SYNTHESIS OF SYMMETRICAL 2,2',4,4'-TETRASUBSTITUTED [4,4'-BITHIAZOLE]-5,5'(4H,4'H)-DIONES AND THEIR REACTIONS WITH SOME NUCLEOPHILES

Symmetrical asubstituted-[4,4'-bithiazole]-5,5'(4H,4'H)-diones were ob tained in high yields by oxidation of 5(4H)-thiazolones by KMnO4 in ac etic acid. In some cases, the isomeric 2.4'- and 2,2'-bithiazolones we re also formed. Results from two crossover reactions were consistent w ith a free radical mechanism. Four series of thiazolones were prepared , each based on a different substituent at the 2-position; i.e., pheny l, ethoxy, ethyl and ethylthio. The effects of substituents on the iso mer distributions of the dehydrodimers indicated that electronic facto rs were less important than steric factors. X-Ray crystallography esta blished the structure of the dehydrodimer 4,4'dibenzyl-[4,4'-bithiazol e]-5,5'(4H,4'H)-dione. One stereoisomer of 4,4'-dimethyl-[4,4'-bithiaz ole]-5,5'(4H,4'H)-dione and a mixture of the stereoisomers of 4,4'-dib enzyl-[4,4'-bithiazole]-5,5'(4H,4'K)-dione were treated with nucleophi les. The former gave imide derivatives of alpha,alpha'-dehydrodimeric amino acids when the nucleophile was L-alanine ethyl ester or I-butyla mine. The structure of one of the reaction products, (4R,5R*)-2,5-dip henyl-2-thiazoline-4-carboxylic acid piperidylamide, was established b y X-ray crystallography. Treatment of stereoisomeric mixtures of 2,2'- diethoxy-4,4'-bithiazolones with HCl in benzene gave the corresponding racemic and meso bis-(N-carboxythioanhydride)s. A stereoisomeric mixt ure of the bis(N-carboxythioanhydride)s of leucine treated with glycin e ethyl ester gave a bicyclic derivative of the alpha,alpha'-dehydrodi meric amino acid.