Abstract
The reaction of 4-methyl-2-methylaminothiazole (1a) and N, N-dimethylthiocarbamoyl chloride (2a) in a nonpolar solvent gave four products, 4-methyl-2-methylimino-3-(N, N-dimethylthiocarbamoyl)-4-thiazoline (3a), 1, 1, 3-trimethyl-3-(4-methyl-2-thiazolyl) thiourea (4a), 4-methyl-2-methylamino-5-(N, N-dimethylthiocarbamoyl) thiazole (5a), and 1, 1-dimethyl-3-(3, 4-dimethyl-2 (3H)-thiazolyidene) thiourea (6a). The 2-phenylamino analog of 1a (1b) gave the corresponding phenyl compounds (3b-6b) on reaction with 2a. Compounds 3a and 3b were isomerized to 6a and 6b, respectively, in dioxane with a drop of hydrochloric acid. From studies with 15N-labeled compounds, a mechanism is proposed involving a proton-induced ring transformation of 3, via protonation of 3, cleavage of the 3, 4-bond, and bond formation between the imino nitrogen and 4-carbon atoms. A similar ring transformation took place with 3-N, N-dimethylcarbamoyl analogs of 3a and 3b, but not with a thiazolidine analog of 3b.
