Methodologies and Strategies for Selective Borylation of C–Het and C–C Bonds

Chemical Reviews, Год журнала: 2020, Номер 120(15), С. 7348 - 7398

Опубликована: Июнь 29, 2020

Organoborons have emerged as versatile building blocks in organic synthesis to achieve molecular diversity and carboxylic acid bioisosteres with broad applicability drug discovery. Traditionally, these compounds are prepared by the substitution of Grignard/lithium reagents electrophilic boron species Brown hydroboration. Recent developments provided new routes for efficient preparation organoborons applying reactions using chemical feedstocks leaving groups. As compared previous methods that used halides (I, Br, Cl), direct borylation less reactive C–Het C–C bonds has become highly important get efficiency functional-group compatibility. This Review aims provide a comprehensive overview this topic, including (1) C–F bond borylation, (2) C–O (3) C–S (4) C–N (5) borylation. Considerable attention is given strategies mechanisms involved. We expect will inspire chemists discover more transformations expand field.

Язык: Английский

---

Alkoxy Radicals See the Light: New Paradigms of Photochemical Synthesis

Chemical Reviews, Год журнала: 2021, Номер 122(2), С. 2429 - 2486

Опубликована: Окт. 6, 2021

Alkoxy radicals are highly reactive species that have long been recognized as versatile intermediates in organic synthesis. However, their development has impeded due to a lack of convenient methods for generation. Thanks advances photoredox catalysis, enabling facile access alkoxy from bench-stable precursors and free alcohols under mild conditions, research interest this field renewed. This review comprehensively summarizes the recent progress radical-mediated transformations visible light irradiation. Elementary steps radical generation either or central reaction development; thus, each section is categorized discussed accordingly. Throughout review, we focused on different mechanisms well impact synthetic utilizations. Notably, catalytic abundant still early stage, providing intriguing opportunities exploit diverse paradigms.

Язык: Английский

---

Photoinduced Borylation for the Synthesis of Organoboron Compounds

Chemical Reviews, Год журнала: 2021, Номер 121(7), С. 3561 - 3597

Опубликована: Фев. 17, 2021

Organoboron compounds have important synthetic value and can be applied in numerous transformations. The development of practical convenient ways to synthesize boronate esters has thus attracted significant interest. Photoinduced borylations originated from stoichiometric reactions alkanes arenes with well-defined metal–boryl complexes. Now, photoredox-initiated borylations, catalyzed by either transition metal or organic photocatalysts, photochemical high efficiency become a burgeoning area research. In this Focus Review, we summarize research on photoinduced especially emphasizing recent developments trends. This includes the borylation arenes, alkanes, aryl/alkyl halides, activated carboxylic acids, amines, alcohols, so based catalysis, metal-free organocatalysis, direct activation. We focus reaction mechanisms involving single-electron transfer, triplet-energy other radical processes.

Язык: Английский

---

Reductive Cross-Coupling of Unreactive Electrophiles

Accounts of Chemical Research, Год журнала: 2022, Номер 55(17), С. 2491 - 2509

Опубликована: Авг. 11, 2022

ConspectusTransition-metal-catalyzed reductive coupling of electrophiles has emerged as a powerful tool for the construction molecules. While major achievements have been made in field cross-couplings between organic halides and pseudohalides, an increasing number reports demonstrates reactions involving more readily available, low-cost, stable, but unreactive electrophiles. This account summarizes recent results our laboratory focusing on this topic. These findings typically include deoxygenative C–C alcohols, alkylation alkenyl acetates, C–Si chlorosilanes, C–Ge chlorogermanes.The alcohols with is synthetically appealing, potential chemistry remains to be disclosed. Our initial study focused reaction allylic aryl bromides by combination nickel Lewis acid catalysis. method offers selectivity that opposite classic Tsuji–Trost reactions. Further investigation benzylic led foundation dynamic kinetic cross-coupling strategy applications nickel-catalyzed arylation cobalt-catalyzed enantiospecific alkenylation alcohols. The titanium catalysis was later established produce carbon radicals directly from unactivated tertiary via C–OH cleavage. development their fragments delivers new methods all-carbon quaternary centers. shown high functionalization leaving primary secondary intact. Alkenyl acetates are inexpensive, environmentally friendly considered most attractive reagents. benzyl ammoniums alkyl mild approaches conversion ketones into aliphatic alkenes.Extensive studies enabled us extend cross-electrophile silicon germanium chemistry. harness ready availability chlorosilanes chlorogermanes suffer challenge low reactivity toward transition metals. Under catalysis, broad range couple well vinyl- hydrochlorosilanes. use partners formation functionalized alkylsilanes. seems less substrate-dependent, various common aryl, alkenyl, In general, functionalities such Grignard-sensitive groups (e.g., acid, amide, alcohol, ketone, ester), acid-sensitive ketal THP protection), fluoride chloride, bromide, tosylate mesylate, silyl ether, amine tolerated. provide access organosilicon organogermanium compounds, some which challenging obtain otherwise.

Язык: Английский

---

Diastereoselective Synthesis of Aryl C‐Glycosides from Glycosyl Esters via C−O Bond Homolysis

Angewandte Chemie International Edition, Год журнала: 2021, Номер 60(17), С. 9433 - 9438

Опубликована: Янв. 15, 2021

C-aryl glycosyl compounds offer better in vivo stability relative to O- and N-glycoside analogues. glycosides are extensively investigated as drug candidates applied chemical biology studies. Previously, were derived from lactones, glycals, stannanes, halides, via methods displaying various limitations with respect the scope, functional-group compatibility, practicality. Challenges remain synthesis of nucleosides 2-deoxysugars easily accessible carbohydrate precursors. Herein, we report a cross-coupling method prepare heteroaryl glycosides, including 2-deoxysugars, esters bromoarenes. Activation substrates leverages dihydropyridine (DHP) an activating group followed by decarboxylation generate radical C-O bond homolysis. This strategy represents new means activate alcohols partner. The convenient preparation their exemplifies potential this medicinal chemistry.

Язык: Английский

---

Nontraditional Fragment Couplings of Alcohols and Carboxylic Acids: C(sp³)–C(sp³) Cross-Coupling via Radical Sorting

Journal of the American Chemical Society, Год журнала: 2022, Номер 144(14), С. 6185 - 6192

Опубликована: Март 30, 2022

Alcohols and carboxylic acids are among the most commercially abundant, synthetically versatile, operationally convenient functional groups in organic chemistry. Under visible light photoredox catalysis, these native synthetic handles readily undergo radical activation, resulting open-shell intermediates can subsequently participate transition metal catalysis. In this report, we describe C(sp3)–C(sp3) cross-coupling of alcohols through dual combination N-heterocyclic carbene (NHC)-mediated deoxygenation hypervalent iodine-mediated decarboxylation. This mild practical Ni-catalyzed radical-coupling protocol was employed to prepare a wide array alkyl–alkyl cross-coupled products, including highly congested quaternary carbon centers from corresponding tertiary or acids. We demonstrate applications methodology alcohol C1-alkylation formal homologation, as well late-stage functionalization drugs, natural biomolecules.

Язык: Английский

---

Visible Light-Induced Borylation of C–O, C–N, and C–X Bonds

Journal of the American Chemical Society, Год журнала: 2020, Номер 142(3), С. 1603 - 1613

Опубликована: Янв. 3, 2020

Boronic acids are centrally important functional motifs and synthetic precursors. Visible light-induced borylation may provide access to structurally diverse boronates, but a broadly efficient photocatalytic method that can effect of wide range substrates, including strong C–O bonds, remains elusive. Herein, we report general, metal-free visible platform enables electron-rich derivatives phenols anilines, chloroarenes, as well other haloarenes. The reaction exhibits excellent group tolerance, demonstrated by the complex substrates. Remarkably, is catalyzed phenothiazine, simple organic photocatalyst with MW < 200 mediates previously unachievable single electron reduction phenol potentials negative approximately – 3 V versus SCE proton-coupled transfer mechanism. Mechanistic studies point crucial role photocatalyst–base interaction.

Язык: Английский

---

Generation of non-stabilized alkyl radicals from thianthrenium salts for C–B and C–C bond formation

Nature Communications, Год журнала: 2021, Номер 12(1)

Опубликована: Июль 26, 2021

Abstract Sulfonium salts bearing a positively charged sulfur atom with three organic substituents have intrigued chemists for more than century their unusual structures and high chemical reactivity. These compounds are known to undergo facile single-electron reduction emerge as valuable alternative source of aryl radicals synthesis. However, the generation non-stabilized alkyl from sulfonium has been challenge several decades. Here we report treatment S -(alkyl) thianthrenium generate key intermediates granting controlled selective outcome ensuing reactions under mild photoredox conditions. The value these reagents demonstrated through efficient construction alkylboronates other transformations, including heteroarylation, alkylation, alkenylation, alkynylation. developed method is practical, provides opportunity convert C–OH bond C–B C–C bonds.

Язык: Английский

---

Progress in Photoinduced Radical Reactions using Electron Donor‐Acceptor Complexes

Asian Journal of Organic Chemistry, Год журнала: 2021, Номер 10(4), С. 711 - 748

Опубликована: Фев. 11, 2021

Abstract Photocatalyzed organic synthesis transformation is a remarkable green synthetic strategy because of the advantages operational simplicity, high chemoselectivities, cheap, and environmental benignancy, along with extensive applications in fields organic, pharmaceutical functional material chemistry. Generally, photoredox catalysts or photosensitizers are necessary for generation their excited states to perform successive oxidative reductive reactions through single electron transfer (SET) energy (ET) process. Furthermore, exploration colored donor‐acceptor (EDA) complex charge (CT) between an electron‐rich electron‐poor substrate provides chance deliver intermediate under irradiation light, resulting formation radical activate species induce various reactions. These were performed without need any external photocatalysts mild reaction conditions. Herein, this review focuses on recent progress photoinduced addition reactions, borylations, radical‐radical cross‐coupling degradation cascade cyclization via EDA complexes. We highlight these novel methodologies applications, as well mechanisms. This will help provide references medicinal chemists who charmed by photochemical transformations based

Язык: Английский

---

Halogen-atom and group transfer reactivity enabled by hydrogen tunneling

Science, Год журнала: 2022, Номер 377(6612), С. 1323 - 1328

Опубликована: Сен. 15, 2022

The generation of carbon radicals by halogen-atom and group transfer reactions is generally achieved using tin silicon reagents that maximize the interplay enthalpic (thermodynamic) polar (kinetic) effects. In this work, we demonstrate a distinct reactivity mode enabled quantum mechanical tunneling uses cyclohexadiene derivative γ-terpinene as abstractor under mild photochemical conditions. This protocol activates alkyl aryl halides well several alcohol thiol derivatives. Experimental computational studies unveiled noncanonical pathway whereby cyclohexadienyl radical undergoes concerted aromatization or abstraction through an effective H atom. activation mechanism seemingly thermodynamically kinetically unfavorable but rendered feasible tunneling.

Язык: Английский

---