Metal-free oxidative formal C(sp2)-H arylation of cyclopentene-1,3-diones with ß-naphthols.

An efficient, mild, and transition-metal free formal C(sp2)-H arylation of prochiral 2,2-disubstituted cyclopentene-1,3-diones is reported. This oxidative arylation with ß-naphthols proceeds via base-mediated C-Michael addition followed by aerial oxygen insertion and a subsequent α-hydroperoxy elimination sequence. This operationally simple and environmentally benign transformation is highly scalable and does not require any pre-functionalization. Moreover, this reaction affords excellent yields of α-substituted ß-naphthols bearing all-carbon quaternary centers.

Enantioselective Cu(I)-catalyzed borylative cyclization of enone-tethered cyclohexadienones and mechanistic insights.

The catalytic asymmetric borylation of conjugated carbonyls followed by stereoselective intramolecular cascade cyclizations with in situ generated chiral enolates are extremely rare. Herein, we report the enantioselective Cu(I)-catalyzed ß-borylation/Michael addition on prochiral enone-tethered 2,5-cyclohexadienones. This asymmetric desymmetrization strategy has a broad range of substrate scope to generate densely functionalized bicyclic enones bearing four contiguous stereocenters with excellent yield, enantioselectivity, and diastereoselectivity. One-pot borylation/cyclization/oxidation via the sequential addition of sodium perborate reagent affords the corresponding alcohols without affecting yield and enantioselectivity. The synthetic potential of this reaction is explored through gram-scale reactions and further chemoselective transformations on products. DFT calculations explain the requirement of the base in an equimolar ratio in the reaction, as it leads to the formation of a lithium-enolate complex to undergo C-C bond formation via a chair-like transition state, with a barrier that is 22.5 kcal/mol more favourable than that of the copper-enolate complex.

Rh(III)-catalyzed diastereoselective cascade annulation of enone-tethered cyclohexadienones via C(sp2)-H bond activation.

Herein, we report highly diastereoselective arylative cyclization of enone-tethered cyclohexadienones via Rh(III)-catalyzed C-H activation of N-methoxybenzamides. This reaction proceeds through the formation of a five-membered rhodacycle followed by bis-Michael cascade annulation to access functionalized bicyclic scaffolds with four contiguous stereocenters with a broad substrate scope. These products have excellent functional handles, allowing further synthetic transformation to increase the structural complexity. Furthermore, mechanistic studies of arylative cyclization and a gram-scale experiment are also presented.