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UNEXPECTED CONVERSION OF 4-OXO-4H-CHROMENE-2-CARBOXYLIC ACID TO 2-(1,3-BENZOTHIAZOL-2-YL)-4H-CHROMEN-4-ONE AND SPIRO[1,4-BENZOTHIAZINE-2,2'-CHROMENE]-3,4'(3'H,4H)-DIONE

Fernando Cagide, Lígia R. Gomes, John N. Low, Fernanda Borges
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Abstract


2-(1,3-Benzothiazol-2-yl)-4H-chromen-4-one and spiro[1,4-benzothiazine-2,2'-chromene]-3,4'(3'H,4H)-dione have been synthesized from 4-oxo-4H-chromene-2-carboxylic acid. The course of the reaction that usually occurs between the activated carboxylic acid and aromatic amines was changed upon the use of different reaction conditions (acidic or basic) and 2-aminobenzenethiol. As a result, new heterocyclic derivatives were obtained. Structures of the compounds have been established on the basis of spectral (1D and 2D NMR spectra) and X-ray data.


Keywords


2-aminobenzenethiol; 2-(1,3-benzothiazol-2-yl)-4H-chromen-4-one; benzotriazol-1-yloxytripyrrolidinophosphonium hexafluorophosphate; chromene-2-carboxylic acid; spiro[1,4-benzothiazine-2,2'-chromene]-3,4'(3'H,4H)-dione; phosphorus oxychloride; acidic vs basic conditions.

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Latvian Institute of Organic Synthesis - Aizkraukles iela, 21, Riga, LV-1006, Latvia - hgs@osi.lv