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1.
James W. Pavlik Theppawut Israsena Na Ayudhaya Chennagiri R. Pandit Supawan Tantayanon 《Journal of heterocyclic chemistry》2004,41(1):61-67
Trifluromethyl substitution on the pyrazole ring was found to enhance photoreactivity via the P4 pathway which involves interchange of the N2‐C3 ring atoms. Thus, 1‐methyl‐3‐(trifluromethyl)pyrazole (1) and 1‐methyl‐5‐(trifluromethyl)pyrazole (3) transposed with a P4/P6 or P4/P6+P7 ratio of 2.1:1. 1‐methyl‐4‐(trifluromethyl)pyrazole (2) transposed regiospecifically by the P4 transposition pathway. Compounds 2 and 3 were also observed to undergo photocleavage to yield enaminonitrile and enaminoisocyanide products. 相似文献
2.
We give an overview of studies of models for semiflexible, equilibrium polymers with special emphasis on our work on both lattice and continuum models for such systems. We show, principally by Monte Carlo simulations, that, once monomers self assemble to form polymers, their semiflexibility leads to nematic phases at low temperatures. Attractive wall potentials encourage the adsorption of these equilibrium polymers on surfaces. Rapid cooling leads to the formation of glasses with entangled polymers. Shear promotes nematic ordering, but, at high shear rates, this tendency decreases since the equilibrium polymers are torn apart. A version of our model in which the polymers are directed shows the polymer analog of bosonic Mott-insulating, mass-density-wave, and supersolid phases. We give a brief comparison of our work with other studies and also explore the experimental implications of our study. 相似文献
3.
Conjugated esters and amides react with aryldiazonium salts at room temperature (MeCN) to form the corresponding iminium hydrazone derivatives, which can be thermally cyclized to cinnoline-3-esters and cinnoline-3-amides. In general the intermediate iminium salts derived from the enamine amides cyclize faster than those from the enamine esters. Furthermore, the ease of cyclization depends upon the structure of the base-component of the enamine ester or the amide and the substituent in the aryl moiety of the diazonium salt. The configurational structure of the iminium hydrazones, studied by NMR spectroscopy, has been shown to involve H-bonding of the hydrazonyl N-H with the ester or the amide CO group. 相似文献
4.
A series of monoacylated piperazine derivatives were obtained by the reaction of carboxylic acids with 2-chloro-4,6-dimethoxy-1,3,5-triazine in dichloromethane at room temperature. Good to excellent yields, short reaction times and mild reaction conditions are important features of this methodology. 相似文献
5.
A synthesis of deethyldesoxycamptothecin via the reaction of two readily accessible synthons is described. One of the synthons constitutes the ABC ring system of camptothecin, while the second provides all the C atoms of the rings D and E. The synthetic approach is suited for the total synthesis of camptothecin analogues. 相似文献
6.
7.
Carbenes3a-e add to the α-side of the first double bond of dienamine2 (title compound) to give 1 : 1 adducts4a-e, Chlorofluorocarbene3e gives, in addition, ketone7, corresponding to β-addition at the second double bond of2, and a 2 : 1 adduct8. The reaction of2 with dichlorocarbene3a yields, besides4a, novel ring-expansion products5 and6 corresponding to addition of two moles of3a. Ethoxycarbonylcarbene3f reacts with the dienamine (2) to give isomeric esters9 and10a,b. The structure assignments and the mechanism of formation of the reaction products are discussed. 相似文献
8.
Alkylation of 4-ethoxy-2-hydroxypyrimidines (10a, b), via their anions, provides a convenient procedure for preparing N1-substituted derivatives. Reaction of 10a, b with t-butyl 4-bromo-2-benzyloxycarbamidobutyrate (17) gives good yields of the N1-alkylated products 18a, b. The latter have been converted to uracil- (20a), thymine- (20b) and cytosine- (21) substituted -aminobutyric acids. 相似文献
9.
S. G. Yunusova S. D. Gusakova A. I. Glushenkova U. K. Nadzhimov Sh. Turabekov SA. Musaev 《Chemistry of Natural Compounds》1991,27(2):147-150
A comparative analysis has been made of the amounts of lipids and their fatty-acid compositions in the seeds of the lines of agenetic collection of cotton plants of the speciesGossypium hirsutum and their hybrids and the variety Tashkent-1. The results obtained on the fatty-acid compositions of some hybrids make it possible to recommend the use of individual lines of cotton plants as donors for improving the food-value indices of cottonseed oil.Institute of Chemsitry of Plant Substances, Academy of Sciences of the Uzbek SSR, Tashkent. V. I. Lenin Tashkent State University. Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 173–176, March–April, 1991. 相似文献
10.
The diastereomeric adducts of dichlorocarbene and dibromocarbene with (protected) uridine react with alcohols to give diazepine nucleosides (4a–c). The endo-chloro-exo-fluorocarbene adducts (1d and 2d) also react analogously to yield diazepine nucleoside 4d. On the other hand, the corresponding exo-chloro-endo-fluoro isomers (1e and 2e) are totally inert under the same reaction conditions. The adducts 1b and 2b yield, besides the ring-expanded product (4b), uridine-5-aldehyde (6a) in varying amounts which depend upon the conformation of the diastereomer. These results are explained on the basis of a possible role of the ring-oxygen of the ribose moiety. 相似文献