Tandem Thien- and Benzannulations of α-Alkenoyl-α-alkynyl Ketene Dithioacetals with Cyanoacetates: Synthesis of Functionalized Benzo[b]thiophenes
摘要:
A novel domino annulation strategy for the construction of benzo[b]thiophenes has been developed. In the presence of Cs2CO3 and Ag2CO3, a wide range of alpha-alkenoyl-alpha-alkynyl ketene dithioacetals readily react with cyanoacetates in CH3CN at 110 degrees C under N-2 to afford multisubstituted benzo[b]thiophenes efficiently via tandem thien- and benzannulations. A plausible mechanism is also proposed.
The iododecarboxylation reaction of alpha-carboxylate, alpha-cinnamoyl ketene cyclic dithioacetals 2 was successfully performed with iodine as halogenation reagent and in water insensitive media. This reaction provides a mild and efficient method for the preparation of alpha-iodo, alpha-cinnamoyl ketene cyclic dithioacetals 3 which are important kinds of potential new intermediates to be valued.