Highly efficient C-C bond-forming reactions of an α-cyanoketene dithioacetal with aldehydes and ketones

In the presence of titanium(IV) chloride, the C-C bond-forming reaction of the α-cyanoketene cyclic dithioacetal 1,3-dithiolan-2-ylideneacetonitrile with various aldehydes and ketones afforded multifunctional pentanedinitriles, 3-substituted- or 3,3-disubstituted 2,4-di-1,3-dithiolan-2-ylidenepentanedinitriles, respectively, in good to excellent yields under very mild conditions. A possible mechanism involving consecutive C-C bond formation was proposed.