Arylboration of Alkenes by Cooperative Palladium/Copper Catalysis

Arylboration of vinylarenes and methyl crotonate with aryl halides and bis­(pinacolato)­diboron by cooperative Pd/Cu catalysis has been developed, giving 2-boryl-1,1-diarylethanes and an α-aryl-β-boryl ester in a regioselective manner. The reaction is compatible with a variety of functionalities and amenable to be scaled-up to a gram scale with no detriment to the yield. A short synthesis of the biologically active compound CDP840 was performed using the present reaction as a key step

How to Control Inversion vs Retention Transmetalation between Pd^II–Phenyl and Cu^I–Alkyl Complexes: Theoretical Insight

Transmetalation between Pd­(Br)­(Ph^A)­(PCyp₃)₂ (Ph = phenyl, Cyp = cyclopentyl) and Cu­(C^aHMePh^B)­(NHC) (NHC = 1,3-bis­(2,6-diisopropylphenyl)-imidazolidin-2-ylidene) is an important elementary step in recently reported catalytic cross-coupling reaction by Pd/Cu cooperative system. DFT study discloses that the transmetalation occurs with inversion of the stereochemistry of the C^aHMePh^B group. In its transition state, the C^aHMePh^B group has almost planar structure around the C^a atom. That planar geometry is stabilized by conjugation between the π* orbital of the Ph^B and the 2p orbital of the C^a. Another important factor is activation entropy (Δ<i>S</i>°^‡); retention transmetalation occurs through Br-bridging transition state, which is less flexible than that of the inversion transmetalation because of the Br-bridging structure, leading to a smaller activation entropy in the retention transition state than in the inversion transition state. For C^aHMeEt group, transmetalation occurs in a retention manner. In the planar C^aHMeEt group of the inversion transition state, the C^a 2p orbital cannot find a conjugation partner because of the absence of π-electron system in the C^aHMeEt. Transmetalation of C^aHMe­(CHCH₂) occurs in a retention manner because the vinyl π* is less effective for the conjugation with the C^a 2p because of its higher orbital energy than the Ph π*. The introduction of electron-withdrawing substituent on the Ph^B is favorable for inversion transmetalation. These results suggest that the stereochemistry of the C^a atom in transmetalation can be controlled by electronic effect of the C^aHMeR (R = phenyl, vinyl, or alkyl) and sizes of the substituent and ligand

How to Control Inversion vs Retention Transmetalation between Pd^II–Phenyl and Cu^I–Alkyl Complexes: Theoretical Insight

Transmetalation between Pd­(Br)­(Ph^A)­(PCyp₃)₂ (Ph = phenyl, Cyp = cyclopentyl) and Cu­(C^aHMePh^B)­(NHC) (NHC = 1,3-bis­(2,6-diisopropylphenyl)-imidazolidin-2-ylidene) is an important elementary step in recently reported catalytic cross-coupling reaction by Pd/Cu cooperative system. DFT study discloses that the transmetalation occurs with inversion of the stereochemistry of the C^aHMePh^B group. In its transition state, the C^aHMePh^B group has almost planar structure around the C^a atom. That planar geometry is stabilized by conjugation between the π* orbital of the Ph^B and the 2p orbital of the C^a. Another important factor is activation entropy (Δ<i>S</i>°^‡); retention transmetalation occurs through Br-bridging transition state, which is less flexible than that of the inversion transmetalation because of the Br-bridging structure, leading to a smaller activation entropy in the retention transition state than in the inversion transition state. For C^aHMeEt group, transmetalation occurs in a retention manner. In the planar C^aHMeEt group of the inversion transition state, the C^a 2p orbital cannot find a conjugation partner because of the absence of π-electron system in the C^aHMeEt. Transmetalation of C^aHMe­(CHCH₂) occurs in a retention manner because the vinyl π* is less effective for the conjugation with the C^a 2p because of its higher orbital energy than the Ph π*. The introduction of electron-withdrawing substituent on the Ph^B is favorable for inversion transmetalation. These results suggest that the stereochemistry of the C^a atom in transmetalation can be controlled by electronic effect of the C^aHMeR (R = phenyl, vinyl, or alkyl) and sizes of the substituent and ligand

Intramolecular Aminocyanation of Alkenes by Cooperative Palladium/Boron Catalysis

A cooperative palladium/triorganoboron catalyst to accomplish the intramolecular aminocyanation of alkenes through the cleavage of N–CN bonds is reported. 4,5-Bis­(diphenylphosphino)-9,9-dimethylxanthene (Xantphos) is found to be crucial as a ligand for palladium to effectively catalyze the transformation with high chemo- and regioselectivity. A range of substituted indolines and pyrrolidines with both tetra- or trisubstituted carbon and cyano functionalities are readily furnished by the newly developed cyanofunctionalization reaction. A preliminary example of enantioselective aminocyanation is also described

Anti-Markovnikov Hydroheteroarylation of Unactivated Alkenes with Indoles, Pyrroles, Benzofurans, and Furans Catalyzed by a Nickel–<i>N</i>‑Heterocyclic Carbene System

We report the catalytic addition of C–H bonds at the C2 position of hetero­arenes, including pyrroles, indoles, benzofurans, and furans, to unactivated terminal and internal alkenes. The reaction is catalyzed by a combination of Ni­(COD)₂ and a sterically hindered, electron-rich <i>N</i>-hetero­cyclic carbene ligand or its analogous Ni­(NHC)­(arene) complex. The reaction is highly selective for anti-Markovnikov addition to α-olefins, as well as for the formation of linear alkylheteroarenes from internal alkenes. The reaction occurs with substrates containing ketones, esters, amides, boronate esters, silyl ethers, sulfon­amides, acetals, and free amines

<i>para</i>-Selective Alkylation of Benzamides and Aromatic Ketones by Cooperative Nickel/Aluminum Catalysis

We report a method that ensures the selective alkylation of benzamides and aromatic ketones at the <i>para</i>-position via cooperative nickel/aluminum catalysis. Using a bulky catalyst/cocatalyst system allows reactions between benzamides and alkenes to afford the corresponding <i>para</i>-alkylated products. The origin of the high <i>para</i>-selectivity has also been investigated by density functional theory calculations

Rhodium Complexes Bearing PAlP Pincer Ligands

We report rhodium complexes bearing PAlP pincer ligands with an X-type aluminyl moiety. IR spectroscopy and single-crystal X-ray diffraction analysis of a carbonyl complex exhibit the considerable σ-donating ability of the aluminyl ligand, whose Lewis acidity is confirmed through coordination of pyridine to the aluminum center. The X-type PAlP–Rh complexes catalyze C2-selective monoalkylation of pyridine with alkenes

Rhodium Complexes Bearing PAlP Pincer Ligands

We report rhodium complexes bearing PAlP pincer ligands with an X-type aluminyl moiety. IR spectroscopy and single-crystal X-ray diffraction analysis of a carbonyl complex exhibit the considerable σ-donating ability of the aluminyl ligand, whose Lewis acidity is confirmed through coordination of pyridine to the aluminum center. The X-type PAlP–Rh complexes catalyze C2-selective monoalkylation of pyridine with alkenes

Rhodium Complexes Bearing PAlP Pincer Ligands

We report rhodium complexes bearing PAlP pincer ligands with an X-type aluminyl moiety. IR spectroscopy and single-crystal X-ray diffraction analysis of a carbonyl complex exhibit the considerable σ-donating ability of the aluminyl ligand, whose Lewis acidity is confirmed through coordination of pyridine to the aluminum center. The X-type PAlP–Rh complexes catalyze C2-selective monoalkylation of pyridine with alkenes

Rhodium Complexes Bearing PAlP Pincer Ligands

We report rhodium complexes bearing PAlP pincer ligands with an X-type aluminyl moiety. IR spectroscopy and single-crystal X-ray diffraction analysis of a carbonyl complex exhibit the considerable σ-donating ability of the aluminyl ligand, whose Lewis acidity is confirmed through coordination of pyridine to the aluminum center. The X-type PAlP–Rh complexes catalyze C2-selective monoalkylation of pyridine with alkenes