Abstract
The reaction of monocyclic oxyphosphorane compounds 1a, 1b, 1c, with ethylene glycol in pyridine was studied by 31P NMR. The results showed that compound 1a, with an unsaturated five-membered ring reacts slightly faster than compound lb with a saturated ring attached by two trans p-nitro phenyl groups, which reacts 100 times faster than the cis compound lc. To interpret the mechanism, hexacoordinated intermediates 3, and 4, were proposed. The properties of 3b, and 3c, as well as 1b, and 1c, were investigated on the basis of PM3 calculations. The calculations showed that there was about 2.9 kcal/mol difference between the active energy of the ester exchange reaction for compound 1b, and 1c, which matched well with our experimental results and provided more support to the proposed mechanism.
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