Umpolung Synthesis of 1,3-Amino Alcohols: Stereoselective Addition of 2-Azaallyl Anions to Epoxides
作者:Paige E. Daniel、Alexandria E. Weber、Steven J. Malcolmson
DOI:10.1021/acs.orglett.7b01471
日期:2017.7.7
report the direct preparation of 1,3-amino alcohols that contain up to three contiguous stereogenic centers by the umpolung coupling of imines and epoxides. Nucleophilic 2-azaallyl anions, generated from imines, are stereoselectively added to epoxides to furnish 1,3-amino alcohols after hydrolysis of the product imine. Transformations afford amino alcohols with >98% site selectivity with respect to
Click à la carte: robust semi-orthogonal alkyne protecting groups for multiple successive azide/alkyne cycloadditions
作者:Ibai E. Valverde、Agnès F. Delmas、Vincent Aucagne
DOI:10.1016/j.tet.2009.06.093
日期:2009.9
We herein describe an in-depth screening and systematic comparison of five classical silyl alkyne protective groups, to evaluate their potential in the context of multiple successive copper (I)-catalyzed alkyne-azide cycloadditions (CuAAC). We confirm the relative sensitivity of TMS, especially under CuAAC conditions. The relative robustness of its higher analogues, and the discovery of mild silver-catalyzed deprotection conditions selective for TES compared to DPS or TIPS allowed us to design a strategy allowing three successive CuAAC on a single scaffold, as we have illustrated by the synthesis of a tris-triazolo model compound. (C) 2009 Elsevier Ltd. All rights reserved.