Catalytic deracemization of α-branched aldehydes is a direct strategy to construct enantiopure α-tertiary carbonyls, which are essential to pharmaceutical applications. Here, we report a photochemical E / Z isomerization strategy for the deracemization of α-branched aldehydes by using simple aminocatalysts and readily available photosensitizers. A variety of racemic α-branched aldehydes could be directly transformed into either enantiomer with high selectivity. Rapid photodynamic E / Z isomerization and highly stereospecific iminium/enamine tautomerization are two key factors that underlie the enantioenrichment. This study presents a distinctive photochemical E / Z isomerization strategy for externally tuning enamine catalysis.

Deracemization, which converts a racemate into its single enantiomer without separation of the intermediate, has gained renewed interest in asymmetric synthesis with its inherent atomic economy and high efficiency. However, this ideal process requires selective energy input and delicate reaction design to surmount the thermodynamical and kinetical constraints. With the rapid development of asymmetric catalysis, many catalytic strategies in concert with exogenous energy input have been exploited to facilitate this nonspontaneous enantioenrichment. In this perspective, we will discuss the basic ideas to accomplish catalytic deracemization, categorized by the three major exogenous energy sources including chemical (redox)-, photo- and mechanical energy from attrition. Emphasis will be given to the catalytic features and the underlying deracemization mechanism together with perspectives on future development.

Catalytic deracemization of α-branched aldehydes represents an unmet challenge with fundamental importance in carbonyl chemistry. In this work, we report a photochemical E/Z isomerization strategy for the deracemization of α-branched aldehydes by using simple aminocatalysts and readily available photosensitizers. Various racemic α-branched aldehydes could be directly transformed into their corresponding single enantiomers in high enantioselectivity. Rapid photodynamic E/Z isomerization and highly stereospecific iminium/enamine tautomerization are two key factors that underlie the highly effective enantio-enrichment. This study presents a distinctive photochemical E/Z isomerizing strategy for externally tuning enamine catalysis.

Catalytic deracemization of α-branched aldehydes represents an unmet challenge with fundamental importance in carbonyl chemistry. In this work, we report a photochemical E/Z isomerization strategy for the deracemization of α-branched aldehydes by using simple aminocatalysts and readily available photosensitizers. Various racemic α-branched aldehydes could be directly transformed into their corresponding single enantiomers in high enantioselectivity. Rapid photodynamic E/Z isomerization and highly stereospecific iminium/enamine tautomerization are two key factors that underlie the highly effective enantio-enrichment. This study presents a distinctive photochemical E/Z isomerizing strategy for externally tuning enamine catalysis.