Structural and stereogenic properties of spiro- and ansa-substituted 1,3-propanedioxy derivatives of a spermine-bridged cyclotriphosphazene


Coles, S. J., Davies, D. B., Eaton, R. J., Kilic, A., Shaw, R. A. and Ciftci, G. Y. (2006) Structural and stereogenic properties of spiro- and ansa-substituted 1,3-propanedioxy derivatives of a spermine-bridged cyclotriphosphazene. Polyhedron, 25, (4), 953-962. (doi:10.1016/j.poly.2005.10.023).

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Description/Abstract

Reaction of 1,3-propanediol with the achiral spermine-bridged cyclophosphazene 1 at various molar ratios in THF gives a number of spiro-and ansa-derivatives that exhibit different stereogenic properties, viz. racemic, meso or achiral forms. As expected, spiro forms are preferred (giving mono-, di-, tri- and tetra-substitution), although significant amounts of mono- and di-substituted ansa derivatives also occur. A number of new structures have been characterized by NMR spectroscopy and X-ray crystallography in this work; mono-spiro 2, di-mono-ansa 6 and di-spiro/mono-ansa 8. The mono-ansa compound 3 was observed in solution by NMR spectroscopy but no evidence was found for the monospiro/monoansa 5, a necessary precursor of compound 8. The tri-spiro derivative 7 has been isolated and characterized by P-31 NMR spectroscopy, whereas the structures of the di-monospiro 4 (meso) and tetra-spiro 9 have been characterized previously. The stereogenic properties of many of the products have been confirmed by X-ray crystallography and/or by P-31 NMR spectroscopy on addition of the chiral solvating agent, (S)-(+)-2,2,2-trifluoro-1-(9-anthryl)ethanol. Although the starting compound I is achiral, it is found that unsymmetrically-substituted derivatives with 1,3-propanediol give racemic mixtures for the mono-spiro 2 and tri-spiro 7 derivatives, whereas symmetrically-substituted derivatives such as di-mono-ansa 6 and di-spiro/mono-ansa 8 are meso. It is found that care must taken in interpreting the 'splitting' of P-31 NMR signals on addition of CSA in terms of 'chirality' of molecules, because some meso compounds give false positive results due to changes from A(2)X-like to A(2)B or ABX spin systems.

Item Type: Article
ISSNs: 0277-5387 (print)
Related URLs:
Keywords: cyclophosphazene derivatives, stereogenicity, nmr, chiral solvating agent, x-ray crystallography phosphorus-nitrogen compounds, crystal-structures, cyclophosphazenes, spectra
Subjects: Q Science
Q Science > QD Chemistry
Divisions: University Structure - Pre August 2011 > School of Chemistry
ePrint ID: 44411
Date Deposited: 01 Mar 2007
Last Modified: 27 Mar 2014 18:28
Contact Email Address: davidbry@ndavies.co.uk
URI: http://eprints.soton.ac.uk/id/eprint/44411

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