Carbamic acid, ethyl ester → 2,6,7-Trimethylquinazolin-4(3H)-one

Participants

Reaction Conditions

Reaction Steps

A mixture of 3,4-dimethylacetanilide (16.3 g), ethyl carbamate (14 g), phosphorus pentoxide (30 g) and xylene (55 ml) was stirred vigorously using a mechanical stirrer under an atmosphere of argon. The mixture was slowly heated to approximately 60° C. whereupon a visible reaction ensued with the evolution of heat and with an increase in the viscosity of the mixture. The temperature of the mixture was raised over a period of 90 minutes to 150° C. and the mixture was stirred at this temperature for 2 hours during which time more phosphorus pentoxide (12 g in total) was added portionwise. The mixture was cooled and the xylene was decanted. A mixture of ice and water (250 ml) was added to the residue and the mixture was stirred for 30 minutes and filtered. The solid was analysed by thin layer chromatography using ethyl acetate as solvent and if it contained any product it was purified by chromatography as described for the residue obtained below. The filtrate was cooled in an ice bath to a temperature of less than 5° C. and the acidity of the solution was reduced to pH 5 by the addition of a concentrated aqueous sodium hydroxide solution. The mixture was extracted with ethyl acetate (2×50 ml) and the combined extracts were dried over magnesium sulphate, filtered and evaporated. The residue was purified by chromatography on a silica gel column using a 1:1 v/v mixture of methylene chloride and ethyl acetate as eluent. There were thus obtained, in order of elution, 3,4-dihydro-2,6,7-trimethylquinazolin-4-one (2 g) and 3,4-dihydro-2,5,6-trimethylquinazolin-4-one (2 g).

Provenance & Evidence