Synthesis method for substituting sesquialter siloxane by non-functional alkyl

The disclosed high-yield synthesis method for cage octa-silsesquioxanes substituted by non-functional alkyl comprises: with continual stirring at 50-80Deg, dripping the alkyltrialkoxy silane of 1mol into the mixed liquid with 5-10mol deionized water, 50-100ml solvent with ketone and cyanogen, 0.1-0.3ml trialkylamine as structural inhibitor and 0.5-5ml catalyst with strong HCl and organic acid; with constant temperature of 50-80Deg, refluxing and stirring for 18h, and filtering to obtain the coarse product; cleaning by deionized water with mass as 10-20 times to the coarse product then by the acetone; finally, vacuum drying. This invention can speed up hydrolysis and the structural form, and decreases side reaction.