Abstract
Reaction of 2-chloro-N, N-dimethyl-2-(phenylthio) acetamide (1a) with styrene in the presence of stannic chloride gave 3, 4-dihydro-N, N-dimethyl-4-phenyl-2H-1-benzothiopyran-2-carboxamide. The same benzothiopyran was also obtained from N, N-dimethyl-2-(phenylsulfinyl) acetamide and styrene under the Pummerer reaction conditions, but in lower yield. Similarly, α-chlorosulfides derived from ethyl 2-(phenylthio) acetate, 2-(phenylthio) acetonitrile, 1-(phenylthio)-2-propanone, and thioanisole reacted with styrene to give the corresponding 4-phenylbenzothiopyrans in variable yields. The reaction of 1a with trans-stilbene gave the expected benzothiopyran derivative, but the reaction of 1a with 1, 1-diphenylethylene and phenylacetylene showed some variation of the reaction course. This cycloaddition reaction was extended to the intramolecular case. A possible mechanism for the formation of the benzothiopyran is discussed.
