Blocked mercaptosilanes are provided in which the blocking group contains and unsaturated heteroatom or carbon chemically bound directly to sulfur via a single bond. This blocking group optionally may be substituted with one or more carboxylate ester or carboxylic acid functional groups. These silanes are used in manufacture of inorganic filled rubbers, with the silanes deblocked by a deblocking agent. Synthesis of the blocked mercaptosilanes is also provided.