Nucleophilic substitution reactions of 10- and 11-membered fluorodioxy ansa cyclotriphosphazene derivatives

Abstract

The reactions of cyclophosphazenes with 10-membered ansa-{N3P3Cl4[OCH2(CF2)3CH2O] (1a)} and 11-membered ansa-{N3P3Cl4[OCH2(CF2)4CH2O] (1b)} rings with the sodium salts of methanol in a THF solution at different molar ratios were used to investigate the reaction pathways and mechanism of nucleophilic substitution at the PCl2 and PCl(OR) phosphorus atoms. The reactions afforded eleven products, whose structures have been characterized by elemental analysis, mass spectrometry, (1)H, (19)F and (31)P NMR spectroscopy and X-ray crystallography; mono-methoxy derivatives (2a, 3a, 3b), di-methoxy derivatives (5a-7a, 5b), tri-methoxy derivatives (8a, 8b) and the tetra-methoxy derivatives (9a, 9b). The X-ray crystallographic studies of four compounds (6a-8a and 8b) demonstrated unambiguously that nucleophilic substitution reactions at the ansa-ring PCl(OR) phosphorus atoms of the cyclotriphosphazene compounds N3P3Cl4[OCH2(CF2)nCH2O] n = 3 (1a) and 4 (1b) occurred with a retention of configuration for both the 10- and 11-membered fluorodioxy ansa rings, respectively. The results confirmed that the reactions with 1a containing the 10-membered ansa-ring occurred competitively at both the PCl2 and P(OR)Cl moieties with an approximate 8 : 1 preference at the PCl2 group, whereas reactions with 1b containing the 11-membered ansa-ring occurred exclusively at the PCl2 group before the P(OR)Cl moiety. The results were mainly rationalized in terms of the P-Cl bond lengths of the reactants and the cation-assisted mechanism of reaction.

Silver(I) coordination polymers assembled from flexible cyclotriphosphazene ligand: structures, topologies and investigation of the counteranion effects

“…The P-N bond distances (Table S1) range from 1.5744 (15) Å for P3-N3 to 1.5836 (15) Å for P1-N1. The N-P-N and P-N-P angles range from 121.60 (9) to 122.46 (9) and 117.24 (8) to 117.65 (8) , respectively, and are well matched with those observed in cyclic phosphazenes (Beşli et al, 2007(Beşli et al, , 2013Beşli, Coles, Davies, Kiliç, Okutan et al, 2011;Beşli, Coles, Davies, Kiliç & Shaw, 2011;Eçik et al, 2012).…”

Chiral configurations in cyclophosphazene chemistry

“…It is not possible meso form for Type II(4), Type II(5), Type II(7) Type II (8) and Type II (9) configurations. Hence all derivatives would be racemates which are shown for Type II(5) cis (55* [64], 56a [93], 56b [82]), Type II(5) trans (57 [76]), Type II(7) cis (58 [50]). …”

“…15). Compounds 88a and b [93] as the configuration isomers are excellent examples for two of three cis-cis-trans forms of Type III(1) (a, b or c). These compounds are diastereoisomers (two racemic forms), in which the methoxy groups are trans for 88a (SR′S″/RS′R″) or cis for 88b (SS′R″/RR′S″).…”

“…The interchange of X and Y for the trans doesn't lead to a stereoisomer whereas it is possible that the interchange of X and Y causes a configurational change giving a stereoisomer for the cis form. The diastereoisomeric crystal examples of the cyclotriphosphazene derivatives including pseudoasymmetric centres (72 and 73 [93]; 74 [37] and 75* [104]) for Type II(2) and Type II (6), respectively are shown. The sterochemistry of these compounds can be assigned as R,r,S/S,s,R (cis-meso-1) or R,s,S/ S,r,R (cis-meso-2).…”