Process for reducing 5-(2-thenylidene) hydantoin to 5-(2-thenyl) hydantoin

A process for preparing 5-(2-thenyl) hydantoin comprising reacting 5-(2-thenylidene) hydantoin in acetic acid with a phosphorous compound selected from the group consisting of red phosphorous and phosphonic acid, in the presence of catalytic quantities of an iodine compound selected from the group consisting of iodine and hydroiodic acid, wherein the molar ratio of phosphorous compound to 5-(2-thenyl) hydantoin is between about 1 and 5 and the molar ratio of iodine compound to 5-(2-thenylidene) hydantoin is between 0.01 and 0.5, and thereafter recovering 5-(2-thenyl) hydantoin from the reaction medium.

A process for reducing 5-(2-thenylidene) hydantoin to 5-(2-thenyl) hydantoin consisting of reacting 5-(2-thenylidene) hydantoin in acetic acid with a phosphorous compound selected from the group consisting of red phosphorous and phosphonic acid in the presence of water and a catalytic amount of an iodine compound selected from the group consisting of iodine and hydroiodic acid wherein the molar ratio of phosphorous compound to 5-(2-thenylidene) hydantoin is between 1 and 5, the molar ratio of iodine compound to 5-(2-thenylidene) hydantoin is between 0.01 and 5, and the molar ratio of water to 5-(2-thenylidene) hydantoin is between 1 and 5, and thereafter recovering 5-(2-thenyl) hydantoin from the reaction medium.