One-Pot Preparation of Tricyclo[5.2.2.0^4,9]undecanes via Cu-Catalyzed Asymmetric Carboboration of Cyclohexadienone-Tethered Allenes

Abstract

The Cu-catalyzed asymmetric carboboration of cyclohexadienone-tethered allenes has been achieved through regioselective β-borylation of the allenes and subsequent conjugate addition to cyclohexadienones, affording cis-bicyclic frameworks with acceptable yields and high to excellent enantioselectivities. Further conjugate borylation of the carboboration products proved to be a favorable kinetic resolution process, which improved the overall enantioselectivity. Finally, one-pot preparation of highly enantioenriched tricyclo­[5.2.2.04,9]­undecanes was developed from the cyclohexadienone-tethered allenes through β-borylation/1,4-addition and subsequent tandem oxidation/intramolecular aldol reaction.

Rhodium(III)-Catalyzed Asymmetric Reductive Cyclization of Cyclohexadienone-Containing 1,6-Dienes via an Anti-Michael/Michael Cascade Process

“…Among the many prochiral molecules, cyclohexadienone derivatives, which are easily available through oxidative dearomatization of the corresponding phenols, have been widely investigated for desymmetrization using chiral organocatalysts or transition-metal catalysts . Recently, significant progress was achieved in transition-metal-catalyzed asymmetric cyclization of cyclohexadienone-containing 1,6-enynes and 1,6-enallenes, affording bicyclic and polycyclic skeletons with multiple stereocenters. However, due to the relatively low reactivity of simple alkenes, asymmetric cyclization of cyclohexadienone-tethered electron-rich alkenes (1,6-dienes) is still rare .…”

Rhodium-Catalyzed Enantioselective and Desymmetrizative Pauson–Khand Reaction: Access to Tricyclo[6.2.1.04,11]undecenes

“…In this context, a highly effective method for single-step enantioselective synthesis of these structures from readily accessible starting materials is highly attractive. Recently, seminal reports of 6–5–6 rings formation have emerged through desymmetrization of cyclohexadienones with alkenes, alkynes, or allenes . On the basis of our previous research in Rh-catalyzed oxa-PKR and recent asymmetric carbonylations, , we hypothesized that the desymmetrization PK reaction of C4-alkynyl substituted cyclohexadienones with CO might provide a straightforward strategy to form the 6–5–5 ring scaffolds (Scheme C).…”