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Issue 37, 2009
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Chiral triaryl phosphite-based palladacycles and platinacycles: synthesis and application to asymmetric Lewis acid catalysis

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Abstract

The optically pure monophosphites P(OAr)(BINOLate) (7, where Ar = 2,4-di-tert-butylphenyl) have been prepared by treatment of PCl2(OAr) with R- or S-BINOL. Treatment of [PdCl2(NCMe)2] with 7 gave [PdCl2(7)2] (9) or the binuclear orthometallated complex [Pd2Cl2(7-H)2] (8) depending on the reaction conditions. Bridge cleavage reactions of 8 gave [PdCl(7-H)(L)] with L trans to carbon when L = PPh3 or 7 and cis to carbon when L = N-heterocyclic carbene. Treatment of [PtCl2(NCtBu)2] with 7 gave [PtCl2(7)2] (18) which upon further reaction with PtCl2 furnished a mixture of binuclear [Pt2Cl2(7-H)2] (17) and cis-[PtCl(7-H)(7)] (19). The palladium complexes containing cyclometallated 7 were screened for catalysis of 1,4-conjugate addition of phenylboronic acid to cyclohexen-2-one and the allylation of benzaldehyde with allyltributyltin. Conversions were generally high in each case but enantioselectivities were low (15% e.e. at best). The X-ray crystal structures of 8, 17 and [PdCl(7-H)(NHC)] (10a, where NHC = 1,3-(dimesityl)imidazolidin-2-ylidene) have been determined.

Graphical abstract: Chiral triaryl phosphite-based palladacycles and platinacycles: synthesis and application to asymmetric Lewis acid catalysis

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Publication details

The article was received on 14 Apr 2009, accepted on 15 Jun 2009 and first published on 31 Jul 2009


Article type: Paper
DOI: 10.1039/B907333G
Citation: Dalton Trans., 2009,0, 7796-7804
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    Chiral triaryl phosphite-based palladacycles and platinacycles: synthesis and application to asymmetric Lewis acid catalysis

    R. B. Bedford, H. Dumycz, M. F. Haddow, L. T. Pilarski, A. G. Orpen, P. G. Pringle and R. L. Wingad, Dalton Trans., 2009, 0, 7796
    DOI: 10.1039/B907333G

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