Synthesis and Catalysis of Strong Carbon Acids Containing Bis(triflyl)methyl Group

Abstract

Bis(trifluoromethylsulfonyl)methyl (Tf₂CH; Tf=SO₂CF₃) group is an appealing acidic functionality for development of novel organocatalysts. It has been reported that some compounds bearing Tf₂CH functionality show notably strong acidity in both solution and gas phases, although the catalysis of such carbon acids has not been defined for a long time. On the other hand, we recently found that 1,1,3,3-tetrakis(trifluoromethylsulfonyl)propane (Tf₂CHCH₂CHTf₂) performs as an excellent catalyst for several carbon-carbon bond forming reactions using silicon enolates. Furthermore, as an effective strategy to prepare a novel type of carbon acid catalysts, we reported that Tf₂CHCH₂CHTf₂ can be successfully used as a suitable reagent for incorporating Tf₂CH functionality to neutral nucleophiles. On the basis of this strategy, multiple carbon acid catalysts were developed. Such carbon acids are effective but easy-to-handle acid catalysts.