enones present as s-trans conformers to provide good yields of the silyl enol ethers of beta-acetylido carbonyl compounds. Typically good substrates are 2-cyclopentenone, 2-cyclohexenone, alpha,beta-unsaturatedaldehydes, and beta-alkoxy-alpha-enones. Copper acetylide reagents prepared from CuI and an alkynyllithium give considerably higher yields than those prepared from CuBr or CuCN. Iodotrimethylsilane
Diastereoselective approach to 11-aryl steroid skeletons through a cobalt(I)-mediated [2+2+2] cyclization of allenediynes
作者:Marc Petit、Corinne Aubert、Max Malacria
DOI:10.1016/j.tet.2006.05.091
日期:2006.11
The cobalt(I)-mediated [2+2+2] cycloaddition reactions of allenediynes of yne-allene-yne type bearing an aryl group on the allene are described. The cyclizations are totally chemo- and regioselective and show low diastereoselectivities. η4-Complexed tricyclic (6,6,6) compounds were obtained in good yields as mixtures of endo/exo diastereomers. The cyclization is also compatible with an oxyfunctionality