Chiral 2-[N-aryl-N-(ferrocenylmethyl)amino}methyl]-4-(1-methylethyl)-4,5-dihydroxazoles with various substituents at the aryl ring were prepared by alkylation of N-(ferrocenylmethyl)anilines, FcCH2NHC6H4R (Fc = ferrocenyl), with (S)-2-(chloromethyl)-4-(1-methylethyl)-4,5-dihydrooxazole. The oxazoles, substituted anilines, and the precursors of the latter, the respective Schiff bases FcCH=NC6H4R, were characterized by standard methods and further studied by mass spectrometry. The oxazoles were further tested as chiral auxiliaries in the addition of diethylzinc to benzaldehyde but showed only negligible asymmetric induction (ee ca 10%), most likely due to steric hindrance of the nitrogen donor centres. This steric restriction seems to be lowered upon replacement of the substituted phenyl group with a benzyl substituent; compounds FcCH2NHCH2Ph and (R)-FcCH2NHCH(Me)Ph are easily alkylated yielding [FcCH2NMe2(CH2Ph)]I (9) and 2-[N-(1-phenylethyl)-N-(ferrocenylmethyl)amino}methyl]-4-(1-methylethyl)-4,5-dihydroxazole (10), respectively. Solid-state structures of FcCH2NHC6H4R (R = 2-Me and 4-Cl), 9, and 10 have been determined by single-crystal X-ray diffraction.
手性化合物2-[N-芳基-N-(
二茂铁甲基)
氨基}
甲基]-4-(1-甲乙基)-4,5-二羟基
噁唑烷在芳基环上带有各种取代基,通过将N-(
二茂铁甲基)
苯胺FcCH2NHC6H4R (Fc =
二茂铁基)烷基化制备,与(S)-2-(
氯甲基)-4-(1-甲乙基)-4,5-二羟基
噁唑烷反应。这些
噁唑烷、取代
苯胺和后者的前体,相应的席夫碱FcCH=NC6H4R,通过标准方法进行了表征,并通过质谱进一步研究。这些
噁唑烷在
苯甲醛与
二乙基锌加成反应中作为手性辅助试剂进行了进一步测试,但仅表现出微弱的不对称诱导(ee约10%),这很可能是由于
氮供体中的立体阻碍。这种立体限制似乎在用
苄基取代取代
苯基团时降低了;化合物FcCH2NHCH2Ph和(R)-FcCH2NHCH(Me)Ph易于烷基化,生成[FcCH2NMe2(CH2Ph)]I(9)和2-[N-(1-
苯乙基)-N-(
二茂铁甲基)
氨基}
甲基]-4-(1-甲乙基)-4,5-二羟基
噁唑烷(10),分别。单晶X射线衍射确定了FcCH2NHC6H4R(R =
2-甲基和4-
氯)、9和10的固态结构。