diastereoselective radical 1,5 phenylmigration reactions fromsilicon in diarylsilyl ethers to various C-centered radicals to form the corresponding 3-phenylated alcohols are described. Functionalized aryl groups can also be transferred. The effect of the variation of the attacking radical on the aryl transfer reaction is discussed. Best results are obtained for the phenylmigration to nucleophilic secondary
New triazole antifungal agents having C6S7 or S6C7 bridges are disclosed. These triazoles provide alternatives to existing antifungals in terms of formulation, bioavailability and activity.
Tetraphenylstibonium methoxide (1) is an effective reagent for the synthesis of oxiranes and oxetanes from the corresponding 1,2- and 1,3-halohydrins, respectively. As the reaction conditions are neutral, oxiranes bearing an ester moiety were obtained intact without undergoing solvolysis. In addition, oxetanes, whose preparation was not generally facile, were formed in good yields under mild conditions (60-80°C).
4-fluoro-3- methylpentanoates () which were converted to their carbanions. Treatment with bromine gave esters , and iodine gave alkyl 4-fluoro-2-iodo- 3-methylpentanoates (). Esters and were converted to alkyl 2-azido-4-fluoro-3-methylpentanoates () whose hydrogenation gave alkyl 2-amino-4-fluoro-3-methylpentanoates (). Hydrolysis afforded γ-fluoroisoleucine ().
Heterogeneous asymmetric ring-opening reactions of prochiral epoxides included as guest molecules in tri-o-thymotide clathrates.
作者:Raymond Gerdil、Giacomo Barchietto
DOI:10.1016/s0040-4039(00)96597-3
日期:1987.1
Enantiomorphous tri-o-thymotideclathrates of prochiral oxiranes were submitted to the action of gaseous hydrogen halides. Ring-opening reactions ensued that differ from those reported in homogeneous phase, showing a considerable modification of the chemical reactivity of the external reagent in the host lattice. Chirality transfer from the host receptors to the guest products was also observed, but