Sequential homo-coupling Diels–Alder/retro Diels–Alder reaction of 5,5′-bi-1,2,4-triazine-containing thiamacrocycles as a new route to thiacrown ethers incorporating a 2,2′-bipyridine subunit

A new route to thiacrown ethers 5a–d and 6a–d incorporating a 2,2′-bipyridine subunit is elaborated using, (1) homo-coupling of 1,2,4-triazine sulfides 3a–d tethered to poly(ethylene glycol) chains with potassium cyanide and (2) Diels–Alder/retro Diels–Alder reaction with norbornadiene or 1-pyrrolidino-1-cyclopentene as the key steps.