R. R. Kostikov

Azirinium ylides from alkoxycarbonylcarbenoids and 2H-azirines: Generation and transformations

Dirhodium tetraacetate-catalyzed decomposition of diazo esters in the presence of 3-aryl-2H-azirines having no substituent in the 2-position gives rise to azirinium ylides which then undergo isomerization into 2-azabuta-1,3-diene derivatives or (in the presence of excess diazo ester) react with the corresponding rhodium carbenoid to form substituted 3,4-dihydro-2H-pyrroles. 2-Mono-and 2,2-disubstituted 3-phenyl-2H-azirines react with rhodium carbenoids generated from diazo esters to give azirinium ylides which are converted into the corresponding 2-azabuta-1,3-dienes.

Intramolecular 1,3-dipolar cycloaddition to ester carbonyl of azomethinylides prepared from aldimines and difluorocarbene

Azomethinylides generated by reaction of difluorocarbene with N-alkyl- and N-arylimines of O-acylated salycilaldehyde undergo intramolecular 1,3-dipolar cycloaddition to the ester carbonyl group forming regioselectively 2,5-epoxy-1,4-benzoxazepine derivatives.

Regio- and stereoselectivity of cycloaddition of C-amidonitrones to esters of methylenecyclopropanedicarboxylic acids

C-Amidonitrones add regio- and stereoselectively to esters of 3-methylenecyclopropane-1,2-dicarboxylic, 2-(diphenylmethylene)cyclopropane-1,1-dicarboxylic, and 2-(1-phenylethylidene)cyclopropane-1,1-dicarboxylic acids to form a single diastereomer of 4-spirocyclopropaneisoxazolidines.

Regioselectivity in the Addition of 1,3-Dipolarophiles to 6-Aryl-1,5-diazabicyclo[3.1.0]hexanes

Thermolysis of 6-aryl-1,5-diazabicyclo[3.1.0]hexanes in the presence of 1,3-dipolarophiles having an unsymmetrically substituted double C=C bond (such as N-arylimides derived from 2-aryl-substituted maleic, citraconic, and itaconic acids, ethyl propynoate, aryl isocyanates, and aryl isothiocyanates) leads to formation of the corresponding 1,3-dipolar cycloaddition products. The reaction is regioselective, and in most cases only one regioisomer is obtained. The addition direction depends on the 1,3-dipolarophile structure, i.e., electronic and steric factors determining the most effective orbital interaction upon approach of the reagent to substrate.

Reaction of vinylidenecyclopropanes with aromatic imines in the presence of Lewis acids

Abstract1-Methyl-2-(2-methylpropenylidene)-1-phenylcyclopropane, 7-(2-methylpropenylidene)bicyclo[4.1.0]heptane, and (Z)-9-(2-methylpropenylidene)bicyclo[6.1.0]non-4-ene react with N-benzylideneanilines in the presence of boron trifluoride-ether complex to give pyrrolidine derivatives. Reactions of 1-methyl-1-phenyl-2-diphenylvinylidenecyclopropane with N-benzylideneanilines in the presence of BF3·Et2O, Yb(OTf)3, or Sc(OTf)3 lead to the formation of substituted 1,2,3,4-tetrahydroquinolines. 7-Diphenylvinylidenebicyclo[4.1.0]heptane in the presence of BF3·Et2O undergoes isomerization into 5-phenyl-8,9,10,11-tetrahydro-7H-cyclohepta[a]naphthalene.

Intramolecular 1,3-Dipolar Cycloaddition of Azomethine Ylides Generated from Ethoxycarbonylcarbenoids and Schiff Bases

Decomposition of ethyl diazoacetate in the presence of copper, copper acetylacetonate, or copper trifluoroacetylacetonate and ethyl 4-[2-(R-imino)phenoxymethyl]-2-butenoate leads to formation of chromeno-[4,3-b]pyrrole-2,3-dicarboxylic acid derivatives. The reactions involve intermediate formation of azomethine ylides which undergo regio- and stereoselective intramolecular cycloaddition at the C=C bond to afford chromeno[4,3-b]pyrroles. The steric structure of the product depends on the configuration of intermediate ylide and nature of the substituent at the ylide nitrogen atom.

( Z )-1-alkylidene- and 1-arylmethylidene-5,5-dimethyl-3-oxopyrazolidin-1-ium-2-ides and their cycloaddition to N -arylmaleimides

The reaction of (Z)-1-arylmethylidene-5,5-dimethyl-3-oxopyrazolidin-1-ium-2-ides with para-substituted N-arylmaleimides at 110°C is cis-stereoselective [cis/trans-adduct ratio ≥(9–10): 1]. Under analogous conditions, the conversion of (Z)-1-(2,6-dichlorophenylmethylidene)-5,5-dimethyl-3-oxopyrazolidin-1-ium-2-ide in the reaction with N-(4-methoxyphenyl)maleimide in 6-7 h did not exceed 1–2%. The cycloaddition of (Z)-1-ethylidene- and (Z)-1-(2-methylpropylidene)-5,5-dimethyl-3-oxopyrazolidin-1-ium-2-ides to N-arylmaleimides, regardless of the substituent in the phenyl group of the latter, gave preferentially the corresponding trans-adducts, which cannot be rationalized only by steric effect of substituents in terms of the concerted mechanism.

1,3-Dipolar Cycloaddition of Difluoro-Substituted Azomethine Ylides. Synthesis and Transformations of 2-Fluoro-4,5-dihydropyrroles

Abstract2-Fluoro-4,5-dihydropyrrole-3,4-dicarboxylic acid derivatives were obtained by reaction of difluorocarbene with N-substituted ketone imines in the presence of fumaronitrile, maleonitrile, or dimethyl maleate. The reaction involves intermediate formation of azomethine ylides and their subsequent cycloaddition at the double bond. 11H-Dibenz[b,e]azepine and 3,4-dihydroisoquinolines react with difluorocarbene in the presence of fumaronitrile to give fluoro-substituted dibenzo[c,f]pyrrolo[1,2-a]azepine and pyrrolo[2,1-a]-isoquinoline derivatives. Treatment of 2-fluoro-4,5-dihydropyrrole-3,4-dicarbonitrile with amines and alkoxides affords the corresponding 2-amino- and 2-alkoxy derivatives, while its reactions with hydrazine hydrate and benzimidamide lead to formation of substituted pyrrolo[2,3-c]pyrazole and pyrrolo[2,3-d]-pyrimidine derivatives.

Reactions of 1, 5-π-cyclization of gem-difluoro-substituted azomethine ylides involving an aromatic ring

Reactions of N-(5-R-furan-2-ylmethylidene)anilines with difluorocarbene proceeds through intermediate azomethine ylides suffering 1,5-π-cyclization to yield 6,6-difluorocyclopropa[b]furo[2,3-c]pyrrole and/or 4,4,6,6-tetrafluorocyclopropa[b]furo[2,3-c]pyrrole. The heating of these compounds without solvent resulted in high yields of 2,5-disubstituted 7-fluoro-4,5-dihydrofuro[3,2-c]pyridin-4(5H)-ones.

Immonium ylides derived from halocarbenes in the synthesis of nitrogen-containing compounds

Reactions of halocarbenes with imines, ketenimines, and aromatic azaheterocycles, which proceed through the corresponding azomethine ylides, keteneimine ylides, and cycloimmonium ylides, are reviewed. New routes for the synthesis of halo- and nitrogencontaining compounds using the transformations of halosubstituted immonium ylides are discussed.