Bismuth(III) Chloride or Triflate-Catalyzed Dienophilic Activity of α-Ethylenic Aldehydes and Ketones

Full text of DOI:10.1021/jo970389h

4880
J . Org. Chem. 1997, 62, 4880-4882
Ta ble 1. Diels-Ald er Rea ction s Ca ta lyzed by Va r iou s
Bism u th (III) Ch lor id e or Tr ifla te-Ca ta lyzed
Dien op h ilic Activity of r-Eth ylen ic
Ald eh yd es a n d Keton es
Lew is Acid s
product
en-
catalyst
(mol %)
experimental
conditionsa
and
isomers
%
try reaction
yieldb
Bernard Garrigues, Ferdinand Gonzaga,
He´le`ne Robert, and J acques Dubac*
1
2
3
4
1 + 4
1 + 4
1 + 4
2 + 5
Sc(OTf)3 (10)
Bi(OTf)3 (1)
BiCl3 (10)
[TiCp*2(H2O)]- 25 °C; 13 h
(OTf)2
0 °C; 12 h
0 °C; 4 h
0 °C; 2 h
8 (89/11)d 96c
8 (93/7)d
8 (95/5)d
9
87
86
He´te´rochimie Fondamentale et Applique´e
(UPRES(A) 5069 CNRS), Universite´ Paul-Sabatier,
118 route de Narbonne, 31062 Toulouse Ce´dex, France
90c
5
6
7
8
9
10
11
12
13
2 + 5
2 + 5
2 + 5
2 + 6
2 + 6
2 + 6
3 + 7
3 + 7
3 + 7
Bi(OTf)3 (0.1) 25 °C; 14 h
9
9
9
10
10
85
82
82
60c
69
62
65e
88
61
Bi(OTf)3 (1)
BiCl3 (10)
Yb (fod)3 (1)
Bi (0Tf)3 (1)
BiCl3 (10)
SmI2 (5)
25 °C; 3 h
25 °C; 45 min
rt; 24 h
25 °C; 3 h
25 °C; 2 h
25 °C; 24 h
25 °C; 20 h
25 °C; 15 h
Received March 3, 1997
The weak shielding of the 4f shell (lanthanoid contrac-
tion) and the relativistic effects responsible for the
stabilization of 6s orbital (inert pair) confer to bismuth-
(III) a potential Lewis acidity, many complexes of which
have been reported.1 Curiously, the catalytic properties
of bismuth compounds, in particular those of Bi(III) as
Lewis acids, was developed only recently, although the
applications in organic synthesis of the organobismuth-
anes derived from Bi(V) are well known.2 Some recent
results in this area, including some from our laboratory,
concern the catalytic activity of Lewis acids derived from
Bi(III) for Mukaiyama-aldol3 and -Michael reactions,3a,b
halosilane activation,4 carbonyl-ene reaction,5 and acy-
lations,6 especially Friedel-Crafts acylation.6d,e Catalytic
properties of Bi(III) compounds are also known for other
reactions like the oxidation of alkenes,7 R-ketols,8 or
epoxides,9 and for the Knoevenagel condensation.10
This new attraction to bismuth is understandable.
Increasingly, catalysts and the processes using them
should be consistent with ecological standards. Bismuth
is the least toxic of the heavy elements.11 Biochemistry,12
toxicology,13 and environmental effects14 of bismuth
compounds have been recently reported. Bismuth com-
10
11 (90/10)e
11 (98/2)e
11 (97/3)e
Bi (OTf)3 (1)
BiCl3 (10)
a
Solvent CH2Cl2, except entry 8 (none); 1 M solutions, diene
and dienophile in equimolar amounts, except for entries 1-3 (diene
0.12 M, dienophile 0.4 M), and entry 11-13 (diene 1 M, dienophile
b
0.5 M). Yields in isolated product. c References: entries 1,15 4,16
d
8,17 11.18 endo/exo. e 1,4/1,3 isomers.
pounds are already used as industrial catalysts (manu-
facture of acrolein,7a acrylonitrile)7b and are employed in
pharmaceutical products.12
We present here the first examples of Diels-Alder
reactions catalyzed by bismuth(III) derivatives, bismuth
trichloride, or bismuth tris(triflate), in comparison with
some analogous Lewis acids well-known for their efficient
catalytic activity. The reactivity of standard dienes,
cyclopentadiene (1), 2,3-dimethylbutadiene (2), and iso-
prene (3) has been examined with four dienophiles,
methyl vinyl ketone (4), ethyl vinyl ketone (5), acrolein
(6), and methacrolein (7).
(1) Lange, K. C. H.; Klapo¨tke, T. M. In The Chemistry of Organic
Arsenic, Antimony and Bismuth Compounds; Patai, S., Ed.; J . Wiley:
New York, 1994; pp 315-366.
Resu lts a n d Discu ssion
In the case of the Diels-Alder cycloaddition between
1 and 4, scandium triflate (10% mol, 12 h, 96% yield) is
a better catalyst than ytterbium or yttrium triflates.15
Under the same conditions, 1% of Bi(OTf)3 gave an 87%
yield of 8 after 4 h (Table 1, entry 2), and 10% of BiCl3
gave the same yield after only 2 h (entry 3). The endo/
exo selectivity was a little higher (93/7 and 95/5, respec-
tively) than with Sc(OTf)3 (89/11).
The same two Bi-catalysts were compared with [TiCp*2-
(H2O)](OTf)2 in the case of the reaction between 2 and
516 (Table 1, entries 4-7). BiCl3 (10% mol) led to a
convenient result (45 min, 82% yield), and Bi(OTf)3
proved more efficient than the Ti-catalyst; 0.1% of Bi-
(OTf)3 and 2% of the Ti-catalyst gave a comparable result.
The bismuth catalysts were also found to be more
efficient than an ytterbium catalyst, Yb(fod)3. In the
(2) (a) Barton, D. H. R. Pure Appl. Chem. 1987, 59, 937. (b) Finet,
J . P. Chem. Rev. 1989, 89, 1487 and refences therein.
(3) (a) Wada, M.; Takeichi, E.; Matsumoto, T. Bull. Chem. Soc. J pn.
1991, 69, 990. (b) Le Roux, C.; Gaspard-Iloughmane, H.; Dubac, J .;
J aud, J .; Vignaux, P. J . Org. Chem. 1993, 58, 1835. (c) Le Roux, C.;
Gaspard-Iloughmane, H.; Dubac, J . Bull. Soc. Chim. Fr. 1993, 130,
832. (d) Le Roux, C.; Gaspard-Iloughmane, H.; Dubac, J . J . Org. Chem.
1994, 59, 2238. (e) Fontaine, E.; Baltas, M.; Escudier, J . M.; Gorrichon,
L. Mon. Chem. 1996, 127, 519.
(4) (a) Labrouille`re, M.; Le Roux, C.; Gaspard-Iloughmane, H;
Dubac, J . Synlett 1994, 723. (b) Labrouille`re, M.; Le Roux, C.; Oussaid,
A.; Gaspard-Iloughmane, H.; Dubac, J . Bull. Soc. Chim. Fr. 1995, 132,
522. (c) Montero, J . L.; Winum, J . Y.; Leydet, A.; Kamal, M.; Pavia, A.
A.; Roque, J . P. Carbohyd. Res. 1997, in press.
(5) Peidro, L.; Le Roux, C.; Laporterie, A.; Dubac, J . J . Organomet.
Chem. 1996, 521, 397.
(6) (a) Dubac, J .; Le Roux, C.; Gaspard-Iloughmane, H. In Progress
in Organosilicon Chemistry; Marciniec, B., Chojnowski, J ., Eds.; Gordon
and Breach: Basel, Switzerland, 1995; pp 325-343. (b) Le Roux, C.;
Mandrou, S.; Dubac, J . J . Org. Chem. 1996, 61, 3885. (c) Le Roux, C.;
Dubac, J . Organometallics 1996, 15, 4646. (d) Dubac, J .; Labrouille`re,
M.; Laporterie, A.; Desmurs, J . R. (Rhoˆne-Poulenc Chimie) 1996, Eur.
Pat. Appl. EP 698,593 (FR Appl. 94/10,523, 24 Aug 1994) (Chem. Abstr.
1996, 124, 316758y). (e) Desmurs, J . R.; Labrouille`re, M.; Dubac, J .;
Laporterie, A.; Gaspard, H.; Metz, F. In The Roots of Organic
Development; Desmurs, J . R., Ratton, S., Eds.; Elsevier: Amsterdam,
The Netherlands, 1996, pp 15-28.
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Industrial Chemistry; Gerhartz, W., Ed.; VCH: Weinheim (Germany),
1985; Vol. A1, pp 149-160. (b) Langvardt, P. W. In Ullman’s
Encyclopedia of Industrial Chemistry; Gerhartz,W., Ed.; VCH: Wein-
heim (Germany), 1985; Vol. A1, pp 177-184.
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Materials; Van Nostrand Reinhold: New York, 1989; pp 283, 284, 522,
and 523.
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Antimony and Bismuth Compounds; Patai, S., Ed.; J . Wiley: New York,
1994; pp 695-713.
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Antimony and Bismuth Compounds; Patai, S., Ed.; J . Wiley: New York,
1994; pp 715-723.
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Bismuth Compounds; Patai, S., Ed.; J . Wiley: New York, 1994; pp
725-759.
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Lett. 1995, 51, 4991.
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34, 2601. (b) Le Boisselier, V.; Dunach, E.; Postel, M. J . Organomet.
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(10) Prajapati, D.; Sandhu, J . S. Chem. Lett. 1992, 1945.
S0022-3263(97)00389-7 CCC: $14.00 © 1997 American Chemical Society

Notes
J . Org. Chem., Vol. 62, No. 14, 1997 4881
reaction between 2 and 6, Yb(fod)3 (10% mol) was used
without solvent at rt.17 In 1 M dichloromethane solution
with the same reagents, Bi(OTf)3 (1% mol) and BiCl3 (10%
mol) led to an equivalent yield after a shorter time (Table
1, entries 8-10).
The activity of bismuth catalysts was compared with
that of samarium(II) iodide for the reaction between 3
and 718 (Table 1, entries 11-13). In this reaction, the
use of a Lewis acid as catalyst strongly increase the 1,4-
regioselectivity.16 Although with SmI2 this regioselec-
tivity was already high (90%), with Bi-catalysis it in-
creased up to 97-98%. Even though BiCl3 appeared a
little less active than SmI2, Bi(OTf)3 was much more
efficient.
Finally, several other reactions between the dienes 1-3
and the dienophiles 4-7 have been carried out in
dichloromethane as solvent, in the presence of Bi(OTf)3
(1%), and led to the expected adducts in very good yields.
For example, 2-methylbicyclo[2.2.1]-5-heptene-2-carbox-
aldehyde (12) (endo/ exo ) 5/95) was formed in 96% yield
from 1 and 7 at 0 °C after 4 h, and 4-methyl-3-cyclohexen-
1-yl methyl ketone (13) was isolated in 90% yield (0 °C;
24 h) from 3 and 4.
identify three hydrates: Bi(OTf)3‚nH2O, n ) 9, 4, 2.25 For
temperatures higher than 80 °C, the dihydrate led a loss
of weight, but a beginning of decomposition appeared;
thus the pure anhydrous bismuth triflate has not been
isolated. Unlike triflates of transition elements,26 bis-
muth(III) triflate is not decomposed by water; therefore,
it is recoverable after aqueous workup, and reusable, as
we have shown (see Experimental Section).
Con clu sion
The use of Bi(III) salts as Lewis acid catalysts has
primarily concerned halides.3-6 This work extends their
field of application to [4 + 2] cycloadditions involving
R-carbonyl ethylenic dienophiles. In comparison with
other Sc-, Ti-, Sm-, or Yb-based efficient catalysts they
show higher reactivity and selectivity. Bismuth (III)
triflate, the strong catalytic activity of which we have also
observed in the Mukaiyama-aldol reaction,27 appears as
a useful competitor to transition metal triflates,26b both
because of its properties, i.e. catalytic power, water-stable
and reusable catalyst, and also low cost.
The extension of this work into other Lewis acid
mediated catalytic syntheses and the development of
chiral bismuth-based catalysts is currently in progress.
The soft Lewis acidity of Bi(III) compounds, especially
if the bismuth bears electronegative atoms,19 results in
low stability of carbonyl complexes.1 An intramolecular
complex in which the bismuth is coordinated to a car-
bonyl group has been recently isolated.20 Other experi-
ments have shown the Bi-acyl chloride interactions,6e that
lead to effectively catalyzed acylation reactions.6 An
electrophilic assistance has been put forward with alde-
hydes and ketones involved in the Bi-catalyzed Mu-
kaiyama-aldol, -Michael,3 and carbonyl-ene reactions.5
The activation of R-carbonyl ethylenic dienophiles like
4-7 is promoted by the Lewis acid coordination with the
carbonyl group.21 The results presented here show that
the two Bi(III) salts, BiCl3 and especially Bi(OTf)3, in
which the Lewis acidity of bismuth is amplified by three
strong electron-withdrawing groups, are strong, effective
Lewis acids. At the same time, these catalysts are
selective for [4 + 2] cycloadditions. We have not ob-
served, for the dienes or for the dienophiles, the polym-
erization frequently involved with strong Lewis acids.22
Unlike BiCl3, which is commercially available, the
synthesis and the use of Bi(OTf)3 requires some com-
ments. Bismuth(III) triflate is a known compound, which
has been prepared from bismuth trifluoroacetate or
bismuth oxide.23 These previous works have not reported
the existence of hydrates, whereas the crystalline struc-
Exp er im en ta l Section
Gen er a l. Dichloromethane was purified and dried using
known procedures.28 Bismuth(III) chloride and oxide, trifluo-
romethanesulfonic acid, dienes 2, 3, and dienophiles 4-7 were
purchased and used without further purification. BiCl3 was
preserved in a desiccator. Cyclopentadiene (1) was distilled from
its dimer just before use.
Typ ica l P r oced u r e. A solution of dienophile (16 mmol) in
8 mL of dichloromethane was introduced into a thermostated
100 mL double-walled flask, equipped with a septum inlet and
a magnetic stirbar and connected to a drying agent (calcium
chloride). The catalyst, bismuth triflate dihydrate (110 mg, 0.16
mmol) or bismuth chloride (504 mg, 1.6 mmol), was transferred
in a glovebag to the reaction flask, and the mixture was agitated
for 15 min. A solution of diene (16 mmol) in 8 mL of dichlo-
romethane was added dropwise, and the reaction was kept under
agitation during the time indicated in the table. The reaction
mixture was quenched with 10 mL of a saturated sodium
carbonate aqueous solution. The layers were separated, and the
aqueous layer was washed three times with 10 mL of dichlo-
romethane. The organic layers were combined, dried over
sodium sulfate, and concentrated under reduced pressure. The
crude product was analyzed according to previously described
1
methods;15-18 in particular, all compounds obtained had H NMR
spectra identical to those previously reported: 8,29 9,16 10,16 11.30
The isomers of adducts 8 and 11 were identified from products
obtained by thermal Diels-Alder addition (8: endo/ exo ) 62/
38;31 11: 1,4/1,3 isomers ) 70/30).16 Their ratios were deter-
mined by GC with n-alkanes as internal standards.
ture of a nonahydrate has been recently established.24
A
controlled dehydration between rt to 80 °C allowed us to
Bism u th (III) Tr iflu or om eth a n esu lfon a te. Bismuth tri-
flate was prepared from previous described procedure from
bismuth oxide or bismuth(III) acetate.23 The solid obtained was
heated at 60 °C under reduced pressure (0.1 mmHg) until a
constant weight was obtained. Elemental analysis was in
agreement with a mixture of hydrated forms of bismuth tri-
(17) Danishefsky, S.; Bernardski, M. Tetrahedron Lett. 1985, 26,
2507.
(18) Van de Weghe, P.; Collin, J . Tetrahedron Lett. 1994, 35, 2545.
(19) (a) Reese, A. L.; McMartin, K.; Miller, D.; Wickham, P. P. J .
Org. Chem. 1973, 38, 764. (b) Nakamura, E.; Shimada, J .; Kuwajima,
I. Organometallics 1985, 4, 646.
(20) Murafuji, T.; Mutoh, T.; Satoh, K.; Tsunenari, K. J . Organo-
metallics 1995, 14, 3848.
(21) (a) Fleming, I. Frontier Orbitals and Organic Chemical Reac-
tions; J . Wiley: New York, 1976; pp 161-165. (b) Houk, K. N. J . Am.
Chem. Soc. 1973, 95, 4092.
(22) (a) Brandup, J .; Immergut, E. H. In Polymer Handbook, 3rd
ed.; Wiley: New York, 1989; pp 295-363. (b) Liao, S.; Yu, S.; Chen,
Z.; Yu, D. J . Mol. Catal. 1992, 72, 209.
(23) (a) Singh, S.; Verma, A. R. D. Ind. J . Chem. 1983, 22A, 814. (b)
Niyogi, D. G.; Singh, S.; Gill, S.; Verma, R. D. J . Fluorine Chem. 1990,
48, 421.
(25) Loue¨r, M.; Le Roux, C.; Dubac, J . To be published.
(26) (a) Kowall, T.; Foglia, F.; Helm, L.; Merbach, A. E. Chem. Eur.
1996, 2, 285. (b) Kobayashi, S. Synlett 1994, 689; and refences therein.
(27) Le Roux, C.; Robert, H.; Laporterie, A.; Dubac, J . XIth Inter-
national Symposium on Organosilicon Chemistry, Universite´ Mont-
pellier II, 1-6 Sept 1996, Abstract OC5.
(28) Perrin, D. D.; Armarego, W. L. F. Purification of Laboratory
Chemicals; Pergamon Press: New York, 1992.
(29) Laszlo, P.; Schleyer, P. J . Am. Chem. Soc. 1963, 85, 2709.
(30) Van de Weghe, P. Thesis, Universite´ Paris XI, Orsay, 1995.
(31) Dinwiddie, J . G., J r.; McManus, S. P. J . Org. Chem. 1965, 30,
766.
(24) Frank, W.; Reiss, G. J .; Schneider, J . Angew. Chem., Int. Ed.
Engl. 1995, 34, 2416.

4882 J . Org. Chem., Vol. 62, No. 14, 1997
Notes
The catalytic power of these various hydrated forms of
bismuth triflate for the described reactions was comparable.
An aqueous suspension (40 mmol L-1) of bismuth triflate
dihydrate was agitated over 24 h at rt and filtered and the
resulting powder heated at 80 °C under reduced pressure. The
product obtained gave elemental analysis and NMR spectra (13
C
and 19F) identical to those of the starting material. Their
catalytic activity, compared for two reactions (Table 1, entries
2 and 12) is analogous.
The recovery of a substantial amount of bismuth triflate in a
5% molar catalytic experiment from 2 and 5 was carried out as
above, by filtration after reaction and aqueous workup. The
catalytic activity of the recovered bismuth triflate was un-
changed.
flate. Another heating between 60 °C and 80 °C under reduced
pressure of this crude powder led to a loss of weight, with
formation of a low hydrated form of bismuth triflate, Bi(OTf)3‚
2H2O. Anal. Calcd for C3H4BiF9O11S3: C, 5.20; H, 0.58; Bi,
30.19; F, 24.70; S, 13.90. Found: C, 5.25; H, 0.67; Bi, 30.23; F,
24.71; S, 13.92. 13C NMR (CD3COCD3): 120 ppm (from TMS),
quartet, 1J (13C/19F) ) 321 Hz; 19F NMR (CD3COCD3): 0.84 ppm
(from CF3COOH); IR (nujol), ν (cm-1): 3450-3550 (mb), 1230-
1290 (vs), 1180 (s), 1034 (s), 1028 (sh), 650 (sh), 643 (s).
Ack n ow led gm en t. We thank Professor Michael A.
Brook (McMaster University, Hamilton, Canada) for his
assistance in the preparation of the manuscript. Sup-
port of this work by the Centre National de la Recherche
Scientifique is gratefully acknowledged.
J O970389H