From 1,2-difunctionalisation to cyanide-transfer cascades - Pd-catalysed cyanosulfenylation of internal (oligo)alkynes

Internal alkynes substituted by aliphatic or aromatic moieties or by heteroatoms were converted into sulphur-substituted acrylonitrile derivatives. Key is the use of Pd catalysis, which allows the addition of aromatic and aliphatic thiocyanates in an intra- and intermolecular manner. Substrates with several alkyne units underwent further carbopalladation steps after the initial thiopalladation step, thus generating in a cascade-like fashion an oligoene unit with sulphur at one terminus and the cyano group at the other. The intra- and intermolecular Pd-catalysed cyanosulfenylation of internal alkynes enables the formation of tetrasubstituted thioacrylonitriles and is extended to oligoyne systems leading to oligoenes and a cyanide transfer over four or six atoms.