摘要:

Early developments in solid phase organic synthesis are traced. Particular emphasis is placed on the use of cross-linked polystyrene in the first general method of monoblocking symmetrical difunctional compounds. The monoprotected polymer-bound symmetrical starting materials were then used in multi-step syntheses of a variety of compounds, particularly insect pheromones. Asymmetric synthesis on polymer supports was demonstrated. Diels-Alder and 1,3-dipolar additions on polymer supports proceeded readily as did macrocyclic formation of porphyrins and phthalocyanines. All of these reactions clearly showed that most organic chemical reactions could be performed on solid phases and laid the basis for the development of combinatorial chemistry. The first unsymmetrical phthalocyanine was prepared using the solid phase method and this led eventually to solution phase methods of preparing bi-, tri-, tetra-, and even a dendritic-like pentanuclear phthalocyanine.Key Words: solid phase organic synthesis (SPOS), phthalocyanines.

ISSN:0008-4042    

DOI:10.1139/v00-007

出版商:NRC Research Press    

年代:2000

数据来源: NRC

摘要:

Experimental solubilities are reported at 25.0°C for diuron (also called 3-(3,4-dichlorophenyl)-1,1-dimethyl urea) dissolved in 49 different organic nonelectrolyte solvents containing ether-, chloro-, hydroxy-, ester-, methyl-, andtert-butyl-functional groups. Results of these measurements are used to test the applications and limitations of expressions derived from Mobile Order theory. For the 28 nonalcoholic solvents for which predictions could be made computations show that Mobile Order theory does provide fairly reasonable estimates of the saturation mole fraction solubilities. Average absolute deviation between predicted and observed values is 60.1%. Diuron solubilities in the alcohol solvents are used to calculate stability constants for presumed solute-solvent hydrogen bonds that are believed to occur in solution.Key words: pesticide, diuron solubilities, organic nonelectrolyte solvents, solubility predictions

ISSN:0008-4042    

DOI:10.1139/v99-243

出版商:NRC Research Press    

年代:2000

数据来源: NRC

摘要:

The solvent dependent study of absorption, fluorescence, and fluorescence excitation spectra of 2-(2'-hydroxyphenyl)-1H-naphth-[2,3-d]-imidazole (HPNI) have indicated the presence of different rotamers and tautomers in theSoandS1states. Similarity of the absorption and fluorescence spectra of HPNI in protic solvents with those of 2-(2'-methoxyphenyl)-1H-naphth-[2,3-d]-imidazole (MPNI) suggests that the normal emission is observed from the rotamers2and4, whereas the tautomer emission is observed from the tautomer3, formed by the excited state intramolecular proton transfer (ESIPT) in the rotamer1(Scheme 1). Ground state geometries of rotamers1,2, and the tautomer3were optimized using AM1 method. The results show that the rotamer2is the most stable and its stability further increases in polar and protic solvents due to the dipolar solvation interaction. The increase in the fluorescence quantum yield of the normal band when methanol or water is added to dioxane is due to: (i) the formation of rotamer4, where ESIPT is not possible and (ii) the decrease in the rate of non-radiative decay process. Very large red shifted fluorescence bands of the monocations of HPNI and MPNI in different solvents have been assigned to the charge transfer band.Key words: 2-(2'-hydroxyphenyl)-1H-naphth-[2,3-d]-imidazole, ESIPT, prototropic reactions, fluorescence, 2-(2'-methoxyphenyl)-1H-naphth-[2,3-d]-imidazole.

ISSN:0008-4042    

DOI:10.1139/v99-244

出版商:NRC Research Press    

年代:2000

数据来源: NRC

摘要:

The structures of 30 neutral and positively charged small clusters were optimized and a number of hypothetical reaction pathways were investigated to compare the performance of the B3LYP/CEP-121G(d) Effective Core Potential/triple-split basis set method (ECP, method 1) and the B3LYP/6-311G(d) approach (method 2) for geometry optimizations. In addition, single point calculations at the B3LYP/CEP-121+G(d,p) (on geometries optimized by method 1) and at the B3LYP/6-311+G(d,p) (on optimized structures from methods 1 and 2) levels were also carried out. The augmented CEP-121G scheme is roughly 1.4 to 2.0 times computationally cheaper than full electron calculations, and is able to reproduce structures, infrared frequencies, thermochemical parameters and dipole moments predicted by the all-electron basis set employed in this study. From a practical viewpoint, the results confirm that ECPs can be used in combination with density functional methods, despite the fact that the former are typically generated via a Hartree-Fock approach.Key words: CEP, Effective Core Potentials, alkoxides, DFT, Ti.

ISSN:0008-4042    

DOI:10.1139/v99-225

出版商:NRC Research Press    

年代:2000

数据来源: NRC

摘要:

(-)-Scopolamine hydrochloride anhydrate gives crystals belonging to the orthorhombic space groupP212121and at 293(2) K:a= 7.097(2),b= 10.686(2),c= 22.623(2) Å,V= 1715.7(6) Å3,Z= 4,R(F)= 0.039, andRw(F)= 0.053. (-)-Scopolamine hydrochloride 1.66hydrate yields crystals belonging to the tetragonal space groupP43212 and at 293(2) K:a=b= 11.843(6),c= 26.211(4) Å,V= 3676(3) Å3,Z= 8,R(F)= 0.047, andRw(F2)= 0.135. (-)-Scopolamine methobromide affords crystals belonging to the orthorhombic space groupP212121and at 293(2) K:a= 7.0403(8),b= 10.926(2),c= 23.364(5) Å,V= 1797.2(6) Å3,Z= 4,R(F)= 0.039, andRw(F)= 0.052. The two hydrochloride pseudopolymorphs were isostructural to the corresponding two hydrobromide analogues. Both hydrohalide hydrated crystals have a water molecule occupying a general position of symmetry, and another water molecule occupying a special position ofC2-rotation symmetry. The hydrated hydrochloride salt also had an additional 0.322(17) partial occupancy water molecule (absent in the hydrobromide sesquihydrate) occupying another special position ofC2-rotation symmetry, i.e., the extra water molecule occupied the special position in statistically ca. one-third of the unit-cells to give a total hydrate stoichiometry of 1.66 molecules of water. While the two hydrohalide anhydrates exhibited extended tropate ester conformations (phenyl-ring antiperiplanar to oxirane moiety) vs. compact conformations (phenyl-ring near the scopine underside) for the two hydrated hydrohalides, all four displayed other common structural features: axialN-methyl stereochemistry, antiperiplanar methylol oxygen/aromatic C(ipso) relationships, and phenyl-ring eclipsing of the C(alpha)-H bond. The CPMAS13C NMR spectrum of (-)-scopolamine hydrobromide "trihydrate" shows it to be a conglomerate of (-)-scopolamine hydrobromide sesquihydrate plus two or more hydrated species (three ca. equal intensity carbonyl signals at 5.0 kHz spin-rate). High-speed rotor spinning (e.g., ca. 10 kHz and higher) causes a temperature-induced phase-transition to yield only the sesquihydrate form. The same transformation was noted with a 18 K rotor-temperature increase and an invariant 5.0 kHz spin-rate. The sesquihydrate spectrum remained after spin-rate decrease to 5.0 kHz, but the three component mixture 5.0 kHz spectrum was regenerated after three weeks sample storage within the capped rotor. The (-)-scopolamine free base crystalline melt CPMAS spectrum also shows a mixture of at least three hydrated species.Key words: stereochemistry, X-ray crystallography, solid-state NMR, CPMAS, anticholin

ISSN:0008-4042    

DOI:10.1139/v00-005

出版商:NRC Research Press    

年代:2000

数据来源: NRC

摘要:

The results of ab initio calculations with the 6-31G basis sets on azulene and its derivatives (including azulenequinones and diazoazulenequinones) are presented in accordance with considerations of their structures and bonding. Azulene is a non-alternant compound with ten &pgr; electrons and has either aCsorC2vsymmetry depending on the different carbon bonding. The semiempirical and HF ab initio calculations converge to aCssymmetry and the DFT and MP2 calculations converge to aC2vsymmetry as a ground state structure of azulene. The CIS calculations describe the excited state of azulene and the first excitation energy (S0-S1) is 533 nm (CIS/6-31+G*), which could illustrate the azure color of azulene. According to the geometry analysis, there are 16 geometrical isomers in azulenequinone conjugated diketones of azulene. Ab initio calculation with the 6-31G basis set generates 1,5- and 1,7-azulenequinone being the most stable isomers of azulenequinone. Theoretically, the relative stability of the bromination product of azulenequinones indicates that 7-bromo-1,5-azulenequinone and 3-bromo-1,7- azulenequinone (for monobromoazulenequinones) and 3,7-dibromo-1,5- azulenequinone and 3,5-dibromo-1,7-azulenequinone (for dibromoazulenequinones) are more stable isomers. The product of diazotization of amino- bromoazulenes is diazoazulenequinone in which a diazo group replaces a ketone group. Isomeric 1,8- and 1,2-diazoazulenequinones are the most stable isomers of diazoazulenequinone according to the theoretical consideration. Due to the resonance and relative stability, diazoazulenequinone may easily extrude nitrogen and form the corresponding triplet ketocarbene intermediate and electronic isomers that undergo photoreaction with THF leading to a polyether bridged azulene (crown type ether). The cyclic reactions in diazoazulenequinone are also studied.Key words: azulene, azulenequinone, diazoazulenequinone, ab initio.

ISSN:0008-4042    

DOI:10.1139/v99-241

出版商:NRC Research Press    

年代:2000

数据来源: NRC

摘要:

Binding constants of &bgr;-cyclodextrin with six hydroxyphenyl alkyl ketones having a general structure Z-Ph-CO-(CH2)nCH3(Z =o-OH orp-OH andn= 0, 1, or 3) were measured at 25°C by UV-vis spectrophotometry. In all cases the formation of 1:1 host-guest complexes was established. NMR chemically induced shifts indicated mixed complexation modes. Equilibrium constants are around 200 M-1for some of the compounds and for the others around 1000 M-1. It is suggested that complexes with different geometries coexist in the solution with predominance of those with the aryl group (KSCD200 M-1) or alkyl group (KSCD1000 M-1) inside the cavity.Key words: inclusion complex, &bgr;-cyclodextrin, hydroxyphenyl alkyl ketones, association constants, UV-vis spectrophotometry

ISSN:0008-4042    

DOI:10.1139/v00-002

出版商:NRC Research Press    

年代:2000

数据来源: NRC

摘要:

The acylation of 8-methyl- (1b) and 8-methoxy[2.2]metaparacyclophane1cwith 1.1 equiv. of acetyl chloride in CS2solution in the presence of aluminum chloride afforded 15-acetyl-8-methyl- (2b) and 12-acetyl-8-methoxy[2.2]metaparacyclophanes (3c) with 65 and 41% yields, respectively. The different orientations for the electrophilic substitution were observed to be dependant on the substituent at the 8 position. On the other hand, when the same reaction was carried out under the same reaction conditions with the corresponding 5-tert-butyl derivatives (11),ipso-acetylation at thetert-butyl group was observed along with acetylation on thepara-benzene ring. The substituent effect on the 8-position was also observed in the presentipso-acetylation. Theipso-acylation at thetert-butyl group of 5-tert-butyl-8-methoxy[2.2]metaparacyclophane (11c)is attributed to the highly activated character of the aryl ring and the increased stabilization of a sigma-complex intermediate arising from the dienone-type sigma-complex intermediate possible in the case of a internal methoxy substituent. However, the presentipso-acetylation has not been observed in mild reaction conditions such as acetyl chloride in the presence of TiCl4catalyst due to deactivation of the second aromatic ring by the introduced acetyl group on thepara-benzene ring. The mechanism of these novel reactions is also discussed.Key words: cyclophanes, electrophilic aromatic substitution, regioselectivity, through-space electronic interaction,ipso-acylation.

ISSN:0008-4042    

DOI:10.1139/v00-006

出版商:NRC Research Press    

年代:2000

数据来源: NRC

摘要:

Two novel compounds, celastroidine A (1) and B (2), were isolated from the roots ofHippocratea celastroidesK. Their structures were elucidated by spectroscopical and X-ray diffraction studies. Celastroidine A (1) (C50H74O5) was identified as a Diels-Alder adduct of a triterpene plus a diterpene and celastroidine B (2) as a beyerane, a type of dimer of two diterpene (C40H60O4). Both compounds could be formed in vivo by a Diels-Alder reaction. Celastroidine A showed some antifeeding activity against the stored grain insectSitophyllus zeamays.Key words:Hippocratea celastroides, Hippocrataceae, roots, Diels-Alder adducts, diterpenoids, triterpenoids, x-ray diffraction, insect antifeedants, stored grain insects,Sitophyllus zeamays, insecticidal plants, Diels-Alderase.

ISSN:0008-4042    

DOI:10.1139/v99-239

出版商:NRC Research Press    

年代:2000

数据来源: NRC

摘要:

A series of aminodiols RN(CH2CH2C(OH)Rprime2)2(R, Rprime = Me, Me4; Me, Ph5;tert-butyl, Me6;tert-Bu, Ph7; (S)-PhCH(Me), Me8) were prepared by the Michael addition of a primary amine to methyl acrylate followed by reaction of the resulting aminodiester with excess methyl or phenyl lithium. Reaction of two equivalents of the aminodiols4-8with tetrabenzylzirconium afforded the zirconium bis(aminodiolates)10-14in excellent yield. Complex11(R, Rprime = Me, Ph) adopts acis,fac-octahedral geometry in solution and in the solid state. Complexes10-14are fluxional in solution by NMR spectroscopy: small substituents at nitrogen and large substituents at the alkoxide carbons slow the rate of exchange. The chiral complex14functions as a Lewis acid catalyst in the nitroaldol (Henry) reaction and the oxidation of geraniol bytert-butyl hydroperoxide with modest enantioselectivities (30 and 46% enantiomeric excess (ee), respectively).Key words: diol, Michael addition, zirconium, synthesis, structure, fluxional, alkoxide, Lewis acid, catalysis.

ISSN:0008-4042    

DOI:10.1139/v00-001

出版商:NRC Research Press    

年代:2000

数据来源: NRC