Rhodium-catalyzed allylation of styrenes with allyl tosylate

Article abstract of DOI:10.1039/b007880h

Rhodium-catalyzed allylation of styrene with allyl tosylate gave 1-phenylpenta-1,4-diene, and various styrene derivatives were also allylated yielding 1,4-dienes or 1,5-dienes.

Full text of DOI:10.1039/b007880h

Rhodium-catalyzed allylation of styrenes with allyl tosylate
Naofumi Tsukada,* Tetsuo Sato and Yoshio Inoue
Department of Materials Chemistry, Graduate School of Engineering, Tohoku University, Sendai 980-8579, Japan.
E-mail: tsukada@aporg.che.tohoku.ac.jp
Received (in Cambridge, UK) 28th September 2000, Accepted 20th December 2000
First published as an Advance Article on the web 18th January 2001
Rhodium-catalyzed allylation of styrene with allyl tosylate
gave 1-phenylpenta-1,4-diene, and various styrene deriva-
tives were also allylated yielding 1,4-dienes or 1,5-dienes.
Table 1 Rhodium-catalyzed allylation of styrene derivatives with allyl
tosylatea
The palladium-catalyzed arylation of alkenes, the Heck reac-
tion, has proven to be a versatile method for the formation of
1
carbon–carbon bonds. In contrast, the analogous reaction of
alkenes with allyl compounds is far more limited in its
application, except for intramolecular metallo-ene reactions,2
and remains a challenge in organic synthesis. Although a few
examples of the transition metal-catalyzed allylation of alkenes
have been reported,3 to our knowledge, a reaction yielding
simple allylation products, i.e. 1,4-dienes, is yet to be
discovered. For example, strained alkenes such as norbornene†
react with allyl compounds in the presence of various transition
–5
metal catalysts, however, these reactions do not afford
3
1
,4-dienes because of stereochemical problems. The palla-
dium-catalyzed allylation of activated olefins with allyl-
stannane and allyl chloride gives not mono-allylation products,
but double allylation products selectively.4 Mitsudo et al.
reported ruthenium-catalyzed reactions of allyl carbonates with
N,N-dimethylacrylamide, in which only 1,3-dienes were ob-
tained in moderate yields.5 Herein we wish to report the
rhodium-catalyzed simple allylation of styrene derivatives with
allyl tosylate.6
When styrene (1a) was treated with two equivalents of allyl
tosylate in the presence of
Rh(nbd)(CH CN) ]PF (nbd = norbornadiene‡) in dioxane at
0 °C, 1-phenylpenta-1,4-diene 2a was produced in 17% yield
eqn. (1)). Allyl tosylate and styrene were not recovered, and no
a
catalytic amount of
[
3
2
6
4
(
(1)
other product was identified. No allylation product was formed
using typical allylating agents such as allyl acetate, allyl
carbonate and allyl iodide. Palladium complexes such as
3 4 2 3 3 3 4 4 2
Pd(PPh ) , Pd (dba) ·CHCl , [Pd(CH CN) ](BF ) , or various
Lewis acids were ineffective as catalysts for the allylation
reaction. The yield of 2a was improved up to 34% by the
addition of allyl iodide (40 mol%). In contrast, the addition of
other allylic compounds such as allyl bromide, allyl acetate, or
allyl phosphate, decreased the yield slightly. Other organic and
inorganic iodides like n-propyl iodide, tert-butyl iodide and
potassium iodide also hindered the reaction to some extent.
Furthermore, amounts of allyl iodide less than or exceeding 40
mol% were less effective on the yield of 2a.
Although satisfactory yield was not obtained in the allylation
of non-substituted styrene, the reactions of several substituted
styrenes gave allylation products in higher yields as illustrated
in Table 1. The allylation of 1,1-diphenylethylene 1b afforded
2b in 51% yield (run 1). The yield of 2b increased to 74% with
the addition of allyl iodide (run 2). The electron-rich alkene 1c
was so reactive that the product 2c was obtained in 80% yield
DOI: 10.1039/b007880h
Chem. Commun., 2001, 237–238
This journal is © The Royal Society of Chemistry 2001
237

rhodium, and with the insertion of 1g to A or B, the rhodium
organometallic intermediate C is afforded. In the reaction using
allyl acetate or allyl iodide as the allylating agent, the
coordination of acetate or iodide ions to rhodium is so strong
that the insertion of an alkene does not take place. Subsequent
1
b-hydrogen H elimination in C affords 1,5-diene 3. Since free
2
rotation around the C(H )–C(Ph) bond in C is possible, alternate
2
syn-b-hydrogen H elimination in D also occurs, providing
1
,4-diene 2g. The 1,5-dienes were obtained selectively in
reactions where free rotation around the C–C bond is not
possible in the intermediate corresponding to C (runs 13–15).
As the formation of 2j and 2k is not consistent with the
mechanism shown in Scheme 1, the existence of another
mechanism, e.g. a Friedel–Crafts type reaction, cannot be ruled
out, although typical Lewis acids are ineffective in the present
allylation reaction. Further investigation of the reaction mecha-
nism and the application to other alkenes are in progress.
Scheme 1
(
1
run 3). The reaction of 1-(p-methoxyphenyl)-1-phenylethylene
d also gave 2d in high yield (run 4), whereas the ortho-
substituted isomer 1e was less reactive (run 5). By contrast, the
reaction of the electron-poor alkene 1f afforded 2f in lower yield
(
26%, run 6). The a-alkyl-substituted styrenes 1g and 1h also
Notes and references
reacted with allyl tosylate. In the reaction of 1g the total yield of
the allylated products was high (82%, run 7), although 1,5-diene
3
†
‡
The IUPAC name for norbornene is bicyclo[2.2.1]hept-2-ene.
The IUPAC name for norbornadiene is bicyclo[2.2.1]hepta-2,5-diene.
was yielded in addition to 2g. The reaction of 1h gave the
monoallylated product 2h and the diallylated 4, generated by the
allylation of a 1,5-diene product corresponding to 3 (run 8).
When allyl iodide was added to the reaction of 1h, diallylated
products 4 and 5 were obtained in 63% yield (run 9). In contrast
to the high reactivity of a-substituted styrenes, b-substituted
styrenes were less reactive. The reactions of Z-stilbene, E-
stilbene and b-methylstyrene did not give any allylated
products. The electron-rich b-substituted styrene derivative 1i
barely reacted with allyl tosylate affording 2i in only 16% yield
1
Reviews: (a) R. F. Heck, Palladium Reagents in Organic Synthesis,
Academic Press: London, 1985; (b) R. F. Heck, in Comprehensive
Organic Synthesis, ed. B. M. Trost and I. Fleming, Pergamon Press:
Oxford, 1991, Vol. 4, p. 833; (c) W. Cabri and I. Candiani, Acc. Chem.
Res., 1995, 28, 2; (d) J. Tsuji, in Palladium Reagents and Catalysts,
Innovations in Organic Synthesis, Wiley: London, 1995, p. 125; (e) A. de
Meijere and F. Meyer, Angew. Chem., Int. Ed. Engl., 1994, 33, 2379.
Reviews: (a) W. Oppolzer, in Comprehensive Organic Synthesis, ed.
B. M. Trost and I. Fleming, Pergamon Press: Oxford, 1991, Vol. 5,
chapter 8.3; (b) W. Oppolzer, in Comprehensive Organometallic
Chemistry II, ed. E. W. Abel, F. G. A. Stone and G. Wilkinson, Pergamon
Press, Oxford, 1995, Vol. 12, chapter 1.2.
2
(
run 10). Indene 1j was also allylated at the C-2 carbon (runs
1). The allylation reactions of the phenyl-substituted cyclic
alkenes 1l–n were also investigated. All the reactions gave only
1
3 (a) M. Catellani, G. P. Chiusoli, E. Dradi and G. Salerno, J. Organomet.
Chem., 1979, 177, C29–31; (b) E. Amari, M. Catellani and G. P.
Chiusoli, J. Organomet. Chem., 1985, 285, 383; (c) K. Fugami, T.
Enokido, K. Kawata, M. Kameyama and M. Kosugi, Main Group Met.
Chem., 1999, 22, 511; (d) Y. Morisaki, T. Kondo and T. Mitsudo, Org.
Lett., 2000, 2, 949; (e) N. Tsukada, T. Sato and Y. Inoue, Tetrahedron
Lett., 2000, 41, 4181.
1
,5-dienes 2l–n in satisfactory yields, in which no 1,4-diene was
observed (runs 13–15).
Although little mechanistic information has been obtained for
the Rh-catalyzed allylation of styrenes, we believe that the
reaction proceeds via a mechanism similar to that of the
palladium-catalyzed Heck arylation reaction. The likely inter-
mediates for the allylation of 1g are illustrated in Scheme 1. The
4
H. Nakamura, J.-G. Shim and Y. Yamamoto, J. Am. Chem. Soc., 1997,
19, 8113.
1
oxidative
Rh(nbd)(CH
complex B, in which tosylate anions weakly coordinate to
addition
of
allyl
tosylate
with
5
T. Mitsudo, S.-W. Zhang, T. Kondo and Y. Watanabe, Tetrahedron Lett.,
1992, 33, 341.
[
3
CN) ]PF
2
6
gives the dicationic complex A or the
6 N. Tsukada, S. Sugawara and Y. Inoue, Org. Lett., 2000, 2, 655.
238
Chem. Commun., 2001, 237–238