Synthesis of Heteroaromatic Compounds by Newly Extended Pummerer Reactions

Ketene dithioacetal monoxides (KDMs) bring out a variety of latent intriguing reactivity upon treatment with triflic anhydride. The extended Pummerer reactions of KDMs provide reliable accesses to heteroaromatic compounds including (benzo) furan, (benzo) thiophene, and pyrroles. Trifluoromethyl-substituted KDMs are useful building blocks to prepare alpha-trifluoromethyl carbonyl compounds and 3-trifluoromethyl heteroaromatic compounds. A newly uncovered interrupted Pummerer reaction/ [3,3] sigmatropic rearrangement cascade is the key that realizes most of the transformations in this paper. The last part of this paper describes the first example of metal-catalyzed Pummerer reaction where sulfoxides are directly activated by the catalyst.