An asymmetric domino reaction was developed utilizing readily available cyclic α-dehydroamino ketones and aldehydes, which when subjected a 2-iodoxybenzoic acid (IBX)-mediated oxidation gives pyrrolidinone-containing tricyclic derivatives. trans-Perhydroindolic acid proved to be an efficient organocatalyst in this reaction (up to 94% yield, 99% ee, and >20:1 dr). The product could be conveniently converted
Brine-Stabilized 2,2,2-Trifluorodiazoethane and Its Application in the Synthesis of CF<sub>3</sub>–Substituted Cyclopropane α-Amino Acids
作者:Chuan-Le Zhu、Li-Jun Yang、Shen Li、Yan Zheng、Jun-An Ma
DOI:10.1021/acs.orglett.5b01450
日期:2015.7.17
CF3CHN2 in CH3CN is realized. This method shows excellent generality, affording a wide range of trifluoromethyl-substituted cyclopropanes bearing azlactone rings in good to high yields and diastereoselectivities. With the products in hand, the trifluoromethyl-substituted cyclopropane α-amino acids and relative peptide derivatives could be readily obtained.
Cation-Triggered Switchable Asymmetric Catalysis with Chiral Aza-CrownPhos
作者:Guang-Hui Ouyang、Yan-Mei He、Yong Li、Jun-Feng Xiang、Qing-Hua Fan
DOI:10.1002/anie.201411593
日期:2015.3.27
AbstractAn aza‐crown ether, modified phosphoramidite ligand, has been designed and synthesized. The ON/OFF reversible switch of catalytic activity for its rhodium catalyst was thoroughly investigated in the asymmetric hydrogenation of dehydroamino acid esters modulated by host–guest interactions. In the OFF state, the catalyst is almost inactive (less than 1 % conversion) because of the formation of an intermolecular sandwich complex by two aza‐crown ether moities and the cationic rhodium metal center. In using alkali‐metal‐cations as the trigger, the catalytic activity was turned ON and consequently resulted in full conversions and excellent enantioselectivities (up to 98 % ee).
Silver-Promoted Direct Phosphorylation of Bulky C(sp<sup>2</sup>)–H Bond to Build Fully Substituted β-Phosphonodehydroamino Acids
作者:Hao-Qiang Cao、Hao-Nan Liu、Zhe-Yuan Liu、Baokun Qiao、Fa-Guang Zhang、Jun-An Ma
DOI:10.1021/acs.orglett.0c02229
日期:2020.8.21
A general and practical cross-dehydrogenative coupling protocol between readily available trisubstituted α,β-dehydro α-amino carboxylic esters and H-phosphites is described. This C(sp2)–H phosphorylation reaction proceeds with absolute Z-selectivity promoted by silver salt in a radical relay manner. The bulky tetrasubstituted β-phosphonodehydroamino acids were obtained in grams and added new modules