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[摘要]：A 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 second Diels-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. |
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