| Aziridines were recognized as versatile building blocks and useful synthetic intermediates,and widely applied in the synthesis of natural products and medicinal reagents.Three-membered ring system of aziridines is highly strained.Due to ring constrain aziridines readily undergo ring-opening reactions with nucleophiles to form amino acids,chiral ligands and biologically active compounds.Therefore,ring-opening reactions have been an attractive filed in modern organic chemistry.In the past decades, tandem reactions of designed precursors brought great attention to the construction of complicated compounds.Owing to the advantages of greatly enhancing synthetic efficiency,forming two or more bonds in one pot,and avoiding the purification procedures of intermediates,the tandem reaction played a very important role in modern organic synthetic chemistry.In this context,we investigate an efficient route to dihydroxazine derivatives via tandem ring-opening/closing reactions of N-Ts aziridines with aryl proparglic alcohols.The main contents are brief as follows:1.A series of new dihydroxazines have been efficiently prepared from tandem ring-opening/closing reactions of various N-Ts aziridines and aryl propargyl alcohols promoted by t-BuOK.The reaction condition has been optimized and the scope of the tandem ring-opening/closing reactions has been studied.2.The structure of new cyclic dihydroxazine product was unambiguously confirmed by X-ray diffraction.On the basis of the experimental results,a possible mechanism was proposed.Furthermore,the process of ring-opening,isomerization and ring-closing was confirmed by experimental methods and NMR analysis.3.Morpholine derivatives were conveniently obtained by an ionic hydrogenation. Noteworthy,only cis morpholine derivatives was observed in the hydrogenation by TFA/Et3SiH at 50℃for isopropyl-substituted dihydroxazines.The tosy group of morpholine derivatives could be readily removed to afford chiral 3,5-disubstituted morpholine.
|
PDF Full Text Request