Selektive Addition von gasf�rmigem Chlorwasserstoff an kristalline Epoxide und Steroid-Epoxide
摘要:
Solid epoxides add gaseous HCl or HBr regioselectively and without melting, if the melting points are sufficiently high. Such additions proceed diastereoselectively with chiral epoxides. These gas/solid reactions are compared to similar transformations in solution. One observes interesting reaction sequences in the conversions of steroidal epoxides. Thus, the opening of the epoxide ring may be followed by cationic rearrangements, or it occurs elimination of water, if it creates conjugation to a carbonyl group.
Highly efficient Lewis acid catalyzed, one step conversions of 16α,17α-epoxy-3β-hydroxypregn-5-en-20-one to d-homosteroid and Δ13-steroids
作者:Navdeep K Girdhar、M.P.S Ishar、Rajiv Kumar、Rajinder Singh、Gurmit Singh
DOI:10.1016/s0040-4020(01)00673-1
日期:2001.8
Conversion of 16 alpha ,17 alpha -epoxy-3 beta -hydroxypregn-5-en-20-one (1a) to 16 beta -chloro-3 beta ,17 alpha -dihydroxy-17 beta -methyl-17a-homoandrost-5-en-17a-one (3) in very high yields (95%), in one step by treatment with 3 equiv. of anhyd. AlCl3, has been achieved; use of two equiv. of AlCl3 affords mixture Of D-homosteroid 3 (70%) and chlorohydrin 4 (27%). On the other hand, treatment of la with excess of acetic anhydride and anhydrous ZnCl2 at room temperature leads to reversal of the direction of epoxide ring opening with concomitant methyl migration, leading to 3 beta ,16 alpha -diacetoxy-17-methyl-17 alpha -pregna-5,13-diene-20-one (6) in high yield (92%). The conversions are a remarkable improvement over related routes in terms of both yield and selectivity. (C) 2001 Elsevier Science Ltd. All rights reserved.
Schwarz,V.; Syhora,K., Collection of Czechoslovak Chemical Communications, 1963, vol. 28, p. 637 - 643
作者:Schwarz,V.、Syhora,K.
DOI:——
日期:——
Synthesis of novel 1,2,3-triazolyl derivatives of pregnane, androstane and<scp>d</scp>-homoandrostane. Tandem “click” reaction/Cu-catalyzed<scp>d</scp>-homo rearrangement
作者:Yury N. Kotovshchikov、Gennadij V. Latyshev、Nikolay V. Lukashev、Irina P. Beletskaya
DOI:10.1039/c4ob00404c
日期:——
Copper-catalyzed 1,3-dipolar cycloaddition has been employed in the reaction of steroidal azides with various terminal alkynes. A number of novel 1,2,3-triazolyl derivatives of pregnane, androstane and D-homoandrostane were obtained in high yield (70–98%). The developed synthetic protocols allowed us to attach the triazolyl moiety to both the side chain and the steroidal backbone directly, despite
Selektive Addition von gasf�rmigem Chlorwasserstoff an kristalline Epoxide und Steroid-Epoxide
作者:Gerd Kaupp、Anke Ulrich、Gerhard Sauer
DOI:10.1002/prac.19923340503
日期:——
Solid epoxides add gaseous HCl or HBr regioselectively and without melting, if the melting points are sufficiently high. Such additions proceed diastereoselectively with chiral epoxides. These gas/solid reactions are compared to similar transformations in solution. One observes interesting reaction sequences in the conversions of steroidal epoxides. Thus, the opening of the epoxide ring may be followed by cationic rearrangements, or it occurs elimination of water, if it creates conjugation to a carbonyl group.