A new type of chemical cascade reaction was found: the direct formation of cyclopropanes from carbonyl compounds and C–H acid. The action of free halogen or active halogen containing compounds on a mixture of 1equiv of carbonyl compound and 2equiv of malononitrile in a basic alcohol solution results in the formation of substituted 1, 1, 2, 2- tetracyanocyclopropanes in 15–80% yield. The latter are well-known precursors for the ...