CYCLOPENTA-1,2-DITHIOLES, CYCLOPENTA-1,2-THIAZINES, AND METHYLENOINDENES FROM NEW MOLECULAR-REARRANGEMENTS

The cyclobutanone oxime 6 reacts with disulfur dichloride, N-chlorosuc cinimide, and Hunig's base to give three unexpected 10 pi pseudo azule nes in low yield: the dark blue cyclopenta-1,2-dithiole 7, its red iso mer 10, and the orange cyclopenta-1,2-thiazine 8. The benzo derivative 14 of oxime 6 gives an analogous benzo product 15 together with the m ethylenoindene 16 in high yield. The formation of all of these product s can be explained by a unified mechanism based on initial abnormal Be ckmann rearrangement of the oximes to cyanides followed by cyclization and/or exhaustive chlorination and dehydrochlorination. The 1,2-dithi ole 7 is synthesized independently from 1-(cyanomethyl)cyclopentene 11 and the above reagents, and 1-cyanomethylindene 17 is similarly conve rted into methylenoindenes 18 and 19, which are isomers of product 16. Structures 7 and 15 are confirmed by X-ray crystallography, and compo unds 7, 8, 15, 16, 18, and 19 show birefringence on heating in a hot s tage polarizing microscope indicating, most unexpectedly, liquid cryst alline behavior.