One-pot synthesis of multisubstituted spirocyclopropanes mediated by α-picoline

An efficient methodology was developed for the synthesis of multisubstituted spirocyclopropane derivatives. The reaction between isatin (acenaphthoquinone) and α-bromo(chloro)-acetophenone compounds afforded the corresponding spirocyclopropane products with high stereoselectivity via a one-pot tandem reaction in the presence of α-picoline and triethylamine. In addition, spirocyclopropanepyrazoles were obtained in good yields via a one-pot cascade reaction of α-bromo-acetophenone, pyrazolone and aromatic aldehydes. Diverse spirocyclopropane compounds were prepared through the multicomponent one-pot pathway. The high efficiency of this process and operational simplicity make it an attractive method for the synthesis of spirocyclopropanes.