Gold‐Catalyzed One‐Step Construction of 2,3‐Dihydro‐1
<i>H</i>
‐Pyrrolizines with an Electron‐Withdrawing group in the 5‐position: A Formal Synthesis of 7‐Methoxymitosene
作者:Ze‐Yi Yan、Yuanjing Xiao、Liming Zhang
DOI:10.1002/anie.201203678
日期:2012.8.20
What a ring formation! Bicyclic dihydropyrrolizines with an electron‐withdrawing group (EWG) at the 5‐position are formed in one step from linear azidoenynes under goldcatalysis. This novel route involves the use of azide as a nitrene precursor, electronically‐controlled regioselectivity, and the generation of destabilized 1‐azapentadienium ions and their pericyclic reactions. This method was used
Synthesis of Bicyclic Imidazoles via [2 + 3] Cycloaddition between Nitriles and Regioselectively Generated α-Imino Gold Carbene Intermediates
作者:Yuanjing Xiao、Liming Zhang
DOI:10.1021/ol302102h
日期:2012.9.7
The cyclic alpha-imino gold carbene intermediate B is most likely generated in situ via regioselective nitrene transfer from an azido group to a tethered terminal alkyne in the presence of a gold catalyst and at ambient temperature. This highly electrophilic intermediate can react with a weakly nucleophilic nitrile, which is used as the reaction solvent, to deliver a bicyclic imidazole rapidly in an overall bimolecular [2 + 2 + 1] cycloaddition and in mostly serviceable yield. The competing intramolecular Huisgen reaction, although likely also catalyzed by gold, is minimized by using AuCl3 as the catalyst.
Synthesis of 1,3,4-Trisubstituted Isoquinolines by Iodine-Mediated Electrophilic Cyclization of 2-Alkynyl Benzyl Azides
作者:Dirk Fischer、Hisamitsu Tomeba、Nirmal K. Pahadi、Nitin T. Patil、Yoshinori Yamamoto
DOI:10.1002/anie.200701392
日期:2007.6.18
Visible-Light-Promoted Selenylation/Cyclization of <i>o</i>-Alkynyl Benzylazides/<i>o</i>-Propargyl Arylazides: Synthesis of Seleno-Substituted Isoquinolines and Quinolines