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Intramolecular addition reactions of electrophilic metallovinylcarbenes with nucleophiles that do not have access to the carbene center undergo addition to the vinylogous position, forming products that rely on subsequent transformations of vinylmetal intermediates. Catalytic addition to a carbon-carbon double bond elicits the formation of an intermediate carbocation whose proton loss causes protodemetalation of the vinylmetal intermediate. Addition to the azido group results in the formation of aliphatic 1,2,3-triazines by [3 + 3]-cycloaddition. Catalytic intramolecular reactions with a carbamate nucleophile yield a carbonyl ylide whose loss of isobutylene produces oximidovinyl-oxazolidinone esters with high enantioselectivity. Comparisons are made between rhodium, copper, gold, and silver catalysts 

Abstract A Brønsted acid catalyzed C–H functionalization of vinyldiazoacetates with 3-hydroxyisoindolinone is developed. This methodology provides a general access to E-substituted isoindolinone vinyldiazo compounds in good yields and excellent diastereoselectivities with broad substrate generality under mild conditions, and with 4-substituted 2-diazo-3-butenoates produces fused bicyclic pyrrolidines. The reaction generally involves addition of the N-acyl ketiminium electrophile, formed from the 3-hydroxyisoindolinone, to the vinylogous position of the vinyldiazo compound resulting in vinyldiazonium ion intermediates that undergo deprotonation to new vinyldiazo compounds or ring closure to fused bicyclic pyrrolidines. 

Triflimide catalysis of the [3 + 2]-cycloaddition of 3-indolymethanols with vinyldiazoacetates provides general access to β-tetrahydrocyclopenta[b]indol-substituted α-diazoesters. Initiated by addition of the in situ generated vinylogous iminium electrophile from 3-indolymethanol to the vinylogous position of the vinyldiazo compound and completed by intramolecular cyclization from the vinyldiazonium ion intermediate, this transformation occurs in good yields and excellent diastereoselectivity with a broad substrate scope under mild conditions. The resulting α-diazoesters undergo Rh2(OAc)4-catalyzed substrate-dependent 1,2-migration to form multisubstituted carbazoles in high yields. 

Highly selective formal [3 + 2]-cycloaddition of vinyldiazoacetates with quinone ketals and quinoneimine ketals has been accomplished at room temperature with catalytic amounts of the Brønsted acid triflimide, leading to highly functionalized diazoacetates in good yields. The vinyldiazonium ion generated by electrophilic addition to the vinylogous position of the reactant vinyldiazo compound is the key intermediate in this selective transformation. Both oximidovinyldiazoacetates and those with other vinyl substituents undergo cycloaddition reactions with quinone ketals whose products, after extended reaction times, undergo substrate-dependent 1,2-migration; catalysis by Rh2(OAc)4, HNTf2, and Sc(OTf)3 effects these 1,2-migrations to the same products. However, the products from HNTf2-catalyzed reactions between quinoneimine and oximidovinyldiazoacetates undergo Rh2(OAc)4-catalyzed 1,3-C−H insertion. 1,3-Difunctionalization products are obtained for electrophilic reactions of Eschenmoser’s salt with selected vinyldiazoacetates, but with α-dibenzylaminomethyl ether, 1,6-hydride transfer reactions are observed with oximidovinyldiazoacetates. 

Highly selective formal [4 + 2]-cycloaddition of vinyldiazoacetates with azoalkenes from a-halohydrazones, as well as with cyclopentadiene and furan, occurs with light irradiation at room temperature, producing highly functionalized heterocyclic and bicyclic compounds in good yields and excellent diastereoseletivity. Under blue light these vinyldiazoacetate reagents selectively form unstable cyclopropenes that undergo intermolecular cycloaddition reactions at a faster rate than their competitive ene dimerization. [4 + 2]-cycloaddition of vinyldiazoacetates with in situ formed azoalkenes produces bicyclo[4.1.0]tetrahydropyridazine derivatives and, together with their cycloaddition using cyclopentadiene and furan that form tricyclic compounds, they occur with high chemoselectivity and diastereocontrol, good functional group tolerance, and excellent scalability. Subsequent transformations portray the synthetic versatility of these structures. 

A substituted donor–acceptor cyclobutenecarboxamide is synthesized with modest enantiocontrol through a chiral copper(I) complex catalyzed [3 + 1]-cycloaddition reaction of α-acyl diphenylsulfur ylides with 3-siloxy-2-diazo-3-butenamides. With a methyl substituent on the 4-position of the 3-butenamide, the cis-vicinal-3,4-disubstituted cyclobutenecarboxamide is formed with >20:1 diastereocontrol. Donor-acceptor 3-methyl-2-siloxycyclopropenecarboxamide is rapidly formed from the reactant enoldiazoamide and undergoes catalytic ring opening to give only the Z-γ-substituted metallo-enolcarbene. Elimination from 3-siloxy-2-diazo-3-pentenamide to form the conjugated 3-siloxy-2,4-pentadienamide is competitive but minimized at low temperature.