Acetic Anhydride → HCID 11845599, compound

Participants

Reaction Conditions

Reaction Steps

5,5-Dioxo-4,5,6,7-tetrahydro-5λ6-pyrazolo[5,1-c][1,4]thiazine-2-carbaldehyde (1.95 g) was added to the dry acetonitrile (112 mL) solution of anhydrous MgBr2 (cont. 98%) (5.48 g) under a nitrogen atmosphere at room temperature. The dry THF solution (112 mL) of (5R,6S)-6-bromo-7-oxo-4-thia-1-azabicyclo[3.2.0]hept-2-ene-2-carboxylic acid 4-nitrobenzyl ester (cont. 96.5%) (3.88 g) was added to the mixture, cooled to −20° C., and Et3N (cont. 99%) (3.79 mL) was added in one portion. The reaction vessel was covered with foil to exclude light. The reaction mixture was stirred for 3 h at −20° C. and treated with acetic anhydride (cont. 97%) (3.79 mL) and DMAP (cont. 99%) (120 mg) in one portion. The reaction mixture was warmed to 0° C. and stirred for 16 h at 0° C. To the reaction mixture was added acetic anhydride (cont. 97%) (0.95 mL) and DMAP (cont. 99%) (120 mg) in one portion. The mixture was diluted with ethyl acetate and washed with 5% citric acid aqueous solution, saturated sodium hydrogen carbonate and brine. The organic layer was dried (MgSO4), followed by concentration under reduced pressure. The residue was purified with a silica-gel column chromatography (CHCl3:acetone=19:1-4:1) to give the titled compound as a pale brown amorphous solid (diastereo-mixture (8:2), 1.35 g, 22%).

Provenance & Evidence