N,N-Spiro bridged bis(cyclotriphosphazene) derivatives with four equivalent chiral centres: Synthesis, characterization and stereogenic properties

Abstract

N,N-Spiro bridged bis(cyclotriphosphazene) derivatives having four equivalent centres of chirality were prepared and their stereogenic properties were investigated. Bis non-geminal trans-dibenzylaminocyclotriphosphazene {trans-P3N3Cl4[N(CH2Ph)(2)](2)}, (1) and cis-mono ansa 2,2,3,3-tetrafluoro-1 ',4 '-butanedioxycyclotriphosphazene, {P3N3Cl4[OCH2(CF2)(2)CH2O]} (2), which have two chiral centres, were used as starting compounds and their de-protonation reactions resulted in the formation of the N, N-spiro bridged bis(cyclotriphosphazene) derivatives (3a,b and 6a,b). All new isolated compounds were analysed by elemental analysis, MALDI TOF mass analysis and NMR spectroscopy. In addition, the molecular structure of 3a was determined by X-ray crystallography. This new heterocyclic compound with four equivalent chiral centres (3a) exists as trans-cis geometric isomer and is meso due to centre and plane of symmetry. The chiral properties of the compounds (3a and 6a) were determined by X-ray crystallography and were supported by P-31 NMR spectroscopy on addition of the chiral solvating agent (CSA) (R)-(+)- 2,2,2-trifluoro-1-(90-anthryl) ethanol.