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

The substitution reactions of the monospiro and geminally disubstituted cyclotriphosphazene derivatives N3P3Cl4R2 (R2 = OCH2(CF2)2CH2O (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 31P 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 (R2 = 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 1H and 31P NMR spectroscopy. The structures of compounds for which suitable crystals could be obtained were characterized by X-ray crystallography