Catalytic, contra-Thermodynamic Alkene Isomerization

The positional isomerization of C–C double bonds is a powerful strategy for the interconversion of alkene regioisomers. However, existing methods provide access to thermodynamically more stable isomers from less stable starting materials. Here we report the discovery of a dual catalyst system that promotes contra-thermodynamic positional alkene isomerization under photochemical irradiation, providing access to terminal alkene isomers directly from conjugated, internal alkene starting materials. The utility of the method is demonstrated in the deconjugation of diverse electron rich/poor alkenes and through strategic application to natural product synthesis. Mechanistic studies are consistent with a regiospecific bimolecular homolytic substitution (SH2') mechanism proceeding through an allyl-cobaloxime intermediate.

The antioxidant activity of polysulfides: it's radical!

Sulfurized olefins (polysulfides) containing four (or more) sulfur atoms react efficiently with peroxyl radicals by homolytic substitution, accounting for their primary antioxidant activity.

The Invention of New Methodologies: An Opportunity for Dating Natural Products

This Account surveys almost two decades of methodological developments and their straightforward applications to the total synthesis of simple natural products. The main directions covered include radical chemistry and cascades, electrophilic catalysis based on coinage metals, and asymmetric synthesis based on bis(sulfoxides) auxiliaries.1 Introduction2 Radical Cascades2.1 N-Cyanamides2.2 Homolytic Substitution at Sulfur Atom to Give Sultines3 Electrophilic Catalysis Based on Platinum(II) and Gold(I) Complexes4 From Alkylydene Bis(sulfoxides) to Chiral Carboxylic Acids5 Conclusion and Perspectives