Copper-Catalyzed ortho-Functionalization of Quinoline N-Oxides with Vinyl Arenes

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.

Copper-catalyzed asymmetric 1,2-arylboration of enamines: access to chiral borate-containing 3,3'-disubstituted isoindolinones

An enantioselective copper-catalyzed 1,2-arylboration reaction of enamines has been developed by employing (R)-xyl-BINAP as a chiral ligand. A number of chiral borate-containing 3,3'-disubstituted isoindolinones were obtained in moderate to good yields and good to excellent enantioselectivities from the reactions of N-(o-iodobenzoyl)enamines and bis(pinacolato)diboron (B2pin2) under mild reaction conditions. Synthetic transformations of the products were conducted to demonstrate the practicality of 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.

Directed C8-H allylation of quinoline N-oxides with vinylcyclopropanes via sequential C-H/C-C activation

The Rh(III)-catalyzed C8-allylation of quinoline N-oxides has been accomplished using vinylcyclopropanes as an allyl source with excellent diastereoselectivity at room temperature. The C-H/C-C activation, substrate scope and natural product mutation are the important practical features.

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.

Copper-catalyzed C2 alkenylation of pyridine-N-oxides with alkynes

A general and expedient method to construct the scaffolds of 2-alkenylpyridines, through copper-catalyzed C2 alkenylation of pyridine-N-oxides with alkynes, has been disclosed. This protocol shows operational simplicity, good functional group compatibility and broad substrate scope.

Copper-catalyzed 1,2-Borylacylation of 1,3-Enynes: synthesis of β-Alkynyl ketones

A copper catalyzed 1,2-borylacylation of 1,3-enynes with B₂pin₂ and acid chlorides has been developed. Using readily available 1,3-enynes, B₂pin₂ and acid chlorides as substrates, a range of highly functionalized α,α-disubstituted β-alkynyl ketones were readily prepared under mild conditions in moderate to good yields. The borylacylated products can be easily derivatized to give several valuable structures. Notably, treatment of the products with NaBO₃·4H₂O provided 1,2-allenyl ketones, which is proposed to proceed via a retro-aldol process of the corresponding homopropargyl alcohols.

Copper-Catalyzed ortho-Alkenylation of Quinoline N-Oxides with Alkynes

A copper-catalyzed regioselective C-2 alkenylation of quinoline N-oxides with alkynes and pinacol diborane has been developed. This method provides efficient access to a wide variety of deoxygenated 2-alkenyl quinolines with...

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.

Cooperative Lewis Acid Catalysis for the Enantioselective C(sp3)-H Bond Functionalizations of 2-Alkyl Azaarenes

Herein, we describe the enantioselective C(sp³)-H bond functionalizations of 2-alkyl azaarenes using a cooperative dual Lewis acid catalysis. An achiral Lewis acid activates the unactivated azaarene partner without the need for a strong base. Orthogonally, a chiral-at-metal Lewis acid catalyst enables LUMO lowering and induces chirality. This method tolerates a range of complex molecular scaffolds and exhibits good to excellent yields and selectivity while accepting a wide variety of functional groups.

Selective Synthesis of Pyrano[3,2-b]indoles or Cyclopenta[b]indoles Tethered with Medium-Sized Rings via Cascade C-C σ-Bond Cleavage and C-H Functionalization

Highly atom-economical tandem reactions have been developed for the synthesis of pyrano[3,2-b]indoles or cyclopenta[b]indoles tethered with 7-, 8-, or 9-membered rings. These reactions first undergo a carbon-carbon σ-bond cleavage reaction of cyclic β-ketoesters. Next, in the presence of CuCl₂ and Ag₂CO₃, intramolecular O-H/C-H coupling occurs to give pyrano[3,2-b]indoles. This is the first example for capture of the enoloxyl radical of the intramolecular C-O bond formation reaction, whereas C3 nucleophilic addition afforded cyclopenta[b]indoles using TsOH·H₂O.