Aluminum Carbenoid R₂AlCH₂I – a New Cyclopropanation Agent for the Transformation of Unsaturated Amines into Cyclopropyl Amines

Abstract

The reaction of substituted allyl amines and enamines (allyldiethylamine, allyl piperidine, allyl tert-octyl amine, 1-cyclohexenylpiperidine, (Z)-1-styrylpiperidine) with two equivalents of Et 3 Al and CH 2 I 2 at room temperature in CH 2 Cl 2 results in the formation of corresponding cyclopropyl amines in high yields (71-87%). The reaction is complete in 3-18 hours depending on the amine structure. The transformation proceeds with retention of configuration of the substituents at the double bond in (Z)-1-styrylpiperidine. The paper demonstrates the advantage of using aluminum carbenoids over traditional cyclopropanation reagents (diazomethane, Simmons-Smith and Furukawa reagents) for the preparation of cyclopropyl amines. Introduction.Despite the ease of obtaining aluminum carbenoids by the reaction of CH 2 I 2 and trialkylaluminums, their chemistry has been little studied. Over the last few years the authors have developed a new approach to the synthesis of cyclopropane compounds based on the reaction of substituted alkynes and allenes with aluminum carbenoids [1,2]. Substituted propargyl alcohol and amines have been successfully involved in the reaction [3,4]. At the same time, only a few examples for the cyclopropanation of functionally-substituted alkenes