Palladium-catalyzed intramolecular C(sp(2))-H imidoylation for the synthesis of six-membered N-heterocycles

Catalyst-free synthesis of phenanthridines via electrochemical coupling of 2-isocyanobiphenyls and amines

One pot metal-free synthesis of phenanthridines and amides under electrochemical conditions.

Advances in palladium-catalysed imidoylative cyclization of functionalized isocyanides for the construction of N-heterocycles

Palladium-catalysed isocyanide insertion reactions have witnessed great progress in recent years. In particular, imidoylative cyclization of functionalized isocyanides was successfully developed by taking advantage of the adjustable substituents on the isocyano group, opening a new avenue to access a variety of nitrogen-containing heterocycles. In this review article, we summarize the advances of functionalized isocyanide insertion reactions and highlight the breakthroughs of enantioselective palladium catalysed imidoylation reactions by using this strategy. Additionally, copper-catalysed cyclization reactions of functionalized isocyanides are briefly discussed.

C(sp3)–H functionalization with isocyanides

This review highlights the state-of-the-art advances in C(sp³)–H functionalization involving isocyanides through the synergistic combination of isocyanide insertion and C(sp³)–H bond activation.

Recent Advances in Palladium-Catalyzed Isocyanide Insertions

Isocyanides have long been known as versatile chemical reagents in organic synthesis. Their ambivalent nature also allows them to function as a CO-substitute in palladium-catalyzed cross couplings. Over the past decades, isocyanides have emerged as practical and versatile C1 building blocks, whose inherent N-substitution allows for the rapid incorporation of nitrogeneous fragments in a wide variety of products. Recent developments in palladium catalyzed isocyanide insertion reactions have significantly expanded the scope and applicability of these imidoylative cross-couplings. This review highlights the advances made in this field over the past eight years.

Palladium-catalysed dearomative aryl/cycloimidoylation of indoles

The first example of a dearomative palladium-catalysed isocyanide insertion reaction has been developed using functionalized isocyanides as the reaction partner of N-(2-bromobenzoyl)indoles. The imidoyl-palladium intermediate generated by tandem indole double bond/isocyanide insertion reactions could be trapped by intramolecular functional groups such as the C(sp2)-H bond and alkenes, affording diversified indoline derivatives bearing C3 imine-containing heterocycles. The dearomative aryl/cycloimidoylation of indoles proceeded smoothly in good to excellent yields with a wide functional group tolerance.

Catalytic formation of N3-substituted quinazoline-2,4(1H,3H)-diones by Pd(ii)EN@GO composite and its mechanistic investigations through DFT calculations

Modified GO based palladium composite was synthesized for catalytic synthesis of N3-substituted ouinazoline-2,4(1H,3H)-diones and the mechanistic route was theoretically investigated.

Thio radical-induced denitrogenative annulation of 1-azido-2-isocyanoarenes to construct 2-thiolated benzimidazoles

A method for the synthesis of 2-thiolated benzimidazoles is described starting from thiols and 1-azido-2-isocyanoarenes. The isocyano group works as an acceptor of various thio radicals, followed by denitrogenative annulation of the resulting imidoyl radical intermediates to the azido group, with nitrogen loss as the only process involving high bond-forming efficiency. The one-pot method for the synthesis of these products with high functional group tolerance in the benzimidazole-based ring is not available in previous literature.

Pd-Catalyzed C(sp2)-H Imidoylative Annulation: A General Approach To Construct Dibenzoox(di)azepines

A general method to construct the scaffolds of dibenzooxazepine and dibenzodiazepine, through Pd-catalyzed isocyanide insertion and intramolecular C(sp²)-H activation, has been developed. This is the first example of seven-membered heterocycle formation by C-H imidoylative annulation.

Cascade double isocyanide insertion and C-N coupling of 2-iodo-2'-isocyano-1,1'-biphenyls

A palladium-catalyzed double isocyanide insertion using 2-iodo-2'-isocyano-1,1'-biphenyls followed by copper-catalyzed intramolecular C-N coupling, delivering a unique heterocyclic structure containing both phenanthridine and carbazole scaffolds, has been developed. In this cascade process, four chemical bonds, including two C-C, one C-O, and one C-N bonds are formed consecutively without isolating an intermediate. The strategy of using a functionalized isocyanide in double insertion provides a quick approach for constructing heterocyclic systems with high bond-forming efficiency.

Access to 1-amino-3,4-dihydroisoquinolines via palladium-catalyzed C–H bond aminoimidoylation reaction from functionalized isocyanides

Efficient and practice access to 1-amino-3,4-dihydroisoquinolines, through palladium-catalyzed intramolecular C–H bond aminoimidoylation of α-benzyl-α-isocyanoacetates, has been developed.

Copper-catalyzed cyclization of 2-cyanobenzaldehydes and 2-isocyanoacetates: an efficient strategy for the synthesis of substituted 1-aminoisoquinolines

An efficient strategy for the synthesis of substituted 1-aminoisoquinoline has been developed.

Palladium-catalysed stereoselective synthesis of 4-(diarylmethylidene)-3,4-dihydroisoquinolin-1(2H)-ones: expedient access to 4-substituted isoquinolin-1(2H)-ones and isoquinolines

Palladium-catalysed stereoselective synthesis of 4-(diarylmethylidene)-3,4-dihydroisoquinolin-1(2H)-ones and their straightforward transformations to 4-substituted isoquinolin-1(2H)-ones and isoquinolines are described.

Palladium-Catalyzed Incorporation of Two C1 Building Blocks: The Reaction of Atmospheric CO2 and Isocyanides with 2-Iodoanilines Leading to the Synthesis of Quinazoline-2,4(1H,3H)-diones

A Pd-catalyzed insertion and cycloaddition of CO₂ and isocyanide into 2-iodoanilines under atmospheric pressure has been developed and affords quinazoline-2,4(1H,3H)-diones through the formation of new C-C, C-O, and C-N bonds under mild conditions. This reaction provides a new and practical method not only for the construction of quinazoline-2,4(1H,3H)-diones but also for the efficient utilization of carbon dioxide.

Palladium-catalyzed β-selective C(sp2)–H carboxamidation of enamides by isocyanide insertion: synthesis of N-acyl enamine amides

An efficient synthesis of N-acyl enamine amides via palladium-catalyzed alkene C–H activation and isocyanide insertion has been developed.

Silver-mediated oxidative C–H difluoromethylation of phenanthridines and 1,10-phenanthrolines

An efficient silver-mediated oxidative C–H difluoromethylation of phenanthridines and 1,10-phenanthrolines with TMSCF₂H was developed.

I2/CHP mediated [1 + 1 + 1 + 1] cyclization of aromatic isocyanides with amines to construct 1,3-diazetidine-2,4-diimine derivatives

An I₂/CHP (cumene hydroperoxide) mediated [1 + 1 + 1 + 1] cyclization of aromatic isocyanides with readily accessible amines via the formation of 4 new C–N bonds has been developed to construct unsymmetric 1,3-diazetidine-2,4-diimine derivatives under mild conditions.

Palladium-catalyzed C(sp2)–H aminoimidoylation of isocyano-containing arenes: synthesis of amino substituted N-heterocycles

An efficient access to amino substituted phenanthridine and isoquinoline derivatives, through palladium-catalyzed C(sp²)–H aminoimidoylation, has been developed.

Visible-light-mediated radical insertion/cyclization cascade reaction: synthesis of phenanthridines and isoquinolines from isocyanides

The development of a visible-light promoted radical insertion/cyclization cascade reaction to generate phenanthridines and isoquinolines from isocyanides under mild reaction conditions is reported.

A one-pot synthesis of [1,2,3]triazolo[1,5-a]quinoxalines from 1-azido-2-isocyanoarenes with high bond-forming efficiency

An efficient approach to prepare 1,2,3-triazolo[1,5-a]quinoxaline scaffolds, starting from 1-azido-2-isocyanoarenes and terminal acetylenes or substituted acetaldehydes, has been developed.

Metal-catalyzed C–H functionalization involving isocyanides

This review demonstrates the metal-catalyzed incorporation of isocyanides into C–H functionalization to establish complicated reactions utilizing synergistic effects.

Palladium-Catalyzed Synthesis of α-Iminonitriles from Aryl Halides via Isocyanide Double Insertion Reaction

An efficient one-pot synthesis of α-iminonitriles from readily available aryl halides via palladium-catalyzed double isocyanide insertion and elimination has been developed, without using various hypertoxic cyanides and excess oxidants. Furthermore, the utility of this reaction was demonstrated by the rapid total synthesis of quinoxaline and the reaction of functional groups exchanged with aryl halides.