Synthesis of 1-Formyl-1,2-dihydroquinoline Derivatives by a Lewis Acid-Catalyzed Cyclization of o-(1-Hydroxy-2-alkenyl)phenyl Isocyanides

An efficient route to 1-formyl-1,2-dihydroquinolines 6 is described based on the BF3-catalyzed cyclization of o-(1-hydroxy-2-alkenyl)phenyl isocyanides 4, which can be prepared feasibly by the reaction of N-(o-acylphenyl)formamides 1 with alkenylmagnesium bromides 2 followed by treatment of the resulting hydroxy formamides 3 with phosphorous oxychloride.