Facile Pd(II)- and Ni(II)-catalyzed isomerization of terminal alkenes into 2-alkenes

Article abstract of DOI:10.1021/jo900180p

(Chemical Equation Presented) Mono- and 2,2′-disubstituted terminal alkenes can be isomerized into the more stable internal (Z)- and (E)-alkenes by treating them with catalytic amounts of [(allyl)PdCl]₂ or [(allyl)NiBr]₂, a triarylph

Full text of DOI:10.1021/jo900180p

Facile Pd(II)- and Ni(II)-Catalyzed Isomerization of Terminal
Alkenes into 2-Alkenes
Hwan Jung Lim, Craig R. Smith, and T. V. RajanBabu*
Department of Chemistry, The Ohio State UniVersity, 100 W. 18th AVenue, Columbus, Ohio 43210
rajanbabu.1@osu.edu
ReceiVed January 31, 2009
Mono- and 2,2′-disubstituted terminal alkenes can be isomerized into the more stable internal (Z)- and
(E)-alkenes by treating them with catalytic amounts of [(allyl)PdCl]2 or [(allyl)NiBr]2, a triarylphosphine,
and silver triflate at room temperature. The isomeric ratio (E:Z) depends on the alkenes, the E-isomer
being the major one. The reaction is tolerant to a wide variety of functional groups including other
reactive olefins. Unlike the more reactive Ir catalysts, monosubstituted alkenes give almost exclusively
the 2-alkenes. Direct comparison to two of the best-known catalysts for this process {[Ir(PCy3)3]+[BPh4]-
and Grubbs generation II metathesis catalyst} is also described.
SCHEME 1. Isomerization of Allyl Ethers into Vinyl Ethers
Introduction
Isomerization of allylic derivatives is a well-known reaction1
that has been used in unmasking allylic protecting groups2 and
enantioselective synthesis of vinyl amines3a and ethers.3b
Notable applications of the vinyl ether synthesis include the
use of these intermediates for other C-C bond-forming reactions
such as Claisen rearrangements.4a,b The isomerization reaction
has also been used for the stereoselective syntheses of silyl ethers
of aldehyde enols.4c,d Depending on the metal and the reaction
conditions, varying selectivities for the isomerized (E)- and (Z)-
alkenes have been observed. In general, while Ni(II) catalysts
deliver the best Z:E ratios,5 Ir catalysts are the optimal reagents
for the preparation of E-olefins (Scheme 1).4b–d,6 Low-yielding
(1) (a) Frauenrath, H. In Houben-Weyl, E15/1; Kropf, H.; Schaumann, E.,
Eds.; Thieme: Stuttgart, 1995; p 1. (b) For a recent review describing applications
in synthesis that appeared after the initial submission of this manuscript, see:
(c) Donohue, T. J.; O’Riordan, T. J. C.; Rosa, C. P. Angew. Chem., Int. Ed.
2009, 48, 1014.
(2) (a) Greene, T. W.; Wuts, P. G. M. ProtectiVe Groups in Organic Synthesis,
2nd ed.; Wiley: New York, 1991. (b) Kocienski, P. J. Protecting Groups; Thieme
Verlag: Stuttgart, 2000.
(3) (a) Otsuka, S.; Tani, K. Synthesis 1991, 665. (b) Frauenrath, H.; Brethauer,
D.; Reim, S.; Maurer, M.; Raabe, G. Angew. Chem., Int. Ed. 2001, 40, 177.
(4) (a) Reuter, J. M.; Salomon, R. G. J. Org. Chem. 1977, 42, 3360. (b) Nelson,
S. G.; Bungard, C. J.; Wang, K. J. Am. Chem. Soc. 2003, 125, 13000, and references
therein. (c) Stevens, B. D.; Bungard, C. J.; Nelson, S. G. J. Org. Chem. 2006, 71,
6397. (d) Ohmura, T.; Yamamoto, Y.; Miyaura, N. Organometallics 1999, 18, 413.
(e) A mineral acid mediated isomerization of terminal methylene compounds is
unlikely to be of broad value for reactions of sensitive substrates reported in
this paper: (f) Buckle, D. R.; Arch, J. R. S.; Edge, C.; Foster, K. A.; Houge-
Frydrych, C. S. V.; Pinto, I. L.; Smith, D. G.; Taylor, J. F.; Taylor, S. G.; Tedder,
J. M.; Webster, R. A. B. J. Med. Chem. 1991, 34, 919.
(5) Wille, A.; Tomm, S.; Frauenrath, H. Synthesis 1998, 305, and references
therein.
(6) (a) Baudry, D.; Ephritikhine, M.; Felkin, H. J. Chem. Soc., Chem.
Commun. 1978, 694. (b) Matsuda, I.; Kato, T.; Sato, S.; Izumi, Y. Tetrahedron
Lett. 1986, 27, 5747. (c) Baxendale, I. R.; Lee, A.-L.; Ley, S. V. J. Chem. Soc.,
Perkin Trans. 1 2002, 1850. (d) Shen, X.; Wasmuth, A. S.; Zhao, J.; Zhu, C.;
Nelson, S. G. J. Am. Chem. Soc. 2006, 128, 7438. (e) Patnam, R.; Ju´arez-Ruiz,
J. M.; Roy, R. Org. Lett. 2006, 8, 2691.
10.1021/jo900180p CCC: $40.75
Published on Web 05/14/2009
2009 American Chemical Society
J. Org. Chem. 2009, 74, 4565–4572 4565

Lim et al.
TABLE 1. Isomerization of 1-Methylenetetralin (1) and 1-(2-Phthalimidoethyl)styrene (3a)a
yield (%)
4 (E:Z)
entry
catalyst (mol %), additives (mol %)
conditions
2
1
2
3
4
[(allyl)NiBr]2 (5), Ph3P (10) AgOTf (5), ethylene
[(allyl)PdCl]2 (5), Ph3P (5) AgOTf (5), ethylene
[(allyl)PdCl]2 (1), Ph3P (5) AgOTf (1), diallyl ether (1)
[(allyl)NiBr]2 (1), Ph3P (2) NaBARF(1), diallyl ether (1)
[(allyl)PdCl]2 (5), (o-tol)3P (10) AgOTf (10), CH2Cl2
(Ir(COE)2Cl]2, PCy3, NaBPh4, CH2Cl2/acetone (50:1)
[Cl2RuL3] Grubbs 2nd gen (10) MeOH
ethylene (1 atm), 25 °C, 2 d
ethylene (1 atm, 20 min), 25 °C, 2 d
25 °C, 1.5 d
25 °C, 2 d
25 °C, 2 d
0
90
90
82
>99
<2
∼7
<5
79 (15:1)b
79 (8:1)b
5
∼10c
<2
∼7
6d
7e
25 °C, 3 h
60 °C, 1 d
a See eqs 5 and 6 and Experimental Section for details. b 16 mol % cat., 35 °C. c 10 mol % cat. d Reference 6d, Scheme 1. e Reference 8a, eq 1.
isomerizations of terminal alkenes catalyzed by Pt,7a Rh,7a Pd,7b
and Ni7c have been known since 1964. The role of a bulky ligand
and the intermediacy of the metal hydride implied in the [2-Me-
C6H4-O)3P]3Ni/HCl7c have been effectively used to design other
protocols for this reaction.7d,e Iridium(I) catalysts originally
developed by Felkin6a have been modified for the skeletal
isomerization of functionalized terminal alkenes at room
temperature.6a–e The most recent entry into this group of
catalysts capable of effecting the skeletal isomerization of
C-allylic appendages in highly functionalized substrates is the
Grubbs generation II metathesis catalyst that has been “thermally
modified” (eq 1).8
Since cationic metal hydrides have been implicated in these
reactions, we wondered whether the hydrovinylation conditions
could be modified to improve the yield of selectiVe isomerization
of a monosubstituted terminal alkene into a 2-alkene and of a
2,2′-disubstituted alkene into a trisubstituted alkene. We are
especially interested in avoiding the complication from subse-
quent isomerization of the primary product, which often
accompanies some of the isomerization reactions of terminal
alkenes involving Ir6b,e and Ru.8h This isomerization is especially
problematic when the homoallylic position of the carbon chain
in the starting alkene is unsubstituted (eq 4). There are only
limited reports of rearrangements of 2,2′-disubstituted alkenes
to the corresponding internal trisubstituted isomer.8h When
coupled with a Wittig, Grignard, or Keck radical allylation8f
reaction, to produce the ethylidene derivative, this transformation
could be quite useful. In acyclic systems, the configuration of
the newly formed carbon-carbon double bond would also be
of some interest.11 The results of these studies are reported here.
During our studies on asymmetric hydrovinylation of 2,2′-
disubstituted alkenes we noticed that some substrates consis-
tently gave varying proportions of a minor component readily
identified as the allylic rearrangement product as illustrated in
eqs 2a and 2b.9 A similar rearrangement was also detected
during cycloisomerization of dienes catalyzed by {[(allyl)PdCl]2/
AgOTf/[(2-Me-C6H4)3P]} (eq 3).10
Results
Our initial studies concentrated on the little known8h isomer-
ization of the 2,2′-disubstituted alkenes. Results of isomerization
of the two prototypical substrates 1-methylenetetralin (1, eq 5)
and 1-(2-phthalimidoethyl)styrene (3, eq 6) are shown in Table
1. When 1 was reacted under typical hydrovinylation condi-
tions12 using Ph3P as a ligand,{[(allyl)NiBr]2, Ph3P, AgOTf, 25
°C, 2 d)} in an atmosphere of ethylene, no reaction ensued (entry
1, column 4). In accordance with our previous observation that
Pd(II) salts show enhanced reactivity under these conditions,12b
the use of [(allyl)PdCl]2 instead of the corresponding Ni salt
4566 J. Org. Chem. Vol. 74, No. 12, 2009

Isomerization of Terminal Alkenes into 2-Alkenes
TABLE 2. Isomerization of 2,2′-Disubstituted Alkenesa
leads to the expected product 2 in very good yield (entry 2,
column 4).13 Typically the reaction involving ethylene is carried
out as follows: appropriate amounts of the metal salt, the
phosphine, and AgOTf are mixed in CH2Cl2 in a drybox in a
Schlenk tube, and the mixture is taken out of the box and placed
in an atmosphere of ethylene for 20 min. The alkene is
introduced, the ethylene atmosphere is replaced by nitrogen,
and the mixture is stirred for 2 days at rt. Unlike the
hydrovinylation reaction, there is no need to remove the
precipitated salts (AgX) for the isomerization reactions. While
the use of ethylene has a slight advantage in the recovery of
products, we find that an operationally simpler procedure is to
use catalytic amounts of diallyl ether (entry 3). Presumably
diallyl ether, which undergoes facile cycloisomerization to
3-methylene-4-methyltetrahydrofuran, readily produces10a,b the
requisite cationic metal hydride with minimum of contamination
by other side products. Use of diallyl ether also helps the Ni-
catalyzed reaction if a highly dissociated counteranion, [(3,5-
(CF3)2C6H3]4B-, is used instead of OTf (entry 4, column 4).14,12b
Thus with 1 mol % of [(allyl)2NiBr]2 and 2 mol % each of Ph3P,
Na+[(3,5-(CF3)2C6H3]4B- (BARF) and diallyl ether 1 gives very
good yield of the isomerization product 2 (entry 4).
Isomerization of functionalized alkene 3a (eq 6) is best carried
out in the presence of ethylene or diallyl ether (entries 2 and 3,
(7) (a) Harrod, J. F.; Chalk, A. J. J. Am. Chem. Soc. 1964, 86, 1776. (b)
Davies, N. R. Aust. J. Chem. 1964, 17, 212. (c) Gosser, L. W.; Parshall, G. W.
Tetrahedron Lett. 1971, 2555. (d) Lochow, C. F.; Miller, R. G. J. Org. Chem.
1976, 41, 3020. (e) Malanga, C.; Urso, A.; Lardicci, L. Tetrahedron Lett. 1995,
36, 1133. (f) For reports on the use of isomerization of C-allyl compounds in
the context of complex molecule synthesis, see the following. (g) Via Rh-
intermediates: Warmerdam, E.; Tranoy, I.; Renoux, B.; Gesson, J.-P. Tetrahedron
Lett. 1998, 39, 8077. (h) Nakamura, H.; Arata, K.; Wakamatsu, T.; Ban, Y.;
Shibasaki, M. Chem. Pharm. Bull. 1990, 38, 2435. (i) Pd: Whang, K.; Cooke,
R. J.; Okay, G.; Cha, J. K. J. Am. Chem. Soc. 1990, 112, 8985. (j) Ruthenium
hydride: Curran, D. P.; Jacobs, P. B.; Elliott, R. L.; Kim, B. H. J. Am. Chem.
Soc. 1987, 109, 5280.
a [(Allyl)PdCl]2 (5 mol %), (o-tol)3P (10 mol %), AgOTf (10 mol %),
CH2Cl2 (0.05 M). Determined by H NMR analysis.
b
1
column 5), since other conditions gave virtually no reaction.
The ratio of E:Z alkenes was found to depend on the additive,
with ethylene giving the mixture in an E:Z ratio of 15:1 as
determined by 1H NMR. This reaction appears to be very
sensitive to steric effects, since the ortho-substituted derivative
3b gave no product.
(8) (a) Hanessian, S.; Giroux, S.; Larsson, A. Org. Lett. 2006, 8, 5481. (b)
Dinger, M.; , B.; Mol, J. C. Eur. J. Inorg. Chem. 2003, 2827. See also: (c)
Arisawa, M.; Terada, Y.; Nakagawa, M.; Nishida, A. Angew. Chem., Int. Ed.
2002, 41, 4732, and references therein. (d) Yue, C. J.; Liu, Y.; He, R. J. Mol.
Catal. A: Chem. 2006, 259, 17. (e) Bo¨hrsch, V.; Blechert, S. Chem. Commun.
2006, 1968. (f) Wipf, P.; Spencer, S. R. J. Am. Chem. Soc. 2005, 127, 225. (g)
Schmidt, B. Eur. J. Org. Chem. 2004, 1865. For a bifunctional Ru catalyst that
brings about isomerization of double bonds over 30 positions, see: (h) Grotjahn,
D. B.; Larsen, C. R.; Gustafson, J. L.; Nair, R.; Sharma, A. J. Am. Chem. Soc.
2007, 129, 9592. See also: (i) Cadot, C.; Dalko, P. I.; Cossy, J. Tetrahedron
Lett. 2002, 43, 1839. (j) Alcaide, B.; Almendros, P.; Alonso, J. M.; Aly, M. F.
Org. Lett. 2001, 3, 3781. (k) Donohue, T. J.; Rosa, C. P. Org. Lett. 2007, 9,
5509.
(9) (a) Zhang, A.; RajanBabu, T. V. J. Am. Chem. Soc. 2006, 128, 5620. (b)
Smith, C. R.; RajanBabu, T. V. Org. Lett. 2008, 10, 1657. (c) Smith, C. R.;
Lim, H. J.; RajanBabu, T. V. Synthesis 2009, in press. For recent reviews of
hydrovinylation, see: (d) Jolly, P. W.; Wilke, G. Hydrovinylation. In Applied
Homogeneous Catalysis with Organometallic Compounds; Cornils, B.; Herrmann,
W. A., Eds.; VCH: New York, 1996; Vol. 2, pp 1024-1048. (e) RajanBabu,
T. V. Chem. ReV. 2003, 103, 2845. (f) RajanBabu, T. V. Synlett 2009, 853.
(10) (a) Radetich, B.; RajanBabu, T. V. J. Am. Chem. Soc. 1998, 120, 8007.
For other related observation, see: (b) Lloyd-Jones, G. C. Org. Biomol. Chem.
2003, 215. (c) Kisanga, P.; Widenhoefer, R. A. J. Am. Chem. Soc. 2000, 122,
10017. (d) Yamamoto, Y.; Ohkoshi, N.; Kameda, M.; Itoh, K. J. Org. Chem.
1999, 64, 2178. (e) Heumann, A.; Moukhliss, M. Synlett 1998, 1211. (f) Grigg,
R.; Malone, J. F.; Mitchell, T. R. B.; Ramasubbu, A.; Scott, R. M. J. Chem.
Soc., Perkin Trans. 1 1984, 1745. (g) Behr, A.; Freudenberg, U.; Keim, W. J.
Mol. Catal. 1986, 35, 9. (h) Bogdanovic´, B. AdV. Organomet. Chem. 1979, 17,
105.
Experimentally the use of commercially available [(allyl)P-
dCl]2 has a clear advantage over [(allyl)NiBr]2, which is a
thermally sensitive solid that has to be kept at low temperature
in a drybox.15 In subsequent experiments we discovered that
for simple substrates such as 1 when the Pd-catalyzed reaction
is carried out in the presence of (o-tolyl)3phosphine, there is no
need to have the ethylene or diallyl ether present for a
quantitative conversion to the product (entry 5, column 4).
Entries 66d and 78a list the use of two of the best catalysts
capable of allylic isomerizations. Neither the Ir(I) nor the
modified Grubbs generation II catalyst under the prescribed
reaction conditions is useful for this transformation.
Further scope of the reaction is shown in Table 2, which lists
other alkenes that undergo the isomerization under these
conditions. The 1-indanone-derived alkene 5 gave an excellent
yield of the internal alkene at room temperature (entry 1).
Methylene compounds prepared via Wittig reaction of aryl alkyl
ketones are excellent substrates for this reaction. 2-Arylbutenes
6-8 gave excellent yields of the product, an internal alkene.
While the 2-naphthyl derivative 7 gave good E-selectivity, the
1-naphthyl analog 8 gave only a 2:1 mixture of (E)- and (Z)-
alkenes. Attempted isomerization of the furyl derivative 9 led
to polymerization.
(11) (a) Importance of tri-substituted alkenes: Chatterjee, A. K.; Grubbs, R. H.
Org. Lett. 1999, 1, 1751. (b) A recent report on E/Z isomerization of
arylalkenes: Yu, J.; Gaunt, M. J.; Spencer, J. B. J. Org. Chem. 2002, 67, 4627.
(12) (a) Nomura, N.; Jin, J.; Park, H.; RajanBabu, T. V. J. Am. Chem. Soc.
1998, 120, 459. (b) RajanBabu, T. V.; Nomura, N.; Jin, J.; Nandi, M.; Park, H.;
Sun, X. J. Org. Chem. 2003, 68, 8431.
(15) (a) Wilke, G.; Bogdonovic, B.; Hardt, P.; Heimbach, P.; Keim, W.;
Kro¨ner, M.; Oberkirck, W.; Tanaka, K.; Steinru¨cke, E.; Walter, D.; Zimmermann,
H. Angew. Chem., Int. Ed. Engl. 1966, 5, 151. (b) Synthetic Methods of
Organometallic and Inorganic Chemistry; Herrmann, W. A.; Salzer, A., Eds.;
Georg Thieme Verlag: Stuttgart, 1996; Vol. 1, p 156. Details of the preparation
of [(allyl)NiBr]2: (c) Smith, C. R.; Zhang, A.; Mans, D.; RajanBabu, T. V. Org.
Synth. 2008, 85, 248.
(13) See Supporting Information for 1H and 13C NMR spectra of key starting
materials and products, and gas chromatograms of products from various
reactions.
(14) Effect of counteranions in related reactions, see: Nandi, M.; Jin, J.;
RajanBabu, T. V. J. Am. Chem. Soc. 1999, 121, 9899.
J. Org. Chem. Vol. 74, No. 12, 2009 4567

Lim et al.
TABLE 3. Selective Isomerization of C- and O-Allyl Derivatives
a Determined by NMR or GC. b 9% unidentified material and 10% starting material. c Rest starting material. d Mixture of E/Z, configuration not
determined.
SCHEME 2. Isomerization of a Terminal Alkene using an
Ir(I) Catalyst4b,6d
Monosubstituted terminal alkenes also undergo the isomer-
ization with remarkable ease under the typical conditions
outlined in the previous paragraph, giving exclusively the
2-alkene. Several nontrivial examples of this transformation are
shown in Table 3. 6-(tert-Butyldimethylsiloxy)hex-1-ene 13
undergoes exceptionally clean isomerization to the correspond-
ing (Z)- and (E)-2-hexenes (18) under typical hydrovinylation
conditions at -55 °C (entry 1).13 The expected internal olefin
18 is formed in >95% yield in an E:Z ratio of 3.5:1.0 as judged
1
by H NMR spectroscopy and gas chromatography. No trace
of any other alkenes is observed under these conditions. The
reaction catalyzed by Pd(II) (entry 2) gives 80% yield of (E)-
and (Z)-18 in the same ratio. This reaction is less clean compared
to the Ni-catalyzed reaction, the product being contaminated
with up to 10% starting material, and 9% of another isomeric
alkene.13 Isomerization of 13 using the metathesis catalyst (eq
1, 10 mol % [Ru], MeOH, 60 °C, 12 h) yields <45% of the E/Z
mixture (3.8:1.0) of 18 contaminated with other isomers. The
Ir(I) catalyst [(Ir(COE)Cl]2, PCy3, NaBPh4, CH2Cl2/acetone (50:
1)]4b gave 94% yield of (E)-1-tert-butyldimethylsiloxyhexene
(Scheme 2).
the disubstituted alkene 19. The E- and Z-isomers are obtained
in >95% yield in a ratio of 5.9:1.0 with <4% of the starting
material (entry 3). The Ir(I) catalyst gives a mixture of products
arising from both 1,3- and 1,6-hydrogen shifts with the latter
predominating (Scheme 2).13 The modified Grubbs catalyst gave
a mixture of 14% starting material, 47% (E)-19, and 12% (Z)-
19 along with a mixture of isomers.13 While 1,6-dienes readily
undergo cycloisomerization followed by isomerization of the
exocyclic alkylidene under Pd catalysis (eq 3),10a a substrate
more resistant to cyclization, such as 1,7-octadiene (15), simply
undergoes isomerization of the terminal alkenes to give a
stereoisomeric mixture of 2,6-octadienes (20) (entry 4). Surpris-
The proportion of starting material in the equilibrium mixture
of alkenes depends on the starting alkene, as indicated by the
isomerization in 1-(but-3-enyloxy)-4-methoxybenzene (14) to
4568 J. Org. Chem. Vol. 74, No. 12, 2009

Isomerization of Terminal Alkenes into 2-Alkenes
SCHEME 3. Possible Mechanism for the Alkene
Isomerization
(R′ ) alkyl) could be slow to undergo the allylic insertion
reaction (29 f 30), and ethylene is needed to generate the
reactive metal hydride. The reluctance of the metal hydride to
add to a 1,2-disubstituted alkene (34, R′ ) H) might also explain
why the exhaustive isomerizations seen with other catalysts
(Scheme 2), most notably Ir(I), are not seen in these reactions.
Conclusions
The cationic metal hydride mediated selective skeletal
isomerization of terminal alkenes provides a facile route to di-
and trisubstituted alkenes. The reaction is sensitive to steric
effects yet tolerant to a variety of common functional groups
and, in some cases, may provide synthetically useful levels of
E:Z selectivity in the formation of the trisubstituted alkenes.
Experimental Section
General Information. See Supporting Information.
Attempted Isomerization of 1-Methylene-2,3,4-trihydronaph-
thalene 1 under Hydrovinylation Conditions. General procedure
A (Table 1, entry 1, column 4). In a flame-dried flask, [(allyl)NiBr]2
or [(allyl)PdCl]2, the phosphine ligand, and the silver salt were
mixed in that order in CH2Cl2 in a drybox. After the precipitated
silver salt was removed by filtration though Celite, the solution
was taken out of the drybox and was connected to an ethylene line.
The system was evacuated and refilled with ethylene three times.
To the resulting complex was added 1 in CH2Cl2 dropwise at room
temperature. After stirring for the prescribed time (Table 1), all
volatile materials were removed, and the product was purified by
column chromatography. Gas chromatography and NMR showed
complete recovery of starting materials. We have since found that
for most isomerization reactions described below it is not necessary
to remove the precipitated silver salt.
ingly, the triene 16, prone to isomerization of the endocyclic
1,4-diene, cleanly gives 90% yield of a mixture of (E)- and
(Z)-3-butenyl derivatives (21) arising from selective isomeriza-
tion of the side chain (entry 5). Likewise, the enyne 17
undergoes just the isomerization to 22 without the expected16
cyclization of the enyne to a bisalkylidene.
Finally, several sterically demanding substrates, 23-26, failed
to undergo isomerization even under more forcing conditions.
Use of [(Allyl)PdCl]2/Phosphine/AgOTf Activated by Ethylene
for the Double Bond Migration. General procedure B (Table 1,
entry 2, columns 4 and 5). In a flame-dried three-neck flask,
[(allyl)PdCl]2, PPh3, and AgOTf were dissolved in CH2Cl2 in a
glovebox. After the reaction vessel was taken out of the box, an
ethylene line was connected to the vessel, the line was evacuated,
and then ethylene was introduced. The process was repeated three
times. The resulting monomeric allylic Pd complex was stirred for
20 min under 1 atm of ethylene at rt, and then the exomethylene
substrate 1 or 3a was added dropwise as a solution in CH2Cl2. The
ethylene was exchanged with a N2 atmosphere, and the resulting
mixture was stirred at ambient temperature for the prescribed time.
All volatile materials were evaporated, and then the mixture was
filtered using a short pad of silica gel using EtOAc/hexane solvent.
The product was analyzed by GC and NMR.
Use of [(Allyl)PdCl]2/Phosphine/AgOTf Activated by Diallyl
Ether for the Double Bond Migration. General procedure C (Table
1, entry 3, columns 4 and 5). To a premixed allyl-Pd complex in
CH2Cl2 that was prepared in the same fashion as in the previous
experiment (general procedure B), an equivalent amount of dial-
lylether was added instead of ethylene, and then the mixture was
stirred at rt for 20 min. The substrate dissolved in CH2Cl2 was added
dropwise to the catalyst solution, and the resulting mixture was
stirred at ambient temperature for the indicated time. The product
was purified and analyzed as indicated previously.
Discussion
Mechanistically the alkene isomerization is related to the
olefin dimerization reaction, since both start with a common
reactive intermediate in the form of an active metal hydride.
Such a hydride (32, Scheme 3) could be generated by initial
formation of the [(allyl)metal(phopshine)]+OTf- (28)14 from the
metal halide followed by an insertion (29 f 30) and ꢀ-hydride
elimination. The 1,4-diene 31 is formed as a byproduct.10b,17
Once the hydride is generated, it adds to the terminal alkene to
form the organometallic 33, which undergoes yet another
ꢀ-hydride elimination to give the alkene isomers (34) in a
thermodynamically controlled reaction. Note that almost invari-
ably the (E)-alkenes predominate in the isomerization reactions.
The reluctance of the 1,1-disubstituted alkene to undergo the
reaction in the absence of a sterically unencumbered alkene,
ethylene, is thus easily understood. A 1,1-disubstututed alkene
Use of [(Allyl)PdCl]2/Phosphine/AgOTf without any Additive
for the Double Bond Migration. General procedure D (Table 1,
entry 5, columns 4 and 5). To an (allyl)Pd(phosphine) complex in
CH2Cl2 that was prepared in the same fashion as in the general
procedure B, the substrate dissolved in CH2Cl2 was added dropwise,
and the resulting mixture was stirred at ambient temperature for
(16) (a) Trost, B. M.; Lautens, M. J. Am. Chem. Soc. 1985, 107, 1781. (b)
Trost, B. M. Acc. Chem. Res. 1990, 23, 34.
(17) For isolation of such an insertion product in styrene dimerization, see:
(a) DiRenzo, G. M. Mechanistic Studies of Catalytic Olefin Dimerization
Reactions Using Electrophilic η3-allyl-Palladium(II) Complexes. Ph. D. Thesis,
University of North Carolina, 1997.
(18) (a) Kobayashi, H.; Sonoda, A.; Iwamoto, H.; Yoshimura, M. Chem.
Lett. 1981, 10, 579. (b) Brookhart, M.; Grant, B.; Volpe, A. F., Jr. Organome-
tallics 1992, 11, 3920–3922.
(19) Exon, C.; Magnus, P. J. Am. Chem. Soc. 1983, 105, 2477.
J. Org. Chem. Vol. 74, No. 12, 2009 4569

Lim et al.
the indicated time. The product was purified and analyzed as
indicated previously.
(m, 1H, Ar), 6.22 (s, 1H, vinyl), 3.33 (s, 2H, allylic CH2), 2.19 (s,
3H, allylic CH3). 13C NMR (CDCl3): δ 146.1, 144.3, 139.9, 128.7,
126.0, 124.4, 123.6, 118.8, 37.6, 13.0.
Isomerization of 1 Using [(Allyl)NiBr]2/Ph3P/NaBARF and
Diallylether. (Table 1, entry 4, column 4). The precatalyst was
prepared as follows in a glovebox. To [(allyl)NiBr]2 (10.8 mg, 0.03
mmol) in CH2Cl2 (1 mL) were added PPh3 (15.7 mg, 0.06 mmol)
and NaBARF (53.0 mg, 0.06 mmol). The catalyst solution prepared
above was removed from the drybox, and diallylether (3.7 µL, 0.03
mmol) was added as a single portion under nitrogen, and the mixture
was allowed to stir for 2 min to form the active catalytic species.
A solution of the substrate 1 (433 mg, 3.00 mmol) in 3 mL of
CH2Cl2 was added dropwise over a period of 1 min, and the reaction
was allowed to proceed for 2 d. The resulting product was filtered
by flash column chromatography (eluted with pentane) to get the
desired product 2 (0.35 g, 82%) as a colorless oil, which was then
Isomerization of 1-(But-1-en-2-yl)-4-chlorobenzene (6) (Table
2, entry 2). General procedure D. The isomerization reaction of 6
(0.167 g, 1.0 mmol) was carried out using [(allyl)PdCl]2 (5 mol
%), (o-tol)3P (10 mol %), and AgOTf (10 mol %) in CH2Cl2 with
no other additive at rt for 16 h. After the solvent was evaporated,
the crude product was purified by column chromatography to yield
1
the desired product 10 (87%, E:Z ) 19:1). H NMR (CDCl3): δ
7.33-7.27 (m, 4H, Ar), 5.86 (q, 1H, J ) 6.50 Hz, vinyl), 2.02 (s,
3H, allylic CH3), 1.80 (d, 3H, J ) 6.50 Hz, allylic CH3; E), 1.59
(d, 3H, J ) 6.50 Hz, allylic CH3; Z). 13C NMR (CDCl3): δ 142.4,
134.5, 132.1, 128.2, 126.8, 123.0, 15.4, 14.3.
Isomerization of 2-(But-1-en-2-yl)naphthalene (7) (Table 2,
entry 3). General procedure D. The isomerization reaction of 7
(0.182 g, 1.0 mmol) was carried out using [(allyl)PdCl]2 (5 mol
%), (o-tol)3P (10 mol %), and AgOTf (10 mol %) in CH2Cl2 with
no other additive at rt for 16 h. After the solvent was evaporated,
the crude product was purified by column chromatography to yield
1
used to acquire all analytical data without further purification. H
NMR (CDCl3): δ 7.23-7.17 (m, 2 H), 7.15-7.10 (m, 2 H),
5.85-5.83 (m, 1 H), 2.75 (t, J ) 8.0 Hz, 2 H), 2.26-2.20 (m, 2
H), 2.04 (dd, J ) 3.2 Hz, J ) 1.6 Hz, 2 H). 13C NMR (CDCl3): δ
136.3, 135.9, 132.3, 127.3, 126.7, 126.3, 125.4, 122.8, 28.3, 23.2,
19.3.
1
the desired product 11 (97%, E:Z ) 9:1). H NMR (CDCl3): δ
Isomerization of 2-(3-(3-(Benzyloxy)phenyl)but-3-enyl)isoindo-
line-1,3-dione (3a) (Table 1, entry 2, column 5). General procedure
B. In a flame-dried three-neck flask, [(allyl)PdCl]2 (2.4 mg, 0.0061
mmol), PPh3 (3.7 mg, 0.013 mmol), and AgOTf (3.4 mg, 0.013
mmol) were dissolved in distilled CH2Cl2 (3 mL) in a glovebox.
After the reaction vessel was taken out from a box, an ethylene
line was connected to the vessel, the line was evacuated, and then
ethylene was introduced. This process was repeated three times.
The resulting Pd complex was stirred for 20 min under 1 atm of
ethylene at rt, and then the exomethylene substrate 3a (29 mg, 0.076
mmol) in CH2Cl2 (1 mL) was added dropwise. Ethylene atmosphere
was exchanged for a N2 atmosphere, and the resulting mixture was
stirred at 35 °C for 2 d. All volatile materials were evaporated,
and then the mixture was purified by flash column chromatography
to obtain 28 mg (79%) of the product 4a (E:Z ) 15:1) contaminated
7.83-7.81 (m, 2H, Ar), 7.79-7.76 (m, 2H, Ar), 7.58 (dd, 1H, J )
9.0, 2.0 Hz, Ar), 7.47-7.42 (m, 2H, Ar), 6.05 (q, 1H, J ) 7.0 Hz,
vinyl; E), 2.15 (s, 3H, allylic CH3; E), 2.13 (s, 3H, allylic CH3; Z),
1.87 (d, 3H, J ) 7.0 Hz, allylic CH3; E), 1.67 (d, 3H, J ) 7.0 Hz,
allylic CH3; Z). 13C NMR (CDCl3): δ 141.2, 135.4, 133.5, 132.3,
128.0, 127.5, 127.4, 126.0, 125.3, 124.3, 123.8, 123.1, 15.5, 14.5.
Isomerization of 1-(But-1-en-2-yl)naphthalene (8) (Table 2,
entry 4). General procedure D. The isomerization reaction of 8
(0.182 g, 1.0 mmol) was carried out using [(allyl)PdCl]2 (5 mol
%), (o-tol)3P (10 mol %) and AgOTf (10 mol %) in CH2Cl2 at rt
for 16 h. After the solvent was evaporated, the crude product was
purified by column chromatography to yield the desired product
12 (99%, E:Z ) 2:1). 1H NMR (CDCl3): δ 8.03 (dd, 1H, J ) 6.0,
2.5 Hz, Ar), 7.90 (dd, 1H, J ) 8.0, 3.5 Hz, Ar), 7.79 (d, 1H, J )
8.0 Hz, Ar), 7.54-7.50 (m, 3H, Ar), 7.32 (d, 1H, J ) 6.5 Hz, Ar),
5.87 (q, 1H, J ) 7.0 Hz, vinyl; Z), 5.66 (q, 1H, J ) 6.50 Hz, 1H;
E), 2.16 (s, 3H), 1.94 (d, J ) 6.50 Hz, 3H), 1.42 (d, J ) 6.50 Hz;
Z). 13C NMR (CDCl3): δ (E) 144.3, 135.7, 133.8, 131.4, 128.3,
126.7, 126.0, 125.6, 125.5, 125.4, 124.9, 18.7, 14.0; (Z) 140.5,
135.8, 133.7, 130.8, 128.3, 125.8, 125.6, 125.2, 124.9, 123.3, 26.1,
14.8.
Isomerization of 1,7-Octadiene (Table 3, entry 4). General
procedure D. In a nitrogen filled drybox, a dry flask was charged
with [(allyl)PdCl]2 (0.016 g, 0.045 mmol) in 1 mL of CH2Cl2. To
this solution was added 2 equiv of phosphine ligand (1 equiv with
respect to metal, 0.024 g, 0.09 mmol) followed by AgOTf (0.023
g, 0.09 mmol). The precipitate was filtered off using a Celite-
plugged pipet. After 30 min the reaction vessel was taken out from
a box. To the resulting metal catalyst was added 1,7-octadiene
(0.200 g, 1.81 mmol) in CH2Cl2 dropwise at ambient temperature.
After the resulting mixture was stirred at ambient temperature for
2 h, most of the volatile materials were evaporated, and the crude
product was analyzed by NMR and GC. Total absence of the
starting olefinic peaks in the 1H NMR due to the starting methylene
compound (δ 5.70-5.90 m; 4.90-5.05 m), and appearance of new
olefinic H at δ 5.25-5.40 (4 H) and vinyl-CH3 signals at 1.50-1.51
(6 H) indicate isomerization of the double bonds without cyclization.
Since the product is volatile the conversion was estimated to be
>95% by both NMR and GC. No further analysis was carried out.
Synthesis of 6-tert-Butyldimethylsiloxy)hex-1-ene (13). To a
solution of 0.581 g (5.81 mmol) of 5-hexene-1-ol in 5 mL of DMF
at 0 °C under nitrogen was added 1.19 g (17.4 mmol) of imidazole
and 1.31 g (8.72 mmol) of tert-butyldimethylsilyl chloride. The
mixture was stirred at rt for 2 days and subsequently quenched
with 10 mL of water. The aqueous layer was extracted with ether
(3 × 10 mL). The combined organic layers were washed with 2 N
aqueous NaOH solution and then brine and dried over MgSO4
before concentration in vacuo. The residue was purified by flash
1
with 21% of starting olefin 3a. H NMR (CDCl3): δ 7.90-7.69
(m, 4 H, phthalimidyl), 7.49-7.29 (m, 5 H, Ar), 7,19 (t, J ) 6.4
Hz, 1 H, Ar), 7.05-6.85 (m, 2 H, Ar), 6.84-6.79 (m, 1 H, Ar),
5.85 (t, J ) 7.0 Hz, 1 H, Ar(CH3)CdCHCH2N-phth), 5.03 (s, 2 H,
OCH2Ph), 4.50 (d, 7.5 Hz, 2 H, Ar(CH3)CdCHCH2N-phth, E), 4.22
(d, J ) 6.5 Hz, 2 H, Ar(CH3)CdCHCH2N-phth, Z), 2.23 (s, 3 H,
Ar(CH3)CdCHCH2NPhth, E), 2.01 (s, 3 H, Ar(CH3)CdCHCH2N-
phth, Z). 13C NMR (CDCl3): δ 168.4, 144.5, 139.4, 137.3, 134.1,
132.5, 129.6, 128.1, 127.8, 123.4, 121.6, 119.1, 113.7, 113.1, 70.2,
36.5, 16.4. HRMS 406.1400 (M + Na+•; calcd for C25H21NNaO3
406.1419). The configuration of the major product was established
by NOE studies.
Isomerization of 1-Methylene-1,2,3,-trihydronaphthalene (1)
(Table 1, entry 2, column 4). General procedure D. Following the
general procedure D using 10 mol % of preformed Pd catalyst, the
isomerization of 1 (0.145 g, 1.0 mmol) was checked. After the crude
product was purified by column chromatography, the product (2,
0.145 g, >99%) was analyzed by NMR.
Isomerization of 1-Methylene-2,3-dihydro-1H-indene (5) (Table
2, entry 1). General procedure D. The isomerization reaction of 5
(0.131 g, 1.0 mmol) was carried out using [(allyl)PdCl]2 (5 mol
%), (o-tol)3P (10 mol %), and AgOTf (10 mol %) in CH2Cl2 with
no other additive at rt for 8 h. After the solvent was evaporated,
the crude product was purified by column chromatography to yield
1
the desired product 9 (94%, isolated yield). H NMR (CDCl3): δ
7.47 (d, 1H, J ) 7.2 Hz, Ar), 7.39-7.31 (m, 2H, Ar), 7.27-7.23
4570 J. Org. Chem. Vol. 74, No. 12, 2009

Isomerization of Terminal Alkenes into 2-Alkenes
chromatography on silica gel, eluting with hexane/ethyl acetate (98:
2), to afford the silyl ether (13) as a clear oil (1.19 g, 96%). H
154.2, 153.3, 130.3, 126.8, 116.0, 69.7, 56.0, 17.9, 13.5. The
configuration of the major product was established by NOE studies.
1
NMR (CDCl3): δ 5.73-5.90 (m, 1 H), 4.91-5.06 (m, 2 H), 3.62
(t, J ) 6.4 Hz, 2 H), 2.03-2.12 (m, 2 H), 1.38-1.60 (m, 4 H),
0.90 (s, 9 H), 0.05 (s, 6 H).
Isomerization of 6-tert-Butyldimethylsiloxy)hex-1-ene. General
procedure A (Table 3, entry 1). To a solution of [(allyl)NiBr]2 (5.2
mg, 0.14 mmol) in 1 mL of CH2Cl2 under nitrogen at room
temperature was added a solution of Ph3P (7.6 mg, 0.28 mmol) in
1 mL of CH2Cl2. The resulting brown solution was added to a
mixture of AgOTf (10.3 mg, 0.40 mmol) in 1 mL of CH2Cl2. After
stirring for 1.5 h at rt, the mixture was filtered through a small
plug of Celite, and the precipitate was rinsed with 2 mL of CH2Cl2.
The filtrate was collected in a Schlenk flask and was taken out of
the drybox. The catalyst solution was cooled to -55 °C. Under an
atmosphere of ethylene, 0.428 g (2.00 mmol) of alkene 13 was
added dropwise to the catalyst solution. After stirring at -55 °C
for 4 h, the mixture was quenched with saturated NH4Cl solution
and extracted CH2Cl2 (3 × 10 mL). The combined organic layers
were dried over MgSO4 and concentrated in vacuo. The crude
product was analyzed by GC, which indicated that the alkene had
completely isomerized to two new products in a ratio of 3.5:1.0.
The volatile crude product (>95% estimated by GC) was purified
by chromatography on silica, eluting with ethyl acetate/hexane (98:
2), to afford the product(s) 18, which was analyzed by GC and
NMR. 1H NMR (CDCl3): δ 5.40-5.46 (m, 2 H), 3.57-3.65 (m, 2
H), 1.97-2.10 (m, 2 H), 1.54-1.67 (m, 5 H), 0.90 (s, 9 H), 0.05
(s, 6 H).
Isomerization of Methyl 1-(2-Butenyl)-2,5-cyclohexadiene-1-
carboxylate (16). General procedure D (Table 3, entry 5). Substrate
16 (0.1 g, 0.5 mmol) was reacted with 5 mol % [(allyl)PdCl]2 (10.4
mg, 0.026 mmol), 5 mol % of (o-CH3-C6H4)3P (16 mg, 0.05
mmol), AgOTf (13 mg, 0.05 mmol), and CH2Cl2 at rt for 1 d. The
resulting product was purified by chromatography to yield 91 mg
(91%) of 21 as a mixture E/Z isomers. Based on the 1H NMR, the
E/Z ratio was estimated as 3.6:1.0. 1H NMR (CDCl3): δ 5.88-5.73
(m, 4 H, -CHdCH- in the ring), 5.41-5.22 (m, 2 H, CH2 -C
HdCH-CH2-, E and Z), 3.69 (s, 3 H, OCH3, Z), 3.67 (s, 3 H,
OCH3, E), 2.63 (m, 2 H, RdCH-CH2-CHdR, E and Z), 2.43 (d,
J ) 5.2 Hz, 2 H, C-CH2-CHdCHCH ), 2.34 (d, J ) 6.1 Hz, 2
3
H, C-CH2-CHdCHCH3), [δ 2.43 + δ 2.34] 2 H, 1.51-1.61 two
sets of doublets (d, J ) 6.7 Hz, 3 H, CdC-C H3). 13C NMR
(CDCl3): δ 174.7, 128.6, 127.0, 126.7, 125.4, 125.3, 51.9, 47.9,
43.4, 37.2, 26.0, 17.9; HRMS 192.1132 (M+•; calcd for C12H16O2
192.1150).
Palladium-Catalyzed Isomerization of 6-tert-Butyldimethylsi-
loxy)hex-1-ene. General procedure D (Table 3, entry 2). The
isomerization reaction was carried out using [(allyl)PdCl]2 (0.50
mmol), (o-tol)3P (1 mol %), and AgOTf (1 mol %) in CD2Cl2. The
Isomerization of (tert-Butyl[[2,2-dimethyl-1-(1-propynyl)-3-pen-
tenyl]oxy] Dimethylsilane (17). General procedure D (Table 3, entry
6). Substrate 1716 (0.1 g, 0.8 mmol) was reacted with 5 mol % of
[(allyl)PdCl]2, 10 mol % of (2-Me-C6H4)3P, and 10 mol % AgOTf
in CH2Cl2 at rt for 16 h. The reaction mixture was quenched with
saturated ammonium chloride, and the product was extracted with
ether. The dried organic layer was concentrated, and the product
was purified by flash column chromatography to obtain 95 mg
1
reaction was followed by H NMR spectroscopy, which indicated
maximum conversion to the products at 24 h. The products (E)-
and (Z)-18 (80%, 3.7:1.0) were identified by comparison of gas
chromatogram and spectral properties of the sample from the
previous run. In addition to 10% starting material, ∼9% of an
unidentified product was also detected by gas chromatography (see
Supporting Information).
1
(95%) of 22 as a thick oil. Based on the H NMR, the E/Z ratio
was estimated as 8.0:1.0. 1H NMR (CDCl3): δ 5.57-5.30 (m, 2H),
4.00 (m), 3.91 (q, J ) 2.3 Hz) [together 1 H, R3Si-O-CH], 1.79
(d, J ) 2.3 Hz, 3H, R-Ct C-CH3), 1.66 (d, J ) 5.6 Hz, 3 H,
CHdC-CH3), 1.00 (2s, separated by ∼2 Hz, 6 H, R(CH3)2), 0.10
(2s, 9H, tBu in OTBS), 0.11 (s, 3H, Me in OTBS), 0.05 (s, 3H,
Me in OTBS). 13C NMR (CDCl3): δ 137.8, 120.1, 79.8, 79.3, 70.5,
40.9, 25.5, 25.4, 22.5, 22.1, 18.0, 2.9, -4.5; HRMS 266.2057 (M+•;
calcd for C16H30O4Si 266.2066).
Synthesis of 1-(But-3-enyloxy)-4-methoxybenzene (14). To a
stirred solution of 4-methoxyphenol (1 g, 8.06 mmol), 3-buten-1-
ol (0.99 g, 10.48 mmol), and triphenylphosphine (2.75 g, 10.48
mmol) in anhydrous THF (20 mL) was added diisopropylazodi-
carboxylate (2.12 g, 10.48 mmol) slowly at 0 °C. After the reaction
was stirred overnight at rt, the mixture was diluted with EtOAc
(20 mL) and water (20 mL) and separated. The crude compound
was extracted with EtOAc (3 × 20 mL), and the combined organic
layers were dried over Na2SO4. The resulting product was purified
by chromatography to afford 1.5 g (93%) of 14. 1H NMR (CDCl3):
δ 6.87-6.81 (m, 4 H, Ar), 5.94-5.86 (m, 1H, ROCH2CH2CHd
CH2), 5.18-5.09 (q, 2H, ROCH2CH2CHdCH2), 3.97-3.95 (t, J
) 7.0 Hz, 2 H, ROCH2CH2CHdCH2), 2.53-2.49 (m, 2 H,
ROCH2CH2CHdCCH2), 3.75 (s, 3 H, ArOCH3), 1.75-1.70 (d, J
) 5.0 Hz, 3 H, ROCH2CHdCHCH3). 13C NMR (CDCl3): δ 154.0,
153.2, 134.8, 117.1, 115.8, 114.8, 68.1, 55.9, 33.9.
Isomerization of 1-(But-3-enyloxy)-4-methoxybenzene (14). Gen-
eral procedure D (Table 3, entry 3). 1-(But-3-enyloxy)-4-methoxy-
benzene (30 mg, 0.168 mmol) was reacted with [(allyl)PdCl]2 (1.6
mg, 0.0042 mmol), (o-tol)3P (2.6 mg, 0.0084 mmol), AgOTf (2.2
mg, 0.0084 mmol), and CH2Cl2 at rt for 1 d. The resulting product
was purified by chromatography to afford 30 mg (>99%) of 19 as
a mixture of E- and Z-isomers with the starting material. Based on
1H NMR and GC, the conversion and E/Z ratio were estimated as
96% and 5.9:1.0 respectively. 1H NMR (CDCl3): δ 6.86-6.80 (m,
4 H, Ar), 5.84-5.80 (m, 1H, ROCH2CHdCHCH3, E and Z),
5.74-5.68 (m, 1 H, ROCH2CHdCHCH3, E and Z), 4.54-4.53 (d,
J ) 5.5 Hz, 2 H, ROCH2CHdCHCH3, Z), 4.53-4.39 (m, 2 H,
ROCH2CHdCHCH 3, E), 3.75 (s, 3 H, ArOCH3), 1.75-1.70 (d, J
) 5.0 Hz, 3 H, ROCH2CHdCHCH3). 13C NMR δ (CDCl3, E only):
Isomerization of 6-tert-Butyldimethylsiloxy)hex-1-ene (13) Us-
8a
ing Grubbs Second-Generation Catalyst.
Using the same
procedure and catalyst (10 mol %) aforementioned, the isomeriza-
tion of TBS-protected olefin 13 (11.2 mg, 0.052 mmol) was
checked. The crude product was analyzed by GC. See Supporting
Information for chromatograms.
Isomerization of 1-(But-3-enyloxy)-4-methoxybenzene (14) Us-
ing Grubbs Second-Generation Catalyst Shown in eq 1.8a The
starting olefin 14 (9.3 mg, 0.052 mmol) in anhydrous MeOH (0.8
mL) was treated with Grubbs second-generation catalyst (4.4 mg,
10 mol %). The resulting solution was stirred at 60 °C for 12 h.
After the solvent was evaporated in vacuo, the residue was filtered
on a silica pad, eluting with ether. The crude product was directly
analyzed by GC. See Supporting Information for chromatograms.
Isomerization of 1-Methylene-2,3,4-trihydronaphthalene (1) Us-
ing Grubbs Second-Generation Catalyst. Using the same procedure
and catalyst (10 mol %) aforementioned, the isomerization of olefin
1 (15.0 mg, 0.104 mmol) was checked. The crude product was
purified by short column chromatography and analyzed by 1H NMR.
Isomerization of 2-(3-(3-(Benzyloxy)phenyl)but-3-enyl)isoindo-
line-1,3-dione (3a) Using Grubbs Second-Generation Catalyst.
Using the same procedure and catalyst (10 mol %) aforementioned,
the isomerization of olefin 3a (10.0 mg, 0.0261 mmol) was checked.
J. Org. Chem. Vol. 74, No. 12, 2009 4571

Lim et al.
The crude product was purified by short column chromatography
and analyzed by H NMR.
(m, 2H, Ar), 6.36-6.33 (dt, 1H, J ) 12.0, 1.5 Hz, ROCHdCHEt),
5.32-5.27 (m, 1H, ROCHdCHEt), 3.75 (s, 3H, OMe), 2.05-1.99
(m, 2H, RCH2CH3), 1.05-0.98 (t, 3H, J ) 6.0 Hz, RCH2CH3).
1
Isomerization of 6-tert-Butyldimethylsiloxy)hex-1-ene (13) Us-
ing Ir(COE)2Cl]2/PCy3/NaBPh4 in CH2Cl2/Acetone (Scheme 2).4b,6d
Using the same procedure and catalyst (2 mol %) aforementioned,
the isomerization of TBS-protected olefin 13 (25.5 mg, 0.119 mmol)
was checked. After the resulting mixture was stirred at rt for 3 h,
most of the volatile materials were evaporated, and the crude
product was purified by column chromatography to get the
isomerized silylenolether tert-butyl(hex-1-enyloxy)dimethylsilane
Attempted Isomerization of 1-Methylene-2,3,4,5-trihydronaph-
thalene (1) Using Ir(COE)2Cl]2/PCy3/NaBPh4 in CH2Cl2/Acetone.4b,6d
Using the same procedure and catalyst (2 mol %) aforementioned,
the isomerization of olefin 1 (17.1 mg, 0.119 mmol) was checked.
The crude product was purified by short column chromatography
1
and analyzed by H NMR.
Attempted Isomerization of 2-(3-(3-(Benzyloxy)phenyl)but-3-
enyl)isoindoline-1,3-dione (3a) Using Ir(COE)2Cl]2/PCy3/NaBPh4
in CH2Cl2/Acetone.4b,6d Using the same procedure and catalyst (2
mol %) aforementioned, the isomerization of olefin 3a (22.8 mg,
0.060 mmol) was checked. The crude product was purified by short
1
(24.0 mg, 94%). The product was analyzed by H NMR and GC.
1H NMR (CDCl3): δ 6.21-6.18 (dt, 1H, J ) 12.0, 1.5 Hz,
nBuCHdCHOTBS), 4.97-4.95 (q, 1H, 3.8 Hz, nBuCHd
CHOTBS), 1.89-1.82 (m, 2H, nBu), 1.30-1.26 (m, 4H, nBu),
0.90-0.84 (m, 12 H, tBuSi and nBu), 0.10 (s, 6H, SiMe2).
Isomerization of 1-(But-3-enyloxy)-4-methoxybenzene (14) Us-
ing [Ir(COE)Cl]2/PCy3/NaBPh4 in CH2Cl2/Acetone.4b,6d In a nitrogen-
filled drybox, a dry flask was charged with [Ir(COE)2Cl]2 (1.1 mg,
0.0012 mmol), PCy3 (1.9 mg, 0.0068 mmol), and NaBPh4 (0.8 mg,
0.0029 mmol), and the mixture was dissolved in CH2Cl2/acetone
(0.52 mL, 25/1). After 5 min of stirring, the starting olefin 14 (21.2
mg, 0.119 mmol) in CH2Cl2 (0.5 mL) was added dropwise at rt.
After the resulting mixture was stirred for 3 h at rt, most of the
volatile materials were evaporated, and the crude product was
purified by column chromatography to yield the mixture of the
desired product (19) and further isomerized 1-(but-1-enyloxy)-4-
methoxybenzene (2-OPMP) (20.4 mg (96%), 19:2-OPMP ) 1.0:
1
column chromatography and analyzed by H NMR.
Acknowledgment. Financial assistance for this research by
NSF (CHE-0610349) and NIH (General Medical Sciences, R01
GM075107) is gratefully acknowledged. C.R.S. also thanks the
ACS Organic Division for a graduate fellowship sponsored by
The Schering Plough Corporation.
Supporting Information Available: Spectroscopic data (1H
and 13C NMR) and gas chromatographic traces of starting materials,
products, and crude isomerization products. This material is
available free of charge via the Internet at http://pubs.acs.org.
1
1
3.5 (based on H NMR)). The product was analyzed by H NMR
1
and GC. H NMR (CDCl3): δ 6.92-6.88 (m, 2H, Ar), 6.84-6.79
JO900180P
4572 J. Org. Chem. Vol. 74, No. 12, 2009