Diisopropyl(N,N,N′,N′-tetramethylethylenediamine)zinc(II), the first crystal structure of a diisopropylzinc complex

Lennartson, Anders; Hedström, Anna; Håkansson, Mikael

doi:10.1107/s1600536806052068

Cited by 9 publications

(10 citation statements)

References 9 publications

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“…In the racemic tetramer B , ( R )‐ and ( S )‐alkoxides form Zn 2 O 2 square dimers, and macrocycle were also constructed with ( R )‐ and ( S )‐alkoxides. This Zn 2 O 2 square and macrocycle tetramer structure has good accordance with the proposed stable tetramer structure by DFT calculations including steric hindrance of isopropyl group 16c. In the chiral tetramer A , six i Pr 2 Zn moieties coordinate to the nitrogen atoms that do not coordinate to the Zn 2 O 2 square.…”

Section: Methodssupporting

confidence: 82%

“…Zinc alkoxide with oligomeric structures16c was also observed upon changing the crystallization conditions. Mixing 1–2 equivalents of i Pr 2 Zn with either enantiopure or racemic alkanol afforded Crystals C and D , respectively, with different structures (Figure 2).…”

Section: Methodsmentioning

confidence: 98%

“…Irrespective of whether the active catalyst or resting state is a dimer or higher oligomer(s), the formation of an aggregate seems to be a key feature of this reaction. However, no detailed structural study of the asymmetric autocatalyst has been undertaken by X‐ray diffraction analysis 16…”

Section: Methodsmentioning

confidence: 99%

“…In the chiral tetramer A , six i Pr 2 Zn moieties coordinate to the nitrogen atoms that do not coordinate to the Zn 2 O 2 square. These coordinated i Pr 2 Zn are activated by nitrogen coordination, with C‐Zn‐C angles of 156‐164°, and with a CZn bond length of 1.99–2.01 Å 16–18. In the racemic alkoxide crystal B , four i Pr 2 Zn moieties coordinate.…”

Section: Methodsmentioning

confidence: 99%

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Crystal Structure of the Isopropylzinc Alkoxide of Pyrimidyl Alkanol: Mechanistic Insights for Asymmetric Autocatalysis with Amplification of Enantiomeric Excess

et al. 2015

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Asymmetric amplification during self-replication is akey feature that is used to explain the origin of homochirality. Asymmetric autocatalysis of pyrimidyl alkanol in the asymmetric addition of diisopropylzinc to pyrimidine-5-carbaldehyde is aunique example of this phenomenon. Crystallization of zinc alkoxides of this 5-pyrimidyl alkanol and single-crystal X-ray diffraction analysis of the alkoxide crystals reveal the existence of tetramer or higher oligomer structures in this asymmetric autocatalytic system.The origin of biological homochirality,such as that found in l-amino acids,i safundamental question that has attracted the interest of scientists from awide range of research areas. [1] Although there are several possible origins of homochirality, propagation and amplification of chirality generated from the initial breaking of symmetry are also key topics for the evolution of homochirality.A symmetric autocatalysis with amplification of chirality has been suggested as amechanistic model for the evolution of homochirality.I nt his reaction, ac hiral product serves as an asymmetric catalyst to produce more of itself;the process is thus an automultiplication of the chiral compound.We found asymmetric autocatalysis with amplification of the enantiomeric excess (ee)i nareal chemical reaction (Scheme 1).[2-4] When diisopropylzinc (iPr 2 Zn) is added to pyrimidine-5-carbaldehyde 1 in the presence of ac atalytic amount of (S)-pyrimidyl alkanol 2 with alow ee,asymmetric autocatalytic amplification of the ee produces (S)-2 with high ee as the final product. Early autocatalytic work with pyrimidine-5-carbaldehyde [2a] and 2-methylpyrimidine-5-carbaldehyde was succeeded by the use of superior 2-alkynyl analogues [2b] and the amplification efficiencywas dramatically increased to obtain product 2 with more than 99.5 % ee after consecutive asymmetric autocatalytic amplification, even when the initial catalyst has only ca. 510 À5 % ee.T his unique property means that, in addition to chiral molecules, at race imbalance of chirality induced by chiral triggers such as circularly polarized light, [5] crystal chirality, [6] various chiral materials, [7] or isotope chirality [8] can also be amplified to afford enantioenriched alkanol 2 with corresponding absolute configurations.Furthermore,spontaneous absolute asymmetric synthesis can be achieved by using this reaction. [9] Although the theory of asymmetric amplification during self-replication was first proposed in 1953, [10] the above reaction remains the only practical example of ac hemical reaction involving asymmetric autocatalysis that leads to high levels of amplification of ee.S everal studies have been undertaken to understand the mechanism of this reaction. Thel arge amplification of ee observed in this autocatalytic reaction is often explained by the formation of aggregates, which has been proposed to account for the positive nonlinear effect observed during asymmetric catalysis.[11] Mechanistic studies based on kinetic experiments, [12] reaction mo...

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Section: Methodssupporting

confidence: 82%

Section: Methodsmentioning

confidence: 98%

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

See 2 more Smart Citations

Crystal Structure of the Isopropylzinc Alkoxide of Pyrimidyl Alkanol: Mechanistic Insights for Asymmetric Autocatalysis with Amplification of Enantiomeric Excess

et al. 2015

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“…Because an amine is a Lewis base, it coordinates to the zinc atom of dialkylzinc [51], and this coordination enhances the nucleophilic character of the dialkylzinc. We reasoned as follows: when achiral amine is added to the reaction between aldehyde 1 and i-Pr 2 Zn, the achiral amine acts as a catalyst to promote the formation of racemic alkanol 2 with statistical fluctuation of chirality.…”

Section: Resultsmentioning

confidence: 99%

Spontaneous absolute asymmetric synthesis promoted by achiral amines in conjunction with asymmetric autocatalysis

et al. 2010

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The origin of homochirality of organic compounds such as L-amino acids and D-sugars have intrigued many scientists, and several hypotheses regarding its homochirality have been proposed. According to the statistical theory, small fluctuations in the ratio of the two enantiomers are present in a racemic mixture obtained from the reaction of achiral molecules. We report herein the reaction of pyrimidine-5-carbaldehyde and diisopropylzinc in the presence of achiral amine such as N,N'-dimethylpiperazine, N,N'-diethylpiperazine or N-methylmorpholine but in the absence of a chiral substance. The stochastic formation of (S)-and (R)-pyrimidyl alkanols with detectable ee was observed. This study shows that the slight fluctuation of the enantiomeric ratio of pyrimidyl alkanol produced at the initial reaction step can be enhanced significantly in conjunction with asymmetric autocatalysis with amplification of enantiomeric excess. We believe that the stochastic behavior in the formation of pyrimidyl alkanol constitutes one of the conditions necessary for spontaneous absolute asymmetric synthesis.

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Crystal Structure of the Isopropylzinc Alkoxide of Pyrimidyl Alkanol: Mechanistic Insights for Asymmetric Autocatalysis with Amplification of Enantiomeric Excess

et al. 2015

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Diisopropyl(N,N,N′,N′-tetramethylethylenediamine)zinc(II), the first crystal structure of a diisopropylzinc complex

Cited by 9 publications

References 9 publications

Crystal Structure of the Isopropylzinc Alkoxide of Pyrimidyl Alkanol: Mechanistic Insights for Asymmetric Autocatalysis with Amplification of Enantiomeric Excess

Crystal Structure of the Isopropylzinc Alkoxide of Pyrimidyl Alkanol: Mechanistic Insights for Asymmetric Autocatalysis with Amplification of Enantiomeric Excess

Spontaneous absolute asymmetric synthesis promoted by achiral amines in conjunction with asymmetric autocatalysis

Crystal Structure of the Isopropylzinc Alkoxide of Pyrimidyl Alkanol: Mechanistic Insights for Asymmetric Autocatalysis with Amplification of Enantiomeric Excess

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