Tetrahedron Letters
Triazole acetyl gold(III) catalyzed Meyer–Schuster rearrangement
of propargyl alcohols
b,
Yongchun Yang a, Yanan Shen a, Xiaoli Wang a, Yao Zhang a, Dawei Wang a, , Xiaodong Shi
⇑
⇑
a The Key Laboratory of Food Colloids and Biotechnology, Ministry of Education, School of Chemical and Material Engineering, Jiangnan University, Wuxi 214122, Jiangsu
Province, China
b 4202 E Fowler Ave, Department of Chemistry, University of South Florida, Tampa, FL, USA
a r t i c l e i n f o
a b s t r a c t
Article history:
A new type triazole acetyl gold(III) was prepared and found to be an effective catalyst in Meyer–Schuster
rearrangement of propargyl alcohols. The reactions proceeded well under much milder conditions to
afford enones bearing a wide range of functional groups, thereby opening a new avenue for gold(III)
catalysis. In addition, TriaAuCl2 catalyst was also effective on promotion of a-haloenones synthesis.
Ó 2016 Elsevier Ltd. All rights reserved.
Received 28 January 2016
Revised 11 April 2016
Accepted 13 April 2016
Available online 13 April 2016
Keywords:
Triazole
Gold
Meyer–Schuster rearrangement
Propargyl alcohols
Haloenones
Introduction
1A
1B
HO
O
OH
Gold catalysis has been widely applied in organic transforma-
tions, and methods for their efficient, selective functionalization
to construct more complex molecules during the past several
decades.1,2 Gold(I) catalysts are usually two coordinated with
180° linear geometry, while gold(III) catalysts have a planar coor-
dination geometry, and hence the spatial environment around
the gold center can be more easily fine-tuned through ligand
design studies. However, gold(I) catalysis has achieved much more
development and concern than gold(III) catalysis, which should be
attributed to the heat stability of gold catalyst.3 The typical gold
(III) catalyst is the PicAuCl2 and their derivatives, which enriched
and evidenced the development of gold(III) catalysis (Scheme 1A).
After some pioneering works on PicAuCl2,4 Hashmi reported
PicAuCl2 catalyzed phenol synthesis, which revealed that gold(III)
precatalysts represent a typical step in catalyst-tuning by ligand
design, while they found Au(I) showed low selectivity.5 Toste
et al. described a PicAuCl2 catalyzed synthesis of azepines via inter-
molecular [4+3]-annulation reaction.6 In 2013, Waser et al devel-
oped the selective synthesis of 2- and 3-alkynylated furans based
on a domino cyclization/alkynylation process with PicAuCl2 as
catalyst.7 Chan group showed that PicAuCl2 catalyzed selective
O
O
N
N
Cl Au
Cl
N
Cl Au
Cl
N
N
O
O
O
O
N
Au O
Cl
Cl Au
Cl
O
Cl
PicAuCl2
TriaAuCl2
Scheme 1. PicAuCl2 and TriaAuCl2.
1,3-acyloxy migration/5-exo-dig cyclization/1,5-acyl migration to
afford cis-cyclopenten-2-yl d-diketones.8
Our research in developing new triazole ligands to balance the
stability and reactivity of gold catalysts has led to the recent
discovery of triazole gold(I) complexes (TA-Au),9,10 which was
achieved several applications on hydroamination, Hashmi phenol
synthesis, and 3,3-rearrangements with TA-Au(I) as a catalyst.
We have a concern about triazole ligands: could triazole adjust
the stability and reactivity of gold catalysts gold(III)? Herein, we
synthesized the TriaAu(III)Cl2 complex, which showed excellent
catalytic activity in Meyer–Schuster rearrangement of propargyl
alcohols for enone synthesis under mild conditions, which avoid
the preparation of corresponding acetate derivatives and have
large substrate exploration (Scheme 1B).
The designed (triazol-1-yl)acetic acid (1a) was synthesized
from benzotriazole and methyl 2-bromoacetate via two steps with
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0040-4039/Ó 2016 Elsevier Ltd. All rights reserved.