Carbenoid coupling reactions

Polycondensation via Carbenoid Coupling Reactions of Bis(dichloromethyl)arenes... 

In connection with nickel-catalysed reductive coupling reactions of dihaloarenes, leading to poly(arylene)s, the copper-catalysed reductive carbenoid coupling reactions involving substituted bis(dichloromethyl)arenes and metals or other reductants should be mentioned. The reductive carbenoid coupling of bis(phenyldichloromethyl)arene with zinc in the presence of Cu-based catalysts is shown below ... 

Treatment of gem-dibromocyclopropane 34 with Bu3ZnLi from —85 to 0°C generates 1-butylcyclopropylzinc 36 via the 1,2-migration of the zincate carbenoid 35 (equation 27)24. Subsequent Pd°-catalyzed cross-coupling reactions afford cyclopropane... 

Other annelation reactions leading to racemic [njhelicenes with n > 6 include carbenoid coupling providing the parent [7]helicene [74],... 

Tandem insertion of aUyl carbenoids and aldehydes affords some organic compounds resnlting from a three-component coupling reaction. The most extensively studied application of this methodology is the insertion of allyl carbenoids into zirconacycles and subsequent elaboration of the formed allylzirconocenes with electrophiles (Scheme 39). ... 

Metallations are more useful synthetically when the substrate contains only one reactive site. The syntheses of benzyl-, allyl-, pentadienyl- and more delocalized group-IA organometallics and of group-IA acetylides are best performed by reaction (a). These preparations are not complicated by secondary coupling reactions or by contamination of the reaction mixture with other metals. Metallations of halogen-containing substrates at low T give carbenoids which are difficult to prepare by other routes. 

In the laboratory of G.A. Sulikowski, an enantioselective synthesis of a 1,2-aziridinomitosene, a key substructure of the mitomycin antitumor antibiotics, was developed. Key transformations in the synthesis involved the Buchwald-Hartwig cross-coupling and chemoselective intramolecular carbon-hydrogen metal-carbenoid insertion reaction. 

Scheme 23. Copper-mediated coupling reactions of alkylidene carbenoids...

The C-H insertion reaction of phosphanylidene carbenoid is also found as a typical carbenoid reaction. The copper-mediated oxidative coupling reactions are powerful synthetic tools to construct some conjugated systems with the P=C skeleton, which are operated by treatment of oxygen. Lithium phosphanylidene carbenoids are applicable to synthesize the heavier heteroallenic compounds and stable biradical compounds. Moreover, an intriguing trimerization of phosphanylidene carbenoids is used to give the triphosphafulvene as an isomer of triphosphabenzene, which will lead to a novel organic chemistry. Indeed, the mentioned low-coordinated phosphorus compounds may well be applied to the synthesis of novel materials [5,64,65]. 

Motherwell and Roberts dicarbonyl coupling reaction can be improved by substituting l,2-bis(chlorodimethylsilyl)ethane for TMSCl. The intermediate organozinc carbenoids can be trapped with Series to produce cyclopropanes, as exemplifi in the... 

A one-pot synthesis and derivatization of diynes and triynes is reported. The polyyne framework was formed from a dibromoolefm precursor 96 based on a carbenoid rearrangement, and the resulting Li-acetylide is then transmetallated with zinc chloride which then allowed for the divergent preparation of aryl polyynes 97 via Negishi palladium-catalyzed cross-coupling reactions. 

The chemistry of copper carbenoids involved in the catalytic decomposition of diazo compounds and related tosylhydrazones has been reviewed. Many aspects of these catalytic transformations are covered including not only the classical cyclopropanation and X-H insertion processes but also a range of formal cycloaddition reactions, the reactions involving ylide formation, and the various coupling reactions of diazo derivatives. An account more focused on asymmetric metal-catalysed X-H insertion has been published. Through this review, the dependence on the nature of the metal and its i ligands can be evaluated for these 0-H, N-H, S-H, and Si-H insertions of carbenoids. 

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