Evidence for concerted processes in the course of the homoallenylic transposition
Abstract
The hydrolysis of beta-allenic tosylates produces mainly 2-methylenecyclobutanols resulting from a homoallenylic participation along with isomeric 2-methylenecyclobutanol minor products coming from a 1234-1243 rearrangement. Structures of various cyclopropylvinyl carbocations involved in the course of the hydrolysis have been determined by computational studies. For acyclic tosylates, the hydrolysis of one beta-deuterated allenic tosylate confirmed the nucleophilic attack on the corresponding nonclassical carbonium ion before its evolution to a more stable cyclopropylvinyl carbocation. In the case of one cyclic beta-allenic tosylate, the structure of the products has been checked by the use of deuterated isotopomer. (C) 2013 Published by Elsevier Ltd.