SYNTHESIS AND CHARACTERIZATION OF LARGE STEREOREGULAR ORGANOSILOXANE CYCLES

The large stereoregular phenyltrimethylsiloxysiloxane macrocycles of g eneral formula [PhSi(OSiMe3)O](n) (n = 6 and 12) have been selectively obtained with high yields by trimethylsilylation of cage-like oligoph enylmetallasiloxanes (OPMS) which we described earlier. The compounds 3 (n = 6) and 4 (n = 12) have been characterized by NMR-spectroscopy m ethod and by single crystal X-ray analysis. This investigation showed unambiguously that the siloxane macrocycles keep their size and config uration (the same as in the initial OPMS) during the trimethylsilylati on. Thus a synthetic route for obtaining large stereoregular siloxane macrocycles has been developed. (C) 1998 Elsevier Science S.A. All rig hts reserved.