CsCF3B(OMe)3: A Versatile Nucleophilic Source of the Trifluoromethyl Anion

Abstract We have identified cesium trimethoxy(trifluoromethyl)borate [CsCF3B(OMe)3] as a nucleophilic source for the trifluoromethylation of carbonyl compounds. A differentiating characteristic of CsCF3B(OMe)3 is its heightened reactivity in ethereal solvents compared to its potassium analogue, which is typically employed in dimethylformamide. Also, in contrast to the extensively studied Ruppert–Prakash reagent (TMSCF3), CsCF3B(OMe)3 does not require the addition of an exogenous activator. Described herein, we detail the synthesis of CsCF3B(OMe)3 and demonstrate its efficacy in trifluoromethylation across various scaffolds, including methyl ketones, isatin derivatives, and 1,2-acyclic dicarbonyls.