Silver(I) salts as useful reagents in pyrazole synthesis

Abstract

This account provides a survey on the synthesis of a huge variety of pyrazole-containing molecules by 1,3-dipolar cycloadditions promoted by silver(I) salts. The data on this subject are listed in a systematic way according to the type of the cycloaddition involved, with an emphasis to improvements with respect to reactions performed in the presence of the usual organic basic agents.

Silver-Mediated Synthesis of Heterocycles

“…Stereoselective cycloadditions have also been carried out. A review has been recently published by the author . One recent example is shown below (Scheme ) .…”

“…A review has been recently published by the author. 172 One recent example is shown below (Scheme 85). 173 The β-lactamic hydrazonoyl chloride 309 gave the nitrilimine 310 under the influence of the silver ion.…”

Solid-Phase Synthesis of Amino Acid Derived N-Unsubstituted Pyrazoles via Sydnones

“…Huisgen’s 1,3-dipolar cycloaddition is a versatile method to synthesize five-membered nitrogen heterocycles . Recent synthesis of pyrazoles via 1,3-dipolar cycloaddition includes reactions of nitrile imines and alkynes or enamines, hydrazones and nitroolefins, diazo compounds and alkynes, and azomethine imines and alkynes . Sydnones are relatively stable mesoionic compounds that react as azomethine imine-type dipoles .…”

Theoretical analysis of the mechanism and regioselectivity of the 1, 3-dipolar cycloaddition of E-3-(dimethylamino)-1-(10H-phenothiazin-2-yl)prop-2-en-1-one with some nitrilimines using DFT and the distortion/interaction model

“…[5][6][7] The 1,3-DC reactions of nitrilimines with alkenes is an important method for preparing pyrazoles and pyrazolidines in a regioselective and stereoselective manner. 8 Experimentally; it has been found that the cycloaddition reactions of nitrilimines 1a-c with E-3-(dimethylamino)-1-(10H-phenothiazin-2-yl) prop-2-en-1-one 2 give preferentially the cycloadducts 3a, 3b and 3c respectively, shown in Scheme 1. 9 In continuation of our studies on the mechanism and regioselectivity of the1,3-DC reactions, [10][11][12][13][14][15][16][17][18] we became interested in the above mentioned reactions based on activation energy calculations, the distortion/interaction model and DFT-based reactivity indexes.…”