The atropisomeric compound 2,2'-di(pyridin-2-yl)-1,1'-binaphthalene (1) has been chlorinated, via its bis-N-oxide 2, at the 4 and 6 pyridine ring positions so as to generate the three isomeric species: 2,2'-bis(6-chloropyridin-2-yl)- (3a), 2-(4-chloropyridin-2-yl)-2'-(6-chloropyridin-2-yl)- (3b) and 2,2'-bis(4-chloropyridin-2-yl)-1,1'-binaphthalene (3c). The dichlorinated compounds underwent Ni-catalysed Kumada cross-coupling with MeMgI to give the methylated pyridine isomers: 2,2'-bis(6-methylpyridin-2-yl)- (4a), 2-(4-methylpyridin-2-yl)-2'-(6-methylpyridin-2-yl)- (4b) and 2,2'-bis(4-methylpyridin-2-yl)-1,1'-binaphthalene (4c). The enantiomerically pure forms of the six novel ligands (3a-3c and 4a-4c), prepared from enantiomerically pure 2,2'-di(pyridin-2-yl)-1,1'-binaphthalene (1), were tested in asymmetric catalysis, but proved to be no better and in most cases poorer than parent 1. The coordination of the ligands to Zn and Pd fragments has been explored and compared with the parent compound 1 so as to rationalise the negative effect of pyridine substitution on asymmetric induction in the zinc-catalysed allylation of benzaldehyde.
异构体化合物 2,2'-二(吡啶-2-基)-1,1'-联萘 (1) 通过其双-N-氧化物 2 在吡啶环的 4 和 6 位置进行氯化,从而生成三种异构体:2,2'-双(6-氯吡啶-2-基)-(3a)、2-(4-氯吡啶-2-基)-2'-(6-氯吡啶-2-基)-(3b)和 2,2'-双(4-氯吡啶-2-基)-1,1'-联萘(3c)。这些二氯化合物在 Ni 催化下与 MeMgI 发生 Kumada 交叉偶联反应,生成甲基化吡啶异构体:2,2'-双(6-甲基吡啶-2-基)- (4a)、2-(4-甲基吡啶-2-基)-2'-(6-甲基吡啶-2-基)- (4b) 和 2,2'-双(4-甲基吡啶-2-基)-1,1'-联萘 (4c)。六种新型配体(3a-3c 和 4a-4c)的对映体纯度由对映体纯度为 2,2'-二(吡啶-2-基)-1,1'-联萘(1)制备而成,它们在不对称催化中进行了测试,但结果证明它们的催化效果并不比母体 1 更好,在大多数情况下还不如母体 1。对配体与 Zn 和 Pd 片段的配位进行了探讨,并与母体化合物 1 进行了比较,从而合理解释了吡啶取代对锌催化苯甲醛烯丙基化不对称诱导的负面影响。