Biginelli-Atwal Reactions of (+)-Pulegone: An Entry into Chiral Hexahydroquinazolin-2-one Derivatives

Biginelli-Atwal condensations of (+)-pulegone with (thio)ureas and guanidine afford hexahydroquinazoline-2(1H)-ones (-thiones) and/or 2-amino-1,3-thiazines with selectivities that depend on both the (thio)ureas and the experimental conditions. Carboannelation of these heterocyclic adducts with diethyl ethoxymethylenemalonate leads to uncommon pyrimidoquinazoline and pyrimidobenzothiazine systems.