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Communication | Regular issue | Vol 22, No. 4, 1984, pp.675-679
Published online, 1st January, 1970
DOI: 10.3987/R-1984-04-0675
Regiocontrolled Cyclisation to the Isomeric Dipyridazino[4,5-b:4‘,5‘-e][1,4]thiazines — Competence and Performance of Benzylamino and Thioether Functions on the 3(2H)-Pyridazinones as Regiocontrolling Elememts

Kenji Kaji, Hiromu Nagashima, and Hirohisa Oda*

*Gifu Pharmaceutical University, 6-1 Mitahora-higashi 5-chome, Gifu 502-8585, Japan

Abstract

The 5,5’-thioethers (5a-c) perform a regiocontrolled cyclisation affording either the 10H-dipyridazino[1,4]thiazine-1,9-diones (1’a-c) (by Ullmann mode) or the 10-benzyl derivatives of 1,6-dione isomers (2a-c) (via Smiles rearrangement), only depending on the acidity of media employed. The 4,5’-thioethers (6a-c) exhibit also the regiospecific control to give exclusively the 10H-dipyridazino[1,4]thiazine-1,6-diones (2’a-c) in acidic conditions or the 10-benzyl-4,6-dione isomers (3a-c) in basic conditions, respectively. Some principal features of the regiocontrolled cyclisation are discussed.