Controlled Regiodivergent C–H Bond Activation of Imidazo[1,5‑<i>a</i>]pyridine via Synergistic Cooperation between Aluminum and Nickel

The catalytic method features a cooperative interaction between Ni and Al imparting remote C–H alkenylation at the C5 position of imidazo­[1,5-<i>a</i>]­pyridine with alkynes at mild conditions. Exclusion of AlMe₃ switches the selectivity to the C3 position. Reactions with styrene and other olefinic substrates affording C5-adducts by Ni/Al catalysis are also included

Tandem Isomerization and C–H Activation: Regioselective Hydroheteroarylation of Allylarenes

The first Ni-promoted prototype reaction based on the tandem C–H activation of heteroarenes with alkene isomerization is demonstrated, leading to the branched hydroheteroarylation products. Simultaneously, the reaction selectivity can be chemically switched to linear adducts through Ni–Al tandem catalysis

Unusual Water-Soluble Imino Phosphine Ligand: Enamine and Imine Derivatives of 1,3,5-Triaza-7-phosphaadamantane (PTA)

A series of water-soluble and air-stable <i>E</i>-enamine derivatives of 1,3,5-triaza-7-phosphaadamantane (PTA), PTAC­(R)­NH₂, <b>1</b>–<b>4</b>, are reported along with data on <i>E–Z</i> isomerization and tautomerization to the imine form (PTA-CRNH). Reaction of 1,3,5-triaza-7-phosphaamantane-6-yl lithium, PTA-Li, with aromatic nitriles afforded <i>E</i>-enamine derivatives of PTA in good yield (49–91%). Phosphines <b>1</b>–<b>4</b> are stable toward water and air, and do not appear to isomerize or tautomerize, unless coordinated to a metal or oxidized. The corresponding oxides, OPTAC­(R)­NH₂ (<b>5</b>–<b>8</b>), were observed as ∼55/45 mixtures of <i>E</i> and <i>Z</i> isomers. Kinetic data on the <i>E–Z</i> isomerization is reported. Upon coordination of <b>1</b>–<b>4</b> to W­(CO)₄­(pip)₂, a κ¹-<i>P</i> enamine is formed, [W­(CO)₄(pip)­(κ¹-<i>P</i>-PTACRNH₂)]. Enamine–imine tautomerization of the metal bound phosphine was observed resulting in κ²-<i>P</i>,<i>N</i> imine complexes, [W­(CO)₄(κ²-<i>P</i>,<i>N</i>-PTA-CRNH)], <b>9</b>–<b>12</b>. The crystal structures of the κ¹-<i>P</i> enamine <b>11a</b>, κ²-<i>P</i>,<i>N</i> imine <b>9</b> and <b>12</b>, phosphines <b>1</b> and <b>3</b>, as well as phosphine oxide <b>8a</b> were obtained. DFT calculations on the various isomers of the phosphines and phosphine oxides are also reported

Hemilabile β‑Aminophosphine Ligands Derived from 1,3,5-Triaza-7-phosphaadamantane: Application in Aqueous Ruthenium Catalyzed Nitrile Hydration

A series of β-aminophosphines derived from 1,3,5-triaza-7-phosphaadamantane (PTA) are described. PTA-CHPhNHPh (<b>1</b>), PTA-CH­(<i>p</i>-C₆H₄OCH₃)­NHPh (<b>2</b>), and PTA-CPh₂NHPh (<b>3</b>) were prepared in good yield (62–77%) by reaction of lithiated PTA with the corresponding imine followed by hydrolysis. Compounds <b>1</b> and <b>2</b> were synthesized as pairs of diastereomers which were separated by successive recrystallization from THF/hexane. Compounds <b>1</b>–<b>3</b> are somewhat soluble in water (<i>S</i>₂₅^o = 4.8 (<b>1</b>), 4.9 (<b>2</b>), 2.7 (<b>3</b>) g/L). Upon coordination to Ru­(II) arene centers both monodentate (κ¹-P) [RuCl₂(η⁶-toluene)­(<b>1</b>–<b>3</b>)] and bidentate (κ²-P,N) [RuCl­(η⁶-toluene)­(<b>1</b>–<b>3</b>)]Cl coordination modes were observed. Ru­(II) arene complexes <b>4</b>–<b>6</b> exhibited hemilabile behavior transitioning between κ¹-P and κ²-P,N coordination upon change in solvent or addition of a coordinating ligand such as Cl^– or CH₃CN. Complexes (<b>4</b>–<b>6</b>) were found to be active air stable catalysts for the aqueous phase hydration of various nitriles with TOF up to 285 h^–1 and TON of up to 97 000 observed

Hemilabile β‑Aminophosphine Ligands Derived from 1,3,5-Triaza-7-phosphaadamantane: Application in Aqueous Ruthenium Catalyzed Nitrile Hydration

A series of β-aminophosphines derived from 1,3,5-triaza-7-phosphaadamantane (PTA) are described. PTA-CHPhNHPh (<b>1</b>), PTA-CH­(<i>p</i>-C₆H₄OCH₃)­NHPh (<b>2</b>), and PTA-CPh₂NHPh (<b>3</b>) were prepared in good yield (62–77%) by reaction of lithiated PTA with the corresponding imine followed by hydrolysis. Compounds <b>1</b> and <b>2</b> were synthesized as pairs of diastereomers which were separated by successive recrystallization from THF/hexane. Compounds <b>1</b>–<b>3</b> are somewhat soluble in water (<i>S</i>₂₅^o = 4.8 (<b>1</b>), 4.9 (<b>2</b>), 2.7 (<b>3</b>) g/L). Upon coordination to Ru­(II) arene centers both monodentate (κ¹-P) [RuCl₂(η⁶-toluene)­(<b>1</b>–<b>3</b>)] and bidentate (κ²-P,N) [RuCl­(η⁶-toluene)­(<b>1</b>–<b>3</b>)]Cl coordination modes were observed. Ru­(II) arene complexes <b>4</b>–<b>6</b> exhibited hemilabile behavior transitioning between κ¹-P and κ²-P,N coordination upon change in solvent or addition of a coordinating ligand such as Cl^– or CH₃CN. Complexes (<b>4</b>–<b>6</b>) were found to be active air stable catalysts for the aqueous phase hydration of various nitriles with TOF up to 285 h^–1 and TON of up to 97 000 observed