Ambidoselective Dithiocarboxylation and Thiocarbamoylation of β‐Keto Enolates

Treatment of β‐keto enolates 1 with carbon disulfide in the presence of sodium hydride and subsequent alkylation yield the open‐chain or cyclic acylformylketene S,S‐acetals 3 and 4, respectively. Thiophenes 5, 6, or 7 and thieno[2,3‐b]thiophenes 8 are formed by using as alkylating agents first methyl iodide and then an α‐CH‐acidic halo compound or only two equivalents of the latter. β‐Keto enolates 1 also react with phenyl isothiocyanate to give acylformylketene S,N‐acetals 10, aroylthiophenes 11 or thiazolidin‐4‐ones 12.