Zn-Catalyzed Regioselective and Chemoselective Reduction of Aldehydes, Ketones and Imines

Abstract

An operationally convenient Zn-catalyzed synthesis of alcohols by the reduction of aldehydes, ketones, and α,β-unsaturated aldehydes/ketones is reported. It is a rare example of using mild and sustainable HBpin as a reductant for catalytic reduction of carbonyl compounds in the absence of acid or base as hydrolysis reagent. The reaction is upscalable and proceeds in high selectivity without the formation of boronate ester by-products, and tolerates sensitive functionalities, such as iodo, bromo, chloro, fluoro, nitro, trifluoromethyl, aminomethyl, alkynyl, and amide. The Zn(OAc)2/HBpin combination has been also proved to be chemoselective for the C=N reduction of imine analogs.

Depolymerization of Polyester and Polycarbonate Waste using HBpin and Cheap Zinc Catalysts

“…Based on experimental results reported on the literature, [41][42][43] the reductive depolymerization of polyesters with the system Zn(OAc) 2 /HBpin should initially involve the formation of the hydride species A, followed by coordination and reduction of the ester monomer to the corresponding boryl acetal intermediate B.…”

BF3-promoted selective catalytic hydroboration of epoxides to primary alcohols

“…In this respect, Zn(OAc) 2 /HBpin catalyzed reduction of carbonyl compounds was realized in the presence of NH 4 Cl/H 2 O, which provided an alternative to acid or base hydrolysis reagents. 40 Furthermore, given the soaring prices of precious metals and heightened environmental concerns, the use of metal-free catalytic systems has been developed significantly. [41][42][43] Lewis acidic boron reagents have emerged as excellent catalysts for metal-free hydroboration.…”

“…In this respect, Zn(OAc) 2 /HBpin catalyzed reduction of carbonyl compounds was realized in the presence of NH 4 Cl/H 2 O, which provided an alternative to acid or base hydrolysis reagents. 40…”

Zinc Catalyzed Hydroboration of Esters and Nitriles with Pinacolborane

“…The metal zinc has gained the attention of various research groups, being earth-abundant, low-cost, and eco-friendly, which can be used as an alternative to noble metal catalysts in various organic transformations. In literature, zinc metal complexes are used as catalysts in the reduction of carbonyl bonds. − Yang and co-workers reported the reduction of esters by employing organozinc (ZnEt 2 ) as a catalyst . Catalysts based on zinc have been used in various organic reactions by researchers such as Negishi, , Fukuyama, Reformatskii reactions, and others. − …”