1.2- Dihydro-l,2,4-benzotriazines

Benzotriazines. Reduction of 2-nitrophenylhydrazones 463 or similar hydrazides 466 gives 1,2-dihydro-l,2,4-benzotriazines 464 (Scheme 240). In most cases the initial dihydro compounds 464 are oxidized by air or potassium ferricyanide to the aromatic 1,2,4-benzotriazines 465 <1997J(P1)3107, 1999JHC589, CHEC-III (9.02.7.4)177>. 

V -(2-Aminophenyl)hydrazides are cyclized to 5 and oxidized to 1,2,4-benzotriazines 6 when treated with hydrochloric acid and sodium 3-nitrobenzenesulfonate.5,147 Similarly, A -(2-nitro-phenyl)hydrazides give 1,2-dihydro-l, 2,4-benzotriazines 5 when the nitro group is reduced with sodium amalgam in ethanol. In most cases, the initially formed dihydro compounds are not isolated, but are oxidized by potassium hexacyanoferrate(III) to the aromatic 1,2,4-benzotriazines 6.148 Reduction of the nitrohydrazones or the tautomeric azo compounds with zinc, catalytic hydrogenation,332 or elcctrochemically246 affords 1,2,4-benzotriazines 6.148 Electrochemical reduction of A"-(2-nitrophenyl)hydrazides yields 3-substituted 1,2,4-benzotriazines 6.140... 

Dihydro-l,2,4-benzotriazines are isolated from the reduction of 1,2,4-benzotriazines 4 with sodium dithionite346a,b or sodium borohydride.373 The products obtained by reduction of l,2,4-benzotriazine-3-carboxylates 4 (R1 = C02R2) were formulated as the 1,4-dihydro derivatives. Reduction of 1,2,4-benzotriazine A-oxides 5 affords 1,2,4-benzotriazines or dihydro-1, 2,4-benzotriazines, the product ratio depending on the conditions used346b 350a,b 374,375 (see Section 2.2.1.5.2.). 

Dimethylamino-(1.2-Dihydro-l, 2,4-benzotriazine) Diethyl Propyl Malonate 3-Dimethylamlno-1,2,4-benzotriazine Oxide Propyl Malonyl Chloride... 

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