Abstract 4-Methyl-5-(substituted) imino-1, 2, 3, 4-thiatriazolines 1 (R 2≠ Me) undergo cycloaddition-elimination reactions with isocyanates to yield 4-methyl-5-(substituted) imino- 1, 2, 4-thiadiazolidine-3-ones 5 via the thermodynamically less stable isomers 4. The latter have not been isolated, except for 4q which was shown to iso-merize rapidly into 5q with phenylsulfonyl isocyanate. The reactions of 1 are accelerated by using less bulky R 2 ...
