The cyclization of an aryllithium tethered to a methylenecycloalkane, generated from 2-(o- bromobenzyl)-1-methylenecycloalkanes 1, 2, and 3 by low-temperature lithium-bromine exchange, has been found to be a kinetically slow but thermodynamically favorable process that proceeds at a convenient rate in an exclusively 5-exo fashion when solutions of the aryllithium in n-heptane-di-n-butyl ether (9: 1 v/v) are warmed to 45° C. The cyclization ...