Synthesis of 5, 6, 7, 8-Tetrahydroquinolines by Thermolysis of Oxime O-Allyl Ethers in the Presence of Boron Trifluoride Etherate

Thermolysis of cyclohexanone oxime O-crotyl and O-cinnamyl ether in the presence of BF3-etherate regioselectively gave 4-methyl- and 4-phenyl-5, 6, 7, 8-tetrahydroquinoline, while the addition of organic bases such as triethylamine and pyridine inhibited the rearrangement. These findings suggested that the addition of the acid made [1, 2] shift the predominant one of the two possible transformations, [1, 2] and [2, 3] shift, of the O-allyl ethers.