KOAc-Catalyzed One-Pot Three-Component 1,3-Dipolar Cycloaddition of α-Diazo Compounds, Nitrosoarenes, and Alkenes: An Approach to Functionalized Isoxazolidines

Intermolecular 1,3-Dipolar Cycloaddition Reaction of N-Carbamoyl Nitrones Generated by N-Selective Carbamoylation of Oximes with Isocyanates

N-Selective carbamoylation reaction of oximes with isocyanates generates nitrones, which undergo 1,3-dipolar cycloaddition with various dipolarophiles to afford diverse isoxazolidines. Notably, combinations of highly electron-rich oxime and highly electron-deficient dipolarophile exhibited high reactivity, with product yields of up to 94 %. The substituent on the isoxazolidine-nitrogen atom could be successfully removed without loss of the cyclic structure. Computational studies have also elucidated the mechanism of the reaction and origin of stereoselectivity.

Trapping of Arynes with In Situ Generated Aryltrifluoromethylnitrones Enables Access to Trifluoromethylated Benzoxazolines

Herein, we report a rare example of trapping arynes using in situ generated aryltrifluoromethylnitrone to access an important class of trifluoromethylated benzoxazolines. This three-component strategy involves a nitrone formation/[3 + 2] cycloaddition/thermal rearrangement cascade and furnishes trifluoromethylated benzoxazolines in high yields. The scope of the reaction is quite broad with respect to aryltrifluorodiazoethanes, nitrosoarenes, and arynes. The proposed reaction pathway is supported through the isolation and characterization of the key reaction intermediates phenyltrifluoromethylnitrone and benzisoxazoline.

Cycloaddition of N-arylnitrones with donor-acceptor oxiranes via C-C bond cleavage to construct 1,5,2-dioxazinanes

Highly functionalized 1,5,2-dioxazinanes could be smoothly produced via a Sc(OTf)3-catalyzed chemoselective [3 + 3] cycloaddition of various N-arylnitrones with a series of donor-acceptor oxiranes. This reaction involves in situ generation of 1,3-dipoles through Sc(OTf)3-catalyzed C-C bond cleavage of oxiranes and moderate to high yields were obtained for most substrates. This transformation features C-C bond cleavage of donor-acceptor oxiranes, accessible starting materials and mild reaction conditions.

Cu(OAc)2-catalyzed three-component cycloaddition of malonates, nitrosoarenes and alkenes: access to isoxazolidines

The Cu(OAc)₂-catalyzed one-pot three-component cycloaddition of malonates, nitrosoarenes and alkenes is described. A wide range of isoxazolidines could be obtained in moderate to excellent yields via this method. Mechanistic investigations indicated that the key step in this catalytic system is the straightforward formation of nitrone intermediates through the Cu(OAc)₂-catalyzed reaction of malonates with nitrosoarenes.

Hydrazones as Substrates in the Synthesis of Isoxazolidines via a KOH-Promoted One-Pot Three-Component Cycloaddition with Nitroso Compounds and Olefins

Hydrazones have been employed as the starting materials in a KOH-mediated one-pot three-component cycloaddition with readily accessible nitroso compounds and olefins to construct various isoxazolidines. Compared with diazo compounds as starting materials, this methodology could afford a wider range of products in good to excellent yields and diastereoselectivities for most substrates, and hydrazones are cheaper, more accessible, and safer substrates. The experimental study shows that the choice of suitable hydrazones is crucial.

Multicomponent Reactions Involving Diazo Reagents: A 5-Year Update

This review summarizes recent developments in multicomponent reactions of diazo compounds. The role of diazo reagent and the type of interaction between components was analyzed to structure the discussion. In contrast to previous reviews on related topics mostly focused on metal catalyzed transformations, a substantial amount of organocatalytic or catalyst-free methodologies is covered in this work.

Visible-light-promoted nitrone synthesis from nitrosoarenes under catalyst- and additive-free conditions

A green and sustainable nitrone formation reaction via visible-light-promoted reaction of aryl diazoacetates with nitrosoarenes is described. This protocol exhibits good functional group tolerance and broad substrate scope for both aryl diazoacetates with nitrosoarenes. Comparing the reported methods for the synthesis of nitrones from nitrosoarenes, the reaction described herein occurs under sole visible-light irradiation without the need of any catalysts and additives.

Directed Cobalt-Catalyzed C-H Activation to Form C-C and C-O Bonds in One Pot via Three-Component Coupling

Herein, we disclose an efficient cobalt-catalyzed three-component coupling of benzamides, diazo compounds, and tert-butyl hydroperoxide, which provides an efficient approach to construct C(sp²)-C(sp³) and C-O bonds in one-pot accompanied with C-H activation. This protocol features low catalyst loading (4 mol %), the avoidance of additives, and excellent functional group compatibility, providing three-component coupling adducts with high yields under mild conditions (up to 88%). Mechanism studies show that the reaction may involve a radical process.

NBS/DBU-Promoted One-Pot Three-Component Cycloaddition of Malonic Acid Derivatives, Nitrosoarenes, and Alkenes: Synthesis of Isoxazolidines

A general DBU-mediated one-pot three-component cycloaddition reaction of easily accessible malonic acid derivatives, nitrosoarenes, and alkenes has been successfully established with the aid of NBS to provide direct access to highly functionalized isoxazolidine derivatives with generally good to excellent yields, broad functional group tolerance, and excellent regio- and diastereo-selectivities under mild conditions. The mechanism study shows that the NBS-mediated formation of bromomalonic acid derivatives from malonic acid derivatives and DBU-promoted synthesis of nitrone intermediates via the reaction of bromomalonic acid derivatives with nitrosoarenes are key steps.

N-Alkyl nitrones as substrates for access to N-aryl isoxazolidines via a catalyst-free one-pot three-component reaction with nitroso compounds and olefins

N-Alkyl nitrones are used as starting materials to construct N-aryl isoxazolidines, instead of N-alkyl isoxazolidines or N–H 1,3-oxazinanes via a catalyst-free one-pot three-component reaction with nitrosoarenes and olefins.

Synthesis of isoxazolidines via catalyst-free one-pot three-component cycloaddition of sulfoxonium ylides, nitrosoarenes and alkenes

A general and practical strategy for the construction of various keto-substituted isoxazolidines via one-pot three-component reaction of easily accessible, safer and more stable sulfoxonium ylides, nitrosoarenes and olefins is described.

Synthesis of spirocyclic Δ4-isoxazolines via [3 + 2] cycloaddition of indanone-derived ketonitrones with alkynes

A [3 + 2] cycloaddition of indanone-derived nitrones and alkynes under mild conditions is developed, allowing facile synthesis of spirocyclicindenyl isoxazolines with structural diversity. The sequential protocol of generated in situ ketonitrone from unsaturated ketones and N-alkylhydroxylamines is also achieved successfully, affording the desired products in considerable yield with moderate to good diastereoselectivity. Moreover, the spirocyclic product can be conveniently transformed into indenyl-based allylic alcohol and enamide.

A [3 + 2] cycloaddition of indanone-derived nitrones with alkynes under mild conditions has been developed. It is a highly efficient and straightforward method for the synthesis of diverse spirocyclicindenyl isoxazolines.

Constructing chiral aza-quaternary carbon centers by enantioselective carbonylative Heck reaction of o-iodoanilines with allenes

The construction of chiral aza-quaternary C-centers via C–N bond formation is achieved by a Pd-catalysed asymmetric carbonylative Heck reaction of o-iodoanilines with allenes, providing chiral dihydroquinolinone derivatives with moderate to high yield and enantiomeric ratio.

Straightforward Approach toward Multifunctionalized Aziridines via Catalyst-Free Three-Component Reactions of α-Diazoesters, Nitrosoarenes, and Alkynes

A straightforward, catalyst-free atom- and step-economical approach for the synthesis of multisubstituted 1-arylaziridine-2-carboxylates via one-pot three-component reactions of α-diazoesters, nitrosoarenes, and alkynes has been described. This method could provide facile access to a variety of multifunctionalized aziridines in up to 91% yields under mild reaction conditions and features the catalyst-free strategy and use of cheap and readily accessible starting materials.

Humic acid as an efficient and reusable catalyst for one pot three-component green synthesis of 5-substituted 1H-tetrazoles in water

A simple one pot three-component green synthesis of 5-substituted 1H-tetrazoles is described using humic acid as an efficient catalyst in water.