Intramolecular Aldol Condensation ofα- Oxo Ketene Dibenzylthioacetals: A Facile Route to Substituted Thiophenes

As a kind of intermediates, a-oxo ketene dithioacetals I are important in organicsynthesis"'. In our recent studies, we found that the difference of dialkythio group canbestow various properties on these kinds of compounds"'. To exploit the reactivityadjusted by the dialkythio groups in l, a-oxo ketene dibenzylthioacetals 2 were chosenand studied. Some interesting new results were obtained in these experiments. Here wereport the new results.When studying the reaction of a-oxo ketene dibenzylt…     

Condensation Reaction of α-Aroyl-α-acetyl Ketene Cyclic Dithioacetals with Aromatic Aldehydes

Asaversatilethree-carbonsynthon,a--oxoketenedimethylthioacetalsIhavebeenappliedinmanyfields'.Inourpreviousworks'-',someproperties,especiallyadditionselectivity,ofthearoxoketenecyclicdithioacetals2werefoundtobequitedifferentfromthoseof1.Herea--aroyl...     

α-Oxo Ketene Dithioacetals Chemistry-A Facile Route to the Synthesis of Fused Heterocyclic Compounds

Q-Oxo ketene dithioacetals and related compounds are versatile synthons in organicsynthesis'-'. The substitution reaction of or-oxo ketene dimethylthio acetals with diamineis one of the impel'tant applications for the synthesis of corresponding a-oxo ketenecyclic N, N-acetals. Junjappa and co-workers described this reaction ill a review'.However, since some kinds of ketene dimethylthio acetals are not easy to prepare, themethod melltioned above is limited. Zhu and co-workers had successfully…     

Synthesis of Triphenyltin 2-(1,2-Ethylenedithio) Methylene-3-Oxo-5-Aryl-4-Pentenoate

ac-oxo-ketenedithioacetalsandrelatedcompoundsareversatileSynhlonsinorghocsynthesis.'"Althoughtherehavebeennumerousreportsaboutmisfieldinrecentyears,l-6allofthestUdiescanberoughlydividedintotwoaspectsfoneistheapplicahonofac-oxo-ketenedithioacetalsinorganicsyntilesis,andtileoilleristilesindiesontilereachvityadjustCdbythedialkylthiogroupsinac-oxo-betenedi1illoacetals.WehavedevotCdoureffortstothelatter."82-(l,2-ethylenedithio)medlylene-3-oxo-5-aryl-4-pentenoacids3wereformedbycondonsahonofacylketC…     

Intramolecular Induction of Asymmetric Darzen's Condensation of Aldehydes with Chiral α-Chloroacetates

Inconvergentwithourinterestintheasymmetricsynthesisofnaturalproducts,intramolecularinductionofasymmetricDarzen'scondensationlofaldehydeswithQchloroacetatesofchiralalcoholswasstudies,asshowninScheme1.Scheme1.R*OH CICH,COCI~CICH,COOR*i(-)-menthol(450%)3( )-Jsomenthoi(i56%)5(-)-8-phenylmenthoi(74%)2( )-neomenthol(147%)4( )-f6nchol(478%)6(-)-8-11-naphthylmenthoi(99%)I-henumbersintileparenthesisilldicatedthece%oftilecorrcspondillgmethy13-pllcn}lgl}'cidatcobtainedh\'trallscstcrltiationBenza…     

A Convenient Synthesis of Pyrazolylpyrazoles Using α-Oxo Ketene S,S- and N,S-Acetals

Aryl-substitutedpyrazolederivativeshavealreadyattractedwideattentioninrecentdecadesbecausetheywerereportedtoshowabroadspectrum0fbi0logicalactivities.Forinstance,severalsubstitutedpyrazolyIpyrazoIesdemonstratedhighpreemergentherbicidalactivityagainstawidevarietyofbroadleafweedspecies"'.Pyraz0lyl-pyrimidinesexhibiteds0mefungicidalactivity'.Fripronil(5-amino-3-cyan0-l-(2',6,-dichloro-4'-trifluoromethylphenyisanewpyrazoleinsecticidethatprovidesexcellentc0ntrolofmanysoilandf0liarinsects0nawidevari…     

Azo-coupling Decarboxylation Reaction of α-Carboxy Ketene Dithioacetals in Water-a New Route to 1,2-Diaza-1,3-butadienes

Under basic conditions,a series of 4,4-dialkylthio-1,2-diaza-1,3-butadienes were synthesized in good to excel-lent yields via a novel azo-coupling decarboxylation reaction by reacting α-carboxyl ketene dithioacetals witharyldiazonium salts in aqueous medium.     

Synthesis of 3- and 5-Alkyl-6-alkyl(aryl)tetrahydropyran-2,4-diones by the Condensation of β-Oxo Acid Esters with Aldehydes and Ketones

A method is proposed for obtaining 3- and 5-alkyl-6-alkyl(aryl)tetrahydropyran-2,4-diones based on the condensation of the dianion of alkyl(dialkyl)acetoacetic ester with aldehydes and ketones.     

Synthesis of α-Hydroxy-ω-Aminotelechelic Polypeptide from α-Amino Acid N-Carboxyanhydrides Catalyzed by Alkali-metal Borohydrides

It is reported that alkali-metal borohydrides(MBH4, M = Li, Na and K) are efficient catalysts for ring opening polymerization(ROP) of α-amino acid N-carboxyanhydrides(NCAs). Polypeptides are prepared in quantitative yields with relatively narrow molecular weight distributions(MWDs = 1.1~1.5) which depend on the reaction temperature. End groups of the produced polypeptide are studied in detail by MALDI-ToF MS, 1H-NMR, 13C-NMR, 1H-1H COSY and 1H-13C HMQC analyses. The results indicate that α-hydroxy-ω-aminotelechelic polypeptides are formed which are suitable for postpolymerization functionalization.     

Synthesis of α,β-Unsaturated Ketones using Potassium fluoridealumina Catalyst by Microwave Irradiation

Microwaveirradiationhasf0undalotofapplicati0nsinrecentyears'".Thereactiontimecanbeshortenedgreatlyundermicrowaveirradiation,soitisanewandconvenientsyntheticmethod.Inprevi0uspapers"',wereportedtheethoxylationsofnitro-chlorobenzeneandreactionsofcarboxylicacidwithhalidesunderndcrowaveirradiation.a,6-Unsaturatedketonesareusefulcompounds,whosesynthesiswerenoteasybyconventionalways"9.Ontheotherhand,KF-Al2O3isanewkindofbasecatalyststhatcancatalyzemanyreactionsunderndldconditions,t0givehighcatalytic…     

Intramolecular Aldol Condensation of a - Oxo Ketene Dibenzylthioacetals: A Facile Route to Substituted Thiophenes

A new method for the synthesis of substituted thiophenes was through intramolecular aldol condensation of α-oxo ketene dibenzylthioacetals.All products were confirmed with IR,1H NMR and elemental analysis.     

5-雄烯-3β, 7α, 17β-三醇和5-雄烯-3β, 7β, 17β-三醇的合成

以5-雄烯二醇为原料,用微生物转化的方法合成了两个重要的神经甾体5-雄烯-3β, 7α, 17β-三醇和5-雄烯-3β, 7β, 17β-三醇。所用菌种总枝毛霉为我们自己筛选,并首次应用于5-雄烯-3β, 7α, 17β-三醇和5-雄烯-3β, 7β, 17β-三醇的合成中。     

An Efficient and Odorless Synthesis of Thioethers Using 2‐[Bis(alkylthio)methylene]‐3‐oxo‐N‐o‐tolylbutanamides as Thiol Equivalents

Using 2‐[bis(alkylthio)methylene]‐3‐oxo‐N‐o‐tolylbutanamides 1 as odorless thiol equivalents, an efficient and odorless synthesis of thioethers has been developed. Promoted by NaOH in EtOH, the cleavage of 1 commences to generate thiolate anions, and the generated thiolate anions then react with halides to give various thioethers in good yield. It is noteworthy that only a very faint odor of thiols can be perceived during both the reaction and the workup.     

SmI2－Mediated Addition Reaction of α－Halomethylsulfones to Carbonyl Compounds. A Convenient Synthesis of β－Hydroxysulfones

Due to the chemoselective dehalogenation by SmI2, the addition of a-halomethylsulfones to carbonyl compounds afforded ,β-hydroxysulfones. Those reactions with α-bromomethylsulfones gave the products in moderate to good yields. The SmI2-mediated addition of gem-dihalomethylsulfones to ketones also afforded α-halo-β-hydroxysulfones in moderate yields.     

Synthesis and Characterization of α-Bromo Chalcone Derivatives

α-Bromo chalcones containing 2-thiene ring were prepared in good yields by the condensation of 1-(thien-3-yl)ethanone with aromatic aldehydes, followed by bromination with bromine and selective dehydrobromination with triethyl amine at room temperature.     

胆甾-4α-甲基-8-烯-3β，7α-二醇二乙酸酯的结构与性质研究

Lophenol, cholest-4α-methyl-7-en-3β-ol (1), obtained from Dracaena cochinchinensis (Lour.) S. C. Chen, was structurally modified. It was acetylated to protect 3β-hydroxyl group, and then oxidised by selenium dioxide in acetic acid to give cholest-4a-methyl-8-en-3β, Ta-diol diacetate (3). This compound 3 is unstable in chloroform solution or when heated and easily converted to a diene compound, cholest-4a-methyl-7,14-dien-3β-ol acetate (4). The structures of 3 and 4 were elucidated by means of IR, ^1H NMR, ^13C NMR and MS, and the absolute configuration of 3 was established by X-ray crystallography. The property of 3 was also discussed in this paper. Both 3 and 4 are new compounds and were reported for the first time.     

Facile Preparation of Homoallyl β′，γ′—Unsaturated Amines via 1,2—Addition of α，β—Unsaturated Imines with Allylsamarium Bromide

A series of homoallyl β′，γ′-unsaturated amines were synthe sized via 1,2-addition of α，β-unsaturated imines with allylsamarium bromide in excellent yields under mild and neutral conditions.     

A Novel Approach to Synthesis of α，β－Unsaturated Ketones

A new approach to the synthesis of α，β-unsaturated ketones from 1,2,3-trimethyl benzimidazolium salt via the condensation reaction with aldehydes followed by the addition reaction of Grignard reagents with quaternary C=N bond was provided.     

Stereocontrolled Synthesis of (E)-β,γ-Unsaturated Esters via Palladium-Catalyzed Cross-Coupling of (E)-Alkenylboronic Acids with α-Bromoacetic Esters

The cross-coupling reaction of trans-alkenylboronic acids with a-bromoacetic esters was firstly studied. It was found that using Pd(OAc)2 as catalyst, a bulky electron-rich phospine, (2-dicyclohexylphospino-biphenyl) as ligand, the reaction can be readily accomplished to give specific (E)-b,g-unsaturated esters in high yields.