The reactions of electron-deficient 1Н-benzo[f]chromenes with 2,3-dimethylbenzothiazol-3-ium iodide

Abstract

The action of 2,3-dimethylbenzothiazol-3-ium iodide on 1H-benzo[f]chromenes containing an acceptor substituent in the β-position to the oxygen atom in the presence of triethylamine results in the opening of the pyran ring and the formation of [(2E,4Z)-4-(3-methyl-benzothiazol-2(3H)-ylidene)but-2-en-1-yl]naphthalen-2-ols. In the case of 1-aryl-2-nitro-1H-benzo[f]chromenes, 3-methyl-2-[(1E,3Z)-3-(3-methylbenzothiazol-2(3H)-ylidene)prop-1-en-1-yl]benzothiazol-3-ium iodide was isolated. The resulting compounds containing the merocyanine chromophore are of interest as dyes and fluorescent labels.