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Expected and unexpected reactions of 1,3-benzothiazine derivatives, II. Formation of isomeric 5,6-dihydro-1,5-benzothiazocines |
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| Authors: | Lajos Fodor Péter Csomós Antal CsámpaiPál Sohár Tamás HolczbauerAlajos Kálmán |
| Institution: | a Central Laboratory, County Hospital, H-5701 Gyula, POB 46, Hungary b Institute of Pharmaceutical Chemistry, University of Szeged, H-6720 Szeged, Eötvös u. 6., Hungary c Research Group of Stereochemistry of the Hungarian Academy of Sciences, H-6720 Szeged, Eötvös u. 6., Hungary d Institute of Chemistry, Eötvös Loránd University, H-1518 Budapest, POB 32, Hungary e Protein Modelling Research Group, Hungarian Academy of Sciences and Eötvös Loránd University, H-1518 Budapest, POB 32, Hungary f Institute of Structural Chemistry, Chemical Research Centre, Hungarian Academy of Sciences, H-1525 Budapest, POB 17, Hungary |
| Abstract: | A method for the synthesis of medium-sized 1,5-benzothiazocines by ring enlargement of 1,3-benzothiazines has been developed. When N-alkyl-1,3-benzothiazines were reacted with dimethyl acetylenedicarboxylate in acetonitrile at room temperature, regioisomeric 5,6-dihydro-2H-1,5-benzothiazocines and 5,6-dihydro-4H-1,5-benzothiazocines were obtained as novel ring systems. Dimethyl acetylenedicarboxylate could attack either the nitrogen or the sulfur atom of the thiazines. NMR spectroscopic and X-ray crystallographic investigations confirmed the structures of the products. |
| Keywords: | Ring expansion Medium-sized ring 1 5-Benzothiazocines DMAD NMR X-ray crystallography |
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