Abstract Methods are explored to enhance the efficiency and versatility of the synthesis of the 1-substituted 4-(propananilido) perhydroazepine analgesics. The modified synthesis begins with ring expansion of 1-carbethoxy-4-piperidinone 3 with ethyl diazoacetate and boron trifluoride to yield 1, 5-biscarbethoxyperhydroazepin-4-one 4. Selective hydrolysis of 4 followed by decarboxylation provides 1-carbethoxyperhydroazepin-4-one 6. Reductive ...