549 research outputs found
Lost in a sea of sameness : lack of differentiation dominates the telecommunications industry
Based on our analysis of the websites and Twitter feeds of the top 30 global players in the telecom sector , telecommunications companies are hell bent on telling their customers they are no different from their competitors.
Everyone is selling similar solutions that claim to improve the customer âs business by the identical processes of :
transformation, acceleration, growth, integration, scalability, securit
Synthesis of 2-iodoynamides and regioselective [2+2] cycloadditions with ketene
The first synthesis of 2-iodoynamides is described as well as the first [2+2] cycloadditions of ketene with iodo alkynes.National Institutes of Health (U.S.) (GM 28273)Boehringer Ingelheim PharmaceuticalsMerck Research Laboratorie
A [4+4] annulation strategy for the synthesis of eight-membered carbocycles based on intramolecular cycloadditions of conjugated enynes
A [4+4] annulation strategy for the synthesis of eight-membered carbocycles is reported that proceeds via a cascade involving two pericyclic processes. In the first step, the [4+2] cycloaddition of a conjugated enyne with an electron-deficient cyclobutene generates a strained six-membered cyclic allene that isomerizes to the corresponding 1,3-cyclohexadiene. In the second step, this bicyclo[4.2.0]octa-2,4-diene intermediate undergoes thermal or acid-promoted 6-electron electrocyclic ring opening to furnish a 2,4,6-cyclooctatrienone. The latter transformation represents the first example of the promotion of 6-electron electrocyclic ring opening reactions by acid.National Institutes of Health (U.S.) (GM 28273)Pfizer Inc.National Science Foundation (U.S.). Graduate Research FellowshipAstraZeneca (Firm) (Graduate Fellowship)David A. Johnson Summer Graduate Fellowshi
Regiocontrol in the synthesis of naphthoquinones. Regiospecific synthesis of lomandrone and aristolindiquinone
Combination of the ring expansion of 3-t-butoxy-4-aryl-4-hydroxycyclobutenones to hydroxynaphthoquinones with the Hooker Oxidations of hydroxyquinones provides powerful methodolgy for the regiospecific synthesis of highly substituted naphthoquinones and related compounds. This combination is employed for the synthesis of the natural naphthoquinones, lomandrone and aristolindiquinone. Š 1993
TricycloÂ[3.3.1.03,7]nonane-3,7-diyl bisÂ(methaneÂsulfonate)
The crystal structure of the title compound, C11H18O6S2, was determined to investigate the effect of the eclipsed mesyl groups on the bond length of the vicinal quaternary C atoms. The two quaternary C atoms of the noradamantane skeleton and the two O atoms to which they are connected all located essentially in the same plane [maximum deviation 0.01â
Ă
], resulting in an eclipsing conformation of the CâO bonds. The CâC bond of the quaternary C atoms is 1.597â
(3)â
Ă
is considerably longer than the other CâC bonds of the molÂecule
Functionalization of Styrenes by CopperâCatalyzed Borylation/ orthoâCyanation and SilverâCatalyzed Annulation Processes
An efficient twoâstep method for the assembly of indanone derivatives starting from a simple vinyl arene has been developed. The sequence first involves addition of bis(pinacolato)diboron (B2pin2) and NâcyanoâNâphenylâpâmethylbenzenesulfonamide (NCTS) to a broad range of styrenes by utilizing IMesCuCl as catalyst. This step simultaneously accomplishes hydroboration of the alkene and orthoâ
cyanation of the benzene unit. The products thus obtained are further functionalized by a AgNO3/Selectfluorâmediated coupling of the BPin and cyano functionalities to annulate a new fiveâmembered ring. This combined twoâstep sequence provides a versatile method for the siteâselective derivatization of a broad range of vinyl arene substrates.A Cu and Ag sequence: The bisâfunctionalization of styrenes is accomplished through a copperâcatalyzed process that enables hydroboration of the alkene and regioselective orthoâ
cyanation of the arene. The resulting adducts are converted, by a radical cyclization process, into a cyclopentanone unit fused to the original aromatic ring. Together, these methods allow efficient cyclopentannulation of a broad range of styrene derivatives.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/115938/1/anie_201507303_sm_miscellaneous_information.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/115938/2/12683_ftp.pd
Development of a simple system for the oxidation of electron-rich diazo compounds to ketones
Evaluating the thermal vinylcyclopropane rearrangement (VCPR) as a practical method for the synthesis of difluorinated cyclopentenes : experimental and computational studies of rearrangement stereospecificity
Vinyl cyclopropane rearrangement (VCPR) has been utilised to synthesise a difluorinated cyclopentene stereospecifically and under mild thermal conditions. Difluorocyclopropanation chemistry afforded ethyl 3-(1'(2'2'-difluoro-3'-phenyl)cyclopropyl) propenoate as all four stereoisomers (18a, 18b, 22a, 22b) (all racemic). Trans-E isomer (18a), prepared in 70% yield over three steps, underwent near quantitative VCPR to difluorocyclopentene 23 (99%). Rearrangements were followed by 19F NMR (100-180 °C). While cis/trans cyclopropane stereoisomerisation was facile, favouring trans-isomers by a modest margin, no E/Z alkene isomerisation was observed even at higher temperatures. Neither cis nor trans Z-alkenoates underwent VCPR, even up to much higher temperatures (180 oC). Cis-cyclopropanes underwent [3,3]-rearrangement to afford benzocycloheptadiene species. The reaction stereospecificity was explored using electronic structure calculations and UB3LYP/6-31G* methodology allowed the energy barriers for cyclopropane stereoisomerisation, diastereoisomeric VCPR and [3,3]-rearrangement to be ranked in agreement with experiment
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