Base-Catalyzed One-Pot Synthesis of 2,3,6-Substituted Pyridines

A three-component reaction catalyzed by base was established, which mainly consisted of ynals, isocyanates, amines and alcohols. This strategy provides a wide range of substrates and represents a simple process for the preparation of different pyridine derivatives in good yields with high regioselectivities.

Csp3-H Imination Using Arylazo Sulfone as a N Source: An Approach to Access Imines

An unprecedented Csp3-H imination reaction using arylazo sulfones as the readily accessible and stable N source is reported. The synthetic virtues are demonstrated through mild conditions, simple operation, good air compatibility, and functional group tolerance, as well as suitability for gram-scale reaction. The resulting imines can be further converted to α-amino acids. The presented results shed light on an unusual usage of arylazo sulfones and will inspire novel experimental design by using arylazo sulfones as the N source.

A Novel Method to Construct 2-Aminobenzofurans via [4 + 1] Cycloaddition Reaction of In Situ Generated Ortho-Quinone Methides with Isocyanides

A new approach for the synthesis of 2-aminobenzofurans has been described via Sc(OTf)₃ mediated formal cycloaddition of isocyanides with the in situ generated ortho-quinone methides (o-QMs) from o-hydroxybenzhydryl alcohol. Notably, as a class of readily available and highly active intermediates, o-QMs were first used in the construction of benzofurans. This [4 + 1] cycloaddition reaction provides a straightforward and efficient methodology for the construction of 2-aminobenzofurans scaffold in good yield (up to 93% yield) under mild conditions.

Cascade reaction of o-enoyl arylisocyanide and o-hydroxy aromatic aldimine: diastereoselective access to a polycyclic spirobenzoxazine chromeno[4,3-b]pyrrole derivative

A series of structurally unusual spirobenzoxazine chromeno[4,3-b]pyrrole derivatives have been efficiently constructed in a single operation from readily available starting materials. This domino transformation forms successively three new rings and provides a fast and economic strategy with excellent diastereoselectivity.

Catalytic Metal-Enabled Romance of Isocyanides for Use as “C1N1” Synthons in Cyclization: Beyond Radical Chemistry

Cyclizative reactions have attracted considerable attentions in organic synthesis with regard to the high atom economy and synthetic efficiency towards cyclic architectures. Especially, isocyanide-based cyclizations have proven to be a...

Hypothesis-Driven Palladium-Catalyzed Transformations for the Construction of New Molecular Architectures

The development of new synthetic protocols to access diverse molecular scaffolds from readily available starting compounds is of significance in both academia and industry. Towards this, the catalysis by transition metals has been employed as a powerful tool to access molecules with broad structural and functional diversity. An overview of the recent literature manifested the tremendous potential of transition metal-catalyzed processes in advancing organic synthesis in a new direction. This account compiles new conceptual advancements in the palladium-catalyzed Alder-ene type cycloisomerization reactions, C-H functionalizations, and one-pot multicatalytic processes, which have become essential tools to access new classes of molecules.

Nickel-promoted oxidative domino Csp3-H/N-H bond double-isocyanide insertion reaction to construct pyrrolin-2-ones

The first nickel-catalyzed oxidative domino C_sp3-H/N-H double isocyanide insertion reaction of acetamides with isocyanides has been developed for the synthesis of pyrrolin-2-one derivatives. A wide range of acetamides bearing various functional groups are compatible with this reaction system by utilizing Ni(acac)₂ as a catalyst. In this transformation, isocyanide could serve as a C1 connector and insert into the inactive C_sp3-H bond, representing an effective way to construct heterocycles.

Palladium-Catalyzed Imidoylation-Triggered [2 + 2 + 1] Cyclization of Internal Alkyne with Isocyanides

In this work, a palladium-catalyzed [2 + 2 + 1] cyclization of internal alkynes with double isocyanides is described. This facile procedure is efficient for synthesizing various pyrrolo[3,2-c]quinolin-2-amines. The reaction worked well with a broad reaction scope. In the process, it is believed that sequential double isocyanide insertion, 6-exo-dig cyclization of alkyne, and addition of an imino group are involved.

Palladium-Catalyzed Cycloaddition of Alkynylimines, Double Isocyanides, and H2O/KOAc

In this work, a palladium-catalyzed cyclization of alkynylimines and double isocyanides is described. This facile procedure is efficient for synthesizing various 4-amidyl-2-aminopyrroles. Mechanism investigation indicates that a four-membered ring-fused pyrrole species is a key intermediate and the reaction involves [4 + 1] cycloaddition, protonation, nucleophilic addition, 1,4-addition of isocyanide, and rearomatization. Interestingly, the linear dipyrrole derivative is found to be an appropriate fluoride ion probe with a remarkable emission change, which could serve as a potential candidate for optoelectronic conjugated materials.

Insights into C–O insertion in a carbene/alkyne metathesis cascade reaction catalyzed by Rh2(OAc)4: a DFT study

The mechanism and selectivities of C–O insertion in the carbene/alkyne metathesis of diazo compounds catalyzed by Rh₂(OAc)₄ are studied with DFT calculations.

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.

A One-Pot Synthesis of Oxazepine-Quinazolinone bis-Heterocyclic Scaffolds via Isocyanide-Based Three-Component Reactions

A novel, efficient and environmentally friendly approach has been developed for the synthesis of biologically important bis-heterocyclic oxazepine-quinazolinone derivatives. The structurally interesting compounds of high purity were synthesized by a one-pot three-component reaction of 2-(2-formylphenoxy) acetic acid and 2-aminobenzamide as bifunctional reagents and an isocyanide without using any catalyst, with excellent overall yields.

A silver(i)-catalyzed cascade bicyclization strategy for synthesis of 5H-benzo[d]tetrazolo[5,1-b][1,3]thiazines

A simple and efficient protocol for silver(i)-catalyzed tandem reaction of o-alkynylphenyl isothiocyanates with sodium azide has been developed, affording a series of 5H-benzo[d]tetrazolo[5,1-b][1,3]thiazines in moderate to good yields. In this transformation, a [3 + 2] cycloaddition reaction mechanism was involved and two new rings were formed in one pot.

Synergistic silver/scandium catalytic spiroketalization of β-alkynyl ketones for the atom economical synthesis of skeletally diverse spirocyclic isochromenes

Two types of new synergistic silver/scandium catalytic spiroketalizations of β-alkynyl ketones have been achieved, delivering a variety of skeletally diverse spirocyclic isochromenes in generally good yields.

A bicyclization reaction with two molecular allenyl ketones and isocyanides: synthesis of a lactone-containing azaspirocycle derivative

A novel bicyclization reaction of two molecular allenyl ketones and isocyanides has been disclosed. This strategy allows for the construction of structurally complex spirocyclic lactam–lactone systems in an efficient manner.

Hetero-bimetallic cooperative catalysis for the synthesis of heteroarenes

Review covering the synthesis of 5- and 6-membered as well as condensed heteroarenes, focussing on the combinations in cooperative catalytic systems in strategies used to achieve selectivity and also highlights the mode of action for the cooperative catalysis leading to the synthesis of commercially and biologically relevant heteroarenes.

A formal (5+1) annulation reaction from heterodimerization of two different isocyanides: stereoselective synthesis of 2H-benzo[b][1,4]oxazin-2-one

A novel (5+1) annulation reaction of functionalized 2-isocyanophenyloxyacrylate and aromatic, aliphatic isocyanides has been disclosed. This strategy allows for a quick access to many 2H-benzo[b][1,4]oxazin-2-one derivatives.

Regioselective synthesis of polycyclic sulfones via radical-induced three-component bicyclization cascades

New radical-triggered three-component bicyclization cascades of 2-alkynylaryldiazonium tetrafluoroborates with a sulfur dioxide surrogate DABCO·(SO₂)₂ and internal alkynes have been reported for the first time, leading to 49 examples of polycyclic sulfones with moderate to good yields.

Nickle Catalysis Enables Access to Thiazolidines from Thioureas via Oxidative Double Isocyanide Insertion Reactions

An efficient synthesis of thiazolidine-2,4,5-triimine derivatives was developed via Ni-catalyzed oxidative double isocyanide insertion to thioureas under air conditions, in which thioureas play three roles as a substrate, a ligand, and overcoming isocyanide polymerization. The reaction is featured by employing a low-cost and low loading Ni(acac)₂ catalyst, without any additives, and high atom economy. This is the first example to directly apply a Ni(II) catalyst in oxidative double isocyanide insertion reactions.

Palladium-catalyzed oxidative coupling of arylboronic acid with isocyanide to form aromatic carboxylic acids

A valuable palladium-catalyzed oxidative coupling of aryl- and alkenyl borides with isocyanide for the synthesis of corresponding carboxylic acids has been developed. With wide substrate scopes and good functional group tolerance, this reaction offers corresponding carboxylic acids in moderate to excellent yields.

Relay tricyclic Pd(ii)/Ag(i) catalysis: design of a four-component reaction driven by nitrene-transfer on isocyanide yields inhibitors of EGFR

A four-component reactions promoted by Pd(ii)/Ag(i) relay catalysis paved the way for the development of a new EGFR inhibitor.

Ytterbium and silver co-catalyzed synthesis of pyrrole-fused bicyclic skeletons from enynones and isocyanides

A cascade reaction of isocyanide and enynone using Yb/Ag cooperative catalysis provided a quick access to structurally complex pyrrole-fused heterocycles.

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.

Direct intramolecular amination of tryptophan esters to prepare pyrrolo[2,3-b]indoles

A metal-free iodine-catalyzed intramolecular amination has been developed for the practical synthesis of pyrrolo[2,3-b]indoles from readily available tryptophan esters. The transformation has been applied to a wide array of substrates and can be performed on gram scale under very mild conditions.

Direct carboxamidation of cyclic 2-diazo-1,3-diketones by Rh2(OAc)4-catalyzed isocyanide insertion–hydrolysis

A novel and efficient strategy for the synthesis of 2-hydroxy-6-oxocyclohex-1-enecarboxamides through a Rh₂(OAc)₄-catalyzed direct carboxamidation of cyclic 2-diazo-1,3-diketones has been developed.