Catalytic Aerobic Generation of Acyliminium Ions through Electron‐Transfer‐Mediated Carbon‐Carbon Bond Activation

Abstract

Homobenzylic amides and carbamates, upon single-electron oxidation, undergo mesolytic cleavage reactions to form acyliminium ions. Appending nucleophilic groups to these substrates results in cyclization reactions to form N-acylaminals. The Nmethylquinolinium ion that serves as the photooxidant in these reactions can function as a catalyst when dioxygen is introduced into these reactions, representing a unique method for effecting catalytic, aerobic oxidations. Herein we present a full account of our studies on catalytic aerobic electron-transferinitiated cyclization reactions of homobenzylic amides and carbamates, with particular emphasis on the roles of the amide group, the nucleophilic group, and the functionality in the tether in promoting efficient ring constructions and altering reaction mechanisms.

Discovery of an α-Amino C–H Arylation Reaction Using the Strategy of Accelerated Serendipity

“…The C-H bonds adjacent to the nitrogen atom in 8 are weakened by about 40 kcal/mol and so could undergo deprotonation by NaOAc (where OAc is an acetoxy group) to give a-amino radical 9 (19,36). A radical-radical coupling reaction could then unite intermediates 5 and 9, representing the key bond-forming step (15)(16)(17)(18)(19)(37)(38)(39)(40)(41)(42)(43). Elimination of CNfrom 10 would then form the aromatized benzylic amine product 11.…”

Pelagic Fishing at 42,000 Years Before the Present and the Maritime Skills of Modern Humans

“…The C-H bonds adjacent to the nitrogen atom in 8 are weakened by about 40 kcal/mol and so could undergo deprotonation by NaOAc (where OAc is an acetoxy group) to give a-amino radical 9 (19, 36). A radical-radical coupling reaction could then unite intermediates 5 and 9, representing the key bond-forming step (15)(16)(17)(18)(19)(37)(38)(39)(40)(41)(42)(43). Elimination of CNfrom 10 would then form the aromatized benzylic amine product 11.In summary, the concept of accelerated serendipity has been successfully executed, resulting in the discovery of a photoredox amine C-H arylation reaction.…”

Oxidative Cyclorelease from Soluble Polymeric Supports

“…Thus only substrates in which the requisite functional groups for the cyclization event have been successfully installed will be released from the polymer, thereby providing an editing mechanism that facilitates separation at the end of the sequence. Herein we report that substrates for electron transfer initiated cyclization (ETIC) reactions can be synthesized on soluble polymeric supports, and that cyclorelease reactions occur efficiently upon single electron oxidation to provide products of high purity. Additionally we show that single electron oxidation is an excellent trigger for traceless liberation of aldehydes and ketones from polymeric supports even in the absence of an internal nucleophile.…”

“…(5) Molecular weight can be controlled rationally by adjusting metathesis catalyst loading or employing a different catalyst in order to alter the solubility properties of the polymer to suit the needs of a particular class of substrate. Based on structure−reactivity studies conducted in our labs relating the effects of arene substitution to the propensity of intermediate radical cations to fragment, 10b, we chose to attach the polymer to the substrates through an ether linkage at the para position of the arene.

3 ROMP approach to oligonorbornenes.

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