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Ring Transformation of 3,1-Benzothiazin-2,4-dithiones with Carboxylic Acid Hydrazides to Substituted 1,3,4-Thiadiazoles or in the Presence of Hydroxid Ions to 3-Acylamino-quinazolin-2,4-dithiones
Leistner, Siegfried,Hentschel, Karin,Wagner, Guenther
, p. 915 - 922 (2007/10/02)
The substituted 1,3,4-thiadiazoles 4-14 were prepared in one step by reaction of 3,1 benzothiazin-2,4-dithiones 1 and 3 with RCONHNH2 (R=Me, Ph, substituted Ph, 4-Pyridyl, CONHNH2).Reaction of 1 with RCONHNH2 in the presence of HO(-) leads to substituted quinazolin-2,4-dithiones 18-20.Under the action of CS2 the yield of 19 and 20 increases.Possible reaction mechanisms are discussed. - keywords: 2H-3,1-Benzothiazin-2,4(1H)-dithione; Carbocyclic acid hydrazides; Quinazolin-2,4(1H,3H)-dithione; Ring transformation; 1,3,4-Thiadiazoles
COMPOSES SULFURES HETEROCYCLIQUES. XCVI. REACTION DE L'HYDRAZINE SUR LES DIHYDRO-1,2 BENZOTHIAZINE-3,1 THIONES-4
Legrand, Louis,Lozac'H, Noel
, p. 139 - 143 (2007/10/02)
1-Alkyl-1,2-dihydro-3,1-benzothiazine-4-thiones 1, when reacting with hydrazine, give with a good yield a 1-alkyl-3-amino-2,3-dihydro-1H-quinazoline-4-thione-2, often together with a derivative of 1,3,4-thiadiazole-3. With 1-aryl-1,2-dihydro-3,1-benzothiazine-4-thiones, the main product of the reaction with hydrazine appears to be a 1-aryl-4-hydrazono-1,4-dihydro-2H-3,1-benzothiazine 4, sometimes with some amount of 3.On the contrary, when reacting with hydrazine, 1-alkyl (or 1-aryl)-1,2-dihydro-3,1-benzothiazin-4-ones lead to a 2-alkylamino (or arylamino)-benzohydrazide 5. By thermolysis 4 isomerizes into 2 which is accompanied by derivatives (3 and 7) of 1,3,4-thiadiazole.The structures of compounds 2, 4 and 7 have been studied by NMR and UV spectrometry.
