3685-22-1Relevant articles and documents
PNO ligand containing planar chiral ferrocene and axial chiral diphenol and application thereof
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Paragraph 0128-0131, (2021/06/23)
The invention discloses a PNO ligand containing planar chiral ferrocene and axially chiral diphenol and application of the PNO ligand. The PNO ligand containing planar chiral ferrocene and axially chiral diphenol is shown in any one of general formulas (I)-(IV). Or a PNO ligand containing planar chiral ferrocene and axial chiral diphenol as shown in any one of general formulas (V)-(VIII); compared with a previously reported tridentate ligand, the PNO ligand containing the planar chiral ferrocene and the axial chiral diphenol not only has good stability and easiness in synthesis, but also has planar chirality and axial chirality and has a good chiral environment, so that not only is excellent selectivity to a substrate ensured, but also the catalytic activity of a catalyst and the application range of the substrate are further improved. The chiral raw materials used in the invention are commercial bulk products, and the ligand synthesis route is simpler, so that large-scale production can be well carried out, and the method has a huge commercial application prospect.
A Practical and Stereoselective In Situ NHC-Cobalt Catalytic System for Hydrogenation of Ketones and Aldehydes
Zhong, Rui,Wei, Zeyuan,Zhang, Wei,Liu, Shun,Liu, Qiang
, p. 1552 - 1566 (2019/06/14)
Homogeneous catalytic hydrogenation of carbonyl groups is a synthetically useful and widely applied organic transformation. Sustainable chemistry goals require replacing conventional noble transition metal catalysts for hydrogenation by earth-abundant base metals. Herein, we report how a practical in situ catalytic system generated by easily available pincer NHC precursors, CoCl2, and a base enabled efficient and high-yielding hydrogenation of a broad range of ketones and aldehydes (over 50 examples and a maximum turnover number [TON] of 2,610). This is the first example of NHC-Co-catalyzed hydrogenation of C=O bonds using flexible pincer NHC ligands consisting of a N-H substructure. Diastereodivergent hydrogenation of substituted cyclohexanone derivatives was also realized by fine-tuning of the steric bulk of pincer NHC ligands. Additionally, a bis(NHCs)-Co complex was successfully isolated and fully characterized, and it exhibits excellent catalytic activity that equals that of the in-situ-formed catalytic system. Catalytic hydrogenation is a powerful tool for the reduction of organic compounds in both fine and bulk chemical industries. To improve sustainability, more ecofriendly, inexpensive, and earth-abundant base metals should be employed to replace the precious metals that currently dominate the development of hydrogenation catalysts. However, the majority of the base-metal catalysts that have been reported involve expensive, complex, and often air- and moisture-sensitive phosphine ligands, impeding their widespread application. From a mixture of the stable CoCl2, imidazole salts, and a base, our newly developed catalytic system that formed easily in situ enables efficient and stereoselective hydrogenation of C=O bonds. We anticipate that this easily accessible catalytic system will create opportunities for the design of practical base-metal hydrogenation catalysts. A practical in situ catalytic system generated by a mixture of easily available pincer NHC precursors, CoCl2, and a base enabled highly efficient hydrogenation of a broad range of ketones and aldehydes (over 50 examples and up to a turnover number [TON] of 2,610). Diastereodivergent hydrogenation of substituted cyclohexanone derivatives was also realized in high selectivities. Moreover, the preparation of a well-defined bis(NHCs)-Co complex via this pincer NHC ligand consisting of a N-H substructure was successful, and it exhibits equally excellent catalytic activity for the hydrogenation of C=O bonds.
Preparing method for trans- 4- hydroxycyclohexanecarboxylic acid
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Paragraph 0008-0010, (2017/08/27)
The invention discloses a preparing method for trans- 4- hydroxycyclohexanecarboxylic acid. The method comprises the steps of adding p-hydroxybenzoic acid, catalyst and solvent into the high pressure reactor to obtain cis- and trans- 4-hydroxycyclohexanecarboxylic acid, then adding the 4-hydroxycyclohexanecarboxylic acid into the solvent and adding a certain volume of sodium alkoxide as the catalyst, increasing the temperature and obtain trans- 4- hydroxycyclohexanecarboxylic acid with content of over 90% through isomerization reaction. Then obtaining pure trans- 4- isomerization reaction by recrystallization of petroleum ether ethyl acetate. Benefit of the invention: the invention provides a preparing method for trans- 4- hydroxycyclohexanecarboxylic acid. The raw material is easy to obtain and the product can be produced in large scale, which greatly reduces the cost.
