Phosphite-mediated annulation: an efficient protocol for the synthesis of multi-substituted cyclopropanes and aziridines

In the presence of phosphite or phosphine, the reaction between 4-, 2-nitrobenzaldehyde and methylidenemalononitriles proceeded smoothly to give the cyclopropane derivatives in high yields, while the reaction between 4-, 2-benzaldehyde, and N-tosylbenzaldimines afforded the azidridine derivatives in moderate to high yields. A plausible mechanism was proposed and the strongly electron-withdrawing nitro-group is believed to play a critical role in these transformations. (C) 2009 Elsevier Ltd. All rights reserved.