Dimethylformamide → 3-(5-Cyclopropyl-1,2,4-oxadiazol-3-yl)-4,5-dihydroimidazo[1,5-a]quinoxaline

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Reaction Steps

A solution of the 1,2,3,4-tetrahydroquinoxalin-2-one (IV, 5.51 g) and THF (55 ml) is cooled to -40°, and potassium tert-butoxide (1.0M in THF, 34.8 ml) is added dropwise over 5 min. The mixture is allowed to warm to -20° over 1 hr. DMF (10 ml) and THF (40 ml) are added to the resultant solid, allowing the mixture to stir. The mixture is cooled to -50°, and diethyl chlorophosphate (5.02 ml) is added dropwise over 5 min. The mixture is allowed to warm to -20° over 1 hr. The mixture is cooled to -78°, and the oxadiazole isocyanide (5.70 g) is added. Potassium tert-butoxide (34.8 ml) is added dropwise over 15 min, the mixture is allowed to warm slowly to 20°-25°, and is stirred for 3 days at 20°-25°. The mixture is quenched with water, filtered, washed with water and dried to provide the desired material as a solid. Additional solids that precipitated from the filtrate are filtered, triturated with ethyl acetate/hexane (20/80) and dried to give the title compound, mp 243°-245°; NMR (CDCl3) 8.07, 7.42, 7.10, 6.8-6.9, 4.81, 4.08, 2.2-2.3 and 1.2-1.4 δ.

Provenance & Evidence