On the reactivity of 2-alkyl-1,3-thiazolium-4-olates toward electrophiles

On the basis of our synthetic methodologies employing mesoionic synthons, the nucleophilic character of 2-alkyl-1,3-thiazolium-4-olates (2-alkylthioisomünchnones) has been envisaged and developed, at the expenses of their common role as masked 1,3-dipoles. Reactions with aliphatic acid chlorides lead to monoketones derived from thiazolidin-4-ones, whose structure can be rationalized in terms of orbital interactions by computational studies. Aromatic acid chlorides invariably produce 1,3-dicarbonyl compounds, yet maintaining the mesoionic core. Unlike [3+2]-cycloadditions reported previously for thioisomünchnones with isocyanates and isothiocyanates, these heterocumulenes react with 2-alkylthioisomünchnones affording conjugated amides or thioamides.