Recent progress in asymmetric synthesis has been made by the developments of both organic asymmetric catalysts and stoichiometric organic chiral auxiliaries. [1] The origin of significant enantiomeric enrichments in organic compounds such as l-amino acids on the earth has been an intriguing puzzle. [2] One of the proposed mechanisms for the enantiomeric enrichments of organic compounds is through asymmetric synthesis and/or subsequent asymmetric adsorption [3] on the surface of inorganic enantiomorphic crystals. We recently reported an enantioselective synthesis of an organic compound promoted by chiral quartz, [4] which is an enantiomorphic inorganic molecule with covalent bonds between the silicon and oxygen atoms.On the other hand, sodium chlorate (NaClO 3 ) is an enantiomorphic inorganic ionic crystal. [5] Kondepudi et al. reported that almost all of the NaClO 3 crystals precipitated from a stirred particular solution have the same chirality. [6,7] However, the relevance of the chirality of NaClO 3 to that of an organic compound was not established. An earlier report [8] on the enantioselective adsorption of racemic compounds by NaClO 3 was disproved by the later examination of Gillard and da Luz de Jesus. [9] Thus, the question has remained as to whether significantly enantiomerically enriched organic compound can be formed using chiral NaClO 3 , an inorganic ionic crystal.Herein we report an unprecedented highly enantioselective synthesis of an organic compound which is induced by d-or l-NaClO 3 crystals. The enantioselective addition of diisopropylzinc (iPr 2 Zn) to 2-(tert-butylethynyl)pyrimidine-5-carbaldehyde (1) in the presence of d-or l-NaClO 3 powder gave pyrimidylalkanol 2 with high ee values (96 ± 98 % ee) in high yields (90 ± 99 %; Scheme 1, Table 1).The (S)-pyrimidylalkanol (S)-2 was obtained with 98 % ee in 93 % yield when iPr 2 Zn was added to the mixture of d-NaClO 3 and aldehyde 1 (Entry 1). The reaction is reproducible (Entries 2 and 3). On the other hand, reactions between aldehyde 1 and iPr 2 Zn in the presence of l-NaClO 3 , instead of d-NaClO 3 , always gave (R)-2 with 98 % ee in yields of 91 ± 98 % (Entries 4 ± 6). When the reactions were run sequentially in the presence of d-, l-, d-, and l-NaClO 3 , using exactly the same reaction equipments
Dedicated to Professor Dieter Seebach on the occasion of his 65th birthday 1,3-Disubstituted chiral allenes without any heteroatoms act as chiral initiators in the addition of (i-Pr) 2 Zn to pyrimidine-5-carbaldehyde to afford, in combination with the subsequent asymmetric autocatalysis, chiral pyrimidin-5-yl alkanols with up to 98% ee. The absolute configuration of the pyrimidin-5-yl alkanol formed depend on that of the chiral allene.
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