999 resultados para INTERNAL ALKYNES


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A range of arylgold compounds have been synthesized and investigated as single-component catalysts for the hydrophenoxylation of unactivated internal alkynes. Both carbene and phosphine-ligated compounds were screened as part of this work, and the most efficient catalysts contained either JohnPhos or IPr/SIPr. Phenols bearing either electron-withdrawing or electron-donating groups were efficiently added using these catalysts. No silver salts, acids, or solvents were needed for the catalysis, and either microwave or conventional heating afforded moderate to excellent yields of the vinyl ethers.

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[Rh(OH)6]3− intercalated Ni–Zn mixed basic salt (Rh/NiZn) acts as an efficient catalyst for the hydrophenylation of internal alkynes with arylboronic acids under mild conditions. The turnover number per Rh site approached 740 in the reaction between 4-octyne and phenylboronic acid. The catalytic monomeric Rh(III) complex is stabilised within the NiZn interlayers, attributable to a strong electrostatic interaction, promoting its re-use.

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A wide range of palladium catalysed regio- and stereo-specific 5-, 6- and 7-exo-dig mono-, bis- and tris-cyclisation processes of aryl and vinyl halides and allylic acetates are described. The mono- and bis-cyclisation processes terminate in hydride capture from piperidine-formic acid or sodium formate. Addition of TI2CO3 results in alkyne-allene isomerisation and leads, after cyclisation, to 1,3-dienes which give Diels-Alder adducts in good yield. Copyright (C) 1996 Elsevier Science Ltd

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A Pt catalysed hydrometallation reaction has been developed that provides b-metallated products as a single region and geometric isomer. The reaction is incredible tolerant of sterics and actually performs better in more sterically congested stubstrates. We have demonstrated this approach in hydrosilylations, hydrostannylations and hydroboronations. We have shown a wide range of silanes to participate in this reactions and a Denmark type one-pot hydrosilylation-Hiyama coupling has been achieved as a single regioisomer. The regioselectivity has been probed for internal alkynes and we have discovered that the regioselectively is determined by both steric and electronic factors. We can selectively form either the a or b-products as a single regioisomer by altering the steric environment and we have discovered that electronic effects overide the sterics.

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Inexpensive and commercially available nano-powder magnetite is an excellent catalyst for the addition of acid chlorides to internal and terminal alkynes, yielding the corresponding chlorovinyl ketones in good yields. The process has been applied to the synthesis of 5-chloro-4-arylcyclopent-2-enones, 3-aryl-1H-cyclopenta[a]naphthalen-1-ones, and (E)-3-alkylidene-2,3-dihydro-1H-cyclopenta[a]naphthalen-1-ones, just by changing the nature of the starting acid chloride or the alkyne. All tested processes elapse with an acceptable or excellent regio- and stereo-selectivity. Moreover, the use of the iridium impregnated on magnetite catalyst permits the integration of the chloroacylation process with a second dehydrochlorination–annulation process to yield, in one-pot, 1-aryl-2,4-dialkylfurans in good yields, independently of the nature of the starting reagents, and including the heteroaromatic ones.

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The impact of service direction, service training and staff behaviours on perceptions of service delivery are examined. The impact of managerial behaviour in the form of internal market orientation (IMO) on the attitudes of frontline staff towards the firm and its consequent influence on their customer oriented behaviours is also examined. Frontline service staff working in the consumer transport industry were surveyed to provide subjective data about the constructs of interest in this study, and the data were analysed using structural equations modelling employing partial least squares estimation. The data indicate significant relationships between internal market orientation (IMO), the attitudes of the employees to the firm and their consequent behaviour towards customers. Customer orientation, service direction and service training are all identified as antecedents to high levels of service delivery. The study contributes to marketing theory by providing quantitative evidence to support assumptions that internal marketing has an impact on services success. For marketing practitioners, the research findings offer additional information about the management, training and motivation of service staff towards service excellence.