Highly Enantioselective Conjugate Addition of Nitroalkanes to Alkylidenemalonates Using Efficient Phase-Transfer Catalysis of <i>N</i>-Spiro Chiral Ammonium Bromides
作者:Takashi Ooi、Shingo Fujioka、Keiji Maruoka
DOI:10.1021/ja047047v
日期:2004.9.1
to the desired conjugate addition product 4 (R1 = Et, R2 = Ph) quantitatively (anti/syn = 86:14) with 97% ee (anti isomer). The applicability of this procedure has been demonstrated with other representative alkylidenemalonates and nitroalkanes. Since 4 can be readily transformed into the corresponding gamma-amino acid hydrochloride 5 without loss of diastereo- and enantioselectivity, the present method
硝基烷烃与亚烷基丙二酸酯的高度对映选择性共轭加成首次通过利用 N-螺 C2-对称手性溴化季铵 1 的有效相转移催化实现。例如,简单混合硝基丙烷 (2, R1 = Et )、二异丙基苄基二烯丙二酸酯 (3, R2 = Ph)、Cs2CO3 (1 当量) 和 (S,S)-1 (1 mol%) 在甲苯中在 0 摄氏度下 2.5 小时产生所需的共轭加成产物 4( R1 = Et,R2 = Ph) 定量(反/syn = 86:14)与 97% ee(反异构体)。该程序的适用性已用其他代表性的亚烷基丙二酸酯和硝基烷烃证明。由于 4 可以很容易地转化为相应的 γ-氨基酸盐酸盐 5,而不会损失非对映选择性和对映选择性,