A cis-directing effect towards diols by an exocyclic P-NHR moiety in cyclotriphosphazenes

Abstract

Cyclophosphazenes containing the P-NHR moiety in an exocyclic spiro ring, N3P3Cl4[NH(CH2)(3)O], (1), and N3P3Cl4[NH(CH2)(3)NMe], (2). were used to investigate a possible directing effect of the P-NHR moiety oil the formation of products in the nucleophilic substitution reactions with diols Such as tetraethyleneglycol, 1,3-propanediol and 2,2-dimetliyl-1,3-propanediol. The P-31 NMR spectra of the reaction Mixtures showed that only one kind of ansa product is formed in each of these reactions. X-ray crystallographic studies of the ansa products [(4a), (5a), (6a) and (7a)] have provided definitive proof of the cis-directing effect of the P-NHR moiety in cyclotriphosphazenes. It is likely that hydrogen-bond interaction between the incoming nucleophile and the P-NHR moiety of the reactant accounts for the preference for products with the substituents cis to the NH group. (C) 2009 Elsevier B.V. All rights reserved.