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 newroute 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–Alderreaction with norbornadiene or 1-pyrrolidino-1-cyclopentene as the key steps.
of 1:1 thiacrown ether macrocycles 5a―c containing a fused cyclopenteno[c]2,2'-bipyridine subunit has been accomplished through first homo-coupling of 1,2,4-triazine bisulfides 3a―c tethered to poly(ethylene glycol) chains with potassium cyanide and second Diels―Alder/retro-Diels―Alder reaction of such obtained thiamacrocycles 4a―c with 1-pyrrolidino-1-cyclopentene. Macrocycles 5a―c were oxidized to
The crystal structure determinations and theoretical calculations at DFT/B3LYP/6-311++G(d,p) level of 5,5'-bi-1,2,4-triazine thiacrown ethers containing 16-, 19- and 22-membered macrocyclic ring were used to analyze their conformational preferences in the crysalline state and gaseous phase.
A facile approach to 2,2′-bipyridine based thiacrown ethers and their sulfoxides by DA-rDA reaction of 5,5′-bi-1,2,4-triazine thiamacrocycles. The conformation studies
Diels-Alder/retro Diels-Alder (DA-rDA) reactions of 5,5′-bi-1,2,4-triazinethiamacrocycles 4a–c afforded medium-size 2,2′-bipyridinebasedthiacrownethers 5a–c in good yield. The latter were oxidized to non-racemic monosulfoxides 7a–c using Davis oxaziridine and tested as chiral auxilaries in the asymmetric addition of diethyl zinc to benzaldehyde. The theoretical calculations at DFT /B3LYP/6-311G**