Compounds of the formula Ia ##STR1## in which X and R.sup.1 to R.sup.6 are as defined in the claims, are obtainable by reacting monochlorosilanes of the formula II ##STR2## with tetrasubstituted ethylenes of the formula III ##STR3## X as Cl and Br can be replaced by ester groups of inorganic and organic acids. The compounds of the formula I and those with other ester groups are suitable especially as a protective-group reagent for hydroxyl, mercapto, carboxyl, amino and amide groups.
式Ia的化合物##STR1##其中X和R.sup.1至R.sup.6如权利要求所定义,可通过将式II的单
氯硅烷##STR2##与式III的四取代
乙烯##STR3##反应获得。X作为Cl和Br可以被无机和有机酸的酯基所取代。式I的化合物和其他酯基的化合物特别适用作羟基、巯基、羧基、
氨基和酰胺基的保护基试剂。