hydrosilane [(EtO)3SiH] was revealed in the one-carbon migration and isomerization of 4,4-biaryl-substituted 1-butenes, in which the (EtO)3SiH plays a key role in the palladium-catalyzed one-carbon migration and subsequent isomerization of terminal alkenes. This catalytic protocol is applied in the synthesis of a key building block of cassumunin C in high yield and promising selectivity.