Novel role of carbon monoxide as a Lewis acid catalyst for Friedel-Crafts reaction [17]

Full text of DOI:10.1021/ja0165032

8626
J. Am. Chem. Soc. 2001, 123, 8626-8627
Scheme 1. Possibility of Carbon Monoxide as a Lewis Acid
Novel Role of Carbon Monoxide as a Lewis Acid
Catalyst for Friedel-Crafts Reaction
Sensuke Ogoshi,* Hiromitsu Nakashima,
Kazumasa Shimonaka, and Hideo Kurosawa*
Department of Applied Chemistry
Faculty of Engineering, Osaka UniVersity
Suita, Osaka 565, Japan
ReceiVed June 27, 2001
ReVised Manuscript ReceiVed July 18, 2001
The Friedel-Crafts reaction, in which a Lewis acid plays a
crucial role to improve the efficiency of the reaction, is the most
important and traditional method to introduce an alkyl group into
an aromatic ring.1 Thus far, a gaseous Lewis acid, such as BF3,
has been employed as a very useful Lewis acid due to the simple
separation from the reaction mixture, despite its corrosive and
expensive nature. Thus, a gaseous, noncorrosive, and inexpensive
Lewis acid would allow us to construct an economical and
environmentally-friendly process. In the course of our studies on
the reaction of propargyl electrophiles with low valent transition-
metal complexes,2 we observed the occurrence of an unanticipated
Friedel-Crafts reaction under a carbon monoxide pressure, and
it was not mediated by metal complexes. This seems to bear some
relation to the fragmentation of alkoxyhalocarbenes to carbon
monoxide and haloalkanes (Scheme 1, plain arrow), in which the
generation of carbocations is proposed as a key step.3 Following
the fragmentation sequence in the reverse direction led us to
propose that carbon monoxide potentially could play an important
role as a gaseous, noncorrosive, and inexpensive Lewis acid to
generate alkyl cation. Here, we describe for the first time a novel
role of carbon monoxide as a Lewis acid for Friedel-Crafts
reactions (Scheme 1, bold arrow).
Table 1. Carbon Monoxide-Catalyzed Friedel-Crafts Reaction
The reaction of benzyl chloride in benzene either under a
carbon monoxide pressure (10 atm) or under a nitrogen atmo-
sphere in an autoclave fitted with a glass insert tube was
examined.4 Friedel-Crafts alkylation reaction proceeded at 130
°C under carbon monoxide pressure to give diphenylmethane in
excellent yield (Table 1). On the other hand, the reaction under
a nitrogen atmosphere did not proceed at all. The reaction with
toluene also afforded a mixture of Friedel-Crafts products. The
reaction under one atmospheric pressure of carbon monoxide also
proceeded quantitatively, but prolonged time was required.5
Similarly, under carbon monoxide pressure, p-methylbenzyl
chloride underwent Friedel-Crafts reaction in benzene at 130
°C or in toluene at 90 °C. The reaction of 3-phenylpropargyl
chloride with benzene proceeded under the same conditions to
give chlorocinnamyl benzene by addition of hydrogen chloride
to the triple bond of a simple Friedel-Crafts product,6 which is
a Isolated yield. b Bubbling CO for 2 min at 0 °C.
a highly atom-economic reaction. Friedel-Crafts acylation of
hydrocinnnamoyl chloride with toluene also proceeded, although
more severe conditions were needed.7 The isolation of the reaction
product is extremely easy; after the release of carbon monoxide
in a well-ventilated fume hood, only evaporation of the solvent
gave isolated products, since carbon monoxide is a gaseous Lewis
acid and does not undergo such complexation with HCl to
transform the Lewis acid to nonvolatile compounds as ordinary
Lewis acids do.
To confirm the role of carbon monoxide, control reactions were
carried out, and the results are summarized in Table 2. The
reaction of benzyl chloride in benzene-d6 under carbon monoxide
pressure (5 atm) in a pressure NMR tube at 130 °C for 10 h
proceeded smoothly to give diphenylmethane-d5 in 95% yield (run
1). To rule out the possibility that a pressurized atmosphere
promotes the reaction, the same reaction was attempted under a
(1) Olah, G. A., Ed. Friedel-Crafts Chemistry; Wiley: New York, 1973.
Olah, G. A.; Krishnamurti, R.; Prakash, G. K. S. In ComprehensiVe Organic
Synthesis, 1st ed.; Trost, B. M., Ed.; Pergamon Press: Oxford, 1991; Vol. 3,
p 293.
(2) Ogoshi, S.; Nishida, T.; Shinagawa, T.; Kurosawa, H. J. Am. Chem.
Soc. 2001, 123, 7164. Ogoshi, S.; Nishida, T.; Tsutsumi, K.; Ooi, M.;
Shinagawa, T.; Akasaka, T.; Yamane, M.; Kurosawa, H. J. Am. Chem. Soc.
2001, 123, 3223.
(3) Moss, R. A. Acc. Chem. Res. 1999, 32, 969. Yan, S.; Sauers, R. R.;
Moss, R. A. Org. Lett. 1999, 1, 1603.
(4) A solution of electrophile in benzene or toluene (66.4 mM) was placed
into a glass insert tube in an autoclave, then was pressurized with carbon
monoxide and heated at 130 °C or 90 °C for 10 h. Without a glass insert
tube, reaction proceeded under a nitrogen atmosphere, since the oxidized
autoclave inside wall could act as a Lewis acid to promote Friedel-Crafts
reaction.
(6) Maroni, R.; Melloni, G.; Modena, G. J. Chem. Soc., Perkin Trans. I
1973, 2491.
(5) A solution of benzyl chloride in toluene was placed into a pressure-
resistant glass tube, and carbon monoxide was bubbled into the solution for
2 min at 0 °C. Then, the solution was heated at 130 °C for 30 h.
(7) Saito, S.; Sato, Y.; Ohwada, T.; Shudo, K. J. Am. Chem. Soc. 1994,
116, 2312. Nonoshita, K.; Maruoka, K.; Yamamoto, H.; Bull. Soc. Chem.
Jpn. 1988, 61, 2241.
10.1021/ja0165032 CCC: $20.00 © 2001 American Chemical Society
Published on Web 08/08/2001

Communications to the Editor
J. Am. Chem. Soc., Vol. 123, No. 35, 2001 8627
Table 2. Control Reactions
Most of studies on carbon monoxide concern the efficiency of
incorporation of carbon monoxide into organic compounds;
however, thus far, the application of carbon monoxide as a
reaction promoter has not been studied at all. Thus, the new aspect
of carbon monoxide reported here for the first time as a
noncorrosive, economical, and easily re-collectable gaseous,
smallest Lewis acid is very important from the viewpoints of
organic, physical, industrial, theoretical, combinatorial, and green
chemistry. Moreover, it would not only allow us to construct new
reactions catalyzed by carbon monoxide but also require us to
reconsider the role of carbon monoxide in the reported reactions
under carbon monoxide atmosphere. Further efforts related to this
reaction including kinetic and computational studies are under
progress in this laboratory.
run
conditions
CO 5 atom, 10 h
N2 5 atm, 10 h
CO2 5 atm, 10 h
Fe(CO)5 5 mol% N2 1 atm, 17 h
Fe(CO)5 5 mol% CO 5 atm, 17 h
yield
95%
no reaction
no reaction
30%
1
2
3
4
5
10%
a NMR yield.
pressurized atmosphere of nitrogen (run 2) or carbon dioxide (run
3), but in vain. Moreover, the same reaction was examined in
the presence of a catalytic amount of Fe(CO)5, since iron
pentacarbonyl, Fe(CO)5, could be generated in a carbon monoxide
cylinder8 and metal carbonyl complexes could be a catalyst for
Friedel-Crafts reaction.9 In fact, Fe(CO)5 did catalyze the reaction
(run 4); however, the yield was much lower than that in run 1.10
Moreover, under carbon monoxide pressure the reaction proceeded
much more slowly (run 5), which rules out the possibility that
Fe(CO)5 catalyzes the reaction in run 1 and indicates that carbon
monoxide acts as a Lewis acid for Friedel-Crafts reaction.
Acknowledgment. Partial support of this work through CREST of
the Japan Science and Technology Corporation and Grants-in-Aid for
Scientific Research from the Ministry of Education, Science and Culture,
Japan, is gratefully acknowledged.
JA0165032
(10) A solution of benzyl chloride (6.3 mg, 0.05 mmol) in 0.5 mL of C6D6
was pressurized with carbon monoxide (5 atm) and heated at 130 °C for 10
h in a pressure-resistant NMR tube. For the reactions in the presence of
5 mol % of Fe(CO)5, 0.5 mg of Fe(CO)5 was added. NMR yields are given.
In control reactions, carbon monoxide compressed into a cylinder in a month
was used, in which less than 0.52 ppm of Fe(CO)5 was generated.8 This
concentration corresponds to the presence of less than 0.005 mol% of
Fe(CO)5 in run 1.
(8) Carbon monoxide cylinder stability test in SUMITOMO SEIKA
CHEMICALS CO., LTD.
(9) Shimizu, I.; Sakamoto, T.; Kawaragi, S.; Maruyama, Y.; Yamamoto,
A. Chem. Lett. 1997, 137. Kusama, H.; Narasaka, K. Bull. Chem. Soc. Jpn.
1995, 68, 2379.