Related Experiment Video
Updated: Jun 13, 2026
Synthesis of a Borylated Ibuprofen Derivative Through Suzuki Cross-Coupling and Alkene Boracarboxylation Reactions
Published on: November 30, 2022
On the possibility of catalytic reduction of carbonyl moieties with tris(pentafluorophenyl)borane and H2: a
Jonas Nyhlén1, Timofei Privalov
1Department of Organic Chemistry, Arrhenius Laboratory, Stockholm University, SE-106 91, Stockholm, Sweden.
Abstract:
The study thoroughly examines the Gibbs free energy surfaces of a new mechanism for reduction of ketones/aldehydes by tris(pentafluorophenyl)borane (1) and H(2). Key elements of the proposed mechanism are the proton and the hydride transfer steps similar to Stephan's catalytic reduction of imines by 1. The proton is transferred to the ketone/aldehyde in the process of H(2) cleavage by the carbonyl-borane couple and the hydride is transferred in a nucleophilic attack on the carbonyl carbon by the hydridoborate in the ionic pair, [HOCRR'](+)[HB(C(6)F(5))(3)](-). The in solvent Gibbs free energy barriers of H(2) splitting by adducts of B(C(6)F(5))(3) with acetone, acetophenone and benzaldehyde are predicted to be in the range of 24.5 +/- 2.5 kcal mol(-1), which corresponds to potential energy barriers in the range of 17.0 +/- 2.0 kcal mol(-1). Significantly lower barrier of H(2) activation is predicted in cases of bulky ketones such as 2,2,4,4-tetramethylpentan-3-one. With respect to the hydridoborate intermediate, the nucleophilic attack on the activated carbon is predicted to have a relatively low barrier for the sterically unhindered substrates, while this barrier is considerably higher for the sterically encumbered substrates. Since the formation of the hydridoborate intermediates is found to be endothermic, the transition state of the nucleophilic attack is the highest point of the computed energy profile for all tested substrates. Overall, according to in solvent density function calculations the proposed reduction of "compact" ketones/aldehydes by 1 and H(2) is allowed both thermodynamically and kinetically at elevated temperature, but it is expected to be slower and more substrate specific than the corresponding reduction of imines.
More Related Videos
Related Concept Videos
02:23Alcohols from Carbonyl Compounds: Reduction
Catalytic hydrogenation is similar to the reduction of an alkene or alkyne by adding H2 across the pi bond in the presence of transition metal catalysts like Raney Ni, Pd–C, Pt, or Ru. Aldehydes and ketones can be reduced by this method, often under mild to moderate heat (25–100°C) and...
02:47Alkynes to Aldehydes and Ketones: Hydroboration-Oxidation
One of the convenient methods for the preparation of aldehydes and ketones is via hydration of alkynes. Hydroboration-oxidation of alkynes is an indirect hydration reaction in which an alkyne is treated with borane followed by oxidation with alkaline peroxide to form an enol that rapidly converts into an aldehyde or a ketone. Terminal alkynes form aldehydes, whereas internal alkynes give ketones as the final product.
03:08Hydroboration-Oxidation of Alkenes
02:24Reduction of Alkynes to cis-Alkenes: Catalytic Hydrogenation
Like alkenes, alkynes can be reduced to alkanes in the presence of transition metal catalysts such as Pt, Pd, or Ni. The reaction involves two sequential syn additions of hydrogen via a cis-alkene intermediate.
02:36Regioselectivity and Stereochemistry of Hydroboration
Hydroboration proceeds in a concerted fashion with the attack of borane on the π bond, giving a cyclic four-centered transition state. The –BH2 group is bonded to the less substituted carbon and –H to the more substituted carbon. The concerted nature requires the simultaneous addition of –H and –BH2 across the same face of the alkene giving syn stereochemistry.
01:28Reduction of Benzene to Cyclohexane: Catalytic Hydrogenation