Preparation and determination of configuration of 3-halogeno-3-methyl-5α-cholestane epimers
作者:Marc van Robays、Roger Busson、Hubert Vanderhaeghe
DOI:10.1039/p19860000251
日期:——
3β-chloro-3α-methyl-5α-cholestane were prepared by reaction of hydrochloric acid with the two epimeric 3-hydroxy-3-methyl-5α-cholestanes. A better yield and cleaner conversion could be obtained with tetramethyl-1-chlorovinylamine as chlorinating agent. Reaction of the two 3-methyl-5α-cholestanols with triphenylphosphine–carbon tetrachloride or phosphorustrichloride oxide–pyridine gave mixtures of 3-methyl-5α-cholest-2-ene
通过使盐酸与两种差向异构的3-羟基-3-甲基-5α-胆甾烷反应,制得3α-氯-3β-甲基-和3β-氯-3α-甲基-5α-胆甾烷。用四甲基-1-氯乙烯基胺作为氯化剂,可以获得更好的收率和更清洁的转化率。两种3-甲基-5α-胆甾醇与三苯基膦-四氯化碳或三氯化磷-吡啶的反应生成了3-甲基-5α-胆甾-2-烯,3-甲基-5α-胆甾-3-烯和3-亚甲基-5α-胆甾烷。通过用(二乙基氨基)三氟化硫处理两个3-甲基-5α-胆甾烷-3-醇,获得了两个差向异构的3-氟-3-甲基-5α-胆甾烷。3-卤代-3-甲基-5α-胆甾烷的构型由它们的13个决定C nmr光谱。两种3-卤代-3-甲基-5α-胆甾烷差向异构体的可用性使800-400 cm -1区域的红外光谱得到了明确的解释。
Photoreduction des esters car☐yliques dans l'hexamethylphosphortriamide (HMPT)
作者:C. Portella、H. Deshayes、J.P. Pete、D. Scholler
DOI:10.1016/s0040-4020(01)88794-9
日期:1984.1
Use of HMPT as solvent in photochemistry allows efficient photoreductions. Alkyl esters and especially non absorbing alkyl acetates are photoreduced in excellent yields into alkanes. In the latter case, a protonating agent is necessary. Numerous examples illustrate the generality and convenience of the reaction. This photoreduction involves an electron transfer from HMPT to ester.