2,2‐dichloroaldehydes from aldehydes and alcohols by chlorination in dimethylformamide

A method is described for the synthesis of α,α‐dichloroaldehydes, free from monochloroaldehyde, by chlorination of aldehydes or alcohols in dimethylformamide at 40–90°C. Results are reported for: (yield %) propanal (90), butanal (78), pentanal (78), 3‐methylbutanal (90), propanol (64), butanol (78), 3‐methylbutanol (52), pentanol (66), 3,3‐dimethylbutanol (86), hexanol (66), 2‐phenylethanol (51), 3‐phenylpropanol (54), 1,5‐pentanediol [3,3‐dichloro‐2‐hydroxytetrahydropyran (37), 2,3,3‐trichlorotetrahydropyran (19)], 1,6‐hexanediol [2,2,5,5‐tetrachloro‐1,6‐hexanedial (63)]. Oxidative conversion (KMnO4, K2Cr2O7, H2O2‐NaHCO3) into α,α‐dichlorocarboxylic acids and methyl esters is discussed.