Dihydroxyacetone → 1,3-Diacetoxyacetone

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Reaction Steps

A 16 L reactor equipped with a mechanical stirrer, a Pt-100 thermometer, a reflux condenser and a nitrogen inlet was charged with 1.00 kg (10.9 mol) 1,3-dihydroxyacetone and 3.25 L (4.03 mol) pyridine. To this suspension 3.31 L (34.8 mol) acetic acid anhydride was added during 35 min, maintaining the temperature between 15 and 22° C. with a cooling bath. During the addition the suspension turned into a clear, slightly reddish solution. The mixture was stirred for 2.5 h at RT before it was concentrated on a rotatory evaporator at 50-55° C./10 mbar. The oily residue was dissolved in 10.0 L dichloromethane and washed two times with 5.0 L 2N hydrochloric acid, then with 5.0 L water. The organic layer was concentrated on a rotatory evaporator at 40° C./10 mbar and the oily residue was further dried under these conditions for 1.5 h. The dark red crude product (2 kg) was dissolved in 5.7 L toluene and the solution was warmed to 30° C. 5 L heptane were added during 10 min and the resulting turbid solution was seeded with product crystals, whereas fast crystallization occurred. 5 L heptane was added to the suspension to improve stirability. After stirring overnight at RT the suspension was cooled to 0° C. and stirred for 2 h at that temperature. The crystals then were filtered off and washed portionwise with totally 7 L of pre-cooled heptane. The crystals were dried at 30-35° C. at <=10 mbar over the weekend, to give 1.47 kg 1,3-diacetoxyacetone (78% yield; assay: 100%).

Provenance & Evidence