Ferrocenyl bisoxazoline as an efficient non‐phosphorus
ligand for palladium‐catalyzed copper‐free Sonogashira
reaction in aqueous solution
| Jingxin Wu
| Xinwei He
| Yongjia Shang
Material and Chemical Engineering
College, Zhengzhou University of Light
Industry, Zhengzhou 450001, Henan
Province, People's Republic of China
College of Chemistry and Materials
Science, Anhui Normal University, Wuhu
241000, Anhui Province, People's Republic
Shuyan Yu, Material and Chemical
Engineering College, Zhengzhou
University of Light Industry, Zhengzhou
Yongjia Shang, College of Chemistry
and Materials Science, Anhui Normal
University, Wuhu 241000, China.
Doctoral Research Fund of Zhengzhou
University of Light Industry, Grant/Award
Number: 2014BSJJ009; Foundation of
Henan Educational Committee, Grant/
Award Number: 17A150022; National
Natural Science Foundation of China,
Grant/Award Number: 21372008 and
‐catalyzed Sonogashira coupling reactions of alkynes and a variety of
aryl halides with 1,3‐bis(5‐ferrocenylisoxazoline‐3‐yl)benzene as an efficient
non‐phosphorus ligand under copper‐free conditions are presented. The main
advantages over previous methodologies include low catalyst loading (0.2 mol%
and 0.4 mol% ferrocenyl bisoxazoline ligand are sufficient for these cou-
pling reactions), less problematic reaction medium (water–dimethylformamide)
and more convenient operation (no requirement for nitrogen protection).
copper‐free conditions, non‐phosphorus ligand, Sonogashira reaction
1 | INTRODUCTION
The coupling of aryl or vinyl halides (or triflate) with
terminal alkynes catalyzed by palladium, commonly
termed Sonogashira cross‐coupling reactions, has been
recognized as one of the most important sp
carbon bond formation reactions in organic synthesis.
The resulting internal alkynes or enynes are important
intermediates for pharmaceuticals,
biologically active molecules,
and optical and liquid‐crystal materials.
The most com-
monly utilized catalytic systems for these reactions
include phosphine‐ligated palladium catalysts together
with CuI as a co‐catalyst under degassed conditions.
However, phosphine ligands suffer some drawbacks, such
as sensitivity to air and moisture, requirement for an inert
environment and large amounts of palladium source for
carrying out the reaction.
Also, the presence of
copper(I) could result in the formation of some Cu(I)
acetylides in situ that can readily induce oxidative
homocoupling reactions of alkynes.
Hence, the develop-
ment of new non‐phosphorus ligands with adequate activ-
ity to avoid the use of copper has become an important
topic of research in organic synthesis.
Received: 9 July 2017 Revised: 27 September 2017 Accepted: 29 September 2017
Appl Organometal Chem. 2018;32:e4156.
Copyright © 2017 John Wiley & Sons, Ltd.wileyonlinelibrary.com/journal/aoc 1of7