2,2′,6,6′-四甲氧基-4,4′-二(二苯基氧膦)-3,3′-联吡啶的合成

Synthesis of 2,2′,6,6′-Tetramethoxy-4,4′-diphenylphosphinoyl-3,3′-bipyridyl

以2,6 二氯吡啶为起始原料,首先合成了2,6 二甲氧基吡啶,而后经过-20～-40℃下吡啶环的溴化反应,合成了中间产物2,6 二甲氧基 3 溴吡啶,收率为74 8%;进而,在-78℃条件下利用Ph2PCl作为亲电试剂进行亲电取代反应制备了中间产物2,6 二甲氧基 3 溴 4 二苯基膦吡啶,收率为77 4%;最后,利用0℃下三价膦的氧化反应合成了2,6 二甲氧基 3 溴 4 二苯基氧膦吡啶及150℃下吡啶环的偶合反应,合成出了目标产物2,2′,6,6′ 四甲氧基 4,4′ 二(二苯基氧膦) 3,3′ 联吡啶,收率分别为95 3%和62 5%,整个合成过程的总收率为27 8%。在合成过程中采用氢谱、碳谱等核磁共振方法鉴定了一些重要中间产物和目标产物的分子结构。

2,6-Dimethoxypyridine(Ⅰ) was prepared from 2,6-dichlorpyridine firstly.Then by slow addition of bromine to Ⅰ at -20 ～ -40 ℃,3-bromo-2,6-dimethoxypyridine(Ⅱ) was produced in 74.8% yield.Electrophilic substitution of Ⅱ with Ph_2PCl at -78 ℃ gave 3-bromo-2,6-dimethoxy-4-diphenylphosphinopyridine(Ⅲ) in 77.4% yield.Finally,oxidation of trivalent phosphorous in Ⅲ at 0 ℃ and coupling reaction of the pyridine ring at 150 ℃ were used to synthesize the target product 2,2′6,6′-tetramethoxy-4,4′-diphenylphosphinoyl-3,3′-bipyridyl.The yields were 95.3% and 62.5% respectively.Structural analyses of the important intermediates and the target product were done by ~1HNMR and ^(13)CNMR.