Diastereoselective Synthsis Of β-amido Acetals And Dihydroxazine Derivatives From The Additional Reaction Of N,O-acetals With Electron-rich Olefins

As important synthetic intermediates,imines have been widely applied in synthesis of nitrogen-containing compounds. However, due to their own instability, the application of imines was limited in organic synthesis. Thus, it is of great significance for organic synthesis to search for stable precursors of imines.In this paper, we developed an easy-operative and efficient method with the advantage of the ease to get the material and highly diastereoselectiveβ-amido acetals and dihydroxazine derivatives were gotten via a TMSOTf-catalyzed additional reaction of N, O–acetals as stable precursors of imines with electron-rich olefins including enol ethers and allylic silanes.The general conditions to expand substates was determined by optimizing the reaction conditions. The study has showed that with the TMSOTf (0.5 mmol) as catalyst, CH2Cl2 as solvent, at -78℃for 1 hour and under nitrogen atmosphere, a wide variety of N, O-acetals, except for those with the electron-withdrawing group, can well react with electron-rich olefins in moderate to good yields and high diastereoselectivities. Moreover, in the absence of catalyst, dihydroxazine derivatives with kinds of alcohols can be selectively converted intoβ-amido acetals by ring-opening reaction, which has wide application in organic synthesis because of the advantage of mild condition and operability. The molecular structure of 141bd was confirmed by single-crystal X-ray diffraction. 55 examples ofβ-amino acetals and dihydroxazine derivatives are given in this paper.The innovations of this paper as follow: We develop N, O-acetals as the stable precursor of imine, and through reacting electron-rich olefins, we have attained diverseβ-amino acetals and dihydroxazine derivatives in high diastereoselectivities as well as broad functional-group tolerance. In addition, dihydroxazine derivatives can react with diverse alcohols and led to functionalizedβ-amido acetals under mild and simple condition, which provides a new method for the synthesis of diverse 2-C branched sugar in high diastereoselectivities.