1988-75-6Relevant academic research and scientific papers
An attractive route to transamidation catalysis: Facile synthesis of new o-aryloxide-N-heterocyclic carbene ruthenium(II) complexes containing trans triphenylphosphine donors
Nirmala, Muthukumaran,Prakash, Govindan,Viswanathamurthi, Periasamy,Malecki, Jan Grzegorz
, p. 15 - 26 (2015/04/14)
Well-defined robust ruthenium(II) complexes 3a-d bearing o-aryloxide-N-heterocyclic carbene ligands with different wingtip substituents (3a (R = Me), 3b (R = Ph), 3c (R = iPr) and 3d (R = Mes)) in the imidazole ring were synthesized in good yields by the reaction of imidazolium proligands with metal precursor [RuHCl(CO)(PPh3)3] by transmetallation from the corresponding silver carbene complexes. All the Ru(II)-NHC complexes have been characterized by elemental analyses, spectroscopic methods as well as ESI mass spectrometry. The molecular structure of the complex 3a was identified by means of single-crystal X-ray diffraction analysis, which revealed that the complexes possess a distorted octahedral geometry. In order to explore the catalytic potential of the synthesized complexes, all the four [Ru-NHC] complexes [3a-d] were tested as catalysts for transamidation of carboxamides with amines. Notably, the complex 3a was found to be very efficient and versatile catalyst toward transamidation of a wide range of amides with amines.
(Diacetoxyiodo)benzene-Lithium Bromide as a Convenient Electrophilic Br+ Source
Braddock, D. Christopher,Cansell, Gemma,Hermitage, Stephen A.
, p. 461 - 464 (2007/10/03)
A mild and versatile procedure for the bromination of olefins and activated arenes by in situ generation of 'Br+' using (diacetoxyiodo)benzene and lithium bromide is presented. The reactions were carried out in open vessels at room temperature and were typically complete in 30 minutes. The brominated products were isolated by column chromatography, which also allowed for the isolation of the iodobenzene by-product for recycle.
Reactivity and selectivity of aryloxylium ions
Hegarty, Anthony F.,Keogh, Joseph P.
, p. 758 - 762 (2007/10/03)
The reactivity and selectivity of aryloxylium ions in acetonitrile-water mixtures are described. The 4-bromo-2,4,6-trialkylcyclohexa-2,5-dienones used as substrates were synthesised by electrophilic bromination in yields of 60% (3 R = Me) and 52% (7 R = B
Solid-phase bromination of hindered phenols
Vol'eva,Belostotskaya,Komissarova,Ershov
, p. 1249 - 1251 (2007/10/03)
The solid-phase bromination of a series of tert-butyl-substituted phenols with N-bromosuccinimide and dioxane dibromide afforded halogenated cyclohexadienones, quinobromides. Under the extrusion conditions, the latter underwent further transformations, mainly, debromination. A new reaction, dioxane dibromide catalyzed anhydro-heterocyclization of 2,2′-dihydroxy-3,3′,5,5′-tetra-tert-butyldiphenyl to 2,4,6,8-tetra-tert-butyldibenzofuran, was discovered and the mechanism of this reaction was proposed.
Bond Fixation in Annulenes. 14. Synthesis of and Bond Shifting Equilibrium between 1,4- and 1,6-Di-tert-butylcyclooctatetraenes
Paquette, Leo A.,Hefferon, George J.,Samodral, Rodney,Hanzawa, Yuji
, p. 1262 - 1266 (2007/10/02)
Photolysis of the Diels-Alder adduct of 3,6-di-tert-butyl-o-benzoquinone and cyclobutadiene at ice-bath temperatures afforded the bicyclooctatriene 12.During warming to room temperature, this hydrocarbon underwent kinetically first-order valence isomerization to provide 5 and its bond shift isomer 4.This finding adumbrated the facility with which 4 and 5 are interconverted.Reaction of this cyclooctatetraene mixture with N-methyltriazolinedione gave urazoles 16 and 17 as chromatographically separable entities.Like 13, the related cycloadduct of 12 wherein both bridgehead tert-butyl groups exhibit restricted rotation , the angular tert-butyl substituent in 17 is sterically perturbed.Hydrolysis-oxidation of either 16 or 17 returned only mixtures of 4 and 5 because of their rapid bond shifting rates.When the equilibrium constant between these two isomers was determined by 1H NMR spectroscopy, it was found that 5, the apparently more congested compound, was the more stable in CDCl3 solution.The possible underlying causes of this phenomenon are discussed.
