Formation of spiro and ansa derivatives in the reaction of 2,2,3,3,4,4-hexafluoropentane-1,5-diol with cyclotriphosphazene

Abstract

Reaction of cyclophosphazene, N3P3Cl6 (1), With the sodium derivative of the fluorinated diol, 2,2,3,3,4,4-hexafluoropentane-1,5-diol (2), in THF solution at room temperature afforded five isolated products, whose structures have been characterised by X-ray crystallography and H-1, F-19 and P-31 NMR spectroscopy: the mono-spiro compound, N3P3Cl4(OCH2CF2CF2CF2CH2O) (3), its ansa isomer (4), a di-spiro derivative N3P3Cl2(OCH2CF2CF2CF2CH2O)(2) (5), its spiro-ansa (6) isomer and the tri-spiro compound N3P3(OCH2CF2CF2CF2CH2O)(3) (7). Quantitative P-31 NMR measurements of the soluble portion of the reaction mixture show that in the reaction of (1) with the sodium derivative of the fluorinated pentanediol (2) there is a small preference for spiro compounds compared to ansa compounds (ratio ca. 1.3:1), similar to the analogous reaction of (1) with the sodium derivative of the fluorinated butanediol where there is a slightly greater proportion of spiro compared to ansa compounds (ratio ca. 1.5:1). The relative proportions of spiro and ansa compounds is likely to depend on the fine balance in stabilities of the different medium-sized rings in the fluorinated pentanediol (spiro, 8- and ansa, 10-membered rings) compared to the fluorinated butanediol (spiro, 7- and ansa, nine-membered rings) derivatives of cyclophosphazene. (c) 2007 Elsevier Ltd. All rights reserved.