Rhodium‐Catalyzed [(3+2)+2] Carbocyclization of Alkynylidenecyclopropanes with Substituted Allenes: Stereoselective Construction of Tri‐ and Tetrasubstituted Exocyclic Olefins

Abstract

The development of the stereoselective rhodiumcatalyzed[ (3+ +2)+ +2] carbocyclization of alkynylidenecyclopropanes (ACPs) with substituted allenes is described. This work demonstrates that activated and unactivated allenes preferentially undergo carbometalation at the distal terminus to generate tri-and tetrasubstituted exocyclic olefins with an eutral rhodium catalyst. In addition, this method provides as trategy for the total synthesis of the guaiane family of sesquiterpenes,whichare not directly accessible using alkynes as exogenous p-components.F inally,t he preparation of the bicyclo[5.4.0]undecane ring system using ahomologated ACP tether serves to further illustrate the versatility of this approach. Scheme 1. Rationalef or the development of the rhodium-catalyzed [(3+ +2)+ +2] carbocyclization of ACPs with allenes.

Catalytic C–C Bond Activations via Oxidative Addition to Transition Metals

“…The same group extended the reactivity of ACPs to the [3 + 2+2]-cycloaddition with substituted allenes (Scheme ) . The reaction proceeds according to a similar mechanism as described above.…”

“…62 The same group extended the reactivity of ACPs to the [3 + 2+2]-cycloaddition with substituted allenes (Scheme 18). 63 The reaction proceeds according to a similar mechanism as described above. Oxidative addition of ACP 101 to the In addition, the reaction permits the formation of 5,7-and 6,7bicyclic structures in high regioselectivities.…”

Unveiling the Chemistry and Synthetic Potential of Catalytic Cycloaddition Reaction of Allenes: A Review

“…Evans and co-workers described the stereoselective synthesis of tri- and tetrasubstituted exocyclic alkenes via carbocyclization of several alkynylidenecyclopropanes (ACPs) with activated and inactivated allenes [ 88 ]. Their synthetic protocol for the formation of substituted exocyclic olefins was well suited for the synthesis of the guaiane family of sesquiterpenes via distal insertion of disubstituted allenes into ACPs.…”