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。
Controllable Isomerization of Alkenes by Dual Visible‐Light‐Cobalt Catalysis
作者:Qing‐Yuan Meng、Tobias E. Schirmer、Kousuke Katou、Burkhard König
DOI:10.1002/anie.201900849
日期:2019.4.16
We report herein that thermodynamic and kineticisomerization of alkenes can be accomplished by the combination of visible light with Co catalysis. Utilizing Xantphos as the ligand, the most stable isomers are obtained, while isomerizing terminal alkenes over one position can be selectively controlled by using DPEphos as the ligand. The presence of the donor–acceptor dye 4CzIPN accelerates the reaction
BF3·OEt2 promotes fast, mild, clean and regioselective dehydration of tertiary alcohols
作者:Gary H. Posner、Ellen M. Shulman-Roskes、Chang Ho Oh、Jean-Christophe Carry、Julianne V. Green、A.Brian Clark、Haiyan Dai、Tizah E.N. Anjeh
DOI:10.1016/0040-4039(91)80200-p
日期:1991.11
BF3.OEt2 in methylene chloride at 25-degrees-C for 2 hours or less is shown to be effective for easy conversion of tertiary alcohols into the corresponding thermodynamically most stable alkenes.