D. S. Milbrath, J. Springer, J. Clardy
Aug 1, 1981
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Journal
Phosphorus Sulfur and Silicon and The Related Elements
Abstract
Abstract Reaction of 2-chloro-2-oxo-4,6-dimethyl-1,3,2-dioxaphosphorinane with KF and a catalytic amount of 18-crown-6-ether gives a mixture of two isomers (5a and 5b) which are anancomeric at phosphorus. While the stable isomer could be obtained pure, attempts to isolate the unstable isomer resulted in mixtures. Nmr (31P, 13C and 19F) and dipole moment measurements on the stable isomer and the isomer mixture are consistent with the presence of an axial fluorine in the stable isomer. This is strongly supported by the observation that the 5,5-dimethyl analogue of 5, contains an axial fluorene as determined by x-ray diffraction techniques. The earlier conclusion (Ref. 3) that 1JPFax > 1JPFeq in the isomeric 4-methyl analogues of 5a and 5b is supported by our investigations and a rationale for this unusual coupling relationship is put forth.