. Butler,
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摘要:
Steric Reversal of the endo-Selectivity Effect in1,3-Dipolar Cycloadditions of Phthalazinium-2-ylideswith N-Substituted Maleimides: endo- and exo-1,2-(Dicarboxy-N-substituted imido)-1,2,3,10btetrahydropyrrolo[2,1-a]phthalazines$Richard N. Butler* and Derval M. FarrellChemistry Department, University College Galway, IrelandN-Methyl- and N-aryl-maleimides undergo cycloadditions with phthalazinium-2-dicyanomethanide and -2-unsubstitutedmethanide 1,3-dipoles to give exclusive or predominant endo-cycloadducts but with N-tert-butylmaleimide this endoeffect is reversed to favour the exo-cycloadducts exo-1,2-(dicarboxy-N-tert-butylimido)-1,2,3,10b-tetrahydropyrrolo[2,1-a]phthalazines 11 and 15.The transition state factors which direct the stereocourseof many Diels¡ÓAlder and 1,3-dipolar cycloadditions tofavour endo-cycloadducts, such as bonding secondary orbitalinteractions, favourable alignments of dipole momentsand others, have aroused considerable interest.1¡Ó3 Anti-bonding secondary orbital interactions may alter the reac-tion to exo-selective4 and in cases where the endo-selectivityis delicately balanced a variety of secondary factors can leadto mediocre endo- and exo-selectivities.3,5¡Ó10 Catalysts mayalso reverse the endo eect.11,12 Recently13 we have exam-ined the cycloadditions of the phthalazinium-2-methanide1,3-dipoles 1 and 2 with a range of alkyne and alkenedipolarophiles and a preference for endo-cycloadditionswas noted.Herein we explore this eect with a series of N-substituted maleimide dipolarophiles.For these systems theendo eect required the absence of steric hindrance in thecycloaddition and it depended also on the stability andhence selectivity of the dipole. A large steric eect in thedipolarophile reversed the endo eect and gave an exclusiveexo-cycloaddition.The 1,3-dipole 1 is a stable solid while species 2 is highlyunstable and decomposes rapidly even at £¾30 8C andcan only be generated and trapped in situ.13 When dipole 1was separately treated with N-methyl-, N-phenyl- andN-( p-nitrophenyl)-maleimide in acetonitrile at ambienttemperatures the exclusive endo-cycloadducts 3, 4 and 5respectively were formed (Scheme 1; Table 1, entries 1¡Ó3).In these reactions steric hindrance did not overcome thesecondary factors which favour the endo-cycloaddition andthe electronic substituent inuence of varying from NMe toNC6H4NO2-p did not aect the endo-selectivity.Howeverwith N-tert-butylmaleimide as dipolarophile to the dipole 1steric inhibition swamped the endo eect and the reactionwas exclusively switched over to the exo product 11 (Table 1,entry 4).A similar trend was observed with the unstabledipole 2 but in this case endo/exo mixtures were encounteredin each case with the balance being turned from predomi-nantly endo to predominantly exo by the N-tert-butyl substi-tuent (Table 1, entries 5¡Ó8). These results illustrate theJ. Chem.Research (S),1998, 214¡Ó215$Table 1 CycloadductsYield YieldEntrya Compd. Mp/8C (%) Compd. Mp/8C (%)endo exo1 3 233¡Ó235b 94d ¡V ¡V <12 4 252¡Ó254b 87d ¡V ¡V <13 5 148¡Ó150c 89d ¡V ¡V <14 6 ¡V <1 11 157¡Ó159c 80d5 7 164¡Ó165b 48 12 124¡Ó126b 256 8 208¡Ó210b 46 13 105¡Ó107b 257 9 190¡Ó192b 52 14 162¡Ó164b 258 10 202¡Ó204b 25(8)e 15 218¡Ó220b 49(16)eaEntries 1¡Ó4 from dipole 1; entries 5¡Ó8 from dipole 2. bFrom ethanol. cFrom acetonitrile. dExclusive products;remainder was recovered 1.eParentheses contain conversion yields. Reaction yields are corrected for recovery ofstarting material.importance of steric eects and the stability/selectivity ofthe dipole in the endo eect. The more unstable and lessselective dipoles 2 gave endo/exo mixtures rather than exclu-sive endo- or exo-cycloaddition. With the stable dipole 1 theScheme 1 Some 1H NMR shifts shown for Y Me, R H$This is a Short Paper as dened in the Instructions for Authors,Section 5.0 [see J.Chem. Research (S), 1998, Issue 1]; there is there-fore no corresponding material in J. Chem. Research (M).*To receive any correspondence (e-mail: r.debuitleir@ucg.ie).214 J. CHEM. RESEARCH (S), 1998endo eect required minimum steric constraints from thedipolarophile.The stereoisomeric products were not interconvertible andtheir structures were established from microanalyses, IR, 1Hand 13C NMR spectra which showed all of the expectedsignals and splitting patterns.The endo-isomers 3¡Ó10 werereadily distinguished by (a) NOE dierence spectra whichshowed NOE enhancements of 12¡Ó25% between the cisprotons at C-10b and C-1 and (b) J values of 8¡Ó10Hzbetween these same protons conrming the cis alignmentwith a small dihedral angle. The exo-isomers 11¡Ó15 did notshow NOE enhancements between the trans H atoms atC-10b and C-1 and they showed reduced J values of5¡Ó7.5 Hz conrming the trans alignment with a largerdihedral angle. The H-10b proton in structures 11¡Ó15 alsoshowed a shielding eect from the cis-imido unit (Scheme1).Also, H atoms or Me groups lying endo to the plane ofthe phthalazine ring current showed more upeld (shielded)signals than those in the exo positions (Scheme 1).ExperimentalMps were measured on an Electrothermal apparatus. IR spectrawere measured with a Perkin Elmer 983G spectrophotometer andmicroanalyses on a Perkin Elmer model 240 CHN analyser. NMRspectra were measured on a JEOL GXFT 400 instrument usingCDCl3 or (CD3)2SO2 as solvent.Dipole 1 was prepared and dipole2 generated in solution from salt 2A as previously described.13 Thefollowing are typical examples of cycloaddition reactions.endo-1,2(Dicarboxy-N-methylimido)-3,3-dicyano-1,2,3,10b-tetra-hydropyrrolo[2,1-a] phthalazine 3 (Table 1, entry 1).A suspensionof compound 1 (0.35 g, 1.8 mmol) in acetonitrile (15 ml) was treatedwith N-methylmaleimide (0.2 g, 1.8 mmol) and the mixture stirred atambient temperature for 12 h.Removal of solvent under reducedpressure yielded compound 3 (94%); mp 233¡Ó235 8C (from ethanol)(Found: C, 68.4; H, 3.6; N, 19.7. C16H11N5O2 requires C, 68.7; H,3.5; N, 19.9%); max(mull)/cm£¾1, 2305 (C2N), 1785, 1716 (C1O);H ([2H5]DMSO), 2.89 (3 H, s, CH3), 4.31 (1 H, m, H-1), 4.57 (1 H,d, J= 8.1 Hz, H-2), 5.00 (1 H, d, J= 7.3 Hz, H-10b), 7.55¡Ó7.70(3 H, m, H-7 to H-9), 7.85 (1 H, d, H-10), 8.01 (1 H, s, H-6); C[2H6]DMSO), 25.3 (CH3), 43.4 (C-2), 50.1 (C-1), 58.4 (C-3), 58.7(C-10b), 110.9 and 112.1 (C2N), 124.0 (C-10a), 130.2 (C-6a), 127.0,127.7 and 129.1 (C-8 to C-10), 131.6 (C-7), 147.6 (C-6), 171.1 and173.2 (C1O).exo-1,2-(Dicarboxy-N-tert-butylimido)-3,3-dicyano-1,2,3,10b-tetra-hydropyrrolo[2,1-a] phthalazine 11 (Table 1, entry 4).A suspensionof compound 1 (0.35 g, 1.8 mmol) in acetonitrile (15 ml) was treatedwith N-tert-butylmaleimide (0.28 g, 1.8 mmol), and the mixturestirred at ambient temperature for 12 h.Removal of the solventunder reduced pressure yielded compound 11 (80%); mp 157¡Ó159 8C (from acetonitrile) (Found: C, 65.4; H, 4.7; N, 20.0.C19H17N5O2 requires C, 65.7; H, 4.9; 20.2%); max(mull)/cm£¾1, 2290(C2N), 1696, 1718 (C1O); H ([2H5]DMSO): 2.17 (9 H, s, Butprotons), 3.93¡Ó3.96 (1 H, dd, H-1), 4.56 (1 H, d, J=8.1 Hz, H-2),4.82 (1 H, d, J =5.1 Hz, H-10b), 7.43¡Ó7.58 (3 H, m, H-7 to H-9),7.73 (1 H, d, J= 15.8 Hz, H-10), 8.12 (1 H, s, H-6); C([2H6]DMSO): 38.9¡Ó40.1 (But CH3 overlapping with solvent peaks),43.9 (C-2), 53.4 (C-1), 54.3 [But C(CH3)3], 58.9 (C-3), 69.4 (C-10b),118.8 (C2N), 125.2 (C-10a), 124.5, 126.3, 128.8 (C-8 to C-10),131.1 (C-6a), 134.1 (C-7), 142.9 (C-6), 168.4 and 173.9 (C1O).exo-1,2-(Dicarboxy-N-p-nitrophenylimido)-1,2,3,10b-tetrahydro-pyrrolo[2,1-a] phthalazines 14 and the endo isomer 9 (Table 1, entry7).A solution of triate salt 2A (0.35 g, 0.96 mmol) and N-( p-nitrophenyl)maleimide (0.42 g, 1.91 mmol) in dry dichloromethane(20 ml) under anhydrous conditions was treated with an excess ofcaesium uoride (0.40 g, 2.63 mmol) and stirred at ambient tempera-ture for 24 h.The resulting mixture was ltered and the ltrate(together with CH2Cl2, lter-cake washings) evaporated underreduced pressure to 4 cm3, placed on a ash column of silica gel(230¡Ó400 mesh ASTM) packed with dichloromethane and elutedwith mixtures of dichloromethane¡Ódiethyl ether having gradientvariations of 5% from 100:0 to 50:50 v/v. The rst product elutedfrom the column was compound 14 (25%); mp 162¡Ó164 8C (fromethanol) (Found: C, 62.8; H, 3.7; N, 15.2.C19H14N4O4 requires C,63.0; H, 3.9; N, 15.5%); max(mull)/cm£¾1: 1715 (C1O), H (CDCl3):3.55¡Ó3.67 (3 H, m, H-3endo, H-2, H-1), 4.35¡Ó4.42 (2 H, m, H-10b,H-3exo), 7.27¡Ó7.64 (7 H, m, Ho of N-C6H4NO2 and H-6 to H-10),8.34 (2 H, d, Hm of N-C6H4NO2), C (CDCl3): 44.2 (C-2), 50.6(C-1), 57.7 (C-3), 61.5 (C-10b), 123.5 (C-10a), 131.1 (C-6a), 131.5(C-7), 140.8 (C-6), 125.8, 126.4, 129.2 (C-8 to C-10), 136.9, 124.4,126.9, 147.0 (N-C6H4NO2, C-1', C-2', C-3', C-4' resp.), 174.7 and175.2 (C1O).Compound 9 was subsequently eluted from the column (52%);mp 190¡Ó192 8C (from ethanol) (Found: C, 62.8; H, 3.7; N, 15.2.C19H14N4O4 requires C, 63.0; H, 3.9; N, 15.5%); max(mull)/cm£¾1:1715 (C1O); dH (CDCl3): 3.54¡Ó3.70 (3 H, m, H-3endo, H-2, H-1),4.53 (1 H, d, J= 12.4 Hz, H-3exo), 4.75 (1 H, d, J =7.6 Hz,H-10b), 7.19¡Ó7.69 (7 H, m, H-6 to H-10 and Ho of N-C6H4NO2),8.25 (2 H, d, Jm of C6H4NO2); dC (CDCl3): 43.8 (C-2), 48.5 (C-1),58.9 (C-3), 60.4 (C-10b), 121.9 (C-10a), 126.9 (C-6a), 127.8 (C-7),138.7 (C-6), 124.4, 124.7, 129.6 (C-8 to C-10), 135.9, 122.7, 125.5,145.1 (N-C6H4NO2, C-1', C-2', C-3', C-4' resp.), 171.9 and 174.7(C1O).Received, 17th November 1997; Accepted, 24th December 1997Paper E/7/08237AReferences1 For a review see: L.Ghasez, Stereocontrolled Organic Synthesis,ed. B. M. Trost, Blackwell Scientic Publications, Oxford, 1994,pp. 200¡Ó210.2 R. B. Woodward and R. F. Homann, Angew. Chem., Int. Ed.Engl., 1969, 8, 781.3 O. Gunner, R. Ottenbrite, D. Shillady and P. Alston, J. Org.Chem., 1988, 53, 5348.4 R. Cookson, B. Drake, J. Hudel and A. Morrison, J. Chem.Soc., Chem. Commun., 1966, 15.5 M. Ansell and A. Clements, J. Chem. Soc. (C), 1971, 275.6 T. Cohen, A. Mura, D. Shull, E. Fogel, R. Runer and J. Falck,J. Org. Chem., 1976, 41, 3218.7 L. Overman, G. Taylor, K. Houk and L. Donelsmith, J. Am.Chem. Soc., 1978, 100, 3182.8 Y. Kobuke, T. Sugimoto, J. Furukawa and T. Fueno, J. Am.Chem. Soc., 1970, 92, 6548.9 Y. Kobuke, T. Sugimoto, J. Furikawa and T. Fueno, J. Am.Chem. Soc., 1972, 94, 1587.10 T. Sugimoto, Y. Kobuke and J. Furukawa, Tetrahedron Lett.,1976, 1587.11 S. Danishefsky, E. Larson, D. Askin and N. Kato, J. Am.Chem. Soc., 1985, 107, 1246.12 S. Danishefsky, K. H. Chao and G. Schultz, J. Org.Chem., 1985, 50, 4650; J. Motoyoshiya, T. Kameda, M. Asari,M. Miyamoto, S. Narita, H. Aoyama and S. Hayashi, J. Chem.Soc., Perkin Trans. 2, 1997, 1845.13 R. N. Butler, D. M. Farrell and C. S. Pyne, J. Chem. Res. (S),1996, 418.J. CHEM. RESEARCH (S), 1998 215
ISSN:0308-2342
DOI:10.1039/a708237a
出版商:RSC
年代:1998
数据来源: RSC
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44. |
Solid–Liquid Phase-transfer Catalytic Synthesis of Chiral Glycerol Sulfide Ethers Under Microwave Irradiation† |
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Journal of Chemical Research, Synopses,
Volume 0,
Issue 4,
1997,
Page 216-217
Jing-Xian Wang,
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摘要:
Solid�}Liquid Phase-transfer Catalytic Synthesis of Chiral Glycerol Sulfide Ethers Under Microwave Irradiation$ Jing-Xian Wang,* Yumei Zhang, Danfeng Huang and Yulai Hu Institute of Chemistry, Department of Chemistry, Northwest Normal University, 95 An Ning Road(E.), Lanzhou 730070, China Epoxypropoxyphenols react with benzenethiols under phase-transfer catalysis and microwave irradiation to give chiral glycerol sulfide ethers, this procedure is simple, rapid and efficient. The rapid heating of foodstu€s in microwave ovens is routinely used by mankind.However, people have recognized other potential applications for this method of heating and scientists engaged in a number of disciplines have applied the rapid heating associated with microwave technology to a number of useful processes. These include the preparation of samples for analysis, applications to waste treatment, polymer technology, drug release/targeting, ceramics and alkane decomposition processes, hydrolysis of proteins and peptides inorganic and solid-state synthesis.So it is organic synthesis which beneRts signiRcantly from this technology.1�}3 Our work involves the synthesis of chiral glycerol sulRde ethers in a modiRed commercial microwave oven. In the past, Iizawa et al.4 have reported the synthesis of 3-hydroxy-3-(phenylthio)propyl phenyl ether under normal conditions. However, they have synthesied only one isomer and since these compounds can be separated into two kinds of chiral compounds, they may have some biological activity, so it is very interesting to investigate these com- pounds.We have now found that chiral glycerol sulRde ethers can be obtained from epoxypropoxyphenols and benzenethiols using microwave irradiation. This method is simple, rapid and a€ords good yields. It takes only 8 min for the reaction to Rnish (compared to 5 h for the synthesis by Iizawa et al.4). The reactions are shown in Scheme 1 and the results are summarized in Table 1.Since atomic sulfur is easily polarized, the e€ect of the R1 groups of substituted benzenethiols is important in deter- mining the yield of the chiral glycerol sulRde ethers. When the substituted benzenethiol contains an eletron-releasing group such as Me, the yield of the corresponding glycerol sulRde ether is high (73%), and when the substituent is an electron-withdrawing group such as NO2 the yield of the corresponding glycerol sulRde ether is low.Using the reaction of PhCH2SH with epoxypropoxy- phenol as an example, we investigated the e€ect of phase- transfer catalysts (PTC) on the reaction. When PEG-400 (or PEG-600) was used as a phase-transfer catalyst, the yield of the glycerol sulRde ether is high (89.3%) whereas the yield is only 67.6% without any PTC. The eciency of several PTCs studied is in the order PEG-4001PEG-600 > Bu4NBr > Me4NI. The e€ect of various solvents used in the formation of chiral glycerol sulRde ethers was studied and DMF was found to be the best solvent for the reactions.This is because DMF is a polar solvent and it's boiling point is high, it can eciently absorb microwave energy, also sodium aryl thiolates are soluble in DMF. Other solvents were studied for these reactions and their suitability are in the order DMF> EtOH >butanol >acetone. Power and reaction time also in�Puence the yield of the glycerol sulRde ethers which is greatest at 750 W and 8 min.Experimental Infrared spectra were measured as KBr discs (or liquid Rlm) using an Alpha Centauri FT-IR spectrophotometer, 1H NMR spectra (80 MHz) were recorded in CDCl3 [or (CD3)2CO] using an FT-80 spectrometer, mass spectra were obtained on a Nippon Shimadzu QP-1000 GC-MS spectrometer. Microwave irradiations are carried out in a modiRed Galanz WP 750B commercial microwave oven at 2450 MHz. General Procedure.DIn a typical experiment, the benzenethiol (5.4 mmol), sodium hydroxide (0.4 g, 9.6 mmol), PEG-400 (0.1 g) and DMF (10 ml) were added in a bottle (100 ml), and then re�Puxed under microwave irradiation with 100% power (750 W).After 1 min a mixture of the epoxypropoxyphenol5,6 (5.8 mmol) and DMF (2 ml) was added dropwise over a period of 1.5 min and irradiated continuously for 5.5 min. The solid was Rltered o€ and the Rltrate taken to dryness under reduced pressure. The residue was acidiRed with dilute HCl and extracted with diethyl ether and the solution dried over MgSO4.After Rltration, the diethyl was evaporated to yield crude product which was chromatographed on silica gel J. Chem. Research (S), 1998, 216�}217$ Scheme 1 $This is a Short Paper as deRned in the Instructions for Authors, Section 5.0 [see J. Chem. Research (S), 1998, Issue 1]; there is there- fore no corresponding material in J. Chem. Research (M). *To receive any correspondence. 216 J. CHEM. RESEARCH (S), 1998[eluent: light petroleum (bp 60¡¾90 8C)¡¾ethyl acetate (16:1 v/v)] or crystallized.Received, 10th November 1997; Accepted, 12th January 1998 Paper E/7/08058A References 1 S. Caddick, Tetrahedron, 1995, 51, 10403. 2 C. R. Strauss and R. W. Trainor, Aust. J. Chem., 1995, 48, 1665. 3 K. D. Raner, C. R. Strauss, R. W. Trainor and J. S. Thorn, J. Org. Chem., 1995, 60, 2456. 4 T. Iizawa, A. Goto and T. Nishikubo, Bull. Chem. Soc. Jpn., 1989, 62, 597. 5 Jin-Xian Wang, Manli Zhang and Yulai Hu (Submitted for publi- cation). 6 S. S. JovanovicA , M. M. Mis I icA -VukovicA , D. D. DjokovicA and D. S. Bajic, J. Mol. Catal., 1992, 73, 9. Table 1 Preparation of chiral glycerol sulfide ethers (5a-o) Reaction Found (calcd) (%) Compound time/ min Mp/8C Yield (%) Molecular formula C H O S max/cm¢§1 (KBr) dH (CDCl3, Me4Si) MS (m/z) 5a 8 Oil 92 C15H16O2S 69.46 (69.23) 6.19 (6.15) 12.04 (12.31) 12.44 (12.31) 3426, 2926, 1599, 1244, 690 2.49 (s, 1 H, OH), 3.21 (m, 2 H, Ha), 4.09 (m, 3 H, Hb), 6.81¡¾7.49 (m, 10 H, aromatic) 260 (Ma) 5b 8 Oil 73 C16H18O2S 70.06 (70.07) 6.30 (6.57) 12.20 (11.68) 11.44 (11.68) 3426, 2923, 1599, 1588, 690, 2871 1.26 (s, 1 H, OH), 3.13 (m 2 H, Ha), 4.04 (m, 3 H, Hb), 6.81¡¾7.92 274 (Ma) 5c 8 53.2¡¾ 53.9 90 C17H20O2S 70.82 (70.83) 6.68 (6.94) 11.39 (11.11) 11.11 (11.11) 3575, 2919, 1610, 1585, 1243, 631 2.28 (d, 6 H, CH3), 2.72 (s, 1 H, OH), 3.17 (m, 2 H, Ha), 4.01 (s, 3 H, Hb), 6.71¡¾7.38, (m, 8 H, aromatic) 288 (Ma) 289 (M a 1) 5d 8 Oil 91 C19H18O2S 73.37 (73.55) 5.72 (5.81) 10.40 (10.32) 10.51 (10.32) 3427, 2926, 1590, 1564, 1244, 690 2.72 (s, 1 H, OH), 3.28 (m, 2 H, Hb), 4.04 (s, 3 H, Ha), 6.77¡¾8.50, (m, 12 H, aromatic) 310 (Ma) 5e 8 Oil 79 C23H20O2S 76.61 (76.67) 5.61 (5.56) 8.71 (8.89) 9.07 (8.89) 3406, 2927, 1595, 1580, 1241, 665 2.37 (s, 1 H, OH), 3.35 (m, 2 H, Ha), 4.21 (m, 3 H, Hb), 6.65¡¾8.51, (m, 14 H, aromatic) 360 (Ma) 5f 8 121¡¾ 122 88.9 c20H18O4S 67.79 (67.80) 5.04 (5.08) 18.08 (18.08) 9.11 (9.04) 3445, 1690, 1596, 1580, 2930, 1243, 645 3.37 (m, 2 H, Ha), 4.41 (m, 3 H, Hb), 4.95 (s, 2 H, CO2H a OH), 6.75¡¾8.81 (m, 11 H, aromatic) 354 (Ma) 5g 8 Oil 75 C20H20O2S 74.19 (74.07) 5.99 (6.17) 9.77 (9.88) 10.05 (9.88) 3427, 2023, 1587, 1613, 1382, 601 2.26 (s, 3 H, CH3), 2.43 (s, 1 H, OH), 3.26 (m, 2 H, Ha), 3.26 (m, 2 H, Ha), 6.67¡¾8.49 (, 11 H, aromatic) 324 (Ma) 5h 8 54.5¡¾ 55.2 89.3 C16H18O2S 69.92 (70.07) 6.53 (6.57) 11.74 (11.68) 11.81 (11.68) 3394, 2926, 1599, 1587, 1492, 1244, 687 1.63 (s, 1 H, OH), 2.74 (m, 2 H, Ha), 3.78 (m, 2 H, Ha), 4.01 (s, 3 H, Hb), 6.84¡¾7.40 (m, 10 H, aromatic) 274 (Ma) 5i 8 Oil 67 C19H18O2S 73.25 (73.55) 5.80 (5.81) 10.53 (10.32) 10.40 (10.32) 3422, 2927, 1595, 1580, 1241, 690 2.56 (s, 1 H, OH), 3.31 (m, 2 H, Ha), 4.23 (m, 3 H, Hb), 6.70¡¾8.27 (m, 12 H, aromatic) 310 (Ma) 5j 8 55¡¾ 55.9 70 C17H20O2S 70.96 (70.83) 6.69 (6.94) 11.14 (11.11) 11.21 (11.11) 2920, 1613, 1585, 1512, 1379, 1242, 700 1.60 (s, 1 H, OH), 2.29 (s, 3 H, CH3), 2.69 (m, 2 H, Ha), 3.76 (s, 2 H, Hb), 3.98 (s, 3 H, Hb), 6.73¡¾7.31 (m, 9 H, aromatic) 288 (Ma) 5k 8 52¡¾ 52.6 97 C16H18O2S 70.19 (70.07) 6.56 (6.57) 11.43 (11.68) 11.82 (11.68) 3574, 2917, 1582, 1611, 160244, 688 2.28 (s, 3 H, CH3), 2.48 (s, 1 H, OH), 3.20 (m, 2 H, Ha), 6.71¡¾7.41 (m, 9 H, aromatic) 264 (Ma) 5l 8 Oil 82.4 C20H20O2S 74.12 (74.07) 6.08 (6.17) 10.11 (9.88) 9.69 (9.88) 3419, 2873, 2923, 1596, 1580, 572 2.28 (s, 3 H, CH3), 3.25 (m, 2 H, Ha), 4.21 (s, 3 H, Hb), 6.67¡¾8.29 (m, 11 H, aromatic) 324 (Ma) 5m 8 111¡¾ 111.7 94 C16H16O4S 62.92 (63.16) 4.98 (5.26) 21.53 (21.05) 10.57 (10.53) 3191, 2923, 1690, 1587, 1563, 1496, 685 3.30 (m, 2 H, Ha), 4.26 (m, 3 H, Hb), 5.75 (s, 2 H, CO2H a OH), 6.85¡¾ 8.11 (m, 9 H, aromatic) 304 (Ma) 5n 8 62¡¾ 62.5 80 C20H20O2S 74.46 (74.07) 5.96 (6.17) 9.51 (9.88) 10.07 (9.88) 3500, 2926, 1620, 1595, 1580, 1243, 700 2.48 (s, 1 H, OH), 2.81 (m, 2 H, Ha), 3.79 (s, 2 H, Ha), 4.18 (m, 3 H, Hb), 6.74¡¾8.22 (m, 12 H, aromatic) 324 (Ma) 5o 8 113¡¾ 114 66.7 C17H18O4S 64.21 (64.15) 5.57 (5.66) 20.41 (20.13) 9.81 (10.06) 3503, 2925, 1674, 1588, 1563, 1514, 1256, 690 2.28 (s, 3 H, CH3), 3.28 (m, 2 H, Ha), 4.10 (m, 3 H, Hb), 5.45 (s, 2 H, CO2H a OH), 6.75¡¾8.14 (m, 8 H, aromatic) 318 (Ma) J.CHEM. RESEARCH (S), 1998 217
ISSN:0308-2342
DOI:10.1039/a708058a
出版商:RSC
年代:1998
数据来源: RSC
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45. |
Yield and Pore-size Distribution of Pyrolysis Products of Organic Compounds as Chemical Modifiers in Electrothermal Graphite Furnace Atomic Absorption Spectrometry† |
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Journal of Chemical Research, Synopses,
Volume 0,
Issue 4,
1997,
Page 218-219
Shoji Imai,
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摘要:
Yield and Pore-size Distribution of PyrolysisProducts of Organic Compounds as ChemicalModifiers in Electrothermal Graphite Furnace AtomicAbsorption Spectrometry$Shoji Imai,*a Yasuko Nishiyamab and Yasuhisa HayashibaDepartment of Chemistry, Faculty of Integrated Arts and Sciences, The University of Tokushima,Tokushima 770, JapanbDepartment of Chemistry, Joetsu University of Education, Joetsu, Niigata 943, JapanYields of pyrolysis products and pore-size distribution of amorphous carbon produced from organic chemical modifiers,such as ascorbic acid, glucose and sucrose, for electrothermal atomization atomic absorption spectrometry were examined:the pyrolysis yield (for which ascorbic acid > glucose >sucrose) and the pore-size distribution are independent ofthe modifier used.Organic compounds have been used as chemical modiersfor elements such as lead,1¡Ó6 tin,6,7 antimony,8 selenium,8indium,9 gallium10 and gold11¡Ó14 in graphite furnace atomicabsorption spectrometry (GFAAS).The eectiveness oforganic compounds has been discussed from viewpoints ofthe formation of active carbon species and reductive gases.In previous work pyrolysis processes have been reported for(i) gaseous compounds (hydrocarbons, CO and CO2) below580 K; (ii) active carbon species such as soot between 600and 1100 K; and (iii) thermally stable carbon speciesbetween 1200 and 2400 K.15 The thermally stable carbonspecies was assigned to amorphous carbon by Ramanspectrometry.15 Recently, it was suggested that the eective-ness of an organic chemical modier for indium is due tothe proportion of the surface area coated by the amorphouscarbon and absorption into the micro-sized pores in theamorphous carbon.9 When discussing the degree of theeectiveness of organic chemical modiers, it is useful toexamine the pyrolysis yield and the pore-size distribution ofthe amorphous carbon. In the present work the pyrolysisyield and pore-size distribution for ascorbic acid, glucoseand sucrose are reported and the eectiveness of ascorbicacid and sucrose on GFAAS for indium and gallium isdiscussed.ExperimentalA Hitachi model Z-8000 ame and graphite furnace atomicabsorption spectrometer equipped with a Zeeman eect backgroundcorrector, an optical temperature controller system (Hitachi model180¡Ó0341), an automatic sampler and an automatic data processorwas used.The analytical wavelength and spectral bandwidth were325.6nm and 1.3nm for indium and 294.3nm and 0.4nm for gal-lium, respectively.Temperature data were calibrated using a Chinomodel IR-AH1 S radiation thermometer. The thermometer was cali-brated with a Pt¡ÓRh thermocouple. The standard atomizer con-ditions are given in Table 1.Raman spectra were measured at room temperature by means ofa Jobin-Yvon Ramanor T64000 based on a triple 0.64m focallength monochromator equipped with three 1800-grooves/mmgratings and a 1024256 element CCD detector; a triple subtrac-tive conguration and 3.5 cm£¾1 spectral bandwidth were used.Formacroscopic measurements, the 514.5nm line of an argon ion laserwith a low power of 20 mW at the sample and 180 8 scattering wasused to avoid thermal decomposition. The wavenumbers of theobserved Raman spectra were calibrated using the argon plasmalines (514.5 nm).Specic surface area and absorption pore-size distribution ofamorphous carbon were obtained using a Shimadzu modelASAP-2000 with N2 adsorption gas by BET and BJH methods,respectively.Aliquots of a commercially available standard solution werediluted with 0.1 mol dm£¾3 nitric acid before use.Distilled anddeionized water was puried with a Milli-Q Plus system.Results and DiscussionA pyrolytic graphite-coated (PG) furnace was heated untila constant weight as measured by an analytical balance wasreached. The organic matrix modier (2 mg: 40 ml of 50g l£¾1)was pyrolysed with the furnace in the atomizer unitaccording to the standard atomizer conditions except for theatomization and cleaning stages (Table 1) and this processwas repeated three times (6.0 mg of modier pyrolysed).Then, the furnace was removed and weighed.A pyrolysisyield (%) was obtained from the equation [weight changein mg]/6.0 (mg)100. The detectable low limit and theuncertainty of yield were 2% for yields of 6.0 mg (0.1 mgof mass) and 2%, respectively. The yields at pyrolysistemperatures of 640 and 1230K are shown in Table 2 withthe standard deviation (n= 5).At 640 K, the yield increasesin order sucrose <glucose <ascorbic acid. The weight lossof the compounds is attributed to a release of gaseousspecies, such as hydrocarbons, water and carbon monoxide.When the pyrolysis temperature was increased to 1230 K,the yield by weight decreased. Since active carbon species,such as soot, vaporize over the temperature range 970¡Ó1100 K,11,15 the yield is attributed to that of amorphouscarbon and the decrease in yield is attributed to the releaseof active carbon species.The pyrolysis yield for ascorbicJ. Chem. Research (S),1998, 218¡Ó219$Table 1 Standard atomization conditionsStageDry Pyrolysis Atomizationb CleaningTemp.a (T/8C) 120 varying 2800 2900Ramp time (t/s) 30 20 0 0Hold time (t/s) 0 10 3 3Inner gas flow(ml m£¾1)200 200 30 200aProgrammed for the atomizer unit. bAn optical temperaturecontroller was used.Table 2 Pyrolysis yield of 6.0mg of organic chemical modifierin a PG furnacePyrolysisPyrolysis yield (%) (n 5)temperature (T/K) Ascorbic acid Glucose Sucrose640 3223 722 2221230 2222 222 <2$This is a Short Paper as dened in the Instructions for Authors,Section 5.0 [see J.Chem. Research (S), 1998, Issue 1]; there is there-fore no corresponding material in J. Chem. Research (M).*To receive any correspondence (e-mail: imai@ias.tokushima-u.ac.jp).218 J. CHEM. RESEARCH (S), 1998acid is clearly more than approximately 10-fold that for glucose and sucrose.After pyrolysis of 1.0 mg (20 ml of 50g l¢§1) of the organic chemical modi¢çers at 1000 K, Raman spectra at the centre of the bottom of the sample compartment were observed through the sample injection hole of the furance with the bare PG furnace, as shown in Fig. 1. For the PG surface (line in Fig. 1), two Raman bands, a band corresponding to the E2 g mode near to 1584 cm¢§1 (G band) and a broad band for disorder mode with weak intensity of approxi- mately 1361 cm¢§1 (D band) were observed.16 After pyrolysis of the organic chemical modi¢çer, the intensity near the pos- itions of the G and D bands was increased with an increase in the intensity at the bottom between both bands.In the case of ascorbic acid the Raman shifts of the two broad bands were 1591 and 1381 cm¢§1, respectively, and that for the shoulder was 1430 cm¢§1. However, the broad bands can- not be assigned at the present time. For sucrose, the D band of the PG surface may form a sharp peak on the broad peak for the pyrolysis product.The intensity of the Raman band is due to the proportion of the surface area coated by the pyrolysis product relative to the area of the laser beam spot (100 mm diameter) at the centre of the bottom of the sample compartment. The order of the intensities, which is sucrose<glucose <ascorbic acid, is in agreement with that of the pyrolysis yield. The bulk amorphous carbon samples of ascorbic acid, glucose and sucrose were prepared by heating for 2 h at 1170K using a mu.e furnace after releasing smoke. A BET speci¢çc surface area of 698217, 683217 and 624215m2 g¢§1 (n =3) was observed for the amorphous carbon of ascorbic acid, glucose and sucrose, respectively. The pore size distribution at diameters over the range 2¡¾20 nm (meso- pores) is shown in Fig. 2. The adsorption average pore diameter was 2.4, 2.5 and 2.4nm for ascorbic acid, glucose and sucrose, respectively.Table 3 shows the e€ect of organic chemical modi¢çer additive on the integrated absorbance for indium and gallium, which are elements that exhibit a large loss of analyte in GFAAS particularly when using a PG furnace because of formation of volatile oxide at 1000 K,10,17 with a pyrolysis temperature of 900 K. The degree of sensitivity enhancement was greater for ascorbic acid than for sucrose. Although the sensitivity enhancement is due to the reduction by the pyrolysis products and the absorption onto the amorphous carbon,9 the surface area and pore-size distri- bution are similar.Thus, the superiority of ascorbic acid can be elucidated by the greater yield of pyrolysis product. It has been reported in our previous work that when a PG furnace treated by a modi¢çer at temperatures above 1230K is used for GFAAS of indium, the superior e€ectiveness of ascorbic acid is also observed (Fig. 4 in ref. 9). We gratefully acknowledge Ken Isobe (Kokan Keisoku Co.Ltd., Kawasaki, Japan) for his assistance in obtaining the surface area and pore-size distribution of amorphous carbon. Received, 11th August 1997; Accepted, 8th December 1997 Paper E/7/05858F References 1 J. G. T. Regan and J. Warren, Analyst, 1976, 101, 220. 2 J. W. McLaren and R. C. Wheeler, Analyst, 1977, 102, 542. 3 M. Tominaga and Y. Umezaki, Anal. Chim. Acta, 1982, 139, 279. 4 G. F. R. Gilchrist, C. L. Chakrabarti and J. P. Byrne, J. Anal. At. Spectrom., 1989, 4, 533. 5 S. Imai and Y. Hayashi, Anal. Chem., 1991, 63, 772. 6 A. B. Volynsky, S. V. Tikhomirov, V. G. Senin and A. N. Kashin, Anal. Chim. Acta, 1993, 284, 367. 7 M. Tominaga and Y. Umezaki, Anal. Chim. Acta, 1979, 110, 55. 8 M. T. Perez-Corona, M. B. La Calle-Guntinas, Y. Madrid and C. Camara, J. Anal. At. Spectrom., 1995, 10, 321. 9 S. Imai, N. Hasegawa, Y. Nishiyama, Y. Hayashi and K. Saito, J. Anal. At. Spectrom., 1996, 11, 601. 10 S. Imai, T. Ibe, T. Tanaka and Y. Hayashi, Anal. Sci., 1994, 10, 901. 11 S. Imai and Y. Hayashi, Bull. Chem. Soc. Jpn., 1992, 65, 871. 12 A. J. Aller, Anal. Chim. Acta, 1994, 292, 317. 13 S. Imai, K. Okuhara, T. Tanaka and Y. Hayashi, J. Anal. At. Spectrom., 1995, 10, 37. 14 N. Thomaidis, E. A. Piperaki and C. E. Efstathiou, J. Anal. At. Spectrom, 1995, 10, 221. 15 S. Imai, Y. Nishiyama, T. Tanaka and Y. Hayashi, J. Anal. At. Spectrom., 1995, 10, 439. 16 M. Yoshikawa, Material Sci. Forum, 1989, 52/53, 365. 17 S. Imai, N. Hasegawa, Y. Hayashi and K. Saito, J. Anal. At. Spectrom., 1996, 11, 515. Fig. 1 Raman spectra of a surface of sample compartment of a PG furnace: 1, bare furnace; 2¡¾4, after pyrolysis of 1mg of organic matrix modi�¡er at 1000 K: 2, sucrose; 3, glucose; 4, ascorbic acid Fig. 2 Pore-size distribution of amorphous carbons pyrolysed at 1170 K: ., ascorbic acid;w, glucose, r, sucrose Table 3 Effect of organic chemical modifier on the integrated absorbance for 2 ng of indium and gallium Relative value of integrated absorbance Matrix modifier Indium Gallium Absent 1.00 1.00 10 g l¢§1 sucrose 4.28 3.36 10 g l¢§1 ascorbic acid 7.19 9.87 J. CHEM. RESEARCH (S), 1998 2
ISSN:0308-2342
DOI:10.1039/a705858f
出版商:RSC
年代:1998
数据来源: RSC
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