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

Sarkar, Arindam and Krishnamurthy, Setharampattu S and 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. In: Tetrahedron, 65 (1). pp. 374-382.

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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:	Journal Article
Publication:	Tetrahedron
Publisher:	Elsevier Science
Additional Information:	Copyright of this article belongs to Elsevier Science.
Keywords:	Calix[4]arene;Conformational analysis;NMR spectroscopy; P-ligands.
Department/Centre:	Division of Chemical Sciences > Inorganic & Physical Chemistry
Date Deposited:	04 May 2009 11:02
Last Modified:	19 Sep 2010 05:00
URI:	http://eprints.iisc.ac.in/id/eprint/18117

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