Rare‐earth metal‐catalyzed hydroboration of unsaturated compounds

Abstract

The reduction of unsaturated compounds is one of the most widely applied transformations in organic synthesis. Aggressive reductants, highly pressurized hydrogen gas, and stoichiometric amount of metal salts used have greatly burdened the environment, stimulating the development of catalytic approaches with milder and greener conditions. In this context, the hydroboration has attracted great attention, and great progress has been achieved in the past decades. Due to the great performance of rare‐earth complexes in numerous organic transformations, such complexes are also employed as catalysts in the hydroboration of different unsaturated compounds. The current review summarized recent works of rare‐earth complexes catalyzed hydroboration of various unsaturated compounds, covering the publications mainly in past 5 years albeit with alkenes as exception. The transformations are mainly classified into two categories: hydroboration of C–C and C–hetero unsaturated compounds, and some closely related works are also discussed, such as rare‐earth catalyzed direct borylation of C–H bonds.

Exploration of Ligand-Centered Hydride Transfer in La/Y-Catalyzed Deoxygenative Reduction of Tertiary Amides with Pinacolborane

“…13−15 Significant progress has been made in the deoxygenation of amides to amines via hydrosilylation and hydroboration. 16,17 The catalytic hydroboration of unsaturated carbon heteroatom bonds is a straightforward method for the synthesis of organoboranes. In the hydroboration reactions, the mild and easily handled pinacolborane (HBpin) has become a promising reducing agent to provide a hydride source and shows good functional group tolerance.…”

“…The traditional reduction methods usually require harsh reductants such as LiAlH 4 , BH 3 , and pressurized H 2 . − Applications of these methods are thus limited by the harsh reaction conditions as well as the poor selectivity and tolerance. Consequently, development of a more safe and reliable hydride source to realize the selective and efficient reduction of amides is of great interest and importance. − Significant progress has been made in the deoxygenation of amides to amines via hydrosilylation and hydroboration. , The catalytic hydroboration of unsaturated carbon heteroatom bonds is a straightforward method for the synthesis of organoboranes. In the hydroboration reactions, the mild and easily handled pinacolborane (HBpin) has become a promising reducing agent to provide a hydride source and shows good functional group tolerance. − …”

Magnesium halide-catalyzed hydroboration of isocyanates and ketones

“…Recently, the hydroboration of unsaturated organic substrates has attracted wide attention and considerable development has been achieved. 11–27 Compared with alkene (CC), alkyne (CC) and nitrile (CN) unsaturated bonds, reports on metal-catalyzed hydroboration of isocyanates are very few. 28–35 In 2021, Nembenna et al .…”

Mechanistic study of homoleptic trisamidolanthanide-catalyzed aldehyde and ketone hydroboration. Chemically non-innocent ligand participation

“…37 Lanthanide-organic catalysts are efficient and selective hydroboration catalysts and, regarding specic unsaturations, have proven procient in the hydroboration of carbonyl functionalities. [38][39][40][41][42][43][44] They lend themselves well to this transformation due to the oxophilic nature of the lanthanide ion, which aids in carbonyl coordination/activation. While the use of rare earth catalysts for the hydroboration of C]X bonds has been on the rise, there has been limited mechanistic information which would provide valuable insight into reaction pathways and their potential manipulation in this emerging eld.…”