Stereoselective annulation between an allene, an alkene, and two nitrosoarenes to access bis(isoxazoliodine) derivatives

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.

Development of a [2 + 2]-Nitroso/Alkene Cycloaddition Using Sodium Tetrakis[3,5-bis(trifluoromethyl)phenyl]borate Catalyst: Controlled Chemoselectivity of Two Equilibrating Isomeric Intermediates

Sodium tetrakis[3,5-bis(trifluoromethyl)-phenyl]borate (NaBArF) catalyzes the [2 + 2] cycloaddition of 1,4-disubstituted cyclopenta-1,3-dien-2-yl esters with nitrsobenzene in toluene, affording two isolable regioisomers of 6-oxa-7-azabicyclo[3.2.0] heptanes, which thermally rearrange into the same 4-aminocyclopent-1-en-3-ones. In the case of 4-substituted cyclopenta-1,3-dien-2-yl esters, their initial [2 + 2] cycloaddition intermediates undergo a rapid ring expansion to afford six-membered piperidone derivatives efficiently.

Catalyst-free synthesis of isoxazolidine from nitrosoarene and haloalkyne via a 1,2-halo-migration/[3 + 2] cycloaddition cascade

An unprecedented catalyst-free three-component reaction to synthesize isoxazolidine from easily accessible haloalkyne, nitrosoarene and maleimide was developed. This reaction was proposed to proceed via a 1,2-halo migration and [3 + 2] cycloaddition cascade, providing a new reaction pattern of alkyne and nitroso containing species wherein a new type of nitrone was generated. Besides, the reaction conditions were efficient and environmentally benign, enabling the formation of various bioactivity-related isoxazolidines.

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.

Radical chemistry of nitrosoarenes: concepts, synthetic applications and directions

The radical chemistry of nitrosoarenes has recently emerged as an attractive and important topic in organic chemistry.

Synthesis of functionalized cyclopentenes through allenic ketone-based multicomponent reactions

A novel and efficient synthesis of diversely functionalized cyclopentene derivatives through the multicomponent reactions of 1,2-allenic ketones with 4-chloroacetoacetate and malononitrile/cyanoacetate under mild and metal-free conditions is presented. Mechanistically, the formation of title compounds involves a cascade process including nucleophilic substitution, Michael addition and intramolecular aldol type reaction. Interestingly, when 1-phenyl allenic ketones bearing electron-donating groups on the phenyl ring were reacted with 4-chloroacetoacetate and cyanoacetate, methylenecyclo-pentanes, the regioisomer of cyclopentenes, were formed with good selectivity and high efficiency.

Gold-catalyzed (4+3)-annulations of 2-alkenyl-1-alkynylbenzenes with anthranils with alkyne-dependent chemoselectivity: skeletal rearrangement versus non-rearrangement

Two distinct (4+3)-nitroxy annulations between 1,5-enynes and anthranils have been developed to access tetrahydro-1H-benzo[b]azepine derivatives.

Two distinct (4+3)-nitroxy annulations between 1,5-enynes and anthranils have been developed to access tetrahydro-1H-benzo[b]azepine derivatives; the chemoselectivity varies with the types of alkynes. Terminal alkyne substrates deliver benzo[b]azepine derivatives via a novel skeletal rearrangement while internal 1,5-enynes afford products without a rearrangement process. To elucidate the mechanism of rearrangement, we performed ¹³C- and ²H-labeling experiments to identify the gold-containing isobenzofulvene intermediates, but their formation relies on the presence of anthranils.