Diastereocontrol by trialkylaluminums in the synthesis of tetrahydrofurans via radical cyclization.
[reaction: see text]. The influence of various Lewis acids in the radical cyclization of beta-allyloxyalkyl phenyl selenides was investigated. Whereas the unperturbed cyclization afforded trans-2,4-disubstituted tetrahydrofurans as the major products (cis/trans approximately 1/4.5), cyclization in the presence of trialkylaluminums (3 equiv) afforded predominantly (cis/trans approximately 7/1) the corresponding cis-isomers.
Ericsson
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Department of Organic Chemistry, Institute of Chemistry, Uppsala University, Box 531, S-751 21, Uppsala, Sweden.
Engman
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