Ti(O^iPr)_4/席夫碱配合物催化不对称2-甲氧基丙烯与对硝基苯甲醛的Hetero-ene反应

Asymmetric Hetero-ene Reaction of 2-Methoxypropene and 4-Nitrobenzaldehyde with Ti(O^iPr)_4/Schiff-base Catalysts

由新型联苯手性骨架(R)-(+)-2-氨基-2′-羟基-6,6′-二甲基-1,1′-联苯1a,(R)-(+)-2-氨基-2′-羟基-4,4′,6,6′-四甲基-1,1′-联苯1b与不同取代基的水杨醛反应合成了9个新型席夫碱配体2a～2i,化合物的结构用核磁共振以及高分辨质谱进行表征.其中(R)-(+)-2-氨基-2′-羟基-6,6′-二甲基-1,1′-联苯和3,5-二溴水杨醛衍生得到的席夫碱配体2g与Ti(OiPr)4生成的配合物催化不对称2-甲氧基丙烯与对硝基苯甲醛的Hetero-ene反应,在-10℃反应3h时获得了最高为79%ee的反应产物.

Nine new chiral Schiff-base ligands (2a-2i, 3) were prepared from (R)-(+)-2-amino-2′-hydroxy-6, 6′-dimethyl-1, 1′-biphenyl (1a ), (R)-(+)-2-amino-2′-hydroxy-4, 4′, 6, 6′-tetramethyl-1, 1′-biphenyl (1b) and substituted salicylaldehydes. The structures of these Schiff-base ligands were characterized with ~1H NMR, ^(13)C NMR and high resolution mass spectroscopy (HR-MS). The asymmetric hetero-ene reaction between 2-methoxypropene and 4-nitrobenzaldehyde catalyzed by Ti(O^iPr)_4/2g complex was carried out at -10 ℃ for 3 h, up to 79 % ee of product was obtained.