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Mendeleev Communications Electronic Version, Issue 4, 1997 (pp. 127–168) A novel stereoselective and catalytic C–C coupling reaction: acetylene dimerization accompanied by addition of iodine to yield (E,E)-1,4-diiodobuta-1,3-diene in the PtIV–I––I2–MeOH system Sergey A. Mitchenko,*a Valentin P. Ananikov,b Irina P. Beletskayac and Yuri A. Ustynyukc a A. N. Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences, 117813 Moscow, Russian Federation. Fax: +7 095 135 5085; e-mail: mitchen@samit.donetsk.ua b N.D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences, 117913 Moscow, Russian Federation. Fax: +7 095 135 5328 c Department of Chemistry, M. V. Lomonosov Moscow State University, 119899 Moscow, Russian Federation. Fax: +7 095 932 8846 A new catalytic reaction – dimerization of acetylene accompanied by addition of iodine to yield (E,E)-1,4-diiodobuta-1,3-diene at 30 °C in a methanolic solution of NaI, PtIV and I2 – has been found; a plausible reaction mechanism involves intermediate formation of a cis-divinyl derivative of platinum(IV) through two subsequent triple bond iodoplatination steps followed by reductive elimination of the final product.Metal complex catalysis of acetylene hydrocarbon conversions usually involves1–2 an intermediate p-complex of alkyne and metal centre formation. Probably due to the inability of platinum(IV) to form a stable p-complex with alkynes,3 for a long time PtIV has been considered to be inert toward alkynes. Recently it has been shown4 that PtIV is a rather effective catalyst for acetylene hydroiodation in aqueous acidic (HI) solutions.This reaction involves intermediate platinum(IV) s-vinyl derivative formation through a triple bond iodoplatination step. Now we have found a new reaction of alkynes with PtIV complexes in the absence of acid but in the presence of iodine. In the case of acetylene the reaction proceeds under catalytic conditions giving (E,E)-1,4-diiodobuta-1,3-diene.Acetylene selectively and quantitatively converts into (E,E)-1,4-diiodobuta-1,3-diene at 30 °C in a methanolic solution of NaI (0.3–3.0 M), PtIV ([Na2PtCl6·6H2O] = 0.002– 0.02 M), and I2 (0.2 M):† The yield‡ of product based on consumed acetylene is close to 100%, and the highest value of the yield is about 5000% based on the catalyst involved.The E,E-diene configuration is in accordance with the AA'BB' pattern in the 1H NMR spectrum (Figure 1). An iteration procedure leads to the following parameters (Figure 2): † Synthesis of (E,E)-1,4-diiodobuta-1,3-diene. Anhydrous NaI (0.6 g) was dissolved in methanol (5 ml) and the solution was saturated with acetylene. Iodine (0.36 g) and Na2PtCl6·6H2O (27 mg, 0.048 mmol) were added to the resulting solution.The reaction proceeds at room temperature. After 6 h the product was precipitated by adding water to the solution. The precipitate was separated, washed out by water, then by a saturated aqueous solution of NaI, and after that repeatedly by water up to the absence of iodide ions in the washings. The product was extracted by methanol.The extract solution was evaporated at room temperature and the residue obtained was dried in vacuum. A white crystalline product was obtained (60 mg, 0.196 mmol). MS (EI), m/z: 306 (M+), 179 (CHI=CH–CH=CH+), 127 (I+). Found (%): C 16.2, H 1.5; calc. for C4H4I2 (%): C 15.69, H 1.31. ‡ The values of the product yield were determined by 1H NMR spectroscopy. The data obtained corresponds to an E,E-product configuration [cf. the spectrum5 of (E,E)-1,4-dichlorobuta-1,3-diene]. 13C{1H} (CD3OD): d = 145.5 (–CH=), 83.1 (–CI=). IR spectrum (cm–1, pellet with KBr): 3020 vw (nH–C=), 1620 m (nC=C), 1530 s, 1380 m, 1280 s, 1140 s, 1010 m, 960 vs (dH–C=). The last band is typical6 of conjugated trans-double bonds. It should be noted that reaction of the acetylene derivative propargyl alcohol with PtIV in an aqueous iodide solution at 5 °C leads to the formation of a bis(b-iodovinyl) PtIV derivative isolated as [Pt(CH=CI–CH2OH)2I2](CH3OH) 1.§ The NMR and IR data as well as elemental analysis confirm the structure proposed.The large value of J(Pt–C) = 801.4 Hz clearly § Synthesis of [Pt(CH=CI–CH2OH)2I2](CH3OH) 1. K2PtCl6 (0.2 g, 0.412 mmol) was suspended in 10 ml of an aqueous solution of KI (5 M) and stirred for 1 h.The precipitate of K2PtI6 was isolated and dissolved in 10 ml of H2O. To suppress the possible reduction of platinum(IV) iodide complexes8 a solution (0.15 ml) of I2 (1 M, 0.15 mmol) and NaI (5 M) was added to K2PtI6 dissolved in water. Propargyl alcohol (1.39 mmol) was added dropwise during 2 h to the resulting solution at 5 °C.After 6 h the precipitate formed was isolated, twice washed out by water, then twice by a 1 M aqueous solution of KI and finally repeatedly by water up to the absence of I– in the washings. Extraction by methanol of the washed precipitate gives after solvent evaporation a dark brown product (95 mg, yield based on PtIV is 28%). Found (%): C 9.8, H 1.4, Pt 23.0; calc.for C7H12O3I4Pt (%): C 9.92, H 1.42, Pt 23.02. 1H NMR (CD3OD): d 6.44 [triplet accompanied by 195Pt satellites, 2H, J(HH) = 2.0 Hz, J (PtH) = 31.1 Hz], 4.50 [doublet accompanied by 195Pt satellites, 4H, J(HH) = 2.0 Hz, J(PtH) = 2.5 Hz]; 13C{1H} NMR (CD3COCD3) d 100.9 [J(CPt) = 801.4 Hz, –CH=], 82.3 [J(CPt) = 24.4 Hz, –CI=], 72.6 [J(CPt) = 30.2 Hz, –CH2–]. IR (cm–1, pellet with KBr): 3030 vw (nH–C=), 2920, 2860 w (nCH2 ), 1630 m (nC=C), 1430 w (nH2C–C=), 1000, 940 m (dH–C=).HCºCH (E,E)-(ICH=CH)2 PtIV I–, I2/MeOH C=C I aH Hb C=C b'H Ha' I d(a) = 7.13 ppm d(b) = 6.82 ppm J(ab) = 14.39 Hz, J(ab') = –0.60 Hz J(aa') = 0.50 Hz, J(bb') = 10.19 Hz C=C I DOCH2 H C=C H CH2OD I C=C DOCH2 Hb C=C aH CH2 d OD I I Sol I I C H C I CH2OD Pt C H C I CH2OD Sol CD3COOD heat, –PtI2 slowly 1 2 3 Scheme 1 cMendeleev Communications Electronic Version, Issue 4, 1997 (pp. 127–168) indicates the presence of a metal–carbon s-bond. Decomposition of 1 leading to (E,E)-2,5-diiodohexa-2,4-dien-1,6-diol¶ 2 (Scheme 1) was monitored by 1H NMR spectroscopy. Complex 1 in CD3COOD solution almost completely decomposes into 2 and PtI2 during 3 h at 80 °C. Slow isomerization of the product 2 into the (Z,E)-2,5-diiodohexa- 2,4-dien-1,6-diol 3 takes place in CD3OD solution.An equilibrium mixture (1:1) of 2 and 3 is formed within 3 months at room temperature. Assignment of the NMR spectrum for compound 3 due to the intrinsic asymmetry of 3 can be easily made.†† The observed isomerization of 2 into 3 may be considered as independent evidence for the E,E-conformation of the product 2.The catalytic reaction mechanism can be rationalised within the framework of Scheme 2. By analogy with the above-mentioned reactions of propargyl alcohol we may assume that the catalytic transformation of acetylene proceeds through two subsequent acetylene triple bond iodoplatination reactions (steps a and b) leading to intermediate formation of a cis-divinyl derivative of platinum(IV).Decomposition of the latter organoplatinum compound through a reductive elimination route (step c) should give [cf. reaction (1), Scheme 1] the final product. The latter reaction can proceed due to oxidative assistance by iodine in the reductive elimination step (cf. ref. 7); in this case the platinum oxidation state does not change.If this oxidative assistance is not necessary for the reductive elimination flow, oxidation by iodine8 of platinum(II) which should be formed in the step c will regenerate the initial catalyst. Exploring the generality of this reactivity, particularly with respect to its implications for alkyne activation by PtIV, as well as elucidation of the reaction mechanism, are the subjects of ongoing studies in our laboratories. This work was supported, in part, by the International Soros Science Education Program (ISSEP) through grant no.GSU 053221. ¶ 1H NMR: d 7.16 (s, 2H), 4.41 (s, 4H); 13C{1H} (CD3OD): d 137.6 (–CH=), 109.8 (–CI=), 66.4 (–CH2–); IR (cm–1, pellet with KBr): 3210 vs (nO–H), 3050 vw (nH–C=), 2920, and 2840 m (nCH2), 1630 m and 1570 s (nC=C), 1430 s (nH2C–C=), 1370 s, 1300 m, and 1240 s (dCH2 ), 1040 vs (nC–O), 1010 vs, and 970 s (dH–C=).†† 1H NMR: d 7.06 [dt, 1H, J(HaHd) = 1.0 Hz, J(HaHb) = 10.4 Hz], 6.92 [dt, 1H, J(HbHc) = 1.5Hz, J(HbHa) = 10.4 Hz], 4.37 [d, 2H, J(HdHa) = 1.0 Hz], 4.25 [d, 2H, J(HcHb) = 1.5Hz]. References 1 J. P. Collman, L. S. Hegedus, J. R. Norton and R. G. Finke, Principles and Applications of Organotransition Metal Chemistry, University Science Books, Mill Valley, California, 1987, p. 859. 2 G. W. Parshall and S. D. Ittel, Homogeneous Catalysis. The Applications and Chemistry of Catalysis by Soluble Transition Metal Complexes, Wiley-Interscience, John Wiley & Sons, New York, Chichester–Brisbane–Toronto–Singapore, 1992, p. 199. 3 M. Herberhold, Metal p-Complexes. V.II. Complexes with Mono-Olefin Ligands.Part 1. General Survey, Elsevier, Amsterdam, London, New York, 1972. 4 S. A. Mitchenko, V. V. Zamashchikov and A. A. Shubin, Kinet. Katal., 1993, 34, 479 [Kinet. Catal. (Engl. Transl.), 1993, 34, 421]. 5 A. A. Bothner-By and D. Jung, J. Am. Chem. Soc., 1968, 90, 2342. 6 K. Nakanishi, Infrared Absorption Spectroscopy. Practical, Holden–Day, Inc., San-Francisco and Navikodo Co. Ltd., Tokyo, 1962. 7 Zhi-Qiang Wang, P. S. Humphies and P. M. Maitlis, Abstracts of the XIth FECHEM Conference on Organometallic Chemistry, Parma, Italy, 1995, p. 256. 8 S. A. Mitchenko, V. V. Zamashchikov, O. N. Pryadko, E. L. Kostenko and A. A. Shubin, Kinet. Katal., 1993, 34, 78 [Kinet. Catal. (Engl. Transl.), 1993, 34, 64]. C=C I H H C=C H H I C I I Sol C H I H Pt C H C I H Sol – I I I I Pt C H C I H Sol I2 HCºCH HCºCH a b c A B Scheme 2 PtI6 2– 7.20 7.12 7.04 6.96 6.88 6.80 6.72 Figure 1 Experimental 1H NMR spectrum of (E,E)-1,4-diiodobuta-1,3-diene; CD3OD, Bruker AM-300 (300 MHz). d/ppm Figure 2 Simulated (see the text) 1H NMR spectrum of (E,E)-1,4-diiodobuta- 1,3-diene. 7.2 7.1 7.0 6.9 6.8 d/ppm Received: Moscow, 12th November 1996 Cambridge, 20th January 1997; Com. 6/07748J

ISSN:0959-9436     

出版商:RSC    

年代:1997

数据来源: RSC