Acetic Anhydride → 3,4-dihydro-1H-pyrrolo[2,1-c][1,4]oxazine-8-carboxylic acid ethyl ester

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Reaction Conditions

Reaction Steps

To a mixture of 4-formyl-morpholine-3-carboxylic acid (Comp. No. 1) (43 g, 0.295 mol) and acetic anhydride (410 g, 4 mol) was added ethyl propiolate (190 g, 1.94 mol). The resulting mixture was heated slowly to 120° C., which was accompanied by gas evolution. After heating for 2 h at 120° C., the resulting mixture was concentrated under reduced pressure. The crude product was purified by silica gel chromatography (eluting with up to 25% ethyl acetate in heptane) to give 21.4 g (37%) of pure 3,4-dihydro-1H-pyrrolo[2,1-c][1,4]oxazine-8-carboxylic acid ethyl ester. LC/MS (method 4): Rt=1.10 min; m/z=196.1 (M+H+).

Provenance & Evidence