Synthesis of enones, pyrazolines and pyrrolines with gem-difluoroalkyl side chains

Abstract

Starting from easily accessible gem-difluoropropargylic derivatives, a DBU-mediated isomerisation affords enones in fair yields with a gem-difluoroalkyl chain. These derivatives were used to prepare pyrazolines and pyrrolines with the desired gem-difluoroalkyl side chain by cyclocondensations in good yields and with excellent stereoselectivity. A one-pot process was also successfully developed for these sequential reactions. By carrying out various types of Pd-catalyzed coupling reactions for compounds with a p-bromophenyl substituent a route to focused chemical libraries was demonstrated.

Keywords

• 19F/1H HOESY
• gem-difluoroalkyl derivatives
• organo-fluorine compounds
• palladium catalysis
• pyrazolines
• pyrrolines