About Dendrimers: Structure, Physical Properties, and Applications

Hydrogenation is a core technology in chemical synthesis. High rates and selectivities are attainable only by the coordination of structurally well-designed catalysts and suitable reaction conditions. The newly devised [RuCl(2)(phosphane)(2)(1,2-diamine)] complexes are excellent precatalysts for homogeneous hydrogenation of simple ketones which lack any functionality capable of interacting with the metal center. This catalyst system allows for the preferential reduction of a C=O function over a coexisting C=C linkage in a 2-propanol solution containing an alkaline base. The hydrogenation tolerates many substituents including F, Cl, Br, I, CF(3), OCH(3), OCH(2)C(6)H(5), COOCH(CH(3))(2), NO(2), NH(2), and NRCOR as well as various electron-rich and -deficient heterocycles. Furthermore, stereoselectivity is easily controlled by the electronic and steric properties (bulkiness and chirality) of the ligands as well as the reaction conditions. Diastereoselectivities observed in the catalytic hydrogenation of cyclic and acyclic ketones with the standard triphenylphosphane/ethylenediamine combination compare well with the best conventional hydride reductions. The use of appropriate chiral diphosphanes, particularly BINAP compounds, and chiral diamines results in rapid and productive asymmetric hydrogenation of a range of aromatic and heteroaromatic ketones and gives a consistently high enantioselectivity. Certain amino and alkoxy ketones can be used as substrates. Cyclic and acyclic alpha,beta-unsaturated ketones can be converted into chiral allyl alcohols of high enantiomeric purity. Hydrogenation of configurationally labile ketones allows for the dynamic kinetic discrimination of diastereomers, epimers, and enantiomers. This new method shows promise in the practical synthesis of a wide variety of chiral alcohols from achiral and chiral ketone substrates. Its versatility is manifested by the asymmetric synthesis of some biologically significant chiral compounds. The high rate and carbonyl selectivity are based on nonclassical metal-ligand bifunctional catalysis involving an 18-electron amino ruthenium hydride complex and a 16-electron amido ruthenium species.

https://onlinelibrary.wiley.com/doi/pdf/10.1002/1521-3773%2820010105%2940%3A1%3C40%3A%3AAID-ANIE40%3E3.0.CO%3B2-5

Asymmetric Catalysis by Architectural and Functional Molecular Engineering: Practical Chemo‐ and Stereoselective Hydrogenation of Ketones

Recent Advances in the Baylis−Hillman Reaction and Applications

1,2-Amino Alcohols and Their Heterocyclic Derivatives as Chiral Auxiliaries in Asymmetric Synthesis

Large-scale applications of transition metal-catalyzed couplings for the synthesis of pharmaceuticals.

Asymmetric amplification during self-replication is a key feature that is used to explain the origin of homochirality. Asymmetric autocatalysis of 5-pyrimidyl alkanol in the asymmetric addition of diisopropylzinc to pyrimidine-5-carbaldehyde is a unique example of this phenomenon. To obtain mechanistic insight into this reaction, the crystallization of possible intermediates, specifically zinc alkoxides of this 5-pyrimidyl alkanol, was investigated. Single-crystal X-ray diffraction analysis of the obtained alkoxide crystals reveals the existence of tetramer or higher oligomer structures in this asymmetric autocatalytic system.

Structural Study of Asymmetric Autocatalysis by X-Ray Crystallography

The discovery and development of asymmetric autocatalysis, in which the structures of the chiral catalyst and the chiral product are the same, are described. Chiral 5-pyrimidyl, 3-quinolyl, and 5-carbamoyl-3-pyridyl alkanols act as highly enantioselective asymmetric autocatalysts in the enantioselective addition of diisopropylzinc to the corresponding aldehydes, such as pyrimidine-5-carbaldehyde. 2-Alkynyl-5-pyrimidyl alkanol with an enantiomeric excess (ee) of >99.5% automultiplies practically perfectly as an asymmetric autocatalyst in a yield of >99% and >99.5% ee. Asymmetric autocatalysis with an amplification of ee has thus been realized. Consecutive asymmetric autocatalysis starting with chiral 2-alkynylpyrimidyl alkanol of only 0.6% ee amplifies its ee significantly, and yields itself as the product with >99.5% ee. The reaction of pyrimidine-5-carbaldehyde and diisopropylzinc in the presence of chiral initiators with low ee’s, such as secondary alcohol, amine, carboxylic acid, mono-substituted [2.2]paracyclophane, and chiral primary alcohols due to deuterium substitution, regulates the absolute configuration of the resulting pyrimidyl alkanols, and the ee of the resulting pyrimidyl alkanol is much higher than that of the chiral initiator. Leucine and [6]helicene with very low ee’s, which are known to be induced by circularly polarized light (CPL), also serve as chiral initiators to produce pyrimidyl alkanol with higher ee’s. Overall, the process represents the first correlation between the chirality of CPL and an organic compound with very high ee. Chiral inorganic crystals, such as quartz and sodium chlorate, act as chiral inducers in the asymmetric autocatalysis of pyrimidyl alkanol. The process correlates for the first time ever the chirality of inorganic crystals with an organic compound with very high ee. © 2001 John Wiley & Sons, Inc. and The Japan Chemical Journal Forum Chem Rec 1:321–332, 2001

Asymmetric Autocatalysis and the Origin of Chiral Homogeneity in Organic Compounds.

Catalytic asymmetric synthesis and asymmetric autocatalysis of chiral 5,5'-(3,3'-bipyridyl)-dialkanediol

An atropisomeric hydrocarbon, (R)-1,1′-binaphthyl, acts as a chiral initiator of asymmetric autocatalysis of pyrimidyl alkanol in the enantioselective addition of diisopropylzinc to pyrimidine-5-carbaldehyde to afford (S)-5-pyrimidyl alkanol 2 with 96% ee. On the other hand, in the presence of (S)-1,1′-binaphthyl, the reaction affords (R)-2 with 94% ee.

Asymmetric Autocatalysis of Pyrimidyl Alkanol Induced by Optically Active 1,1′‐Binaphthyl, an Atropisomeric Hydrocarbon, Generated from Spontaneous Resolution on Crystallization.

Kenso Soai

Papers

Structural Study of Asymmetric Autocatalysis by X-Ray Crystallography

Asymmetric Autocatalysis and the Origin of Chiral Homogeneity in Organic Compounds.

Catalytic asymmetric synthesis and asymmetric autocatalysis of chiral 5,5'-(3,3'-bipyridyl)-dialkanediol

Asymmetric Autocatalysis of Pyrimidyl Alkanol Induced by Optically Active 1,1′‐Binaphthyl, an Atropisomeric Hydrocarbon, Generated from Spontaneous Resolution on Crystallization.

The Soai reaction and its implications with the life's characteristic features of self-replication and homochirality