Ethyl orthoformate → N-[2,3-bis(4-methyl-1-piperazinyl)-6-quinoxalinyl]formimidic acid ethyl ester

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Reaction Steps

A 17.05 g. portion of 6-amino-2,3-bis(4-methyl-1-piperazinyl)quinoxaline (prepared as in Example 1) is thoroughly mixed with 100 ml. of triethylorthoformate, then 5 drops of concentrated sulfuric acid is added with magnetic stirring and the mixture is heated at reflux in an oil bath (145°-150° C.). The solid is dissolved in about 30 minutes but shortly thereafter a yellow solid is precipitated out. Stirring is continued and the mixture allowed to reflux overnight at a distillate temperature of about 75°-80° C. After refluxing for 16 hours the reflux condenser is replaced with a takeoff condenser with a 10 cm. Vigreux column attached and 6.5 ml. of distillate with a boiling point of about 80° C. is collected over a 21/2 hour period. The maximum oil bath temperature over this period of time is 180° C. The reaction mixture is cooled and the liquid layer is decanted from a small amount of insoluble material. The decanted liquid is stripped of solvent by water pump evacuation and the residual oil is triturated with 50 ml. of hexane and heated to boiling on the steam bath to dissolve the oil. The solution is cooled in an ice bath to yield a solid yellow mass. Additional hexane is added and the precipitate is filtered, washed on the filter with hexane, and pressed dry with suction to give 18.5 g. of the product of the example as a yellow solid.

Provenance & Evidence