A Regioselective Route to New Polytopic Receptors by Diaminolysis of Chlorocyclotriphosphazatriene-Containing Crown Ethers

Abstract

A general strategy is reported for the facile preparation of diamino-derivatized PNP-crowns, giving access to a large range of new host molecules of different sizes, shapes, and topology. Reactions of the tetrachloro-PNP-crown precursor 1 with polymethylene-diamines 2a-h (n ) 2-6, 8, 10, 12) proceed rapidly and regioselectively via substitution reactions of Cl at the PNP-crown-forming P-atoms; the reaction is assisted by the macrocyclic 1,3-oxy(tetraethylenoxy) substituent at the N 3 P 3 ring which provides a site for the hydrogen-bond-driven assembly of reagents 1 and 2. The products belong to three different classes of polytopic receptors: lateral macrobicycles (ansa, 5ah), bola-amphiphilic tritopic bis-crowns (bino, 6a-h), and tetratopic cylindrical macrotricycles (bisbino, 8a-h). The structures of 5, 6, 8, and 10b were established by MS and 31 P NMR spectroscopy, and an X-ray crystal structure was obtained for the bis-bino 1,3-diaminopropane PNP-crown derivative 8b. Preliminary screening by a simple TLC test of the metal-cation complexing properties of the series of compounds 5, 6, and 8 revealed their capacity to bind both harder (alkali and alkaline earth) and softer (transition) metal cations, with significant affinity being displayed toward potassium and silver cations by many of the ligands studied.

Chiral Configurations of Spirane‐Bridged Cyclotriphosphazenes

“…On the other hand, singly bridged macrocyclic phosphazene compounds (e.g. containing piperazine [5] and diamine [9,10] ) and spermine-bridged cyclotriphosphazene derivatives [6] have disubstituted cyclotriphosphazene rings, which provide multiple stereocenters and the possibility of diastereoisomers. For example, the meso and racemic forms of piperazine-bridged macrocyclic phosphazenes have been separated by column chromatography and characterised by X-ray crystallography and by 31 P NMR spectroscopy [5] [after addition of a lanthanide-containing chiral shift reagent (CSR)].…”

Chiral configurations in cyclophosphazene chemistry

“…The doubling-up of 31 P NMR signals was also observed for single-bridged compounds formed by the reaction of the cis-ansa cyclotriphosphazatriene-macrocyclic compound, 1,3-[oxy(tetraethylenoxy)]-1,3,5,5-tetrachlorocyclotriphosphazatriene, (32a), with aliphatic diamines [NH 2 -(CH 2 ) n -NH 2 , n = 2-6,8,10,12] (128, Fig. 22) [96,161] and this type of reaction opened up a convenient route to investigate the chiral configurational properties of cyclophosphazene compounds because there are multiple stereogenic centers giving rise to diastereoisomers. Although many of the products were stable in non-polar solvents at ambient temperatures, the crystals of the diamino singly-bridged compounds were not sufficiently stable for structure determination by X-ray crystallography [96,161].…”

“…Compound 32a could undergo a similar series of reactions with the secondary diamine, piperazine, to give analogous singly-bridged (bino) and doubly-bridged (bis-bino) derivatives, whose crystals were stable and suitable for X-ray structure determination [21]. The series of reactions of 32a with piperazine is similar to those with primary diamines [96,161], except that the reactions with piperazine lead to stable bridged compounds 129 (Fig. 22) and are simpler because they do not lead to formation of compounds analogous to either the spiro-ansa compound or the ansa-ansa series of compounds [21].…”

“…22) [96,161] and this type of reaction opened up a convenient route to investigate the chiral configurational properties of cyclophosphazene compounds because there are multiple stereogenic centers giving rise to diastereoisomers. Although many of the products were stable in non-polar solvents at ambient temperatures, the crystals of the diamino singly-bridged compounds were not sufficiently stable for structure determination by X-ray crystallography [96,161]. It was suggested that the most likely cause of instability in the primary amine derivatives of 32a was the presence of both P-Cl and P-NH groupings in the product 128, which could react to give polymerisation and/or decomposition products [21].…”

“…0.06-0.09 ppm [21], the similar behaviour observed for lower members of the series of diamine-bridged macrocyclic-cyclophosphazene compounds, (128) Δδ ca. 0.02-0.05 ppm, [161] and for two analogous series of singly-bridged cyclotriphosphazatriene-diamine derivatives (127; denoted as 3n3 and 4n4 series with n = 6,7,8,9) by Labarre et al [160]. Examples of structures of single-bridged cyclophosphazene derivatives giving rise to meso and racemic diastereoisomers; sterogenic properties known for compound 129 [21], but not recognised for compounds 127 [160] and 128 [96,161] …”