硅胶硫酸:一种在温和及无溶剂条件下一锅法合成1,4-二氢吡啶的高效多相催化剂(英文)

A series of 1,4-dihydropyridines have been prepared by a one-pot condensation of aldehydes,ethyl acetoacetate,and ammonium acetate in the presence of a heterogeneous catalyst silica sulfuric acid at room temperature under solvent-free condition. This new protocol has the advantage of short reaction time and excellent yields,and is an environmentally benign route to the synthesis of 1,4-dihydropyridines.     

Metal and organo-catalysed asymmetric hydroaminomethylation of styrenes

A new protocol that enables asymmetric hydroaminomethylation of styrenes to afford chiral amines has been developed. Catalysed by an Rh-phosphine species and a chiral phosphoric acid, styrenes are converted into β-chiral amines with good enantioselectivities under syngas in the presence of an amine and Hantzsch ester. The reaction involves two key steps, hydroformylation and reductive amination, with the former catalysed by the Rh species whilst the latter by the phosphoric acid.     

One-pot five-component synthesis of highly functionalized piperidines using oxalic acid dihydrate as a homogenous catalyst

An efficient green protocol is described for the preparation of highly functionalized piperidines via a one-pot five-component reaction between aromatic aldehydes,anilines andβ-ketoesters in the presence of oxalic acid dihydrate as catalyst in ethanol at ambient temperature.The structure as well as the relative stereochemistry of these compounds was confirmed by single X-ray crystallographic analysis.     

Arylation of pyridine N-oxides via a ligand-free Suzuki reaction in water

We report a practical and highly efficient protocol for the arylation of pyridine N-oxides with arylboronic acid through palladium-catalyzed Suzuki reaction in water.This ligand-free Suzuki reaction is performed in the presence of diisopropylamine and gives 2-or 3-arylated pyridyl N-oxide derivatives in good to excellent yields within 1 h.     

A Highly Efficient and Recyclable Solid Acid Catalyst for Synthesis of Spiro-oxindole Dihydroquinazolinones Under Ultrasound Irradiation

A simple,efficient and green procedure for the synthesis of spiro-oxindole dihyfroquinazolinones was developed by multi-component condensation of isatoic anhydride,aniline and isatin in the presence of a novel solid acid catalyst under ultrasound irradiation.The present environmentally benign protocol offers several advantages, such as shorter reaction time,a wide range of fimctional group tolerance,the use of an inexpensive heterogeneous catalyst,and a high yield of products via a simple experimental and work-up procedure.The mesoporous solid acid catalyst was directly prepared from phytic acid by microwave-sulfonation method without template.The phytic acid based solid acid was fully characterized by means of Fourier transform infrared spectroscopy(FTIR),Raman spectroscopy,X-ray diffraction(XRD),X-ray photoelectron spectroscopy(XPS),and transmission electron imcroscopy(TEM).The catalyst can be recovered and reused for at least five runs without significant impact on the product yields.     

GENERATION OF RADICAL CATIONS——A FACILE GENERATION OF RADICAL CATIONS VIA THE ACTION OF AN OXOAMMONIUM TRIFLUOROACETATE

The reaction between a stable nitroxide, 2, 2, 6, 6-tetramethyl-4-chloropiperidinyl-1-oxy, la and aromatic amines and heterocycles, 3—9, in methylene chloride in the presence of trifluoroacetic acid, has been investigated. The corresponding radical cations of the amines and the heterocycles were readily generated by this reaction, which could persist for a long period of time in the system. Kinetic ESR studies were performed to elucidate the reaction mechanism and the results showed that the formation of the radical cations involves one-electron transfer reaction between the active oxidant, the oxoammonium trifluoroacetare, 2a, which results from the disproportionation of the nitroxide in the presence of trifluoroacetic acid, and the substrates studied. This affords a facile method for the generation of radical cations from aromatic amines and heterocyclics by the action of an organic oxidant.     

Environmentally Benign Oxidation of Some Organic Sulfides with 34% Hydrogen Peroxide Catalyzed by Simple Heteropolyoxometalates

An environmentally benign oxygenation protocol was developed for selective oxidation of some types of aromatic and aliphatic sulfides in good to excellent yields utilizing 34% hydrogen peroxide catalyzed by simple heteropolyoxometalates in normal drinking water at room temperature. The catalysts could be recovered and reused for at least seven reaction cycles under the described reaction conditions without considerable loss of reactivity. This procedure introduced a new insight into the use of simple heteropolyanions as recoverable catalysts for the oxidation of organic sulfides by an environmentally acceptable protocol. Keywords     

Facile synthesis of novel fluorinated thieno[2,3-d]pyrimidine derivatives containing 1,3,4-thiadiazole

A series of novel fluorinated thieno[2,3-d]pyrimidine derivatives incorporating 1,3,4-thiadiazole were synthesized by a facile microwave-assisted procedure,including the cyclization of 2-aminothiophene-3-carbonitrile with trifluoroacetic acid,chlorination and nucleophilic substitution reaction.This protocol offered such advantages as mild reaction conditions,short reaction time, simple puritication and good yields.The structures of the products were characterized by ~1H NMR,MS,elemental analysis and Xray diffraction.     

Expedient Trifluoromethylacylation of Styrenes Enabled by Photoredox Catalysis

Herein,we disclosed a photoredox enabled protocol for trifluoromethylacylation of styrenes through a radical-carboanion cascade and subsequent oxidation.With a broad range of aldehydes and inexpensive Langlois reagent as acyl and CF3 precursor,respectively,the alkene motif could be readily converted into β-trifluoromethyl ketones in moderate to good yields and with excellent regioselectivity.Besides CF3,di-,mono-and non-fluorinated C-radicals were revealed amenable in this reaction,providing good opportunity for the construction of structurally diverse ketones of interest in pharmaceutical research.Additionally,the utility of this protocol was further demonstrated by successful extension to trifluoromethylarylation and-alkylation by employing arylcyanide or acrylates in place of carbonyls.     

A ligand-free Heck reaction catalyzed by the in situ-generated palladium nanoparticles in PEG-400

<正>A ligand-free Heck reaction catalyzed by in situ-generated palladium nanoparticles in PEG-400 has been developed.This catalytic system is a simple and active protocol for the Heck reaction of aryl halides under mild conditions.Comparative experiments demonstrated that the Heck reaction catalyzed by the palladium nanoparticles in situ-generated under the Heck reaction conditions was carried out much quicker than that by the in ex situ-generated ones.     

Synthesis of methoxy-substituted phenols by peracid oxidation of the aromatic ring

[reaction: see text] A novel benign protocol for the preparation of hydroxy-methoxybenzene derivatives is disclosed. By utilizing this protocol, activated aromatic compounds such as 1,3-dimethoxy-2-methyl-benzene and 1-(2,6-dimethoxyphenyl)ethanone are smoothly converted to the corresponding monohydroxylated compound. The reaction can be considered to be a normal aromatic electrophilic substitution reaction, and the regioselectivity for the reaction thus follows the similar rules as for electrophilic substitutions. The protocol is composed by benign reagents, namely, hydogenperoxide, acetic acid, and p-toluene sulfonic acid, which lead to the production of ethaneperoxoic acid in situ. The ethaneperoxoic acid operates as the hydroxylating reagent. The hydroxylation reaction is completed within a short period and requires moreover only mild experimental conditions, which make this novel protocol a green, cheap, and rapid process leading to hydroxy-methoxybenzene derivatives. The proposed reaction mechanism is supported by density functional theory and NMR spectroscopy experiments. The mechanism is constituted by two discrete steps: (a) addition of OH+ to the most nucleophilic carbon atom of the aromatic ring, which is the rate-determining step, and (b) the loss of the proton from the aromatic ring.     

A convenient room temperature ipso‐nitration of arylboronic acid catalysed by molecular iodine using zirconium oxynitrate as nitrating species: An experimental and theoretical investigation

A simple and convenient protocol has been developed for ipso‐nitration of arylboronic acid catalysed by molecular iodine at room temperature, using zirconium oxynitrate as the nitrating species. The protocol is applicable to electronically diverse aryl‐ and heteroarylboronic acid moieties under mild reaction conditions with good to excellent isolated yields. Furthermore, a theoretical investigation has been performed for the same reaction, and reaction profiles are modelled using modern density functional theory (DFT). DFT‐based results support the experimentally observed results.     

Highly Efficient and Practical Method for Synthesis of 2,2′-Azino-Bis(3-Ethyl-benzothiazoline-6-Sulfonic Acid) (ABTS) and Its Diammonium Salt

A highly efficient and practical protocol for synthesis of 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) and its diammonium salt has been carried out by six steps. On comparison of the traditional methods, the present protocol has many advantages including mild reaction conditions, excellent product yields, shorter reaction steps, and no hazardous reagents. Moreover, the present protocol also provides an easy scaling and separation method.     

Titanium isopropoxide as efficient catalyst for the aza-Baylis-Hillman reaction. Selective formation of alpha-methylene-beta-amino acid derivatives

The direct formation of alpha-methylene-beta-amino acid derivatives is achieved using the aza version of the Baylis-Hillman protocol. The products are readily formed in a three-component one-pot reaction between arylaldehydes, sulfonamides, and alpha,beta-unsaturated carbonyl compounds. The reaction is efficiently catalyzed by titanium isopropoxide and 2-hydroxyquinuclidine in the presence of molecular sieves. The protocol allows for structural variation of the substrates, tolerating electron-poor and electron-rich arylaldehydes and various Michael acceptors.     

Perchloric Acid-Catalyzed Synthesis of 9-Aryl Xanthenes-9H-3,6-diol and 1,3,6,8-Tetraol in Water

Efficient syntheses of xanthenes have been described using a catalytic amount of perchloric acid in water. The high temperature and lengthy reaction time normally required for formation of xanthenes derivatives are not necessary when using a catalytic amount of perchloric acid. The method is relatively inexpensive, easily available, nonvolatile, nonexplosive, and thermally robust to catalyze the reaction at 80 °C by simple heating with good to excellent yields. The advantages of the reaction involve simple reaction protocol, simple workup, and improved synthesis in the presence of perchloric acid as catalyst.     

Green and catalyst-free synthesis of olsalazine analogs

A greener protocol for the synthesis of olsalazine analogs is reported. Olsalazine analogs are prepared in high yields by a one-pot reaction of two molecules of mesalazine with benzotriazole-activated aspartic acid and glutamic acid in water under microwave irradiation.     

Rh-Catalyzed One-Pot Reductive Alkylation of Malononitrile Under Transfer Hydrogenation Conditions

Dihydroartemisinin can be converted to its ether derivatives in good yields by reaction with different alcohols in the presence of a catalytic amount of dodecatungstophosphoric acid hydrate. Easy handling, trouble-free workup by filtration, excellent yields, and very short reaction times are some of the highlights of this protocol.     

Deoxygenation of tertiary and secondary benzylic alcohols into alkanes with triethylsilane catalyzed by solid acid tin(IV) ion-exchanged montmorillonite

We discovered an efficient protocol for the conversion of tertiary and secondary benzylic alcohols into the corresponding alkanes in good to quantitative yields by employing tin(IV) ion-exchanged montmorillonite (Sn-Mont) as a solid acid catalyst and Et3SiH as the hydride source. The reaction is likely to proceed via the S_N1-type reaction mechanism, that is, the formation of carbenium ions, followed by the addition of a hydride from the silane. The work-up of the reaction only requires simple filtration of the solid acid without any neutralization of the acid catalyst.     

A convenient one-pot three component synthesis of 3-aminoalkylated indoles catalyzed by 3-chlorophenylboronic acid

An efficient protocol was developed for the synthesis of 3-aminoalkylated indoles using 3-chlorophenylboronic acid as a catalyst under ambient temperature conditions. The three-component reaction of indoles, aromatic aldehydes and N-methyl aniline offered corresponding 3-aminoalkylated indoles in excellent yields. This protocol presents some remarkable features such as mild reaction conditions, simple workup procedure and excellent yields.     

Total synthesis of (+)-blasticidin s

The first total synthesis of the peptidyl nucleoside antibiotic, blasticidin S (1), has been achieved by the coupling reaction of cytosinine (3) and blastidic acid (2). A key step in the synthesis of cytosinine (3) is the sigmatropic rearrangement of allyl cyanate 24; this reaction provided efficient and stereoselective access to 2,3-dideoxy-4-amino-D-hex-2-enopyranose (26 a). Further elaboration of 26 a gave methyl hex-2-enopyranouronate 29, and cytosine N-glycosylation of 31 using the Vorbrüggen conditions for the silyl Hilbert-Johnson reaction furnished the differentially protected cytosinine (32) in 11 steps from 2-acetoxy-D-glucal (14) (4.0 % overall yield). Synthesis of the Boc-protected blastidic acid 47 in nine steps starting from chiral carboxylic acid 35 (23 % overall yield) utilized Weinreb's protocol for the preparation of benzyl amide 38 and Fukuyama's protocol for the synthesis of the secondary amine 40. Assembly of the protected cytosinine (32) and blastidic acid (47) by the BOP method in the presence of HOBt, and finally elaboration to 1 by deprotection of the fully protected 54 established the total synthesis of blasticidin S (1).