Allenes bearing a nucleophilic group cyclize on treatment with acyltetracarbonyl cobalt complexes in the presence of mild bases. Various nucleophilic groups and cobalt complexes can be used to give highly functionalized pyrrolidines, cyclopentanes and tetrahydrofurans. Disubstituted allenes may be used in the reaction. 1,3-disubstituted allenes give products with high stereoselectivity.
In order to synthesize the major C(3)-C(12) part of fostriecin, asymmetric dihydroxylation of several dienes 5a-f, prepared by cross-coupling reactions of several types. vas studied, thus providing high dependency on the hydroxyl groups at C(5) and C(l 1). The best regioselectivity was obtained with 5d to produce diol 23. which was later transformed into the advanced intermediate 26. (C) 2002 Elsevier Science Ltd. All rights reserved.
FUNCTIONALIZED CHAIN EXTENDED INITIATORS FOR ANIONIC POLYMERIZATION