69854-68-8Relevant academic research and scientific papers
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
supporting information, 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.
Use of Shift Reagent with MTPA Derivatives in 19F NMR Spectroscopy IV - Determination of Enantiomeric Composition for a Variety of Secondary Cycloalkanols. A Survey
Merckx, E. M.,Lepoivre, J. A.,Lemiere, G. L.,Alderweireldt, F. C.
, p. 380 - 387 (2007/10/02)
Chiral secondary cycloalkanols (monpocyclic alcohols) are derivatized to the corresponding (R)-α-methoxy-α-trifluoromethyl-α-phenylacetic acid esters and analysed by 19F NMR in the presence of tris(6,6,7,7,8,8,8-heptafluoro-2,2-dimethyl-3,5-octanedionato)europium(III) .Using this method the enantiomeric composition can be measured for severak cyclopentanols, cyclohexanols and cycloheptanols, with a variety of substitution patterns.It is shown that a mixture of four stereoisomeric cycloalkanols, such as cis and trans disubstituted alcohols, can be analysed simultaneously.
PREPARATION OF PURE OPTICALLY ACTIVE (3S)- AND (4S)-tert-BUTYLCYCLOHEXENES.
Sadozai, S.K.,Lepoivre, J.A.,Dommisse, R.A.,Alderweireldt, F.C.
, p. 637 - 642 (2007/10/02)
(1S,3S)-3-tert-Butylcyclohexanol, obtained from enzymatic reduction of racemic 3-tert-butylcyclohexanone, is dehydrated to optically active cyclohexenes.The carbon-13 NMR spectral data and ORD-curves are given.The optical rotation of the (3S)-(+) and (4S)
