•
Trihaloacetic acids react with aldehydes in DMSO at room temperature to give trihalomethyl carbinols: J. Chem. Soc., Perkin 2, 1247 (1984):

• The acid and its Na salt (1:1) in DMF are also effective: Tetrahedron Lett., 33, 3435 (1992). Use of HMPA or DMI extends the scope to less reactive aldehydes: Synthesis, 327 (1990).