The reaction of cycloalkenes(cyclopentene, cyclohexene, cycloheptene, cyclooctene, 1-methylcyclohexene, and norbornene) with Et2MeSiH and carbonmonoxide in the presence of Co2(CO)8 gave the corresponding diethylmethylsiloxymethylenecycloalkenes. In such reactions of cyclohexene, the following hydrosilanes gave the corresponding siloxymethylenecyclohexanes: Me3SiH, EtMe2SiH, Et2MeSiH, Et3SiH, PhMe2SiH