Bis(pinacolato)diboron, B₂pin₂

See also: Bis(neopentylglycolato)diboron, Tetrahydroxydiboron

Recent Literature

CrCl₂ mediates a nucleophilic addition of a primary amine derivative to an aldehyde to provide an alcohol. This radical-polar crossover process is selective for aldehydes and compatible with numerous functional groups, which are not tolerated under classical Grignard-type conditions.
Y. Huang, Z. Liu, W. H. Liu, Org. Lett., 2023, 25, 4934-4939.

A Pd-catalyzed reaction of water with a diboron compound as the reductant produces clean hydrogen gas under ambient reaction conditions. The B₂Pin₂-H₂O system enables a selective hydrogenation of olefins in the presence of a palladium catalyst.
D. P. Ojha, K. Gadde, K. R. Prabhu, Org. Lett., 2016, 18, 5062-5065.

A B₂Pin₂-assisted copper-catalyzed semihydrogenation of alkynes provides various alkenes in good to excellent yields with Z-selectivity under mild reaction conditions. The present protocol enabled convenient synthesis of deuterium-substituted Z-alkenes using readily available ethanol-d₁ as the deuterium source.
H. Bao, B. Zhou, H. Jin, Y. Liu, J. Org. Chem., 2019, 84, 3579-3589.

Rhodium-catalyzed deoxygenations and borylations of ketones with B₂pin₂ provide alkenes, vinylboronates, and vinyldiboronates. These reactions offer mild reaction conditions, a broad substrate scope, and excellent functional-group compatibility. Mechanistic studies support that the ketones initially undergo a Rh-catalyzed deoxygenation to give alkenes via boron enolate intermediates.
L. Tao, X. Guo, J. Li, R. Li, Z. Lin, W. Zhao, J. Am. Chem. Soc., 2020, 142, 18118-18127.

The combination of B₂pin₂ and KOtBu enables a chemoselective, metal-free reduction of aromatic nitro compounds to the corresponding amines in very good yields in isopropanol. The reaction tolerates various reducible functional groups.
H. Lu, Z. Geng, J. Li, D. Zou, Y. Wu, Y. Wu, Org. Lett., 2016, 18, 2774-2776.

A visible-light-promoted transfer hydrogenation of azobenzenes proceeds smoothly in methanol at ambient temperature in the presence of B₂pin₂ through a radical pathway. The reaction reduces a broad range of azobenzenes to the corresponding hydrazobenzenes in very good yields.
M. Song, H. Zhou, G. Wang, B. Ma, Y. Jiang, J. Yang, C. Huo, X.-C. Wang, J. Org. Chem., 2021, 86, 4804-4811.

An unprecedented nickel-catalyzed reductive borylation of enaminones provides β-ketone boronic esters via a challenging transformation of an alkenyl C(sp²)-N bond. While B₂pin₂ plays a dual role in this process, water serves as the hydrogen source.
X. Li, Z. Chen, Y. Liu, N. Luo, W. Chen, C. Liu, F. Yu, J. Huang, J. Org. Chem., 2022, 87, 10349-10358.

B₂pin₂ mediates a radical cascade cyclization/aromatization reaction of enaminone with pyridine to provide valuable functionalized indolizines under metal-, external oxidant-, and base-free conditions. The reaction is compatible with a broad range of functional groups, such as halogens, π-systems, and heterocycles.
W.-W. Ding, Y. Zhou, S. Song, Z.-Y. Han, Org. Lett., 2022, 24, 7350-7354.