Formose Reactions. XXVIII. Selective Formation of 2,4-Bis(hydroxymethyl)-3-pentulose in N,N-Dimethylformamide–Water Mixed Solvent

Dihydroxyacetone, Dl-glycero-tetrulose, and 2,4-bis(hydroxymethyl)-3-pentulose (2,4-BH-3-P) were favorably formed in a formose reaction by choosing a suitable ratio of water to N,N-dimethylformamide used as solvent or a suitable [thiamine·HCl]/[HCHO] ratio. The formose reaction was strongly affected by the concentration of formaldehyde in the water layer. Under the reaction conditions studied, thiamine decomposed rapidly. 2,4-BH-3-P was isolated from the reaction mixture and characterized by MS, IR, and NMR techniques. A pathway for the formation of 2,4-BH-3-P was also proposed.