Comparative study of anionic and radical cyclization for the preparation of 1,3-dimethylindans: highly stereoselective preparation of cis-1,3-disubstituted indans via intramolecular carbolithiation.
[reaction: see text] The preparation of 1,3-dimethylindans from 4-(2-bromophenyl)-1-pentene (1) and 2-(2-iodo-1-methylethyl)styrene (2) substrates via radical-mediated cyclization and intramolecular carbolithiation has been investigated. Although cyclization of the radical derived from either substrate proceeds with modest selectivity for the cis-isomer, as does cycloisomerization of the aryllithium derived from substrate 1 (cis/trans approximately 2), intramolecular cyclization of the alkyllithium derived from substrate 2 is a highly cis-selective process (cis/trans = 12).
Bailey
William F
WF
Department of Chemistry, University of Connecticut, Storrs, Connecticut 06269-3060, USA. bailey@uconn.edu
Mealy
Michael J
MJ
Wiberg
Kenneth B
KB
D000838:Anions / Q000737:chemistry; D003500:Cyclization; D005609:Free Radicals / Q000737:chemistry; D007189:Indans / Q000138:chemical synthesis* / Q000737:chemistry; D008958:Models, Molecular; D013237:Stereoisomerism
D000838:Anions; D005609:Free Radicals; D007189:Indans