Hypervalent iodine in synthesis. 65: A new route to synthesize N-acylbenzotriazoles via palladium catalyzed carbonylation of benzotriazole and hypervalent iodonium salts in the presence of carbon monoxide

Article abstract of DOI:10.1081/SCC-100103981

N-acylbenzotriazoles are obtained directly in fair yields by palladium-catalyzed carbonylation of diaryliodonium salts with benzotriazoles in the presence of carbon monoxide.

Full text of DOI:10.1081/SCC-100103981

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HYPERVALENT IODINE IN
SYNTHESIS. 65: A NEW
ROUTE TO SYNTHESIZE N-
ACYLBENZOTRIAZOLES VIA
PALLADIUM CATALYZED
CARBONYLATION OF
BENZOTRIAZOLE AND
HYPERVALENT IODONIUM
SALTS IN THE PRESENCE OF
CARBON MONOXIDE
Li Wang a & Zhen-Chu Chen b
a Department of Chemistry , Zhejiang University,
(XiXi Campus) , Hangzhou, 310028, P.R. China
b Department of Chemistry , Zhejiang University,
(XiXi Campus) , Hangzhou, 310028, P.R. China
Published online: 09 Nov 2006.
To cite this article: Li Wang & Zhen-Chu Chen (2001) HYPERVALENT IODINE
IN SYNTHESIS. 65: A NEW ROUTE TO SYNTHESIZE N-ACYLBENZOTRIAZOLES VIA
PALLADIUM CATALYZED CARBONYLATION OF BENZOTRIAZOLE AND HYPERVALENT
IODONIUM SALTS IN THE PRESENCE OF CARBON MONOXIDE, Synthetic
Communications: An International Journal for Rapid Communication of Synthetic
Organic Chemistry, 31:11, 1633-1637, DOI: 10.1081/SCC-100103981

To link to this article: http://dx.doi.org/10.1081/SCC-100103981
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SYNTHETIC COMMUNICATIONS, 31(11), 1633–1637 (2001)
HYPERVALENT IODINE IN SYNTHESIS. 65:
A NEW ROUTE TO SYNTHESIZE
N-ACYLBENZOTRIAZOLES VIA
PALLADIUM CATALYZED
CARBONYLATION OF BENZOTRIAZOLE
AND HYPERVALENT IODONIUM SALTS IN
THE PRESENCE OF CARBON MONOXIDE
Li Wang andZhen-Chu Chen *
Department of Chemistry, Zhejiang University,
(XiXi Campus) Hangzhou, 310028, P.R. China
ABSTRACT
N-acylbenzotriazoles are obtained directly in fair yields by
palladium-catalyzed carbonylation of diaryliodonium salts
with benzotriazoles in the presence of carbon monoxide.
As a synthetic auxiliary, benzotriazole offers many advantages. It is an
inexpensive, stable compound, and can be easily removed at the end of the
synthetic sequence, benzotriazole residue can be introduced into a molecule,
and activate groups to which they are attached. So, the versatile applications
of benzotriazole in organic chemistry has been explored and many papers
* Corresponding author.
1633
Copyright & 2001 by Marcel Dekker, Inc.
www.dekker.com

1634
WANG AND CHEN
have been published including some reviews.1 N-acylbenzotriazoles are
powerful acylation agents and have many applications in organic chemistry,
such as in the anionic polymerization of lactants to obtain polymers2 in the
acetylation of proteins,3 with trialkylaluminums to give ketones4 and in the
acetone-sensitized photolysis to form a cyclopentadiene derivative.5 Several
synthetic methods for N-acylbenzotriazoles are available. Most
previous preparations of acylbenzotriazoles have utilized acid chlorides by
reaction with 1-(trimethylsilyl)-benzotriazole,6 with 1-(tributylstannyl)ben-
zotriazole7 or with 1-(hydroxymethyl)benzotriazole.8 However, the dis-
advantages of using acid chlorides are obvious. They are highly reactive
and often result in undesired complications; many acid chlorides are
unstable, difficult to prepare, and liquids with unpleasant odors. Recently,
Katritzky et al., reported the directly reaction of carboxylic acids with
1-(methanesulfonyl)benzotriazole to form the N-acylbenzotriazoles.8
However, to prepare the 1-(methanesulfonyl)benzotriazole requires several
steps. In our attempts to find a method to avoid using acids chlorides for
reaction at mild conditions, we focused our attention to palladium-catalyzed
carbonylation of diaryliodonium salts with easily available benzotriazole.
Recently, as a highly active electrophilic reagents, diaryliodonium salts have
been used extensively in our lab.10 We now report palladium-catalyzed
carbonylation of diaryliodonium and benzotriazole under one atmosphere
pressure of carbon monoxide at room temperature which is shown in
Scheme 1. The results are summarized in Scheme 1 and Table 1.
Scheme 1.
To optimize the reaction conditions, a series of experiments have been
carried out. Among the palladium catalysts Pd(OAc)2, PdCl2, Pd(PPh3)2Cl2
and Pd(PPh3)4 tested, Pd(OAc)2 is the best choices. The reaction was found
to be general. Several diaryliodonium salts containing various substituents,
such as methoxy, methyl and chloro groups were sÀuccessfully reacted. The
PhI(OH)OTs (entry 2) and (PhCH ¼ CH)IþPhBF4 (entry 6) also reacted
smoothly.
In conclusion, a new synthetic route to N-acylbenzotriazoles has
been developed by the palladium-catalyzed carbonylation of diaryliodonium
salts with the benzotriazole under one atmosphere pressure of carbon
monoxide.

HYPERVALENT IODINE IN SYNTHESIS. 65
Table 1. N-Substituted Phenacyl Benzotriazolesa
1635
Yield
(%)b
À
Entry
1
Ar2I+BF4
Catalysts
Base
Product
Ph2IþBF4
Pd(OAc)2 K2CO3 1PhCOBt-1
K2CO3 1PhCOBt-1
66
60
71
75
60
62
À
2PhI(OH)OTs
PÀd(OAc)
2
3
4
5
6
(p-CH3C6H4)2IþBF4
(p-CH3OC6H4)2IþBF4
Pd(OAc)2 K2CO3 p-CH3C6H4COBt-1
Pd(OAc)2 K2CO3 p-CH3OC6H4COBt-1
Pd(OAc)2 K2CO3 p-ClC6H4COBt-1
Pd(OAc)2 K2CO3 E-(PhCH ¼ CH)
COBt-1
À
À
(p-ClC6H4)2I+BF4
E-(PhCH ¼ CH)Iþ
À
PhBF4
a Reagent and conditions: 1 mmol iodonium salt, 2.5 mmol K2CO3, 5 mol%
Pd(OAc)2 and 1 mmol benzotriazole, in 5 ml DMF at 80C under one atmosphere
of carbon monoxide; b isolated yields.
EXPERIMENTAL
1H-NMR spectra were recorded on a PMX-60 spectrometer,
using CDCl3 as the solvent with TMS as an internal standard. IR
spectra were determined on a PE-683 Spectrophotometer. Melting Points
are uncorrected.
General Procedure for Synthesis of N-Substituted
Phenylacylbenzotriazoles
The benzotriazole (1 mmol) was added to a stirred solution of
diaryliodonium tetrafluoroborate (1 mmol), Pd(OAc)2 (11 mg, 5 mol%),
K2CO3(345 mg, 2.5 mmol) and anhydrous DMF (10 mL) under one
atmosphere of carbon monoxide at 50ꢀC. The mixture was stirred at
50ꢀC for 10 hours, evaporated in vacuo and then quenched in a
saturated NH4Cl solution (5 mL), extracted with CH2Cl2 (2 Â 10 mL).
The organic layer was dried over anhydrous Na2SO4 and evaporated
in vacuo. The crude product was separated by preparative thin layer
chromatography on silica gel with 1:5 ethyl acetate-hexane as eluent
to afford the product, N-substituted phenylacylbenzotriazoles.
1-Benzoylbenzotriazole (Entry.1, 2) m.p. 111–113ꢀC (lit.11 112–114ꢀC)
1H NMR 7.45–7.70 (m, 5H) 8.05–8.35 (m, 4H); IR.(KBr) 1702, 1643,
1289 cmÀ1
.

1636
WANG AND CHEN
1-40-methylbenzoylbenzotriazole (Entry.3) m.p. 115–116ꢀC (lit.11
114–116ꢀC) H-NMR 2.32 (s, 3H) 7.28–7.60 (m, 4H) 7.95–8.26 (m, 4H)
1
I.R.(KBr) cmÀ1 1702, 1643, 1289 cmÀ1
.
1-40-methyoxybenzoylbenzotriazole (Entry.4) m.p. 110–111ꢀC (lit.11
108–110ꢀC) 1H-NMR 3.79 (s, 3H), 7.40–8.40(m, 8H), IR.(KBr) 1714,
1620, 1260 cmÀ1
.
1-40-chlorobenzoylbenzotriazole (Entry.5) m.p. 119–120ꢀC (lit.11
118–120ꢀC) 1H-NMR 7.45–7.70 (m, 4H), 8.10–8.42(m, 4H); IR.(KBr)
1695, 1680, 1270 cmÀ1
1-Cinnamoylbenzotriazole
158–159ꢀC) 1H-NMR 7.23–7.80 (m, 9H), 8.12–8.45 (m, 2H); IR.(KBr)
1685, 1605, 1279 cmÀ1
.
(Entry.6)
m.p.
158–160ꢀC
(lit.12
.
ACKNOWLEDGMENT
We appreciate the financial support of the National Science
Foundation of China (Project 29472036).
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Received in Japan June 12, 2000