Reactions of Carbon Substituents

8 Reactivity of Substituents Attached to Ring Nitrogen Atoms 9.01.8.1 Reactions of Carbon Substituents 

6-Disubstituted-2-methyl-1,2,3-triazinium iodides 114a-c are demethylated to the triazines 17m,s,u by reaction with formamide and diammonium persulfate (Equation 92) 1991H(32)2015 . This special case has already been mentioned in Section 9.01.5.6 together with the removal of 2-dicyanomethylene groups from the 1,2,3-triazinium dicyanomethylides 34 (R = H R, R = Me, Et, Ph) under the same conditions see also 1996CHEC-11(6)483 . Cycloadditions of 2-ethyl-1,2,3-triazinium tetrafluoroborates and 1,2,3-triazinium 2-dicyanomethylides have been treated in Section 9.01.5.7. 

Hydrolysis of 2-(l-chloroethoxycarbonyl)-2,5-dihydro-l,2,3-triazine 118b in MeCN/H20 (1 1) at 60°C readily affords the corresponding 2-deacylated-2,5-dihydrotriazine 21g (90%) 1996J(P1)2511 . 

For the rearrangement of 3-substituted-3,4-dihydro-l,2,3-benzotriazin-4-imines 54 (R3 = Bn, Ar) to the isomeric 4-benzyl- (or aryl-) amino-1,2,3-benzotriazines 36, see Section 9.01.4.4. A substituent shift from N-2 to N-3 in 2-methyl- (2-aryl-) l,2,3-benzotriazin-2-ium-4-olates to give the 3-methyl- (3-aryl-) 3,4-dihydro-1,2,3-benzotriazin-4-ones by irradiation in acetonitrile has been reviewed previously 1984CHEC(3)369 . 

Reduction by lithium aluminium hydride (LAH) or addition of phenylmagnesium bromide transforms the aroyl groups in 3-aroyl-3,4-dihydro-l,2,3-benzotriazin -ones 93b and 93c into more hydrolyzable 3-(1-hydroxy-1-arylalkyl) groups. Accordingly, the parent benzotriazinone 3 is reached in both cases prior to or during aqueous workup 1%OJOC1501 . 

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