Palladium-catalyzed Asymmetric [3+2]cycloadditions Of Vinylcyclopropanes And In Situ Formed α,β-unsaturated Imines

Indole derivatives especially the spirocyclopentane-1,3′-indolenines are an very important part of numerous natural products and drug molecules. Thus, enormous effort has been devoted to the development of rapid and efficient synthetic procedures for the highly functionalized and optically enriched indole derivatives. The cyclopropane derivatives are another very significant intermediates in organic synthesis, especially in the synthesis of five or six-membered ring compounds. Vinyl cyclopropanes can transform to zwitter ionic complex in the presence of lewis acid or transition metal, and the zwitter ionic complex are reactive in the cycloaddition reaction with dipolarophiles such as olefins, imines and aldehydes. In this paper, we have developed a palladium-catalyzed asymmetric [3+2] cycloaddition of vinyl cyclopropanes and in situ formed α,β-unsaturated imines from aryl sulfonyl indoles.The reaction proceeds with high diastereoselectivity to provide the optically enriched spirocyclopentane-1,3′-indolenines in up to 74% yield and with up to 97% ee, which include an all-carbon quaternary center and two tertiary stereocenters, and further selective hydrolysis can get four consecutive chiral center. All of the compounds were identified by1 H NMR,13 C NMR, HRMS and the absolute configuration of the compounds were assigned by X-ray crystal analysis.