Issue 8, 1999

One-pot synthesis of indeno-1,2-thiazines, -[1,2]dithioles and thiophenes; new liquid crystalline materials

Abstract

In a search for further examples of a new type of discotic liquid crystal, we have examined the reactions of S2Cl2 in the presence of a chlorinating agent (NCS) and a base (Hünig’s base or DABCO), mostly in THF, with cyclopent-1-enylacetic acid 6, inden-3-ylacetic acid 8 and its nitrile 16 and 1-(dicyanomethylene)indane 22. The cyclopentene acid 6 gives purple crystals of the trichlorocyclopenta[1,2]dithiole ester 7, the product of heterocyclic ring formation, chlorination and dehydrochlorination and, unexpectedly, conversion of the acid in THF into its 4-chlorobutyl ester. Indenylacetic acid 8 gives methyleneindenes 10 and 11, the tricyclic 1,2-dithiolone 12 and the deep purple thiophene 13. Indenylacetonitrile 16 gives the chlorocyanomethylene indane 17 and the E- and Z- isomers of both the dichloroindene 18 and the monochloroindane 19, depending upon the precise reaction conditions. Dicyanomethylene indane 22 gives the dichloroindene 23 and the red, thermochromic indeno-1,2-thiazine 24; the analogous cyano-ester 25 gives the corresponding products. On melting, crystals of 13 and 23 are strongly birefringent. Mechanisms are proposed for the new transformations.

Article information

Article type
Paper

J. Chem. Soc., Perkin Trans. 1, 1999, 1023-1028

One-pot synthesis of indeno-1,2-thiazines, -[1,2]dithioles and thiophenes; new liquid crystalline materials

L. S. Konstantinova, O. A. Rakitin, C. W. Rees, L. I. Souvorova and T. Torroba, J. Chem. Soc., Perkin Trans. 1, 1999, 1023 DOI: 10.1039/A809808E

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