Minimization of Back‐Electron Transfer Enables the Elusive sp³ C−H Functionalization of Secondary Anilines

Angewandte Chemie International Edition, Год журнала: 2021, Номер 60(14), С. 7669 - 7674

Опубликована: Янв. 18, 2021

Abstract Anilines are some of the most used class substrates for application in photoinduced electron transfer. N,N‐Dialkyl‐derivatives enable radical generation α to N‐atom by oxidation followed deprotonation. This approach is however elusive monosubstituted anilines owing fast back‐electron transfer (BET). Here we demonstrate that BET can be minimised using photoredox catalysis presence an exogenous alkylamine. synergistically aids aniline SET and then accelerates following In this way, α‐anilinoalkyl radicals now possible these species a general sense achieve divergent sp 3 C−H functionalization.

Язык: Английский

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Reductive Arylation of Aliphatic and Aromatic Aldehydes with Cyanoarenes by Electrolysis for the Synthesis of Alcohols

Organic Letters, Год журнала: 2021, Номер 23(9), С. 3472 - 3476

Опубликована: Апрель 16, 2021

An electroreductive arylation reaction of aliphatic and aromatic aldehydes as well ketones with electro-deficient (hetero)arenes is described. A variety cyano(hetero)arenes carbonyl compounds, especially aldehydes, have been examined, providing secondary tertiary alcohols in moderate to good yields. Mechanistic studies, including cyclic voltammetry (CV), electron paramagnetic resonance (EPR), divided-cell experiments, support the generation ketyl radicals persistent heteroaryl radical anions via cathodic reduction followed by radical-radical cross-coupling.

Язык: Английский

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Merging Carbonyl Addition with Photocatalysis

Accounts of Chemical Research, Год журнала: 2022, Номер 55(8), С. 1135 - 1147

Опубликована: Март 31, 2022

The carbonyl group stands as a fundamental scaffold and plays ubiquitous role in synthetically important chemical reactions both academic industrial contexts. Venerable transformations, including the aldol reaction, Grignard Wittig Nozaki-Hiyama-Kishi constitute vast empowering synthetic arsenal. Notwithstanding, two-electron mechanisms inherently confine breadth of accessible reactivity topological patterns.Fostered by rapid development photoredox catalysis, combing well-entrenched addition radicals can harness several unique increasingly sustainable transformations. In particular, unusual carbon-carbon carbon-heteroatom disconnections, which are out reach chemistry, be conceived. To meet this end, novel strategy toward utilization simple compounds intermolecular radical acceptors was developed. reaction is enabled visible-light photoredox-initiated hole catalysis. situ Brønsted acid activation moiety prevents β-scission from occurring. Furthermore, regioselective alkyl obviates use metals, ligands, or additives, thus offering high degree atom economy under mild conditions. On basis same concept work Schindler co-workers, carbonyl-olefin cross-metathesis, induced visible light, has also been achieved, leveraging Prins-elimination sequence.Recently, dual chromium catalysis developed us Kanai, complementary approach to revered reaction. Leveraging intertwined synergy between light metal, radical-to-polar crossover transformations eminent molecular motifs have Reactions such redox-neutral allylation aldehydes alkylation harvest power enable catalytic metal. Overall, exquisite levels diastereoselectivity enforced via highly compact transition states. Other examples, dialkylation 1,3-dienes propargylation portray versatile combination multicomponent coupling endeavors. Highly valuable motifs, commonly occur complex drug natural product architectures, now accessed single operational step. Going beyond addition, seminal contributions Fagnoni MacMillan preconized photocatalytic HAT-based acyl formation key aldehyde valorization strategy. Our articulated concept, carboxy hydrogen abstractors regio- chemoselective alkynylation trifluoromethylthiolation.This Account, narrative our others' at interface radical-based photochemistry, aims provide core guiding foundations disruptive developments. We envisage that extending crossovers manifolds, taming less-activated carbonyls, processes, merging electron steps with energy-transfer events will propel breakthroughs near future.

Язык: Английский

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Photoinduced 1,2-dicarbofunctionalization of alkenes with organotrifluoroborate nucleophilesviaradical/polar crossover

Chemical Science, Год журнала: 2021, Номер 12(26), С. 9189 - 9195

Опубликована: Янв. 1, 2021

Alkene 1,2-dicarbofunctionalizations are highly sought-after transformations as they enable a rapid increase of molecular complexity in one synthetic step. Traditionally, these conjunctive couplings proceed through the intermediacy alkylmetal species susceptible to deleterious pathways including β-hydride elimination and protodemetalation. Herein, an intermolecular 1,2-dicarbofunctionalization using alkyl N-(acyloxy)phthalimide redox-active esters radical progenitors organotrifluoroborates carbon-centered nucleophiles is reported. This redox-neutral, multicomponent reaction postulated photochemical radical/polar crossover afford key carbocation that undergoes subsequent trapping with organoboron accomplish carboallylation, carboalkenylation, carboalkynylation, carboarylation alkenes regio- chemoselective control. The mechanistic intricacies this difunctionalization were elucidated Stern-Volmer quenching studies, quantum yield measurements, experiments ionic intermediates.

Язык: Английский

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Convergent Synthesis of 1,4-Dicarbonyl Z-Alkenes through Three-Component Coupling of Alkynes, α-Diazo Sulfonium Triflate, and Water

Journal of the American Chemical Society, Год журнала: 2022, Номер 144(11), С. 4952 - 4965

Опубликована: Март 11, 2022

We report a general protocol for the convergent synthesis of 1,4-dicarbonyl Z-alkenes form alkynes using α-diazo sulfonium triflate and water. The C═O, C═C, C–H bonds are formed under mild conditions with wide range functional groups tolerated. reaction exhibits excellent Z-selectivity complete regioselectivity. resulting can smoothly undergo follow-up conversion to variety heteroaromatic scaffolds. Moreover, also provides facile access corresponding deuterated heteroarenes high level deuterium incorporation (90–97% D-inc.) by directly D2O, thus rendering method highly valuable. comprehensive mechanistic studies indicate that free carbyne radical intermediate is via photocatalytic single electron transfer process, KH2PO4 plays crucial role in significant improvements on yield selectivity based density-functional theory calculations, providing new direction coupling reactions diazo compounds.

Язык: Английский

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