497-02-9Relevant articles and documents
Nickel-Catalyzed Asymmetric Reductive 1,2-Carboamination of Unactivated Alkenes
He, Jun,Xue, Yuhang,Han, Bo,Zhang, Chunzhu,Wang, You,Zhu, Shaolin
supporting information, p. 2328 - 2332 (2020/01/08)
Starting from diverse alkene-tethered aryl iodides and O-benzoyl-hydroxylamines, the enantioselective reductive cross-electrophilic 1,2-carboamination of unactivated alkenes was achieved using a chiral pyrox/nickel complex as the catalyst. This mild, modular, and practical protocol provides rapid access to a variety of β-chiral amines with an enantioenriched aryl-substituted quaternary carbon center in good yields and with excellent enantioselectivities. This process reveals a complementary regioselectivity when compared to Pd and Cu catalysis.
Synthesis of β-Chiral Amines by Dynamic Kinetic Resolution of α-Branched Aldehydes Applying Imine Reductases
Matzel, Philipp,Wenske, Sebastian,Merdivan, Simon,Günther, Sebastian,H?hne, Matthias
, p. 4281 - 4285 (2019/08/20)
Imine reductases (IREDs) allow the one-step preparation of optically active secondary and tertiary amines by reductive amination of ketones. Until now, mainly α-chiral amines have been prepared by this route. In this study, we explored the possibility of synthesizing β-chiral amines, a class of compounds which is also frequently found as structural motif in pharmaceuticals but much more challenging to prepare due to the following reasons: (i) The aldehyde substrate already contains the chiral center and needs to be racemized to enable full conversion. (ii) Because the intermediate imine bears the stereo center two carbon atoms remote to the imine nitrogen, it is more challenging to achieve high enantioselectivity compared to α-chiral amine synthesis. For investigating the proof of concept, we first confirmed that different IREDs are able to convert a variety of α-branched aldehydes when combined with five different amine substrates. The IRED from Streptomyces ipomoeae was a suitable enzyme facilitating the dynamic kinetic resolution of 2-phenylpropanal and a substituted 2-methyl-3-phenylpropanal: the corresponding N-methylated β-chiral amines were obtained with '95 % conversion and 78 and 95 %ee. Other amines were formed with low to moderate enantiomeric excess. This exemplifies the potential of IREDs for the one-step synthesis of secondary β-chiral amines, but also the challenge to identify highly selective enzymes for a desired amine product.
The remarkable promotion of in situ formed Pt-cobalt oxide interfacial sites on the carbonyl reduction to allylic alcohols
Li, Chenyue,Ke, Changxuan,Han, Ruirui,Fan, Guoli,Yang, Lan,Li, Feng
, p. 78 - 87 (2018/06/06)
Pt catalysts attract increasing attention for selectively hydrogenating α,β-unsaturated aldehydes to produce allylic alcohols, thanks to their relatively satisfactory selectivity towards the reduction of C[dbnd]O bond over C[dbnd]C bond. Here, new carbon supported cobalt oxide-decorated platinum nanocatalysts for highly selective hydrogenation of cinnamaldehyde were fabricated via a facile composite precursor route. As-fabricated cobalt oxide-decorated Pt catalyst at a Co/Pt atomic ratio of 0.6 was found to exhibit an exceptional catalytic performance with an extremely high 99% yield of cinnamyl alcohol under mild reaction conditions (2 MPa H2 and 80 °C). In contrast to that of the undecorated Pt one, the intrinsic activity of the cobalt oxide-decorated Pt-based one, i.e. the turnover frequency for cinnamaldehyde conversion (4.19 s?1), was significantly increased by 9.5 times. The present catalyst system presents a particularly dramatic enhancement in catalytic performance, in comparison with other Pt-based hydrogenation catalysts previously reported. Such exceptional catalytic efficiency was probably corelated with unique geometric and electronic modifications of Pt particles by CoOx species, thereby giving rise to both the increased exposed active metal surface and the favorable electron-rich state of Pt0 species. Correspondingly, the rate of cinnamaldehyde conversion could be improved and the adsorption of the carbonyl group could be strengthened. This synergy between CoOx species and Pt sites is accounted for the observed superiority of CoOx-decorated Pt catalyst to Co-free Pt one in selective hydrogenation of carbonyl compounds.
