scholarly journals Ligand-Controlled Regiodivergence in Nickel-Catalyzed Hydroarylation and Hydroalkenylation of Alkenyl Carboxylic Acids

2020 ◽  
Author(s):  
Zi-Qi Li ◽  
Yue Fu ◽  
Ruohan Deng ◽  
Van Tran ◽  
Yang Gao ◽  
...  
Keyword(s):  
Dft Calculations ◽  
Transition State ◽  
Carboxylic Acids ◽  
Alkyl Group ◽  
Steric Effects ◽  
High Yield ◽  
Mechanistic Studies ◽  
Ligand Environment ◽  
Ligand Free ◽  
Electronic And Steric Effects

<div>A nickel-catalyzed regiodivergent hydroarylation and hydroalkenylation of unactivated alkenyl carboxylic acids is reported, whereby the ligand environment around the metal center dictates the regiochemical outcome. Markovnikov hydrofunctionalization products are obtained under mild ligand-free conditions, with up to 99% yield and >20:1 selectivity. Alternatively, anti-Markovnikov products can be accessed with a novel 4,4-disubstituted Pyrox ligand in excellent yield and >20:1 selectivity. Both electronic and steric effects on the ligand contribute to the high yield and selectivity. Mechanistic studies suggest a change in the turnover-limiting and selectivity-determining step induced by the optimal ligand. DFT calculations reveal that in the anti-Markovnikov pathway, repulsion between the ligand and the alkyl group is minimized (by virtue of it being 1° versus 2°) in the rate- and regioselectivity-determining transmetalation transition state. <br></div>

scholarly journals Ligand-Controlled Regiodivergence in Nickel-Catalyzed Hydroarylation and Hydroalkenylation of Alkenyl Carboxylic Acids

2020 ◽  
Author(s):  
Zi-Qi Li ◽  
Yue Fu ◽  
Ruohan Deng ◽  
Van Tran ◽  
Yang Gao ◽  
...  
Keyword(s):  
Dft Calculations ◽  
Transition State ◽  
Carboxylic Acids ◽  
Alkyl Group ◽  
Steric Effects ◽  
High Yield ◽  
Mechanistic Studies ◽  
Ligand Environment ◽  
Ligand Free ◽  
Electronic And Steric Effects

<div>A nickel-catalyzed regiodivergent hydroarylation and hydroalkenylation of unactivated alkenyl carboxylic acids is reported, whereby the ligand environment around the metal center dictates the regiochemical outcome. Markovnikov hydrofunctionalization products are obtained under mild ligand-free conditions, with up to 99% yield and >20:1 selectivity. Alternatively, anti-Markovnikov products can be accessed with a novel 4,4-disubstituted Pyrox ligand in excellent yield and >20:1 selectivity. Both electronic and steric effects on the ligand contribute to the high yield and selectivity. Mechanistic studies suggest a change in the turnover-limiting and selectivity-determining step induced by the optimal ligand. DFT calculations reveal that in the anti-Markovnikov pathway, repulsion between the ligand and the alkyl group is minimized (by virtue of it being 1° versus 2°) in the rate- and regioselectivity-determining transmetalation transition state. <br></div>

Studies on Iron-Catalyzed Aerobic Oxidation of Benzylic Alcohols to Carboxylic Acids

Synthesis ◽  
2018 ◽  
Vol 50 (08) ◽  
pp. 1629-1639 ◽  
Author(s):  
Shengming Ma ◽  
Xingguo Jiang
Keyword(s):  
Carboxylic Acids ◽  
Large Scale ◽  
Aerobic Oxidation ◽  
Catalytic Amount ◽  
Steric Effects ◽  
Benzylic Alcohols ◽  
Academic Laboratory ◽  
Electron Donating Groups ◽  
Electronic And Steric Effects ◽  
Comprehensive Study

A comprehensive study on aerobic oxidation of benzylic alcohols­ to carboxylic acids with a catalytic amount each of Fe(NO3)3·9H2O, TEMPO, and KCl is conducted. Various synthetically useful functional groups are well tolerated in the reaction. Distinct electronic and steric effects are observed in the reaction: electron-withdrawing groups accelerate the reaction while electron-donating groups make the reaction slower, and ortho-substituted substrates react slower than meta-substituted substrates. Several large-scale reactions (100 mmol) are conducted using a slow air flow of 30 mL/min to demonstrate the practicality of this method in an academic laboratory.

Hydroxamic acids. II. The acetylation of O-alkylhydroxamic acids

1969 ◽  
Vol 22 (1) ◽  
pp. 161
Author(s):  
MTW Hearn ◽  
AD Ward
Keyword(s):  
Hydroxamic Acid ◽  
Acetyl Derivative ◽  
Hydroxamic Acids ◽  
Steric Effects ◽  
High Yield ◽  
Acid Form ◽  
Acid System ◽  
Mild Conditions ◽  
Acidic Proton ◽  
Electronic And Steric Effects

O-Alkylhydroxamic acids are readily acetylated, in high yield, under mild conditions. Aliphatic O-alkylhydroxamic acids yield only one product, shown to be the N-acetyl derivative. O-Alkylarylhydroxamic acids form both the O- and N- acetyl isomers; the ratio of these isomers depends on electronic and steric effects. Ultraviolet spectral data indicate that the salts of O-alkylarylhydroxamic acids exist predominantly in the hydroximic acid form; however, it is not possible to decide which is the acidic proton of the hydroxamic acid system. The nature of the cation in the salts of O-alkylhydroxamic acids is important in determining the site of acetylation.

Electronic and steric effects on the solvation at the transition state in the solvolysis of some tertiary benzylic chlorides

1992 ◽  
Vol 33 (43) ◽  
pp. 6499-6502 ◽  
Author(s):  
Liu Kwang-Ting ◽  
Chen Pang-Shao ◽  
Chiu Pao-Feng ◽  
Tsao Meng-Lin
Keyword(s):  
Transition State ◽  
Steric Effects ◽  
Electronic And Steric Effects

Preparation, properties, and reductive alkylation of arylhydrazides

1998 ◽  
Vol 76 (8) ◽  
pp. 1180-1187 ◽  
Author(s):  
Giancarlo Verardo ◽  
Nicoletta Toniutti ◽  
Angelo G Giumanini
Keyword(s):  
Carboxylic Acid ◽  
Carboxylic Acids ◽  
Alkyl Group ◽  
Sodium Tetrahydroborate ◽  
Structural Features ◽  
High Yield ◽  
Reductive Alkylation ◽  
H Nmr ◽  
E And Z Isomers

1-Acyl-2-arylhydrazines (1), readily obtained in high yield from the condensation of arylhydrazines and the appropriate liquid carboxylic acid (2), underwent reductive alkylation with the same or different liquid carboxylic acids (2) and NaBH4 to give 1-acyl-2-alkyl-2-arylhydrazines (3) in good to moderate yields. The carboxylic acid has both the role of supplying the entering alkyl group and of acting as solvent. Most likely, it also modifies the BH4- anion to an active reducing agent under those conditions. The 1H NMR criteria for identifying the location of acylation of hydrazines and E and Z isomers are given. The MS spectra of the prepared hydrazides were analyzed in order to identify relevant structural features leading to specific fragmentations.Key words: 1-acyl-2-arylhydrazine, 1-acyl-2-alkyl-2-arylhydrazine, reductive alkylation, sodium tetrahydroborate, carboxylic acid.

Reactions of an Aluminium(I) Reagent with 1,2-, 1,3- and 1,5-Dienes: Dearomatisation, Reversibility, and a Pericyclic Mechanism

2019 ◽  
Author(s):  
Clare Bakewell ◽  
Martí Garçon ◽  
Richard Y Kong ◽  
Louisa O'Hare ◽  
Andrew J. P. White ◽  
...  
Keyword(s):  
Reaction Mechanism ◽  
Dft Calculations ◽  
Transition State ◽  
Reaction Pathways ◽  
Aromatic Rings ◽  
Aromatic Character ◽  
Pericyclic Reaction

The reactions of an aluminium(I) reagent with a series of 1,2-, 1,3- and 1,5-dienes are reported. In the case of 1,3-dienes the reaction occurs by a pericyclic reaction mechanism, specifically a cheletropic cycloaddition, to form aluminocyclopentene containing products. This mechanism has been interrogated by stereochemical experiments and DFT calculations. The stereochemical experiments show that the (4+1) cycloaddition follows a suprafacial topology, while calculations support a concerted albeit asynchronous pathway in which the transition state demonstrates aromatic character. Remarkably, the substrate scope of the (4+1) cycloaddition includes dienes that are either in part, or entirely, contained within aromatic rings. In these cases, reactions occur with dearomatisation of the substrate and can be reversible. In the case of 1,2- or 1,5-dienes complementary reactivity is observed; the orthogonal nature of the C=C π-bonds (1,2-diene) and the homoconjugated system (1,5-diene) both disfavour a (4+1) cycloaddition. Rather, reaction pathways are determined by an initial (2+1) cycloaddition to form an aluminocyclopropane intermediate which can in turn undergo insertion of a further C=C π-bond leading to complex organometallic products that incorporate fused hydrocarbon rings.

Sign in / Sign up

Export Citation Format

Share Document