BINOL-3,3′-TrifloneN,N-Dimethyl Phosphoramidites: Through-Space19F,31P Spin-Spin Coupling with a Remarkable Dependency on Temperature and Solvent Internal Pressure

Kruck, Matthias, Munoz-Herranz, Maria, Bishop, Hannah L., Frost, Christopher G., Chapman, Christopher J., Kociok-Köhn, Gabriele, Butts, Craig P. and Lloyd-Jones, Guy C. (2008) BINOL-3,3′-TrifloneN,N-Dimethyl Phosphoramidites: Through-Space19F,31P Spin-Spin Coupling with a Remarkable Dependency on Temperature and Solvent Internal Pressure. Chemistry - A European Journal, 14 (26). pp. 7808-7812. ISSN 0947-6539

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Abstract

A combined computational and experimental study of the effects of solvent, temperature and stereochemistry on the magnitude of the through-space spin–spin coupling between 31P and 19F nuclei which are six-bonds apart is described. The reaction of 3-trifluoromethylsulfonyl-2,'2-dihydroxy-1,1'-binaphthalene (3-SO2CF3-BINOL) with hexamethylphosphorous triamide (P(NMe2)3) generates a pair of N,N-dimethylphosphoramidites which are diastereomeric due to their differing relative configurations at the stereogenic phosphorous centre and the axially chiral (atropisomeric) BINOL unit. Through-space NMR coupling of the 31P and 19F nuclei of the phosphoramidite and sulfone is detected in one diastereomer only. In the analogous N,N-dimethylphosphoramidite generated from 3,3'-(SO2CF3)2-BINOL only one of the diastereotopic trifluoromethylsulfone moieties couples with the 31P of the phosphoramidite. In both cases, the magnitude of the coupling is strongly modulated (up to 400?%) by solvent and temperature. A detailed DFT analysis of the response of the coupling to the orientation of the CF3 moiety with respect to the P-lone pair facilitates a confident assignment of the stereochemical identity of the pair of diastereomers. The analysis shows that the intriguing effects of environment on the magnitude of the coupling can be rationalised by a complex interplay of solvent internal pressure, molecular volume and thermal access to a wider conformational space. These phenomena suggest the possibility for the design of sensitive molecular probes for local environment that can be addressed via through-space NMR coupling.

Item Type: Article
Faculty \ School: Faculty of Science > School of Chemistry
Related URLs:
Depositing User: Rachel Smith
Date Deposited: 14 Feb 2012 16:39
Last Modified: 21 Apr 2020 18:57
URI: https://ueaeprints.uea.ac.uk/id/eprint/37106
DOI: 10.1002/chem.200800825

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