Recent Developments in Coinage Metal Catalyzed Transformations of Stabilized Vinyldiazo Compounds: Beyond Carbenic Pathways

Abstract

Transition metal-catalyzed transformations of vinyldiazo compounds have become a versatile tool in organic synthesis. Although several transition metals have been investigated for this purpose, this field has been mainly dominated by dirhodium catalysts. Remarkable levels of chemo-, regio-, diastereo- and enantioselectivity have been reached in some of these rhodium-catalyzed transformations. In the last few years coinage metals have also emerged as useful catalysts in transformations involving vinyldiazo compounds. In some cases, highly efficient catalyst-dependent protocols arising from divergent mechanistic pathways have been reported. In this Personal Account, we aim to showcase recent advances in metal coinage catalyzed transformations of vinyldiazoacetates, an exciting field of research to which our group has actively contributed in the last few years.

Vinyldiazo Reagents and Metal Catalysts: A Versatile Toolkit for Heterocycle and Carbocycle Construction

“…Enantioselective dirhodium(II)-catalyzed formal [2+ +3]-cycloaddition reactions between alkenyldiazoacetates, in which an alkyl group is trans at the g-position, and nitrones were reported by Qin and Davies in 2013. [8] As illustrated in Scheme 6a, Rh 2 (R-TPCP) 4 facilitated dinitrogen extrusion from alkenyldiazoacetates to form rhodium-alkenylcarbenes;n ucleophilic attack by nitrones 7 at the vinylogous position of the electrophilic rhodium-alkenylcarbenes followed by five-memberedring closure produced rhodium-4-isoxazolidinylcarbenes;s ubsequent [1,3]-hydride abstraction and [1,2]-proton transfer completed this transformation. Interestingly,a ccording to early work from the Doyle group, [9,11] dirhodium(II)-catalyzedc yclization reactions of nitrones with methyl 2-diazo-3-butenoate, which does not bear as ubstituent at the g-position (Scheme 6b), [9] and methyl enoldiazoacetate, in whichasilyloxy substituent is at the b-position (Scheme 8a,S ection3.2), [11] resultedi nd istinctly different outcomes.A sd epicted in Scheme 6b,r hodium-4-isoxazolidinylcarbenes were also generated by rhodium-vinylcarbene formationf rom methyl 2-diazo-3-butenoate and their formal [2+ +3] cycloaddition with diarylnitrones.…”

“…Gold-catalyzed cyclization reactions of arylvinyldiazoacetates with aryldiazoacetates. catalysis by an N-heterocyclic carbene gold(I) complex, the preferentially formed gold-arylcarbenes underwent electrophilic addition at the terminal nitrogen atom of the arylvinyldiazoacetates, and subsequent ring closure followed by [1,3]proton transfer delivered pyrazole derivatives 27 (Scheme 14 a). [20] Notbaly, ortho-substituents on Ar 2 inhibited C=Cb ond formation owing to electrophilic attack by the gold-arylcarbenes at the diazo carbon atom of the arylvinyldiazoacetates.…”

“…Recently,e fficient and versatile cycloadditionm ethodologies from combinations of vinyldiazo reagents andm etal catalysts have been exhibited in the construction of carbocycles and heterocycles. [3] As depicted in Scheme 1, the common core structureo fv inyldiazo reagents is conjugated vinyl and diazo functionalities (C=CÀC=N 2 ), whereas different substituents (e.g.,hydro,alkyl, aryl, and silyloxy) and different electron-withdrawing groups(e.g.,ester,amide, and ketone) are attached to the vinyl moiety and diazo carbon atom, respectively;r hodium (especially Rh 2 L 4 )a nd coinage-metal (including copper,s ilver, and gold) complexess erve as the catalysts in the ring-forming reactions.…”

“…This umpolung is one of the principal causesf or the chemodivergence in catalytic reactions of vinyldiazo compounds. [3] This minireview,c overing the very latest achievements in the field of metal-catalyzed cyclization reactions with vinyldiazo reagents, focuses on reagent-or catalyst-dependent chemodivergence:1 )different substituents (e.g.,h ydro vs. silyloxy) or electron-withdrawing groups (e.g.,e ster vs. amide) installed on vinyldiazo reagents result in divergent cyclization pathways; 2) different metal catalysts (e.g.,r hodium vs. copper) lead to distinct cyclization outcomes. Twos ystematic reviewso n metal-catalyzed transformationso fv inyldiazo compounds have emphasized methodology developmenta nd mechanistic overview.…”

“…Twos ystematic reviewso n metal-catalyzed transformationso fv inyldiazo compounds have emphasized methodology developmenta nd mechanistic overview. [3] In this review,m etal-catalyzed cyclization reactions of vinyldiazo compounds with nitrosoarenes, nitrones, indoles, and other diazo compounds are selected and discussed to showcase the controllable versatility of the combination of vinyldiazo reagents and metal catalysts;w ea im to provide an illustrated manualo ft he cyclization toolkitc ontaining vinyldiazo reagents and metal catalysts, thus promoting its application and expansion by the widersynthetic community.…”