Asymmetric Autocatalysis Induced by Chiral Crystals of Achiral Tetraphenylethylenes |
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Authors: | Tsuneomi Kawasaki Mai Nakaoda Nobuhiro Kaito Taisuke Sasagawa Kenso Soai |
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Institution: | (1) Department of Applied Chemistry, Tokyo University of Science, Kagurazaka, Shinjuku-ku Tokyo, 162-8601, Japan;(2) Research Institute of Science and Technology, Tokyo University of Science, Kagurazaka, Shinjuku-ku Tokyo, 162-8601, Japan; |
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Abstract: | The achiral hydrocarbon tetraphenylethylene crystallizes in enantiomorphous forms (chiral space group: P21) to afford right- and left-handed hemihedral crystals, which can be recognized by solid-state circular dichroism spectroscopic
analysis. Chiral organic crystals of tetraphenylethylene mediated enantioselective addition of diisopropylzinc to pyrimidine-5-carbaldehyde
to give, in conjunction with asymmetric autocatalysis with amplification of chirality, almost enantiomerically pure (S)- and (R)-5-pyrimidyl alkanols whose absolute configurations were controlled efficiently by the crystalline chirality of the tetraphenylethylene
substrate. Tetrakis(p-chlorophenyl)ethylene and tetrakis(p-bromophenyl)ethylene also show chirality in the crystalline state, which can also act as a chiral substrate and induce enantioselectivity
of diisopropylzinc addition to pyrimidine-5-carbaldehyde in asymmetric autocatalysis to give enantiomerically enriched 5-pyrimidyl
alkanols with the absolute configuration correlated with that of the chiral crystals. Highly enantioselective synthesis has
been achieved using chiral crystals composed of achiral hydrocarbons, tetraphenylethylenes, as chiral inducers. This chemical
system enables significant amplification of the amount of chirality using spontaneously formed chiral crystals of achiral
organic compounds as the seed for the chirality of asymmetric autocatalysis. |
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