Formose Reactions. XIV. A Selective Formose Reaction in the Presence of a Slight Amount of Calcium Ions

It was found that a formose reaction in the presence of small amounts of calcium and d-fructose gave rise to three products, 2-(hydroxymethyl)glycerol, 3-(hydroxymethyl)pentitol, and 2,4-bis(hydroxymethyl)pentitol, with a high selectivity. Various factors affecting the selectivity were also discussed: [Ca], pH, [d-fructose], the reaction temperature, co-catalysts, and metal hydroxides. The amount of formaldehyde relative to [Ca] is the most important factor in obtaining the selective formation of the three-branched sugar alcohols. Under these reaction conditions, the α,β-enediol structure is required in an effective co-catalyst for the formose reaction. 2-(Hydroxymethyl)glycerol, 3-(hydroxymethyl)pentitol, and 2,4-bis(hydroxymethyl)pentitol were formed with a high selectivity in the formose reactions catalyzed by KOH, Mg(OH)2, Fe(OH)3, and LiOH.