tert-Butanol → 3-tert-butyloxycarbonylamino-4-(2-methylphenyl)-7,8-dihydro-6H-cyclopenta[g][1]benzopyran-2-one

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Reaction Steps

To a solution of 4-(2-methylphenyl)-2-oxo-2,6,7,8-tetrahydrocyclopenta[g][1]benzopyran-3-carboxylic acid (2.5 g) and diphenyl phosphoryl azide (DPPA, 2.58 g) in tert-butanol (25 ml) was added triethylamine (1.1 ml) dropwise and the mixture was stirred at room temperature for 30 minutes and, then, refluxed for 4 hours. The solvent was distilled off and the residue was diluted with water and extracted with ethyl acetate. The extract was washed with water, dried (MgSO4) and distilled to remove the solvent, whereby 3-tert-butyloxycarbonylamino-4-(2-methylphenyl)-7,8-dihydro-6H-cyclopenta[g][1]benzopyran-2-one was obtained as oil. The oil was crystallized from hexane (2.95 g, 96.7%). Recrystallization from ethanol-hexane gave colorless prisms, m.p. 154°-155° C.

Provenance & Evidence