Calix[4]arene bisphosphite ligands bearing two distal 2,2'-biphenyldioxy or 2,2'-binaphthyldioxy moieties: conformational flexibility and allyl-palladium complexes

Sarkar, Arindam ; Krishnamurthy, Setharampattu S. ; Nethaji, Munirathinam (2009) Calix[4]arene bisphosphite ligands bearing two distal 2,2'-biphenyldioxy or 2,2'-binaphthyldioxy moieties: conformational flexibility and allyl-palladium complexes Tetrahedron, 65 (1). pp. 374-382. ISSN 0040-4020

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Official URL: http://linkinghub.elsevier.com/retrieve/pii/S00404...

Related URL: http://dx.doi.org/10.1016/j.tet.2008.10.031

Abstract

Achiral and chiral calix[4]arene bisphosphite ligands (2 and 3) bearing two distal 2,2'-biphenyldioxyphosphinoxy and 2,2'-binaphthyldioxyphosphinoxy moieties, respectively, have been synthesized. Each of these ligands exists in two pairs of interconverting conformations in solution. The partial cone conformer (A) of the (bis)biphenyldioxyphosphinoxy ligand 2 has been separated by fractional crystallization and its structure established by X-ray crystallography. The mechanism of interconversion of the pairs of conformers (A/B and C/D) has been probed by two-dimensional NMR spectroscopy. The 1H and 31P NMR evidence strongly supports a similar kind of exchange mechanism for ligand 3. Freezing of the cone conformer from the interconverting C/D pair of conformers of ligand 2 has been achieved by complexation with (allyl)palladium moieties. The methyl-allyl complex (2d) is moderately effective for catalytic regioselective allylic alkylation of crotyl acetate.

Item Type:Article
Source:Copyright of this article belongs to Elsevier Science.
Keywords:Calix[4]arene; Conformational Analysis; NMR Spectroscopy; P-ligands
ID Code:17767
Deposited On:16 Nov 2010 12:43
Last Modified:08 Jun 2011 06:34

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