Silver‐Catalyzed Chemoselective [4+2] Annulation of Two Isocyanides: A General Route to Pyridone‐Fused Carbo‐ and Heterocycles

Abstract

A silver-catalyzed chemoselective [4+2] annulation of aryl and heteroaryl isocyanides with α-substituted isocyanoacetamides was developed for the facile and efficient synthesis of 2-aminoquinolones, naphthyridines, and phenanthrolines. A mechanism for this multistep domino reaction is proposed on the basis of a C-labeling experiment, according to which an unprecedented chemoselective heterodimerization of two different isocyanides generates an α-amidoketenimine intermediate, which undergoes 1,3-amino migration to form an α-imidoylketene, followed by 6 π electrocyclization.

Constructing Organometallic Architectures from Aminoalkylidyne Diiron Complexes

“…The use of trimethylsilylacetylide supplies the way to dimerization, presumably through the release of Me 3 SiC≡CSiMe 3 by contact with the alumina used for chromatographic purification (Scheme b). It should be mentioned here that the metal mediated assembly of isocyanide units is a topic of current great interest, pointing to the definition of convenient strategies to access novel nitrogen containing organic structures , …”

Highly efficient AgNO3‐catalyzed approach to 2‐(benzo[d]azol‐2‐yl)phenols from salicylaldehydes with 2‐aminothiophenol, 2‐aminophenol and benzene‐1,2‐diamine

“…Over the past decade, silver salt catalysts have significantly emerged to promote a broad range of organic transformations, such as cyclization, cycloaddition, allylation, tandem reactions, decarboxylation and other reactions owing to their efficiency, abundance, affordability and simple operation. Very recently, silver nitrate (AgNO 3 ) has attracted much attention as a promising alternative to traditional transition metal catalysts and has also been employed for organic reactions, such as phosphorylation, radical reactions, addition, domino reactions and others …”

Recent Organic Transformations with Silver Carbonate as a Key External Base and Oxidant

“…The retro-hetero-Michael addition ring-opens the 2-imidazoline (78-I) to give the imidamide intermediate, and then a cascade involving nucleophilic addition, proton transfer, and dehydration provides highly substituted pyrrole 80 as the product. In 2017, Xu and co-workers developed a silver-catalyzed chemoselective [4+2] annulation of aryl and heteroaryl isocyanides 72 with α-substituted isocyanoacetamides 81 to afford pyridone-fused carbo-and heterocycles 82 (Scheme 48) [64]. To determine the reaction mechanism, the reaction was performed with a 13 C labeled isocyanide group in 72, and the NMR spectrum showed the benzo[h]quinolone product 82 with 13 C at the 2-position.…”