Tandem Radical Cyclizations: a One-Step Synthesis of Stereoisomeric Tricyclo[6.3.0.0^2,6]undecanes From Acyclic Precursors

Abstract

Radical cyclization of (1E,5Z)-1-iodoundeca-1,5,10-triene with triphenyltin hydride provides one acyclic, one monocyclic, two bicyclic and four tricyclic products. At low concentration (0.002 M), the title tricycloundecane products resulting from triple cyclization predominate, but the stereoselectivity is low. Cyclization of (1E,5Z)-1-iodo-8,8-bis( phenylsulfonyl )undeca-1,5,10-triene followed by reductive desulfonylation provides a similar ratio of products to the parent. The results show that this class of triple cyclization occurs well, but the level of stereoselectivity must be raised for it to become synthetically useful.