- Selective iron-catalyzed cross-coupling reactions of Grignard reagents with enol triflates, acid chlorides, and dichloroarenes
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Cheap, readily available, air stable, nontoxic, and environmentally benign iron salts such as Fe(acac)3 are excellent precatalysts for the cross-coupling of Grignard reagents with alkenyl triflates and acid chlorides. Moreover, it is shown that dichloroarene and -heteroarene derivatives as the substrates can be selectively monoalkylated by this method. All cross-coupling reactions proceed very rapidly under notably mild conditions and turned out to be compatible with a variety of functional groups in both reaction partners. A detailed analysis of the preparative results suggests that iron-catalyzed C-C bond formations can occur via different pathways. Thus, it is likely that reactions of methylmagnesium halides involve iron-ate complexes as the active components, whereas reactions of Grignard reagents with two or more carbon atoms are effected by highly reduced iron-clusters of the formal composition [Fe(MgX)2]n generated in situ. Control experiments using the ate-complex [Me4Fe]Li2 corroborate this interpretation.
- Scheiper, Bodo,Bonnekessel, Melanie,Krause, Helga,Fuerstner, Alois
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p. 3943 - 3949
(2007/10/03)
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- The Synthesis and Transition Temperatures of Some 4,4"-dialkyl- and 4,4"-Alkoxyalkyl-1,1':4',1"-terphenyls with 2,3- or 2',3'-difluoro Substituents and of their Biphenyl Analogues
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The tetrakis(triphenylphosphine)palladium(o)-catalysed coupling of arylboronyc acids with aryl halides is used to prepare several 4,4"-dialkyl- and 4,4"-alkoxyalkyl-1,1':4',1"-terphenyls with 2,3- or 2',3'-difluoro substituents and their related biphenyl systems.Lithiation ortho to a 1,2-difluoroaromatic unit provides the route to the 2,3-difluoroarylboronic acids.The 2,3-difluoro substituted terphenyls are low-melting liquid crystals with wide-range Sc phases and no underlying smectic phase; these compounds are excellent hosts for ferroelectric systems.The compounds with widest Sc ranges are those with the difluoro substituents in an end ring and the compounds with difluoro substituents in the central ring show more nematic character and so are useful for ECB devices.
- Gray, George W.,Hird, Michael,Lacey, David,Toyne, Kenneth J.
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p. 2041 - 2054
(2007/10/02)
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- MESOGENIC AND NON MESOGENIC CENTRAL RIGID CORES.
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The mesogenic power of several central rigid cores is measured by means of depolarized Rayleigh scattering. It is shown that there is a close relation between the angular correlation parameter J and the mesogenic power that lead us to define mesogenic and
- Destrade,Tinh,Gasparoux
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p. 273 - 288
(2007/10/02)
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