Abstract: The cyclobutanone oxime 6 reacts with disulfur dichloride, N-chlorosuccinimide, and Hünig's base to give three unexpected 10 π pseudoazulenes in low yield:  the dark blue cyclopenta-1,2-dithiole 7, its red isomer 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 methylenoindene 16 in high yield. The formation of all of these products can be explained by a unified mechanism based on initial abnormal Beckmann rearrangement of the oximes to cyanides followed by cyclization and/or exhaustive chlorination and dehydrochlorination. The 1,2-dithiole 7 is synthesized independently from 1-(cyanomethyl)cyclopentene 11 and the above reagents, and 1-cyanomethylindene 17 is similarly converted into methylenoindenes 18 and 19, which are isomers of product 16. Structures 7 and 15 are confirmed by X-ray crystallography, and compounds 7, 8, 15, 16, 18, and 19 show birefringence on heating in a hot stage polarizing microscope indicating, most unexpectedly, liquid crystalline behavior.

Cite: Rakitin O.A. , Rees C.W. , Williams D.J. , Torroba T.
Cyclopenta-1,2-dithioles, Cyclopenta-1,2-thiazines, and Methylenoindenes from New Molecular Rearrangements
Journal of Organic Chemistry. 1996. V.61. N26. P.9178-9185. DOI: 10.1021/jo9612234 WOS OpenAlex

Identifiers:

Web of science:	WOS:A1996WC12000019
OpenAlex:	W2952395534

Citing:

DB	Citing
OpenAlex	37
Web of science	31

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