Achieving elusive transformations with organocatalysis: direct $\beta $-carbon activation of saturated carbonyl compounds

Abstract

Direct β -carbon activation of saturated carbonyl compounds for carrying out fast forward β -functionalization has been one of the most difficult to achieve tasks in catalysis. In the past few years, this challenging issue has attracted considerable attention among the chemical community that has led to fruitful developments to accomplish this elusive transformation. In this short review, we highlight recent developments for direct β -carbon functionalization of saturated carbonyl compounds based on conceptually new methods including oxidative enamine catalysis, N -heterocyclic carbene (NHC)-assisted catalysis, and photoredox catalysis.

Catalytic Asymmetric Oxidative Enamine Transformations

“…In 2009, the group of Wang and Li first introduced an amine catalyst in a Saegusa oxidation system, effectively oxidizing 3-phenylpropionaldehyde derivatives to its α,β-unsaturated analogue . Two years later, the same group reported a tandem β-functionalization of saturated aldehydes by oxidative iminium catalysis.…”

“…The typical enamine catalytic process involves the coupling of a nucleophilic enamine intermediate with an electrophile for C–C/C–X bond formations (Scheme ). Beyond its well-defined nucleophilic feature, enamine is also rich in redox properties and could be readily oxidized to an electron-deficient structure upon a single-electron transfer or electron/proton transfer process. , …”