The Cyclization of Hex-5-Enylcarbamates and Related Compounds With Benzeneselenenyl Chloride and Some Reactions of the 2-Substituted Piperidine Products

Abstract

The reaction of hex-5-enylcarbamates with benzeneselenenyl chloride gives adducts which cyclize , in the presence of silica or stannic chloride, to 2-phenylselenomethylpiperidine-1-carboxylates. The corresponding selenoxides eliminate to form 2-methylenepiperidine derivatives which are unstable, both thermally and on silica. The selenoxides also undergo a Pummerer-type reaction to form 2-acetoxy( phenylseleno ) methylpiperidine systems which can be oxidatively converted into a piperidine 2-aldehyde. The selenoxides react with carbon tetrachloride in base to form a 2,2,2-trichloroethyl substituent . Both the selenoxides and the phenylseleno groups of the cyclized products can be displaced by nucleophiles. Ethyl hept-6-enylcarbamate did not give a cyclic product with benzeneselenenyl chloride and silica, and gave a poor yield of a hexahydroazepine with stannic chloride. Hex-5-enamide cyclized to give a lactone, rather than a lactam , product. Hex-5-enenitrile gave Ritter reaction products with benzeneselenenyl chloride in acetonitrile , and a dimer in non- nucleophilic solvents.