Lewis Base–Boryl Radicals Enabled Borylation Reactions and Selective Activation of Carbon–Heteroatom Bonds

Accounts of Chemical Research, Journal Year: 2022, Volume and Issue: 56(2), P. 169 - 186

Published: Dec. 26, 2022

ConspectusThe past decades have witnessed tremendous progress on radical reactions. However, in comparison with carbon, nitrogen, oxygen, and other main group element centered radicals, the synthetic chemistry of boron radicals was less studied, mainly due to high electron-deficiency instability such 3-center-5-electron species. In 1980s, Roberts co-workers found that coordination a Lewis base (amines or phosphines) center could form 4-center-7-electron boryl (Lewis base-boryl LBRs) are be more stable. only limited applications were developed. 2008, Curran achieved breakthrough discovery N-heterocyclic carbene (NHC) which enable range reduction polymerization Despite these exciting findings, powerful valuable LBRs would expected, given structures reactivities easily modulated, provide ample opportunities discover new this Account, summary our key contributions LBR-enabled borylation reactions selective activation inert carbon-heteroatom bonds will presented.Organoboron compounds shown versatile chemical society, their syntheses rely principally ionic The development mechanistically different allows synthesizing products inaccessible by traditional methods. For purpose, we progressively developed series NHC-boryl mediated chemo-, regio-, stereoselective alkenes alkynes, wide variety structurally diverse organoboron molecules successfully prepared. utility borylated also demonstrated. Furthermore, disclosed photoredox protocol for oxidative generation enabled useful defluoroborylation arylboration reactions.Selective bond is an ideal way convert simple starting materials value-added products, while cleavage bonds, particular chemoselectivity control when multiple identical present similar environments, remains long-standing challenge. We envisaged finely tuning properties might solution address Recently, 4-dimethylaminopyridine (DMAP)-boryl promoted sequential C-F functionalization trifluoroacetic acid derivatives, α-C-F selectively snipped via spin-center shift mechanism. This strategy enables facile conversion abundantly available highly mono- difluorinated molecules. Encouraged finding, further three-step sequence construct all-carbon quaternary centers from trichloromethyl groups, where three C-Cl cleaved rational choice suitable precursors each step. dehydroxylative alkylation α-hydroxy carboxylic derivatives achieved, allowing efficient some biomass platform value products.

Language: Английский

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Iron‐Catalyzed Silylation and Spirocyclization of Biaryl‐Ynones: A Radical Cascade Process toward Silylated Spiro[5.5]trienones

Advanced Synthesis & Catalysis, Journal Year: 2022, Volume and Issue: 364(9), P. 1537 - 1542

Published: March 11, 2022

Abstract Iron‐catalyzed cascade silyl radical addition/6‐ exo ‐trig cyclization/dearomatization of biaryl ynones has been developed. This approach uses silane as the precursor well silylation reagent, 1,10‐phenanthroline ligand, and tert ‐butyl hydroperoxide (TBHP) oxidant. By employing this tandem process, a series silylated spiro[5.5]trienones were prepared. magnified image

Language: Английский

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Cp₂Fe Mediated Electrochemical Synthesis of Phosphonylated Spirocyclic Indolines via Dearomatization of Indoles

Organic Letters, Journal Year: 2023, Volume and Issue: 25(21), P. 3956 - 3960

Published: May 18, 2023

A general and robust strategy for the synthesis of phosphonylated spirocyclic indolines has been developed through Cp2Fe-catalyzed electrochemical dearomaztizaion indoles, which proven challenging to achieve via chemical oxidants. range 3,3-spiroindolines were obtained in moderate good yields with excellent diastereoselectivities. The synthetic application was further illustrated by its easy scalability antitumor activity product.

Language: Английский

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Ynones in dearomative spirocyclisation processes; a review

Tetrahedron Chem, Journal Year: 2024, Volume and Issue: 9, P. 100055 - 100055

Published: Jan. 14, 2024

This review concentrates on our research into the discovery of novel ynone-based dearomative spirocyclisation processes, whilst placing new chemistry context existing knowledge. The genesis programme, development efficient synthetic routes to prepare natural products spirobacillene A (1) and B (2), utilised indole ynones. stimulated a much wider study explore reactivity ynones in processes more generally. Routes generate wide range spirocycles were subsequently developed, with reactions tethered indoles, benzofurans, benzisoxazoles, pyrroles, pyridines, isoquinolines, pyrazines, cyclic ketimines, anisoles all discussed herein, these initiated by catalytic Ag(I), Cu(II), Pd(0), photolysis many other reagents. Asymmetric variants some are also discussed, as is further elaboration spirocyclic give carbazoles, quinolones, polycycles useful building blocks. Finally, applications methodology product synthesis (e.g. A, lasubine II indolizidine 209D) described.

Language: Английский

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Visible-Light-Induced Cascade Cyclization of 3-(2-(Ethynyl)phenyl)quinazolinones to Phosphorylated Quinolino[2,1-b]quinazolinones

Organic Letters, Journal Year: 2022, Volume and Issue: 24(43), P. 7912 - 7917

Published: Oct. 21, 2022

3-(2-(Ethynyl)phenyl)quinazolinones were designed and synthesized as a class of novel efficient skeletons for phosphorylation/cyclization reactions. Under visible light irradiation, series phosphorylated quinolino[2,1-b]quinazolinones (35 examples, up to 87% yield) first from 3-(2-(ethynyl)phenyl)quinazolinones diarylphosphine oxides by using 4CzIPN photocatalyst under mild conditions. This reaction was also applicable sunlight irradiation. Moreover, the efficiency could be significantly improved continuous-flow

Language: Английский

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Indolyl‐Ynones: Building Blocks for Molecular Diversity

Advanced Synthesis & Catalysis, Journal Year: 2024, Volume and Issue: 366(5), P. 1044 - 1058

Published: Jan. 12, 2024

Abstract This review centers on the synthetic strategies employed with indolyl‐ynones. Indolyl‐ynone, owing to its highly reactive ynone moiety, frequently partakes in dearomatizing spirocyclization reactions and subsequent rearrangement when subjected various reaction conditions. Hence, heterocycles such as densely functionalized spiroindolenines, carbazoles, quinolines carbo‐and hetero‐cycle substituted indoles are synthesized from In addition this, versatile spirocyclic indole scaffold exhibits capability produce tetracyclic polyclic structures through intricate skeletal processes. Moreover, total synthesis of natural products using indolyl‐ynone moiety was also compiled this review.

Language: Английский

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Photoredox-Catalyzed Strain-Release-Driven Synthesis of Functionalized Spirocyclobutyl Oxindoles

Organic Letters, Journal Year: 2024, Volume and Issue: 26(30), P. 6396 - 6401

Published: July 24, 2024

Spirocyclobutyl oxindoles have garnered substantial attention in drug discovery and pharmaceuticals owing to their wide range of biological activities. Strain-release small-ring compounds is a powerful strategy enable efficient access complex molecules. In this study, we successfully realized photoredox-catalyzed strain-release radical spirocyclization approach attain functionalized spirocyclobutyl oxindoles. A diverse array radicals, such as sulfonyl, phosphonyl, trifluoromethyl, were added efficiently the strained C-C σ-bond bicyclobutanes (BCBs) afford library Furthermore, obtained products could be transformed into valuable building blocks. The observed reactivity selectivity been rationalized based on density functional theory calculations.

Language: Английский

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Investigation of Dearomatizing Spirocyclizations and Spirocycle Functionalization En Route to Spirocalcaridines A and B—Some Trials and Tribulations

Molecules, Journal Year: 2025, Volume and Issue: 30(5), P. 1143 - 1143

Published: March 3, 2025

Spirocalcaridines A and B are among the most challenging members of marine invertebrate-derived Leucetta alkaloids. Approaches to construction elaboration highly compact spirocyclic core described. The synthesis tricyclic guanidine via tandem oxidative amination dearomatizing spirocyclization (TOADS) using hypervalent iodine set stage for total migration C4/C8 double bond C4/C5 position, followed by oxidation. undesired but not surprising propensity cyclohexadienone undergo rearrangement phenol hindered desired olefin migration. Furthermore, initial efforts install oxidation sequentially, first at C5 then C4 in complete carbon skeleton, were fraught with unforeseen challenges unusual outcomes. In addition, scope limitations iodine-mediated on various substrates explored. Urethanes thiourethanes underwent an excellent yield, whereas reaction allylic species lacking p-methoxy substituent did proceed. Attempts prepare other precursors briefly discussed.

Language: Английский

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Seleno/Thio-functionalized ipso-Annulation of N-Propiolyl-2-arylbenzimidazole to Construct Azaspiro[5,5]undecatrienones

The Journal of Organic Chemistry, Journal Year: 2023, Volume and Issue: 88(23), P. 16485 - 16496

Published: Nov. 9, 2023

Till date, the ipso-cyclization of propiolamides is limited to provide azaspiro[4,5]decatrienones. Herein, we present first example ipso-carbocyclization, leading azaspiro[5,5]-undecatrienones from N-propiolyl-2-arylbenzimidazoles, involving both radical-based and electrophilic reactions. This report establishes an access a wide range chalcogenated (SCN/SCF3/SePh) benzimidazo-fused azaspiro[5,5]undecatrienones in good yields.

Language: Английский

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Visible-Light-Mediated Cascade 1,4-Hydrogen Atom Transfer versus Dearomative Spirocyclization of N-Benzylacrylamides: Divergent Access to Functionalized γ-Ketoamides and 2-Azaspiro[4.5]decanes

The Journal of Organic Chemistry, Journal Year: 2025, Volume and Issue: unknown

Published: Jan. 14, 2025

Visible-light-driven metal- and photocatalyst-free cascade 1,4-HAT dearomative spirocyclization of N-benzylacrylamides are described for sustainable synthesis a variety pharmaceutically important γ-ketoamides 2-Azaspiro[4.5]decanes in one pot good to excellent yields. Readily accessible nontoxic materials, expensive Ir or Ru mild conditions, functional group tolerance, operational simplicity, scalability enhance the practical value this protocol. Mechanistic studies reveal that acyl radicals generated from α-oxocarboxylic acids trigger rare spirocyclization. The synthetic potential environmentally benign method is further showcased by late-stage functionalization drug molecules, amino acid, peptides.

Language: Английский

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