Cover Picture: Catalytic Reductions Without External Hydrogen Gas: Broad Scope Hydrogenations with Tetrahydroxydiboron and a Tertiary Amine (Adv. Synth. Catal. 1/2020)

Abstract

The inside cover picture, designed by Lakshman and co‐workers, illustrates a diverse set of hydrogenations that can be conducted without use of external hydrogen gas (compressed gas). 4‐Methylmorpholine (NMM), tetrahydroxydiboron [B2(OH)4], and 5% Pd on charcoal work in concert to cause reductions of aryl halides and triflates, alkenes, alkynes, aldehydes, and azides, as well as cleavage of benzylic ethers and N‐Cbz groups. Based on the mechanistic knowledge gained in the study, aromatic deuteriations have also been accomplished using N,N‐bis(methyl‐d3)pyridin‐4‐amine (DMAP‐d6) and B2(OD)4. H2 gas appears to be formed in these reactions and this has been observed by 1H NMR and GC analysis. Details of this work can in found in the full paper on pages 166–176 (K. A. Korvinson, H. K. Akula, C. T. Malinchak, D. Sebastian, W. Wei, T. A. Khandaker, M. R. Andrzejewska, B. Zajc, M. K. Lakshman, Adv. Synth. Catal. 2020, 362, 166–176; DOI: 10.1002/adsc.201901099).

Mechanistic insights into H2 evolution via water splitting at the expense of B2(OH)4: a theoretical study

“…43,44 Typically, most hydrogen-rich boron hydrides (such as sodium borohydride, [45][46][47][48][49] ammonia borane, [50][51][52][53][54] and dimethylaminoborane [55][56][57][58][59] ) catalyzed by metal nanoparticles generate H 2 with only one H atom supplied by water and the other one by hydrogen-rich boron hydrides. Since 2020, our group successively reported highly efficient H 2 production upon water splitting at the expense of B 2 (OH) 4 (eqn (1)), which is a common borylation reagent [60][61][62][63][64][65][66][67][68] catalysed by acid, base or metal nanoparticles. 69,70 Experiments using D 2 O in place of H 2 O including the kinetic isotope effect and tandem reaction have confirmed that both H atoms of produced H 2 are only provided by water.…”