Regiochemical Control in the Substitution Reactions of Cyclotriphosphazene Derivatives with Secondary Amines

The substitution reactions of the monospiro and geminally disubstituted cyclotriphosphazene derivatives N3P3Cl4R2 (R-2 = OCH2(CF2)(2) CH2O (1a), SPh (1b), OCH2CH2CH2O (1c), NHPh (1d), OCH2CH2CH2NH (1e), NHBut (1f) with two secondary amines (pyrrolidine and dimethylamine) were carried out to investigate geminal or non-geminal directing effects in mixed substituent cyclophosphazenes. The relative amounts of isomeric products, geminal and non-geminal trans or cis, was established quantitatively from the P-31 NMR spectra of the reaction mixtures. Although secondary amines generally follow a non-geminal pathway in the reactions with hexachlorocyclotriphosphazene, in this work, the reactions of two different secondary amines with some N3P3Cl4R2 (R-2 = OCH2CH2CH2NH, NHPh, NHBut) derivatives lead to the formation of geminal products. We have shown that this observation depends on the electron-donating properties of the PR2 groups. Isolated compounds were analyzed by standard techniques such as elemental analysis, mass spectrometry, and H-1 and P-31 NMR spectroscopy. The structures of compounds for which suitable crystals could be obtained were characterized by X-ray crystallography.