Issue 0, 1982

Ring contractions of thiochroman-4-ones and thiochromen-4-ones

Abstract

3-Bromothiochroman-4-one and its S-oxide undergo ring contraction on heating, especially in the presence of sodium acetate, to give mixtures which include thioindigo (9) and the ethanediylidenethioindigo (10). Brominated 2,2-dimethylthiochroman-4-one reacts on silica gel to form thioindigo, thioindirubin, and the bis(benzothieno)pyran (17).

Bromination of thiochromanone gives a number of products, including 2,3-dibromothiochromen-4-one S-oxide which, on heating with sodium acetate in acetic acid, is converted efficiently into thioindigo. The mechanism of this reaction is investigated.

Article information

Article type
Paper

J. Chem. Soc., Perkin Trans. 1, 1982, 395-402

Ring contractions of thiochroman-4-ones and thiochromen-4-ones

N. E. MacKenzie and R. H. Thomson, J. Chem. Soc., Perkin Trans. 1, 1982, 395 DOI: 10.1039/P19820000395

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