STRUCTURE-REACTIVITY RELATIONSHIPS FOR ASSOCIATIVE DISPLACEMENT-REACTIONS OF PENTACOORDINATE AND HEXACOORDINATE CYCLIC OXYPHOSPHORANES WITHCATECHOLS

The reactivity of a series of cyclic pentaoxyphosphoranes containing a sulfonyl group was carried out, O2S[(t-Bu)MeC6H2O](2)P(OCH2CF3)(3) (1 ), O2S[(t-BU)MeC6H2O](2)P(OPh)(3) (2), O2S[(t-BU)(2)C6H2O](2)P(OCH2CF3 )(3) (4),and O2S [(t-Bu)(2)C6H2O](2)P(OPh)(3) (5). Also included were derivatives containing sulfur, S[(t-Bu)MeC6H2O](2)P(OPh)(3) (6) and S[ (t-Bu)(2)C6H2O](2)P(OPh)(3) (8), and the methylene group, CH2[(t-Bu)Me C6H2O](2)P(OPh)(3) (7), in place of the sulfonyl group in the ring-con taining component. P-31 NMR monitoring of the reactions of the oxyphos phoranes with catechol and 4-nitrocatechol shows the following order o f reactivity: 7 > 8 > 6 > 2 > 5 much greater than 1. It is established that the reactions are associative. An analysis of the products forme d is given relative to this mechanistic process. Both 1 and 4 are foun d to be inert toward nucleophilic displacement by the catechols employ ed. It is suggested that the looseness of P-O bonds (implied by their increased length) that reside in either octahedral formulations or in axial positions of a trigonal biyramid is the principal factor associa ted with reactivity for these cyclic oxyphosphoranes. For the hexacoor dinated geometries, the order of reactivity parallels the extent of oc tahedral character: 8 > 6 > 2 > 5.