PREPARATION OF 1-SUBSTITUTED BICYCLO[2.2.1]HEPTANES BY ANIONIC CYCLIZATION OF A 5-HEXEN-1-YLLITHIUM

The facile regiospecific isomerization of a 5-hexen-l-yllithium to a (cyclopentyl)methyllithium at room tem-perature1provides a convenient route to functionalized cyclopentylmethyl-containing products.2-4As shown below, the precursor olefinic alkyllithiums may be easily prepared in high yield by low-temperature lithium-iodine exchange between an olefinic alkyl iodide and tert-bu-tyllithium (t-BuLi)5,6and the organometallic formed upon 5-exo-trig cyclization may be functionalized by reaction with any of a variety of electrophiles. Herein we report that this methodology may be used to advantage for the preparation of 1-substituted bicyclo[2.2.1]heptanes via cyclization of the olefinic alkyllithium derived from readily available 3-(2-iodoethyl)-l-methylenecyclopentane (1). The two-step, one-pot synthetic sequence is summarized in Scheme I. © 1990, American Chemical Society. All rights reserved.