A Convenient Approach to 16‐, 19‐, and 22‐Membered 2,2′‐Bipyridine Thiacrown Ethers and Their Conformation Preferences

Abstract

AbstractA convenient, three‐step synthesis of 1:1 thiacrown ether macrocycles 5a–c containing a fused cyclopenteno[c]2,2′‐bipyridine subunit has been accomplished through first homocoupling of 1,2,4‐triazine bisulfides 3a–c tethered to poly(ethylene glycol) chains with potassium cyanide and secondDiels–Alder/retro‐Diels–Alder reaction of such obtained thiamacrocycles 4a–c with 1‐pyrrolidino‐1‐cyclopentene. Macrocycles 5a–c were oxidized to nonracemic monosulfoxides 6a–c by using Davis' oxaziridine and tested in the asymmetric addition of the diethylzinc to benzaldehyde. The crystal structure determinations of 5a–c and 6b and theoretical calculations at the DFT/B3LYP/6‐311G** level were used to establish their cis or trans conformations in the solid state and the gas phase.