Selective 1,2-syn alkynylation of an open chain sugar: the prominent role of zinc chloride addition

Depending on the metal, solvent and protective groups, functionalized aldehydes may react through either Felkin or chelated transition states leading to the Felkin-Anh product or the 1,2-anti Felkin-Anh product, respectively. Zinc chloride addition proved to be a key aspect in order to favor 1,2-syn nucleophilic attack.     

Binuclear copper(II) complex with 2-imidazolylbenzothiazole and bridged chloride ligands

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CpLi as a base: application to palladium-catalyzed cross-coupling reaction of aryl-X or alkenyl-X (X=I, Br, OTf, ONf) with terminal acetylenes

The reaction of aryl-X or alkenyl-X (X=I, Br, OTf, ONf) with terminal acetylenes in the presence of a catalytic amount of Pd(OAc)₂ provided the alkynylated products in good yields by using Cp^∗Li (Cp^∗=1,2,3,4,5-pentamethylcyclopentadienyl) as a base.     

First example of a click-reaction on the aminate copper complexes: effect of reaction parameters

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Coupling and cycloaddition of ynamides: homo- and Negishi coupling of tosylynamides and intramolecular [4+2] cycloaddition of N-(o-ethynyl)phenyl ynamides and arylynamides

N,N′-aryl- and N,N′-alkyl-buta-1,3-diyne-1,4-ditosylamides have been synthesized for the first time, in good to excellent yields, by copper-catalyzed dimerization of the corresponding N-aryl or N-alkyl tosylynamides. Negishi coupling of N-ethynylzinc tosylamides derivatives with (hetero)aryl iodides in the presence of Pd₂dba₃ and triphenylphosphine affords N-aryl and N-alkyl arylynamides in yields of up to 90%. Intramolecular [4+2] cycloaddition reactions of N-ethynylphenyl ynamides and arylynamides allow the synthesis of carbazoles and benzannulated and heteroannulated carbazoles in moderate-to-good yields.     

Enantioselective alkynylation of carbonyl compounds with trimethoxysilylalkynes catalyzed by lithium binaphtholate

Enantioselective alkynylation of aldehydes and ketones was accomplished using trimethoxysilylalkynes as alkynylating reagents and lithium 3,3′-diphenylbinaphtholate as a catalyst. Optically active propargylic alcohols were obtained in good to high chemical yields and enantioselectivities. Alkynylation of acetylpyridines afforded biologically active pyridyl propargylic alcohols in good enantioselectivities.     

Photoredox catalyzed C(sp3)C(sp) coupling of dihydropyridines and alkynylbenziodoxolones

A visible light mediated deformylative alkynylation of aldehydes is presented. Under photo irradiation, 1,4-dihydropyridine (DHP), derived from an aldehyde, generated a C(sp³)- radical which couples with an alkynylbenziodoxolone to generate an alkyl substituted alkyne coupling product. This strategy is mild and easy to operate, a wide range of functional groups were tolerated, and 16 examples of products with 35–86% yields were obtained.     

Reductive amination of cyclohexanol/cyclohexanone to cyclohexylamine using SBA-15 supported copper catalysts

Amination of cyclohexanol was investigated in vapour phase over copper catalysts supported on mesoporous SBA-15. The different products identified during reductive amination of cyclohexanol reaction were cyclohexanone, cyclohexylamine, along with small amounts of N-Cyclohexylidinecyclohexylamine and dicyclohexylamine. Among several catalysts tested for the reductive amination, 5% Cu supported on SBA-15 exhibited better catalytic performance than other catalysts with 36% selectivity towards cylclohexylamine at 80% cyclohexanol conversion. The optimum reaction conditions employed to achieve the best catalyst performance were at 250 °C, 0.1 MPa of H₂/NH₃, TOS-10h. The active Cu sites, acidity of the catalyst, and effect of reaction parameters play a pivotal role in the reductive amination reaction. The prepared catalysts were characterized by XRD, BET, SEM, H₂-TPR and NH₃-TPD. The dispersion of Cu, particle size, and metal surface area (m²/g) calculated from pulse N₂O decomposition method. TPR findings reveal the presence of substantially dispersed copper oxide species at lower loadings which is easily reducible than the bulk copper oxide species found at higher Cu loadings. The acidity measurements by NH₃-TPD analysis suggest that the maximum acidic strength was obtained at 5 wt% copper on porous SBA-15, and decreased with Cu loadings. The catalytic properties are well in agreement with the findings of catalysts characterization.     

Developments in visible-light-mediated copper photocatalysis

The scope, applications, and understanding of photoinduced, copper-catalysis have advanced considerably in recent times. Many of these transformations exploit the distinctive properties of photoactive copper species to establish original synthetic methodology and reveal novel reactivity. In this regard, the bifunctionality of copper photocatalysts has often allowed these species to direct and influence synthetic processes in new, interesting, and exciting ways. This article summarizes recent advances in the development of copper photoredox catalysts and provides an overview of the emerging applications of these, and related systems, in organic synthesis.     

Reactivity of cyclic sulfamidates towards lithium acetylides: synthesis of alkynylated amines

A synthetically useful level of reactivity of cyclic sulfamidates toward acetylides is described. Ring-opening reactions of a structurally diverse set of 1,2- and 1,3-cyclic sulfamidates with a range of lithium acetylides from aliphatic, cyclic, aromatic, heteroaromatic, and functionalized alkynes proceed smoothly in a regioselective manner to give the corresponding N-sulfate intermediates. Hydrolysis of these intermediates under acidic conditions furnishes the alkynylated amines in yields ranging from 29% to 98%. The scope of the acetylenic substitution reaction with the structural variations in both the cyclic sulfamidates and alkynes is briefly examined.     

Acrylamide polymers with covalently linked zinc(ii)tetraphenylporphyrin groups: synthesis and complexation with amino acids

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Diastereoselective alkynylation of chiral phosphinoylimines: preparation of optically active propargylamines

Chiral phosphinoylimines were prepared from methylphenylphosphonamides and tested as new chiral and activated imines. The addition of aluminum acetylides was proved to be highly diastereoselective while lithium or magnesium acetylides gave poor results. The cleavage of the chiral auxiliary was done under mild conditions and allows the recovery of the starting phosphonamide without loss of optical purity.     

Reaction of nonstabilized azomethine ylides with Mannich bases: an approach to 3-acylpyrrolidines

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Reaction of lithium acetylides with car-3-ene-2,5-dione

The reaction of car-3-ene-2,5-dione (1), an oxidation product of (+)-car-3-ene, with lithium acetylides proceeds stereospecifically, but not regioselectively, to give only mixtures of regioisomeric acetylenic alcohols with thesyn-orientation of the hydroxy group. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 183–185, January, 1998.     

The first example of alkynylation of propargylic alcohols with alkynylsilanes catalyzed by molecular iodine

Aryl propargyl alcohols undergo smooth alkynylation with alkynylsilanes in the presence of 10 mol % of iodine under mild and neutral conditions to produce 1,4-diynes in excellent yields with high selectivity. The use of readily available molecular iodine makes this method simple, convenient, cost-effective and practical.     

Selective aerobic oxidation of benzylic amines to aryl nitriles catalyzed by CuBr2/N-methyl imidazole

A convenient and efficient copper-catalyzed aerobic oxidation of primary amines to aryl nitriles was described. Various benzylic and allylic amines were selectively oxidized to the corresponding nitriles in high yields using CuBr₂/NMI as the catalyst and O₂ as the oxidant. The oxidation reaction profiles monitored by ¹H NMR disclosed the scenario of the reaction path as well as the role of the additives. The addition of NMI increased the rate of reaction and suppressed the hydrolysis and the deamination.     

The modes of combustion of copper nanopowders

It was shown that the synthesis of Cu nanopowder by thermal decomposition afforded chemically purer (without oxides) and finer (specific surface value ～45 m2 g^?1) product than the synthesis by chemical reduction. The latter method leads to pyrophoric nanopowders containing detectable amounts of copper oxides.     

Reaction of (S)-homoserine lactone with Grignard reagents: synthesis of amino-keto-alcohols and β-amino acid derivatives

The ring-opening reaction of homoserine lactone with phenylmagnesium bromides was systematically examined. A reliable method to achieve β-amino acid precursors was developed by tuning the reaction conditions to favor mono-addition to the carbonyl moiety of the lactone.     

Half-sandwich molybdenum complexes: molecular structure and catalyst precursors for olefin epoxidation with tert-butyl hydroperoxide

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Copper(I) complex with BINAP and 3,5-dimethylpyrazole: synthesis and photoluminescent properties

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