Prepn. of 2-thenyl-5-hydantoin from 2-thenylidene-5-hydantoin - using reaction with phosphorus deriv. in acetic acid with iodine catalyst

摘要

Prepn. of (2-thenyl)-5-hydantoin (I) by reaction of (2-thenylidene)-5-hydantoin and a phosphorus deriv. selected from red phosphorus and phosphonic acid gp. contg. cpd. in acetic acid and in the presence of a catalytic amount of an iodine deriv. selected from iodine and hydrogen iodide. Pref. iodine deriv. is hydrogen iodide in aq. soln. The mole ratio between the hydrogen iodide and the (2-thenylidene)-5-hydantoin is 0.01-0.5. USE/ADVANTAGE - (I) is useful for the prodn. of beta-(2-thienyl)alanine. The process gives good yields and avoids the use of sodium amalgam or ammonium sulphide. In an example 100 g of pure acetic acid was mixed with 19.4 g of pure (2-thenylidene)-5-hydantoin, 15.5 g of red phosphorus, 1.12 g pf a 57% aq. soln. of hydrogen iodide and 1.8 g of water and heated for 210 mins. with boiling. The mixt. was cooled to 30 deg.C, filtered and the prod. crystallised out spontaneously, filtered, washed and dried giving 15.6 g of (I) as clear yellow crystals of MP 189 deg.C.