The Catalytic Aminolysis Of Dithioacetals And Its Application In The Elaboration Of Tetronic Acid Derivatives

Dithioacetals, which are first synthesized from 1885, have proven to be very useful in organic synthesis. Besides the use as a latent carbonyl, methylene group, and an umpolung of the carbonyl group, the synthetic potential of dithioacetal functionality has been widely expanded in recent years. For example, Luh and coworkers demonstrated the Nickel catalyzed olefination reactions of benzylic, allylic, aliphatic and propargylic dithioacetals (function as germinal dication synthons) with Grignard reagents. Takeda et al. reported the desulfurizative metalation of dithioacetals to form titanium-alkylidens species which could produce C-C double bond with aldehydes, ketones and esters. But yet there is no report about the C-N bond formation via direct aminolysis of dithiocetals. In our research on the synthetic applications of dithioacetals, we discovered a new C-N bond forming reaction via direct aminolysis of dithioacetals. Catalyzed by copper acetate, the reactions of dithioacetals with ammonia, primary or secondary amines gave enaminones in high to excellent yields, respectively, under mild conditions.1. In THF solution, under Cu(OAc)₂·H₂O catalyst, we synthesized twenty-four ammonia, prinary and secondary amines substituted tetronic acid derivatives 5aa-5cd and compared the reaction activity of these different ammonia, prinary and secondary amines.2. As an extension of the new C-N coupling reaction, dithioacetals 10a-g were then synthesized and subjected to the reaction sequence. Under the identical conditions, the C-N cross-coupling reaction of 10a-g with n-butylamine was proven to be successful and the corresponding enaminones 11a-g were synthesized in high to excellent yields.In this paper, twenty-nine new products were synthesized and characterized via ¹H NMR, ¹³C NMR and IR.