Rhodium-catalyzed carbonyl allylations by allylic alcohols with tin(II) chloride

Article abstract of DOI:10.1016/j.tetlet.2004.10.051

Rhodium complexes such as [RhCl(cod)]₂, [Rh(cod) ₂]BF₄, and [Rh(cod)(CH₃CN)₂]BF ₄ function as catalysts for carbonyl allylations by allylic alcohols with 1 equimolar amount of tin(II) chlor

Full text of DOI:10.1016/j.tetlet.2004.10.051

Tetrahedron
Letters
Tetrahedron Letters 45 (2004) 8969–8971
Rhodium-catalyzed carbonyl allylations by allylic alcohols
with tin(II) chloride
Yoshiro Masuyama,* Yusuke Kaneko and Yasuhiko Kurusu
Department of Chemistry, Sophia University, 7-1 Kioicho, Chiyoda-ku, Tokyo 102-8554, Japan
Received 7 September 2004; revised 7 October 2004; accepted 12 October 2004
Available online 22 October 2004
Abstract—Rhodium complexes such as [RhCl(cod)]2, [Rh(cod)2]BF4, and [Rh(cod)(CH3CN)2]BF4 function as catalysts for carbonyl
allylations by allylic alcohols with 1equimolar amount of tin(II) chloride to each allylic alcohol and aldehyde in THF at 50 °C to
produce the corresponding homoallylic alcohols.
Ó 2004 Elsevier Ltd. All rights reserved.
Palladium-catalyzed carbonyl allylation by allylic alcoh-
ols is a versatile allylating method in terms of (1) oper-
ation: allylic alcohols are stable to air, water, and
light; and (2) synthetic efficiency: usual starting materi-
als such as allylic halides, esters, and ethers in carbonyl
allylations are prepared from allylic alcohols.1 The pal-
ladium-catalyzed carbonyl allylation, which occurs via
umpolung (transmetallation) of p-allylpalladium com-
plexes,1 needs over two equimolar amounts of reducing
agents such as tin(II) chloride,2 triethylborane,3 and in-
dium(I) iodide,4 to allylic alcohols and/or carbonyl com-
pounds. Only complexes of group X elements have been
found to catalyze the carbonyl allylation via this kind of
umpolung. p-Allylrhodiums, derived from rhodium(I)
complexes with allylic halides, tosylates, and carbonates,
have been applied to reactions with nucleophiles.5 We
here report on a catalytic cycle of rhodium(I) for carbo-
nyl allylation by allylic alcohols with 1equimolar
amount of tin(II) chloride to the allylic alcohols, of
which actual allylating agents are probably not allyltin
compounds but allylrhodium complexes, in contrast to
palladium-catalyzed carbonyl allylation by allylic alcoh-
ols with tin(II) chloride.6
Catalytic activity of rhodium complexes and stoichio-
metry of tin(II) chloride were investigated for the allyla-
tion of benzaldehyde (1mmol) with 2-propenol (1,
1.5mmol) in THF (3mL) and H2O (0.1mL) in the pres-
ence of Rh cat. (0.02mmol) at 50°C for 48h under a
nitrogen atmosphere, which produced 1-phenyl-3-
buten-1-ol (2, R = Ph) (Eq. 1, Table 1). No allylation
occurs without either Rh catalysts or tin(II) chloride.
[RhCl(cod)]2 exhibited a higher catalytic activity than
[Rh(cod)2]BF4, [Rh(cod)(CH3CN)2]BF4, or RhCl-
(PPh3)3 (entries 1and 3–5). The character of ligands
such as PPh3, (8mol%, 84%), P(C6F5)3 (8mol%, 85%)
and dppe (4mol%, 84%) to the conditions of entry 7
does not affect the allylation to afford 2 (R = Ph). The
allylation without H2O was slow (entry 2).7 THF
(76%) is superior to other solvents such as acetonitrile
(61%) and 1,3-dimethylimidazolidin-2-one (38%) under
Table 1. Rhodium-catalyzed allylation of benzaldehyde with 1
Entry
Rh cat.
SnCl2 (mmol)
2 (R = Ph),
Yielda (%)
1[RhCl(cod)]
1.5
1.5
1.5
1.5
1.5
1.0
1.2
76 (95b)
44
43
2
2c
3
[RhCl(cod)]2
[Rh(cod)2]BF4
[Rh(cod)(MeCN)2]BF4
RhCl(PPh3)3
ð1Þ
4
30
14
5
6d
7d
[RhCl(cod)]2
[RhCl(cod)]2
70
90
a Isolated yields.9
Keywords: Nucleophilic addition; Carbonyl allylation; p-Allylrhodium;
Tin(II) chloride.
b After stirring for 72h.
*
Corresponding author. Tel.: +813 3238 3453; fax: +813 3238
3361; e-mail: y-masuya@sophia.ac.jp
c The allylation was carried out without H2O.
d The reaction was carried out with 1 (1mmol) in THF (1mL) for 11h.
0040-4039/$ - see front matter Ó 2004 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tetlet.2004.10.051

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Y. Masuyama et al. / Tetrahedron Letters 45(2004) 8969–8971
Table 2. Rhodium-catalyzed carbonyl allylation with 1
with slight anti-diastereoselectivity (entries 1–3 and 7–
9). Regioselectivity in the allylation of aliphatic alde-
hydes was low (entries 5, 6, and 12).
Entry
R
Time (h)
2, Yielda (%)
14-ClC
6H4
11
24
22
23
1
99
85
60
51
2
3
4
5
6
4-CH3OOCC6H4
4-CH3OC6H4
(E)-C6H5CH@CH
C6H13
7
8
88
85
c-C6H11
1
a Isolated yields.9
ð3Þ
the conditions of entry 1. The allylation was quite slow
at below 30°C and might be followed by dehydration in
refluxing THF.8 The allylation was presumed to proceed
with 1equimolar amount of tin(II) chloride to each 1
and benzaldehyde, unlike palladium-catalyzed carbonyl
allylations (entry 6).2 The balance between the yield and
the reaction rate determined optimal conditions; 1
(1.0mmol), benzaldehyde (1.0mmol), tin(II) chloride
(1.2mmol), and [RhCl(cod)]2 (0.02mmol) in THF
(1mL) and H2O (0.1mL) at 50 °C (entry 7). The allyla-
tion of various aldehydes with 1 was carried out under
the optimal conditions (Eq. 2). Some representative re-
sults are summarized in Table 2. Aromatic aldehydes
bearing an electron-withdrawing or electron-donating
group, aliphatic aldehydes and a,b-unsaturated cinnam-
aldehyde can be employed in the rhodium-catalyzed
allylation.
NMR observation (JEOL K-500) of the reaction of 2-
propen-1-ol (1, 1.0mmol) with tin(II) chloride
(1.2mmol) in the presence of a catalytic amount of
[RhCl(cod)]2 (2mol%) in THF-d8 (0.75mL) at 50°C
was carried out with neither any aldehydes nor any
H2O in a sealed tube. In distinction from palladium-cata-
lyzed reaction,2 the preparation of not 2-propenyltin
intermediate but propene was confirmed: 1H NMR
(500MHz)
d 1.68 (d, J = 6.5Hz, 3H), 4.89 (d,
J = 10Hz, 1H), 4.98 (d, J = 17Hz, 1H), 5.72–5.84 (m,
1H); 13C NMR (125MHz) d 19.5, 115.9, 134.0. The
preparation of propene without H2O suggested that an
allylhydridorhodium(III) complex could be prepared
from an initial p- or r-allylrhodium(III) complex such
as A that should directly cause carbonyl allylation in
the presence of aldehyde via the formation of r-allylrho-
dium(III) complex B coordinated by the aldehyde
(Scheme 1).10 The comparison of regioselectivity be-
tween 3 and 4 suggested that initial 1-methyl-p-allylrho-
dium(III) complex could be transformed into r-2-
butenylrhodium(III) complex by a coordination of alde-
hyde and then the 2-butenyl moiety could cause c-addi-
tion to the aldehyde. Since the reactivity of aliphatic
aldehydes to the carbonyl allylation is low, c-adducts
5b produced initially may react with excess aldehydes
to isomerize to a-adducts 5a via the formation of homo-
allyloxycarbenium ion intermediates.11
ð2Þ
Regioselectivity and diastereoselectivity in the rhodium-
catalyzed carbonyl allylation were investigated with (E)-
2-buten-1-ol (3) and 3-buten-2-ol (4) (Eq. 3). The repre-
sentative results are summarized in Table 3. Since the
reactivity of 4 is higher than that of 3, ease of p-coordi-
nation of C–C double bonds to rhodium may determine
the reaction rates. The allylation of aromatic aldehydes
with either 3 or 4 regioselectively occurred at the allylic
position substituted by a methyl group to produce 5b
In conclusion, we have established the Barbier-type rho-
dium(I)-catalyzed carbonyl allylation by allylic alcohols
with tin(II) chloride. Noteworthy features are that (1)
rhodium(I) complexes function as catalysts for carbonyl
Table 3. Rhodium-catalyzed carbonyl allylation with 3 and 4
Entry
Allylic alcohol
R
Time (h)
Yielda (%)
5a/5b (E/Z, syn/anti)b
1c
2c
3c
4c,d
5c
6c
7
3
3
3
3
3
3
4
4
4
4
4
4
C6H5
4-ClC6H4
39
39
39
29
35
63
20
20
16
2129
19
93
97
99
39
78
72
92
96
93
0/
6/94 (75/25, 42/58)
9/91(75/25, 34/66)
10/90 (71/29, 32/68)
0/ꢀ100 (—, 50/50)
33/67 (67/33, 62/38)
63/37 (77/23, 45/55)
5/95 (65/35, 38/62)
6/94 (65/35, 32/68)
8/92 (69/31, 29/71)
ꢀ100 (—, 50/50)
4-CH3OOCC6H4
(E)-C6H5CH@CH
C6H13
c-C6H11
C6H5
4-ClC6H4
8
9
4-CH3OOCC6H4
(E)-C6H5CH@CH
C6H13
10
11
12
95
6/94 (67/33, 70/30)
c-C6H11
218,133/2677/)73 (79/21
a Yields of mixtures of 5a and 5b.9
b The ratios were determined by 500MHz 1H NMR spectroscopy (JEOL K-500).
c The reaction was carried out with 3 (3.0mmol) and SnCl2 (3.0mmol) in THF (2mL).
d The reaction was carried out at 40°C.

Y. Masuyama et al. / Tetrahedron Letters 45(2004) 8969–8971
8971
RhI
OH
R
+
+
OH
SnCl2
Cl2Sn=O
Cl2Sn=O
H
RhIII
SnCl2OH
R
O
B
RhIII
SnCl2OH
RhIII
SnCl2OH
RCHO
A
Scheme 1. A plausible catalytic cycle.
5. For reactions of p-allylrhodium complexes derived from
allylic halides, tosylates, and carbonates, see: (a) Nixon, J.
F.; Poland, J. S.; Wilkins, B. J. Organomet. Chem. 1975,
92, 393; (b) Crease, A. E.; Das Gupta, B.; Johnson, M. D.;
Moorhouse, S. J. Chem. Soc., Dalton Trans. 1978, 1821;
(c) Fryzuk, M. D. Inorg. Chem. 1982, 21, 2134; (d)
Periana, R. A.; Bergman, R. G. J. Am. Chem. Soc. 1986,
108, 7346; (e) Tjaden, E. B.; Stryker, J. M. J. Am. Chem.
Soc. 1990, 112, 6420; (f) Chin, C. S.; Shin, S. Y.; Lee, C. J.
Chem. Soc., Dalton Trans. 1992, 1323; (g) Muraoka, T.;
Matsuda, I.; Itoh, K. J. Am. Chem. Soc. 2000, 122, 9552;
(h) Tsukada, N.; Sato, T.; Inoue, Y. Chem. Commun.
2001, 237.
allylations by allylic alcohols, (2) a p- or r-allylrho-
dium(III) stannate such as A seems to be an actual allyl-
ating agent though its direct detection by NMR
observation has ended in failure, in distinction from pal-
ladium-catalyzed allylation,2 (3) umpolung of p-allyl-
rhodium complex has been appreciated first, and (4)
the amount of tin(II) chloride used as a reducing agent
can be cut down by using rhodium(I) complexes as cata-
lysts instead of palladium complexes; 1equimolar
amount of tin(II) chloride to each allylic alcohol and
aldehyde displays a sufficient effect.
6. For rhodium-catalyzed enantioselective allylation of aryl-
aldehydes with allylstannane, see: Shi, M.; Lei, G.-X.;
Masaki, Y. Tetrahedron: Asymmetry 1999, 10, 2071.
7. For water-promoted rhodium-catalyzed reactions, see: (a)
Hayashi, T.; Takahashi, M.; Takaya, Y.; Ogasawara, M.
J. Am. Chem. Soc. 2002, 124, 5052; (b) Oi, S.; Honma, Y.;
Inoue, Y. Org. Lett. 2002, 4, 667, and references cited
therein.
Supplementary data
Supplementary data associated with this article can be
found, in the online version, at doi:10.1016/j.tetlet.
2004.10.051.
8. The reaction in refluxing THF produced a mixture of
nonpolar olefinic compounds of which no structures were
determined by instrumental analyses.
References and notes
1. For reviews containing carbonyl allylations by allylic
alcohols via umpolung of p-allylpalladium, see: (a)
Masuyama, Y. J. Synth. Org. Chem. Jpn. 1992, 50, 202;
(b) Masuyama, Y. In Advances in Metal–Organic Chem-
istry; Liebeskind, L. S., Ed.; JAI Press: Greenwich, CT,
1994; Vol. 3, p 255; (c) Tamaru, Y. In Perspectives in
Organopalladium Chemistry for the XXI Century; Tsuji, J.,
Ed.; Elsevier Science: Switzerland, 1999; p 215; (d)
Tamaru, Y. In Handbook of Organopalladium Chemistry
for Organic Synthesis; Negishi, E., Ed.; Wiley: New York,
2002; p 1917.
9. The structures were confirmed by the comparison of
spectroscopic values (IR and 1H NMR) with those of
authentic samples. See: (a) Ref. 2; (b) Ito, A.; Kishida, M.;
Kurusu, Y.; Masuyama, Y. J. Org. Chem. 2000, 65, 494.
10. 1H NMR observation with a stoichiometric amount of
[RhCl(cod)]2 under the same conditions as the observation
with a catalytic amount of [RhCl(cod)]2 was unsuccessful
in detecting an allylrhodium complex; at 25°C 2-propenol
(1) remained intact, while at 50°C no structure of products
other than propene was confirmed. For nucleophilic
addition of r-allylpalladium complexes to aldehydes, see:
Nakamura, H.; Iwama, H.; Yamamoto, Y. J. Am. Chem.
Soc. 1996, 118, 6641.
2. Takahara, J. P.; Masuyama, Y.; Kurusu, Y. J. Am. Chem.
Soc. 1992, 114, 2577.
3. Kimura, M.; Tomizawa, T.; Horino, Y.; Tanaka, S.;
Tamaru, Y. Tetrahedron Lett. 2000, 41, 3627.
11. Nokami, J.; Ohga, M.; Nakamoto, H.; Matsubara, T.;
Hussain, I.; Kataoka, K. J. Am. Chem. Soc. 2001, 123,
9168, The rhodium-catalyzed carbonyl allylation by 3 with
excess benzaldehyde also led to low c-regioselection; 3
(3mmol), tin(II) chloride (2mmol), benzaldehyde
(5mmol), THF (2mL), H2O (0.1mL), 50 °C, 48h, y 41%,
a/c = 34/66.
4. (a) Araki, S.; Kamei, T.; Hirashita, T.; Yamamura, H.;
Kawai, M. Org. Lett. 2000, 2, 847; (b) Hirashita, T.;
Kambe, S.; Araki, S. In Abstracts of 50th Symposium on
Organometallic Chemistry, Osaka, Japan; Kinki Chemical
Society: Japan, 2003; B103.