Catalytic Oxidation of 3-Arylbenzofuran-2(3H)-ones with PCC-H5IO6: Syntheses of 3-Aryl-3-hydroxy/3-amido-3-arylbenzofuran-2(3H)-ones

Regiodivergent and Enantioselective Allylic C-H Alkylation of Allyl Ethers: Optimization, Scope, Mechanism and Application

Vinyl ethers and allyl ethers are important motifs in natural products and pharmaceuticals. Among various methods toward their synthesis, direct allylic C-H functionalization of allyl ethers is one of the most efficient approaches. In this study, one of two regioisomers, a vinyl ether or an allyl ether, could be obtained, depending on whether a Lewis acid co-catalyst was present. Furthermore, branched allyl ethers were smoothly prepared in excellent regio- and enantioselectivity (up to 20 : 1 b/l, 99 % ee) by synergistic catalysis with an achiral Pd(0) complex and a chiral Lewis acid catalyst.

Transition-metal-free decarbonylation-oxidation of 3-arylbenzofuran-2(3H)-ones: access to 2-hydroxybenzophenones

A transition-metal-free decarbonylation-oxidation protocol for the conversion of 3-arylbenzofuran-2(3H)-ones to 2-hydroxybenzophenones under mild conditions has been developed. NMR studies confirmed the role of in-situ-generated hydroperoxide in the conversion. The protocol was applied to a diverse range of substrates to access the target products in good to excellent yields. A structure-activity study for the 5-substituted-2-hydroxybenzophenones towards UV-protection abilities has been verified by mathematical calculations.

Efficient in-situ synthesis of heterocyclic derivatives from benzyl alcohols using pyrazinium chlorochromate-functionalized carbonitride as a novel catalyst

The synthesis of efficient organic compounds from simple substrates is both noticeable and important. However, it can be challenging to achieve this target using suitable strategies. To address this issue, pyrazinium chlorochromate (PCC) was used to modify carbonitride nanosheets (CNs) and applied as a heterogeneous catalyst in the oxidation of benzyl alcohols. That can be regarded as innovation in ingenious synthesis of the PCC on the CNs. Then, it was identified by varied techniques such as EDS, FT-IR, XRD, STA and FE-SEM. This process resulted in in-situ synthesis of 1,4-dihydropyridine and 3,4-dihydropyrimidin-2-(1H) one derivatives with excellent yield.

Visible-light-induced Ritter-type amidation of α-hydroxy ketones in the selective synthesis of α,α-diamido and monoamido ketones

Visible light-induced, transition metal-free oxidative dehydroxylation and C-H amidation of α-hydroxy ketones involving Ritter-type amidation has been developed, leading to the selective synthesis of α,α-diamido- and α-monoamido ketones with tunable selectivity as well as broad substrate tolerance.

One-pot domino syntheses of 3-alkyl-3-N-substituted aminobenzofuran-2(3H)-ones based on alkali-promoted Michael addition and lactonization

In this paper, a novel cascade reaction of caesium carbonate-promoted Michael addition and lactonization for the one-pot synthesis of 3-alkyl-3-N-substituted aminobenzofuran-2(3H)-one derivatives has been established based on the screening of the alkaline reagents and optimization of reaction conditions, in which the N-substituted (ortho-hydroxy)aryl glycine esters were used as the Michael donors to react with different α, β-unsaturated carbonyl compounds. In the case of using the asymmetric starting material, the epimers could be successfully separated by conventional chromatography. In addition, plausible mechanisms were suggested and the absolute configuration of the epimer was analysed. All the chemical structures of unreported benzofuran-2(3H)-one derivatives were characterized by 1H nuclear magnetic resonance (NMR), 13C NMR, IR and high-resolution mass spectrometry (HRMS).

Recent advances of Ritter reaction and its synthetic applications

This review provides a comprehensive survey of Ritter reactions from 2014 to 2020.

Recent Applications of Ritter Reactions in Organic Syntheses

The Ritter reactions are an important Classes of organic reactions in the synthesis of heterocycles and linear amides. Ritter reaction products are pyridine, quinazolinone, and other heterocyclic structures, which have different biological activities such as antibacterial and antivirous application from 2017 to 2020. Furthermore, the Ritter reaction in the synthesis of linear amides is evaluated from 2015 to 2020 in this review. Linear amides are essential components in drug molecules which are difficult to synthesize by conventional methods but can be synthesized through the Ritter reaction.

Chiral Calcium Phosphate Catalyzed Enantioselective Amination of 3-Aryl-2-benzofuranones

A 4-tert-butyl-phenyl substituted (R)-[H₈]-BINOL chiral calcium phosphate catalyzed enantioselective amination of 3-aryl-2-benzofuranones with dibenzyl azodicarboxylate is described. The catalyst loading of the reaction is 1 mol %. This transformation is facile and has a high degree atom economy, which gave products with good yields and high enantioselectivities (79% to 99%). This reaction has excellent ee and a broad substrate scope with mild reaction conditions.

Synthesis and biological evaluation of benzofuran-based 3,4,5-trimethoxybenzamide derivatives as novel tubulin polymerization inhibitors

A new series of derivatives characterized by the presence of the 3,4,5-trimethoxylbenzamide substituted benzofurans were synthesized and evaluated for antiproliferative activity against four cancer cell lines and one normal human cell line. Among them, derivative 6g with greatest cytotoxicity significantly inhibited the growth of MDA-MB-231, HCT-116, HT-29 and HeLa cell lines with IC₅₀ values of 3.01, 5.20, 9.13, and 11.09 μM, respectively. Importantly, 6g possessed excellent selectivity over non-tumoral cell lines HEK-293 (IC₅₀ > 30 μM). Moreover, mechanistic studies revealed that 6g induced HeLa cells arrested in G2/M phase in a concentration-dependent manner, and inhibited polymerization of tubulin via a consistent way with CA-4. In general, these observations suggest that 6g is a promising anti-cancer lead and is worth further investigation to generate potential antitumor agents.

Rhodium(iii)-catalysed cascade [3 + 2] annulation of N-aryloxyacetamides with 3-(hetero)arylpropiolic acids: synthesis of benzofuran-2(3H)-ones

Herein, a cascade [3 + 2] annulation of N-aryloxyacetamides with 3-(hetero)arylpropiolic acids affording benzofuran-2(3H)-ones via rhodium(iii)-catalyzed redox-neutral C-H functionalization/isomerization/lactonization using an internal oxidative directing group O-NHAc was achieved. This catalytic system provides a regio- and stereoselective approach to synthesize (Z)-3-(amino(aryl)methylene)benzofuran-2(3H)-ones with exclusive Z configuration selectivity, acceptable yields and good functional group tolerance. Preliminary investigations on ultraviolet-visible and fluorescence behaviors reveal that the annulation products may be applied as a promising fluorescent probe for sensing metal cations, especially for cerium (Ce3+).

C(sp3)-H hydroxylation of fluorenes, oxindoles and benzofuranones with a Mg(NO3)2-HP(O)Ph2 oxidation system

A novel oxidation system in which magnesium nitrate [Mg(NO3)2] is used as an oxidant in the presence of diphe-nylphosphine oxide [HP(O)Ph2] permits the C(sp3)-H hydroxylation of fluorenes, oxindoles, and benzofuranones. This method features high efficiency, good functional group tolerance, and operational simplicity. The synthetic utility is highlighted by further transformations to valuable organic materials.

Palladium-Catalyzed Chemoselective Activation of sp3 vs sp2 C-H Bonds: Oxidative Coupling To Form Quaternary Centers

The oxidative activation of alkyl C-H bonds vs arene C-H bonds with Pd(OAc)₂ has been found to be generalizable to a number of nucleophilic substrates allowing the formation of a range of hindered quaternary centers. The substrates share a common mechanistic path wherein Pd(II) initiates an oxidative dimerization. The resultant dimer modifies the palladium catalyst to favor activation of alkyl C-H bonds in contrast to the trends typically observed via a concerted metalation deprotonation mechanism. Notably, insertion occurs at the terminus of the alkyl arene for hindered substrates. Two different oxidant systems were discovered that turn over the process. Parameters have been identified that predict, which substrates are productive in this reaction.