The NiCl2-Li-Arene (cat.) Combination as Reducing System, Part 9: Catalytic Hydrogenation of Organic Compounds using the NiCl 2-Li-(Naphthalene or Polymer-Supported Naphthalene) (cat.) Combination

Article abstract of DOI:10.1002/adsc.200390022

The reaction of lithium powder, a catalytic amount of naphthalene or polymer-supported naphthalene, and anhydrous nickel(II) chloride, in THF at room temperature, generates a finely divided and very reactive nickel(0) which has been efficiently applied to the catalytic hydrogenation of different organic compounds such as alkenes, alkynes, carbonyl compounds, imines, organic halides, aromatic compounds, hydrazines, azoxy compounds, and N-oxides.

Full text of DOI:10.1002/adsc.200390022

FULL PAPERS
The NiCl -Li-Arene (cat.) Combination as Reducing System,
2
Part 9: Catalytic Hydrogenation of Organic Compounds using the
NiCl -Li-(Naphthalene or Polymer-Supported Naphthalene) (cat.)
2
Combination
Francisco Alonso, Pablo Candela, Cecilia G o¬ mez, Miguel Yus*
Departamento de QuÌmica Org a¬ nica, Facultad de Ciencias, Universidad de Alicante, Apdo. 99, 03080 Alicante, Spain
Fax: (+34)-965 903549, e-mail: yus@ua.es
Received: July 30, 2002; Accepted: October 7, 2002
Abstract: The reaction of lithium powder, a catalytic organic compounds such as alkenes, alkynes, carbonyl
amount of naphthalene or polymer-supported naph- compounds, imines, organic halides, aromatic com-
thalene, and anhydrous nickel(II) chloride, in THF at pounds, hydrazines, azoxy compounds, and N-oxides.
room temperature, generates a finely divided and
very reactive nickel(0) which has been efficiently Keywords: catalytic hydrogenation; lithium; naphtha-
applied to the catalytic hydrogenation of different lene; nickel; polymer-supported naphthalene
Introduction
catalytic amount of an arene, which showed to be very
efficient in the reduction of a wide variety of organic
[
13a, h]
[13b]
Catalytic hydrogenation is one of the most frequently substrates such as alkenes,
alkynes,
organic halides,
reduction of many functional groups often with high nates, aromatic and heteroaromatic compounds,
carbonyl
[
13c]
[13d]
applied reactions in organic synthesis which allows the compounds and imines,
sulfo-
[13e]
[
1]
control of the chemo-, regio-, and stereoselectivity. In hydrazines, azo compounds, azoxy compounds, and N-
general, heterogeneous catalytic hydrogenation is oxides, and nitrones.
[
2]
[13f]
[13g]
The main advantages of this
preferred due to the mild reaction conditions mostly methodology are: (a) the source of hydrogen is the water
required and to the easy separation of the catalyst. contained in the nickel salt; (b) the grade of hydro-
[
3]
Among the many catalysts available, nickel catalysts
genation can be controlled by the stoichiometry of the
are universal and widely used both in the laboratory and reaction; and (c) deuterated products are easily ob-
in industry. They can be found in a supported form tained by utilizing a nickel salt containing two molecules
[
3]
[4]
[5]
(
nickel on kieselguhr, alumina, or carbon ), as a of deuterium oxide instead of water.
[
6]
nickel-aluminium alloy powder, or obtained by reduc-
However, by applying this methodology stoichiomet-
tion of nickel salts such as nickel aluminides and nickel ric amounts of the nickel salt are needed in order to get
[7]
borides, nickel precipitated from a nickel halide and good reaction conversions. In a preliminary communi-
zinc,[ or the Nic catalysts [NaH-NaOR-Ni(II) salts], cation, we reported a nickel-catalyzed hydrogenation
8]
[14]
[
9]
which generate nickel hydride species. Especially reaction involving external molecular hydrogen and
reactive are those nickel catalysts in the form of very reactive catalytic nickel(0), which was prepared
[10]
colloids or as solvated metal atom dispersed pow- from anhydrous nickel(II) chloride, lithium, and a
ders.[ However, Raney nickel is probably by far the catalytic amount of naphthalene. This reducing system
most used nickel catalyst because of its high activity, found successful application in the reduction of a wide
11]
[
3,12]
being able to reduce practically any function.
Its range of organic compounds including alkenes, alkynes,
main disadvantages are: (a) the difficulty in calculating halogenated materials, aromatic and heteroaromatic
the dosage (it is usually measured as a suspension rather compounds, hydrazines, azoxy compounds, and N-
than weighed); (b) ferromagnetic properties that pre- oxides. In all these reactions, lithium powder was
clude the use of magnetic stirring; (c) it is potentially activated by catalytic naphthalene as electron carrier,
hazardous (pyrophoric); and (d) it becomes inactive which though present in negligible amounts, is incorpo-
after prolonged storage, presumably because it loses rated in the crude reaction product unless some
hydrogen slowly. On the other hand, in the last years we purification technique is applied. On the other hand,
have developed a reduction methodology based on the polymer-supported arenes have found recent applica-
use of dihydrated nickel(II) chloride, lithium, and a tions as electron transfer reagents in lithiation processes,
Adv. Synth. Catal. 2003, 345, No. 1+2
¹ 2003 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim 1615-4150/03/3451+2-275 ± 279 $ 17.50+.50/0
275

FULL PAPERS
Francisco Alonso et al.
H
H
Table 1. Hydrogenation of alkenes and alkynes.
C
C
CH OH
H
H
Yield [%][c]
A[a] B[b]
t [h]
Entry Starting Material
1
Product
A[a] B[b]
H
C
H
C
C
C
C O
C
C
CH NH
C
N
97[d] 97[d]
0.5 0.5
1.0 1.0
NiCl2 (40%)-Li-[naphthalene (2%) or
polymer-supported naphthalene (10%)],
H2 (1 atm), THF, rt.
R
N
O
2
95
99
Y
R
Ar
N
O
N
NH
RHal
Ph
Ph
R
Ar
N
N
Ar
3
1.0 6.0
1.5 1.5
96
98
99
98
Y
H
Ph
Ph
OH
Ar
[
Y = CH, N]
OH
RH
NH
Ar N N Ar
R
4
Scheme 1.
5
3.0 1.0
95
94
96
96
their easy recovery and reuse being their major advan-
tages.[
15]
Ph
Ph
6
7
8
2.0 1.5
4.0 2.5
12.0 0.5
Ph
Ph
In the present paper we report the scope of the use of a
naphthalene-supported polymer, as an alternative elec-
tron transfer catalyst to naphthalene, in the nickel-
catalyzed hydrogenation of the above-mentioned types
of organic substrates. In addition, both systems, NiCl2-
80[d] 93[d-f]
97[d] 98[d]
Ph
93[e]
96
Ph
Ph
9
2.0 12.0
Ph
Li-naphthalene (cat.) and NiCl -Li-(polymer-supported
2
naphthalene) (cat.), were also applied to the catalytic
hydrogenation of carbonyl compounds and imines
[
[
a]
b]
Method A: NiCl -Li-naphthalene, THF, rt.
2
Method B: NiCl -Li-(polymer-supported naphthalene),
2
(
Scheme 1).
THF, rt.
[
c]
Isolated yield of the reaction crude after filtration and
evaporation of solvents, unless otherwise is stated.
GLC yield.
Results and Discussion
[d]
e]
[
Reaction performed at À 78 8C ! rt.
Initially, we prepared a solid mixture composed of
nickel(II) chloride, lithium powder, and a catalytic
amount of naphthalene in the molar ratio 1:5:0.05,
[f]
8
1 and 86% yields were obtained when the reaction was
performed for 0.5 h at rt and 0 8C, respectively.
[
14]
respectively. Some preliminary experiments revealed
that a 20 mol % of nickel led to partial reduction of the
Concerning carbonyl compounds, a series of dialkyl,
substrates, and long reaction times were needed in some cycloalkyl, dicycloalkyl, and aromatic ketones could be
cases to complete the reaction, whereas ca. 40 mol % of hydrogenated to the corresponding secondary alcohols
nickel had an ideal behaviour in most of the starting (Table 2, entries 1 ± 5), although heating at 50 8C was
materials studied. The polymer-supported naphthalene required in two cases for improving the yields (Table 2,
was prepared by radical copolymerization of 2-vinyl- entries 2 and 4). Hydrogenation of benzaldehyde pro-
naphthalene and divinylbenzene (mixture of isomers) in ceeded with moderate yields (Table 2, entry 6), due to
[
15b, c]
a 19 to 1 molar ratio, respectively.
Thus, the reaction the fact that side reactions such as coupling compete
of the above mixture (40 mol % Ni) in the presence of with the main reduction pathway, whereas reduction of
naphthalene or polymer-supported naphthalene, with a the a,b-unsaturated ketone chalcone furnished the
variety of organic substrates in THF at room temper- corresponding saturated alcohol, no chemoselectivity
ature, and under an atmosphere of molecular hydrogen being observed (Table 2, entry 7). A ketimine and an
(
1 atm), led to the corresponding reduced products in aldimine were also reduced to the expected secondary
moderate to excellent yields (Tables 1 ± 4). amines, the latter being obtained in better isolated yields
This methodology was initially applied to the hydro- than the former (Table 2, entries 8 and 9, respectively).
genation of alkenes and alkynes (Table 1). Thus, alkyl This methodology allowed the hydrodehalogenation
chain, cyclic, conjugated, and functionalized alkenes, as reaction of various organic halides. Thus, alkyl, benzylic,
well as dienes gave the expected reduced products in and aromatic chlorides, as well as alkyl and aromatic
very high yields, independently of the electron transfer bromides, and an alkyl iodide were reduced to the
reagent used (Table 1, entries 1 ± 6). A representative corresponding hydrocarbons in moderate to excellent
group of alkynes including terminal, internal, and yields (Table 3, entries 1 ± 6). As regards aromatic com-
conjugated alkynes was also transformed into the pounds, it is worthy of note that the hydrogenation of
corresponding alkanes (Table 1, entries 7 ± 9).
anthracene under the above mentioned conditions
276
Adv. Synth. Catal. 2003, 345, 275 ± 279

The NiCl -Li-Arene (cat.) Combination as Reducing System, Part 9
FULL PAPERS
2
Table 2. Hydrogenation of carbonyl compounds and imines.
Table 3. Hydrogenation of organic halides and aromatic
compounds.
Yield [%][c]
t [h]
Entry
Starting Material
O
Product
OH
Yield [%][c]
A[a] B[b]
A[a]
B[b]
t [h]
Entry
Starting Material
Product
A[a] B[b]
A[a]
B[b]
1
2
3
12.0 12.0
2.0 2.0
2.0 2.0
64
71
Cl
8
2.0 2.5
2.0 2.0
68[d]
89
1
2
4
4
4
4
8
O
OH
Ph3CCl
NH2
Ph3CH
90
95
68[d] 65[d]
NH2
50[d]
98
3
4
12.0 2.0
2.0 2.0
98
94
O
OH
Cl
90
82
Br
14
14
O
OH
84[d] 72[d]
4
2.0 2.5
5
6
7
Ph
Br
I
2.0 2.0
2.0 2.0
2.0 12.0
Ph
84
86
93
57
O
OH
5
6
7
8
9
12.0 12.0
58
62
68[d,e] 65[d,e]
O
O
OH
H
12.0 12.0
12.0 12.0
63
67
60
62
8
12.0 12.0
98
99
N
H
OH
N
[
[
a]
b]
Method A: NiCl -Li-naphthalene, THF, rt.
Method B: NiCl -Li-(polymer-supported naphthalene),
THF, rt.
Isolated yield of the reaction crude after filtration and
evaporation of solvents, unless otherwise is stated.
Isolated yield after column chromatography (silica gel,
hexane or hexane/diethyl ether).
Approx. 10% yield of 9,10-dihydroanthracene was ob-
tained as by-product.
2
H
N
N
2
6.0 6.0
62
88
57
69
[
[
[
c]
d]
e]
N
12.0 12.0
N
H
[
[
a]
b]
Method A: NiCl -Li-naphthalene, THF, rt.
2
Method B: NiCl -Li-(polymer-supported naphthalene),
2
THF, rt.
[
[
c]
Isolated yield of the reaction crude after filtration and reaction of azoxy compounds and N-oxides, which
evaporation of solvents, unless otherwise is stated.
proceeded in moderate yields. Thus, starting from
azoxybenzene and 4,4'-dimethoxyazoxybenzene, the
d]
Reaction performed at 50 8C.
corresponding azobenzenes were obtained, which did
not suffer overreduction to hydrazines or anilines
furnished mainly 1,2,3,4-tetrahydroanthracene (Ta- (Table 4, entries 4 and 5). On the other hand, the N-
ble 3, entry 7), whereas using the combination NiCl ¥ oxides isoquinoline N-oxide and 4-phenylpyridine N-
2
[
13e]
2
H O-Li-DTBB (cat.),
2
9,10-dihydroanthracene was oxide were transformed into the expected deoxygenated
the only reaction product, thus indicating the different heteroaromatic compounds (Table 4, entries 6 and 7).
nature of the mechanisms involved.[16] Quinoline was
The nickel(0) prepared in the mentioned manner was
converted efficiently into 1,2,3,4-tetrahydroquinoline very finely divided, standing as a suspension even after
Table 3, entry 8). In general, similar yield pattern was several days, and showed to be highly reactive as any
(
observed for the naphthalene and polymer-supported attempt to support it failed, resulting in deactivation. In
naphthalene-catalyzed reactions, though 1-chlorode- general, the reactivity of this catalyst is comparable to
cane and 4-chloroaniline were better reduced using that of Raney nickel as regards the hydrogenation of
the polymer-supported naphthalene (Table 3, entries 1 alkenes,
and 3), whereas phenethyl iodide was better reduced which is also accomplished under soft reaction con-
with naphthalene (Table 3, entry 6). ditions. However, the reduction of aromatic com-
The hydrogenation of nitrogen-nitrogen bonds was pounds, alkyl chlorides, azoxy compounds, and
also achieved by any of the two methods in good yields. N-oxides by Raney nickel does not take place or harsh
Thus, phenylhydrazine, 1-methyl-1-phenylhydrazine, reaction conditions are required. Our catalyst also
and 1,2-diphenylhydrazine were reduced to the corre- showed to be superior to the nickel boride obtained
sponding anilines (Table 4, entries 1 ± 3). Finally, this with the NiCl -NaBH -DMF combination in the reduc-
[
17]
[17]
[18]
[19]
alkynes,
ketones,
and hydrazines,
[
17]
22]
[20]
[21]
[
2
4
[
7b]
methodology found application in the deoxygenation tion of alkyl chlorides, and milder reaction conditions
Adv. Synth. Catal. 2003, 345, 275 ± 279
277

FULL PAPERS
Francisco Alonso et al.
Table 4. Hydrogenation of hydrazines, azoxy compounds, lene are comparable, the easy recovery by filtration and
and N-oxides.
reusability of the latter makes it the reagent of choice to
t [h]
Yield [%][c]
carry out the herein reported transformations. In gen-
eral, these catalysts showed a reactivity superior to other
nickel catalysts, and compared to Raney nickel the
behaviour was similar in the reduction of alkenes,
alkynes, ketones and hydrazines, but better results
were obtained in the reduction of aromatic compounds,
alkyl chlorides, azoxy compounds and N-oxides.
Entry
Starting Material
NHNH2
Product
NH2
A[a] B[b]
A[a]
B[b]
1
1.0 1.0
1.0 1.0
88
89
NMeNH2
NMeH
2
3
98
90
93
93
H
N
NH2
12.0
N
12.0
H
O
4
N
N
N
4.0 12.0
N
N
N
58
61
51
O
N
5
6
7
MeO
OMe 12.0 12.0 MeO
N
OMe 57
Experimental Section
1.0 2.0
1.0 2.0
60
67
45
58
N
N
O
General Remarks and Starting Materials
N
O
N
For general information see Ref.[25] Anhydrous THF was
purchased from Acros (99.9%, stabilized). All starting materi-
als (except benzylideneaniline, azoxybenzene, 4,4'-dimethoxy-
azoxybenzene) were commercially available (Aldrich, Fluka)
of the best grade and were used without further purification.
For the preparation of benzylideneaniline, see Ref.[ Azoxy-
[
[
a]
b]
Method A: NiCl -Li-naphthalene, THF, rt.
2
Method B: NiCl -Li-(polymer-supported naphthalene),
2
THF, rt.
[
c]
Isolated yield of the reaction crude after filtration an
evaporation of solvents, unless otherwise is stated.
26]
benzene and 4,4'-dimethoxyazoxybenzene were prepared
according to Ref.[
13f]
For the preparation of the polymer-
supported naphthalene, see Ref.[
15b, c]
All reaction products
[
18]
were required in the hydrogenations of ketones and of
gave satisfactory physical, chromatographic, and spectroscopic
data by comparison with authentic samples which were
commercially available or previously prepared by us following
[
23]
aromatic and heteroaromatic compounds in compar-
ison with other nickel catalysts (H -Ni-EtOH, NiCl -Zn-
2
2
MeOH). Better behaviour of our catalyst was observed
in the reduction of carbon-carbon double and triple
bonds in comparison with the nickel-aluminium alloy,
the latter being used in large excess in a basic medium
and which only affects these functions when they are
[13]
other methodologies.
Preparation of the Catalytic Mixture
[
6a]
The catalytic mixture was composed of lithium powder
benzylic or conjugated with a carbonyl group. Finally,
and as an example of the reactivity of our catalyst, the
hydrogenation of anthracene to furnish 1,2,3,4-tetrahy-
droanthracene was carried out in 2 h at room temper-
(
5
175 mg, 25 mmol), anhydrous nickel(II) chloride (650 mg,
.0 mmol), and ground naphthalene (32 mg, 0.25 mmol) or
polymer-supported naphthalene (160 mg, 1.0 mmol), which
was always kept under nitrogen. Within several weeks, no
apparent loss of activity was observed for this catalytic mixture.
ature with NiCl -Li-naphthalene (Table 3, entry 7),
2
whereas hydrogenation over the widely used palladium
on charcoal required the use of tetralin as solvent in a
[
24]
sealed tube at 340 8C.
General Procedure for the Catalytic Hydrogenation
The catalytic mixture [(75 mg for naphthalene), (88 mg for
polymer-supported naphthalene), 40 mol % Ni] was intro-
duced into a Shlenck tube together with THF (3 mL) and the
starting material (1 mmol) under a hydrogen atmosphere
Conclusion
In this paper we have introduced the catalytic hydro-
(
1 atm) at room temperature. The reaction mixture, which was
genation of a series of organic compounds by using the initially green, changed to black indicating the formation of
system NiCl -Li-naphthalene (cat.). This combination, Ni(0). We observed that Ni(0) was generated faster when only
2
which generates a very reactive nickel, has been applied a small amount ( < 0.5 mL) of the total THF was first added,
followed by successive addition of the rest of THF and the
to the reduction of a variety of substrates such as
corresponding starting material. The course of the reaction was
alkenes, alkynes, carbonyl compounds, imines, organic
followed by GLC and/or TLC, and after the reaction time
halides, aromatic compounds, hydrazines, azoxy com-
specified in Tables 1 ± 4, the resulting black suspension was
pounds, and N-oxides, under very mild reaction con-
diluted with diethyl ether (20 mL) and filtered through a pad
containing silica gel and celite (ca. 3:1). After drying the filtrate
ditions (room temperature in most cases and atmos-
pheric pressure). Alternatively, a polymer-supported
naphthalene has been used as electron transfer agent
over anhydrous Na SO , it was evaporated (15 torr) and the
2
4
resulting residue analyzed without any purification or purified
instead of naphthalene. Although the results obtained by column chromatography (silica gel, hexane or hexane/
with naphthalene and the polymer-supported naphtha- diethyl ether) (see footnotes in Tables 1 ± 4).
278
Adv. Synth. Catal. 2003, 345, 275 ± 279

The NiCl -Li-Arene (cat.) Combination as Reducing System, Part 9
FULL PAPERS
2
Acknowledgements
[10] a) Y. Nakao, Chem. Lett. 1982, 997 ± 998; b) Y. Nakao, K.
Kaeriyama, Nippon Kagaku Kaishi 1984, 1005 ± 1010;
Chem. Abstr. 1984, 101, 44024; c) M. Sakai, Y. Minamida,
K. Sasaki, Y. Sakakibara, Nippon Kagaku Kaishi 1992,
412 ± 414; Chem. Abstr. 1992, 116, 255051; d) Y.-L. Jiang,
X.-Y. Wei, S.-P. Tang, L.-B. Yuang, Catal. Lett. 1995, 34,
This work was generously supported by the Direcci o¬ n General
de Ense nƒ anza Superior (DGES) of the Spanish Ministerio de
Educaci o¬ n y Cultura (MEC; grants no. PB97-0133 and
BQU2001-0538). We are very grateful to Dr. G. Radivoy for
providing samples of the starting materials azoxybenzene and
1
9 ± 22; e) D. Franquin, S. Monteverdi, S. Molina, M. M.
4,4'-dimethoxyazoxybenzene.
Bettahar, Y. Fort, J. Mater. Sci. 1999, 34, 4481 ± 4488.
11] a) K. J. Klabunde, S. C. Davis, H. Hattori, Y. Tanaka, J.
Catal. 1978, 54, 254 ± 268; b) K. J. Klabunde, T. O.
Murdock, J. Org. Chem. 1979, 44, 3901 ± 3908; c) D. H.
Ralston, K. J. Klabunde, Appl. Catal. 1982, 3, 13 ± 28;
d) K. J. Klabunde, Y. Tanaka, J. Mol. Catal. 1983, 21, 57 ±
[
References and Notes
14]
≤
For Part 8, see Ref.[
5
9.
[
1] For monographs, see: a) P. N. Rylander, Hydrogenation
Methods, Academic Press, London, 1985; b) P. A. Chal-
oner, M. A. Esteruelas, F. J o¬ o, L. A. Oro, Homogeneous
Hydrogenation, Kluwer Academic Publishers, Dor-
drecht, 1994.
[
12] a) L. A. Paquette, Encyclopedia of Reagents for Organic
Synthesis, Vol. 6, Wiley, Chichester, 1995, p. 4401; b) For
a recent application of Raney nickel, see, for instance:
A. F. Barrero, E. J. Alvarez-Manzaneda, R. Chahboun,
R. Meneses, J. L. Romera, Synlett 2001, 485 ± 488.
[2] a) S. Siegel, in Comprehensive Organic Synthesis, Vol. 8,
[
13] a) F. Alonso, M. Yus, Tetrahedron Lett. 1996, 37, 6925 ±
(Eds.: B. M. Trost, I. Fleming), Pergamon Press, Oxford,
6928; b) F. Alonso, M. Yus, Tetrahedron Lett. 1997, 38,
149 ± 152; c) F. Alonso, M. Yus, Tetrahedron 1998, 54,
1921 ± 1928; d) F. Alonso, G. Radivoy, M. Yus, Tetrahe-
1
991, pp. 417 ± 442; b) S. Nishimura, Handbook of
Heterogeneous Catalytic Hydrogenation for Organic
Synthesis, Wiley-Interscience, New York, 2001.
3] M. Hudlick y¬ , Reductions in Organic Chemistry, 2nd edn.,
ACS, Washington D. C., 1996.
4] W. F. Maier, K. Bergman, W. Bleicher, P. v. R. Schleyer,
Tetrahedron Lett. 1981, 22, 4227 ± 4230.
5] a) D. Savoia, E. Tagliavini, C. Trombini, A. Umani-
Ronchi, J. Org. Chem. 1981, 46, 5340 ± 5343; b) A.
F¸rstner, F. Hofer, H. Weidmann, Carbon 1991, 29,
dron 1999, 55, 4441 ± 4444; e) G. Radivoy, F. Alonso, M.
Yus, Tetrahedron 1999, 55, 14479 ± 14490; f) F. Alonso, G.
Radivoy, M. Yus, Tetrahedron 2000, 56, 8673 ± 8678; g) G.
Radivoy, F. Alonso, M. Yus, Synthesis 2001, 427 ± 430;
h) F. Alonso, M. Yus, J. Chem. Educ. 2001, 78, 1517 ±
[
[
[
1
518.
[
[
14] F. Alonso, M. Yus, Adv. Synth. Catal. 2001, 343, 188 ± 191.
15] a) T. R. van den Ancker, C. L. Raston, J. Organomet.
Chem. 1998, 550, 283 ± 300; b) C. G o¬ mez, S. Ruiz, M.
Yus, Tetrahedron Lett. 1998, 39, 1397 ± 1400; c) C. G o¬ -
mez, S. Ruiz, M. Yus, Tetrahedron 1999, 55, 7017 ± 7026;
d) M. Yus, C. G o¬ mez, P. Candela, Tetrahedron 2002, 58,
9
2
2
15 ± 919; c) B. H. Lipshutz, T. Tomioka, K. Sato, Synlett
001, 970 ± 973; d) B. H. Lipshutz, Adv. Synth. Catal.
001, 343, 313 ± 326; e) B. H. Lipshutz, S. Tasler, Adv.
Synth. Catal. 2001, 343, 327 ± 329.
[6] a) L. K. Keefer, G. L. Lunn, Chem. Rev. 1989, 89, 459 ±
6
207 ± 6210.
5
02; b) K. Kamata, Y. Tominaga, T. Akiyoshi, T.
Thiemann, S. Mataka, Heterocycles 1998, 48, 1663 ±
668, and references cited therein.
[
16] It is well known that the reduction of anthracene with
dissolving metals yields mainly 9,10-dihydroanthracene,
with partial destruction of aromaticity by reaction at the
less aromatic central ring. However, in the catalytic
hydrogenation of anthracene, the most thermodynami-
cally stable product, 1,2,3,4-tetrahydroanthracene, main-
taining the most p-delocalized aromatic system is
obtained (see Ref. , p. 67).
17] Ref. , Chapter 6.
18] Ref. , Chapter 13.
19] Ref. , p. 133.
20] Ref. , p. 81.
21] Ref. , p. 134.
22] Ref. , p. 131.
23] Ref. , pp. 72 ± 73.
24] Ref. , p. 66.
25] M. Yus, P. MartÌnez, D. Guijarro, Tetrahedron 2001, 57,
1
[
7] a) C. A. Brown, V. K. Ahuja, J. Chem. Soc. Chem.
Commun. 1973, 553 ± 554; b) B. Ganem, J. O. Osby,
Chem. Rev. 1986, 86, 763 ± 780; c) A. Nose, T. Kudo,
Chem. Pharm. Bull. 1990, 38, 1720 ± 1723; d) L. A.
Paquette, Encyclopedia of Reagents for Organic Syn-
thesis, Vol. 6, Wiley, Chichester, 1995, p. 3694; e) J. Choi,
N. M. Yoon, Synthesis 1996, 597 ± 599; f) J. Choi, N. M.
Yoon, Tetrahedron Lett. 1996, 37, 1057 ± 1060; g) N. M.
Yoon, K. B. Park, H. J. Lee, J. Choi, Tetrahedron Lett.
[3]
[3]
[
[
[
[
[
[
[
[
[
[3]
[3]
[3]
1
996, 37, 8527 ± 8528; h) I. Saxena, R. Borah, J. C. Sarma,
[3]
J. Chem. Soc. Perkin Trans. 1 2000, 503 ± 504.
[3]
[8] a) I. Motoyama, Bull. Chem. Soc. Jpn. 1960, 33, 232 ±
[3]
236; b) C. Petrier, J.-L. Luche, Tetrahedron Lett. 1987, 28,
2347 ± 2350; c) A. Nose, T. Kudo, Chem. Pharm. Bull.
1990, 38, 2097 ± 2101; d) M. Sakai, M.-S. Lee, K. Yama-
[3]
1
0119 ± 10124.
guchi, Y. Kawai, Bull. Chem. Soc. Jpn. 1992, 65, 1739 ±
740; e) A. Boruah, M. Baruah, D. Prajapati, J. S.
[
26] S. R. Sandler, W. Karo, Organic Functional Group
Preparations, Vol. 12-II, Academic Press, New York,
1
Sandhu, Synlett 1997, 1253 ± 1254.
1
971, p. 255.
[
9] a) J.-J. Brunet, P. Gallois, P. Caub e¡ re, J. Org. Chem. 1980,
4
5, 1937 ± 1945; b) J. J. Brunet, L. Mordenti, P. Caub e¡ re,
J. Org. Chem. 1981, 46, 1270 ± 1274.
Adv. Synth. Catal. 2003, 345, 275 ± 279
279