Synthesis of 6,8,9-tri- and 2,6,8,9-tetrasubstituted purines by a combination of the Suzuki cross-coupling, N-arylation, and direct C-H arylation reactions

Novel practical methodology of synthesis of a several types of di-, tri-, and tetraarylpurine derivatives by a combination of regioselective Suzuki cross-coupling reactions and/or Cu-catalyzed N-arylation with direct C-H arylations was developed. 6,8-Diaryl- and 2,6,8-triaryl-9-isopropylpurines were prepared by one or two cross-couplings of 6-chloro- or 2,6-dichloro-9-isopropylpurine with arylboronic acids followed by Pd-catalyzed C-H arylation by aryl halides to position 8. 6-Chloropurine and adenine underwent Cu-catalyzed N-arylation to position 9 with boronic acids, followed by cross-coupling with AlMe3 and/or C-H arylation to obtain 8,9-diaryl-6-methylpurines or 8,9-diaryladenines (accompanied by products of partial N-arylation of adenine in position 6). The methodology is suitable for construction of small libraries of modified purines.     

Synthesis of 4-aryl-, 2,4-diaryl- and 2,4,7-triarylpyrrolo[2,3-d]pyrimidines by a combination of the Suzuki cross-coupling and N-arylation reactions

A simple and facile synthesis of novel 4-aryl-2-chloro-, 2,4-diaryl- and 2,4,7-triarylpyrrolo[2,3-d]pyrimidines with various aryl and heteroaryl assemblies in the heterocyclic framework by a combination of Suzuki cross-coupling and N-arylation reactions of 2,4-dichloropyrrolo[2,3-d]pyrimidine with arylboronic acids and haloarenes are described. A majority of the synthesized compounds were found to emit in a near UV-blue spectral range with fluorescence quantum yields up to 67%. The impact of aryl groups attached to the pyrrole ring of pyrrolopyrimidine derivatives on optical properties is discussed.     

Synthesis and reactivity of solid-supported organotrifluoroborates in Suzuki cross-coupling

Solid-supported organotrifluoroborates were prepared in high yields by ion exchange with Amberlyst resins. The reactivity of solid supported aryltrifluoroborates was evaluated in Suzuki-Miyaura couplings with numerous aryl bromide partners. Electron-rich and -poor substituents were tolerated on both substrates, providing yields up to 90%. Examples of alkyl-, alkenyl-, alkynyl-, and heteroaryltrifluoborates were also successfully cross-coupled to aryl halides.     

Synthesis of 3-hetarylpyrroles by Suzuki–Miyaura cross-coupling

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Synthesis of tetraarylthiophenes by regioselective Suzuki cross-coupling reactions of tetrabromothiophene

Tetraarylthiophenes were prepared by regioselective Suzuki cross-coupling reactions of tetrabromothiophene.     

Synthesis of 1,3-diaryl-1H-benzo[g]indazoles

A facile three-step synthetic route toward 1,3-diaryl-1H-benzo[g]indazoles 1a–1n starting with 3,4-dimethoxy-2-allylbenzaldehyde (6) in modest total yield is described. The facile route was carried by aldol condensation of aldehyde 6 with aryl methyl ketones 5a–5d in alkaline MeOH at reflux, Knorr pyrazole synthesis of the resulting chalcones 4a–4d with aryl hydrazines 3a–3e in EtOH at reflux followed by DDQ-mediated aromatization in toluene at reflux, and oxidative cleavage annulation of olefins 2a–2n with the one-pot combination of OsO₄/NaIO₄/HOAc in the aqueous THF at reflux.     

1,3-Oxazoline- and 1,3-oxazolidine-2-thiones as substrates in direct modified Stille and Suzuki cross-coupling

1,3-Oxazoline- (OXT) and 1,3-oxazolidine-2-thiones (OZT) can undergo direct Stille and Suzuki cross-coupling reactions under microwave activation to produce 2-aryloxazoles and 2-aryloxazolines in reasonable to good yields.     

Palladium-catalyzed Suzuki cross-coupling reactions in a microemulsion

An enhancement of palladium-catalyzed Suzuki cross-coupling reactions between substrates possessing long-chain alkyl or oxyalkyl substituents in two-phase media, in the presence of sodium dodecylsulfate, is shown. Quantitative evaluations of the influence of SDS on the reaction rates were determined.     

Synthesis of 8-arylated catechin and epicatechin derivatives via Suzuki cross-coupling

8-Arylated catechin and epicatechin derivatives have been prepared in good to excellent yields via Suzuki cross-coupling in the presence of Pd₂(dba)₃ as the Pd(0) source and Sphos as the phosphine ligand.     

Heterogeneous Suzuki cross-coupling reactions over palladium/hydrotalcite catalysts

The efficiency of various heterogeneous solids consisting of palladium supported on hydrotalcite as catalysts in the Suzuki cross-coupling reaction between bromobenzene and phenylboronic acid was studied. Based on the catalytic activity results, the reaction develops to an acceptable extent with 100% selectivity at moderate temperatures in the presence of some of the catalysts. The best results were provided by a catalyst consisting of an acetate-pyridine complex of Pd supported on hydrotalcite that gave high conversion values even after three reuses. The reactions conditions were very mild (a temperature of 55 degrees C and atmospheric pressure). In fact, the catalyst provided conversion and selectivity results surpassing those of existing heterogeneous phase catalysts and most homogeneous phase catalysts for the same purpose.     

Synthesis of non-proteinogenic phenylalanine analogues by Suzuki cross-coupling of a serine-derived alkyl boronic acid

Protected serine-derived boronic acids have been prepared as β-anionic alanine equivalents, and undergo efficient Suzuki cross-coupling with a variety of aryl halides to give, after elaboration, non-proteinogenic phenylalanine analogues.     

Synthesis of some new N,N′-diarylsubstituted methylene-bis-dihydro-2H-1,3-benzoxazines

The synthesis of a new series of six-membered N,N′-diarylsubstituted methylene-bis-dihydro-2H-1,3-benzoxazines （5a-e） was achieved in excellent yields by Mannich-type condensation of N,N′-diarylsubstituted methylene-bis-o-hydroxybenzyl amines （4a- e） with formaldehyde in chloroform at reflux. These amines （4a-e） were obtained by the reduction of N, Nr-diarylsubstituted methylene-bis-o-hydroxybenzyl imines （3a-e） with NaBH4, which inturn were obtained by the condensation of methylene-bissalicylaldehyde （2） with various substituted arylamines.     

Buchwald ligand-assisted Suzuki cross-coupling of polychlorobenzenes

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Synthesis of unnatural amino acids via Suzuki cross-coupling of enantiopure vinyloxazolidine derivatives

[formula: see text] (R and S)-alpha-Amino alcohols and alpha-amino acids, including 4-methoxyhomophenylalanine, with a variety of unnatural side chains have been synthesized via palladium-catalyzed cross-coupling Suzuki reactions. The key building blocks 1 and 2, synthesized from the common achiral precursor 2-butene-1,4-diol, were made enantiopure utilizing a Pseudomonas cepacia lipase-catalyzed kinetic resolution. The optimal conditions for the Suzuki cross-coupling and the subsequent oxidations of the resultant alpha-amino alcohols are described.     

Synthesis of cobalt-containing monodentate phosphine ligand and application toward Suzuki cross-coupling reactions

A bulky, dicobalt complexed, mono-dentate phosphine, [(μ-PPh₂CH₂PPh₂)Co₂(CO)₄](μ,η-PhCCPCy₂) (4), was prepared from the reactions of the bis(diphenylphosphino)methylene (dppm)-bridged dicobalt complex Co₂(CO)₆(μ-Ph₂PCH₂PPh₂) (2) with PhCCPCy₂ (3). Combination of 4 and Pd(OAc)₂ (1:1) gave an active catalyst for the palladium-catalyzed Suzuki coupling of aryl bromides with phenylboronic acid; the catalytic reactions can be performed even under low catalyst loadings (0.1-0.001 mol% 4/Pd(OAc)₂). Compound 4 has been proved to be an authentic and effective mono-dentate phosphine ligand. Crucial factors such as 4/Pd(OAc)₂ ratio, base being used, solvent volume, temperature, and electronic variation of the aryl bromides in reactions were also investigated and results are reported.     

Synthesis of fluorenones based on a ‘[3+3] cyclization/Suzuki cross-coupling/Friedel-Crafts acylation’ strategy

Functionalized fluorenones were prepared by sequential ‘[3+3] cyclization-Suzuki cross-coupling/Friedel-Crafts acylation’ reactions.     

Catalytic asymmetric carbohydroxylation of alkenes by a tandem diboration/Suzuki cross-coupling/oxidation reaction

[reaction: see text] Chiral nonsymmetric 1,2-diboron adducts are generated by catalytic enantioselective diboration. Oxidation of these adducts provides 1,2-diols in good yield. Alternatively, 1,2-diboron compounds may be reacted, in situ, with aryl halides wherein the less hindered C-B bond participates in cross-coupling. The remaining C-B bond is then oxidized in the reaction workup thereby allowing for net asymmetric carbohydroxylation of alkenes in a tandem one-pot diboration/Suzuki coupling/oxidation sequence.     

Multicomponent and one-pot synthesis of trisubstituted pyridines through a Pd-catalyzed cross-coupling/cross-coupling/cycloaddition sequence

Trisubstituted pyridines are regioselectively synthesized through multicomponent and one-pot processes promoted by a bifunctional Pd-catalyst. The process involves formation of an enamine by Pd-catalyzed amination of an alkenyl bromide, formation of a 2-aza-1,3-butadiene by Pd-catalyzed cross-coupling of a trimethylsilylimine with an alkenyl bromide, and Lewis acid catalyzed cycloaddition between the enamine and the azadiene.     

Investigations on the synthesis of monoarylated diynes by monoprotection/cross-coupling/deprotection approach

The presented experimental work investigates the usefulness of temporary monoprotection of symmetrical terminal diynes in the coupling with aryl iodides. The monoprotection/cross-coupling/deprotection approach proved to be efficient for the coupling of diynes with aryl substrates avoiding the formation of diarylated byproducts. The high importance of the ratio of solvents in the Sonogashira coupling is demonstrated.     

光催化Suzuki偶联反应的非均相催化剂研究进展

Suzuki偶联反应作为构建C-C键的最有效的手段之一,在医药、染料和电子工业等领域扮演着重要的角色。传统的Suzuki偶联反应催化体系需要依赖化石能源产生的热能来驱动,不仅造成了不可再生资源的消耗,还会导致相应的环境问题。近年来,光催化技术和绿色有机合成化学蓬勃发展,利用可再生的太阳能光催化Suzuki偶联反应不但可以解决在催化反应过程中的能源与环境问题,还可以在温和条件下获得高产率的联苯化合物产物,正在受到人们的广泛关注。与均相光催化剂相比,非均相光催化剂具有良好的化学稳定性、便捷的可回收性与优异的循环利用性能等优点,因此成为光催化Suzuki偶联反应的研究重点。本文总结了非均相催化剂光催化Suzuki偶联反应的基本原理,介绍了近年来科研工作者对光催化Suzuki偶联反应中非均相催化剂的制备方法、催化性能以及可循环利用性等方面做的一系列研究。