TY - JOUR
T1 - BINOL-3,3′-triflone N,N-dimethyl phosphoramidites
T2 - Through-space 19F31P spin-spin coupling with a remarkable dependency on temperature and solvent internal pressure
AU - Kruck, M.
AU - Munoz, M.P.
AU - Bishop, H.L.
AU - Butts, C.P.
AU - Lloyd-Jones, G.C.
AU - Frost, C.G.
AU - Chapman, C.J.
AU - Kociok-Kohn, Gabriele
PY - 2008/9/8
Y1 - 2008/9/8
N2 - 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.
AB - 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.
UR - http://www.scopus.com/inward/record.url?scp=53849147608&partnerID=8YFLogxK
UR - http://dx.doi.org/10.1002/chem.200800825
U2 - 10.1002/chem.200800825
DO - 10.1002/chem.200800825
M3 - Article
AN - SCOPUS:53849147608
SN - 0947-6539
VL - 14
SP - 7808
EP - 7812
JO - Chemistry - A European Journal
JF - Chemistry - A European Journal
IS - 26
ER -