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In this Letter, we describe the synthesis of new donor-acceptor substituted cyclopropanes bearing various imido groups and their use in [3+2]-annulation reactions. A sequence of palladiumcatalyzed vinylation and rhodium-catalyzed cyclopropanation gave access to the required cyclopropanes in only two steps and high overall yields. The obtained compounds were used successfully in the tin-catalyzed [3+2] annulation with enol ethers to give cyclopentylamine derivatives in 22-95% yield. [ABSTRACT FROM AUTHOR]

The regioselective and diastereoselective cyclization of acyliminium intermediates generated from aminocyclopropanes on unprotected indoles is presented. The recent results obtained in our group are compared with previous intermolecular reactions with aminocyclopropanes as well as with other cyclization methods involving iminium ions and unprotected indoles. A first speculative analysis of possible reaction mechanisms allows rationalizing the observed selectivity. The high potential of the method for the synthesis of natural alkaloids is demonstrated in the formal synthesis of aspidospermidine and the total synthesis of goniomitine. [ABSTRACT FROM AUTHOR]