30567-87-4

Catalytic transformation of alcohols via metal-catalyzed cross-coupling reactions is very important, but it typically relies on a multistep procedure. We here report a dynamic kinetic cross-coupling approach for the direct functionalization of alcohols. The feasibility of this strategy is demonstrated by a nickel-catalyzed cross-electrophile arylation reaction of benzyl alcohols with (hetero)aryl electrophiles. The reaction proceeds with a broad substrate scope of both coupling partners. The electron-rich, electron-poor, and ortho-/meta-/para-substituted (hetero)aryl electrophiles (e.g., Ar-OTf, Ar-I, Ar-Br, and inert Ar-Cl) all coupled well. Most of the functionalities, including aldehyde, ketone, amide, ester, nitrile, sulfone, furan, thiophene, benzothiophene, pyridine, quinolone, Ar-SiMe3, Ar-Bpin, and Ar-SnBu3, were tolerated. The dynamic nature of this method enables the direct arylation of benzylic alcohol in the presence of various nucleophilic groups, including nonactivated primary/secondary/tertiary alcohols, phenols, and free indoles. It thus offers a robust alternative to existing methods for the precise construction of diarylmethanes. The synthetic utility of the method was demonstrated by a concise synthesis of biologically active molecules and by its application to peptide modification and conjugation. Preliminary mechanistic studies revealed that the reaction of in situ formed benzyl oxalates with nickel, possibly via a radical process, is an initial step in the reaction with aryl electrophiles.

The invention discloses a preparation method of a diarylmethane structure compound. The preparation method disclosed by the invention is as shown in a formula I, and a target compound is prepared through reaction of benzyl alcohol and an aryl electrophilic reagent by utilizing a cheap metal nickel catalyst, taking 1, 1 '-bis (diphenylphosphine) ferrocene and 1, 10-phenanthroline as ligands, takingdimethyl oxalate as an additive and taking manganese powder as a reducing agent. The method has the advantages of easily available raw materials, mild reaction conditions, wide reaction substrate, good compatibility of reaction functional groups, unique chemical selectivity and the like. The method not only can be used for preparing the simple diarylmethane compound, but also can be suitable formodifying bioactive molecules with similar structures of raw materials.

Use of nitromethane as an electrophilic methylene source for the synthesis of symmetrical dithioacetals and bisarylmethanes has been showcased using Sc(OTf)3 as a catalyst. The procedure allows straightforward access to the densely functionalized dithioacetals and bisarylmethanes under mild conditions. Additionally, the method has been applied for the synthesis of antimalarial tetramethyl mellotojaponin C and anticancer dimeric phloroglucinol derivative.

Herein, we give a full account of the development of the palladium-catalysed cross-coupling of benzylammonium salts with boronic acids. A range of benzylamine-derived quaternary ammonium salts can be coupled with boronic acids under relatively mild conditions. Our optimization has identified ligands that can be used to chemoselectively cross-couple at the ammonium in the presence of chlorides. We demonstrate that intramolecular palladium-catalysed C-H activation is also a viable pathway for the putative benzyl-Pd(II) intermediate obtained upon oxidative addition and have optimised this to obtain fluorene in good yield.

Isofraxetin-6-O-β-D-glucopyranoside, identified from traditional medicinal herbal Xanthoceras sorbifolia Bunge, has been demonstrated to be a natural neuroinflammatory inhibitor. In order to obtain more derivatives with potential anti-neuroinflammatory effects, biotransformation was carried out. According to the characteristics of coumarin skeleton, suspension cultures of Angelica sinensis (Oliv.) Diels callus (A. sinensis callus) were employed because of the presence of diverse phenylpropanoids biosynthetic enzymes. As a result, 15 products were yielded from the suspension cultures, including a new coumarin: 8′-dehydroxymethyl cleomiscosin A (1), together with 14 known compounds. Their structures were elucidated by extensive spectroscopic analysis. Furthermore, the biotransformed pathways were discussed. Among them, compound 13 was transformed from isofraxetin-6-O-β-D-glucopyranoside, while compounds 1–6, 10–12, 14–15 were derived from the culture medium stimulated by the substrate. The biotransformation processes include hydroxylation, oxidation and esterification. Furthermore, their inhibitory effects on lipopolysaccharide (LPS)-activated nitric oxide (NO) production were evaluated in BV2 microglial cells. It is worth noting that, 1, 1′-methanediylbis(4-methoxybenzene) (3), obtucarbamates A (5), 2-nonyl-4-hydroxyquinoline N-oxide (10) and 1H-indole-3-carbaldehyde (11) exhibited significant inhibitory effect against neuroinflammation with IC50values at 1.22, 10.57, 1.02 and 0.76?μM respectively, much stronger than that of the positive control minocycline (IC5035.82?μM).

This paper describes the palladium-catalyzed studies on threefold coupling of triarylbismuth reagents with benzylic chlorides and iodides. The optimized protocol conditions are operationally simple, delivering threefold coupling of a variety of triarylbismuths in combination with benzylic chlorides and iodides. The two optimized protocols allowed the synthesis of a diverse range of unsymmetrical diarylmethanes in an efficient manner. As part of this study, chemoselective transformation of benzylic chlorides and iodides was also achieved. This journal is the Partner Organisations 2014.

Proton-exchanged montmorillonite (H-mont) was found to be an eco-friendly and cost-effective catalyst for the generation of O-methylated quinone methides (QM) from the corresponding p or o-methoxybenzyl esters and ethers. Nucleophilic trapping of the O-methylated QM with arenes, alcohols, 1,3-dicarbonyl compounds, silyl enol ethers, and allylsilanes has been carried out, respectively, leading to eco-friendly benzylation reactions. Using this protocol, H-mont-mediated deprotection of PMB-protected esters and ethers have been realized for the first time. This work would pave the way for further exploration in O-alkylated QM that are of chemical and biological significance.

We have developed a nickel-catalyzed cross coupling of benzylic ammonium triflates with aryl boronic acids to afford diarylmethanes and diarylethanes. This reaction proceeds under mild reaction conditions and with exceptional functional group tolerance. Further, it transforms branched benzylic ammonium salts to diarylethanes with excellent chirality transfer, offering a new strategy for the synthesis of highly enantioenriched diarylethanes from readily available chiral benzylic amines.

The partial exchange of tin with the protons of 12-tungstophosphoric acid (TPA) results in a highly active heterogeneous catalyst for benzylation of arenes with benzyl alcohol as benzylating agent. The catalysts were characterized by X-ray diffraction, Laser-Raman and FT-IR of pyridine adsorption. The catalytic activity depends significantly on the extent of tin exchanged with the protons of heteropoly tungstate. The characterization results suggest the presence of Lewis acidic sites by the exchange of tin. The catalyst with partial exchange of Sn showed high benzylation activity, which in turn related to variation in acidity of the catalysts. The catalyst is highly active for benzylation reaction irrespective of the nature of substituted arenes and benzyl alcohols. These catalysts are highly active compared to other acid catalysts used for benzylation of different arenes. The catalyst is easy to separate from reaction mixture and exhibit consistent activity upon reuse. The plausible reaction mechanism based on the role of both Lewis and Bronsted acid sites of the catalyst was discussed.

(Chemical Equation Presented) Reactions of arenes and heteroarenes with aromatic aldehydes proceeded smoothly in the presence of a catalytic combination of [Ir(COD)Cl]2-SnCl4 to afford the corresponding triarylmethane derivatives (TRAMs) in high yields. This 100% TRAM selective transformation is clean and eliminates the use of acid systems.

Much improved catalytic carbon-carbon bond-forming reactions between aryl chlorides and Grignard reagents has been achieved using nickel(II) ion on nanoporous carbon.

Acid-free Friedel-Crafts chemistry: A paradox? Nucleophilicity scales, based on reactions with benzhydrylium ions, show that many π systems are more nucleophilic than aqueous or alcoholic solutions that are generally employed as solvents for SN1 reactions. Solvolytically generated carbocations can, therefore, be trapped by donor-substituted arenes and alkenes to form products of Friedel-Crafts-type reactions in neutral aqueous solutions (see scheme).

The reactivity of o-hydroxybenzyl alcohol (o-HBA, 1), as a model compound for lignin, has been studied in various solvents between 390 and 560 K. Both in polar and apolar solvents the benzylic cation is the reactive intermediate. In alcoholic solvents, the benzylic cation reacts with the solvent to give the corresponding ethers. Relative reaction rates have been determined for different alcohols; a factor of 14 is encountered between the most (methanol) and least (tert-butyl alcohol) reactive ones. The etherification is reversible, in contrast to the electrophilic aromatic substitution with phenol and anisole, for which k(PhOH) = 1 X 105 M-1 s- 1 and k(anisole) = 1 x 104 M-1 s-1, at 424 K. In apolar hydroaromatic solvents, 7H-benz[de]anthracene, 9,10-dihydroanthracene, and 9,10- dihydrophenanthrene, the formation of o-cresol proceeds via hydride transfer from the solvent to the benzylic cation; rate constants at 555 K are 2 x 106, 5 x 104, and 5 x 103 M-1 s-1, respectively.

2-Methoxyalkanoic acids were found to undergo consecutive decarbonylative α,α-diarylation in P2O5-MsOH instead of Friedel-Crafts type arylation on the carbonyl carbon. The influence of the substituents of the arenes and the carboxylic acids in this reaction was elucidated based on the reaction yields. The reaction behavior was found to be primarily governed by the electron-withdrawing/releasing property of the α-substituents on the carboxylic acids as well as the positive species-accepting ability of the arenes. The steric hindrance was shown to participate in determining the reaction feasibility as a secondary factor.

Diarylmethanes were catalytically oxidized with oxygen to benzophenones with a Cu(I)CI catalyst in butyronitrile as solvent in the presence of the mediating agent 2,2',3,3',5,5'-hexaphenyl-(1,1'-biphenyl)-4,4'-dioxyl 1, which was generated in situ from 2,2',3,3',5,5'-hexaphenyl-(1,1'-biphenyl)- 4-4'-diol 4.

In the presence of gallium dichloride, the reaction of carbonyl compounds or their dimethylacetals with aromatic compounds afforded Friedel-Crafts alkylated adducts in good yields.It was suggested that the adducts were obtained by way of a reduction of the carbonyl compounds or their dimethylacetals, followed by the Friedel-Crafts reaction in one-pot.This is the first organic synthetic method with gallium dichloride, low valent gallium.

In the presence of gallium dichloride, carbonyl compounds reacted with anisole to give alkylated anisoles in good yields. It was suggested that the adducts were obtained by way of the reduction of the carbonyl compounds followed by the Friedel-Crafts reaction in a one-pot. This is the first organic synthetic method with gallium dichloride, low valent gallium.

Introduction of specific arylmethyl groups at the 3'-position of the thyroid hormone 3,3',5-triiodo-L-thyronine (T3), and its known hormonally active derivatives, gives liver-selective, cardiac-sparing thyromimetics, with potential utility as plasma cholesterol lowering agents.Selectivity-conferring 3'-substituents include substituted benzyl, e.g. p-hydroxybenzyl, and heterocyclic methyl, e.g. 2-oxo-1,2-dihydropyrid-5-ylmethyl and 6-oxo-1,6-dihydropyridazin-3-ylmethyl.Correlations between in vivo and in vitro receptor binding affinities show that liver/heart selectivity does not depend on receptor recognition but on penetration or access to receptors in vivo.QSAR studies of the binding data of a series of 20 3'-arylmethyl T3 analogues show that electronegative groups at the para position increase both receptor binding and selectivity in vivo.However, increasing 3'-arylmethyl hydrophobicity increases receptor binding but reduces selectivity.Substitution at ortho and meta positions reduces both binding and selectivity.Replacement of the 3,5-iodo groups by halogen or methyl maintains selectivity, with 3,5-dibromo analogues in particular having increased potency combined with oral bioavailability.Diphenyl thioether derivatives also have improved potency but are less orally active.At the 1-position, the D enantiomer retains selectivity, but removal of the α-amino group to give a propionic acid results in loss of selective thyromimetic activity.

The AlCl3 and BF3, as well as 65percent HPF6, catalyzed Friedel-Crafts alkylation of anisole with alkyl halides and alkohols was investigated.The alkylation of anisole with lower catalyst concentrations under mild conditions shows predominant ortho/para directing effect generally with a ratio of c.a. 2:1, with the amount of meta isomer uniformly less than 3percent.With "swamping" catalyst conditions the amount of meta substitution in methylation and ethylation can substantially increase.The isomer distribution in tert-butylation changes with time due to rapid ortho-para interconversion.Consequently, the AlCl3-catalyzed isomerization of isomeric alkylanisoles was also studied.In case of tert-butylanisoles, the ortho isomer shows relatively rapid conversion into para followed by much slower isomerization to meta.The para and meta isomers show isomerization to meta-para mixtures.Isomerization of ethyl-, isopropyl-, and benzylanisoles is generally slow whereas methylanisoles do not isomerize.Comparing results of the alkylation of anisole with toluene leads to the conclusion that the latter are readily affected by concurrent (and in some cases consecutive) isomerization.As the barrier for isomerization in the benzenium ion intermediates of the alkylations is higher in the case of CH3O- than CH3-substituted systems, anisole tends to give the kinetically controlled ortho-para alkylation products and the amount of meta isomer is low.Study of alkylation of 3,5-di- and 2,4,6-trideuterated toluene and anisole and comparing retained deuterium contents with isomer distributions shows that alkylated product formation in case of toluene, but not of anisole, is proceeded by intramolecular, 1,2-alkyl, and hydrogen-deuterium shifting resulting also in increased meta substitution.This effect is most predominant in methylation and ethylation where the alkyl shifts are intramolecular but not in tert-butylation and benzylation, where alkyl transfer is intermolecular.Isopropylation is intermediate in nature.No simple selectivity-reactivity relationship is indicated in the studied alkylation reactions.As shown in benzylations with increasingly electron-donating and -withdrawing substituted benzyl chlorides overall rate (i.e., substrate selectivity) and isomer distributions (i.e., regioselectivity) are not determined in the same step as significantly decreased substrate selectivity is not accompanied by loss of positional selectivity.Previously reported alkylations showing high degree of meta substitution therefore, must have been affected by thermodynamically controlled rearrangement processes, including intramolecular alkyl and hydrogen shifts in the arenium ion intermediates of the alkylation reactions.These are to be differentiated from possible subsequent product isomerizations.Under predominantly kinetic conditions anisole as well as toluene are substantially ortho-para directing in alkylations, as in other electrophilic aromatic substitutions.