Synthesis and reaction of 6‐substituted 3‐methoxycarbonyl‐4‐methylthio‐2H‐pyran‐2‐one derivatives

Reaction of aryl and styryl methyl ketones1a‐mwith dimethyl bis(methylthio)methylenemalonate (2) in the presence of potassium hydroxide in dimethyl sulfoxide gave the corresponding methyl 6‐aryl‐ and 6‐styryl‐4‐methylthio‐2‐oxo‐2H‐pyran‐3‐carboxylates3a‐m. 6‐Aryl derivatives3a‐d,gwere treated with sodium methoxide in methanol to give the corresponding 6‐aryl‐4‐methoxy‐2H‐pyran‐2‐ones8a‐dand9.Phenylcoumalin (7a) and paracotoin (7b) were synthesized by the desulfurization of 6‐aryl‐4‐methylthio‐2H‐pyran‐2‐ones4a,b.Similarly, anibine (8e) was also synthesized from3g. Treatment of3with hydrogen peroxide or 3‐chloroperoxybenzoic acid gave the corresponding 4‐methylsulfiny‐2H‐pyran‐2‐ones10a‐fin good yields. Displacement reactions of10a‐fwith nucleophilic reagents are also described.