The Literature of Heterocyclic Chemistry, Part X, 2005–2007

Metal-catalyzed reactions of organic nitriles and boronic acids to access diverse functionality

The nitrile or cyano (-CN) group is one of the most appreciated and effective functional groups in organic synthesis, having a polar unsaturated C-N triple bond. Despite sufficient stability and being intrinsically inert, the nitrile group can be easily transformed into many other functional groups, such as amines, carboxylic acids, ketones, etc. which makes it a vital group in organic synthesis. On the other hand, despite several boronic acids having a low level of genotoxicity, they have found wide applicability in the field of organic synthesis, especially in transition metal-catalyzed cross-coupling reactions. Recently, transition-metal-catalyzed cascade additions or addition/cyclization processes of boronic acids to the nitrile group open up exciting and useful strategies to prepare a variety of functional molecules through the formation of C-C, C-N and CO bonds. Boronic acids can be added to the cyano functionality through catalytic carbometallation or through a radical cascade process to provide newer pathways for the rapid construction of various important acyclic ketones or amides, carbamidines, carbocycles and N,O-heterocycles. The present review focuses on various transition-metal-catalyzed additions of boronic acids via carbometallation or radical cascade processes using the cyano group as an acceptor.

Catalyst-Free Synthesis of 2,4-Disubstituted-1H-imidazoles through [3 + 2] Cyclization of Vinyl Azides with Amidines

A facile and efficient route for the synthesis of 2,4-disubstituted imidazoles from benzimidamides and vinyl azides through [3 + 2] cyclization under catalyst-free conditions has been described. The method is compatible for a broad range of functional groups with good to excellent yields.

Synthesis of 2,3-dihydroquinazolinones and quinazolin-4(3H)-ones catalyzed by graphene oxide nanosheets in an aqueous medium: “on-water” synthesis accompanied by carbocatalysis and selective C–C bond cleavage

Graphene oxide nanosheet catalyzed strategies for construction of 2,3-dihydroquinazolinones and quinazolin-4(3H)-ones starting from anthranilamide and an aldehyde/ketone in aqueous medium at room temperature have been realized.