A diastereoselective radical cyclization approach to substituted quinuclidines

Abstract

A new, concise, and flexible approach to novel quinuclidines has been developed, which employs a phosphorus hydride mediated radical addition/cyclization reaction in the key step. 1,7-Diene 5 reacts with diethyl thiophosphite in an efficient and diastereoselective radical addition/cyclization reaction to give trisubstituted piperidines 4ab. Piperidines 4ab are subsequently converted into 2,5-disubstituted quinuclidines using SN2-type cyclizations. Finally, the resulting quinuclidines are shown to undergo novel HornerWadsworthEmmons-type (HWE-type) reactions to give unsaturated quinuclidines 21a and 21b, which have structures similar to that of ()-quinine 1.

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