Mechanistic Investigation of the Pseudo-Halogen Effect in Enantioselective Aminocatalyzed [6 + 4] and [10 + 6] Cycloadditions: Enabling Unique Favorskii-Like Rearrangements.

A mechanistic investigation into the novel combination of the -halogen effect with enantioselective aminocatalysis unravels the mechanistic intricacies of [6 + 4] and [10 + 6] higher-order cycloadditions and the succeeding new Favorskii-like rearrangements. By introducing the OTf-group into the tropone framework, it can serve both as an activator for the cycloaddition and as a proficient leaving group within the corresponding cycloadduct, thus enabling unprecedented ring-contracting Favorskii-like rearrangements. Integrating the -OTf group creates an electron-deficient 6π-component leveraging the -halogen effect by enhancing the polarization and introducing new strategic interaction points.

Enantioconvergent 6π Electrocyclization Enabled by Photoredox Racemization.

This study presents a novel photoredox-enabled enantioconvergent catalytic strategy used to construct chiral 2-1,3-benzoxazines via an unprecedented oxa-6π electrocyclization utilizing racemic α-substituted glycinates as substrates. The approach leverages a cobalt-based chiral Lewis acid catalyst, which promotes the transformation under thermal or photoredox conditions. While the thermal reaction selectively converts only the ()-configured glycinates into enantioenriched 2-1,3-benzoxazines (up to 96:4 e.

Asymmetric Organocatalyzed Cascade Reactions─Merging the -Halogen and Halogen Effect with Dienamine Catalysis.

The combination of asymmetric organocatalysis with the ()-halogen effect enables the formation of chiral norcarane scaffolds in high yields and selectivities (up to 92% yield, >99% ee, and >95:5 d.r.).