反应详情

Sodium borohydride (2.54 g, 0.066 mol) is added in portions over a 30 minute period to a stirred suspension of diethyl 5-(bromoacetyl)-1,6-dihydro-6-oxo-2,3-pyridinedicarboxylate (57.2 g, 0.159 mol) at 10°-20° C. Upon completion of the sodium borohydride addition, the reaction mixture is stirred while attaining room temperature. Ice (100 g) is added and the mixture stirred until the ice has melted. The mixture is then concentrated in vacuo and the residue crystallized twice from an ethyl acetate-hexane mixture to give pure diethyl 5-(2-bromo-1-hydroxyethyl)-1,6-dihydro-6-oxo-2,3-pyridinedicarboxylate mp 134°-138° C. Stirring this compound with triethylamine (1.0 mL/g of solid) in methylene chloride for one hour, followed by washing the organic solution with dilute hydrochloric acid, water, brine and drying over anhydrous MgSO4 yields the crude furo[2,3-b]pyridine as an oil upon removing the solvent in vacuo. Crystallization from a cyclohexane-toluene mixture affords pure diethyl 2,3-dihydro-3-hydroxy-furo[2,3-b]pyridine-5,6-dicarboxylate mp 73°-77° C.

1. customwhile attaining room temperature
2. concentrationThe mixture is then concentrated in vacuo
3. customthe residue crystallized twice from an ethyl acetate-hexane mixture