Pyrazoles indazoles

Pyrazoles, Indazoles, and their Derivatives as Starting Materials for the Syntheses of Fused Ring Systems... 

The synthesis of pyrazoles, indazoles and their derivatives generally follows classical methods, the two most important methods for practical purposes being the reaction between hydrazines and /3-difunctional compounds, and 1,3-dipolar cycloadditions (Section 4.04.3.1.2). Both procedures are well documented (64HC(20)l, 66AHC(6)327, 67HC(22)l) and thus the length of the sections in this part of the chapter reflects not only the number of publications dealing with a particular method but also its interest and novelty. 

Het = imidazoles, benzimidazole, pyrazoles, indazole triazole, pyrrole, indole... 

From a qualitative viewpoint there is no doubt that the compounds classified as aromatic in Section 4.04.1.1 (pyrazoles, indazoles, isoindazoles, pyrazolones, indazolones, mesoionic derivatives) indeed have aromatic properties to a greater or lesser extent. Dihy-drobenz[cd]indazole (115) is also formally an aromatic compound since it has an odd number of electron pairs (n =7). However, due to the presence of two adjacent nitrogen atoms the aromatic tautomer (115a) is not stable, and the compound exists as the 1,5- or 1,3-dihydro tautomers (115b) or (115c) <72JCS(P2)68). The antiaromatic benz[cd]indazole (116), although unstable, has been fully characterized by N, H and NMR spectroscopy... 

PYRAZOLES, INDAZOLES, AND THEIR DERIVATIVES AS STARTING MATERIALS FOR THE SYNTHESES OF FUSED RING SYSTEMS... 

The conformation about the C-N bonds of 16 was modified by coordination with Ru-bipyridyl (07POL4373). When there is an ortho-nitro group adjacent to an azole with an N atom at position 2 (pyrazoles, indazoles, triazoles, and tetrazoles) the preferred conformation has the nitro group close to the N atom (48, X = Y = Z = CH, = H, see also 26) this is the... 

HetN-H = indoles, pyrroles, pyrazoles, indazoles, triazoles, imidizaloes, or benzimidazoles... 

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