Synthesis and ring-opening polymerization of novel bicyclic oxalactams: 2-oxa-5-azabicyclo[2.2.2]octan-6-one

A novel bicyclic oxalactam 2‐oxa‐5‐azabicyclo [2.2.21 octan‐6‐one (2,5‐BOL) was synthesized from sodium 3,4‐dihydro‐2H‐pyran‐2‐carboxylate through a seven‐step reaction sequence. Anionic ring‐opening polymerization of 2,5‐BOL was carried out in bulk at 12OOC or in dimethyl sulfoxide at 40, 60, and 80°C by using potassium pyrrolidonate and the N‐benzoyl derivative of 2,5‐BOL as catalyst and activator, respectively. The polymerization gave a new polyamide containing cis‐ and trans‐2,5‐linked tetrahydropyran rings in the main chain. The cis/trans ratio varied from 70/30 to 95 /5 depending on the reaction conditions. The polyamide having number average molecular weights of 3000–8000 was soluble in a variety of solvents including methanol, ethanol, dimethyl sulfoxide, dimethylformamide, chloroform, and dichloromethane. It began to decompose at 280–32OOC depending on the compositions of the cis‐ and trans‐2,5‐linked structural units. The anionic ring‐opening polymerizability of 2,5‐BOL was found to be much lower than its structural isomer, 8‐oxa‐6‐azabicyclo[ 3.2.11 octan‐7‐one (8,6‐BOL).