Organoboron Reagent Usable for Trifluoromethylating Reactions

Potassium trimethoxy(trifluoromethyl)borate (1) is a white solid which can be used as a trifluoromethylating reagent with easier handling.^1-5) For example, 1 reacts with aldehydes, ketones and imines without α-protons under heating wherein the nucleophilic trifluoromethylation to their carbonyl or imino group proceeds in good yields.²⁾ On the other hand, when substrates having α-protons are treated with 1, the trifluoromethylation competitively proceeds with the self-aldol condensation. Furthermore, by the use of copper salts with 1, cross coupling reactions with aryl iodides³⁾ and aryl pinacolborane derivatives⁵⁾ successfully proceed and the corresponding trifluoromethyl group-substituted aromatic compounds are given. In this way, 1 is an inexpensive and easier handling nucleophilic trifluoromethylating reagent and is expected to be used in organic synthesis.