A highly enantioselective asymmetric catalytic synthesis of cis- and trans-aziridines can be achieved with multi-component procedure with primary amines, aldehydes and diazo compounds mediated by a chiral boroxinate (BOROX) catalyst generated from VANOL, VAPOL or t-Bu2VANOL ligands. A catalyst controlled asymmetric aziridination is reported based on the previously developed method for the multi-component cis-aziridination. The stereochemistry of the newly formed aziridines is the function of chiral boroxinate catalyst and is independent of the chiral centers already present in the aldehyde substrates. A series of aldehydes with the chiral centers presented at either α- or β-positions are investigated to find out the diastereoselectivity of the corresponding aziridines from both enantiomers of the BOROX catalyst, as well as the evaluation of ligand control over the diastereoselectivity from the matched and miss-matched pairs. The synthesis of stereoisomers of isoleucine and polyoxamic acid will be discussed as the application of this method.Meanwhile, The three-component catalytic asymmetric synthesis of trans-aziridines is introduced. This method provides direct aziridination of amines, aldehydes and diazoacetamides to give trans-aziridine-2-carboxamides with the chiral boroxinate catalyst. Taken together with our previous reported on the three-component catalytic asymmetric synthesis of cis-aziridines, the three-component aziridination can be controlled to give either cis- or trans-aziridines. The scope of the trans-aziridination is discussed along with the application in the natural product synthesis. As the extension of this methodology, an asymmetric synthesis of α-amino-β-hydroxy amides is developed by the strategy of trans-aziridination/ring-opening cascade reactions with the presence of nucleophilic phenols and carboxylic acids, with decent yields and asymmetric inductions of aminohydroxy amides achieved. The substrate scope of aldehydes and oxygen-nucleophiles will be further explored.In addition, a parallel kinetic resolution of racemic α-iminols is introduced based on the previously developed method of catalytic asymmetric α-iminol rearrangement based on a chiral zirconate complex derived from VANOL ligand. An excellent resolution of the racemic α-iminols with a phenyl and a alkyl migration group to afford a pair of amino ketone regioisomers with high enantiomeric purity. More studies will focus on the stereochemistry to reveal the mechanisms of migration.
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