Alkoxycyclization

A transition state similar to TS 34 – 33 has been proposed in the reaction of cyclopropyl gold(I) carbenes generated by retro-Buchner reaction of 7-cyclopropyl 1,3,5-cycloheptatrienes. 79 Gold(I) complexes are able to catalyze the addition of amines, alcohols, or water to 1, n -enynes affording products of amino-, alkoxy-, or hydroxycyclization under much milder conditions than other metal catalysts. 26, 32, 33, 62, 80 − 82 These additions are stereospecific, as illustrated by the alkoxycyclization of diastereomeric enynes 1m and 1h, and proceed via opening of cyclopropyl gold(I) carbene intermediates 35 by attack of the nucleophile to the cyclopropane ring (Scheme 11 ).