A NEW STRUCTURAL FORM FOR A PENTAOXYPHOSPHORANE. DIEQUATORIAL RING FORMATION IN A TRIGONAL BIPYRAMID
摘要：
Previous studies28 of structural preferences of cyclic pentaoxyphosphoranes have led to trigonal bipyramidal geometries with the ring systems, which varied from five- to eight-membered, occupying axialequatorial positions. Although inferences in mechanistic studies of reactions of cyclic phosphates and variable-temperature NMR studies of ligand-exchange behavior of oxyphosphoranes support intermediates with diequatorial ring placement, no X-ray investigations have yielded this structural form. For example, the activation of protein kinases by c-AMP has been proposed9.10 to result from attack by a functional group of the enzyme to yield a covalent complex, A. Diequatorial ring formation has also been proposed11.12 in the course of hydrolysis of epimeric phosphoranes. Only in the case of a NMR solution study by Denney and co-workers13 of monocyclic pentaoxyphosphoranes containing seven- and eight-membered rings has it been concluded that these rings reside in diequatorial position.14 This is indicated to occur in the ground state at reduced temperature where pseudorotaton has stopped, e.g., in formulations B and C, respectively.
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DOI：
10.1080/10426509508037704
被引量：
年份：
1995
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