Five‐Membered Heterocycles: 1,2‐Azoles. Part 1. Pyrazoles

Transition‐Metal‐Free N‐Arylation of Pyrazoles with Diaryliodonium Salts

“…N-Arylatedp yrazoles are important molecular motifs for biologicallya ctive compounds used in the field of agrochemistry and pharmaceutical science. [1] N-Arylpyrazoles can be prepared by cyclization of substituted N-arylhydrazines with 1,3-difunctionalized compounds, [2] but the limited accesso f arylhydrazines restricts the variability of the desired heterocycles. N-Arylpyrazoles can be preparedb yN-arylationo f 1H-pyrazoles under metal-free conditions through nucleophilic aromatic substitution [3] or in transition-metal-catalyzed couplings.…”

“…on the a-arylation of enolates with iodonium salts, [15] we envisionedt hat the N-arylation of pyrazoles could be achieved with diaryliodonium salts in the presence of weakb ases under mild conditions. In thea rylation of enolates, it was found that the [2,3] rearrangement pathway is energetically more favorable than the [1,2] elimination. In light of these results, we supposed that the neighboring effect of adjacentn itrogen atom could facilitatet he reaction.…”

“…In light of these results, we supposed that the neighboring effect of adjacentn itrogen atom could facilitatet he reaction. First, the coordination of the iodonium salt to pyrazole nitrogen should make the pyrazole more acidic and the intermediate T-shaped N-iodo species can undergo reductivee limination via [2,2] rearrangement, which should be more favorable than the [1,2] alternative (Scheme 1). [16] When unsymmetrical diaryliodonium salts react with nucleophiles, chemoselectivity is highly important.T he reactions are governed by electronic and steric factors, but the type of nucleophile (N, O, C) also plays an important role in determining the outcome of the reaction.…”

A synthetic cannabinoid FDU-NNEI, two 2H-indazole isomers of synthetic cannabinoids AB-CHMINACA and NNEI indazole analog (MN-18), a phenethylamine derivative N–OH-EDMA, and a cathinone derivative dimethoxy-α-PHP, newly identified in illegal products

“…However, their shifts of compound 3 were similar to those of 2-methyl-2 H -indazole [ N -1′ (δ N −91.2) and N -2′ (δ N −161.0)] (Table 3 ; Fig. 1 c) [ 14 ]. Therefore, the structure of compound 3 was determined as AB-CHMINACA 2 H -indazole analog [ N -(1-amino-3-methyl-1-oxobutan-2-yl)-2-(cyclohexylmethyl)-2 H -indazole-3-carboxamide] (Fig.…”

A theoretical study of the mechanism of oxidation of 1H-pyrazolines to 1H-pyrazoles by molecular bromine

“…We have published papers concerning the NMR properties of 2-pyrazolines, 1 H, 18-20 13 C, 21,22 and 15 N. 23 Results from other authors can be found in references 4,24,25 . Also the geometries of these five-membered heterocycles related to the envelope of cyclopentane have been discussed and compared with crystallographic data from the CSD.…”