Reaction of vinylcarbenoids with benzaldehydes: formation of vinylcarbonyl ylides followed by ring closure to oxiranes and dihydrofurans

Catalytic Epoxidation of Carbonyl Compounds via Carbonyl Ylides: from Racemic to Enantioselective

Transition metal-catalyzed epoxidation of carbonyl compounds through carbonyl ylides represents a highly effective method for synthesizing a diverse range of valuable epoxides. This review offers an in-depth overview of the latest developments in inter- and intramolecular epoxidation reactions involving metal carbenes and carbonyl compounds, encompassing both racemic to enantioselective transformations. These catalytic epoxidations are reviewed by highlighting their product selectivity, diversity and applicability, and the related mechanistic rationale is showcased where possible.

Asymmetric formal C-C bond insertion into aldehydes via copper-catalyzed diyne cyclization

The formal C-C bond insertion into aldehydes is an attractive methodology for the assembly of homologated carbonyl compounds. However, the homologation of aldehydes has been limited to diazo approach and the enantioselective reaction was rarely developed. Herein, we report an asymmetric formal C-C bond insertion into aldehydes through diyne cyclization strategy. In the presence of Cu(I)/SaBOX catalyst, this method leads to the efficient construction of versatile axially chiral naphthylpyrroles in moderate to excellent yields with good to excellent enantioselectivities. This protocol represents a rare example of asymmetric formal C-C bond insertion into aldehydes using non-diazo approach. The combined experimental and computational mechanistic studies reveal the reaction mechanism, origin of regioselectivity and stereoselectivity. Notably, the chiral phosphine ligand derived from synthesized axially chiral skeleton was proven to be applicable to asymmetric catalysis.

A Rh(II)-catalyzed highly stereoselective [3 + 2] annulation of vinyl diazoacetates with indole-2-carbaldehyde for the synthesis of indolyl dihydrofurans

A highly stereoselective Rh₂(Oct)₄-catalyzed [3 + 2] cycloaddition of vinyl diazoacetates with indolyl aldehyde has been developed. This protocol provides an efficient access to both cis and trans indolyl dihydrofurans with high yields and diastereoselectivities under mild conditions without or with Lewis acid as additive, respectively. Moreover, these generated functionalized dihydrofurans exhibit potent antiproliferation activity in three different cancer cell lines.

Organo or Metal Complex Catalyzed Synthesis of Five-membered Oxygen Heterocycles

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The reactions involving the formation of C-O bond using metal as a catalyst have emerged to be one of the most influential reactions for the synthesis of heterocycles in modern organic chemistry. Catalysis by metals offers diverse opportunities to invent new organic reactions with a promising range of selectivities such as chemoselectivity, regioselectivity, diastereoselectivity, and enantioselectivity. The methodologies used earlier for synthesis were less approachable to the organic chemist because of their high cost, highly specified instrumentation and inconvenient methods. For both stereoselective and regioselective formation of five-membered O-containing heterocycles, cyclic reactions that are metal and non-metal-catalyzed have known to be very efficient. The present review article covers the applications of metal and non-metal as a catalyst for the synthesis of five-membered O-containing heterocycles.

Unusually reactive and selective carbonyl ylides for three-component cycloaddition reactions

Conditions are described for the Rh-catalyzed formation of highly functionalized dihydro- and tetrahydrofuran products via three-component reactions of aldehydes, alpha-alkyl-alpha-diazoesters, and dipolarophiles. The alkyl-substituted carbonyl ylides that are generated in this fashion are highly reactive in cycloaddition reactions and display a scope of reactivity that is much broader than the three-component reactions of carbonyl ylides derived from ethyl diazoacetate or alpha-aryl-alpha-diazoesters. The reactions of alkyl-substituted carbonyl ylides proceed with high regioselectivity and diastereoselectivity that are rationalized in terms of an asynchronous, endo-selective transition state.

Highly Chemoselective 2,4,5-Triaryl-1,3-dioxolane Formation from Intermolecular 1,3-Dipolar Addition of Carbonyl Ylide with Aryl Aldehydes

[reaction: see text] Rhodium(II) acetate catalyzed 1,3-dipolar cycloaddition of methyl phenyldiazoacetate with a mixture of electron-rich and electron-deficient aryl aldehydes gave 1,3-dioxolanes in high yield with excellent chemoselectivity.

A Facile Three-Component One-Pot Synthesis of Structurally Constrained Tetrahydrofurans That Are t-RNA Synthetase Inhibitor Analogues

A one-pot procedure for the efficient synthesis of tRNA inhibitor analogues was developed. Thus, three-component 1,3-dipolar cycloaddition reactions of carbonyl ylides derived from diazoindan-1,3-dione and aldehydes with other dipolarophiles in 1,1,2,2-tetrachloroethane in 80 degrees C gave ring-fused tetrahydrofurans having three stereocenters in good yield.

Intermolecular rhodium(II)-catalyzed reactions with silicon-substituted carbonyl ylides

[reaction: see text] The Rh(II)-catalyzed reaction of benzyl 2-trialkylsilyl-2-diazoacetates with various acyclic and cyclic ketones affords novel dioxolanones via silicon-substituted carbonyl ylides in up to 98% yield.

Highly stereoselective syntheses of five- and seven-membered ring heterocycles from ylides generated by catalytic reactions of styryldiazoacetates with aldehydes and imines

[reaction--see text] Styryldiazoacetates are effective reactants for ylide formation that results in the formation of dihydropyrroles and dihydroazepines with high stereocontrol and in high yields.