A general route for the stereoselective synthesis of (E)-(1-propenyl)phenyl esters by catalytic CC bond isomerization

Article abstract of DOI:10.1016/j.tet.2012.01.083

A general and efficient procedure for the stereoselective synthesis of (E)-(1-propenyl)phenyl esters from readily accessible allylphenols has been developed. The process involves a two-step sequence consisting of the initial acylation of the allylphenols with an acid chloride, followed by catalytic CC bond isomerization in the resulting allylphenyl esters. The latter step was performed in methanol at 80 °C using catalytic amounts (0.5 mol %) of the commercially available bis(allyl)-ruthenium(IV) dimer [{RuCl(μ-Cl) (η³:η³-C₁₀H₁₆)} ₂] (C₁₀H₁₆=2,7-dimethylocta-2,6-diene-1,8-diyl) . Reactions proceeded in high yields (68-93%) and short times (4-9 h) with complete E-selectivity.

Full text of DOI:10.1016/j.tet.2012.01.083

Tetrahedron 68 (2012) 2611e2620
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Tetrahedron
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A general route for the stereoselective synthesis of (E)-(1-propenyl)phenyl esters
by catalytic C]C bond isomerization
ꢀ
*
*
Alba E. Díaz-Alvarez, Pascale Crochet , Victorio Cadierno
ꢀ
ꢀ
ꢀ
Departamento de Química Organica e Inorganica, IUQOEM (Unidad asociada al CSIC), Universidad de Oviedo, Julian Clavería 8, 33006 Oviedo, Spain
a r t i c l e i n f o
a b s t r a c t
Article history:
A general and efficient procedure for the stereoselective synthesis of (E)-(1-propenyl)phenyl esters from
readily accessible allylphenols has been developed. The process involves a two-step sequence consisting
of the initial acylation of the allylphenols with an acid chloride, followed by catalytic C]C bond isom-
erization in the resulting allylphenyl esters. The latter step was performed in methanol at 80 ꢀC using
Received 18 October 2011
Received in revised form 25 January 2012
Accepted 30 January 2012
Available online 4 February 2012
catalytic amounts (0.5 mol %) of the commercially available bis(allyl)-ruthenium(IV) dimer [{RuCl(m-
Cl)(h3
:
h
3-C10H16)}2] (C10H16¼2,7-dimethylocta-2,6-diene-1,8-diyl). Reactions proceeded in high yields
Dedicated to Dr. Hubert Le Bozec on the
occasion of his 60th birthday
(68e93%) and short times (4e9 h) with complete E-selectivity.
Ó 2012 Elsevier Ltd. All rights reserved.
Keywords:
Homogeneous catalysis
Isomerization
Allylic compounds
Ruthenium
Esters
1. Introduction
advances, there is still a high request for readily available and effi-
cient systems providing the desired 1-propenyl products in a ster-
eoselective manner under mild conditions. Indeed, stereoselectivity
is a key issue in the industrial isomerization of several allylbenzene
derivatives, such as estragole, eugenol or safrole, where only the E-
products are marketed due to the toxic character and unpleasant
organoleptic properties of the corresponding Z-isomers.9t
The catalytic isomerization of olefins is a fundamental reaction in
organic chemistry with widespread academic and industrial appli-
cations.1 Transformation of allylbenzenes into the corresponding
1-propenyl derivatives is a clear example of the synthetic utility of
this textbook reaction since the latter are common starting mate-
rials in the flavour and fragrance industries,2 as well as advanced
intermediates for the preparation of a large variety of biologically
active compounds.3 Traditionally, these isomerization reactions
have been performed with alkali hydroxides in alcoholic media
under high temperature regimes.4 However, these methods usually
suffer from drawbacks like long reactions times, low conversions,
limited tolerance to functional groups and tedious post-synthetic
work-up. During the last years, more convenient approaches
based on the use of heterogeneous and homogeneous catalysts have
been developed.5,6 In particular, since the pioneering works by
Shimizu and Blum on the isomerization of allylbenzene using Natta-
type7 and Ru-, Rh-, and Ir-based catalysts,8 respectively, a wide array
of transition metal complexes has proven effective for the C]C bond
migration of allyl-aromatic compounds.9 However, despite these
Recently, in the context of our studies on the catalytic isomeri-
zation of functionalized allylic compounds,10 we have brought to
light different organometallic ruthenium complexes able to isom-
erize estragole into anethole with E-selectivities ꢁ99%.11 Among
them, the bis(allyl)-ruthenium(IV) dimer [{RuCl(m : -
-Cl)(h3 h3
C10H16)}2] (C10H16¼2,7-dimethylocta-2,6-diene-1,8-diyl)12 de-
serves to be highlighted due to its outstanding activity and acces-
sibility (Scheme 1).11b In fact, it can be purchased from commercial
suppliers (SigmaeAldrich or Strem Chemicals) or easily prepared
by simple reaction of RuCl3$nH2O with isoprene.13
The remarkable E-selectivity shown by complex [{RuCl(
m-
Cl)(h3 3-C10H16)}2] in this industrially relevant transformation
:h
prompted us to undertake a systematic evaluation of its catalytic
behaviour towards related allylbenzene derivatives. As a first result
of these studies, herein we disclose a general and efficient pro-
cedure for the stereoselective synthesis of (E)-(1-propenyl)phenyl
esters C starting from readily available allylphenols A, via initial
acylation of the OH unit of A with an acid chloride and subsequent
* Corresponding authors. Tel.: þ34 985 103 453; fax: þ34 985 103 446; e-mail
addresses: crochetpascale@uniovi.es (P. Crochet), vcm@uniovi.es (V. Cadierno).
0040-4020/$ e see front matter Ó 2012 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2012.01.083

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A.E. Díaz-Alvarez et al. / Tetrahedron 68 (2012) 2611e2620
the alcohol units was readily evidenced by the appearance of a low-
field carbon resonance at 164.5e176.1 ppm, and a strong absorption
band at 1733e1761 cmꢂ1, in the 13C{1H} NMR and IR spectra, re-
spectively, characteristic of ester RCO2-moieties.
Scheme 1. Highly selective estragole to trans-anethole isomerization using complex
[{RuCl(m :h
-Cl)(h3 3-C10H16)}2] as catalyst.
stereoselective C]C bond isomerization in the resulting allyl-
phenyl esters B (Scheme 2). Note that, although compounds of type
C widely occur in nature and present interesting biological activi-
ties,14 to date no convenient routes of access have been described in
the literature.15 In fact, some representatives of this family of
compounds have shown relevant anti-inflammatory,14q anti-
malarial,14p,r anti-bacterial14p,r and anti-fungal14p,r properties, as
well as insecticidal14n and oestrogenic activities.14k
Scheme 3. Synthesis of the allylphenyl esters 6e10(aed).
Once synthesized, the ability of complex [{RuCl(m : -
-Cl)(h3 h3
C10H16)}2] to promote the isomerization of the allyl unit in these
compounds was then evaluated. Optimization of the reaction
conditions was carried out using 2-allyl-6-methylphenyl pro-
pionate (6a) as model compound. In our previous studies on the
estragole to anethole isomerization (Scheme 1), dependence of the
activity of complex [{RuCl(m :h
-Cl)(h3 3-C10H16)}2] with the solvent
was evidenced.11b Consequently, our initial efforts focused on
finding the optimal solvent for the process. To this end, we con-
ducted a series of experiments in different reaction media. They
were performed at 80 ꢀC with 2 mmol of 6a, a ruthenium loading of
1 mol % and 0.5 mL of the appropriate solvent (4 M solutions of 6a),
monitoring the course of the reactions by GC analyses of aliquots.
The results obtained are collected in Table 1.
Scheme 2. General route for the stereoselective synthesis of (E)-(1-propenyl)phenyl
esters C.
2. Results and discussion
Our investigations started with the preparation of a varied
family of allylphenyl esters 6e10(aed) showing a mutual 1,2-, 1,3-
or 1,4-disposition of the ester and allyl functional groups (Scheme
3). These species were generated by acylation of the commer-
cially available, or readily accessible, allylphenols 1e5 with pro-
pionyl chloride, isobutyryl chloride, 3-methyl-butyryl chloride and
benzoyl chloride. Reactions, which were routinely performed in
dichloromethane at rt in the presence of catalytic amounts of 4-
dimethylaminopyridine (DMAP) and triethylamine as HCl scaven-
ger, delivered the desired allylphenyl esters 6e10(aed) in 70e91%
isolated yield after appropriate chromatographic purification.
Characterization of compounds 6e10(aed) was straightforward
following their HRMS, IR and 1H and 13C{1H} NMR data (details are
given in Experimental section). In particular, selective acylation of
As a general trend, the efficiency of the process increased with
the polarity of the solvent due to the easier chloride bridge cleavage
and ruthenium-chloride bond dissociation in [{RuCl(m : -
-Cl)(h3 h3
C10H16)}2], key processes to generate the required vacant sites on
the metal. However, we must note that, although acetonitrile was
one of the most polar solvents used, the conversion obtained in this
medium was particularly low (28% after 4 h, entry 7). This is
probably due to its capacity to coordinate on the active species,
competing then with the substrate. In particular, the best results
were obtained in methanol and ethanol where 95e96% conversions
of 6a into its 1-propenyl isomer 11a were reached after 4 h of
heating (>90% after only 1 h; entries 1 and 2). The higher activities
observed in these solvents versus water or THF (69e83% yield after
4 h; entries 4 and 5) can be attributed to their ability to generate

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A.E. Díaz-Alvarez et al. / Tetrahedron 68 (2012) 2611e2620
2613
Table 1
Table 2
Isomerization of the allylphenyl ester 6a into the (E)-(1-propenyl)phenyl ester 11a
Isomerization of the allylphenyl esters 6e10(aed) into the (E)-(1-propenyl)phenyl
catalyzed by complex [{RuCl(
m
-Cl)(h3
:h
3-C10H16)}2] in different solventsa
ester 11e15(aed) catalyzed by complex [{RuCl(
m
-Cl)(h3 3-C10H16)}2] in methanola
:h
Yieldb (%)
Entry
Solvent
Yield after 1 hb (%)
Yield after 4 hb (%)
Entry
Solvent
Time (h)
Product
1
2
3
4
5
6
7
8
MeOH
EtOH
Glycerol
Water
THF
Toluene
Acetonitrile
1,2-Dichloroethane
91
90
70
78
61
30
10
12
96
95
77
83
69
57
28
43
1
2
3
4
5
6
7
8
6a
6b
6c
6d
7a
7b
7c
7d
8a
8b
8c
8d
9a
9b
9c
4
4
4
7
4
4
4
4
4
4
4
4
9
4
7
4
4
4
4
4
11a
11b
11c
11d
12a
12b
12c
12d
13a
13b
13c
13d
14a
14b
14c
14d
15a
15b
15c
15d
96 (85)
88 (76)
94 (84)
83 (70)
99 (87)
96 (84)
97 (88)
97 (90)
87 (74)
92 (86)
88 (79)
94 (87)
86 (79)
88 (78)
97 (84)
99 (88)
91 (83)
95 (87)
98 (89)
94 (80)
9
a
Reactions performed under N2 atmosphere at 80 ꢀC using 2 mmol of 6a (4 M
solutions). [Substrate]/[Ru] ratio¼100:1.
10
11
12
13
14
15
16
17
18
19
20
b
Determined by GC. Formation of the corresponding Z-isomer not observed.
catalytically active ruthenium-hydride species, via a
b-hydride
9d
10a
10b
10c
10d
elimination process on the corresponding Ru-alkoxide in-
termediates, thus suggesting that the C]C bond migration process
proceeds through a classical ‘hydride mechanism’. Although RueH
species can also be easily formed from glycerol, the use of this
emerging green solvent led to a poorer conversion (77% after 4 h;
entry 3).16 The high viscosity of glycerol, which provokes poor
substrate diffusion in the medium, could be responsible of this
disappointing result.
a
Reactions performed in methanol under N2 atmosphere at 80 ꢀC using 2 mmol
of the corresponding allylphenyl ester 6e10(aed) (4 M solutions). [Substrate]/[Ru]
ratio¼100:1.
b
Determined by GC. Isolated yields after appropriate chromatographic work-up
are given in parentheses. Formation of the corresponding Z-isomers not observed.
Remarkably, regardless of the solvent employed, formation of
a single reaction product was in all cases observed by GC, suggesting
that the migration of the C]C bond in 6a proceeds in a complete
stereoselective manner. This point was unambiguously confirmed
by running a 1H NMR spectrum of one reaction crude after solvent
removal (entry 1), which showed a unique set of signals for the 1-
propenyl product 11a. The mutual coupling constant observed for
the olefinic eCH]CHMe protons (15.7 Hz) clearly indicated the
formation of the thermodynamically more stable E-isomer.17 In or-
der to improve the efficiency of the process, some experiments were
also performed in methanol at different concentrations of the sub-
strate (from 1 M to 5 M). However, while no marked differences in
activity were observed under more concentrated conditions (5 M),
the use of more diluted solutions of 6a slowed the reaction con-
siderably (e.g., only 43% of conversion after 4 h was observed with
a 1 M solution). Much poorer results were also obtained lowering
the reaction temperature (e.g., at 50 ꢀC only 8% of conversion was
observed after 4 h) or the ruthenium loadings (e.g., using 0.1 mol %
NMR spectroscopic techniques (details are given in Experimental
section; copies of the 1H and 13C{1H} are included in
Supplementary data). A characteristic AB system of quartets for the
olefinic protons of the eCH]CHMe units was found in their 1H
NMR spectra, the mutual coupling constants observed (ca. 15.7 Hz)
being in complete accord with the proposed E-alkene geometry.
At this point, we must notice that an alternative route to (E)-(1-
propenyl)phenyl esters 11e15(aed) involving the reverse reactions
sequence, i.e., initial C]C bond migration in allylphenols 1e5 fol-
lowed by acylation of the resulting (1-propenyl)phenols, proved
inoperative using complex [{RuCl(
of complicated mixtures of products was observed upon treatment
of 1e5 with [{RuCl(
-Cl)(h3 3-C10H16)}2] (0.5 mol %) in methanol at
m :h
-Cl)(h3 3-C10H16)}2]. Formation
m
:h
80 ꢀC. Only in the case of chavicol (5) one major reaction product
could be isolated in pure form, and identified as the known (E)-
diphenol 16 (Scheme 4).18 Compound 16 formally results from the
self-coupling of two molecules of the isomerized 4-(1-propenyl)
phenol, a process with precedents in acid media.18,19 The high Lewis-
of [{RuCl(m :h
-Cl)(h3 3-C10H16)}2] only 57% of conversion was ob-
served after 4 h of heating at 80 ꢀC). However, we must note that, in
all these reactions, the E-isomer was again exclusively formed.
Gratifyingly, as observed for 6a, isomerization of the other
acid character of the ruthenium(IV) centres in [{RuCl(m : -
-Cl)(h3 h3
C10H16)}2] may be therefore responsible of this unexpected result.
allylphenyl esters synthesized 6be10d with complex [{RuCl(
m-
Cl)(h3 3-C10H16)}2] (0.5 mol %) also proceeded with complete E-
:
h
selectivity, thus proving the wide scope of this new synthetic
methodology (Table 2). Reactions, which were performed in
methanol at 80 ꢀC, led to the corresponding (E)-(1-propenyl)phenyl
esters 11be15d in more than 83% yield by GC (formation of Z-iso-
mers not observed by GC). No notable influence of the substitution
pattern of the arene ring on the reaction rates was noticed, most of
the reactions being completed within 4 h. Solvent removal and
appropriate chromatographic work-up on silica gel provided ana-
lytically pure samples of all these compounds in high isolated yields
(70e90%), which were fully characterized by means of high-
resolution mass spectrometry and standard IR and multinuclear
Scheme 4. Synthesis of the diphenol 16 from chavicol.

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A.E. Díaz-Alvarez et al. / Tetrahedron 68 (2012) 2611e2620
Finally, to further demonstrate the synthetic utility of our route
distilled under nitrogen before use. All reagents were obtained
to (E)-(1-propenyl)phenyl esters, a series of allylphenols 17e21
containing different functionalities on the aromatic ring were
synthesized, through a Claisen rearrangement of the corresponding
allylphenyl ethers,22 and subsequently transformed into the esters
22ae26a by treatment with propionyl chloride (synthetic details
and characterization data for these new compounds are given in
Experimental section). As shown in Scheme 5, with the exception of
2-allyl-4-methylsulfanylphenyl propionate (26a), which remained
unaltered,23 all these substrates underwent a clean and E-selective
isomerization of their C]C bonds in the presence of complex
from commercial suppliers and used without further purification,
with the exception of compounds [{RuCl(m :h
-Cl)(h3 3-C10H16)}2],13
3-allylphenol (3),20 4-allylphenol (chavicol; 5),21 2,4-diallyl-6-
methoxyphenol (17),24 2-allyl-6-chlorophenol (18),25 2-acetyl-6-
allylphenol (19),26 2-allyl-4-chlorophenol (20)25 and 2-allyl-4-
methylsulfanylphenol (21),27 which were prepared by following
the methods reported in the literature. GC measurements were
made on a Hewlett-Packard HP6890 equipment using a Supelco
Beta-DexÔ 120 column (30 m length; 250 mm diameter). Flash
chromatography was performed using Merck silica gel 60
(230e400 mesh). Melting points were determined in a Gallenkamp
apparatus and are uncorrected. Infrared spectra were recorded on
a PerkineElmer 1720-XFT spectrometer. 1H and 13C{1H} NMR
spectra were recorded on Bruker DPX-300 (300/75 MHz) or Bruker
[{RuCl(m :h
-Cl)(h3 3-C10H16)}2] (0.5 mol %) under the standard re-
action conditions (MeOH, 80 ꢀC), leading to the novel (E)-(1-
propenyl)phenyl esters 27ae30a in 68e93% isolated yield. The
selective E-isomerization of the two allylic units of 22a clearly re-
flects outstanding potential of [{RuCl(
m
-Cl)(h3
:h
3-C10H16)}2].
AV-400 (400/100 MHz) instruments. The chemical shift values (d)
are given in parts per million and are referred to the residual peak
of the deuterated solvent used (CDCl3). DEPT experiments have
been carried out for all the compounds reported. High-resolution
mass spectra (HRMS) were provided by the Mass Spectrometry
Service of Instituto de Investigaciones Químicas (IIQ-CSIC, Seville).
4.2. General procedure for the synthesis of allylphenyl esters
6e10(aed) and 22ae26a
To a solution of the corresponding allylphenol 1e5 or 18e21
(10 mmol) in 20 mL of CH2Cl2, NEt3 (20 mmol), dimethylamino-
pyridine (DMAP) (1 mmol) and the appropriate acid chloride
(11 mmol) were added at 0 ꢀC. The reaction mixture was allowed to
reach the rt and stirred overnight at this temperature. The volatiles
were then removed under reduced pressure, and the resulting oily
residue dissolved in water and extracted with Et2O (4ꢃ30 mL). The
combined organic phases were dried over MgSO4, filtered and
evaporated to dryness under reduced pressure. Final purification by
column chromatography over SiO2, using a mixture hexanes/Et2O
(85:15) as eluent, afforded the desired allylphenyl esters
6e10(aed) and 22ae26a. Characterization data for these com-
pounds are as follows (copies of the 1H and 13C{1H} spectra are
included in Supplementary data):
Scheme 5. Synthesis and isomerization of the allylphenyl esters 22ae26a. Reagents
and conditions: (i) EtC(]O)Cl (1.1 equiv), Et3N (2 equiv), DMAP (10 mol %), CH2Cl2, rt,
overnight, 73e88% yield; (ii) [{RuCl(
9 h, 68e93% yield.
m :h
-Cl)(h3 3-C10H16)}2] (0.5 mol %), MeOH, 80 ꢀC,
4.2.1. 2-Allyl-6-methylphenyl propionate (6a). Colourless oil. Yield:
84% (1.716 g). IR (neat):
NMR (CDCl3):
n
¼1639 (m, C]C), 1757 (s, C]O) cmꢂ1. 1H
d
¼1.34 (t, J¼7.6 Hz, 3H, CH2CH3), 2.18 (s, 3H, CH3),
3. Conclusions
2.65 (q, J¼7.6 Hz, 2H, CH2CH3), 3.30 (d, J¼6.6 Hz, 2H, CH2CH]CH2),
5.06e5.14 (m, 2H, CH2CH]CH2), 5.86e6.00 (m, 1H, CH2CH]CH2),
In summary, a general and efficient method of synthesis of (E)-
(1-propenyl)phenyl esters starting from readily accessible allyl-
phenols has been developed. The process involves the initial acyl-
ation of the allylphenols, followed by catalytic C]C bond
isomerization in the resulting allylphenyl esters. The key isomeri-
zation step proceeded with complete E-selectivity in the presence
7.10e7.14 (m, 3H, CHarom). 13C{1H} NMR (CDCl3):
d
¼9.4 and 16.4 (s,
CH3), 27.5 (s, CH2CH3), 34.8 (s, CH2CH]CH2), 116.1 (s, CH2CH]CH2),
125.9, 127.8 and 129.1 (s, CHarom), 130.5, 132.1 and 147.8 (s, Carom),
136.1 (s, CH2CH]CH2), 172.2 (s, C]O). HRMS (EI): m/z¼204.1154,
calcd for C13H16O2: 204.1150.
of catalytic amounts of the commercially available dimer [{RuCl(m-
4.2.2. 2-Allyl-6-methylphenyl isobutyrate (6b). Pale yellow oil. Yield:
Cl)(h3
:h
3-C10H16)}2] (C10H16¼2,7-dimethylocta-2,6-diene-1,8-diyl).
80% (1.746 g). IR (neat):
NMR (CDCl3):
n
¼1639 (m, C]C), 1755 (s, C]O) cmꢂ1. 1H
Following this route, a large number of (E)-(1-propenyl)phenyl
esters, including the naturally occurring ones 14b and 15aec,14a,c,h,r
could be selectively synthesized in high yields. Overall, the results
reported herein represent a new example of the utility of the
d
¼1.41 (d, J¼7.0 Hz, 6H, CH(CH3)2), 2.20 (s, 3H, CH3),
2.91 (sept, J¼7.0 Hz, 1H, CH(CH3)2), 3.30 (d, J¼6.5 Hz, 2H, CH2CH]
CH2), 5.08e5.14 (m, 2H, CH2CH]CH2), 5.89e6.03 (m, 1H, CH2CH]
CH2), 7.11e7.15 (m, 3H, CHarom).13C{1H} NMR (CDCl3):
d¼16.4 (s, CH3),
bis(allyl)-ruthenium(IV) complex [{RuCl(
m :h
-Cl)(h3 3-C10H16)}2] in
19.1 (s, CH(CH3)2), 34.2 (s, CH(CH3)2), 34.6 (s, CH2CH]CH2), 116.1 (s,
CH2CH]CH2), 125.9, 127.8 and 129.1 (s, CHarom), 130.5, 132.1 and 147.8
(s, Carom), 136.1 (s, CH2CH]CH2), 174.7 (s, C]O). HRMS (EI): m/
z¼218.1302, calcd for C14H18O2: 218.1307.
synthetic organic chemistry.12
4. Experimental section
4.1. General
4.2.3. 2-Allyl-6-methylphenyl-3-methyl butanoate (6c). Colourless
oil. Yield: 77% (1.788 g). IR (neat):
cmꢂ1. 1H NMR (CDCl3):
¼1.11 (d, J¼6.9 Hz, 6H, CH(CH3)2), 2.19 (s,
3H, CH3), 2.19e2.40 (m, 1H, CH(CH3)2), 2.51 (d, J¼7.0 Hz, 2H,
n
¼1639 (m, C]C), 1757 (s, C]O)
Synthetic procedures were performed under an atmosphere of
dry nitrogen. Solvents were dried by standard methods and
d

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A.E. Díaz-Alvarez et al. / Tetrahedron 68 (2012) 2611e2620
2615
CH2CH(CH3)2), 3.29 (d, J¼6.6 Hz, 2H, CH2CH]CH2), 5.06e5.13 (m,
2H, CH2CH]CH2), 5.86e6.00 (m, 1H, CH2CH]CH2), 7.09e7.14 (m,
CH2CH3), 3.43 (d, J¼6.7 Hz, 2H, CH2CH]CH2), 5.10e5.17 (m, 2H,
CH2CH]CH2), 5.95e6.04 (m, 1H, CH2CH]CH2), 6.96e7.33 (m, 4H,
3H, CHarom). 13C{1H} NMR (CDCl3):
d
¼17.0 (s, CH3), 23.0 (s,
CHarom). 13C{1H} NMR (CDCl3):
d¼9.1 (s, CH3), 27.8 (s, CH2CH3), 39.9
CH(CH3)2), 26.0 (s, CH(CH3)2), 35.2 (s, CH2CH]CH2), 43.5 (s,
CH2CH(CH3)2), 116.2 (s, CH2CH]CH2), 126.3, 128.2 and 129.5 (s,
CHarom), 130.9, 132.5 and 142.3 (s, Carom), 136.5 (s, CH2CH]CH2),
171.2 (s, C]O). HRMS (EI): m/z¼232.1465, calcd for C15H20O2:
232.1463.
(s, CH2CH]CH2), 116.4 (s, CH2CH]CH2), 119.3, 121.7, 126.0 and
129.3 (s, CHarom), 136.8 (s, CH2CH]CH2), 141.8 and 150.9 (s, Carom),
173.0 (s, C]O). HRMS (EI): m/z¼190.0995, calcd for C12H14O2:
190.0994.
4.2.10. 3-Allylphenyl isobutyrate (8b). Colourless oil. Yield: 80%
4.2.4. 2-Allyl-6-methylphenyl benzoate (6d). Yellow oil. Yield: 82%
(1.634 g). IR (neat):
(CDCl3):
n
¼1639 (m, C]C), 1757 (s, C]O) cmꢂ1. 1H NMR
(2.069 g). IR (neat):
(CDCl3):
n
¼1639 (m, C]C), 1737 (s, C]O) cmꢂ1. 1H NMR
d
¼1.36 (d, J¼7.0 Hz, 6H, CH(CH3)2), 2.83 (sept, J¼7.0 Hz, 1H,
d
¼2.25 (s, 3H, CH3), 3.36 (d, J¼6.6 Hz, 2H, CH2CH]CH2),
CH(CH3)2), 3.43 (d, J¼6.7 Hz, 2H, CH2CH]CH2), 5.11e5.17 (m, 2H,
5.02e5.89 (m, 2H, CH2CH]CH2), 5.90e6.03 (m, 1H, CH2CH]CH2),
CH2CH]CH2), 5.93e6.07 (m, 1H, CH2CH]CH2), 6.95e7.33 (m, 4H,
7.17e8.30 (m, 8H, CHarom). 13C{1H} NMR (CDCl3):
d
¼16.5 (s, CH3),
CHarom). 13C{1H} NMR (CDCl3):
d
¼18.9 (s, CH(CH3)2), 34.2 (s,
34.9 (s, CH2CH]CH2), 116.2 (s, CH2CH]CH2), 126.7, 127.9, 128.7,
129.2, 130.2 and 133.6 (s, CHarom), 129.3, 130.8, 132.3 and 148.0 (s,
Carom), 136.1 (s, CH2CH]CH2), 164.5 (s, C]O). HRMS (EI): m/
z¼252.1158, calcd for C17H16O2: 252.1150.
CH(CH3)2), 39.9 (s, CH2CH]CH2), 116.3 (s, CH2CH]CH2), 119.2,
121.6, 125.9 and 129.2 (s, CHarom), 136.8 (s, CH2CH]CH2), 141.7 and
151.0 (s, Carom), 175.6 (s, C]O). HRMS (EI): m/z¼204.1148, calcd for
C13H16O2: 204.1150.
4.2.5. 2-Allylphenyl propionate (7a). Colourless oil. Yield: 78%
4.2.11. 3-Allylphenyl-3-methyl butanoate (8c). Colourless oil. Yield:
(1.483 g). IR (neat):
(CDCl3):
n
¼1639 (m, C]C), 1761 (s, C]O) cmꢂ1. 1H NMR
79% (1.724 g). IR (neat):
NMR (CDCl3):
CH(CH3)2), 2.47 (d, J¼7.0 Hz, 2H, CH2CH(CH3)2), 3.44 (d, J¼6.7 Hz,
2H, CH2CH]CH2), 5.10e5.17 (m, 2H, CH2CH]CH2), 5.95e6.04 (m,
1H, CH2CH]CH2), 6.95e7.36 (m, 4H, CHarom). 13C{1H} NMR (CDCl3):
n
¼1639 (m, C]C), 1757 (s, C]O) cmꢂ1. 1H
d
¼1.31 (t, J¼7.6 Hz, 3H, CH3), 2.63 (q, J¼7.6 Hz, 2H,
d
¼1.10 (d, J¼6.6 Hz, 6H, CH(CH3)2), 2.21e2.35 (m, 1H,
CH2CH3), 3.32 (d, J¼6.5 Hz, 2H, CH2CH]CH2), 5.05e5.12 (m, 2H,
CH2CH]CH2), 5.87e6.00 (m, 1H, CH2CH]CH2), 7.05e7.28 (m, 4H,
CHarom). 13C{1H} NMR (CDCl3):
d
¼9.6 (s, CH3), 28.1 (s, CH2CH3), 35.0
(s, CH2CH]CH2), 116.2 (s, CH2CH]CH2), 122.8, 126.5, 127.8 and
130.7 (s, CHarom), 132.3 and 149.4 (s, Carom), 136.3 (s, CH2CH]CH2),
173.2 (s, C]O). HRMS (EI): m/z¼190.0992, calcd for C12H14O2:
190.0994.
d
¼22.4 (s, CH(CH3)2), 25.9 (s, CH(CH3)2), 39.9 (s, CH2CH]CH2), 43.4
(s, CH2CH(CH3)2), 116.3 (s, CH2CH]CH2), 119.3, 121.7, 126.0 and
129.3 (s, CHarom), 136.8 (s, CH2CH]CH2), 141.8 and 150.8 (s, Carom),
171.6 (s, C]O). HRMS (EI): m/z¼218.1311, calcd for C14H18O2:
218.1307.
4.2.6. 2-Allylphenyl isobutyrate (7b). Colourless oil. Yield: 89%
(1.818 g). IR (neat):
(CDCl3):
n
¼1639 (m, C]C), 1756 (s, C]O) cmꢂ1. 1H NMR
4.2.12. 3-Allylphenyl benzoate (8d). Colourless oil. Yield: 74%
d
¼1.37 (d, J¼7.0 Hz, 6H, CH(CH3)2), 2.86 (sept, J¼7.0 Hz, 1H,
(1.763 g). IR (neat):
(CDCl3):
n
¼1638 (m, C]C), 1738 (s, C]O) cmꢂ1. 1H NMR
CH(CH3)2), 3.33 (d, J¼6.5 Hz, 2H, CH2CH]CH2), 5.05e5.13 (m, 2H,
d
¼3.47 (d, J¼6.7 Hz, 2H, CH2CH]CH2), 5.13e5.19 (m, 2H,
CH2CH]CH2), 5.87e6.00 (m, 1H, CH2CH]CH2), 7.04e7.31 (m, 4H,
CH2CH]CH2), 5.96e6.07 (m, 1H, CH2CH]CH2), 7.10e7.70 (m, 7H,
CHarom). 13C{1H} NMR (CDCl3):
d¼19.0 (s, CH(CH3)2), 34.2 (s,
CHarom), 8.23 (m, 2H, CHarom). 13C{1H} NMR (CDCl3):
d¼40.0 (s,
CH(CH3)2), 34.4 (s, CH2CH]CH2), 116.2 (s, CH2CH]CH2), 122.3,
126.0, 127.4 and 130.4 (s, CHarom), 131.9 and 149.0 (s, Carom), 135.9 (s,
CH2CH]CH2), 175.4 (s, C]O). HRMS (EI): m/z¼204.1149, calcd for
C13H16O2: 204.1150.
CH2CH]CH2), 116.4 (s, CH2CH]CH2), 119.4, 121.8, 126.2, 128.6,
129.4, 130.2 and 133.6 (s, CHarom), 129.7, 141.9 and 151.1 (s, Carom),
136.8 (s, CH2CH]CH2), 165.2 (s, C]O). HRMS (EI): m/z¼238.0998,
calcd for C16H14O2: 238.0994.
4.2.7. 2-Allylphenyl-3-methyl butanoate (7c). Colourless oil. Yield:
4.2.13. 4-Allyl-2-methoxyphenyl propionate (9a).29 White solid.
81% (1.768 g). IR (neat):
NMR (CDCl3):
n
¼1639 (m, C]C), 1760 (s, C]O) cmꢂ1. 1H
Yield: 85% (1.872 g). Mp: 44e45 ꢀC. IR (neat):
n
¼1639 (m, C]C),
d
¼1.12 (d, J¼6.6 Hz, 6H, CH(CH3)2), 2.28 (m, 1H,
1761 (s, C]O) cmꢂ1. 1H NMR (CDCl3):
d
¼1.30 (t, J¼7.6 Hz, 3H, CH3),
CH(CH3)2), 2.49 (d, J¼7.2 Hz, 2H, CH2CH(CH3)2), 3.36 (d, J¼6.5 Hz,
2H, CH2CH]CH2), 5.05e5.12 (m, 2H, CH2CH]CH2), 5.89e5.98 (m,
1H, CH2CH]CH2), 7.07e7.22 (m, 4H, CHarom). 13C{1H} NMR (CDCl3):
2.63 (q, J¼7.6 Hz, 2H, CH2CH3), 3.40 (d, J¼6.7 Hz, 2H, CH2CH]CH2),
3.83 (s, 3H, OCH3), 5.11e5.17 (m, 2H, CH2CH]CH2), 5.93e6.04 (m,
1H, CH2CH]CH2), 6.79e6.99 (m, 3H, CHarom). 13C{1H} NMR (CDCl3):
d
¼22.9 (s, CH(CH3)2), 26.2 (s, CH(CH3)2), 35.0 (s, CH2CH]CH2), 43.7
d
¼9.6 (s, CH3), 27.8 (s, CH2CH3), 40.5 (s, CH2CH]CH2), 56.2 (s,
(s, CH2CH(CH3)2), 116.7 (s, CH2CH]CH2), 122.8, 126.5, 127.8 and
130.8 (s, CHarom), 132.3 and 149.4 (s, Carom), 136.3 (s, CH2CH]CH2),
171.8 (s, C]O). HRMS (EI): m/z¼218.1310, calcd for C14H18O2:
218.1307.
OCH3), 113.1, 121.1 and 122.9 (s, CHarom), 116.5 (s, CH2CH]CH2),
137.5 (s, CH2CH]CH2), 138.5, 149.4 and 151.3 (s, Carom), 173.1 (s, C]
O). HRMS (EI): m/z¼220.1093, calcd for C13H16O3: 220.1099.
4.2.14. 4-Allyl-2-methoxyphenyl isobutyrate (9b).30 Colourless oil.
4.2.8. 2-Allylphenyl benzoate (7d).28 Colourless oil. Yield: 84%
(2.001 g). IR (neat):
(CDCl3):
Yield: 84% (1.968 g). IR (neat):
n
¼1639 (m, C]C), 1761 (s, C]O)
n
¼1639 (m, C]C), 1736 (s, C]O) cmꢂ1. 1H NMR
cmꢂ1 1H NMR (CDCl3):
.
d
¼1.35 (d, J¼7.0 Hz, 6H, CH(CH3)2), 2.86
d
¼3.41 (d, J¼6.6 Hz, 2H, CH2CH]CH2), 5.03e5.10 (m, 2H,
(sept, J¼7.0 Hz, 1H, CH(CH3)2), 3.41 (d, J¼6.7 Hz, 2H, CH2CH]CH2),
3.83 (s, 3H, OCH3), 5.10e5.16 (m, 2H, CH2CH]CH2), 5.95e6.04 (m,
1H, CH2CH]CH2), 6.77e6.97 (m, 3H, CHarom). 13C{1H} NMR (CDCl3):
CH2CH]CH2), 5.90e6.04 (m, 1H, CH2CH]CH2), 7.23e7.34 (m, 4H,
CHarom), 7.53e7.70 (m, 3H, CHarom), 8.26 (m, 2H, CHarom). 13C{1H}
NMR (CDCl3):
d
¼35.1 (s, CH2CH]CH2), 116.7 (s, CH2CH]CH2),
d
¼19.1 (s, CH(CH3)2), 34.0 (s, CH(CH3)2), 40.1 (s, CH2CH]CH2), 55.8
122.9, 126.7, 127.9, 129.0, 130.6, 130.8 and 134.0 (s, CHarom), 129.9,
132.6 and 149.6 (s, Carom), 136.2 (s, CH2CH]CH2), 165.4 (s, C]O).
HRMS (EI): m/z¼238.0995, calcd for C16H14O2: 238.0994.
(s, OCH3), 112.8, 120.7 and 122.5 (s, CHarom), 116.1 (s, CH2CH]CH2),
137.1 (s, CH2CH]CH2), 138.2, 138.7 and 151.0 (s, Carom), 175.4 (s, C]
O). HRMS (EI): m/z¼234.1257, calcd for C14H18O3: 234.1256.
4.2.9. 3-Allylphenyl propionate (8a). Colourless oil. Yield: 76%
4.2.15. 4-Allyl-2-methoxyphenyl-3-methyl butanoate (9c).31 Colo-
(1.445 g). IR (neat):
(CDCl3):
n
¼1639 (m, C]C), 1761 (s, C]O) cmꢂ1. 1H NMR
urless oil. Yield: 87% (2.160 g). IR (neat):
n¼1639 (m, C]C), 1761 (s,
d¼1.30 (t, J¼7.5 Hz, 3H, CH3), 2.63 (q, J¼7.5 Hz, 2H,
C]O) cmꢂ1 1H NMR (CDCl3):
.
d¼1.09 (d, J¼6.6 Hz, 6H, CH(CH3)2),

ꢀ
2616
A.E. Díaz-Alvarez et al. / Tetrahedron 68 (2012) 2611e2620
2.22e2.33 (m, 1H, CH(CH3)2), 2.47 (d, J¼7.0 Hz, 2H, CH2CH(CH3)2),
3.40 (d, J¼6.7 Hz, 2H, CH2CH]CH2), 3.82 (s, 3H, OCH3), 5.10e5.17 (m,
2H, CH2CH]CH2), 5.92e6.05 (m, 1H, CH2CH]CH2), 6.78e7.01 (m,
J¼7.5 Hz, 2H, CH2CH3), 3.30 (d, J¼7.9 Hz, 2H, CH2CH]CH2), 3.39 (d,
J¼6.7 Hz, 2H, CH2CH]CH2), 3.82 (s, 3H, OCH3), 5.07e5.19 (m, 4H,
CH2CH]CH2), 5.86e6.07 (m, 2H, CH2CH]CH2), 6.69 (s, 1H, CHarom),
3H, CHarom). 13C{1H} NMR (CDCl3):
d¼22.8 (s, CH(CH3)2), 26.4 (s,
6.70 (s, 1H, CHarom). 13C{1H} NMR (CDCl3):
d¼9.7 (s, CH3), 27.7 (s,
CH(CH3)2), 40.5 (s, CH2CH]CH2), 43.5 (s, CH2CH(CH3)2), 56.1 (s,
OCH3), 113.1, 121.0 and 122.9 (s, CHarom), 116.5 (s, CH2CH]CH2), 137.5
(s, CH2CH]CH2), 138.4, 139.3 and 151.3 (s, Carom), 171.7 (s, C]O).
HRMS (EI): m/z¼248.1415, calcd for C15H20O3: 248.1412.
CH2CH3), 35.0 and 40.6 (s, CH2CH]CH2), 56.3 (s, OCH3), 111.1 and
122.1 (s, CHarom), 116.4 and 116.5 (s, CH2CH]CH2), 133.4, 136.9, 138.6
and 151.6 (s, Carom), 136.5 and 137.6 (s, CH2CH]CH2), 172.6 (s, C]O).
HRMS (EI): m/z¼260.1416, calcd for C16H20O3: 260.1412.
4.2.16. 4-Allyl-2-methoxyphenyl benzoate (9d).32 Whitesolid. Yield:
4.2.22. 2-Allyl-6-chlorophenyl propionate (23a). Pale yellow oil.
91% (2.441 g). Mp: 66e67 ꢀC. IR (neat):
n
¼1638 (m, C]C), 1738 (s,
Yield: 81% (1.819 g). IR (Nujol):
n
¼1639 (m, C]C), 1771 (s, C]O)
C]O) cmꢂ1.1H NMR (CDCl3):
d
¼3.43 (d, J¼6.7 Hz, 2H, CH2CH]CH2),
cmꢂ1.1H NMR (CDCl3):
d
¼1.34 (t, J¼6.4 Hz, 3H, CH3), 2.67 (q, J¼6.4 Hz,
3.83 (s, 3H, OCH3), 5.11e5.18 (m, 2H, CH2CH]CH2), 6.00e6.14 (m,
2H, CH2CH3), 3.33 (d, J¼6.6 Hz, 2H, CH2CH]CH2), 5.08e5.15 (m, 2H,
1H, CH2CH]CH2), 6.83e8.25 (m, 8H, CHarom). 13C{1H} NMR (CDCl3):
CH2CH]CH2), 5.83e5.97 (m, 1H, CH2CH]CH2), 7.14e7.39 (m, 3H,
d
¼40.2 (s, CH2CH]CH2), 55.9 (s, OCH3), 112.9, 120.8, 127.9, 128.6,
CHarom).13C{1H} NMR (CDCl3):
d¼9.6 (s, CH3), 27.8 (s, CH2CH3), 35.3 (s,
130.3 and 133.5 (s, CHarom),116.2 (s, CH2CH]CH2),129.6,138.3,139.1
and 151.2 (s, Carom), 137.2 (s, CH2CH]CH2), 164.9 (s, C]O). HRMS
(EI): m/z¼268.1099, calcd for C17H16O3: 268.1099.
CH2CH]CH2), 116.7 (s, CH2CH]CH2), 127.1, 128.6 and 129.0 (s,
CHarom),127.8,135.0 and 145.9 (s, Carom),135.7 (s, CH2CH]CH2),171.9
(s, C]O). HRMS (EI): m/z¼224.0611, calcd for C12H13O2Cl: 224.0604.
4.2.17. 4-Allylphenyl propionate (10a). Colourless oil. Yield: 73%
4.2.23. 2-Acetyl-6-allylphenyl propionate (24a). Colourless oil.
(1.388 g). IR (neat):
(CDCl3):
n
¼1639 (m, C]C), 1761 (s, C]O) cmꢂ1. 1H NMR
Yield: 88% (2.042 g). IR (Nujol):
n
¼1639 (m, C]C), 1693 and 1760 (s,
d
¼1.29 (t, J¼7.6 Hz, 3H, CH3), 2.60 (q, J¼7.6 Hz, 2H,
C]O) cmꢂ1.1H NMR (CDCl3):
d
¼1.30 (t, J¼7.6 Hz, 3H, CH2CH3), 2.55 (s,
CH2CH3), 3.41 (d, J¼6.7 Hz, 2H, CH2CH]CH2), 5.08e5.14 (m, 2H,
3H, COCH3), 2.66 (q, J¼7.6 Hz, 2H, CH2CH3), 3.34 (d, J¼6.6 Hz, 2H,
CH2CH]CH2), 5.05e5.12 (m, 2H, CH2CH]CH2), 5.83e5.96 (m, 1H,
CH2CH]CH2), 7.27 (dd, J¼7.7 and 7.4 Hz,1H, CHarom), 7.43 (d, J¼7.7 Hz,
CH2CH]CH2), 5.90e6.05 (m, 1H, CH2CH]CH2), 7.01e7.23 (m, 4H,
CHarom). 13C{1H} NMR (CDCl3):
d
¼9.5 (s, CH3), 28.1 (s, CH2CH3), 40.0
(s, CH2CH]CH2),116.4 (s, CH2CH]CH2), 121.8 and 129.9 (s, CHarom),
137.6 (s, CH2CH]CH2), 137.9 and 149.5 (s, Carom), 173.5 (s, C]O).
HRMS (EI): m/z¼190.0990, calcd for C12H14O2: 190.0994.
1H, CHarom), 7.66 (d, J¼7.4 Hz,1H, CHarom).13C{1H}NMR (CDCl3):
¼9.2
d
(s, CH2CH3), 28.1 (s, CH2CH3), 29.5 (s, COCH3), 34.8 (s, CH2CH]CH2),
117.1 (s, CH2CH]CH2), 126.1, 128.8 and 134.6 (s, CHarom), 131.5, 134.4
and 147.5 (s, Carom), 135.8 (s, CH2CH]CH2), 173.1 (s, OC]O), 198.5 (s,
COCH3). HRMS (EI): m/z¼232.1098, calcd for C14H16O3: 232.1099.
4.2.18. 4-Allylphenyl isobutyrate (10b). Colourless oil. Yield: 78%
(1.593 g). IR (neat):
(CDCl3):
n
¼1639 (m, C]C), 1757 (s, C]O) cmꢂ1. 1H NMR
d
¼1.36 (d, J¼7.0 Hz, 6H, CH(CH3)2), 2.83 (sept, J¼7.0 Hz, 1H,
4.2.24. 2-Allyl-4-chlorophenyl propionate (25a). Pale yellow oil.
CH(CH3)2), 3.42 (d, J¼6.7 Hz, 2H, CH2CH]CH2), 5.10e5.17 (m, 2H,
CH2CH]CH2), 5.94e6.07 (m, 1H, CH2CH]CH2), 7.04 (d, J¼8.6 Hz,
2H, CHarom), 7.23 (d, J¼8.6 Hz, 2H, CHarom). 13C{1H} NMR (CDCl3):
Yield: 77% (1.730 g). IR (Nujol):
n
¼1635 (m, C]C), 1762 (s, C]O)
cmꢂ1 1H NMR (CDCl3):
.
d
¼1.29 (t, J¼7.5 Hz, 3H, CH3), 2.61 (q,
J¼7.5 Hz, 2H, CH2CH3), 3.28 (d, J¼6.6 Hz, 2H, CH2CH]CH2),
5.06e5.15 (m, 2H, CH2CH]CH2), 5.82e5.95 (m, 1H, CH2CH]CH2),
7.00 (d, J¼8.2 Hz, 1H, CHarom), 7.20e7.25 (m, 2H, CHarom). 13C{1H}
d
¼19.4 (s, CH(CH3)2), 34.6 (s, CH(CH3)2), 40.0 (s, CH2CH]CH2),116.4
(s, CH2CH]CH2), 121.8 and 129.9 (s, CHarom),137.6 (s, CH2CH]CH2),
137.8 and 149.6 (s, Carom), 176.1 (s, C]O). HRMS (EI): m/z¼204.1150,
calcd for C13H16O2: 204.1150.
NMR (CDCl3):
d
¼9.5 (s, CH3), 28.0 (s, CH2CH3), 34.7 (s, CH2CH]
CH2), 117.4 (s, CH2CH]CH2), 124.1, 127.8 and 130.6 (s, CHarom), 131.6,
134.2 and 147.9 (s, Carom), 135.4 (s, CH2CH]CH2), 172.9 (s, C]O).
HRMS (EI): m/z¼224.0602, calcd for C12H13O2Cl: 224.0604.
4.2.19. 4-Allylphenyl-3-methyl butanoate (10c). Pale yellow oil.
Yield: 75% (1.637 g). IR (neat):
n
¼1639 (m, C]C), 1759 (s, C]O)
cmꢂ1 1H NMR (CDCl3):
.
d
¼1.09 (d, J¼6.7 Hz, 6H, CH(CH3)2),
4.2.25. 2-Allyl-4-methylsulfanylphenyl propionate (26a). Yellow oil.
2.21e2.34 (m, 1H, CH(CH3)2), 2.46 (d, J¼7.0 Hz, 2H, CH2CH(CH3)2),
3.41 (d, J¼6.7 Hz, 2H, CH2CH]CH2), 5.09e5.15 (m, 2H, CH2CH]
CH2), 5.92e6.05 (m, 1H, CH2CH]CH2), 7.03 (d, J¼8.4 Hz, 2H,
CHarom), 7.23 (d, J¼8.4 Hz, 2H, CHarom). 13C{1H} NMR (CDCl3):
Yield: 75% (1.772 g). IR (Nujol):
n
¼1639 (m, C]C), 1757 (s, C]O)
cmꢂ1. 1H NMR (CDCl3):
d
¼1.29 (t, J¼7.3 Hz, 3H, CH2CH3), 2.48 (s, 3H,
SCH3), 2.60 (q, J¼7.3 Hz, 2H, CH2CH3), 3.28 (d, J¼6.5 Hz, 2H,
CH2CH]CH2), 5.06e5.12 (m, 2H, CH2CH]CH2), 5.83e5.97 (m, 1H,
CH2CH]CH2), 6.98 (d, J¼8.4 Hz, 1H, CHarom), 7.15 (m, 2H, CHarom).
d
¼22.8 (s, CH(CH3)2), 26.3 (s, CH(CH3)2), 40.0 (s, CH2CH]CH2), 43.7
(s, CH2CH(CH3)2), 116.4 (s, CH2CH]CH2), 121.9 and 129.9 (s,
CHarom), 137.6 (s, CH2CH]CH2), 137.9 and 149.4 (s, Carom), 172.1 (s,
C]O). HRMS (EI): m/z¼218.1302, calcd for C14H18O2: 218.1307.
13C{1H} NMR (CDCl3):
d
¼9.5 (s, CH2CH3), 16.9 (s, SCH3), 28.0 (s,
CH2CH3), 35.0 (s, CH2CH]CH2), 116.9 (s, CH2CH]CH2), 123.2, 126.3
and 129.3 (s, CHarom), 132.8, 136.1 and 147.2 (s, Carom), 135.9 (s,
CH2CH]CH2), 173.2 (s, C]O). HRMS (EI): m/z¼236.0867, calcd for
C13H16O2S: 236.0871.
4.2.20. 4-Allylphenyl benzoate (10d).33 White solid. Yield: 70%
(1.668 g). Mp: 61e62 ꢀC. IR (Nujol):
n
¼1641 (m, C]C), 1733 (s, C]
O) cmꢂ1
.
1H NMR (CDCl3):
d
¼3.45 (d, J¼6.7 Hz, 2H, CH2CH]CH2),
4.3. General procedure for the synthesis of (E)-(1-propenyl)
phenyl esters 11e15(aed) and 27ae30a
5.11e5.18 (m, 2H, CH2CH]CH2), 5.95e6.09 (m, 1H, CH2CH]CH2),
7.18 (d, J¼8.4 Hz, 2H, CHarom), 7.28 (d, J¼8.4 Hz, 2H, CHarom),
7.51e7.66 (m, 3H, CHarom), 8.22 (m, 2H, CHarom). 13C{1H} NMR
Under nitrogen atmosphere, the corresponding allylphenyl ester
(CDCl3):
d
¼40.0 (s, CH2CH]CH2), 116.5 (s, CH2CH]CH2), 122.0,
6e10(aed) or 22ae25a (2 mmol), the ruthenium(IV) catalyst pre-
129.0 and 130.0, 130.3 and 133.9 (s, CHarom), 130.1, 138.1 and 149.7
(s, Carom), 137.6 (s, CH2CH]CH2), 165.7 (s, C]O). HRMS (EI): m/
z¼238.0997, calcd for C16H14O2: 238.0994.
cursor [{RuCl(m :h
-Cl)(h3 3-C10H16)}2] (6 mg, 0.01 mmol; 1 mol % of
Ru) and methanol (0.5 mL) were introduced into a Teflon-capped
sealed tube. Then, the mixture was heated at 80 ꢀC in an oil-bath for
the indicated time. The course of the reaction was monitored by
4.2.21. 2,4-Diallyl-6-methoxyphenyl propionate (22a). Colourless
taking regularly samples of ca. 10 mL, which after dilution were ana-
oil. Yield: 73% (1.900 g). IR (Nujol):
n
¼1638 (m, C]C), 1763 (s, C]O)
lyzed by GC. Solvent removal under reduced pressure, followed by
purification of the resulting oily residue by column chromatography
cmꢂ1 1H NMR (CDCl3):
.
d¼1.32 (t, J¼7.5 Hz, 3H, CH3), 2.64 (q,

ꢀ
A.E. Díaz-Alvarez et al. / Tetrahedron 68 (2012) 2611e2620
2617
over SiO2, using a mixture hexanes/Et2O (85:15) as eluent, afforded
the (E)-propenylphenyl esters 11e15(aed) and 27e30a. Character-
ization data for these compounds are as follows (copies of the 1H and
13C{1H} spectra are included in Supplementary data):
and 1.6 Hz, 3H, HC]CHCH3), 2.90 (sept, J¼7.0 Hz, 1H, CH(CH3)2),
6.26 (part A of AB system of q, J¼15.7 and 6.5 Hz, 1H, HC]CHCH3),
6.46 (part B of AB system of q, J¼15.7 and 1.6 Hz, 1H, HC]CHCH3),
7.01e7.57 (m, 4H, CHarom). 13C{1H} NMR (CDCl3):
d¼19.3 (CH]
CHCH3), 19.5 (s, CH(CH3)2), 34.6 (s, CH(CH3)2), 122.8, 124.7, 126.4,
126.9, 128.0 and 128.6 (s, CHarom and ]CH), 131.0 and 148.0 (s,
Carom), 175.8 (s, C]O). HRMS (EI): m/z¼204.1153, calcd for
C13H16O2: 204.1150.
4.3.1. (E)-2-Methyl-6-(1-propenyl)phenyl propionate (11a). Yellow
oil. Yield: 85% (0.347 g). IR (neat):
n
¼1653 (w, C]C), 1759 (s, C]O)
cmꢂ1 1H NMR (CDCl3):
.
d
¼1.38 (t, J¼7.6 Hz, 3H, CH2CH3), 1.93 (dd,
J¼6.4 and 1.5 Hz, 3H, HC]CHCH3), 2.20 (s, 3H, CH3), 2.70 (q, J¼7.6 Hz,
2H, CH2CH3), 6.26 (part A of AB system of q, J¼15.7 and 6.4 Hz, 1H,
HC]CHCH3), 6.42 (part B of AB system of q, J¼15.7 and 1.5 Hz, 1H,
4.3.7. (E)-2-(1-Propenyl)phenyl-3-methyl butanoate (12c). Yellow
oil. Yield: 88% (0.384 g). IR (neat):
n
¼1653 (w, C]C), 1759 (s, C]
HC]CHCH3), 7.12e7.40 (m, 3H, CHarom).13C{1H} NMR (CDCl3):
d¼9.8,
O) cmꢂ1. 1H NMR (CDCl3):
d
¼1.13 (d, J¼6.6 Hz, 6H, CH(CH3)2), 1.92
16.8 and 19.3 (s, CH3), 27.9 (s, CH2), 124.5, 125.0, 126.3, 128.6 and 129.8
(s, CHarom and ]CH), 130.9, 131.1 and 146.9 (s, Carom), 172.7 (s, C]O).
HRMS (EI): m/z¼204.1155, calcd for C13H16O2: 204.1150.
(dd, J¼6.5 and 1.6 Hz, 3H, HC]CHCH3), 2.31e2.35 (m, 1H,
CH(CH3)2), 2.52 (d, J¼7.0 Hz, 2H, CH2CH(CH3)2), 6.27 (part A of AB
system of q, J¼15.8 and 6.5 Hz, 1H, HC]CHCH3), 6.47 (part B of
AB system of q, J¼15.8 and 1.6 Hz, 1H, HC]CHCH3), 7.05e7.55 (m,
4.3.2. (E)-2-Methyl-6-(1-propenyl)phenyl isobutyrate (11b). Yellow
4H, CHarom). 13C{1H} NMR (CDCl3):
d¼18.9 (s, CH]CHCH3), 22.5
oil. Yield: 76% (0.331 g). IR (neat):
n
¼1657 (w, C]C), 1757 (s, C]O)
(s, CH(CH3)2), 25.9 (s, CH(CH3)2), 43.3 (s, CH2), 122.5, 124.5, 126.0,
126.5, 127.6 and 128.3 (s, CHarom and ]CH), 130.6 and 147.6
(s, Carom), 171.4 (s, C]O). HRMS (EI): m/z¼218.1307, calcd for
C14H18O2: 218.1307.
cmꢂ1. 1H NMR (CDCl3):
d
¼1.44 (d, J¼7.0 Hz, 6H, CH(CH3)2), 1.93 (dd,
J¼6.4 and 1.6 Hz, 3H, HC]CHCH3), 2.20 (s, 3H, CH3), 2.95 (sept,
J¼7.0 Hz, 1H, CH(CH3)2), 6.25 (part A of AB system of q, J¼15.7 and
6.4 Hz, 1H, HC]CHCH3), 6.43 (part B of AB system of q, J¼15.7 and
1.6 Hz, 1H, HC]CHCH3), 7.36e7.42 (m, 3H, CHarom). 13C{1H} NMR
4.3.8. (E)-2-(1-Propenyl)phenyl benzoate (12d). Colourless oil.
(CDCl3):
d
¼16.4 and 18.9 (s, CH3), 19.2 (s, CH(CH3)2), 34.3 (s,
Yield: 90% (0.429 g). IR (neat):
n
¼1656 (w, C]C), 1735 (s, C]O)
CH(CH3)2), 124.1, 124.6, 125.8, 128.2 and 129.4 (s, CHarom and ]CH),
130.5, 130.7 and 146.4 (s, Carom), 174.7 (s, C]O). HRMS (EI): m/
z¼218.1306, calcd for C14H18O2: 218.1307.
cmꢂ1 1H NMR (CDCl3):
.
d
¼1.89 (dd, J¼6.6 and 1.6 Hz, 3H, HC]
CHCH3), 6.35 (part A of AB system of q, J¼15.8 and 6.6 Hz, 1H, HC]
CHCH3), 6.56 (part B of AB system of q, J¼15.8 and 1.6 Hz, 1H, HC]
CHCH3), 7.18e7.33 (m, 3H, CHarom), 7.56e7.74 (m, 4H, CHarom), 8.31
4.3.3. (E)-2-Methyl-6-(1-propenyl)phenyl-3-methyl
(11c). Yellow oil. Yield: 84% (0.390 g). IR (neat):
1759 (s, C]O) cmꢂ1 1H NMR (CDCl3):
CH(CH3)2), 1.91 (dd, J¼6.5 and 1.6 Hz, 3H, HC]CHCH3), 2.20 (s, 3H,
CH3), 2.30e2.41 (m, 1H, CH(CH3)2), 2.56 (d, J¼7.0 Hz, 2H,
CH2CH(CH3)2), 6.25 (part A of AB system of q, J¼15.7 and 6.5 Hz, 1H,
HC]CHCH3), 6.43 (part B of AB system of q, J¼15.7 and 1.6 Hz, 1H,
HC]CHCH3), 7.12e7.39 (m, 3H, CHarom). 13C{1H} NMR (CDCl3):
butanoate
(m, 2H, CHarom). 13C{1H} NMR (CDCl3):
d¼19.3 (s, CH3), 123.1, 124.7,
n
¼1653 (w, C]C),
126.7, 126.9, 128.2, 128.9, 129.1, 130.7 and 134.1 (s, CHarom and ]
CH), 129.9, 131.1 and 148.1 (s, Carom), 165.5 (s, C]O). HRMS (EI): m/
z¼238.1001, calcd for C16H14O2: 238.0994.
.
d
¼1.14 (d, J¼6.6 Hz, 6H,
4.3.9. (E)-3-(1-Propenyl)phenyl propionate (13a). Yellow oil. Yield:
74% (0.281 g). IR (neat):
n
¼1657 (w, C]C), 1761 (s, C]O) cmꢂ1
.
1H NMR (CDCl3):
d
¼1.30 (t, J¼7.5 Hz, 3H, CH2CH3), 1.90 (dd,
d
¼16.9 and 19.3 (s, CH3), 23.0 (s, CH(CH3)2), 26.1 (s, CH(CH3)2), 43.5
J¼6.4 and 1.3 Hz, 3H, HC]CHCH3), 2.62 (q, J¼7.5 Hz, 2H,
CH2CH3), 6.24 (part A of AB system of q, J¼15.7 and 6.4 Hz, 1H,
HC]CHCH3), 6.41 (part B of AB system of q, J¼15.7 and 1.3 Hz,
1H, HC]CHCH3), 6.93e7.09 (m, 4H, CHarom). 13C{1H} NMR
(s, CH2), 124.5, 125.3, 126.3, 128.6 and 129.8 (s, CHarom and ]CH),
130.9, 131.2 and 146.9 (s, Carom), 171.3 (s, C]O). HRMS (EI): m/
z¼232.1466, calcd for C15H20O2: 232.1463.
(CDCl3):
d
¼9.1 and 18.5 (s, CH3), 27.8 (s, CH2), 118.7, 119.8, 123.4,
4.3.4. (E)-2-Methyl-6-(1-propenyl)phenyl benzoate (11d). Yellow
126.9, 129.3 and 130.4 (s, CHarom and ]CH), 139.6 and 151.1
(s, Carom), 173.0 (s, C]O). HRMS (EI): m/z¼190.0992, calcd for
C12H14O2: 190.0994.
oil. Yield: 70% (0.353 g). IR (neat):
n
¼1639 (w, C]C), 1737 (s, C]O)
cmꢂ1 1H NMR (CDCl3):
.
d
¼1.86 (dd, J¼6.5 and 1.5 Hz, 3H, HC]
CHCH3), 2.25 (s, 3H, CH3), 6.34 (part A of AB system of q, J¼15.7 and
6.5 Hz, 1H, HC]CHCH3), 6.52 (part B of AB system of q, J¼15.7 and
1.5 Hz, 1H, HC]CHCH3), 7.19e7.70 (m, 6H, CHarom), 8.32e8.39 (m,
4.3.10. (E)-3-(1-Propenyl)phenyl isobutyrate (13b). Colourless oil.
Yield: 86% (0.351 g). IR (neat):
n
¼1657 (w, C]C), 1760 (s, C]O)
2H, CHarom). 13C{1H} NMR (CDCl3):
d¼16.9 and 19.3, (s, CH3), 124.5,
cmꢂ1. 1H NMR (CDCl3):
d
¼1.35 (d, J¼7.0 Hz, 6H, CH(CH3)2), 1.91 (dd,
124.9, 126.5, 128.8, 129.1, 129.8, 130.7 and 134.1 (s, CHarom and ]
CH), 129.7, 131.2, 131.3 and 147.0 (s, Carom), 165.0 (s, C]O). HRMS
(EI): m/z¼252.1157, calcd for C17H16O2: 252.1150.
J¼6.4 and 1.3 Hz, 3H, HC]CHCH3), 2.83 (sept, J¼7.0 Hz, 1H,
CH(CH3)2), 6.28 (part A of AB system of q, J¼15.7 and 6.4 Hz, 1H,
HC]CHCH3), 6.41 (part B of AB system of q, J¼15.7 and 1.3 Hz, 1H,
HC]CHCH3), 7.07e7.31 (m, 4H, CHarom). 13C{1H} NMR (CDCl3):
4.3.5. (E)-2-(1-Propenyl)phenyl propionate (12a). Yellow oil. Yield:
d
¼18.4 (s, CH3), 18.9 (s, CH(CH3)2), 34.2 (s, CH(CH3)2), 118.6, 119.7,
87% (0.331 g). IR (neat):
NMR (CDCl3):
n
¼1657 (w, C]C), 1763 (s, C]O) cmꢂ1. 1H
123.3, 126.8, 129.3 and 130.2 (s, CHarom and ]CH), 139.6 and 151.2
(s, Carom), 175.6 (s, C]O). HRMS (EI): m/z¼204.1145, calcd for
C13H16O2: 204.1150.
d
¼1.34 (t, J¼7.6 Hz, 3H, CH2CH3), 1.93 (dd, J¼6.5 and
1.5 Hz, 3H, HC]CHCH3), 2.67 (q, J¼7.6 Hz, 2H, CH2CH3), 6.28 (part A
of AB system of q, J¼15.8 and 6.5 Hz, 1H, HC]CHCH3), 6.46 (part B
of AB system of q, J¼15.8 and 1.5 Hz,1H, HC]CHCH3), 7.04e7.26 (m,
4.3.11. (E)-3-(1-Propenyl)phenyl-3-methyl butanoate (13c). Pale
4H, CHarom). 13C{1H} NMR (CDCl3):
d
¼9.6 and 19.3 (s, CH3), 28.1 (s,
yellow oil. Yield: 79% (0.345 g). IR (neat):
n
¼1657 (w, C]C), 1757 (s,
CH2), 122.9, 124.8, 126.4, 126.9, 128.0 and 128.7 (s, CHarom and ]
CH), 130.9 and 147.9 (s, Carom), 173.2 (s, C]O). HRMS (EI): m/
z¼190.0992, calcd for C12H14O2: 190.0994.
C]O) cmꢂ1 1H NMR (CDCl3):
.
d
¼1.11 (d, J¼6.6 Hz, 6H, CH(CH3)2),
1.91 (dd, J¼6.5 and 1.3 Hz, 3H, HC]CHCH3), 2.23e2.36 (m, 1H,
CH(CH3)2), 2.47 (d, J¼7.0 Hz, 2H, CH2CH(CH3)2), 6.28 (part A of AB
system of q, J¼15.7 and 6.5 Hz, 1H, HC]CHCH3), 6.42 (part B of AB
system of q, J¼15.7 and 1.3 Hz, 1H, HC]CHCH3), 6.94e7.10 (m, 4H,
4.3.6. (E)-2-(1-Propenyl)phenyl isobutyrate (12b). Yellow oil. Yield:
84% (0.343 g). IR (neat):
NMR (CDCl3):
n
¼1657 (w, C]C), 1758 (s, C]O) cmꢂ1. 1H
CHarom). 13C{1H} NMR (CDCl3):
d¼18.5 (s, CH3), 22.4 (s, CH(CH3)2),
d
¼1.40 (d, J¼7.0 Hz, 6H, CH(CH3)2), 1.92 (dd, J¼6.5
25.9 (s, CH(CH3)2), 43.4 (s, CH2), 118.8, 119.9, 123.4, 126.8, 129.3 and

ꢀ
2618
A.E. Díaz-Alvarez et al. / Tetrahedron 68 (2012) 2611e2620
130.3 (s, CHarom and ]CH),139.6 and 151.0 (s, Carom),171.5 (s, C]O).
HRMS (EI): m/z¼218.1306, calcd for C14H18O2: 218.1307.
J¼6.5 and 1.6 Hz, 3H, HC]CHCH3), 2.60 (q, J¼7.5 Hz, 2H, CH2CH3),
6.20 (part A of AB system of q, J¼15.7 and 6.5 Hz, 1H, HC]CHCH3),
6.41 (part B of AB system of q, J¼15.7 and 1.6 Hz, 1H, HC]CHCH3),
7.02 (d, J¼8.6 Hz, 2H, CHarom), 7.34 (d, J¼8.6 Hz, 2H, CHarom). 13C{1H}
4.3.12. (E)-3-(1-Propenyl)phenyl benzoate (13d). White solid. Yield:
87% (0.414 g). Mp: 58e59 ꢀC. IR (Nujol):
n
¼1655 (w, C]C), 1745 (s,
NMR (CDCl3):
d¼9.5 and 18.9 (s, CH3), 28.2 (s, CH2), 121.9 and 127.1
C]O) cmꢂ1
.
1H NMR (CDCl3):
d
¼1.94 (dd, J¼6.4 and 1.4 Hz, 3H,
(s, CHarom), 126.3 and 130.5 (s, ]CH), 136.0 and 149.9 (s, Carom),
173.4 (s, C]O). HRMS (EI): m/z¼190.0999, calcd for C12H14O2:
190.0994.
HC]CHCH3), 6.33 (part A of AB system of q, J¼15.7 and 6.4 Hz, 1H,
HC]CHCH3), 6.47 (part B of AB system of q, J¼15.7 and 1.4 Hz, 1H,
HC]CHCH3), 7.10e7.71 (m, 7H, CHarom), 8.26 (m, 2H, CHarom). 13C
{1H} NMR (CDCl3):
d
¼18.5 (s, CH3), 118.9, 120.0, 123.6, 127.0, 128.6,
4.3.18. (E)-4-(1-Propenyl)phenyl isobutyrate (15b).14r Pale yellow
129.5, 130.2, 130.3 and 133.6 (s, CHarom and ]CH), 129.7, 139.8 and
151.3 (s, Carom), 165.2 (s, C]O). HRMS (EI): m/z¼238.0999, calcd for
C16H14O2: 238.0994.
solid. Yield: 87% (0.355 g). Mp: 43e44 ꢀC. IR (Nujol):
n
¼1658 (w,
C]C),1757 (s, C]O) cmꢂ1. 1H NMR (CDCl3):
d
¼1.35 (d, J¼7.0 Hz, 6H,
CH(CH3)2), 1.91 (dd, J¼6.5 and 1.6 Hz, 3H, HC]CHCH3), 2.83 (sept,
J¼7.0 Hz, 1H, CH(CH3)2), 6.22 (part A of AB system of q, J¼15.7 and
6.5 Hz, 1H, HC]CHCH3), 6.42 (part B of AB system of q, J¼15.7 and
1.6 Hz, 1H, HC]CHCH3), 7.03 (d, J¼8.6 Hz, 2H, CHarom), 7.35 (d,
4.3.13. (E)-2-Methoxy-4-(1-propenyl)phenyl propionate (14a).34 Col-
ourless oil. Yield: 79% (0.348 g). IR (neat):
n
¼1645 (w, C]C), 1763 (s,
C]O) cmꢂ1. 1H NMR (CDCl3):
d¼1.30 (t, J¼7.5 Hz, 3H, CH2CH3), 1.90
J¼8.6 Hz, 2H, CHarom). 13C{1H} NMR (CDCl3):
¼18.9 (s, CH3), 19.3 (s,
d
(dd, J¼6.5 and 1.6 Hz, 3H, HC]CHCH3), 2.63 (q, J¼7.5 Hz, 2H,
CH2CH3), 3.85 (s, 3H, OCH3), 6.21 (part A of AB system of q, J¼15.7 and
6.5 Hz, 1H, HC]CHCH3), 6.40 (part B of AB system of q, J¼15.7 and
1.6 Hz, 1H, HC]CHCH3), 6.80e7.28 (m, 3H, CHarom). 13C{1H} NMR
CH(CH3)2), 34.6 (s, CH(CH3)2), 121.9 and 127.1 (s, CHarom), 126.2 and
130.6 (s, ]CH),136.0 and 150.1 (s, Carom),176.0 (s, C]O). HRMS (EI):
m/z¼204.1158, calcd for C13H16O2: 204.1150.
(CDCl3):
d
¼9.2 and 18.4 (s, CH3), 27.4 (s, CH2), 55.8 (s, OCH3), 109.6,
4.3.19. (E)-4-(1-Propenyl)phenyl-3-methyl butanoate (15c).14a,c Pale
118.4, 122.7, 125.9 and 130.5 (s, CHarom and ]CH), 136.9, 138.7 and
151.0 (s, Carom), 172.7 (s, C]O). HRMS (EI): m/z¼220.1099, calcd for
C13H16O3: 220.1099.
yellow oil. Yield: 89% (0.388 g). IR (neat):
n
¼1657 (w, C]C), 1761 (s,
C]O) cmꢂ1 1H NMR (CDCl3):
.
d
¼1.09 (d, J¼6.6 Hz, 6H, CH(CH3)2),
1.90 (dd, J¼6.5 and 1.5 Hz, 3H, HC]CHCH3), 2.25e2.34 (m, 1H,
CH(CH3)2), 2.46 (d, J¼7.1 Hz, 2H, CH2CH(CH3)2), 6.21 (part A of AB
system of q, J¼15.8 and 6.5 Hz, 1H, HC]CHCH3), 6.40 (part B of AB
system of q, J¼15.8 and 1.5 Hz, 1H, HC]CHCH3), 7.05 (d, J¼8.6 Hz,
2H, CHarom), 7.37 (d, J¼8.6 Hz, 2H, CHarom). 13C{1H} NMR (CDCl3):
4.3.14. (E)-2-Methoxy-4-(1-propenyl)phenyl isobutyrate (14b).14h Col-
ourless oil. Yield: 78% (0.365 g). IR (neat):
n
¼1656 (w, C]C), 1760 (s,
C]O) cmꢂ1. 1H NMR (CDCl3):
d¼1.36 (d, J¼7.0 Hz, 6H, CH(CH3)2), 1.90
(dd, J¼6.5 and 1.5 Hz, 3H, HC]CHCH3), 2.87 (sept, J¼7.0 Hz, 1H,
CH(CH3)2), 3.82 (s, 3H, OCH3), 6.20 (part A of AB system of q, J¼15.7
and 6.5 Hz, 1H, HC]CHCH3), 6.40 (part B of AB system of q, J¼15.7
and 1.5 Hz, 1H, HC]CHCH3), 6.90e6.98 (m, 3H, CHarom). 13C{1H} NMR
d
¼18.9 (s, CH3), 22.8 (s, CH(CH3)2), 26.3 (s, CH(CH3)2), 43.8 (s, CH2),
122.0 and 127.1 (s, CHarom), 126.2 and 130.5 (s, ]CH), 136.1 and
149.9 (s, Carom), 172.0 (s, C]O). HRMS (EI): m/z¼218.1304, calcd for
C14H18O2: 218.1307.
(CDCl3):
d
¼18.8 (s, CH3), 19.4 (s, CH(CH3)2), 34.4 (s, CH(CH3)2), 56.2 (s,
OCH3), 110.1, 118.7, 123.0, 126.2 and 131.0 (s, CHarom and ]CH), 137.2,
139.3 and 151.5 (s, Carom), 175.7 (s, C]O). HRMS (EI): m/z¼234.1255,
calcd for C14H18O3: 234.1256.
4.3.20. (E)-4-(1-Propenyl)phenyl benzoate (15d). White solid.
Yield: 80% (0.381 g). Mp: 53e54 ꢀC. IR (Nujol):
n
¼1652 (w, C]C),
1745 (s, C]O) cmꢂ1. 1H NMR (CDCl3):
d
¼1.93 (dd, J¼6.5 and 1.5 Hz,
3H, HC]CHCH3), 6.25 (part A of AB system of q, J¼15.7 and 6.5 Hz,
1H, HC]CHCH3), 6.45 (part B of AB system of q, J¼15.7 and 1.5 Hz,
1H, HC]CHCH3), 7.15 (d, J¼8.6 Hz, 2H, CHarom), 7.41 (d, J¼8.6 Hz,
2H, CHarom), 7.64e7.70 (m, 3H, CHarom), 8.23 (m, 2H, CH of CHarom).
4.3.15. (E)-2-Methoxy-4-(1-propenyl)phenyl-3-methyl
butanoate
(14c).35 White solid. Yield: 84% (0.417 g). Mp: 41e42 ꢀC. IR (Nujol):
n
¼1656 (w, C]C), 1761 (s, C]O) cmꢂ1. 1H NMR (CDCl3):
¼1.11 (d,
d
J¼6.6 Hz, 6H, CH(CH3)2), 1.91 (dd, J¼6.5 and 1.6 Hz, 3H, HC]
CHCH3), 2.23e2.37 (m, 1H, CH(CH3)2), 2.48 (d, J¼7.1 Hz, 2H,
CH2CH(CH3)2), 3.83 (s, 3H, OCH3), 6.22 (part A of AB system of q,
J¼15.7 and 6.5 Hz, 1H, HC]CHCH3), 6.40 (part B of AB system of q,
13C{1H} NMR (CDCl3):
130.2 (s, CHarom), 126.2 and 133.6 (s, ]CH), 135.8 and 149.7 (s,
Carom), 165.2 (s, C]O). HRMS (EI): m/z¼238.0987, calcd for
C16H14O2: 238.0994.
d
¼18.5 (s, CH3), 121.7, 126.8, 128.6, 129.6 and
J¼15.7 and 1.6 Hz, 1H, HC]CHCH3), 6.90e6.99 (m, 3H, CHarom). 13
C
{1H} NMR (CDCl3):
d¼18.8 (s, CH3), 22.8 (s, CH(CH3)2), 26.3 (s,
4.3.21. (E,E)-2-Methoxy-4,6-di(1-propenyl)phenyl propionate (27a).
CH(CH3)2), 43.5 (s, CH2), 56.1 (s, OCH3), 110.0, 118.8, 123.1, 126.3 and
131.0 (s, CHarom and ]CH), 137.3, 139.1 and 151.5 (s, Carom), 171.5 (s,
C]O). HRMS (EI): m/z¼248.1407, calcd for C15H20O3: 248.1412.
Colourless oil. Yield: 68% (0.354 g). IR (Nujol):
n
¼1656 (m, C]C),
1760 (s, C]O) cmꢂ1. 1H NMR (CDCl3):
d¼1.33 (t, J¼7.5 Hz, 3H, CH3),
1.90 (dd, J¼6.4 and 1.3 Hz, 6H, HC]CHCH3), 2.67 (q, J¼7.5 Hz, 2H,
CH2CH3), 3.83 (s, 3H, OCH3), 6.16e6.33 (m, 2H, HC]CHCH3), 6.41
(part B of AB system of q, J¼15.8 and 1.3 Hz, 1H, HC]CHCH3), 6.52
(part B of AB system of q, J¼15.7 and 1.3 Hz, 1H, HC]CHCH3), 6.82
(d, J¼1.6 Hz,1H, CHarom), 7.05 (d, J¼1.6 Hz,1H, CHarom). 13C{1H} NMR
4.3.16. (E)-2-Methoxy-4-(1-propenyl)phenyl benzoate (14d).36 White
solid. Yield: 88% (0.472 g). Mp: 49e50 ꢀC. IR (Nujol):
n
¼1651 (w, C]
C), 1732 (s, C]O) cmꢂ1 1H NMR (CDCl3):
. d
¼1.92 (dd, J¼6.5 and
1.5 Hz, 3H, HC]CHCH3), 3.85 (s, 3H, OCH3), 6.26 (part A of AB
system of q, J¼15.7 and 6.5 Hz, 1H, HC]CHCH3), 6.43 (part B of AB
system of q, J¼15.7 and 1.5 Hz, 1H, HC]CHCH3), 6.95e7.11 (s, 3H,
CHarom), 7.28e7.63 (m, 3H, CHarom), 8.24 (m, 2H, CHarom). 13C{1H}
(CDCl3):
d
¼9.7 (s, CH2CH3), 18.4 and 18.9 (s, ]CHCH3), 27.3 (s,
CH2CH3), 55.9 (s, OCH3), 107.6 and 115.8 (s, CHarom), 124.3, 125.8,
128.5 and 130.7 (s, ]CH), 131.4, 135.9, 136.1 and 151.3 (s, Carom),
172.4 (s, C]O). HRMS (EI): m/z¼260.1417, calcd for C16H20O3:
260.1412.
NMR (CDCl3):
d
¼18.8 (s, CH3), 56.3 (s, OCH3), 110.2, 118.8, 123.2,
126.5, 128.9, 130.7, 130.9 and 133.8 (s, CHarom and ]CH), 129.9,
137.5, 139.2 and 151.6 (s, Carom), 165.2 (s, C]O). HRMS (EI): m/
z¼268.1103, calcd for C17H16O3: 268.1099.
4.3.22. (E)-2-Chloro-6-(1-propenyl)phenyl propionate (28a). Pale
yellow oil. Yield: 93% (0.417 g). IR (Nujol):
n
¼1654 (m, C]C), 1769
(s, C]O) cmꢂ1. 1H NMR (CDCl3):
d
¼1.36 (t, J¼7.5 Hz, 3H, CH2CH3),
4.3.17. (E)-4-(1-Propenyl)phenyl propionate (15a).14r Colourless oil.
1.91 (dd, J¼6.1 and 1.1 Hz, 3H, HC]CHCH3), 2.71 (q, J¼7.5 Hz, 2H,
CH2CH3), 6.25 (part A of AB system of q, J¼15.8 and 6.1 Hz, 1H, HC]
CHCH3), 6.37 (part B of AB system of q, J¼15.8 and 1.1 Hz, 1H, HC]
Yield: 83% (0.316 g). IR (neat):
n
¼1645 (w, C]C), 1755 (s, C]O)
cmꢂ1. 1H NMR (CDCl3):
d
¼1.29 (t, J¼7.5 Hz, 3H, CH2CH3), 1.99 (dd,

ꢀ
A.E. Díaz-Alvarez et al. / Tetrahedron 68 (2012) 2611e2620
2619
CHCH3), 7.13 (dd, J¼8.0 and 7.8 Hz, 1H, CHarom), 7.30 (d, J¼8.0 Hz,
References and notes
1H, CHarom), 7.39 (d, J¼7.8 Hz, 1H, CHarom). 13C{1H} NMR (CDCl3):
1. See, for example: (a) Metal-Catalysis in Industrial Organic Processes; Chiusoli, G.
P., Maitlis, P. M., Eds.; RSC Publishing: Cambridge, 2008; (b) van Leeuwen, P. W.
N. M. Homogeneous Catalysis: Understanding the Art; Kluwer Academic: Dor-
drecht, 2004; (c) Parshall, G. W.; Ittel, S. D. Homogeneous Catalysis; John Wiley &
Sons: New York, NY, 1992.
2. See, for example: (a) Reineccius, G. Flavor Chemistry and Technology; CRC: Boca
Raton, FL, 2006; (b) Bauer, K.; Garbe, D.; Surburg, H. Common Fragrance and
Flavour Materials; Wiley-VCH: Weinheim, 2001; (c) Ashurst, P. R. Food Flavor-
ings; Aspen: Maryland, 1999; (d) Chalk, A. J. In Flavors and Fragrances: A World
Perspective; Lawrence, B. M., Mookherjee, B. D., Willis, B. J., Eds.; Elsevier Sci-
ence: Amsterdam, 1988.
3. See, for example: (a) Arenas, D. R. M.; Ruíz, F. A. R.; Kouznetsov, V. V. Tetra-
hedron Lett. 2011, 52, 1388e1391; (b) Kouznetsov, V. V.; Arenas, D. R. M. Tet-
rahedron Lett. 2009, 50, 1546e1549; (c) Kouznetsov, V. V.; Forero, J. S. B.; Torres,
D. F. A. Tetrahedron Lett. 2008, 49, 5855e5857; (d) Alvarez, H. M.; de Andrade, J.
L.; Pereira, N., Jr.; Muri, E. M. F.; Horn, A., Jr.; Barbosa, D. P.; Antunes, O. A. C.
Catal. Commun. 2007, 8, 1336e1340; (e) Fujita, K.-I.; Fujita, T.; Kubo, I. Phytother.
Res. 2007, 21, 47e51; (f) Soares, P. M. G.; Lima, R. F.; de Freitas Pires, A.; Souza,
E. P.; Assreuy, A. M. S.; Criddle, D. N. Life Sci. 2007, 81, 1085e1093; (g) Gross, J. L.
Tetrahedron Lett. 2003, 44, 8563e8565; (h) de Lima, M. E. F.; Gabriel, A. J. A.;
Castro, R. N. J. Braz. Chem. Soc. 2000, 11, 371e374; (i) Amano, T.; Yoshikawa, K.;
Ogawa, T.; Sano, T.; Ohuchi, Y.; Tanami, T.; Ota, T.; Hatayama, K.; Higuchi, S.;
Amanuma, F.; Sota, K. Chem. Pharm. Bull. 1986, 34, 4653e4662.
d
¼9.6 (s, CH2CH3), 19.3 (s, ]CHCH3), 27.8 (s, CH2CH3), 124.3, 125.2,
127.0, 128.6 and 130.2 (s, CHarom and ]CH), 128.0, 133.4 and 144.4
(s, Carom), 172.1 (s, C]O). HRMS (EI): m/z¼224.0607, calcd for
C12H13O2Cl: 224.0604.
4.3.23. (E)-2-Acetyl-6-(1-propenyl)phenyl
propionate
(29a).
Colourless oil. Yield: 82% (0.381 g). IR (Nujol):
n
¼1652 (w, C]C),
1689 and 1762 (s, C]O) cmꢂ1. 1H NMR (CDCl3):
d¼1.31 (t, J¼7.5 Hz,
3H, CH2CH3), 1.89 (dd, J¼6.5 and 1.5 Hz, 3H, HC]CHCH3), 2.52 (s,
3H, COCH3), 2.69 (q, J¼7.5 Hz, 2H, CH2CH3), 6.25 (part A of AB
system of q, J¼15.8 and 6.5 Hz, 1H, HC]CHCH3), 6.43 (part B of AB
system of q, J¼15.8 and 1.5 Hz, 1H, HC]CHCH3), 7.23 (dd, J¼7.8 and
7.2 Hz, 1H, CHarom), 7.63 (m, 2H, CHarom). 13C{1H} NMR (CDCl3):
d
¼8.9 (s, CH2CH3), 18.9 (s, ]CHCH3), 27.6 (s, CH2CH3), 29.2 (s,
COCH3), 123.7, 125.7, 128.5, 129.7 and 130.3 (s, CHarom and ]CH),
131.2, 132.5 and 145.5 (s, Carom), 172.7 (s, OC]O), 198.0 (s, COCH3).
HRMS (EI): m/z¼232.1098, calcd for C14H16O3: 232.1099.
4. For a review, see: Pines, H.; Stalick, W. M. Base-Catalyzed Reactions of Hydro-
carbons and Related Compounds; Academic: New York, NY, 1977.
4.3.24. (E)-4-Chloro-2-(1-propenyl)phenyl propionate (30a). Pale
5. The heterogeneous ones rely mainly on the use of solid bases. Selected ex-
amples can be found in: (a) Kishore, D.; Kannan, S. Green Chem. 2002, 4,
607e610; (b) Srivastava, V. K.; Bajaj, H. C.; Jasra, R. V. Catal. Commun. 2003, 4,
543e548; (c) Kishore, D.; Kannan, S. J. Mol. Catal. A: Chem. 2004, 223, 225e230;
(d) Kishore, D.; Kannan, S. Appl. Catal., A: Gen. 2004, 270, 227e235; (e) Kishore,
D.; Kannan, S. J. Mol. Catal. A: Chem. 2006, 244, 83e92; (f) Jinesh, C. M.; An-
tonyraj, C. A.; Kannan, S. Catal. Today 2009, 141, 176e181; (g) Sharma, S. K.;
Parikh, P. A.; Jasra, R. V. J. Mol. Catal. A: Chem. 2010, 317, 27e33.
6. Efficient approaches to isomerize allylaromatics using catalytic amounts of
strong non-ionic bases, such as phosphazenes and proazaphosphatranes, have
also been described: (a) Wu, W.; Verkade, J. G. Arkivoc 2004, 9, 88e95; (b) Yu,
Z.; Yan, S.; Zhang, G.; He, W.; Wang, L.; Li, Y.; Zeng, F. Adv. Synth. Catal. 2006,
348, 111e117.
yellow oil. Yield: 86% (0.386 g). IR (Nujol):
n
¼1653 (w, C]C), 1762
(s, C]O) cmꢂ1. 1H NMR (CDCl3):
d¼1.32 (t, J¼7.6 Hz, 3H, CH2CH3),
1.92 (dd, J¼6.0 and 1.0 Hz, 3H, HC]CHCH3), 2.65 (q, J¼7.6 Hz, 2H,
CH2CH3), 6.27 (part A of AB system of q, J¼16.0 and 6.0 Hz, 1H, HC]
CHCH3), 6.35 (part B of AB system of q, J¼16.0 and 1.0 Hz, 1H, HC]
CHCH3), 6.98 (d, J¼8.6 Hz, 1H, CHarom), 7.19 (dd, J¼8.6 and 2.5 Hz,
1H, CHarom), 7.99 (d, J¼2.5 Hz, 1H, CHarom). 13C{1H} NMR (CDCl3):
d
¼9.2 (s, CH2CH3), 18.9 (s, ]CHCH3), 27.6 (s, CH2CH3), 123.3, 123.9,
126.3, 127.4 and 129.8 (s, CHarom and ]CH), 131.4, 132.1 and 145.9
(s, Carom), 172.6 (s, C]O). HRMS (EI): m/z¼224.0600, calcd for
C12H13O2Cl: 224.0604.
7. Shimizu, A.; Otsu, T.; Imoto, M. Bull. Chem. Soc. Jpn. 1968, 41, 953e959.
8. Blum, J.; Pickholtz, Y. Isr. J. Chem. 1969, 7, 723e733.
9. For selected examples, see: (a) Tooley, P. A.; Arndt, L. W.; Darensbourg, M. Y. J.
Am. Chem. Soc. 1985, 107, 2422e2427; (b) Satyanarayana, N.; Periasamy, M. J.
Organomet. Chem. 1987, 319, 113e117; (c) Rao, S. A.; Periasamy, M. J. Organomet.
Chem. 1988, 342, 15e20; (d) Reddy, M. R.; Periasamy, M. J. Organomet. Chem.
1995, 491, 263e266; (e) Blum, J.; Rosenfeld, A.; Polak, N.; Israelson, O.; Schu-
mann, H.; Avnir, D. J. Mol. Catal. A: Chem. 1996, 107, 217e223; (f) Bricout, H.;
Mortreux, A.; Monflier, E. J. Organomet. Chem. 1998, 553, 469e471; (g) Sato, T.;
Komine, N.; Hirano, M.; Komiya, S. Chem. Lett. 1999, 441e442; (h) Averbuj, C.;
Eisen, M. S. J. Am. Chem. Soc. 1999, 121, 8755e8759; (i) Baxendale, I. R.; Lee, A.-
L.; Ley, S. V. Synlett 2002, 516e518; (j) Baxendale, I. R.; Lee, A.-L.; Ley, S. V. J.
Chem. Soc., Perkin Trans. 1 2002, 1850e1857; (k) Arisawa, M.; Terada, Y.; Na-
kagawa, N.; Nishida, A. Angew. Chem., Int. Ed. 2002, 41, 4732e4734; (l) Shaviv,
E.; Botoshansky, M.; Eisen, M. S. J. Organomet. Chem. 2003, 683, 165e180; (m)
Lee, H. S.; Lee, G. Y. Bull. Korean Chem. Soc. 2005, 26, 461e462; (n) Hanessian, S.;
Giroux, S.; Larsson, A. Org. Lett. 2006, 8, 5481e5484; (o) Sharma, S. K.; Sri-
vastava, V. K.; Jasra, R. V. J. Mol. Catal. A: Chem. 2006, 245, 200e209; (p) Kim, I.
S.; Dong, G. R.; Jung, Y. H. J. Org. Chem. 2007, 72, 5424e5426; (q) Erdogan, G.;
Grotjahn, D. B. J. Am. Chem. Soc. 2009, 131, 10354e10355; (r) Donohoe, T. J.;
O’Riordan, T. J. C.; Rosa, C. P. Angew. Chem., Int. Ed. 2009, 48, 1014e1017; (s) Ding,
F.; Sun, Y.; Verpoort, F. Eur. J. Inorg. Chem. 2010, 1536e1543; (t) Scarso, A.;
Colladon, M.; Sgarbossa, P.; Santo, C.; Michelin, R. A.; Strukul, G. Organometallics
2010, 29, 1487e1497; (u) Nishiwaki, N.; Kamimura, R.; Shono, K.; Kawakami, T.;
Nakayama, K.; Nishino, K.; Nakayama, T.; Takahashi, K.; Nakamura, A.; Hoso-
kawa, T. Tetrahedron Lett. 2010, 51, 3590e3592; (v) Gauthier, D.; Lindhardt, A. T.;
Olsen, E. P. K.; Overgaard, J.; Skrydstrup, T. J. Am. Chem. Soc. 2010, 132,
7998e8009; (w) Meltzer, D.; Avnir, D.; Fanun, M.; Gutkin, V.; Popov, I.;
4.4. Synthesis of (E)-1,3-di(4-hydroxyphenyl)-2-methyl-1-
pentene (16)18
Under nitrogen atmosphere, 4-allylphenol (5) (0.268 g,
2 mmol), the ruthenium(IV) catalyst precursor [{RuCl(m : -
-Cl)(h3 h3
C10H16)}2] (6 mg, 0.01 mmol; 1 mol % of Ru) and methanol (0.5 mL)
were introduced into a Teflon-capped sealed tube. Then, the mix-
ture was heated at 80 ꢀC in an oil-bath for 24 h. Solvent removal
under reduced pressure, followed by purification of the resulting
oily residue by column chromatography over SiO2, using a mixture
hexanes/Et2O (85:15) as eluent, afforded diphenol 16 in 57% yield
(0.153 g) as a yellow oil. Characterization data for this compound
are as follows (copies of the 1H and 13C{1H} spectra are included in
Supplementary data): IR (Nujol):
n
¼1651 (w, C]C), 3324 (s, OeH)
cmꢂ1 1H NMR (CDCl3):
.
d
¼0.93 (t, J¼7.3 Hz, 3H, CH2CH3), 1.65 (d,
J¼1.2 Hz, 3H, CH3), 1.79e1.92 (m, 2H, CH2), 3.19 (t, J¼7.6 Hz,1H, CH),
5.37 (br, 1H, OH), 5.47 (br, 1H, OH), 6.41 (br, 1H, ]CH), 6.79e6.85
(m, 4H, CHarom), 7.14e7.16 (m, 4H, CHarom). 13C{1H} NMR (CDCl3):
d
¼13.0 and 16.1 (s, CH3), 25.8 (s, CH2), 56.2 (s, CH),115.3,115.4,129.5
€
and 130.7 (s, CHarom), 124.9 (s, ]CH),131.7,136.5, 154.0 and 154.1 (s,
Carom), 140.3 (s, ]C). HRMS (EI): m/z¼268.1459, calcd for C18H20O2:
268.1463.
Schomacker, R.; Schwarze, M.; Blum, J. J. Mol. Catal. A: Chem. 2011, 335, 8e13;
(x) Mayer, M.; Welther, A.; von Wangelin, A. J. ChemCatChem 2011, 3,
1567e1571.
10. (a) Cadierno, V.; Crochet, P.; García-Garrido, S. E.; Gimeno, J. Dalton Trans. 2004,
3635e3641; (b) Cadierno, V.; García-Garrido, S. E.; Gimeno, J. Chem. Commun.
2004, 232e233; (c) Cadierno, V.; García-Garrido, S. E.; Gimeno, J.; Nebra, N.
Chem. Commun. 2005, 4086e4088; (d) Cadierno, V.; García-Garrido, S. E.; Gi-
Acknowledgements
ꢀ
meno, J.; Varela-Alvarez, A.; Sordo, J. A. J. Am. Chem. Soc. 2006, 128, 1360e1370;
Financial support from the Spanish MICINN (Projects CTQ2010-
14796/BQU and CSD2007-00006) is acknowledged.
ꢀ
ꢀ
ꢀ
(e) Crochet, P.; Díez, J.; Fernandez-Zumel, M. A.; Gimeno, J. Adv. Synth. Catal.
2006, 348, 93e100; (f) Díaz-Alvarez, A. E.; Crochet, P.; Zablocka, M.; Duhayon,
C.; Cadierno, V.; Gimeno, J.; Majoral, J. P. Adv. Synth. Catal. 2006, 348,
ꢀ
ꢀ
1671e1679; (g) Crochet, P.; Fernandez-Zumel, M. A.; Gimeno, J.; Scheele, M.
Organometallics 2006, 25, 4846e4849; (h) Cadierno, V.; Gimeno, J.; Nebra, N.
Chem.dEur. J. 2007, 13, 6590e6594; (i) Cadierno, V.; Crochet, P.; Gimeno, J.
Synlett 2008, 1105e1124; (j) Lastra-Barreira, B.; Díez, J.; Crochet, P. Green Chem.
Supplementary data
Copies of the 1H and 13C{1H} NMR spectra of all compounds
synthesized in this work. Supplementary data related to this article
can be found in the online version, at doi:10.1016/j.tet.2012.01.083.
ꢀ
ꢀ
2009, 11, 1681e1686; (k) Fernandez-Zumel, M. A.; Lastra-Barreira, B.; Scheele,
M.; Díez, J.; Crochet, P.; Gimeno, J. Dalton Trans. 2010, 39, 7780e7785; (l)
García-Garrido, S. E.; Francos, J.; Cadierno, V.; Basset, J.-M.; Polshettiwar, V.

ꢀ
2620
A.E. Díaz-Alvarez et al. / Tetrahedron 68 (2012) 2611e2620
ꢀ
ChemSusChem 2011, 4, 104e111; (m) Varela-Alvarez, A.; Sordo, J. A.; Piedra, E.;
Nebra, N.; Cadierno, V.; Gimeno, J. Chem.dEur. J. 2011, 17, 10583e10599.
11. (a) Lastra-Barreira, B.; Crochet, P. Green Chem. 2010, 12, 1311e1314; (b) Lastra-
Barreira, B.; Francos, J.; Crochet, P.; Cadierno, V. Green Chem. 2011, 13, 307e313.
17. Although, in general, the catalytic isomerization of allylbenzenes results in
products with predominantly the trans alkene geometry (see Ref. 9) no pre-
vious data for the particular case of allylphenyl esters are available. However,
we must note that the use of complexes [RuCl2(PPh3)3], [RuCl2(DMSO)4],
12. For a review on the chemistry and catalytic applications of complex [{RuCl(
Cl)(h3 3-C10H16)}2] and its derivatives, see: Cadierno, V.; Crochet, P.; García-
Garrido, S. E.; Gimeno, J. Curr. Org. Chem. 2006, 10, 165e183.
13. (a) Porri, L.; Gallazzi, M. C.; Colombo, A.; Allegra, G. Tetrahedron Lett. 1965, 47,
4187e4189; (b) Salzer, A.; Bauer, A.; Podewils, F. In Synthetic Methods of Organo-
metallic and Inorganic Chemistry; Herrmann, W. A., Ed.; Thieme: Stuttgart,
2000; Vol. 9, pp 36e38; (c) Salzer, A.; Bauer, A.; Geyser, S.; Podewils, F.; Turpin,
G. C.; Ernst, R. D. Inorg. Synth. 2004, 34, 59e65.
14. See, for example: (a) Sorensen, J. S.; Sorensen, N. A. Acta Chem. Scand. 1966, 20,
992e1002; (b) D’Albuquerque, I. L.; Monache, F. D.; Ferrari, F.; Marini-Bettolo,
G. B. Gazz. Chim. Ital. 1968, 98, 1189e1196; (c) Bohlmann, F.; Zdero, C. Chem. Ber.
1969, 102, 1691e1697; (d) Bohlmann, F.; Zdero, C. Phytochemistry 1979, 18,
145e147; (e) Kleiman, R.; Plattner, R. D.; Weisleder, D. J. Nat. Prod. 1988, 51,
249e256; (f) Ahmed, M.; Gunatilaka, A. A. L. Pharmazie 1988, 43, 372e373; (g)
Merkel, B.; Reichling, J. Z. Naturforsch. 1990, 45c, 602e606; (h) Reichling, J.;
Merkel, B.; Hofmeister, P. J. Nat. Prod. 1991, 54, 1416e1418; (i) Bos, R.; Woer-
m
-
[{RuCl(
m
-Cl)(h
6-p-cymene)}2],
[RuCl(
5-C9H7)(PPh3)2]
[RuCl2(
h
6-p-cymene)(PPh3)], [RuCl(h5
or : :h
[RuCl2(h3 h2 3-C12H18)]
-
:
h
C5H5)(PPh3)2],
h
(C12H18¼dodeca-2,6,10-triene-1,12-diyl) as catalysts also resulted in the exclu-
sive formation of (E)-11a, suggesting that this isomer is particularly favoured
with respect to the Z one. We must also note that the activity of all these
complexes was comparatively lower to that shown by [{RuCl(
C10H16)}2]. The most active, i.e., the indenyl-ruthenium(II) complex [RuCl(h5
C9H7)(PPh3)2] (1 mol %), led to 11a in 82% GC-yield after 4 h of heating at 80 ꢀ
m
-Cl)(h3
:
h3
-
C
-
€
€
in methanol (to be compared with the entry 1 of Table 1). The stronger Lewis-
acid character of the ruthenium centres in [{RuCl(
-Cl)(h3 3-C10H16)}2], which
facilitates the generation of the catalytically active RueH species from metha-
nol through -hydride elimination in the in situ formed RueOMe in-
m
:h
b
termediates, could explain the higher reactivity observed. In addition,
coordination of the allylic C]C bond of the substrate to the metal should also
be favoured in Ru(IV) versus Ru(II) species.
18. (a) Smirnova, L. S.; Abduazimov, K. A. Khim. Prir. Soedin. 1992, 564e567; (b)
Maksomov, V. I.; Yartseva, N. G.; Zalesskaya, T. E.; Madaeva, O. S. Zh. Obshch.
Khim. 1950, 20, 2194e2201.
€
denbag, H. J.; Hendriks, H.; Sidik; Wikstrom, H. V.; Scheffer, J. J. C. Flavour
Fragrance J. 1996, 11, 321e326; (j) Santos, P. M.; Figueiredo, A. C.; Oliveira, M. M.;
Barroso, J. G.; Pedro, L. G.; Deans, S. G.; Younus, A. K. M.; Scheffer, J. J. C. Phy-
tochemistry 1998, 48, 455e460; (k) Tabanca, N.; Khan, S. I.; Bedir, E.; Anna-
varapu, S.; Willett, K.; Khan, I. A.; Kirimer, N.; Baser, K. H. C. Planta Med. 2004,
70, 728e735; (l) Tabanca, N.; Bedir, E.; Ferreira, D.; Slade, D.; Wedge, D. E.;
Jacob, M. R.; Khan, S. I.; Kirimer, N.; Baser, K. H. C.; Khan, I. A. Chem. Biodivers.
2005, 2, 221e232; (m) Tabanca, N.; Demerci, B.; Kirimer, N.; Baser, K. H. C.;
Bedir, E.; Khan, I. A.; Wedge, D. E. J. Chromatogr., A 2005, 1097, 192e198; (n)
Sampson, B. J.; Tabanca, N.; Kirimer, N.; Demerci, B.; Baser, K. H. C.; Khan, I. A.;
Spiers, J. M.; Wedge, D. E. Pest Manag. Sci. 2005, 61, 1122e1128; (o) Tabanca, N.;
Demerci, B.; Ozek, T.; Kirimer, N.; Baser, K. H. C.; Bedir, E.; Khan, I. A.; Wedge, D.
E. J. Chromatogr., A 2006, 1117, 194e205; (p) Baser, K. H. C.; Tabanca, N.; Kirimer,
N.; Bedir, E.; Khan, I. A.; Wedge, D. E. Pure Appl. Chem. 2007, 79, 539e556; (q)
Tabanca, N.; Ma, G.; Pasco, D. S.; Bedir, E.; Kirimer, N.; Baser, K. H. C.; Khan, I. A.;
Khan, S. I. Phytother. Res. 2007, 21, 741e745; (r) Lanfranchi, D.-A.; Laouer, H.;
Kolli, M. E.; Prado, S.; Maulay-Bailly, C.; Baldovini, N. J. Agric. Food Chem. 2010,
58, 2174e2179.
ꢀ
19. For related acid-promoted dimerizations of styrenes, see: Fornes, V.; García, H.;
ꢀ
Martí, V.; Fernandez, L. Tetrahedron 1998, 54, 3827e3832.
20. Okano, K.; Okuyama, K.-I.; Fukuyama, T.; Tokuyama, H. Synlett 2008,
1977e1980.
21. Gu, W.; She, X.; Pan, X.; Yang, T.-K. Tetrahedron: Asymmetry 1998, 9, 1377e1380.
22. For reviews on the Claisen rearrangement, see: (a) Castro, A. M. M. Chem. Rev.
2004, 104, 2939e3002; (b) Claisen Rearrangement; Hiersemann, M., Nubbe-
meyer, U., Eds.; Wiley-VCH: Weinheim, 2007.
23. This negative result is not surprising since sulphur species are well-known
poisons for homogeneous catalysts due to the formation of strong metal-
esulphur bonds. See, for example: Dunleavy, J. Platinum Metals Rev. 2006, 50,
110.
24. Mal, D.; Pahari, P.; Senapati, B. K. Tetrahedron Lett. 2005, 46, 2097e2100.
25. Lin, Y.-L.; Cheng, J.-Y.; Chu, Y.-H. Tetrahedron 2007, 63, 10949e10957.
26. Adibi, H.; Mojarrad, J. S.; Asgharloo, H.; Zarrini, G. Med. Chem. Res. 2011, 20,
1318e1324.
15. (a) Compounds of type C are generated by plants through a biosynthetic
pathway involving the enzymatic acylation of the corresponding (E)-(1-
propenyl)phenol with carboxylic acids: Tabanca, N.; Douglas, A. W.; Bedir, E.;
Dayan, F. E.; Kirimer, N.; Baser, K. H. C.; Aytac, Z.; Khan, I. A.; Scheffler, B. E. Plant
Genet. Res. 2005, 3, 149e169 and references cited therein; (b) Extraction from
essential oils of Pimpinella species is the main route of access to these com-
pounds (see Ref. 14).
27. Goruin, J. H.; Harfenist, M. Ger. Pat. DE2921824, 1979.
28. Takahashi, T.; Kai, K.; Uchida, H. Jpn. Pat. JP07-206941, 1995.
29. Kazuno, K.; Yamazaki, Y. Jpn. Pat. JP07-010727, 1995.
30. Priestap, H. A.; Bennett, B. C.; Quirke, J. M. E. J. Essent. Oil Res. 2008, 20,
396e402.
31. Hendriks, H.; Smith, D.; Hazelhoff, B. Phytochemistry 1977, 16, 1853e1854.
32. Sadeghian, H.; Seyedi, S. M.; Saberi, M. R.; Arghiani, Z.; Riazi, M. Bioorg. Med.
Chem. 2008, 16, 890e901.
16. The utilization of glycerol as a green reaction solvent for synthetic organic
chemistry is currently a highly active research field that has as main objective
33. Seyedi, S. M.; Jafari, Z.; Attaran, N.; Sadeghian, H.; Saberi, M. R.; Riazi, M. M.
the valorization of a waste generated by the biodiesel industry. For recent re-
ˇ
Bioorg. Med. Chem. 2009, 17, 1614e1622.
ꢀ
views on this topic, see: (a) Gu, Y.; Jerome, F. Green Chem. 2010, 12, 1127e1138;
34. Furuhata, A.; Takagi, K.; Kojo, K. Jpn. Pat. JP59-065035, 1984.
35. von Massow, F.; Smith, M. A. R. J. Chem. Soc., Perkin Trans. 2 1976, 977e980.
36. Tho, F. C.; Natova, L.; Ruschev, D. J. Therm. Anal. 1991, 37, 2723e2727.
ꢀ
(b) Díaz-Alvarez, A. E.; Francos, J.; Lastra-Barreira, B.; Crochet, P.; Cadierno, V.
Chem. Commun. 2011, 6208e6227.