Copper-Catalyzed Regioselective Arylation or Alkenylation of Quinoline N-Oxides with Organoboronates

A copper-catalyzed arylation or alkenylation of quinoline N-oxides with aryl- or alkenylboronates, respectively, has been developed, which provides an efficient route for C2-substituted oxygenated quinolines under mild reaction conditions. The reaction shows a broad substrate scope for both quinoline N-oxides and aryl/alkenylboronates, mild reaction conditions, and high reaction efficiency. The formation of an aryl- or alkenyl-copper species as the key intermediate was suggested to be involved in this reaction.

Gold-Catalyzed Regio- and Stereoselective Alkenylation of Quinoline N-Oxides with Allenamides

A gold-catalyzed cycloaddition/ring opening of allenamides with quinoline N-oxides has been developed, which provides C2-alkenylated quinolines with high E selectivity in moderate to high yields. It is noted that quinoline N-oxides with a C8 or C7 substituent are crucial for this catalytic reaction.

Ligand-Controlled Regiodivergent Cyanoboration of Internal Allenes by Copper Catalysis

The first copper-catalyzed regiodivergent cyanoboration of internal allenes with B₂ pin₂ (bis(pinacolato)diboron) and NCTS (N-cyano-N-phenyl-p-toluenesulfonamide) derivatives is reported. The β,γ- and α,β-cyanoborylated products were synthesized with high regio- and stereo-selectivity. Computational studies revealed that nucleophilic addition of allylcopper or related intermediates on cyanation reagent is the regio- and stereo-determining step, while transmetalation with B₂ pin₂ is the rate-determining step. The nucleophilic addition step proceeds via inner-sphere mechanism in the Cu^I /P(o-tol)₃ and Cu^I /Xantphos (P(o-tol)₃ =tris(o-methylphenyl)phosphine, Xantphos=4,5-bis(diphenylphosphino)-9,9-dimethylxanthene) catalytic systems and via outer-sphere mechanism in the Cu^II /Xantphos catalytic system, respectively.

Catalyst-free synthesis of quinoline-enols through coupling between heterocyclic N-oxides and CF3-ynones under mild conditions

The coupling between heterocyclic N-oxides and CF3-ynones has been demonstrated via the formal C–H and C–C bond cleavage under catalyst-free and mild conditions.