Lithium amide catalyzed hydroboration of nitriles

An operationally facile hydroboration of nitriles is reported that utilizes the stable and inexpensive catalyst LiN(SiMe₃)₂. The reaction displayed good tolerance of functional groups and also converted carbonyl derivatives.

Magnesium-catalyzed hydroboration of organic carbonates, carbon dioxide and esters

A magnesium(i) complex was employed as a highly efficient precatalyst for the hydroboration of carbonates and esters under mild conditions.

Recent advances in transition metal-free catalytic hydroelementation (E = B, Si, Ge, and Sn) of alkynes

This review describes the recent advances in the transition metal-free hydroelementation of alkynes with various metalloid hydrides.

Scope and mechanism of nitrile dihydroboration mediated by a β-diketiminate manganese hydride catalyst

Nitrile insertion allows for manganese-catalyzed nitrile dihydroboration at 80 °C.

Syntheses of asymmetrical magnesium(i) complexes and their catalytic application in epoxide hydroboration

A series of novel structural magnesium(i) complexes stabilized by cyclopentyl and cyclohexyl substituted β-diketiminate ligands have been synthesized and used as highly active and regioselective pre-catalysts for various epoxides hydroboration.

Green hydroboration of carboxylic acids and mechanism investigation

A catalyst-free and solvent-free method for the hydroboration of a variety of carboxylic acids with pinacolborane was developed. The hydroboration of various aromatic and aliphatic carboxylic acids as well as dicarboxylic acids with HBpin could be completed within 6 h at room temperature or within 1 h at 60 °C to give the products in quantitative yields under neat conditions without the need for any solvent or metal catalyst. The possible reaction mechanism was investigated in detail based on the corresponding DFT calculations and the stoichiometric reaction of acetic acid with different equivalents of HBpin (at room temperature and 0 °C) and it revealed the stepwise nature of the protocol.

Catalytic Hydroboration of Aldehydes, Ketones, and Alkenes Using Potassium Carbonate: A Small Key to Big Transformation

An efficient transition-metal-free protocol for the hydroboration of aldehydes and ketones (reduction) was developed. The hydroboration of a wide range of aldehydes and ketones with pinacolborane (HBpin) under the K₂CO₃ catalyst has been studied. The reaction system is practical and reliable and proceeds under extremely mild and operationally simple conditions. No prior preparation of the complex metal catalyst was required, and hydroboration occurred stoichiometrically. Further, the chemoselective reduction of aldehydes over ketones was carried out. Moreover, we demonstrated the use of K₂CO₃ as an efficient catalyst for the hydroboration of alkenes. The operational simplicity, inexpensive and transition-metal-free catalyst, and the applicability to gram-scale synthesis strengthen its potential applications for hydroboration (reduction) at an industrial scale.

Efficient Cobalt Catalyst for Ambient-Temperature Nitrile Dihydroboration, the Elucidation of a Chelate-Assisted Borylation Mechanism, and a New Synthetic Route to Amides

N,N-Diborylamines have emerged as promising reagents in organic synthesis; however, their efficient preparation and full synthetic utility have yet to be realized. To address both shortcomings, an effective catalyst for nitrile dihydroboration was sought. Heating CoCl₂ in the presence of ^PyEtPDI afforded the six-coordinate Co(II) salt, [(^PyEtPDI)CoCl][Cl]. Upon adding 2 equiv of NaEt₃BH, hydride transfer to one chelate imine functionality was observed, resulting in the formation of (κ⁴-N,N,N,N-^PyEtIP^CHMeN^EtPy)Co. Single-crystal X-ray diffraction and density functional theory calculations revealed that this compound possesses a low-spin Co(II) ground state featuring antiferromagnetic coupling to a singly reduced imino(pyridine) moiety. Importantly, (κ⁴-N,N,N,N-^PyEtIP^CHMeN^EtPy)Co was found to catalyze the dihydroboration of nitriles using HBPin with turnover frequencies of up to 380 h^-1 at ambient temperature. Stoichiometric addition experiments revealed that HBPin adds across the Co-N_amide bond to generate a hydride intermediate that can react with additional HBPin or nitriles. Computational evaluation of the reaction coordinate revealed that the B-H addition and nitrile insertion steps occur on the antiferromagnetically coupled triplet spin manifold. Interestingly, formation of the borylimine intermediate was found to occur following BPin transfer from the borylated chelate arm to regenerate (κ⁴-N,N,N,N-^PyEtIP^CHMeN^EtPy)Co. Borylimine reduction is in turn facile and follows the same ligand-assisted borylation pathway. The independent hydroboration of alkyl and aryl imines was also demonstrated at 25 °C. With a series of N,N-diborylamines in hand, their addition to carboxylic acids allowed for the direct synthesis of amides at 120 °C, without the need for an exogenous coupling reagent.

Catalyst-Free Approach for Hydroboration of Carboxylic Acids under Mild Conditions

Herein, we present a facile method for deoxygenative hydroboration of a broad range of carboxylic acids under very mild conditions. The most striking feature of this attractive hydroboration is that this elusive and challenging transformation was realized without catalyst and solvent. The investigation of solvent effect showed that tetrahydrofuran was also suitable for this kind of reaction. Moreover, a successful gram-scale trial may provide a very promising toolkit for carboxylic acid reduction at a large scale.

Magnesium-Catalyzed Hydroboration of Terminal and Internal Alkynes

A magnesium-catalyzed hydroboration of alkynes providing good yields and selectivities for a wide range of terminal and symmetrical and unsymmetrical internal alkynes has been developed. The compatibility with many functional groups makes this magnesium catalyzed procedure attractive for late stage functionalization. Experimental mechanistic investigations and DFT calculations reveal insights into the reaction mechanism of the magnesium catalyzed protocol.

Unexpected intramolecular N-arylcyano-β-diketiminate cyclization in new aminoquinoline derivative complexes of aluminium for CO2 fixation into cyclic carbonates

exo-Dig intramolecular cyclization of β-diketiminates allowed to obtain 4-amino-3-iminoquinolines ligands through a novel pathway. Al(III) complexes bearing these ligands where active towards the synthesis of cyclic carbonates from epoxides and CO₂.

The complex reactivity of β-diketiminato magnesium(i) dimers towards pinacolborane: implications for catalysis

Reactions of magnesium(i) dimers with pinacolborane are complex, yielding many products (e.g. see picture). The results of this study bring into question mechanisms proposed for the magnesium(i) catalysed hydroboration of unsaturated substrates.

Mechanistic insights of anionic ligand exchange and fullerene reduction with magnesium(i) compounds

Exchange of anionic ligands on the Mg₂²⁺ ion via an associative mechanism can be facile and depends on ligand sterics and shape.

n-Butyllithium catalyzed hydroboration of imines and alkynes

Simple and convenient n-BuLi is reported as a highly efficient catalyst in promoting the hydroboration of imines and alkynes.

Catalyst-free and solvent-free hydroboration of ketones

The hydroboration of a wide range of ketones with HBpin under catalyst-free and solvent-free conditions was reported in high yields.

Recent advances in the catalytic hydroboration of carbonyl compounds

The latest development in the catalytic hydroboration of CO groups is summarized in this review. Access to borate ester intermediates provides a pathway to convert them into the corresponding valuable functionalized alcohols.