Formose Reactions. XXI. A Selective Formation of Dihydroxyacetone in the Formose Reaction in N,N-Dimethylformamide

Dihydroxyacetone (DHA) was obtained in good yield from the selective formose reaction which was conducted with 2-(dimethylamino)ethanol and vitamin B1 in N,N-dimethylformamide (DMF). The major products were isolated from the formose and identified as dihydroxyacetone and 2-(1,2-dihydroxyethyl)-5-(2-hydroxyethyl)-4-methylthiazole by spectral data. Vitamin B1 suppressed the vaporization of formaldehyde from the reaction solution. Irrespective of the 2-(dimethylamino)ethanol concentration (above 0.1 M (1M=1 mol dm−3)), the maximum yield of DHA was 80–90 glc% at 1.0 M formaldehyde concentration, when the formaldehyde consumption was above 90%. Above 3.0 M formaldehyde concentration, selective formation of DHA (above 80 glc%) was obtained at the early stage of the reaction. The scheme for the formation of DHA in the formose reaction in the presence of vitamin B1 was also proposed.