Synthesis of Chiral Nine‐Membered N‐Heterocycles through Silver(I)‐Promoted Cycloaddition and Rearrangement from <i>N</i>‐Vinyl‐α,β‐Unsaturated Nitrones with Chiral 3‐Propioloyloxazolidin‐2‐Ones
Xiaoting Qin, Ning Zou, Xiaoling Cheng, Cui Liang, Dong‐Liang Mo
Abstract
Abstract A variety of chiral nine‐membered N‐heterocycles were prepared in moderate to good yields with high diastereoselectivity through a silver(I)‐catalyzed [3+2] cycloaddition and [3,3]‐rearrangement of N ‐vinyl‐α, β‐unsaturated nitrones and chiral 3‐propioloyloxazolidin‐2‐ones. Experimental studies showed that silver catalyst promoted the cycloaddition and rearrangement process, and the stereochemistry of the nine‐membered N ‐heterocycles was controlled via [3,3]‐rearrangement by chiral oxazolidinone‐auxiliary through a boat‐like transition state. Moreover, the obtained nine‐membered N ‐heterocycle diastereomers were converted to chiral pyrrolizines with high diastereoselectivity and pyrrolizine carboxylate was obtained in 54% yield with 90% ee by the removal of chiral auxiliary. magnified image