Abstract The reaction of cycloalkenes (cyclopentene, cyclohexene, cycloheptene, cyclooctene, 1-methylcyclohexene, and norbornene) with Et 2 MeSiH and carbon monoxide in the presence of Co 2 (CO) 8 gave the corresponding diethylmethylsiloxymethylenecycloalkenes. In such reactions of cyclohexene, the following hydrosilanes gave the corresponding siloxymethylenecyclohexanes: Me 3 SiH, EtMe 2 ...