Single diastereomers of unsymmetrical tris-spirocyclic cyclotriphosphazenes based on 1,1′-bi-2-naphthol - Synthesis and structures

Abstract

Diastereoselective synthesis and characterization of chiral unsymmetrical tris-spirocyclic cyclotriphosphazenes based on chiral 1,1′-bi-2-naphthol (BINOL) are reported. Specifically, the chiral compounds (-)N3P 3[1,1′-O2(C10H6) 2](O-2,2′C6H4-C6H 4O)Cl2 [(-)-4] and (-)N3P3[1, 1′-O2(C10H6)2](OCH 2CH2NMe)2 [(-)-5] are prepared by starting with the chiral mono-spiro compound (-)N3P3[1,1′-O 2(C10H6)2]Cl4 [(-)-3]. Synthesis of four other chiral spirocyclics, N3P3[1, 1′-O2(C10H6)2](OCH 2CH2 NMe)(O-2,2′C6H4-C 6H4O)[(-)-6 and (+)-6], N3P3[1, 1′-O2(C10H6)2](NMe 2)4 [(-)-7], N3P3[1,1′-O 2(C10H6)2](O-2,2′C 6H4-C6H4O)(NMeCH2CH 2OH)2 [(-)-8 and (+)-8], and N3P 3[1,1′-O2(C10H6) 2](O-2,2′C6H4-C6H 4O)[NHCH2CH2CH2Si(OEt) 3]2 (9) is also reported herein. Compounds 4-6 are obtained in the solid state diastereoselectively and their X-ray structures have been determined and discussed. The diastereoselectivity is also shown by structural characterization of two distinct isomers in the case of 6 [(-)-6 and (+)-6, respectively] by starting with precursor of 3 having (R) or (S)-BINOL residue. The 1H NMR spectra of 7 and 8 exhibit doublets with virtual coupling for the methyl protons, consistent with the chiral nature of the binaphthoxy residue. The potential of 9, which hydrolyzes readily in CDCl 3 solution, as a useful precursor for chiral polymer applications is highlighted. © 2008 Wiley-Liss, Inc.