Synthesis of 1,2,4-trisubstituted-1,2,5,6-tetrahydropyridines

A novel method for the synthesis of 1,2,4-trisubstituted- or 1,2,3,4-tetrasubstituted-1,2,5,6-tetrahydropyridine is presented. The process was carried out by the bromomethoxylation of 4-substituted-1,2,5,6-tetrahydropyridines 1 with N-bromosuccinimide (NBS) in methanol, dehydrobromination with 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU), and boron trifluoride etherate (BF3-OEt2)-catalyzed cross coupling of the corresponding enamine with trimethylsilyl-based nucleophiles. Homokainoid analogs were also synthesized via the protocol.