Selective allylation of arenethiols using water-soluble palladium complex catalyst in recyclable water/hexane biphasic media

Article abstract of DOI:10.1246/cl.2005.246

Allylation of arenethiols by allylic alcohol with sterically hindered carbon of the allylic moiety is smoothly catalyzed by Pd(OAc)₂/TPPTS in biphasic water/hexane media under ambient conditions. The catalyst water layer can be repeatedly reuse

Full text of DOI:10.1246/cl.2005.246

246
Chemistry Letters Vol.34, No.2 (2005)
Selective Allylation of Arenethiols Using Water-soluble Palladium Complex Catalyst
in Recyclable Water/Hexane Biphasic Media
Nobuyuki Komine, Akari Sako, Shin-ya Hirahara, Masafumi Hirano, and Sanshiro Komiyaꢀ
Department of Applied Chemistry, Graduate School of Engineering, Tokyo University of Agriculture and Technology,
2-24-16 Nakacho, Koganei, Tokyo 184-8588
(Received November 19, 2004; CL-041398)
Table 1. Allylation of thiol using allyl alcohol by palladium
catalysta
Allylation of arenethiols by allylic alcohol with sterically
hindered carbon of the allylic moiety is smoothly catalyzed by
Pd(OAc)2/TPPTS in biphasic water/hexane media under ambi-
ent conditions. The catalyst water layer can be repeatedly reused
without catalytic activity loss.
Time Yield
/h
Entry
Catalyst
Solvent
/%
1
2
3
4
5
6
7
8
9
Pd(OAc)2/4TPPTS water/hexaneb
Pd(OAc)2/4TPPTS water/benzeneb
Pd(OAc)2/4TPPTS water/AcOEtb
Pd(OAc)2/4TPPTS water
Pd(OAc)2/4TPPTS dimethyl sulfoxide
Pd(OAc)2/4TPPTS methanol
2
2
2
3
6
6
6
6
6
6
2
95
52
64
25
0
0
0
0
0
Aqueous/organic biphasic catalyses attract growing inter-
ests in relation to environmentally friendly chemical processes,
due to easy separation of products and catalysts, multiple use
of catalysts, and reduction of organic solvents.1 We recently re-
ported the synthesis and some organometallic reactions of water-
soluble alkyltransition metal complexes2 and biphasic carbonyl-
selective hydrogenation of unsaturated carbonyl compounds.3
Allylation reactions represented as Tsuji–Trost reaction are re-
garded as one of the most important chemical processes in or-
ganic synthesis.4 Among them, Pd-catalyzed allylation of thiols
are still exceptionally rare,5 probably because of possible cata-
lyst poisoning by sulfur coordination, though Ru-catalyzed ally-
lation was recently reported by Mitsudo.6 We now report novel
allylation of arenethiols with allylic alcohols catalyzed by
Pd(OAc)2/TPPTS in aqueous/organic biphasic media.7,8 Suc-
cess in using allylic alcohols as allyl source is also an important
value added in this reaction,6,9 since allylic alcohols are easily
accessible and believed to be a poor inlet to ꢀ3-allylpalladium
intermediates in comparison with other allyl sources such as al-
lylic halides, carbonates, esters, and ethers.
Pd(OAc)2/4PPh3
Pd(OAc)2/4PPh3
benzene
acetonitrile
benzene
acetonitrile
water/hexaneb
c
Pd(PPh3)4
Pd(PPh3)4
Pd(TPPTS)3
c
10
11
0
96
c
aReaction conditions: Pd(OAc)2 (0.02 mmol), phosphine ligand
(0.08 mmol), allyl alcohol (1.0 mmol), benzenethiol (1.0 mmol),
solvent = 8 mL, room temperature. bsolvent = water 4.0 mL,
c
organic solvent 4.0 mL. Pd(0) complex (0.02 mmol).
proceeded with Pd(OAc)2/TPPTS catalyst in biphasic water/
hexane media (Tables 2 and 3). Table 2 shows the results of
allylation of arenethiol derivatives by allyl alcohol. Electron-
donating substituent at para-position and ortho-substitutents in
arenethiol discouraged the catalytic activity (Entries 2–4).
One notable fact observed in Table 3 is that more sterically
hindered side of the allylic moiety is substituted by mercapto
Treatment of benzenethiol with allyl alcohol in the presence
of 2 mol% Pd(OAc)2 and 4 equiv. of TPPTS [TPPTS =
P{C6H4(SO3Na)-3}3] at room temperature for 2 h under nitro-
gen atmosphere in biphasic water/hexane media gave allyl
phenyl sulfide quantitatively (Eq 1).
Table 2. Allylation of several arenethiol with allyl alcohola
Pd(OAc)2 / 5TPPTS
(2.0 mol%)
OH
SAr
+ ArSH
rt, water/hexane
Pd(OAc)2 / 4TPPTS
(2.0 mol%)
ArSH
Entry
1
Time/h
2
Conv./%
Yield/%
96
SPh
95%
(1)
OH
+
PhSH
rt, 2 h
water/hexane
SH
100
Catalytic activity of several palladium catalytic systems was ex-
amined in the reaction of benzenethiol with allyl alcohol
(Table 1). Water/benzene or AcOEt system or only water can al-
so be used, but the yield of allyl phenyl sulfide decreased under
the comparable conditions (Entries 2–4). No allylation product
was obtained when the reaction was carried out in only organic
solvents such as dimethyl sulfoxide, methanol, benzene and ace-
tonitrile in the presence of Pd(OAc)2/4 TPPTS or the corre-
sponding palladium catalysts with triphenylphosphine ligand
(Pd(OAc)2/4 PPh3) (Entries 5–10). It is interesting to note that
use of biphasic water/hexane media is critically important for
this success. Pd(TPPTS)3 also shows catalytic activity for allyla-
tion of benzenethiol in biphasic water/hexane media (Entry 11).
Allylation using several allylic alcohols and arenethiols also
2
5
42
39
94
2
3
SH
100
2
20
58
14
41
SH
24
2
6
52
92
45
91
MeO
F
SH
4
5
SH
2
100
91
aReaction conditions: Pd(OAc)2 (0.02 mmol), TPPTS (0.10 mmol),
allyl alcohol (1.0 mmol), thiol (1.0 mmol), solvent = water 4.0 mL,
hexane 4.0 mL, room temperature.
Copyright Ó 2005 The Chemical Society of Japan

Chemistry Letters Vol.34, No.2 (2005)
247
Table 3. Allylation of benzenethiol with several allylic
alcoholsa
In all catalytic allylations, the products were easily separat-
ed from the catalyst by simple decantation of the organic layer.
Since the catalyst remained in the water layer, the allylation can
be run again by simply adding the hexane solution of the reac-
tants (Table 4). Four runs were performed without loss of cata-
lytic activity for the reaction of benzenethiol with allyl alcohol,
by using the recycled water layer containing the water-soluble
catalyst.
Entry Allylic alcohol Time/h Conv./%
Product (yield/%)
OH
SPh
SPh
(95)
1
2
2
3
100
45
SPh
OH
(E/Z = 95/5)
(18)
(24)
(E/Z = 94/6)
This work was partially supported by New Energy and
Industrial Technology Development Organization (NEDO) and
Japan Chemical Innovation Institute (JCII).
(32)
(E/Z = 88/12)
(45)
(E/Z = 81/19)
(29)
(E/Z = 64/36)
(38)
(40)
(56)
(50)
(59)
3
4
5
6
5
79
100
83
9
3
5
OH
References and Notes
1
a) ‘‘Aqueous-Phase Organometallic Catalysis, Concepts
and Applications,’’ ed. by B. Cornils and W. A. Herrmann,
Wiley-VCH, Weinheim (1998) and references cited therein. b)
‘‘Applied Homogeneous Catalysis with Organometllic
Compounds,’’ ed. by B. Cornils and W. A. Herrmann, VCH,
Weinheim (1996), Vols. 1 and 2.
98
(E/Z = 65/35)
OH
SPh
SPh
7
8
24
24
100
100
(32)
(35)
(61)
(65)
2
a) S. Komiya, M. Ikuine, N. Komine, and M. Hirano, Chem.
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OH
3
4
5
A. Fukuoka, W. Kosugi, F. Morishita, M. Hirano, L. McCaffrey,
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J. Tsuji, ‘‘Palladium Reagents and Catalysts,’’ Wiley, Chichester
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ˆ
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aReaction conditions: Pd(OAc)2 (0.02 mmol), TPPTS (0.10 mmol),
allylic alcohol (1.0 mmol), benzenethiol (1.0 mmol), solvent =
water 4.0 mL, hexane 4.0 mL, room temperature.
group regardless of the starting allylic alcohols.8 E=Z ratio of the
products in the reactions using crotyl alcohol and its regioisom-
er, 1-methylallyl alcohol was slightly different. In addition sub-
stituents at the 3-position of the allylic alcohol significantly sup-
pressed the reaction rate (Entries 2–6). One possible mechanism
is initial coordination of allylic alcohol via C=C double bond,
followed by protonation of OH with thiol to give an ꢀ1-allyl)pal-
ladium(II) intermediate having substituents at the terminal sp2
carbon due to steric hindrance, to which the thiolato anion selec-
tively attacks by an SN20 mechanism. Another possibility is for-
mation of allylic cation coordinated complex which selectively
reacts with thiolato anion at the substituted carbon, since the sec-
ondary and tertiary carbocation is more stable than the primary
one. Such stabilization of these intermediates with increased nu-
cleophilic reactivity of the thiolate could be assisted by water co-
ordination and solvent effect, though further mechanistic studies
including immiscible solvent interface problems are required.
Biphasic allylation can also be applied for amine and carbon
nucleophile. Treatment of diethylamine with allyl alcohol in the
presence of Pd(OAc)2/5 TPPTS (0.4 mol %) at 110 ꢁC for 2 h in
water/pentane media gave allyldiethylamine quantitatively. Al-
lylation of 2,4-pentanedione with allyl alcohol selectively gave
monoallylation product in 73% yield in the presence of NaOH
(8 mol %).
6
7
ˆ
Genet, M. Safi, M. Savignac, and D. Sinou, Tetrahedron, 50,
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by [PdCl(ꢀ3-C3H5)]2 and TPPTS in an water/ethyl acetate bi-
phasic system, where nucleophiles attack the possible ꢀ3-allyl
intermediate. H. Kinoshita, H. Shinokubo, and K. Oshima,
Org. Lett., 6, 4085 (2004).
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8
9
Table 4. Recycling of catalyst for allylation of benzenethiola
Run
Conv./%
Yield/%
1
2
3
4
100
100
100
100
93
97
93
96
aReaction conditions: Pd(OAc)2 (0.02 mmol), TPPTS (0.10
mmol), allyl alcohol (1.0 mmol), benzenethiol (1.0 mmol),
solvent = water 4.0 mL, hexane 4.0 mL, room temperature, 2 h.
Published on the web (Advance View) January 22, 2005; DOI 10.1246/cl.2005.246