By using d8-THF as solvent, the reaction of 1a and 1e with 2a afforded products 4a and 4e with 40% and 20% deuterium incorporation, respectively, at the α-position of the trifluoromethyl group, suggesting that THF is likely to functionalize as a partial hydrogen source (Scheme 4c). Then, two deuterated Hantzsch esters were prepared and subjected to the reaction of 1e with 2a. When HE2 was replaced with 1-d-HE2, the reaction proceeded with a comparable yield but no deuterium incorporation at the α-CF3 position.