Copper(ii) complexes incorporating poly/perfluorinated alkoxyaluminate-type weakly coordinating anions: Syntheses, characterization and catalytic application in stereoselective olefin aziridination

Yang Li, Jiayue He, Vineeta Khankhoje, Eberhardt Herdtweck, Klaus Köhler, Oksana Storcheva, Mirza Cokoja, Fritz E. Kühn

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Abstract

The synthesis and characterization of a series of cationic copper(ii) complexes of the type [Cu(NCR)6][Al(OC(CF3) 2R′)4]2 (R = CH3, Ph; R′ = CF3, Ph, PhCH3), incorporating poly/perfluoronated alkoxyaluminates as weakly coordinating anions (WCAs) is presented. Aziridination of various olefins, such as the unreactive olefins e.g. ethylhex-2-enoate and 1-decene, with N-tosyliminophenyliodinane catalyzed by [Cu(NCR)6][Al(OC(CF3)2R′) 4]2 affords very good yields (up to 96%) and high TOFs (up to 5000 h-1) under mild conditions. Using disubstituted olefins as substrates, high stereoselectivities are obtained at room temperature. The to date highest cis:trans ratio (98:2) of the obtained aziridines is achieved for cis-stilbene in good yield (85%) as well as promising TOF (> 2000 h -1). The investigation of the solvent effect on yield and selectivity reveals that for certain oleophilic substrates (1-decene), less polar solvents, such as dichloromethane are a better choice than acetonitrile, which is commonly considered as the best solvent for olefin aziridination. Accordingly, a mechanism involving a paramagnetic copper nitrene intermediate with both concerted and stepwise pathways is proposed.

Original languageEnglish
Pages (from-to)5746-5754
Number of pages9
JournalDalton Transactions
Volume40
Issue number21
DOIs
StatePublished - 7 Jun 2011

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