Benzotriazines and 3,4-Dihydro-1,2,3-benzotriazin-4-ones

This class of compounds is made available predominantly by the four cyclization modes, C-C-C-N-N-N (b), N-C-C-C-N-N (c), N-C-C-C-N - -N (d), and C-C-C-N-N -l-N (e) (see Section 9.01.9), and recent applications have been shown in Equations (105) and (107)-(111). From these modes, the N-C-C-C-N - - N route is the most widely applied one, with Equation (110) representing an improvement insofar as a new diazotization agent is introduced. All reactions are easily performed and widely applicable, since the terminal N-atom becoming N-3 may be introduced as a carbamoyl, carbohydroxyamide, or carbohydrazide group, determining at the same time the N-3 substiuent. 

A new method was found to prepare 2,3,4,4a-tetrahydro-l,2,3-benzotriazines following the rare C-C-N-N-N-C mode (a). The azo link in l-(2,6-dimethylphenyl)-3,3-di(primary alkyl)triazenes activates the a-methylene groups at N-3 sufficiently to undergo lithiation and, at the same time, most likely complexes the Li-atom brought in by metalation with BuLi. The carbanionic carbon in turn attacks a phenyl carbon atom ortAo to N-1, which is novel, since otherwise functionalized carbon atoms such as CN or a carbonyl group at C-2 are attacked (Equation (102) Section 9.01.9). No predictions regarding a wider applicability, though, are possible at present. 

Introduction of N-2 in the N-C-C-C-N 4-N (d) mode by diazotization of a free NH2 group in 1,8-diaminonaphtha-lenes (one of the two amino groups may be alkylated or arylated) using a variety of diazotizing agents such as aqueous sodium nitrite in the presence of mineral or acetic acid, or NO -transfer reagents such as nitrosodiphenylamine, is a reliable and often applied method. 

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