Cu-catalyzed efficient synthetic methodology for ebselen and related Se-N heterocycles

An efficient copper-catalyzed method for the synthesis of biologically important ebselen and related analogues containing a Se-N bond has been developed. This is the first report of a catalytic process of selenation and Se-N bond formation reaction. Copper-catalyzed reaction tolerates functional groups such as amides, hydroxyls, ethers, nitro, fluorides, and chlorides. The best results are obtained by using a combination of potassium carbonate as a base, iodo- or bromo-arylamide substrates, selenium powder, and copper iodide catalyst.     

锆诱导的五元环化合物的新和成

由锆杂五元环化合物出发合成五元环有机化合物,只要求一个碳单元并且形成两个碳-碳链,从以下四个方面描述了利用锆杂环化物合成五元环有机化合物的新合成方法：(1)CO或RNC的插入反应;(2)与丙炔酸酯的加成反应-峡谷次的Michael加成;(3)与碘代丙烯酸酯或碘代环烯酮的偶联加成反应-先偶联后Michael加成;(4)与酰氯的取代加成反应-先亲核取代后亲核加成,每类反应都含有数个简单反应类型。     

New synthetic methodology for 3-aminotropones

A new synthetic methodology for 3-aminotropones is described. Tropones and 3-aminotroponic building blocks, present in a number of active natural products, could be prepared by a two step synthetic pathway: a first step consisting in a [4+3] cycloaddition reaction between a conveniently substituted α,α′-dihaloketone and a furan derivative functionalized on C-2 by a protected amino group. The second step is based on a rearrangement of the cycloadduct, via the cleavage of the oxygen bridge, under basic conditions.     

Copper complex catalyzed asymmetric monosulfonylation of meso-vic-diols

Asymmetric desymmetrization of meso-vic-diols was performed by tosylation in the presence of copper(II) triflate and (R,R)-Ph-BOX as a catalyst. The method was successfully applied to asymmetric desymmetrization of cyclic and acyclic meso-vic-diols in high enantioselectivity with up to >99% ee.     

Copper catalyzed C-H functionalization for direct Mannich reactions

A protocol for a practical and direct addition of α- and γ-alkyl azaarenes to N-sulfonyl aldimines has been developed. Copper salts act as efficient Lewis acid catalysts for direct Mannich-type reactions providing a mild and fast access to various functionalized heterocycles.     

Copper catalyzed arylation of urea

An efficient copper catalyzed amidation of aryl iodides with urea is described. This method is milder than the palladium catalyzed arylation and avoids the use of toxic phosphine ligands.     

Copper mediated defluorinative allylic alkylation of difluorohomoallyl alcohol derivatives directed to an efficient synthetic method for (Z)-fluoroalkene dipeptide isosteres

Difluoroallylation of optically pure O-silylated (S)-2-methyl-3-hydroxypropanal 10a with bromodifluoropropene mediated by indium provided the corresponding difluorohomoallyl alcohol 11a with low diastereoselectivity, but without a decrease in optical purity. Defluorinative allylic alkylation of each diastereomer of the difluorohomoallyl alcohol efficiently proceeded by the reaction with trialkylaluminium and Cu(I) system or Grignard reagent and a catalytic amount of CuI system in THF to give the fluorine-substituted allylic alcohol 12 in an high yield and in an excellent Z selective manner. Subsequent imidate Claisen rearrangement of the allylic alcohol 12 proceeded with a complete 1,3-chirality transfer to give the fluoroalkene dipeptide isostere structure 14 after the final conversion of the primary alcohol 20 into the carboxylic acid form.     

Copper catalyzed magnesium-Barbier reaction for γ-selective alkyl-allyl coupling

CuCN catalyzed alkyl-allyl coupling under magnesium-Barbier conditions occurs regioselectively and affords predominantly the γ-products in good to high yields. This one-pot CuCN catalyzed reaction utilising Mg, an alkyl halide and an allylic substrate in THF at room temperature provides an easy alternative to the classical CuCN catalyzed γ-allylation of alkyl Grignard reagents.     

Copper catalyzed arylation with boronic acids for the synthesis of N-aryl purine nucleosides

The synthesis of a series of N¹-aryl inosine and guanosine derivatives is described. The procedure for chemoselective N¹-arylation involves the mild oxidative copper(II) mediated coupling with boronic acids. This approach provides access to substituted N¹-aryl purines with interesting structural characteristics and novel scaffolds for drug discovery.     

从炔烃衍生物出发的有机合成方法学

研究了过渡金属催化的炔烃衍生物的异构化反应.从α,β-炔酮、2-炔酸酯和2-炔酸酰胺可以生成相应的(E,E)-共轭双烯酮、双烯酸酯和双烯酸酰胺.首次从2-炔醇异构化为相应的2-烯酮或2-烯醛.这一反应具有简单、高产率和立体选择性的优点.假设反应烯经过连二烯中间体,然后再异构化成产物,这一反应提供了方便而有潜在应用价值的方法以制备天然产物合成时的重要中间体.     

Copper catalyzed access to functionalized oxazoles from oximes via carbenoids

An operationally simple, economical and straightforward synthesis of diverse oxazoles from oximes possessing a vicinal carbonyl group has been achieved by treatment of the latter with terminal diazo compounds like ethyl/benzyl diazoacetate and diazoacetophenone (which act as carbenoids) in one pot. At least two reducible functional groups (two ester groups or cyano?+?ester) are simultaneously introduced in one step. This reaction involves expulsion of a molecule each of N₂ and water only as byproducts under copper catalysis. The structure of one of these oxazoles is confirmed by X-ray crystallography. Both the ester groups in the oxazole product could be reduced to alcohol moieties by using NaBH₄/EtOH.     

ZrCl4 as an efficient catalyst for a novel one-pot protection/deprotection synthetic methodology

A catalytic quantity of ZrCl 4 (20 mol %) was found to be an efficient catalyst for the one-pot esterification and deprotection of (5 S,6 R)-5,6-diacetoxyoct-7-enoic acid in good yields (44-62%) with a lactone formed as a minor byproduct. ZrCl 4 (10-20 mol %) was also sufficient to deprotect 1,3-dioxalane, bis-TBDMS ethers, and diacetate functional groups in excellent yields of up to 93%. ZrCl 4 (1-10 mol %) also promoted diol protection as the acetonide in 90% yield and acted as a trans-esterification catalyst for a range of esters.     

Copper catalyzed Gomberg-Buchmann-Hey reaction using aryldiazonium tosylate

Copper catalyzed modification of Gomberg-Bachmann-Hey reaction to synthesize symmetrical/unsymmetrical biaryls via diazotization of anilines with p-TSA and NaNO₂ system at 50 °C, in aromatic liquids as solvents and second partners was successfully developed. Aniline and 3-nitronaniline gave biphenyl and 3-nitrobiphenyl, respectively, with moderate yields. All para-substituted anilines gave comparatively higher yields while in the other cases including ortho-substituted anilines yields were lower. Except anilines with o-NHCOCH₃ and o-CONH₂ which gave symmetrical biaryls, all others gave selectively unsymmetrical biaryls.     

Copper catalyzed enantioselective allylic substitution by MeMgX

Methyl Grignard undergoes highly regio (>90/10) and enantioselective (ee 91-96%) copper catalyzed allylic substitution on cinnamyl-type chlorides. CuBr (3%) and 3.3% of a chiral phosphoramidite ligand are sufficient for a complete reaction. The synthesis of a precursor of (+)-Naproxen is described. The reaction can be extended to alkyl substituted allylic chlorides (ee 72%).     

Copper catalyzed synthesis of seven and higher membered heterocycles

Nitrogen, oxygen, and sulfur-containing heterocycles have a wide range of biological activities. Metal catalysts are used in organic reactions with high activity. New methods have been explored for the synthesis of heterocyclic compounds in the past few years. The preparation of heterocycles with the assistance of metal catalyst is becoming a highly rewarding strategy in organic synthesis. In this review article, the synthesis of seven and higher-membered heterocycles is presented using copper as a catalyst.     

Efficient synthetic route for thio-triazole derivatives catalyzed by iron doped fluorapatite

Research on Chemical Intermediates - Novel heterogeneous iron doped fluorapatite (Fe-FAp) catalysts were prepared by co-precipitation in the presence of amino acids, glutamic acid, aspartic acid,...     

Cyanoesterification of norbornenes catalyzed by palladium: facile synthetic methodology to introduce cyano and ester functionalities via direct carbon-carbon bond cleavage of cyanoformates

Addition of cyanoformates (NC-COOR) to norbornene at 110 °C in the presence of Pd(PPh₃)₄ (10 mol %) as a catalyst affords with high selectivity the corresponding doubly functionalized polar norbornane derivatives bearing both cyano and ester groups. By using benzonorbornadiene and norbornadienes as the substrates, the reaction can be extended to synthesis of various functionalized norbornene derivatives in moderate to excellent yields. In most cases alkyl groups such as methyl, ethyl, n-propyl, iso-propyl, n-butyl, tert-butyl, and benzyl in the ester functionalities are applicable to the reactions. Oxidative addition of cyanoformates to Pd(0), insertion of norbornenes, and reductive elimination of the corresponding adducts constitute the proposed catalysis pathway.     

Copper catalyzed synthesis of highly substituted pyrrole and isoindole derivatives

We have developed an efficient synthesis of highly substituted pyrrole and isoindole derivatives using copper(I) catalyst. This methodology is helpful for the synthesis of some quinones bearing annealed N-heterocyclic natural products.     

Copper catalyzed synthesis of benzoxazoles and benzothiazoles via tandem manner

A useful protocol for the preparation of substituted 2-aminobenzoxazoles and 2-aminobenzothiazoles was presented. Under the catalysis of copper, 2-aminophenols or 2-aminothiophenols reacted with thiocarbamoyl chlorides via a tandem manner, furnishing a series of 17 benzoheterocycles smoothly with good to excellent yields (70–91%). The broad substrate scope, short reaction time, mild react conditions, easy performance and nice yields make this approach attractive, showing its practical synthetic value for the preparation of some biologically or pharmaceutically active compounds.