Borinic Acid Catalysed Reduction of Tertiary Amides with Hydrosilanes: A Mild and Chemoselective Synthesis of Amines

Abstract

A reduction of various aryl, alkyl, and α,β-unsaturated amides with phenylsilane, catalysed by a borinic acid, is reported. The unprecedented reaction was carried out under very mild conditions and led to useful amines. Furthermore, the reaction tolerates a variety of functional groups. Initial investigations implicated that an intermediate diarylhydroborane is involved in the reaction mechanism.

Borinic Acid Mediated Hydrosilylations: Reductions of Carbonyl Derivatives

“…Since this important discovery, boron‐based catalysts were used as Si–H bond activators in many chemical transformations . Our group recently developed 2‐chlorophenylborinic acid 1a for the challenging catalysis of amide and phosphine oxide reductions . Noticeable, lower temperature was used and high chemoselectivity was achieved when compared to B(C 6 F 5 ) 3 (Scheme ).…”

A Manganese Pre‐Catalyst: Mild Reduction of Amides, Ketones, Aldehydes, and Esters

“…It is worthy of mention that in the absence of photochemical activation, the reduction of simple tertiary amides at room temperature by use of a3 dt ransition-metal catalyst is, to the best of our knowledge,unknown. [21] In this context, we subsequently examined the ability of 1 to effect such unprecedented transformations (2 mol % 1,2 5 8 8C, 18 h; Figure 2). We were pleased to observe that for several of the tertiary amide substrates under investigation herein, high conversion into the desired tertiary amine was achieved under room-temperature conditions,i ncluding the formation of Nbenzylpiperidine (2a), N-benzylmorpholine (2f), tribenzylamine (2h), and N,N-dimethylbenzylamine (2l).…”

Selective C−O Bond Cleavage of Sugars with Hydrosilanes Catalyzed by Piers’ Borane Generated In Situ

“…Interestingly, it was observed that 1 a in the presence of excess PhMe 2 SiH was slowly converted to (C 6 F 5 ) 2 BH 2 (Piers’ borane), with the corresponding 19 F NMR signals at δ −131.6, −149.0, and −160.5 ppm in CDCl 3 . The transformation of 1 into 2 was highly accelerated by employing more reactive silanes, such as PhSiH 3 (20 equiv) or TMDS (200 equiv), resulting in quantitative formation of 2 within 10 min at 25 °C (see the Supporting Information) …”