Ultrasound-assisted synthesis of highly functionalized benzo[1,3]thiazine via Cu-catalyzed intramolecular CH activation reaction from isocyanides, aniline-benzoyl(acetyl) isothiocyanate adduct

First-row transition metal for isocyanide-involving multicomponent reactions (IMCR)

First-row transition metal catalyzed transformations that are able to construct complex molecules from simple, readily obtainable feedstocks have become a keystone of modern synthetic organic chemistry. Particularly, the multicomponent reaction (MCR) involving carbon-carbon (C-C) as well as carbon-heteroatom (C-X) bond formation plays an essential role in many chemical conversions, and insurgencies in these reactions powerfully improve the overall synthetic efficiency. Recently, MCRs emerges rapidly because of its greener sides like eco-friendly nature, swift and straightforward execution, high atom/step economy, and construction of aimed product with lowest or no by-product, usually in quantitative yield. Curiously, the exceptional divalent carbon atoms of isocyanides make them predominantly useful components in multicomponent reactions. As a result of widespread research over the past few decades, numerous well-designed and effective procedures for the first-row TM-catalyzed MCR to afford the various entities have been reported. These aspects are summarized in this review article. A particular focus on comparative discussion of various first-row transition-metal catalyzed isocyanide-based multicomponent reactions through mechanistic details included in the review article.

Copper-Catalyzed Ultrasonic-Promoted Coupling of Acetylene Analogs, Dialkyl azo dicarboxylate, and Benzazoles to Assemble Tricyclic Fused- Ring [1,2,3]triazolo[3,4-b][1,3]benzazole Analogs

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An unprecedented copper-catalyzed reaction of acetylene analogs with dialkyl azo dicarboxylate and benzazole analogs via a cross-coupling sequence was reported. A library of triazolobenzazole fused ring systems including [1,2,3] triazolo [3,4-b] [1,3] benzothiazole, [1,2,3] triazolo [3,4-b] [1,3] benzoxazole and [1,2,3] triazolo[3,4-b][1,3]benzimidazole structures were obtained in moderate to excellent yields under very mild reaction conditions. Structural confirmation of the final products became possible using different methods like spectroscopy and elemental analysis. The control experiments indicated C-H activation of acetylene by copper salts, followed by cycloaddition between a 2-(phenylethynyl)benzo[d]azol-3(2H)-yl anion and azo dicarboxylate as the key mechanistic feature. The broad substrate scope with simple and easily affordable starting materials, as well as mild reaction conditions are the noticeable attributes of this methodology, which provides facile access to the desired products.