Palladium Catalyzed C–H Functionalization of <i>O</i>-Arylcarbamates: Selective <i>ortho</i>-Bromination Using NBS

A series of cyclometalated palladium complexes derived from O-phenylcarbamates has been synthesized by the reaction of the respective carbamates with Pd­(OAc)2 in the presence of acids, CF3CO2H, CF3SO3H, and p-TsOH. The palladacycles were observed to coordinate amines and electron rich anilines but not sulfonamides or carboxamides. Analysis of the tBu-NH2 adduct of the palladacycle 2b (2b·tBu-NH2) by NMR spectroscopy (NOE) revealed a cis-coordination of the amine. However, the amine adducts failed to undergo ortho-amination (C–N bond formation) under varied reaction conditions. Notably, the palladacycle 1d was found to react efficiently with N-iodosuccinimide (NIS) to yield the ortho-iodinated carbamate, 1e. More significantly, this reaction can be extended to a palladium-catalyzed ortho C–H bromination of aryl-O-carbamates even at 5 mol % loading of Pd­(OAc)2 using N-bromosuccinimide (NBS)

Copper-Catalyzed Amidation of 2-Phenylpyridine with Oxygen as the Terminal Oxidant

The Cu(OAc)2-catalyzed, O2-mediated amidation of 2-phenylpyridine via C−H bond activation is reported. A variety of nitrogen reagents including sulfonamides, carboxamides, and anilines participate in the reaction in moderate to good yields

Copper-Mediated Multiple C–H Functionalization of Aromatic <i>N</i>‑Heterocycles: Bromoamination of Indoles and Pyrroles

A copper-mediated bromoamination of aromatic N-heterocycles has been achieved using oxime esters as the N-reagents under mild conditions (ca. 70 °C). The reaction with N-alkyl indoles proceeds regioselectively to produce the 2-amino-3-bromo indole derivatives as confirmed by X-ray crystallographic analysis of the bromoaminated product, 3aa-Br. With N-methylpyrrole both the monobromoaminated and dibromoaminated products were produced by this method

Copper-Mediated Multiple C–H Functionalization of Aromatic <i>N</i>‑Heterocycles: Bromoamination of Indoles and Pyrroles

A copper-mediated bromoamination of aromatic <i>N</i>-heterocycles has been achieved using oxime esters as the <i>N</i>-reagents under mild conditions (ca<i>.</i> 70 °C). The reaction with <i>N</i>-alkyl indoles proceeds regioselectively to produce the 2-amino-3-bromo indole derivatives as confirmed by X-ray crystallographic analysis of the bromoaminated product, <b>3aa-Br</b>. With <i>N</i>-methylpyrrole both the monobromoaminated and dibromoaminated products were produced by this method

Anhydride-Additive-Free Nickel-Catalyzed Deoxygenation of Carboxylic Acids to Olefins

A nickel-catalyzed route for direct, anhydride-additive-free deoxygenation of fatty acids to the corresponding olefins has been developed. The transformation is catalyzed by simple nickel salts of the type NiX₂ (X = halide, acetate, acetylacetonate), uses PPh₃ as a stoichiometric reductant, and exhibits selectivity for generation of linear α-olefin products. The reaction was rendered cocatalytic in PPh₃ using 1,1,3,3-tetramethyldisiloxane (TMDS) as terminal reductant for the in situ reduction of OPPh₃ and catalytic Cu­(OTf)₂

Mimicking the Intradiol Catechol Cleavage Activity of Catechol Dioxygenase by High-Spin Iron(III) Complexes of a New Class of a Facially Bound [N₂O] Ligand

A series of high-spin iron(III) complexes, {N-R-2-[(pyridin-2-ylmethyl)amino]acetamide}FeCl3 [R = mesityl (1b), 2,6-Et2C6H3 (2b), and 2,6-i-Pr2C6H3 (3b)], that functionally emulate the intradiol catechol dioxygenase enzyme are reported. In particular, these enzyme mimics, 1b, 2b, and 3b, which utilized molecular oxygen in carrying out the intradiol catechol cleavage of 3,5-di-tert-butylcatechol with high regioselectivity (ca. 81−85%) at room temperature under ambient conditions, were designed by employing a new class of a facially bound [N2O] ligand, namely, N-R-2-[(pyridin-2-ylmethyl)amino]acetamide [R = mesityl (1a), 2,6-Et2C6H3 (2a), and 2,6-i-Pr2C6H3 (3a)]. The density functional theory studies revealed that the intradiol catechol cleavage reaction proceeded by an iron(III) peroxo intermediate that underwent 1,2-Criegee rearrangement to yield the intradiol catechol cleaved products analogous to the native enzyme

Mimicking the Intradiol Catechol Cleavage Activity of Catechol Dioxygenase by High-Spin Iron(III) Complexes of a New Class of a Facially Bound [N₂O] Ligand

A series of high-spin iron(III) complexes, {N-R-2-[(pyridin-2-ylmethyl)amino]acetamide}FeCl3 [R = mesityl (1b), 2,6-Et2C6H3 (2b), and 2,6-i-Pr2C6H3 (3b)], that functionally emulate the intradiol catechol dioxygenase enzyme are reported. In particular, these enzyme mimics, 1b, 2b, and 3b, which utilized molecular oxygen in carrying out the intradiol catechol cleavage of 3,5-di-tert-butylcatechol with high regioselectivity (ca. 81−85%) at room temperature under ambient conditions, were designed by employing a new class of a facially bound [N2O] ligand, namely, N-R-2-[(pyridin-2-ylmethyl)amino]acetamide [R = mesityl (1a), 2,6-Et2C6H3 (2a), and 2,6-i-Pr2C6H3 (3a)]. The density functional theory studies revealed that the intradiol catechol cleavage reaction proceeded by an iron(III) peroxo intermediate that underwent 1,2-Criegee rearrangement to yield the intradiol catechol cleaved products analogous to the native enzyme

High-Performance Pressure-Sensitive Adhesives from Renewable Triblock Copolymers

High-Performance Pressure-Sensitive Adhesives from Renewable Triblock Copolymer

Nickel Catalysts for the Dehydrative Decarbonylation of Carboxylic Acids to Alkenes

Combining high-throughput experimentation with conventional experiments expedited discovery of new first-row nickel catalysts for the dehydrative decarbonylation of the bioderived substrates hydrocinnamic acid and fatty acids to their corresponding alkenes. Conventional experiments using a continuous distillation process (180 °C) revealed that catalysts composed of Ni^II or Ni⁰ precursors (NiI₂, Ni­(PPh₃)₄) and simple aryl phosphine ligands were the most active. In the reactions with fatty acids, the nature of the added phosphine influenced the selectivity for α-alkene, which reached a maximum value of 94%. Mechanistic studies of the hydrocinnamic reaction using Ni­(PPh₃)₄ as catalyst implicate a facile first turnover to produce styrene at room temperature, but deactivation of the Ni(0) catalyst by CO poisoning occurs subsequently, as evidenced by the formation of Ni­(CO)­(PPh₃)₃, which was isolated and structurally characterized. Styrene dimerization is a major side reaction. Analysis of the reaction mechanism using density functional theory supported catalyst regeneration along with alkene formation as the most energetically demanding reaction steps