Amine-Boranes as Transfer Hydrogenation and Hydrogenation Reagents: A Mechanistic Perspective.

Amine-Boranes as Transfer Hydrogenation and Hydrogenation Reagents: A Mechanistic Perspective.
Angew Chem Int Ed Engl. 2020 Sep 16;:
Authors: Lau S, Gasperini D, Webster RL
Abstract
Transfer hydrogenation (TH) has historically been dominated by Meerwein-Ponndorf-Verley (MPV) reactions. However, with growing interest in amine-boranes, not least ammonia-borane (H 3 N·BH 3 ), as potential hydrogen storage materials, these compounds have also started to emerge as an alternative reagent in TH reactions. In this review we discuss recent literature into TH chemistry using H 3 N·BH 3 and their analogues (amine-boranes and metal amidoboranes) as sacrificial hydrogen donors. By analyzing the mechanisms operating three distinct pathways were considered: ( i ) classical TH, ( ii ) non-classical TH, and ( iii ) hydrogenation. Simple experimental mechanistic probes can be employed to distinguish which pathway is operating and computational analysis can corroborate or discount mechanisms including rationalizing selectivity observed under certain conditions. We find that the pathway in operation can be perturbed by changing the temperature, solvent, amine-borane or even the substrate used in the system, and subsequently assignment of the mechanism can become non-trivial. Therefore, by examining the mechanism of these reactions, we anticipate this will aid in future reaction development in the area of TH using amine-boranes.
PMID: 32935898 ...

Source: Angewandte Chemie - September 15, 2020 Category: Chemistry Authors: Lau S, Gasperini D, Webster RL Tags: Angew Chem Int Ed Engl Source Type: research