Selective reactivity of the phosphorus-chlorine and carbon-chlorine bonds in cyclic chlorocarbaphosphazenes: An unusual activation of a carbon-nitrogen bond in trialkylamines

Acyclic tertiary amines such as triethylamine and tri-n-propylamine used as HCl scavengers in nucleophilic substitution reactions of cyclic chlorocarbaphosphazenes [N3PC2Cl4 (I) and N3P2CCl5 (II)] with (CF2)(n)(CF2CH2OH)(2) [n = 0 (III) or 1 (IV)] are found to undergo a facile C-N bond cleavage with the regiospecific substitution of the dialkylamino groups on the ring carbon atoms of the carbaphosphazene. In the case of cyclic amines such as 1-methylpiperidine and 4-methylmorpholine, the cleavage was found to occur regiospecifically at the N-CH3 bond, resulting in the ring substitution of the cyclic secondary amino group on the dicarbaphosphazene ring carbon atoms, The polyfluoro diol III forms a spirocyclic ring exclusively at the phosphorus site in compounds CF2CH2O](2)PN3C2N(C2H5)(2)](2) (1), CF2CH2O](2)PN3C2N(C3H7)(2)](2) (2), [CF7CH2O](2)PN3C2[NCH2(CH2)(3)CH2](2) (3), and [CF2CH2O](2)PN3C2[N(CH2)(2)O(CH2)(2)](2) (5) along with the formation of carbon-substituted carbaphosphazenes, Cl2PN3C2[NCH2(CH2)(3)CH2](2) (4) and Cl2PN3C2[N(CH2)(2)O(CH2)(2)](2) (6) Reaction of II with III in the presence of triethylamine affords the dispiro product [CF2CH2O)(2)P2N3C[N(C2H5)(2)] (7), which crystallizes in a polar orthorhombic space group, Cmc2(1). Upon refluxing of I or II with R3N (R = C2H5, n-C3H7) in toluene, the amino-substituted carbaphosphazenes, Cl2PN3C2[N(C2H5)(2)](2) (8), Cl4P2N3C[N(C2H5)(2)] (9), and Cl4P2N3C[N(n-C3H7)(2)] (10) are obtained in good yields. Hydrolysis of 8 leads to the formation of Cl(O)PN(H)N2C2[N(C2H5)(2)](2) (11). When lithium salts of the fluoro diols III and IV are reacted with I or II in diethyl ether, the P-CI bond is selectively substituted, yielding the spirocyclic [CF2CH2O](2)PN3C2Cl2 (12), [CF2(CF2CH2O)(2)]PN3C2Cl2 (13), [CF2CH2O](2)P2N3CCl3 (14), and [(CF2CH2O)(2)](2)P2N3CCl (15). The C-Cl bonds in 12 and 14 were easily substituted by their reaction with 4-FC6H4XNa (X = O or S) to form [CF2CH2O](2)PN3C2[4-FC6H4O](2) (16) and [CF2CH2O](2)PN3C2[4-FC6H4S](2) (17). Reactions of 12 and 13 with (CH3)(3)SiN(CH3)(2) under mild conditions result in the elimination of (CH3)(3)SiCl along with the formation of [CF2CH2O](2)PN3C2[N(CH3)(2)](2) (18). The X-ray analyses of 13 and 18 represent the first examples of eight-membered spirocyclic phosphazenes. The thermal behavior of II, 9, 10, 14, and 15 has also been investigated at 120 degrees C. Single-crystal X-ray diffraction studies were carried out for 1, 2, 7, 9-14, and 16-19, and these compounds are also characterized using IR, H-1, C-13, F-19 and P-31 NMR spectroscopy, MS, and elemental analysis.