1- Aminopyrazole. oxidation rearrangement

The rearrangement of cyclopropenyl azides (396) is used for the synthesis of monocyclic 1,2,3-triazines (397) (73JOC3149, 79CB1514). However, the most general method is the oxidation of N-aminopyrazoles (398) with lead tetraacetate or variety of other oxidants (92AHC(53)85). 

The presence or absence of the dioxolane protecting group in dienes dictates whether they participate in normal or inverse-electron-demand Diels-Alder reactions.257 The intramolecular inverse-electron-demand Diels-Alder cycloaddition of 1,2,4-triazines tethered with imidazoles produce tetrahydro-l,5-naphthyridines following the loss of N2 and CH3CN.258 The inverse-electron-demand Diels-Alder reaction of 4,6-dinitrobenzofuroxan (137) with ethyl vinyl ether yields two diastereoisomeric dihydrooxazine /V-oxide adducts (138) and (139) together with a bis(dihydrooxazine A -oxide) product (140) in die presence of excess ethyl vinyl ether (Scheme 52).259 The inverse-electron-demand Diels-Alder reaction of 2,4,6-tris(ethoxycarbonyl)-l,3,5-triazine with 5-aminopyrazoles provides a one-step synthesis of pyrazolo[3,4-djpyrimidines.260 The intermolecular inverse-electron-demand Diels-Alder reactions of trialkyl l,2,4-triazine-4,5,6-tricarboxylates with protected 2-aminoimidazole produced li/-imidazo[4,5-c]pyridines and die rearranged 3//-pyrido[3,2-[Pg.460]

The rearrangement of azidoisoxazoles into 2-aminopyrazole 1-oxides is discussed in Section 2.1.7. No skeletal rearrangements of 2-substituted... 

The most used reaction of A -aminopyrazoles is their oxidation to 1,2,3-triazines <93LA367>. The mechanism of this reaction has been studied by Boulton <86JCS(P1)1249> using N labeling on the amino group one of the examples described is the rearrangement of l-amino-3-methoxyindazole into 4-methoxy-1,2,3-benzotriazine,... 

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