Stereodirective effects in mixed substituent vinyloxycyclotriphosphazenes.
Reaction pathways leading to the new mixed substituent cyclophosphazenes, N(3)P(3)Cl(4)(OCH=CH(2))(OCH(2)CF(3)) and N(3)P(3)Cl(3)(OCH=CH(2))(OCH(2)CF(3))(2), have been explored. Examination of the relative isomeric yields and the spectroscopic properties of these new derivatives gave insight into the mechanism of substitution of cyclophosphazenes with oxyanions. The syntheses of the mixtures of compounds were carried out by two different synthetic pathways. The nucleophilic substitution reaction involves either the vinyloxy ((-)OCH=CH(2)) or the trifluoroethoxy ((-)OCH(2)CF(3)) ion. Either oxyanion could be reacted with the phosphazene first to be followed by the other oxyanion. A comparison of the observed pathways shows the stereoselectivity is controlled by the ring substituent with trifluoroethoxy species favoring trans substitution and the vinyloxy species favoring increased cis substitution. Density Functional Theory and NMR ((13)C, (31)P) studies show the electronic relationships between the exocyclic group and the cyclophosphazenes including transmission of electronic information throughout the phosphazene ring.
Carter
Kenneth R
KR
Department of Chemistry, University of Vermont, Burlington, Vermont 05405-0125, USA.
Calichman
Michael
M
Allen
Christopher W
CW