نتایج جستجو برای: heck cross
تعداد نتایج: 491365 فیلتر نتایج به سال:
[reaction: see text] A palladium-catalyzed decarboxylative arylation reaction was shown to produce Heck-type coupling products using a number of different arene carboxylic acid and 2-cycloalken-1-one substrates. The more conventional Heck coupling of an aryl iodide and a 2-cycloalken-1-one reactant was also briefly explored for comparison, where it was found that phosphine-free (Jeffery) condit...
Palladium(II)-mediated vinylic substitutions of organoboronic acids are known as oxidative Heck reactions and up to now there has been no ligand-supported oxidative Heck protocol, which would help in the development of new selective and efficient reactions. Larhed et al. from the University of Uppsala have developed a novel protocol in which aryl boronic acids are coupled to a variety of olefin...
The construction of carbon–carbon bonds by direct involvement two unactivated carbon–hydrogen bonds, without any directing group, ensures a high atom economy the entire process. Here, we describe simple protocol for Pd(II)/Cu(II)-promoted intermolecular cross-dehydrogenative coupling (CDC) 5-arylimidazoles, benzimidazoles, benzoxazole and 4,5-diphenylimidazole at their C-2 position with functio...
A PdII catalyst system has been used to successfully catalyse two mechanistically distinct reactions in a one-pot procedure: dehydrogenation of 2,2-disubstituted cyclopentane-1,3-diones and the subsequent oxidative Heck coupling. This auto-tandem catalytic reaction is applicable to both batch and continuous flow processes, with the latter being the first example of a tandem aerobic dehydrogenat...
The Heck coupling reactions of aryl halides and olefins were performed under the microwave assistance. Interestingly, the ultralow concentration of transition metals (in ppb) coming from the reactants could catalyze the Heck coupling reactions under microwave irradiation, without addition of any catalysts, ligands and phasetransfer agents. The influences of bases, solvents and temperature were ...
In this paper, the synthesis of a cheap, reusable and ligand-free Pd catalyst supported on MgAl layered double hydroxides (Pd/MgAl-LDHs) by co-precipitation and reduction methods is described. The catalyst was used in Heck reactions under high-speed ball milling (HSBM) conditions at room temperature. The effects of milling-ball size, milling-ball filling degree, reaction time, rotation speed an...
The synthetic potential of stereoselective, palladium-catalyzed hydro(het)arylation reactions of bi-, tri- and tetracyclic (hetero)alkenes in the presence of phospines and arsines as highly efficient ligands was studied. The mechanism of this reductive Heck reaction becomes more complex in the case of benzonorbornenes. Hydroarylation of diazabicyclo-[2.2.1]heptenes provides a stereoselective ac...
Amino alcohols have been used to introduce non-racemic chirality into macrocycles using a modular approach that relies on a Heck macrocyclisation reaction. A wide variety of macrocycles have been synthesised, and their structures studied using X-ray crystallography and molecular modelling. A fragmentation reaction encountered during the use of (S)-1,1-dimethylvalinol revealed that carboxylic ac...
A novel chelate-controlled intermolecular oxidative Heck reaction is reported that proceeds with a wide range of nonresonance stabilized alpha-olefin substrates and organoboron reagents to afford internal olefin products in good yields and outstanding regio- and E: Z stereoselectivities. Pd-H isomerization, common in many Heck reactions, is not observed under these mild, oxidative conditions. T...
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