T3P-Promoted Synthesis of a Series of Novel 3-Aryl-2-phenyl-2,3,5,6-tetrahydro-4H-1,3-thiazin-4-ones

A series of 12 novel 3-aryl-2-phenyl-2,3,5,6-tetrahydro-4H-1,3-thiazin-4-ones was prepared at room temperature by T3P-mediated cyclization of C-phenyl-N-aryl imines with 3-mercaptopropionic acid. Both electron-withdrawing and electron-donating substituents were used. All substituents were successful, including p-nitro. Some reactions were run as 3-component reactions, forming the imine in situ. The reactions were operationally simple and gave yields as high as 79%. An example was also done where a p-nitro group was on both the C-aryl and the N-aryl. This provides ready access to N-aryl compounds in this family, which have been generally difficult to prepare.