Matsumoto Arimasa, Yonemitsu Kento, Ozaki Hanae, Míšek Jiří, Starý Ivo, Stará Irena G, Soai Kenso
Department of Applied Chemistry, Tokyo University of Science, Kagurazaka, Shinjuku-ku, Tokyo, 162-8601 Japan.
Institute of Organic Chemistry and Biochemistry, Czech Academy of Sciences, Flemingovo nám. 2, 166 10 Prague 6, Czech Republic.
Org Biomol Chem. 2017 Feb 7;15(6):1321-1324. doi: 10.1039/c6ob02745h.
Reversal of the sense of enantioselectivity was observed between 1-aza[6]helicene 2 and 2-aza[6]helicene 3 employed as chiral inducers of asymmetric autocatalysis of pyrimidyl alkanol. In the presence of (P)-(+)-1-aza[6]helicene 2, the reaction of pyrimidine-5-carbaldehyde 1 with diisopropylzinc afforded, in conjunction with asymmetric autocatalysis, (S)-pyrimidyl alkanol 4 with high ee. Surprisingly, the reaction in the presence of (P)-(+)-2-aza[6]helicene 3 gave the opposite enantiomer of (R)-alkanol 4 with high ee. In the same manner, (M)-(-)-2 and (M)-(-)-3 afforded (R)- and (S)-alkanol 4, respectively. The sense of enantioselectivity is controlled not only by the helicity of the azahelicene derivatives but also by the position of the nitrogen atom.
在用作嘧啶基烷醇不对称自催化手性诱导剂的1-氮杂[6]螺烯2和2-氮杂[6]螺烯3之间观察到对映选择性方向的反转。在(P)-(+)-1-氮杂[6]螺烯2存在下，嘧啶-5-甲醛1与二异丙基锌的反应，伴随着不对称自催化，得到了高对映体过量的(S)-嘧啶基烷醇4。令人惊讶的是，在(P)-(+)-2-氮杂[6]螺烯3存在下的反应得到了高对映体过量的(R)-烷醇4的对映体。同样地，(M)-(-)-2和(M)-(-)-3分别得到了(R)-和(S)-烷醇4。对映选择性的方向不仅由氮杂螺烯衍生物的螺旋性控制，还由氮原子的位置控制。
