Synthesis of Diverse γ-Lactams via Rh-Catalyzed C(sp2)-H Addition to Aliphatic Nitriles

Intermolecular 1,2-Difunctionalization of Nitriles via Redox Gold Catalysis: Synthesis of Benzoxazoles and Benzimidazoles

The unprecedent gold-catalyzed intermolecular 1,2-difunctionalization of nitriles with o-iodophenols or o-iodoanilines via Au(I)/Au(III) redox catalysis has been developed, providing an expedient route to the synthesis of benzoxazoles or benzimidazoles with broad substrate scope and high functional compatibility. Mechanistic investigation reveals that the Au(III)-Ar species generated via oxidative addition of o-iodophenol to MeDalphosAu+, serves as a key intermediate. Particularly, this annulation is initiated by oxidative addition, rather than the nucleophilic attack of the phenol moiety in o-iodophenol towards the nitrile. The method was also applied to the synthesis of poly aza-heterocycles via a cascade Au(I)/Au(III) and Au(I) catalysis relay.

Access to 2,3-Dihydropyridines Involving Cyano Transformation Relay through Gold Catalysis Assisted by a Lewis Acid

A gold(I)-catalyzed cyclization of enynone-nitriles with amines to 2,3-DHPs assisted by La(OTf)3 has been developed. The compatibility with abundant nucleophiles, high functional group tolerance, rapid assembly of molecular complexity, and late-stage functionalization of bioactive substances make this approach attractive for the construction of 2,3-DHPs, which have rarely been synthesized in the literature. The reaction proceeds via cascade cyclization involving gold/Lewis acid cooperative activation of the alkene and the cyano moiety.

Rh(III)-Catalyzed C-H Activation/Annulation for the Construction of Quinolizinones and Indolizines

A catalytic-condition-controlled synthesis strategy was reported to build quinolizinone and indolizine derivatives from the easily available enamide and triazole substrates with high regioselectivity and good functional group tolerance. More especially, this transformation has successfully fulfilled a C-H bond activation of terminal olefin from enamides followed by a [3 + 3] and a [2 + 3] cyclization cascade under different catalytic conditions, respectively, to provide two kinds of potentially biologically active heterocyclic scaffolds with a ring-junction nitrogen atom. Mechanistically, the methoxyamine formyl group serves as either a traceless directing group (DG) or an oxidizing DG via the C-N and C-C cleavage in this protocol.

Construction of Functionalized α-Imino Ketones via Pd-Catalyzed C-H Addition to Nitriles/Aerobic Oxidation Sequences

Pd(II)-catalyzed addition of sp2 C-H to nitrile/aerobic oxidation sequences for the preparation of functionalized α-imino ketones is described in which readily available heteroarenes and O-acyl cyanohydrins were employed. Various functionalized targeted molecules can be prepared in good yields with high atom and step economy. Moreover, a broad substrate scope and the ready manipulation and availability of the reaction partners enable this protocol to be appealing to explore the chemical space of the construction of functionalized α-imino ketones with high efficiency.

Recent Advances in Alkenyl sp2 C-H and C-F Bond Functionalizations: Scope, Mechanism, and Applications

Alkenes and their derivatives are featured widely in a variety of natural products, pharmaceuticals, and advanced materials. Significant efforts have been made toward the development of new and practical methods to access this important class of compounds by selectively activating the alkenyl C(sp²)-H bonds in recent years. In this comprehensive review, we describe the state-of-the-art strategies for the direct functionalization of alkenyl sp² C-H and C-F bonds until June 2022. Moreover, metal-free, photoredox, and electrochemical strategies are also covered. For clarity, this review has been divided into two parts; the first part focuses on currently available alkenyl sp² C-H functionalization methods using different alkene derivatives as the starting materials, and the second part describes the alkenyl sp² C-F bond functionalization using easily accessible gem-difluoroalkenes as the starting material. This review includes the scope, limitations, mechanistic studies, stereoselective control (using directing groups as well as metal-migration strategies), and their applications to complex molecule synthesis where appropriate. Overall, this comprehensive review aims to document the considerable advancements, current status, and emerging work by critically summarizing the contributions of researchers working in this fascinating area and is expected to stimulate novel, innovative, and broadly applicable strategies for alkenyl sp² C-H and C-F bond functionalizations in the coming years.

The Renaissance of Organo Nitriles in Organic Synthesis

In the arena of functional group-oriented organic synthesis, the nitrile or cyano functionality is of immense importance. The presence of nucleophilic N -atom, π-coordinating ability of the triple bond, and electrophilic C-center imparts unique and interesting reactivity. Owing to the ability of the nitrile to transform into various other functional groups or intermediates, the chemistry is very rich and diverse. In particular, the involvement of nitrile in numerous organic reactions such as inter- or intramolecular alkyne insertion, [2 + 2 + 2] cycloaddition with alkynes, [3 + 2] cycloaddition with azides, [4 + 2] cycloaddition with diene allow the synthesis of many important carbocycles and heterocycles. Furthermore, the nitrile serves as a directing group in many C-H bond functionalization reactions to introduce diverse functionality and participate as a radical acceptor in radical cascade strategies to obtain a large variety of functional molecules. This review mainly focuses on the reactivity and diverse synthetic application of the nitrile including C-H bond functionalization, alkyne insertion, cycloaddition, and thermal or photochemical cascade strategy. The objective of the current review aims at bringing out the striking collection of various nitrile-triggered organic transformations.