Copper-Catalyzed Radical Cascade Difluoromethylation/Cyclization of 2-(3-Arylpropioloyl)benzaldehydes: A Route to Difluoromethylated Naphthoquinones

Palladium-Catalyzed Synthesis of Indanone via C-H Annulation Reaction of Aldehydes with Norbornenes

A novel methodology for the synthesis of indanone derivates has been developed. The palladium-catalyzed annulation reaction of o-bromobenzaldehydes with norbornene derivatives is achieved through extremely concise reaction processes. The indanone skeleton was established directly via C-H activation of the aldehyde group under a mild reaction condition. This method is simple and practical, which simplified the traditional synthesis method for the rapid construction of indanone.

Synthesis of Selectively gem-Difluorinated Molecules; Chiral gem-Difluorocyclopropanes via Chemo-Enzymatic Reaction and gem-Difluorinated Compounds via Radical Reaction

The incorporation of fluorine atoms into an organic compound can alter the chemical reactivity or biological activity of the resulting compound due to the strong electron withdrawing nature of the fluorine atom. We have synthesized many original gem-difluorinated compounds and described the results in four sections. The first section describes the synthesis of optically active-gem-difluorocyclopropanes via the chemo-enzymatic reaction; we applied these compounds to liquid crystalline molecules, then further discovered a potent DNA cleavage activity for the gem-difluorocyclopropane derivatives. The second section describes the synthesis of selectively gem-difluorinated compounds via a radical reaction; we synthesized fluorinated analogues of a sex pheromone of the male African sugarcane borer, Eldana saccharina, and used the compounds as proof for investigating the origin of pheromone molecule recognition on the receptor protein. The third involves the synthesis of 2,2-difluorinated-esters by visible light-driven radical addition of 2,2-difluoroacetate with alkenes or alkynes in the presence of an organic pigment. The last section describes the synthesis of gem-difluorinated compounds via the ring-opening of gem-difluorocyclopropanes. We further developed a novel method of synthesizing gem-difluorohomoallylic alcohols via the ring-opening of gem-difluorocyclopropane and aerobic oxidation by photo-irradiation in the presence of an organic pigment. Since gem-difluorinated compounds that were prepared by the present method have two olefinic moieties with a different reactivity at the terminal position, we accomplished the synthesis of four types of gem-difluorinated cyclic alkenols via the ring-closing-metathesis (RCM) reaction.

Recent advances in electrooxidative radical transformations of alkynes

During the past few years, electrochemical oxidative reactions through radical intermediates have emerged as an environmentally-benign, powerful platform for the facile formation of C–E (E = C, N, S, Se, O and Hal) bonds through single-electron-transfer (SET) processes at the electrodes. Functionalized unsaturated molecules and unusual structural motifs can, for instance, be directly constructed under exceedingly mild reaction conditions through initial radical attack onto alkynes. This minireview highlights the recent advances in electrooxidation in radical reactions until June 2022, with a particular focus on radical additions onto alkynes.

Strategy Analysis of Ynones’ Radical Reactions

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This review highlights the multifaceted synthetic applications of ynones in radical reactions. Substantial progress has been made over the last decade (2010-2020) in the utilization of ynones. Herein, the chemistry of ynones is divided into three sections based on the classes of critical mechanistic insights: (1) radical addition and intramolecular cyclization; (2) radical addition and intermolecular annulation; (3) radical addition and coupling. We hope that this review will promote future research in this area.

Recent advances in transition-metal-catalyzed annulations for the construction of a 1-indanone core

Transition metal-catalyzed carbon–carbon bond forming reactions are a well accepted strategy for the synthesis of organic compounds. This review gives a brief update on the transition-metal-catalyzed annulations to construct 1-indanone scaffolds.

Promising reagents for difluoroalkylation

This review describes recent advances in difluoroalkylation reactions using different substrates.

Syntheses of 12H-benzo[a]xanthen-12-ones and benzo[a]acridin-12(7H)-ones through Au(i)-catalyzed Michael addition/6-endo-trig cyclization/aromatization cascade annulation

A multifaceted gold(i)-catalyzed aromaticity-driven double 6-endo cascade cyclization strategy to synthesize both 12H-benzo[a]xanthen-12-ones and benzo[a]acridin-12(7H)-ones, whose core motifs xanthone and acridone both exist as important scaffolds in an immense number of bioactive compounds, was developed. The scopes of this strategy were examined by using a batch of synthetic 1,3-diphenylprop-2-yn-1-one substrates. To probe the mechanism of this cyclization a control experiment for synthesizing intermediates was performed. Thus, a putative mechanism was determined according to this experiment and previous studies.

An effective preparation of both 1,3-diketones and nitriles from alkynones with oximes as hydroxide sources

An effective phosphine-catalyzed protocol has been established for the syntheses of 1,3-diketones and nitriles from alkynones with oximes as hydroxide surrogates. This method features the use of a phosphine catalyst, compatibility with various functional groups and ambient temperature, which makes this approach very practical. A plausible mechanism was proposed.

Regioselective 5-exo-dig oxy-cyclization of 2-alkynylbenzamide for the synthesis of isobenzofuran-1-imines and isobenzofuran

A TBAB-mediated regioselective radical cyclization of 2-alkynylbenzamide is described herein for the synthesis of isobenzofuran-1-imines. The reactions proceeded smoothly under mild conditions.

Recent advances in radical transformations of internal alkynes

This review highlights the recent progress in the radical transformation of internal alkynes and focuses on the reaction mechanisms by carbon/heteroatom-centered triggered additions, and offers a comprehensive overview on the existing procedures and employed methodologies.

Cobalt Ion Promoted Redox Cascade: A Route to Spiro Oxazine-Oxazepine Derivatives and a Dinuclear Cobalt(III) Complex of an N-(1,4-Naphthoquinone)-o-aminophenol Derivative

The study discloses that the redox activity of N-(1,4-naphthoquinone)-o-aminophenol derivatives (L^RH₂) containing a (phenol)-NH-(1,4-naphthoquinone) fragment is notably different from that of a (phenol)-NH-(phenol) precursor. The former is a platform for a redox cascade. L^RH₂ is redox noninnocent and exists in Cat-N-(1,4-naphthoquinone)(2-) (L^R 2-) and SQ-N-(1,4-naphthoquinone) (L^R •-) states in the complexes. Reactions of L^RH₂ with cobalt(II) salts in MeOH in air promote a cascade affording spiro oxazine-oxazepine derivatives (^OXL^R) in good yields, when R = H, Me, ^tBu. Spiro oxazine-oxazepine derivatives are bioactive, and such a molecule has so far not been isolated by a schematic route. In this context this cascade is significant. Dimerization of L^RH₂ → ^OXL^R in MeOH is a (6H⁺ + 6e) oxidation reaction and is composed of formations of four covalent bonds and 6-exo-trig and 7-endo-trig cyclization based on C-O coupling reactions, where MeOH is the source of a proton and the ester function. It was established that the active cascade precursor is [(L^Me •-)Co^IIICl₂] (A). Notably, formation of a spiro derivative was not detected in CH₃CN and the reaction ends up furnishing A. The route of the reaction is tunable by R, when R = NO₂, it is a (2e + 4H⁺) oxidation reaction affording a dinuclear L^R 2- complex of cobalt(III) of the type [(L^NO2 2-)₂Co^III₂(OMe)₂(H₂O)₂] (1) in good yields. No cascade occurs with zinc(II) ion even in MeOH and produces a L^Me •- complex of type [(L^Me •-)Zn^IICl₂] (2). The intermediate A and 2 exhibit strong EPR signals at g = 2.008 and 1.999, confrming the existence of L^Me •- coordinated to low-spin cobalt(III) and zinc(II) ions. The intermediates of L^RH₂ → ^OXL^R conversion were analyzed by ESI mass spectrometry. The molecular geometries of ^OXL^R and 1 were confirmed by X-ray crystallography, and the spectral features were elucidated by TD DFT calculations.