nmr 500 mhz cdcl 3 u03b4 u2212 0 8 u02dc 0 4 s si me u2212 7 1 u02dc 7 8 s si ph ppm 29 si nmr 99 3 mhz cdcl 3 u03b4 54 0 s me t 2 u2212 79 4 s ph t 3 ppm preparation of compound represented by formula 3 r 1 phenyl r 3 methyl a reflux condenser 100 ml dropping funnel and dean stark tube were placed in a 1000 ml four necked round bottom flask and dried with flame under a nitrogen atmosphere 50 g of cyclotetraphenylsilsesquioxane obtained in example 1 was put into the flask and dissolved in 380 ml of toluene 0 7 ml of hcl as a reaction catalyst was added thereto and reacted at room temperature for 38 hours while slowly dropping 54 g of trimethoxymethylsilane using a dropping funnel thereafter the reactant solution was further reacted at a reflux temperature of toluene for 72 hours after the completion of the reaction the reactant was dropped into an excess of methanol agitated for 30 minutes and then filtered the produced precipitate thereby obtaining white powder of a desired product yield 84 the product was thermally hardened at 150 u00b0 c under 4.