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Recent Advances in Microwave-Assisted Synthesis of Heterocyclic Compounds

“…(47)) [300,301]. The use of microwave irradiation as an alternative energy source in this type of condensation reaction has allowed for higher yields, reduced reaction times, and improved reaction purity [302,303]. For example, reaction of o-phenyldiamine 198 with phenylacetic acid 201, in the presence of HCl under microwave irradiation gave the 2-substituted benzimidazole 202, after 8 min in 79% yield.…”

“…For example, reaction of o-phenyldiamine 198 with phenylacetic acid 201, in the presence of HCl under microwave irradiation gave the 2-substituted benzimidazole 202, after 8 min in 79% yield. In contrast, conventional heating gave 202 in 57% yield after 4 h [303]. Further improvements to this method eliminate strong acids by replacement of the carboxylic acid component with activated derivatives such as S-methylisothiamides hydroiodides or orthoesters.…”

Synthesis and Transformations of Heterocyclic Compounds under the Influence of Microwave Radiation. (Review)

“…With normal heating a comparable yield of the latter was obtained after 3 h [26]. The authors of [22] The heterocyclization of o-phenylenediamine and phenylacetic acid under analogous conditions was more successful, and the yield of the product 2-benzylbenzimidazole hydrochloride (19) after 7 min amounted to 79% [27]. The synthesis of indoles 20 by the decarboxylation of indole-2-carboxylic acid and its substituted derivatives was realized successfully in a closed microwave system.…”

Novel synthetic approach for 1,4-dihydroxyanthraquinone and the development of its lithiated salts as anode materials for aqueous rechargeable lithium-ion batteries

“…The synthetic route that we proposed is a novel method for the synthesis of quinizarin. It involves a combination of sonochemistry and a conventional thermal method, which is comparatively a better scheme than the microwave method 11 to obtain a high yield and high purity. The lithiation of quinizarin was carried out under an inert atmosphere.…”