Organoborane compounds present a class of versatile synthetic intermediate for myriad organic transformations. The direct addition of a B–H bond across unsaturated bond—namely, hydroboration—is a powerful tool for the preparation of organoborane derivatives. This review outlines recent advances in catalytic hydroboration of unsaturated organic compounds, specifically those involving C-X (X = N, O) bonds. We will discuss the chemical behavior of both transition metal catalysts and main group catalysts in hydroboration. Emphasis will also be placed on the reaction mechanism of these catalytic reactions. Furthermore, recent achievements in catalytic hydroboration of carbon dioxide CO2 will be highlighted.

Catalytic Hydroboration of Carbonyl Derivatives, Imines, and Carbon Dioxide

The first metal-free catalytic hydroboration of carbonyl derivatives has been developed in which a catalytic amount of 1,3,2-diazaphospholene effectively promotes a hydroboration reaction of aliphatic and aromatic aldehydes and ketones. The reaction mechanism involves the cleavage of both the PO bond of the alkoxyphosphine intermediate and the BH bond of pinacolborane as well as the formation of PH and BO bonds. Thus, the reaction proceeds through a non-metal σ-bond metathesis. Kinetic and computational studies suggest that the σ-bond metathesis occurred in a stepwise but nearly concerted manner.

Metal‐Free σ‐Bond Metathesis in 1,3,2‐Diazaphospholene‐Catalyzed Hydroboration of Carbonyl Compounds

During the past years a number of interesting zinc catalyzed reactions have been reported, spanning a range from reduction to oxidation, (de)polymerization, synthesis of amines, or cyclopropanation reactions. This Perspective will focus on a selection of recent achievements applying catalytic amounts of zinc in organic transformations and raise the question if zinc can be a future option or tool for organic synthesis.

Rise of the Zinc Age in Homogeneous Catalysis

Aluminum Monohydride Catalyzed Selective Hydroboration of Carbonyl Compounds

https://www.rsc.org/suppdata/cc/c1/c1cc14508h/c1cc14508h.pdf

Catalytic hydroboration by an imido-hydrido complex of Mo(IV)

Synthesis and characterization of a chiral Zn(II) complex based on a trans-1,2-diaminocyclohexane derivative and catalytic reduction of acetophenone

In the title compound, [{η5-CpCo[P(O)(OMe)2]3}Nd(O2CCH3)2]2, with a centrosymmetric mol­ecule, each Nd atom has an eight-coordination environment, surrounded by a tripodal {LOMe = CpCo[P(O)(OMe)2]3} and four bridging acetato ligands. The coordination geometry around each Nd centre is described as a distorted square-antiprism and the two different types of acetato ligands have μ-O:O′- and μ-O,O′:O′-acetato coordination modes. The Nd—O distances are in the range 2.378 (4)–2.594 (5) A and the Nd⋯Nd distance is 3.9913 (6) A.

Soo Gyun Roh

Papers

Synthesis and characterization of a chiral Zn(II) complex based on a trans-1,2-diaminocyclohexane derivative and catalytic reduction of acetophenone

Di-μ-acetato-O:O′-di-μ-acetato-O,O′:O′-bis{[(cyclopentadienyl)tris(dimethylphosphito-P)cobalt-O,O′,O′′]neodymium(III)}

Soo Gyun Roh

Papers

Synthesis and characterization of a chiral Zn(II) complex based on a trans-1,2-diaminocyclohexane derivative and catalytic reduction of acetophenone

Di-μ-acetato-O:O′-di-μ-acetato-O,O′:O′-bis­{[(cyclo­penta­dienyl)tris­(di­methyl­phosphito-P)­cobalt-O,O′,O′′]neodymium(III)}

Di-μ-acetato-O:O′-di-μ-acetato-O,O′:O′-bis{[(cyclopentadienyl)tris(dimethylphosphito-P)cobalt-O,O′,O′′]neodymium(III)}