Synthesis and characterization of large stereoregular organosiloxane cycles

Abstract

The large stereoregular phenyltrimethylsiloxysiloxane macrocycles of general formula [PhSi(OSiMe3)O]n (n=6 and 12) have been selectively obtained with high yields by trimethylsilylation of cage-like oligophenylmetallasiloxanes (OPMS) which we described earlier. The compounds 3 (n=6) and 4 (n=12) have been characterized by NMR-spectroscopy method and by single crystal X-ray analysis. This investigation showed unambiguously that the siloxane macrocycles keep their size and configuration (the same as in the initial OPMS) during the trimethylsilylation. Thus a synthetic route for obtaining large stereoregular siloxane macrocycles has been developed.

Synthesis of macrocyclic tris-cis-tris-trans- dodeca[(phenyl)(hydroxy)]cyclododecasiloxane in carbonic acid solution

“…12 increased with the increase in the reaction time in the carbonic acid solutions. When the reaction was performed during 1-2 h (curves 2, 3), the purity of the product obtained was yet poor, but for longer reaction times (curves 4, 5) the fraction of crystalline impurities drastically decreased.…”

“…For comparison, the initial polyhedral phenylcoppersodiumsiloxane and the reference sample tris-cis-tris-trans-dodeca[(phenyl) (hydroxy)]cyclododecasiloxane described previously (18) were also analyzed. In the IR spectra ( Figure 1 (4), (5) and (6) reaction products after 1, 2, 3, 5 and 6 h, respectively, of the reaction in carbonic acid solutions and subsequent washing with water, (7) the product obtained after 6 h of the reaction in carbonic acid, subsequently washed with water and treated with a diluted acetic acid in order to remove copper basic carbonate; and (8) reference tris-cis-tris-trans-[PhSi(O)OH] 12 sample, obtained accordingly to the previously described method (10).…”

“…Only when the reaction was carried out for 6 h the completed pure product was obtained after washing and drying. The product contained only tris-cis-tris-trans-[PhSi(O)OH] 12 and copper basic carbonate (Figure 1, curve 4 and Figure 2, curve 6). The copper basic carbonate, which is not soluble in water, precipitated together with the cyclic siloxane.…”

“…Studies on the synthesis of polyhedral organometallasiloxanes and their subsequent controlled decomposition have led to the development of a relatively easy and reliable way to obtain stereoregular functional organocyclosiloxane compounds (12)(13)(14)(15)(16)(17)(18). Metal ion-directed selfassembly pathways to form selectively polyhedral organometallasiloxane molecules with well-defined regular configurations were elaborated upon by means of hydrolytic condensation reaction of different trifunctional organoalkoxysilanes in the presence of ions of alkaline and transition metals.…”

“…According to this strategy, the metal ions serve both as templating units and as structural elements. The subsequent reaction of the polyhedral organometallasiloxanes either with triorganylchlorosilanes or with dilute hydrochloric acid in organic solvents allows the metal ions to be removed effectively as metal chlorides and for cyclosiloxanes to be obtained (12)(13)(14)18).…”