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

Despite the ease of obtaining aluminum carbenoids by the reaction of CH₂I₂ 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 by aluminum carbenoid are known, such as geraniol, perillyl alcohol, γ-silicon substituted allylic alcohols [5-7]. In order to develop a general method for the preparation of functionally-substituted cyclopropanes, in this paper we have studied the reaction of aluminum carbenoids with unsaturated amines. We found that the reaction of substituted allyl amines and enamines (allyldiethylamine, allyl piperidine, allyl tert-octyl amine, (E)-N,N-diethyl-1-penten-1-amine, (Z)-N,N-diethyl-2-phenyl-1-ethenamine) with two equivalents of Et₃Al and CH₂I₂ at room temperature in CH₂Cl₂ 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. 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. References [1] I. R. Ramazanov, L. K. Dil\'mukhametova, U. M. Dzhemilev, O. M. Nefedov, J. Organomet. Chem., 2010, 695, 1761-1767; [2] I. R. Ramazanov, A. V. Yaroslavova, U. M. Dzhemilev, O. M. Nefedov, Tetrahedron Lett., 2010, 51, 6268-6269; [3] I. R. Ramazanov, A. V. Yumagulova, U. M. Dzhemilev and O. M. Nefedov, Tetrahedron Lett., 2009, 50, 4233-4235;[4] I. R. Ramazanov, A. V. Yaroslavova, L. M. Khalilov, U. M. Dzhemilev, O. M. Nefedov, Russ. Chem. Bull., 2010, 59, 1668-1670; [5] К. Maruoka, Y. Fukutani, H. Yamamoto, J. Org. Chem., 1985, 50, 4412–4414; [6] A. B. Charette, A. Beauchemin , J. Organomet. Chem., 2001, 617-618, 702-708; [7] Y. Ukaji, K. Inomata, Chem. Lett., 1992, 2353-2356.