Neutral organic super electron donors made catalytic

Neutral organic super electron donors (SEDs) display impressive reducing power but, until now, it has not been possible to use them catalytically in radical chain reactions. This is because, following electron transfer, these donors form persistent radical cations that trap substrate-derived radicals. This paper unlocks a conceptually new approach to super electron donors that overcomes this issue, leading to the first catalytic neutral organic super electron donor

Photochemical generation of radicals from alkyl electrophiles using a nucleophilic organic catalyst

Chemists extensively use free radical reactivity for applications in organic synthesis, materials science, and life science. Traditionally, generating radicals requires strategies that exploit the bond dissociation energy or the redox properties of the precursors. Here, we disclose a photochemical catalytic approach that harnesses different physical properties of the substrate to form carbon radicals. We use a nucleophilic dithiocarbamate anion catalyst, adorned with a well-tailored chromophoric unit, to activate alkyl electrophiles via an S N 2 pathway. The resulting photon-absorbing intermediate affords radicals upon homolytic cleavage induced by visible light. This catalytic S N 2-based strategy, which exploits a fundamental mechanistic process of ionic chemistry, grants access to open-shell intermediates from a variety of substrates that would be incompatible with or inert to classical radical-generating strategies. We also describe how the method’s mild reaction conditions and high functional group tolerance could be advantageous for developing C–C bond-forming reactions, for streamlining the preparation of a marketed drug, for the late-stage elaboration of biorelevant compounds and for enantioselective radical catalysis

Causation in a cascade: the origins of selectivities in intramolecular nitrone cycloadditions

The factors controlling chemo-, regio-, and stereoselectivity in a cascade of reactions starting from a bis(cyanoalkenyl)oxime and proceeding via nitrone cycloadditions have been unraveled through a series of density functional theory calculations with several different functionals. Both kinetic and thermodynamic control of the reaction cascade are important, depending upon the conditions. Kinetic control was analyzed by the distortion/interaction model and found to be dictated by differences in distortions of the cycloaddends in the transition states. A new mechanism competing with that originally proposed in the application of these reactions to the histrionicotoxin synthesis was discovered in these studies