The catalytic activity of a simple aminoalcohol that contains a bulky super silyl group [i.e., tris(trimethylsilyl)silyl (TTMSS)] bonded to the oxygen atom at the γ-position along with a primary amine moiety was examined in the enantioselective1,3-dipolarcycloaddition of nitrones to α,β-unsaturatedaldehydes. The organocatalyst successfully provided optically active isoxazolidines in good chemical
An asymmetric Strecker-type reaction of nitrones using acetone cyanohydrin as a source of HCN has been realized. A magnesium–tartramide complex, generated from (R,R)-2,3-dihydroxy-1,4-di(pyrrolidin-1-yl)-butane-1,4-dione and MeMgBr, promoted transcyanation from the bromomagnesiumsalt of the cyanohydrin, in the presence of a catalytic amount of DBU, to afford the corresponding optically active (S)-α-amino
ABSTRACT An efficient Strecker-type reaction of nitrones with trimethylsilyl cyanide (TMSCN) catalyzed by MgI2 etherate has been achieved in a short time under mild condition. The condensations of aromatic nitrones, heterocyclic nitrones, and aliphatic nitrones with TMSCN are performed in good to excellent yields. Further dehydration of α-cyanohydroxylamine smoothly produced the α-imine nitrile in
Rhodium‐Catalyzed C−H Activation‐Based Construction of Axially and Centrally Chiral Indenes through Two Discrete Insertions
作者:Fen Wang、Jierui Jing、Yanliang Zhao、Xiaohan Zhu、Xue‐Peng Zhang、Liujie Zhao、Panjie Hu、Wei‐Qiao Deng、Xingwei Li
DOI:10.1002/anie.202105093
日期:2021.7.19
Reported herein is asymmetric [3+2] annulation of arylnitrones with different classes of alkynes catalyzed by chiralrhodium(III) complexes, with the nitrone acting as an electrophilic directing group. Three classes of chiral indenes/indenones have been effectively constructed, depending on the nature of the substrates. The coupling system features mild reaction conditions, excellent enantioselectivity
Dual Role of Pyrrolidine and Cooperative Pyrrolidine/Pyrrolidinium Effect in Nitrone Formation
作者:Sara Morales、Fernando G. Guijarro、Inés Alonso、José Luis García Ruano、M. Belén Cid
DOI:10.1021/acscatal.5b01726
日期:2016.1.4
The formation of nitrones by direct condensation between equimolecular amounts of N-substituted hydroxylaminehydrochlorides and aromatic or aliphatic aldehydes is efficiently promoted by pyrrolidine in a matter of minutes under very mild conditions in almost quantitative yields after a simple filtration through a short pad of silica gel. According to theoretical, spectroscopic, and experimental studies