- Synthesis of Pyridazinothiadazines and the Ring Contraction to Pyrazolopyridazines through Extrusion of Sulfur
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Cyclization of 2-substituted 5-4-chloro-3(2H)-pyridazinones (2) with potassium thioacetate, followed by deacetylation, provided new ring system derivatives, 7-substituted 2-phenyl-4H-pyridazinothiadiazin-8(7H)
- Kaji, Kenji,Nagashima, Hiromu,Nagao, Sigeto,Tabashi, Keizo,Oda, Hirohisa
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p. 4437 - 4446
(2007/10/02)
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- SYNTHESIS OF PYRAZOLOPYRIDAZINE DERIVATIVES- TWO COMPARABLE APPROACHES, RING CONTRACTION THROUGH EXTRUSION OF SULPHUR AND PHOTOCHEMICAL CYCLISATION
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Ring contraction of 7-substituted 2-phenyl-4H-pyridazinothiadiazin-8(7H)-ones (5a-d) to 5-substituted 3-phenyl-1H-pyrazolopyridazin-4(5H)-ones (7a-d), through base-induced extrusion of sulphur, is described.Similar reactions proceed, not only on the 4-acetyl derivatives (4a-d) in basic media, but on 5a and the 4-methyl derivative (6a) thermally.Probable mechanism of these reactions are discussed.A comparable approach to the ring contraction, photochemical cyclisation of 2-substituted 5-(1-alkyl-2-benzylidenehydrazino)-4-chloro-3(2H)-pyridazinones (9a-e) to the corresponding 1-alkylpyrazolo-pyridazinone derivatives (8a-e) is also performed.
- Kaji, Kenji,Nagashima, Hiromu,Ohta, Yusho,Nagao, Sigeto,Hirose, Yoshihiko,Oda, Hirohisa
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p. 479 - 484
(2007/10/02)
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