Tandem Isomerization/α,β-Site-Selective and Enantioselective Addition Reactions of N-(3-Butynoyl)-3,5-dimethylpyrazole Induced by Chiral π–Cu(II) Catalysts

Chiral π–Cu(ii)-catalyzed site-, exo/endo-, and enantioselective dearomative (3 + 2) cycloadditions of isoquinolinium ylides with enamides, dienamides, and a trienamide

“…The site-selective, exo / endo -selective, and enantioselective (3 + 2) cycloaddition between 1 and 4 induced by Cu(OTf) 2 · L5 can be rationally interpreted in terms of the mechanism proposed in Scheme 4, which is based upon our previous related studies. 7 Cu(OTf) 2 · L5 chelates with 4 in such a way that the N -Dbs moiety of L5 and the 3,5-dimethylpyrazole moiety of 4 are anti to each other due to steric hindrance. Then, dipolar 1a approaches the α,β-double bond of 4c , activated by the π–Cu( ii ) complex of Cu(OTf) 2 · L5 , from the back of the N -Dbs group in a regio-, exo -, and enantioselective manner to give exo - 5ac via α,β- exo -TS.…”

“…Our previously developed chiral π–Cu( ii ) complexes have demonstrated exceptionally strong capabilities as Lewis-acidic catalysts in several highly useful asymmetric transformations. 7 We envisioned that such a highly effective catalyst system could potentially accomplish several highly important functions: (1) promote exo / endo -selective and enantioselective (3 + 2) cycloadditions between isoquinolinium ylides ( 1 ) and α-substituted, α,β-disubstituted, or β,β-disubstituted α,β-enamides ( 2 ) to conveniently provide pyrroloisoquinoline derivatives ( 3 ); (2) promote challenging highly α,β/γ,δ-site-selective, exo / endo -selective, and enantioselective (3 + 2) cycloadditions between 1 and α,β–γ,δ-dienamides ( 4 ); and (3) promote challenging highly ε,ζ-site-selective, endo -selective, and enantioselective (3 + 2) cycloadditions between 1 and α,β-γ,δ–ε,ζ-trienamide 9a (Scheme 2). If successful, the remarkable versatility of this catalytic system would significantly broaden its practical utility.…”

Copper-Catalyzed Asymmetric Kinugasa/Michael Addition Cascade Reactions for the Synthesis of Chiral Spiro β-Lactams

“…Such processes can be interrupted by adding additional electrophiles to trap the organocopper­(I) intermediates, leading to the formation of densely functionalized or fused nitrogen-containing heterocycles. This strategy has evoked remarkable efforts to develop novel cascade or one-pot reactions, and many gratifying results have been achieved. , …”