Abstract:Ligand redistribution of appropriate alkoxy-or chlorosiloxane substrates at elevated temperatures afforded examples of the title heterocyclic system bearing easily solvolyzable substituents at one or both silicon sites. Also described are novel spirocyclic derivatives of the bidentate alkoxy ligand, -OCMe&H2CH&Mez0-.
“…This sequence is modeled after one used by Frye to prepare 2-chloro-2,5,5-trimethyl-1-oxa-2,5-disilacyclopentane. 12,13 AROP of I, II, or III in THF, catalyzed by dilithiodiphenylsilanediolate, 14 yields IV, V, or VI, respectively ( Figure 2). The high reactivity of I, II, and III is the result of angle strain.…”
Section: Resultsmentioning
confidence: 99%
“…Alkaline pyrolysis of these tetra-adducts results in rearrangement and redistribution to yield I , II , and III . This sequence is modeled after one used by Frye to prepare 2-chloro-2,5,5-trimethyl-1-oxa-2,5-disilacyclopentane. , 1 Synthesis of II .…”
2,5,5-Trimethyl-2-trimethylsiloxy-1-oxa-2,5-disilacyclopentane (I), cis-and trans-2,5-dimethyl-2,5-bis(trimethylsiloxy)-1-oxa-2,5-disilacyclopentane (II), and 2-methyl-2,5,5-tris(trimethylsiloxy)-1-oxa-2,5-disilacyclopentane (III) have been prepared from 1,3,5,7-tetramethylcyclotetrasiloxane (D4 H ) and vinylpentamethyldisiloxane, vinylmethylbis(trimethylsiloxy)silane, and vinyltris(trimethylsiloxy)-silane, respectively, by a two-step synthetic process. I, II, and III undergo anionic ring-opening polymerization (AROP) to yield poly[2,2,5-trimethyl-5-trimethylsiloxy-1-oxa-2,5-disila-1,5-pentanylene] (IV), poly[2,5-dimethyl-2,5-bis(trimethylsiloxy)-1-oxa-2,5-disila-1,5-pentanylene] (V), and poly[2-methyl-2,5,5-tris(trimethylsiloxy)-1-oxa-2,5-disila-1,5-pentanylene] (VI), respectively. I-VI have been characterized by 1 H, 13 C, and 29 Si NMR and IR spectroscopy. Polymer microstructures have been determined by 29 Si NMR. Molecular weights of I-III have been determined by GC/MS and by high-resolution mass spectrometry. Molecular weight distributions of IV-VI have been determined by GPC. Mn's have been independently determined by 1 H NMR analysis. The glass transition temperatures (Tg's) and thermal stability of these polymers have been determined by DSC and TGA, respectively. Chain transfer apparently limits the molecular weight of VI.
IntroductionThere is interest in the synthesis of cyclosilaalkylenesiloxanes and in the cationic ring-opening polymerization of these to yield poly(silaalkylenesiloxane)s. 1 AROP of 2,2,5,5-tetramethyl-1-oxa-2,5-disilacyclopentane has been reported, 2-5 and the kinetics of this process has been studied. 6 2,2,5,5-Tetramethyl-1-oxa-2,5-disilacyclopentane has been used to prepare welldefined poly(R-methylstyrene)-b-poly(dimethylsiloxane) block copolymers by living anionic polymerization. 7 Polymerization of 2-(3′,3′,3′-trifluoropropyl)-2,5,5-trimethyl-1-oxa-2,5-disilacyclopentane and related systems gives elastomeric materials with excellent chemical resistance, electrical properties, and strength. 8,9 Bis(1-oxa-2,5-disilacyclopentane)s undergo AROP to yield nonshrinking polycarbosilane/siloxanes. 10,11 Despite this interest in 1-oxa-2,5-disilacyclopentanes and in AROP, no examples of polymerization of trimethylsiloxy (TMSO)-substituted 1-oxa-2,5-disilacyclopentanes have been reported.
“…This sequence is modeled after one used by Frye to prepare 2-chloro-2,5,5-trimethyl-1-oxa-2,5-disilacyclopentane. 12,13 AROP of I, II, or III in THF, catalyzed by dilithiodiphenylsilanediolate, 14 yields IV, V, or VI, respectively ( Figure 2). The high reactivity of I, II, and III is the result of angle strain.…”
Section: Resultsmentioning
confidence: 99%
“…Alkaline pyrolysis of these tetra-adducts results in rearrangement and redistribution to yield I , II , and III . This sequence is modeled after one used by Frye to prepare 2-chloro-2,5,5-trimethyl-1-oxa-2,5-disilacyclopentane. , 1 Synthesis of II .…”
2,5,5-Trimethyl-2-trimethylsiloxy-1-oxa-2,5-disilacyclopentane (I), cis-and trans-2,5-dimethyl-2,5-bis(trimethylsiloxy)-1-oxa-2,5-disilacyclopentane (II), and 2-methyl-2,5,5-tris(trimethylsiloxy)-1-oxa-2,5-disilacyclopentane (III) have been prepared from 1,3,5,7-tetramethylcyclotetrasiloxane (D4 H ) and vinylpentamethyldisiloxane, vinylmethylbis(trimethylsiloxy)silane, and vinyltris(trimethylsiloxy)-silane, respectively, by a two-step synthetic process. I, II, and III undergo anionic ring-opening polymerization (AROP) to yield poly[2,2,5-trimethyl-5-trimethylsiloxy-1-oxa-2,5-disila-1,5-pentanylene] (IV), poly[2,5-dimethyl-2,5-bis(trimethylsiloxy)-1-oxa-2,5-disila-1,5-pentanylene] (V), and poly[2-methyl-2,5,5-tris(trimethylsiloxy)-1-oxa-2,5-disila-1,5-pentanylene] (VI), respectively. I-VI have been characterized by 1 H, 13 C, and 29 Si NMR and IR spectroscopy. Polymer microstructures have been determined by 29 Si NMR. Molecular weights of I-III have been determined by GC/MS and by high-resolution mass spectrometry. Molecular weight distributions of IV-VI have been determined by GPC. Mn's have been independently determined by 1 H NMR analysis. The glass transition temperatures (Tg's) and thermal stability of these polymers have been determined by DSC and TGA, respectively. Chain transfer apparently limits the molecular weight of VI.
IntroductionThere is interest in the synthesis of cyclosilaalkylenesiloxanes and in the cationic ring-opening polymerization of these to yield poly(silaalkylenesiloxane)s. 1 AROP of 2,2,5,5-tetramethyl-1-oxa-2,5-disilacyclopentane has been reported, 2-5 and the kinetics of this process has been studied. 6 2,2,5,5-Tetramethyl-1-oxa-2,5-disilacyclopentane has been used to prepare welldefined poly(R-methylstyrene)-b-poly(dimethylsiloxane) block copolymers by living anionic polymerization. 7 Polymerization of 2-(3′,3′,3′-trifluoropropyl)-2,5,5-trimethyl-1-oxa-2,5-disilacyclopentane and related systems gives elastomeric materials with excellent chemical resistance, electrical properties, and strength. 8,9 Bis(1-oxa-2,5-disilacyclopentane)s undergo AROP to yield nonshrinking polycarbosilane/siloxanes. 10,11 Despite this interest in 1-oxa-2,5-disilacyclopentanes and in AROP, no examples of polymerization of trimethylsiloxy (TMSO)-substituted 1-oxa-2,5-disilacyclopentanes have been reported.
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