Dearomative Spirocyclization of Tryptamine-Derived Isocyanides via Iron-Catalyzed Carbene Transfer

Tryptamine-derived isocyanides are valuable building blocks in the construction of spirocyclic indolenines and indolines via dearomatization of the indole moiety. We report the Bu4N[Fe(CO)3NO]-catalyzed carbene transfer of α-diazo esters to 3-(2-isocyanoethyl)indoles, leading to ketenimine intermediates that undergo spontaneous dearomative spirocyclization. The utility of this iron-catalyzed carbene transfer/spirocyclization cascade was demonstrated by its use as a key step in the formal total synthesis of monoterpenoid indole alkaloids (±)-aspidofractinine, (±)-limaspermidine, (±)-aspidospermidine, and (±)-17-demethoxy-N-acetylcylindrocarine.

1,2,3-Benzotriazine Synthesis by Heterocyclization of p-Tosylmethyl Isocyanide Derivatives

An efficient methodology to form 4-alkoxy- and 4-aryloxybenzo[d][1,2,3]triazines via an intramolecular heterocyclization of 1-azido-2-[isocyano(p-tosyl)methyl]benzenes under basic conditions has been developed. DFT calculations have been performed to further understand the mechanism of this heterocyclization, which occurs in good to excellent yields with a broad scope.

Scalable Synthesis of Silacyclohexanones and Ready Access to Silicon Building Blocks

A simple and efficient two-step method for the synthesis of silacyclohexanones starting from bis(bromoethylsilanes) using TosMIC is presented. The prepared silacyclohexanones were transformed to nine different heterocycles with silicon incorporation. In addition, the developed methodology was used for the synthesis of a sila analogue of the HDAC6 inhibitor tubastatin A.

Strain and Complexity, Passerini and Ugi Reactions of Four-Membered Heterocycles and Further Elaboration of TOSMIC Product

Straightforward and general Passerini and Ugi procedures have been developed to incorporate four-membered heterocycles into highly functionalized scaffolds. Additionally, toslymethyl isocyanide (TosMIC)-derived Ugi adducts have been prepared, showcasing the prospect of the multicomponent reaction.

Modular Synthesis of Tetrasubstituted Pyrroles via an Annulative Migration Reaction of Allenyl Ketones and p-Toluenesulfonylmethyl Isocyanide

The metal-free cyclization of allenyl ketones and p-toluenesulfonylmethyl isocyanide (TosMIC), promoted by Cs₂CO₃, provides a convenient access to tetrasubstituted pyrroles in which an acyl group undergoes 1,2-migration. This tandem Michael addition/annulative migration synthetic strategy is general and high-yielding for various substituted allenyl ketones. Moreover, a phosphoryl or ester moiety is also a suitable functionality to enable such migration.

Transition metal-catalysed carbene- and nitrene transfer to carbon monoxide and isocyanides

Transition metal-catalysed carbene- and nitrene transfer to the C1-building blocks carbon monoxide and isocyanides provides heteroallenes (i.e. ketenes, isocyanates, ketenimines and carbodiimides). These are versatile and reactive compounds allowing in situ transformation towards numerous functional groups and organic compounds, including heterocycles. Both one-pot and tandem processes have been developed providing valuable synthetic methods for the organic chemistry toolbox. This review discusses all known transition metal-catalysed carbene- and nitrene transfer reactions towards carbon monoxide and isocyanides and in situ transformation of the heteroallenes hereby obtained, with a special focus on the general mechanistic considerations.

Silver-Catalyzed Asymmetric Desymmetrization of Cyclohexadienones via Van Leusen Pyrrole Synthesis

A catalytic asymmetric desymmetrization of cyclohexadienones was accomplished via Van Leusen pyrrole synthesis in the presence of a chiral silver catalyst. The ready access to chiral-fused pyrrole derivatives is attributed to the identification of a suitable isocyanomethyl sulfone surrogate, NasMIC. The current Ag(I)-chiral phosphino-carboamide ligand system can be extended to the kinetic resolution of racemic cyclohexadienones, capitalizing on the differentiated reactivity of chiral quaternary complexes from AgSbF₆, chiral ligand (L*), cyclohexadienone, and NasMIC.

Fe(III)-Catalyzed N-Amidomethylation of Secondary and Primary Anilines with TosMIC

A Fe(III)-catalyzed N-amidomethylation of secondary and primary anilines with p-toluenesulfonylmethyl isocyanide (TosMIC) in water is described. TosMIC plays dual roles as the source of methylene as well as an amidating reagent to form α-amino amides in this multicomponent reaction. The combination of TosMIC and other isocyanides was also investigated to give the desired products in acceptable yields. The current protocol features use of iron catalyst and nontoxic media, broad substrate scope, mild conditions, and operational simplicity.

Iron-Mediated Selective Sulfonylmethylation of Aniline Derivatives with p-Toluenesulfonylmethyl Isocyanide (TosMIC)

An iron-mediated highly selective C-H sulfonylmethylation of aniline derivatives with p-toluenesulfonylmethyl isocyanide in a mixture solvent of H₂O and PEG₄₀₀ under an Ar atmosphere has been realized. This transformation proceeds with operational convenience, use of earth-abundant metal catalyst and nontoxic media, broad substrate scope, and good functional group tolerance. The current methodology could be applied to the regioselective C-H sulfonylmethylation of indolines, tetrahydroquinolines, and tertiary anilines.

Cascade synthesis of 2,4-disulfonylpyrroles by the sulfonylation/[2 + 3]-cycloaddition reactions of gem-dibromoalkenes with arylsulfonyl methyl isocyanides

An efficient cascade reaction involving sulfonylation and [2 + 3]-cycloaddition reactions of gem-dibromoalkenes with arylsulfonyl methyl isocyanides was described for the synthesis of 3-aryl-2,4-disulfonyl-1H-pyrroles. The main highlight of this study is the introduction of a new dual-functional reactivity of arylsulfonyl methyl isocyanides as the sulfonyl source as well as a 1,3-dipolar reagent in the same reaction. This system is facilitated by Cs2CO3 mediation in DMSO and 100 °C conditions.

The Ugi three-component reaction and its variants

A broad variety of α-aminoamide-based compounds have been synthesized via the three-component version of the Ugi reaction (U-3CR) or by any of its variants (Ugi-Zhu-3CR, Orru-3CR, Ugi-4C-3CR, Ugi-Joullié-3CR, GBB-3CR, Ugi-Reissert-3CR, and so on).

One pot synthesis of isocyano-containing, densely functionalised gem-difluoroalkenes from α-trifluoromethyl alkenes, alkyl halides and TosMIC

A base-promoted one-pot, three-component reaction of TosMIC with α-trifluoromethyl alkenes and alkyl halides has been deveolped for the synthesis of isocyano-containing, densely functionalised gem-difluoroalkenes.

Synthesis of polysubstituted pyrroles via isocyanide-based multicomponent reactions as an efficient synthesis tool

The present review covers all synthetic methods based on isocyanide-based multicomponent reactions for the preparation of polysubstituted pyrroles as the parent cores of many essential drugs, biologically active compounds, and compounds with wide application in materials science.

Aryl Azides as Forgotten Electrophiles in the Van Leusen Reaction: A Multicomponent Transformation Affording 4-Tosyl-1-arylimidazoles

Considering aryl azides as electrophilic partners for the TosMIC mediated Van Leusen reaction, a novel multicomponent synthesis of 4-tosyl-1-arylimidazoles is reported. In this transformation, two molecules of TosMIC participate in the reaction mechanism in two different ways, with the second molecule undergoing a novel type of fragmentation resulting in the incorporation of a C-H into the final product.

The base-free van Leusen reaction of cyclic imines on water: synthesis of N-fused imidazo 6,11-dihydro β-carboline derivatives

Construction of imidazoles has been demonstrated on water under base-free conditions. The reaction of dihydro β-carboline imines and p-toluenesulfonylmethyl isocyanides furnished the corresponding substituted N-fused imidazo 6,11-dihydro β-carboline derivatives in very good yields under ambient conditions. The use of deuterium oxide (D2O) as a solvent enabled the incorporation of deuterium isotopes in the imidazole ring.

Synthesis of polyheterocycles via multicomponent reactions

Polyheterocycles are one of the most desired synthetic targets due to their numerous and valuable applications in various fields. Multicomponent reactions (MCRs) are highly convergent one-pot processes, in which three or more reagents are combined sequentially to construct complex products, with almost all the atoms coming from the starting reagents. In this context, the syntheses of 'heterocycles' via MCR-based processes have been reviewed a number of times. However, there is not a single review (recent or otherwise) covering the synthesis of 'polyheterocycles' via a direct MCR or via a one-pot process involving MCRs coupled to further cyclizations (via ionic, metal-catalyzed, pericyclic, or free-radical-mediated cyclizations). This issue is consequently the main topic of the present review, which considers work from the last decade. The work is categorized according to the key processes involved in the syntheses of polyheterocycles, aiming to give readers an easy understanding of this MCR-based chemistry and to provide insights for further investigations. The reaction mechanisms providing novel elements to these MCR-based methods for the synthesis of polyheterocycles are also discussed.

Copper-mediated direct sulfonylation of C(sp2)–H bonds employing TosMIC as a sulfonyl source

Cu-Mediated sulfonylation of C(sp²)–H bonds with p-tosylmethyl isocyanide (TosMIC) as a sulfonyl source was developed utilizing a removable N,O-directing group.

Contemporary Synthetic Strategies toward seco-Prezizaane Sesquiterpenes from Illicium Species

Since the elucidation of the structure of anisatin in the late 1960s, sesquiterpene lactones from various Illicium species of plants have captivated synthetic chemists worldwide, resulting in a large body of synthetic work. In particular, Illicium sesquiterpenes containing the seco-prezizaane carbon framework have seen immense interest in recent years owing to desirable structural and medicinal attributes. This synopsis will focus on recently developed synthetic strategies to access these compact, highly oxidized terpenoids.

Catalytic Enantio- and Diastereoselective Mannich Addition of TosMIC to Ketimines

Chiral amines bearing a stereocenter in the α position are ubiquitous compounds with many applications in the pharmaceutical and agrochemical sectors, as well as in catalysis. Catalytic asymmetric Mannich additions represent a valuable method to access such compounds in enantioenriched form. This work reports the first enantio- and diastereoselective addition of commercially available p-toluenesulfonylmethyl isocyanide (TosMIC) to ketimines, affording 2-imidazolines bearing two contiguous stereocenters, one of which is fully-substituted, with high yields and excellent stereocontrol. The reaction, catalyzed by silver oxide and a dihydroquinine-derived N,P-ligand, is broad in scope, operationally simple, and scalable. Derivatization of the products provides enantioenriched vicinal diamines, precursors to NHC ligands and sp³ -rich heterocyclic scaffolds. Computations are used to understand catalysis and rationalize stereoselectivity.

γ-Carboline Synthesis by Heterocyclization of TosMIC Derivatives

A new method for the synthesis of γ-carbolines by a heterocyclization that involves α-indol-2-ylmethyl TosMIC derivatives and different electrophiles has been developed. This methodology has been successfully applied to the synthesis of several highly substituted γ-carbolines.

To each his own: isonitriles for all flavors. Functionalized isocyanides as valuable tools in organic synthesis

The term functionalized isocyanides refers to all those isocyanides in which a neighbouring functional group can finely tune the reactivity of the isocyano group or can be exploited in post-functionalization processes. In this manuscript, we have reviewed all the isocyanides in which the pendant functional group causes either deviation from or reinforces the normal reactivity of the isocyano group and categorized them to highlight their common features and differences. An analysis of their synthetic potential and the possible unexplored directions for future research studies is also addressed.

Multicomponent reactions: a sustainable tool to 1,2- and 1,3-azoles

The present review outlines the recent advancements and pioneering efforts on the synthesis of 1,2/1,3-azoles employing a multicomponent strategy.

Diversity-oriented catalyst-free synthesis of pseudopeptides containing rhodanine scaffolds via a one-pot sequential isocyanide-based six-component reactions in water using ultrasound irradiation

A planning strategy for diversity-oriented catalyst-free synthesis of pseudopeptides containing rhodanine scaffolds has been developed via a novel one-pot sequential six-component reaction in water. This approach is an efficient, environmentally friendly and expeditious procedure for direct access to wide ranges of pharmacologically significant and structurally interesting compounds based on the union of multicomponent reactions approach via tandem Michael/domino cycloaddition/Ugi reactions sequence from readily available starting materials. The syntheses were achieved by reaction of various primary amines, carbon disulfide, maleic anhydride or itaconic anhydride, aromatic aldehydes, anilines and isocyanides under ultrasound irradiation at room temperature in good yields. Providing of pseudopeptides containing rhodanines with the tandem formation of one new heterocyclic ring as well as creating the seven new bonds such as carbon-carbon, carbon-nitrogen, carbon-oxygen and carbon-sulfur with great efficiency and high atom/bond-forming/structure economy are outstanding features of this designed synthetic route.

[3+2] Cycloaddition of Tosylmethyl Isocyanide with Styrylisoxazoles: Facile Access to Polysubstituted 3-(Isoxazol-5-yl)pyrroles

A facile access to polysubstituted 3-(isoxazol-5-yl)pyrroles was developed through [3+2] cycloaddition of tosylmethyl isocyanide (TosMIC) and styrylisoxazoles. In the presence of KOH, various styrylisoxazoles reacted smoothly with tosylmethyl isocyanide and analogs to deliver a wide range of 3-(isoxazol-5-yl)pyrroles at ambient temperature. This transformation is operationally simple, high-yielding, and displays broad substrate scope.

Synergy Effects in the Chemical Synthesis and Extensions of Multicomponent Reactions (MCRs)-The Low Energy Way to Ultra-Short Syntheses of Tailor-Made Molecules

Several novel methods, catalysts and reagents have been developed to improve organic synthesis. Synergistic effects between reactions, reagents and catalysts can lead to minor heats of reaction and occur as an inherent result of multicomponent reactions (MCRs) and their extensions. They enable syntheses to be performed at a low energy level and the number of synthesis steps to be drastically reduced in comparison with ‘classical’ two-component reactions, fulfilling the rules of Green Chemistry. The very high potential for variability, diversity and complexity of MCRs additionally generates an extremely diverse range of products, thus bringing us closer to the aim of being able to produce tailor-made and extremely low-cost materials, drugs and compound libraries.

Silver-catalyzed formal [3+2]-cycloaddition of α-trifluoromethylated methyl isocyanides: a facile stereoselective synthesis of CF3-substituted heterocycles

An Ag-catalyzed formal [3+2]-cycloaddition of α-trifluoromethylated methyl isocyanides with polar double bonds has been developed for the expeditious synthesis of trifluoromethylated oxazolines, imidazolines and pyrrolines under mild conditions.

Multifunctional odorless isocyano(triphenylphosphoranylidene)-acetates: synthesis and direct one-pot four-component Ugi/Wittig cyclization to multisubstituted oxazoles

A new one-step four-component synthesis of multisubstituted oxazoles has been developed.