The structures of the quaternary salts (IIIa, b, c) produced from the reaction of 1-alkyl-2-piperidones (1a, b, c) (alkyl ; a, phenethyl ; b, benzyl ; c, methyl) with phosphoryl chloride were investigated and found to be 1, 5-di-alkyl-2, 3, 4, 4a, 5, 6, 7, 8 (or 2, 3, 4, 5, 6, 7, 8, 8a)-octahydrocyclobuta-[1, 2-b : 3, 4-b'] dipyridin-1-ium salts (a, alkyl ; phenethyl ; b, benzyl ; c, methyl).