Novel nickel-catalyzed coupling reaction of allyl ethers with chlorosilanes, alkyl tosylates, or alkyl halides promoted by vinyl-Grignard reagent leading to allylsilanes or alkenes

Article abstract of DOI:10.1002/adsc.200404192

A new method for a carbon-silicon or carbon-carbon bond forming reaction between allyl ethers and chlorosilanes, alkyl tosylates, or alkyl halides giving rise to allylsilanes or alkenes has been developed. This reaction proceeds efficiently at ambient temperature by the combined use of nickel catalysts and a vinyl-Grignard reagent. A possible reaction pathway involving the formation of allyl-Grignard reagents via transmetallation of π-allylnickel complexes with the vinyl-Grignard reagent and subsequent trapping of the thus formed allyl-Grignard reagents with electrophiles is proposed.

Full text of DOI:10.1002/adsc.200404192

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Novel Nickel-Catalyzed Coupling Reaction of Allyl Ethers with
Chlorosilanes, Alkyl Tosylates, or Alkyl Halides Promoted by
Vinyl-Grignard Reagent Leading to Allylsilanes or Alkenes
Jun Terao, Hiroyasu Watabe, Hiroyuki Watanabe, Nobuaki Kambe*
Department of Molecular Chemistry & Science andTechnology Center for Atoms, Molecules andIons Control, Graduate
School of Engineering, Osaka University, Yamadaoka 2-1, Suita, Osaka 565-0871, Japan
Fax: (þ81)-6-6879-7390, e-mail: kambe@chem.eng.osaka-u.ac.jp
Received: June 21, 2004; Accepted: October 22, 2004
ð2Þ
Abstract: A new methodfor a carbon-silicon or car-
bon-carbon bondforming reaction between allyl
ethers andchlorosilanes, alkyl tosylates, or alkyl hal-
ides giving rise to allylsilanes or alkenes has been de-
veloped. This reaction proceeds efficiently at ambi-
ent temperature by the combineduse of nickel cata-
lysts anda vinyl-Grignardreagent. A possible reac-
tion pathway involving the formation of allyl-
Grignardreagents via transmetallation of p-allyl-
nickel complexes with the vinyl-Grignardreagent
andsubsequent trapping of the thus formedallyl-
Grignardreagents with electrophiles is proposed.
For example, chlorotriethylsilane reactedwith allyl phe-
nyl ether 1 in the presence of CH2 CH-MgCl anda cat-
alytic amount of NiCl2 in THFat 258C for 1 h to give al-
lyltriethylsilane 2 in quantitative yieldbasedon the allyl
ether 1, Eq. (3), run 1. In this reaction, only a trace
¼
¼
amount of Et3SiCH CH2 (<2%) was formed, probably
through the direct reaction of Et3SiCl with CH2 CH-
¼
MgCl. Interestingly, when PhMgBr was usedinsteadof
CH2 CH-MgCl, 2 was not obtainedat all, but conven-
¼
tional cross-coupling of allyl phenyl ether with PhMgBr
took place exclusively to give allylbenzene 3 in 86%
yield,[6] Eq. (3), run 2. n-BuMgCl afforded only a 13%
yieldof 2 along with a trace amount of cross-coupling
product 4 , Eq. (3), run 3. Under the identical con-
ditions as run 1 in Eq. (3), Ni(acac)2, Ni(COD)2, and
NiCl2(PPh3)2 also afforded 2 quantitatively. When
NiCl2(dppp), PdCl2, and Cp2TiCl2[7] were used, 2 was ob-
tainedin 61%, 39%, and9% yields, respectively.
Keywords: alkyl tosylates; allyl ethers; carbon-car-
bon bondformation; carbon-silicon bondformation;
chlorosilanes; Grignardreagents; nickel
Allyl ethers have been widely utilized as versatile sour-
ces of allylic carbon units in organic synthesis. A number
of allylation reactions have been developed using allyl
ethers catalyzedby transition metals, where palladium
complexes are employedin many of these cases. [1,2] We
[3]
have recently developed C C andC Si[4] bond-form-
ing reactions using alkyl halides and chlorosilanes, re-
spectively, towards organometallic reagents or dienes
by the combineduse of nickel catalysts andGrignardre-
agents. During the course of these studies, we have
foundthat Ni catalyzes the coupling reaction of allyl
ethers with chlorosilanes,[5] alkyl tosylates, or alkyl hal-
ides under mild conditions in the presence of a vinyl-
Grignardreagent, Eqs. (1) and(2).
À
À
ð3Þ
In Table 1 are summarizedthe results of the Ni-cata-
lyzedcoupling reaction of allyl ethers with chlorosilanes
using CH2 CH-MgCl. It is noteworthy that allyl trime-
ð1Þ
¼
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DOI: 10.1002/adsc.200404192
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Novel Nickel-CatalyzedCoupling Reaction of Allyl Ethers
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[a]
¼
Table 1. Ni-catalyzedcoupling reaction of allyl ethers with chlorosilanes using CH CH-MgCl.
2
[a]
¼
Conditions: R3SiCl (1.2 mmol), allyl ether (1 mmol), CH2 CH-MgCl (2.2 mmol), 2 mol % of NiCl2, THF, 258C, 1 h.
NMR yield. The isolated yield is given in parentheses.
Determinedby NMR andGC.
GC yield.
[b]
[c]
[d]
[e]
3 h.
[f]
5 mol % of NiCl2 and2 mmol of the chlorosilane were used.
thylsilyl ether 5, easily available from the corresponding
allyl alcohol, gave the allylsilane 2 in an excellent yield
(entry 1). Ph3SiCl can be employedas the silylating re-
agent to afford 6 in 89% yield(entry 2). Allyl ether 7
possessing a Ph group at the b-carbon gave the corre-
sponding allylsilane 8 in 77% yield(entry 3). When
(E)-cinnamyl trimethylsilyl ether 9 was used, (E)-cinna-
mylsilane 10 was obtainedas the sole product without
the formation of its regioisomer (entry 4). An allyl ether
having an alkyl substituent at the g-carbon 11 [E/Z¼
100/0] afforded the corresponding allylsilane 12 in
70% yieldas a 77:23 mixture of E/Z isomers (entry 5).
It shouldbe notedthat the corresponding a-substituted
ð4Þ
allyl ether 13 also formed 12 (entry 6) with the same re- at the benzylic carbon to yield 18 in 63% yieldalong
gio- andstereoselectivities as entry 5, indicating that with the formation of 17 as the minor product, Eq. (5).
these reaction proceed via the same intermediate. 2-Cy- Under the same conditions, secondary alkyl tosylates
clohexenyl trimethylsilyl ether reactedwith n-Bu3SiCl can also undergo the present coupling efficiently to
to give the corresponding allylsilane 15 in 67% yield(en-
try 7).
give a mixture of regioisomers 19 and 20 in 5% and
80% yields, respectively, Eq. (5).
When alkyl tosylates were usedinsteadof chlorosi-
À
lanes, the C C bondforming reaction took place. n-
Heptyl tosylate reactedwith 5 under similar conditions
as run 1 in Eq. (3) giving rise to 1-decene 16 in 78%
yield, Eq. (4), run 1. n-Heptyl iodide and bromide also
gave 16 in moderate yields, Eq. (4), runs 2 and 3, where-
as the reaction of n-heptyl chloride was sluggish, Eq. (4),
run 4.
In contrast to the case of silylation reaction shown in
run 4 of Table 1, alkylation of cinnamyl trimethylsilyl
ether 9 with n-butyl tosylate took place preferentially
ð5Þ
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Scheme 1. A plausible reaction pathway. The other ligands are omitted for the sake of clarity.
A plausible reaction pathway of this reaction is outlined We carriedout the following control experiments to ex-
¼
in Scheme 1. NiX2 is reduced by CH2 CH-MgCl to af- amine the validity of this reaction pathway. Firstly, p-al-
fordNi 0 via 21 (R’’¼vinyl) with the concomitant forma- lylnickel complex 31 (corresponding to 23 in Scheme 1)
tion of 1,3-butadiene.[8] The thus formedNi 0 undergoes was preparedby the reportedprocedure [9c] andits reac-
oxidative addition towards the allyl ether to afford the tivity towards chlorosilanes was examined. To a THF
p-allylnickel complex 23.[9] Subsequent transmetalla- solution of 31 was added Et3SiCl (2.0 equivs.) andstirred
¼
tion of 23 with 2 equivalents of CH2 CH-MgCl gives at 258C for 1 h. The GC analysis of the reaction mixture
the allyl-Grignardreagent 25 along with the generation indicated no evidence for the formation of allylsilane 2.
of R’’2Ni 21 via the p-allyl(vinyl)nickel complex 24. Then we added Et3SiCl (2.0 equivs.) into a mixture of
¼
Then 25 reacts with electrophiles to give 26 or 27.
The interesting result shown in Eq. (3) that different solution was stirredfor 1 h, however 2 was not formed
equimolar amounts of 31 andCH CH-MgCl andthe
2
products were obtained by changing the Grignard re- again. On the other hand, when 2 equivalents of
¼
agents can be explainedas follows. When a vinyl-
Grignardreagent is used, transmetallation of
CH2 CH-MgCl were used, 2 was obtainedin 31% yield,
24 to Eq. (7). These results may be explainedby assuming
give 25 predominates over the reductive elimination that p-allylnickel complex 31 and 32 are inert towards
leading to 1,5-pentadiene. On the other hand, when chlorosilanes andthat 2 is obtainedby the reaction of
R’’¼phenyl, 24 might be prone to undergo reductive Et3SiCl with allyl-Grignardreagent 25 (X¼Cl) generat-
elimination[6] rather than transmetallation with PhMgBr edby transmetallation of 32 with another molecule of
¼
[Eq. (3), run 2]. When R’’¼n-Bu, b-hydrogen elimina- CH2 CH-MgCl via 33. Although the possibility that
tion[10] from 24 might take place. In fact, the reaction nickelate complex 33 reacts directly with chlorosilane
of Et3SiCl with 7 in the presence of n-BuMgCl afforded cannot be ruledout, the following evidence supports
isopropenylbenzene 28 as a major product along with that transmetallation does proceed under the same con-
9% of allylsilane 29 and3% of cross-coupling product
30, Eq. (6).
ditions as a catalytic system.
ð7Þ
ð6Þ
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Novel Nickel-CatalyzedCoupling Reaction of Allyl Ethers
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The reaction of 9 (1 mmol) with CH2 CH-MgCl ether,[11] andfoundthat 19 and 20 were obtainedin
(2.2 mmol) in the presence of NiCl2 (0.02 mmol) was 4% and95% within 1 min, respectively, Eq. (10). This
conducted at 258C for 3 h in the absence of chlorosilane product ratio of 19 with 20 was similar to the result of
¼
andthen the reaction was quenchedwith aqueous HCl
Eq. (5) supporting that free cinnamyl-Grignardreagent
(1 N). GC analysis of the mixture indicated the forma- is formedin the present Ni-catalyzedcoupling reaction.
tion of allylbenzene 34 and b-methylstyrene 35 in 34%
and13% yields, respectively, Eq. (8). When Ph 3SiCl
was added to the reaction mixture and stirred for
5 min before addition of aqueous HCl (1 N), 10 was ob-
tainedin 42% yieldalong with trace amounts of 34 (2%)
and 35 (3%). These results suggestedthat allyl-Grignard
¼
reagents 36 were formedfrom allyl ethers andCH CH-
MgCl in the presence of Ni.
2
ð10Þ
An alternative catalytic pathway involving oxidative cy-
cloaddition of 1,3-butadiene to Ni(0) leading to a bis(p-
allyl)Ni complex[3] as a catalytic intermediate might be
possible since 1,3-butadiene is accumulated as the reac-
tion proceeds following Scheme 1. In order to examine
its influence, the reaction depicted in run 1 of Eq. (3)
was carriedout in the presence of 1,3-butaidene
(400 mol % basedonallyl ether 1), however the reaction
rate was not affectedeven at the early stage of the reac-
ð8Þ
tion. This may imply that 1,3-butadiene is not involved in
this catalytic reaction.
We also examinedthe reactivities of Grignardreagents
In conclusion, we have developeda Ni-catalyzedcou-
towards chlorosilane and alkyl tosylate. To a mixture of pling reaction of allyl ethers with chlorosilanes, alkyl to-
¼
¼
CH2 CHCH2-MgCl (5 mmol) andCH
(5 mmol) in THF (7.5 mL) was added Et3SiCl volve formation of allyl-Grignardreagents from allyl
(1 mmol) at 258C, andthe reaction mixture was stirred ethers andvinyl-Grignardreagents by the aidof Ni cat-
for 1 min. After quenching the reaction mixture with alysts andsubsequent electrophilic trapping with R 3Si-
CH-MgCl sylates, andalkyl halides. The present reaction wouldin-
2
À
À
aqueous HCl (1 N), the GC analysis of the resulting mix- Cl or R-X to accomplish C Si or C C bondformation.
ture indicated that allylsilane 2 was formedquantitative- Although a number of Pd-catalyzed reactions have
ly while vinylsilane was not detected at all, Eq. (9). been developed to convert allyl alcohols and ethers to
When n-octyl tosylate was usedinsteadof Et SiCl, 1-un- allyl-metal species employing different reducing agents
3
decene was also obtained quantitatively as a sole prod- (Zn,[2] SnCl2,[2] SmI2,[2] InI,[12] Et2Zn[2] andEt B[13]), in
3
uct although a longer reaction time was required. These many of these cases the resulting alkyl-metal species
results indicate that electrophiles react with the allyl- were trappedwith carbonyl compounsd as electro-
Grignardreagent exclusively even in the presence of a
vinyl-Grignardreagent.
philes.[14,15] The present Ni-catalyzedreaction is unique
in the sense that chlorosilanes andalkyl halides or tosy-
lates can be employedas the electrophiles andwould
provide a new method for the generation of allyl-
Grignard reagents. Mechanistic details including the
specific features of the vinyl-Grignardreagent are cur-
rently under investigation.
ð9Þ
Experimental Section
Allyltriphenylsilane (6)
To a mixture of allyl phenyl ether 1 (132 mg, 1.0 mmol), chloro-
triphenylsilane (356 mg, 1.2 mmol), anda catalytic amount of
NiCl2 (2.6 mg, 0.020 mmol) was added a THF solution of
We next examinedthe regioselectivity of the reaction of
s-butyl tosylate with cinnamyl-Grignardreagent, gener-
atedfrom Rieke magnesium andcinnamyl phenyl
¼
CH2 CH-MgCl (1.0 M, 2.2 mL, 2.2 mmol) at 258C under ni-
trogen. After stirring the mixture for 1 h, 1 N aqueous HCl
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Jun Terao et al.
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(ca. 1 mL) was added to the solution. Saturated aqueous
NH4Cl solution (10 mL) was added, and the product was ex-
tracted with diethyl ether (10 mL), dried over MgSO4, and
the extract evaporated to give a pale yellow crude product
(89% NMR yield). Purification by recrystallization from hex-
ane afforded 6; yield: 254 mg (86%); mp 89–908C; IR (KBr):
References and Notes
[1] a) J. Tsuji, Palladium Reagents and Catalysts, John Wiley
& Sons, Inc., Chichester, 1995, pp. 345–356; b) Hand-
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thesis, V2.1.1–4 (Ed.: E. Negishi), Wiley, New York,
2002, pp. 1669–1793.
[2] Y. Tamaru, in: Handbook of Organopalladium Chemistry
for Organic Synthesis, V2.3.4 (Ed.: E. Negishi), Wiley,
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[3] a) J. Terao, H. Watanabe, A. Ikumi, H. Kuniyasu, N.
Kambe, J. Am. Chem. Soc. 2002, 124, 4222–4223; b) J.
Terao, A. Ikumi, H. Kuniyasu, N. Kambe, J. Am.
Chem. Soc. 2003, 125, 5646–5647; c) J. Terao, S. Nii,
F. A. Chowdhury, A. Nakamura, N. Kambe, Adv. Synth.
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43, 6180–6182.
n¼3059, 3045, 3007, 2991, 1427, 1111, 1102, 731, 707 cmÀ1
;
1H NMR (400 MHz, CDCl3): d¼7.53–7.51 (m, 6H), 7.43–
7.33 (m, 9H), 5.87 (ddt, J¼17.2, 10.0, 8.0 Hz, 1H), 4.94 (d,
J¼17.2 Hz, 1H), 4.88 (d, J¼10.0 Hz, 1H), 2.40 (d, J¼8.0 Hz,
2H); 13C NMR (100 MHz, CDCl3): d¼135.6, 134.4, 133.6,
129.4, 127.6, 114.9, 21.3; MS (EI): m/z (relative intensity,
%) ¼300 (Mþ, 0.2), 259 (100), 181 (11), 155 (3), 105 (7); HR-
MS: calcd. for C21H20Si: 300.1334; found: 300.1315; anal. calcd.
for C21H20Si: C 83.94, H 6.71; found: C 83.75, H 6.62.
(E)-Cinnamyltriphenylsilane (10)
To a mixture of 3-phenylallyloxytrimethylsilane 9 (196 mg,
1.0 mmol), chlorotriphenylsilane (361 mg, 1.2 mmol), anda
catalytic amount of NiCl2 (2.7 mg, 0.021 mmol) was added a
[4] J. Terao, A. Oda, A. Ikumi, A. Nakamura, H. Kuniyasu,
N. Kambe, Angew. Chem. Int. Ed. 2003, 42, 3412–3414.
[5] For Ni-catalyzedelectrochemical allylation of carbonyl
compounds with allyl chlorides or acetates using zinc(II)
¼
THF solution of CH2 CH-MgCl (1.1 M, 1.9 mL, 2.1 mmol)
at 258C under nitrogen. After stirring the mixture for 3 h,
1 N aqueous HCl (ca. 1 mL) was added to the solution. Saturat-
edaqueous NH 4Cl solution (10 mL) was added, and the prod-
uct was extractedwith ether (10 mL). The organic layer was
dried over MgSO4, andevaporatedto give a pale yellow crude
product (97% NMR yield). Purification by HPLC with CHCl3
as an eluent afforded 10; yield: 322 mg (90%); mp 93–948C; IR
(KBr): n¼3071, 3023, 1428, 1112, 968, 850, 732, 700, 522, 488,
´
species, see: S. Durandetti, S. Sibille, J. Perichon, J. Org.
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[6] T. Hayashi, M. Konishi, K. Yokota, M. Kumada, J. Chem.
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418, 402 cmÀ1
;
1H NMR (400 MHz, CDCl3): d¼7.55–7.08
(m, 20H), 6.28–6.23 (m, 2H), 2.56–2.50 (br d-like m, 2H);
13C NMR (100 MHz, CDCl3): d¼138.0, 135.6, 134.2, 130.2,
129.4, 128.2, 127.7, 126.3, 126.0, 125.5, 20.6; MS (EI): m/z (rel-
ative intensity, %)¼376 (Mþ, 2), 259 (100), 181 (9), 155 (3), 105
(5); HRMS: calcd. for C27H24Si: 376.1647; found: 376.1638;
anal. calcd. for C27H24Si: C 86.12, H 6.42; found: C 86.04, H,
6.40.
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1-Decene (16)
To a mixture of allyloxytrimethylsilane 5 (118 mg, 0.9 mmol),
n-heptyl tosylate (295 mg, 1.1 mmol), anda catalytic amount
of NiCl2 (2.4 mg, 0.019 mmol) was added a THF solution of
¼
CH2 CH-MgCl (1.3 M, 1.7 mL, 2.2 mmol) at 258C under nitro-
gen. The reaction was quenchedby 1 N aqueous HCl andthe
organic layer was analyzedby GC using octane as an internal
standard to show the formation of 1-dodecene 16 in 78% yield.
The structure of 16 was confirmedby comparison with an au-
thentic sample using GC andGC-MS.
[14] For the reaction using Me3SiCl as electrophile, see: S.
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Acknowledgements
This research was financially supported by the Ministry of Edu-
cation, Culture, Sports, Science and Technology of Japan. One
of the authors (H. W.) expresses his special thanks for the center
of excellence (21COE) program “Creation of Integrated Eco
Chemistry of Osaka University”.
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