Abstract The reaction of a silyl enol ether bearing a nitrogen atom with a hemiacetal vinylog in the presence of a catalytic amount of boron trifluoride etherate led to the corresponding ketoaldehyde. The cyclisation of the ketoaldehyde into azaspiroenone and nitrogen deprotection was performed in basic medium. The N-benzylation of this enone gave the known key intermediate of total synthesis of (±)-perhydrohistrionicotoxin.
