Thermodynamic vs Supramolecular Effects in the Regiocontrol of the Formation of New Cyclotriphosphazene-Containing Chiral Ligands with 1,1‘-Binaphthyl Units: Spiro vs Ansa Substitution at the N3P3 Ring
1997-12-24T00:00:00Z (GMT) by
Synthesis of new cyclophosphazene-containing chiral ligands (6−9) with 1,1‘-binaphthyl units has been achieved by stepwise dicyclosubstitution of hexachlorocyclotriphosphazene (1), with two sodium cation paired dinucleophiles derived from bis-β-naphthol (2) and tetraethylene glycol (3). The structures of the disubstitution products have been found to be addition order-dependent. In particular, the substitution pattern of the 1,1‘-binaphthalene-2,2‘-dioxy substituent in the N3P3 ring [spiro (4 → 6, 7) or ansa (8, 9)] was related to whether or not the crown substituent had been incorporated into 1 beforehand. Addition of the phase transfer catalyst reagent, tetrabutylammonium bromide, to the reaction mixture of 5 + 2-Na2 led to the parallel formation of both the spiro 6 and ansa 8 isomers. Spiro vs ansa regioisomerism of the binaphthalenedioxy derivatives formed is discussed in terms of the contributions of the respective thermodynamic and supramolecular effects to the regiocontrol of substitution in the N3P3 ring. It is found that there are two main factors determining the orientation of the binaphthalenedioxy substitutent incoming to the N3P3 ring: the thermodynamic stability of seven-membered spirocycles at the P-atoms and the crown-related cation assistance of the ansa substitution at the macrocycle bearing P-atoms; the regiocontrol resulting from the supramolecular effects predominates, whenever possible. The structures of compounds 7−9 were proven by X-ray crystallography. The metal cation complexing properties of compounds 6−9 were compared by a simple TLC method. The results show that the complexing properties of the chiral binaphthalenedioxy-containing PNP-crown ligands 6−9 toward alkali metal and silver cations are either similar (spiro-ansa derivative 6) or enhanced (bis-ansa derivatives 7−9) with respect to the parent tetrachloro PNP-crown 5.