Quasi-nature catalysis: Conjugated addition of unsaturated carbonyl compounds with aryl and vinyltin reagents catalyzed by rhodium in air and water

Article abstract of DOI:10.1016/S0040-4039(01)00761-4

In air and water, trialkylphenyl- or trialkylvinylstannanes react with α,β-unsaturated esters and ketones to give the corresponding conjugated addition products in high yields in the presence of a rhodium catalyst.

Full text of DOI:10.1016/S0040-4039(01)00761-4

TETRAHEDRON
LETTERS
Pergamon
Tetrahedron Letters 42 (2001) 4459–4462
Quasi-nature catalysis: conjugated addition of unsaturated
carbonyl compounds with aryl and vinyltin reagents catalyzed by
rhodium in air and water
Sripathy Venkatraman, Yue Meng and Chao-Jun Li*
Department of Chemistry, Tulane University, New Orleans, LA 70118, USA
Received 8 February 2001; revised 3 May 2001; accepted 8 May 2001
Abstract—In air and water, trialkylphenyl- or trialkylvinylstannanes react with a,b-unsaturated esters and ketones to give the
corresponding conjugated addition products in high yields in the presence of a rhodium catalyst. © 2001 Published by Elsevier
Science Ltd.
Recently, we have been interested in developing transi-
tion-metal catalyzed carbonꢀcarbon bond formations
under the quasi-nature conditions of air and water.1
Such reactions have the advantages that (1) water-solu-
ble substrates such as carbohydrates can be used
directly without derivatization; (2) the aqueous catalyst
solution can be recycled easily, and (3) it is more
convenient for operations without the need for using an
inert gas atmosphere. A general requirement for per-
forming such reactions is that the reagent is air- and
water-stable.
On the other hand, the decreased reactivity and the
relatively higher stability towards air and water of these
reagents provides opportunities for performing reac-
tions in aqueous media, such as the allylation9 and
aldol-type condensation,10 and in air.11,12 An important
method for forming carbonꢀcarbon bonds is through
the conjugated addition of an organometallic reagent to
unsaturated carbonyl derivatives.13,14 Recently, we
reported that a,b-unsaturated esters and ketones react
with triphenylbismuth in aqueous media to give the
corresponding conjugated addition products under an
air atmosphere in the presence of a rhodium catalyst.15
While the reaction provides the desired product effec-
tively under the desired reaction conditions, it is not
economical as three phenyl rings are involved in the
triphenylbismuth reagents. Decreasing the amount of
triphenylbismuth lowered the yield of the desired
product considerably, which was in part due to the
formation of biphenyl. In addition, most bismuth com-
pounds are not readily available and are unstable
towards air and water, which limits the application of
the method. In order to overcome these problems,
herein we found that the readily available and stable
trialkylaryl- or trialkylvinyltin reagents 2 can be added
efficiently to unsaturated carbonyl compounds 1, gener-
ating the desired product 3 (upon the catalysis of
rhodium) in air and water (Eq. (1)).16
The use of tin and organotin compounds for synthetic
purposes has been growing in scope.2 This is due to
their relatively high stability and the ability of tailoring
chemo-, regio-, and stereoselectivities by combination
of these reagents with appropriate catalysts. Widely
recognized reactions attributed to the use of tin include
tributyltin hydride based radical chemistry,3 the Stille
reaction,4 allyltin chemistry,5 and tin enolate chem-
istry.6 More recently, transition-metal catalyzed car-
bonyl addition and conjugated additions involving
organotin compounds were studied by Oi7 and
Yamamoto8 under an inert gas atmosphere and anhy-
drous conditions. In particular, Oi7b and co-workers
reported a conjugated addition of arylstannanes to
unsaturated carbonyl compounds in dried THF, under
nitrogen, in a sealed Schlenk tube, catalyzed by
[Rh(COD)(CH3CN)2]BF4 at 60°C, and was quenched
by adding water.
R"
O
O
cat. Rh(I)
+
R"-SnR"'3
R
'
R
R
R'
H2O, 50°C
air atmosphere
3
1
2
(1)
* Corresponding author.
0040-4039/01/$ - see front matter © 2001 Published by Elsevier Science Ltd.
PII: S0040-4039(01)00761-4

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S. Venkatraman et al. / Tetrahedron Letters 42 (2001) 4459–4462
Table 1. Rhodium-catalyzed conjugated addition with aryl and vinylstannanes in aqueous media
Entry
Carbonyl Derivative (1) Stannane(2)
Yield (%)
57(2)
Product (3)
O
O
PhSnMe3
1
2
OEt
OEt
O
O
PhSnMe3
65(64)
67
OEt
OEt
O
O
PhSnMe3
3
4
OMe
OMe
O
O
PhSnMe3
76(77)
O
O
SnBu3
30
5
6
O
O
O
SnBu3
SnBu3
SnBu3
50
O
O
7
8
65
61
O
O
Me
Me
O
PhSnMe3
9
62(30)
CO2Et
CO2Et
CO2Et
CO2Et
PhSnMe3
PhSnMe3
10
75
O
O
11
77(91)
OMe
OMe
OMe
O
O
PhSnMe3
12
62
OMe
HO
HO
All reactions were carried out at 50°C and yields were isolated ones after column chromatography on
silica gel. Yields in parentheses are the ones reported by ref. 7b in anhydrous THF at 60°C under N2.

S. Venkatraman et al. / Tetrahedron Letters 42 (2001) 4459–4462
4461
Scheme 1. Tentative mechanism for the rhodium-catalyzed conjugated addition of aryl and vinylstannanes to unsaturated
carbonyl compounds in air and water.
When trimethylphenylstannane was stirred with ethyl
crotonate and a catalytic amount of a Rh2(COD)2Cl2 (5
mol%) at 50°C in water, a smooth reaction occurred to
give the conjugated product in 65% isolated yield.
Unlike the triphenylbismuth reaction, virtually no
biphenyl product was observed with the tin reagents.
Various conjugated carbonyl compounds were thus
examined under the same reaction conditions with
Rh2(COD)2Cl2 (Table 1). Simple ethyl acrylate also
reacted to give the desired product (entry 1), which is in
sharp contrast to the previous method7b in dried THF,
where essentially no product was obtained on a similar
substrate. In the triphenylbismuth reaction, only a very
small amount of the desired product was obtained.
Both ketones (linear and cyclic) and esters were effec-
tive as the electron-withdrawing functional groups.
Compounds bearing a hydroxyl group reacted as
expected and did not require any protection (entry 12).
Scheme 1 outlines a tentative mechanism in which
rhodium serves as a catalyst for the conjugated addition
of vinyl and aryltin reagents. In conclusion, a conve-
nient rhodium-catalyzed conjugated addition of a,b-
unsaturated carbonyl compounds was developed by
using trialkylvinyl- and trialkylphenylstannanes in air
and water. The scope, mechanism, and synthetic appli-
cations of this novel reaction are under investigation.
References
1. Li, C. J.; Chan, T. H. Organic Reactions in Aqueous
Media; John Wiley & Sons: New York, 1997. See also:
Li, C. J. Chem. Rev. 1993, 93, 2023; Li, C. J.; Chan, T. H.
Tetrahedron 1999, 55, 11149; Li, C. J. Tetrahedron 1996,
52, 5643.
2. (a) Davies, A. G. Organotin Chemistry; John Wiley &
Son: New York, 1997; (b) Omae, I. Organotin Chemistry;
Elsevier: New York, 1989; (c) Pereyre, M.; Quintard, J.
P.; Rahm, A. Tin in Organic Synthesis; Butterworths:
Stoneham, 1986; (d) Smith, P. J. Chemistry of Tin;
Blackie Academic & Professional: New York, 1997; (e)
Chemistry of Tin; Harrison, P. G., Ed.; Chapman and
Hall: New York, 1989; (f) Bristow, G. S. Aldrichim. Acta
1984, 17, 75.
3. (a) Curran, D. Synlett 1991, 107; (b) Giovannini, R.
Synlett 1995, 973; (c) Pereyre, M. Tetrahedron Lett. 1970,
3653; (d) Sato, T. Synlett 1995, 965; (e) Giese, B. Radicals
in Organic Synthesis: Formation of CarbonꢀCarbon
Bonds; Pergamon Press: Oxford, 1986; (f) Giese, B.
Angew. Chem., Int. Ed. Engl. 1983, 22, 622; (g) Porter, N.
J. Am. Chem. Soc. 1989, 111, 8311; (h) Hays, D. S.; Fu,
G. C. J. Am. Chem. Soc. 1995, 117, 7283.
4. (a) Stille, J. K. Pure Appl. Chem. 1985, 57, 1771; (b)
Mitchell, T. N. Synthesis 1992, 803.
5. (a) Thomas, E. J. Main Group Met. Chem. 1996, 19, 307;
(b) Yamamoto, Y. Aldrichim. Acta 1987, 20, 45; (c)
Tagliavini, G. Rev. Silicon, Germanium, Tin Lead Compd.
1985, 8, 237.
6. (a) Groger, H.; Vogl, E. M.; Shibasaki, M. Chem. Eur. J.
1998, 4, 1137; (b) Mukaiyama, T.; Kobayashi, S. Org.
React. (NY) 1994, 46, 1; (c) Shibata, I.; Baba, A. Org.
Prep. Proc. Int. 1994, 26, 85.
7. (a) Oi, S.; Moro, M.; Ono, S.; Inoue, Y. Chem. Lett.
1998, 83; (b) Oi, S.; Moro, M.; Inoue, Y. Chem. Commun.
1997, 1621.
8. Nakamura, H.; Iwama, H.; Yamamoto, Y. J. Am. Chem.
Soc. 1996, 118, 6641.
A typical experimental procedure is as follows: A mix-
ture of cyclohex-2-en-1-one (100 mg, 1.04 mmol),
trimethylphenylstannane (275 mg, 1.14 mmol), and
bis(1,4-cyclooctadiene)dirhodium dichloride (25 mg, 5%
mol) in 4 mL of water was capped and stirred at 50°C
(oil bath temperature) for 12 h. Upon cooling, the
reaction mixture was extracted with ether. The com-
bined organic fractions were dried over MgSO4 and
concentrated. The residue was purified by column chro-
matography on silica gel (eluent: hexane/ethyl acetate=
20:1–10:1) to give 3-phenylcyclohexanone (138 mg, 76%
yield).
9. (a) Nokami, J.; Otera, J.; Sudo, T.; Okawara, R.
Organometallics 1983, 2, 191; (b) Uneyama, K.; Kamaki,
N.; Moriya, A.; Torii, S. J. Org. Chem. 1985, 50, 5396; (c)
Petrier, C.; Einhorn, J.; Luche, J. L. Tetrahedron Lett.
1985, 26, 1449.
10. Chan, T. H.; Li, C. J.; Wei, Z. Y. J. Chem. Soc., Chem.
Commun. 1990, 505.
11. Meng, Y.; Li, C. J. J. Am. Chem. Soc. 2000, 120, 9538.
Acknowledgements
We are grateful to NSF (CAREER Award), the NSF-
EPA joint program for a sustainable environment, and
Louisiana Board of Regents for partial support of our
research.
.

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S. Venkatraman et al. / Tetrahedron Letters 42 (2001) 4459–4462
12. For other water and air tolerant transition-metal catalyzed
reactions reported from this group, see: Venkatraman, S.;
Li, C. J. Org. Lett. 1999, 1, 1133; Venkatraman, S.; Li, C.
J. Tetrahedron Lett. 2000, 41, 4831; Li, C. J.; Meng, Y.;
Yi, X. H.; Ma, J. H.; Chan, T. H. J. Org. Chem. 1998, 63,
7498; Wang, D.; Chen, D. L.; Haberman, J. X.; Li, C. J.
Tetrahedron 1998, 54, 5129; Li, C. J.; Meng, Y.; Yi, X. H.;
Chan, T. H. J. Org. Chem. 1997, 62, 8632; Li, C. J.; Wang,
D.; Chen, D. L. J. Am. Chem. Soc. 1995, 117, 12867.
13. Taylor, R. J. K. Synthesis 1985, 364.
14. For reviews, see: Posner, G. H. An Introduction to Synthesis
using Organocopper Reagents; Wiley: New York, 1980;
Lipshutz, B. H. In Organometallics in Synthesis; Schlosser,
M., Ed.; Wiley: New York, 1994; p. 283. For other
examples of transition-metal catalyzed conjugated addi-
tions, see: Cho, C. S.; Motofusa, S.; Ohe, K.; Uemura, S.;
Shim, S. C. J. Org. Chem. 1995, 60, 883; Ikeda, S.; Cui,
D. M.; Sato, Y. J. Am. Chem. Soc. 1999, 121, 4712;
Sawamura, M.; Hamashima, H.; Ito, Y. J. Am. Chem. Soc.
1992, 114, 8295; Trost, B. M. Angew. Chem., Int. Ed. Engl.
1995, 34, 259; Ohe, T.; Wakita, T.; Motofusa, S.; Cho, C.
S.; Ohe, K.; Uemura, S. Bull. Chem. Soc. Jpn. 2000, 73,
2149.
15. Venkatraman, S.; Li, C. J. Tetrahedron Lett. 2001, 42, 781.
16. Recently, rhodium-catalyzed conjugated additions on a,b-
unsaturated esters with arylboronic acids were reported in
aqueous dioxane under an inert gas atmosphere. Sakuma,
S.; Sakai, M.; Itooka, R.; Miyaura, N. J. Org. Chem. 2000,
65, 5951; Hayashi, T.; Senda, T.; Ogasawara, M. J. Am.
Chem. Soc. 2000, 122, 10716 and references cited therein.
.