Platinum-catalyzed multi-step reaction of propargyl alcohols with N-heteroaromatics

Article abstract of DOI:10.1002/asia.200900318

N-Methyl indole reacts with but-2-yn-1-ol in the presence of PtCl ₂ in MeOH giving indole derivatives having a substituted 3-oxobutyl group at the 3-position in good yield. Under the reaction conditions, various substituted indoles and substituted propargyl alcohols are successfully involved in the reaction giving the corresponding addition products in good to moderate yields. The catalytic reaction can be further extended to N-phenyl pyrrole. In the present multi-step reaction, PtCl2 likely plays dual roles: as the catalyst for the rearrangement of proparg-yl alcohols to the corresponding alken-yl ketones and as the catalyst for the addition of indoles to the alkenyl ke-tones. Experimental evidence is provided to support the proposed mechanism.

Full text of DOI:10.1002/asia.200900318

DOI: 10.1002/asia.200900318
Platinum-Catalyzed Multi-Step Reaction of Propargyl Alcohols with N-
Heteroaromatics
Sivakolundu Bhuvaneswari, Masilamani Jeganmohan, and Chien-Hong Cheng*[a]
Abstract: N-Methyl indole reacts with
but-2-yn-1-ol in the presence of PtCl2
in MeOH giving indole derivatives
having a substituted 3-oxobutyl group
at the 3-position in good yield. Under
the reaction conditions, various substi-
tuted indoles and substituted propargyl
alcohols are successfully involved in
the reaction giving the corresponding
addition products in good to moderate
yields. The catalytic reaction can be
further extended to N-phenyl pyrrole.
In the present multi-step reaction,
PtCl2 likely plays dual roles: as the cat-
alyst for the rearrangement of proparg-
yl alcohols to the corresponding alken-
yl ketones and as the catalyst for the
addition of indoles to the alkenyl ke-
tones. Experimental evidence is provid-
ed to support the proposed mechanism.
Keywords: alcohols · alkylation ·
ketones · nucleophilic addition ·
platinum
Introduction
reactions[6] prompted us to investigate the reaction of substi-
tuted propargyl alcohols and N-heteroaromatics.
The development of multi-step reactions in one pot, without
isolating the intermediate and without changing the reaction
conditions, is highly important in organic synthesis. Various
transition-metal complexes have successfully catalyzed
multi-step reactions in one pot with the construction of di-
verse organic molecules with maximized molecular complex-
ity and minimized organic wastes.[1] Recently, gold and plati-
num complexes have gained much attention in these types
of reaction.[2–3] We reported a platinum-catalyzed multi-step
reaction of alkynyl alcohols with N-heteroaromatics provid-
ing indole derivatives consisting of a cyclic ether group at
the 3-position.[4] The multi-step reaction proceeds by hydro-
alkynylation of alkynyl alcohols in the presence of PtCl2 to
Results and Discussion
In the presence of a catalytic amount of PtCl2 (5 mol%), N-
methyl indole (1a) reacted with but-2-yn-1-ol (2a) in
MeOH at 558C for 20 h to give indole derivative 3a having
a 3-oxobutyl group at the 3-position with a yield of isolated
product of 85% (Scheme 1). The catalytic reaction is com-
À
give cyclic enol ethers. Later, the C H bond of indole adds
to the cyclic enol ether in the presence of PtCl2. A similar
sequential multi-step reaction of substituted alkynes with
various nucleophiles have also been observed in the litera-
ture.[5] Our continuous interest in metal-catalyzed multi-step
Scheme 1. Platinum-catalyzed multi-step reaction of N-methyl indole
with but-2-yn-1-ol.
[a] Dr. S. Bhuvaneswari, Dr. M. Jeganmohan, Prof. Dr. C.-H. Cheng
Department of Chemistry
pletely atom economic with no loss of any atom from the
two reactants in the product. Notably, C3-substituted indole
derivatives exhibit a variety of biological activities and are
important building blocks for the synthesis of biologically
active compounds and natural products.[7] Mostly, compound
3 was prepared by the addition of 1a to a,b-unsaturated
ketone in the presence of metal catalysts.
National Tsing Hua University
Hsinchu 30013 (Taiwan)
Fax : (+886)3-572-4698
E-mail: chcheng@mx.nthu.edu.tw
Homepage: http://mx.nthu.edu.tw/%7Echcheng
Supporting information for this article is available on the WWW
under http://dx.doi.org/10.1002/asia.200900318.
Chem. Asian J. 2010, 5, 141 – 146
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141

FULL PAPERS
Table 1. Results of the multi-step reaction of substituted indoles with
but-2-yn-1-ol.[a]
Optimization Studies
Entry
1
Product 3
Yield [%][b]
To optimize the present reaction, the catalytic activities of
various gold complexes and PtCl2 in the reaction between
1a and 2a in MeOH at 558C for 20 h were tested. Gold
1
81
complexes such as AuCl, AuCl3, AuClACTHNUTRGEN(UNG PPh3), and
NaAuCl4·2H2O were totally inactive for the reaction.[8]
There was no improvement of the reaction even when addi-
tives, such as AgOTf and AgSbF6, were added with the gold
complexes. Gratifyingly, when PtCl2 was used as the catalyst,
3a was observed in a yield of 92% determined by the
1H NMR integration method using mesitylene as an internal
standard. Addition of a supporting ligand, such as norborna-
2
85
80
15
87
3
diene, norbornene, COD, PPh3, PACHTUNRTGNEUNG(2-furyl)3, and dppe, or an
additive, such as AgOTf and AgSbF6, to the PtCl2-catalyzed
solution strongly retarded the catalytic reaction, and no 3a
was formed. Of the solvents tested, MeOH or EtOH ap-
pears to be the choice for the present catalytic reaction
giving 3a in 92 and 91% yields, respectively. The other sol-
vents, THF, CH2Cl2, toluene, CH3CN, and DMF, were totally
ineffective for the reaction. When the catalytic reaction was
carried out in THF in the presence of 10 equiv of MeOH,
product 3a was observed in moderate 65% yield. The reac-
tion of 1a with 2a also proceeded in the presence of PtCl2
in MeOH at room temperature giving product 3a in a yield
of 95%. However, a longer reaction period of 40 h was nec-
essary to complete the reaction. Based on these optimiza-
tion studies, we chose PtCl2 as the catalyst and MeOH as
the solvent in the following reactions.
4
5[c]
6
7
8
78
55
59
Multi-Step Reaction of Various Substituted Indoles with
But-2-yn-1-ol
The results of reaction of indoles 1 with but-2-yn-1-ol (2a)
were summarized in Table 1. 5-Methoxy-1-methyl-1H-indole
(1b) efficiently reacted with 2a in the presence of PtCl2 in
methanol providing an alkylation product 3b at the 3-posi-
tion of N-methyl indole in 81% yield (entry 1). Other 5-sub-
stituted N-methyl indoles including 1c (5-Br), 1d (5-I), and
1e (5-NO2) also participated in the reaction with 2a afford-
ing products 3c–e in 85, 80, and 15% yields, respectively
(entries 2–4). Both 6-methoxy (1 f) and 7-methoxy (1g) in-
doles underwent alkylation with propargyl alcohol 2a fur-
nishing products 3 f and 3g in 87 and 78% yields, respective-
ly (entries 5 and 6), but the alkylation reaction of 1 f was
faster completing the reaction in 14 h (entry 5). It appears
that indoles with electron-donating substituents gave higher
yields when compared with those having electron-withdraw-
ing substitutents. As expected, sterically hindered 2-methyl
N-methyl indole (1h) afforded 3h in 55% yield (entry 7).
[a] Unless otherwise mentioned, all reactions were carried out using in-
doles 1 (1.0 mmol), but-2-yn-1-ol (2a) (1.30 mmol), PtCl2 (5 mol%), and
MeOH at 558C for 20 h. [b] Yield of isolated product. [c] Reaction was
carried out at 558C for 14 h.
The electronic effect of the N-substituent of the indole de-
rivative was also examined. Thus, indole (1i) reacted with
2a to give the corresponding alkylation product 3i in 59%
yield (entry 8). However, N-acetyl indole and N-sulphonyl
indole were totally ineffective for the reaction. The results
show that an electron-donating substituent at the benzo-ring
or at the nitrogen atom of indoles greatly enhances the yield
of product 3.
Abstract in Chinese:
Multi-Step Reaction of N-Methyl Indoles with Substituted
Propargyl Alcohols
The reaction of several substituted propargyl alcohols 2b–g
with 1a were also tested (Table 2). Thus, pent-2-yn-1-ol (2b)
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Chem. Asian J. 2010, 5, 141 – 146

Platinum-Catalyzed Multi-Step Reaction
Table 2. Results of the multi-step reaction of N-methyl indole with sub-
stituted propargyl alcohols 2b–g.[a]
of 1j with 2a in the presence of PtCl2 in MeOH at 558C for
24h afforded product 3p, a C-2 alkylation product of pyr-
role 1j, in 72% yield. Similarly, 1j reacted with 2-thienyl-
substituted propargyl alcohol 2e giving 3q in 69% yield.
Entry
2
Product 3
Yield [%][b]
1
82
Addition Reaction of 3-Phenylpropargyl Alcohol with
Alcohols
The reaction of 3-phenylpropargyl alcohol 2d with MeOH
at 558C in the presence of PtCl2 (5 mol%) for 16h without
N-methyl indole (1a), gave product 4a in 93% yield
(Table 3, entry 1). Other alcohols including EtOH, n-hexa-
2
3
4
80
75
73
Table 3. Results of the multi-step reaction of 3-phenylpropargyl alcohol
with alcohols.[a]
Entry
alcohols
Product 4
Yield [%][b]
1
MeOH
93
5[c]
65
57
2
EtOH
95
92
75
3[c]
n-hexanol/THF
iPrOH
6[c]
4[d]
[a] Unless otherwise mentioned, all reactions were carried out using N-
methyl indole (1a) (1.0 mmol), propargyl alcohols 2b–g (1.20 mmol),
PtCl2 (5 mol%), and MeOH at 558C for 20 h. [b] Yield of isolated prod-
uct. [c] Reaction was carried out at 558C for 24 h.
5[d]
cyclohexanol
57
73
6
tBuOH
and hex-2-yn-1-ol (2c) afforded 3j and 3k in 82 and 80%
yields (entries 1 and 2). 3-Phenylprop-2-yn-1-ol (2d) and 3-
(thiophen-2-yl)prop-2-yn-1-ol (2e) gave alkylation products
3l and 3m in 75 and 73% yields, respectively (entries 3 and
4). Interestingly, sterically hindered propargyl alcohols 2 f
and 2g also reacted efficiently with 1a giving 3n and 3o, re-
spectively, albeit in moderate yields (entries 5 and 6).
7[e]
8[e]
H2O/THF
THF
4 f
–
35
0
[a] Unless otherwise mentioned, all reactions were carried out using 3-
phenylpropargyl alcohol 2d (1.00 mmol), alcohols (3.0 mL), and PtCl2
(5 mol%) at 558C for 16 h. [b] Yield of isolated product. [c] 10 equiv of
n-hexanol in THF (6.0 mL). [d] Product 4 f was observed in 19% yield in
entry 4 and 39% yield in entry 5. [e] THF (6.0 mL) was added.
Multi-Step Reaction of N-Phenyl Pyrrole with Substituted
nol, iPrOH, and cyclohexanol also reacted similarly with 2d
providing addition products 4b–e in excellent yields (en-
tries 2–5). For the reaction of iPrOH and cyclohexanol with
2d, another product, phenyl vinyl ketone 4 f, presumably a
rearrangement product of 2d, was observed in 19 and 39%
yields, respectively. However, only 4 f was observed in 73%
yield when 2d was heated in tBuOH (entry 6). Similarly, in
the presence of water, phenyl vinyl ketone 4 f was also ob-
served, albeit only in 35% yield (entry 7). Notably, when 2d
was heated in THF without alcohol, no rearrangement prod-
uct 4 f was observed. An addition reaction of alcohols to
propargyl alcohols leading to b-alkoxy ketones 4a–e is un-
known in the literature.
Propargyl Alcohols
The scope of the present catalytic reaction can be successful-
ly extended to N-phenyl pyrrole (1j) (Scheme 2). Treatment
Scheme 2. Platinum-catalyzed multi-step reaction of N-phenyl pyrrole
with substituted propargyl alcohols.
Chem. Asian J. 2010, 5, 141 – 146
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143

C.-H. Cheng et al.
FULL PAPERS
Condensation Reaction of Tertiary Propargylic Alcohols
Various gold complexes were known to catalyze the trans-
formation of propargyl alcohols to a,b-unsaturated carbonyl
compounds.[8] However, the catalytic reaction was limited to
secondary and tertiary propargyl alcohols.[8a–d] Very recently,
Akai and co-workers reported a Mo, Au, and Ag-catalyzed
transformation of propargyl alcohols into a,b-unsaturated
carbonyl compounds.[8e] The method successfully converts
primary, secondary, and tertiary propargyl alcohols into a,b-
unsaturated carbonyl compounds. For comparison, the pres-
ent platinum-catalyzed reaction efficiently converts primary
and secondary propargyl alcohols into a,b-unsaturated ke-
tones, but converts tertiary propargyl alcohol 2h to the cor-
responding ethers 5a–b (Scheme 3).
Scheme 4. Proposed mechanism for the platinum-catalyzed multi-step re-
action.
To support that methoxy allene 7 and alkenyl ketone 9
(Table 3) are intermediates, we have performed the follow-
ing two reactions. One is the reaction of N-methyl indole
(1a) with synthesized methoxy allene 12 and H2O (5 equiv)
in the presence of PtCl2 in THF at 558C to afford product
3r in 73% yield. Another one is the reaction of indole with
commercially available ethyl vinyl ketone 9a in the presence
of PtCl2 in MeOH at room temperature to give alkylation
product 3k in 87% yield (Scheme 5).
Scheme 3. Platinum-catalyzed condensation reaction of tertiary propargyl
alcohol.
The condensation reaction of propargylic alcohols with al-
cohols to give propargylic ethers in the presence of gold
complexes has been reported.[8d] However, in this report,
secondary propargylic alcohols reacted with EtOH giving
the corresponding propargylic ethers, and tertiary propargyl-
ic alcohols were converted to a,b-unsaturated ketones. In
contrast, in the present platinum-catalyzed reaction, only
tertiary propargylic alcohols lead to ether products
(Scheme 3).
Mechanistic Discussion
On the basis of the known transformation of propargyl alco-
hols into a,b-unsaturated ketones,[8–9] a possible mechanism
of the present multi-step reaction is outlined in Scheme 4.
The catalytic reaction is likely divided into two parts, and
the platinum catalyst likely plays dual roles: as the catalyst
for the rearrangement of propargyl alcohols 2 to the corre-
sponding alkenyl ketones 9, and as the catalyst for the addi-
tion of indoles to the alkenyl ketones. In the first part, coor-
dination of a carbon–carbon triple bond of propargyl alco-
hol 2 to PtCl2 gives platinum-p-alkynyl complex 6. Regiose-
lective nucleophilic addition of MeOH to the R6-substituted
carbon of alkyne in platinum-p-alkynyl complex 6 followed
by dehydration provides platinum–allenyl complex 7. Ex-
change of water with the methoxy group in 7 and elimina-
tion of PtCl2, gives the a,b-unsaturated ketone 9. In the
second part, coordination of the carbonyl group of 9 to
PtCl2 followed by nucleophilic addition of indole 1 to 10, af-
fords intermediate 11. Protonation of intermediate 11 pro-
vides alkylation product 3 and regenerates PtCl2. It is the
first metal-catalyzed transformation of propargyl alcohol
into a,b-unsaturated ketone, and then, the addition of heter-
oaromatics to the a,b-unsaturated ketone.
Scheme 5. Mechanistic evidences.
Alkylation of N-Methyl Indole with Alkyl Ether
The addition of alcohol to a,b-enone 9 catalyzed by PtCl2
giving b-alkoxy ketone 4 appears to be a reversible process
(Scheme 6). For example, when product 4a (entry 1,
Table 3) was re-dissolved in THF in the presence of PtCl2, a
small amount of enone 9 (~10% by NMR) was produced in
the solution. Furthermore, if 4a–b were allowed to react
with N-methyl indole (1a) in the presence of PtCl2 in
MeOH at 558C, the alkylation product 3l was also observed
in 79 and 76% yields, respectively (Scheme 6). The reaction
of N-methyl indole with alkyl ether 4 is unprecedented in
the literature. We think that compound 4 goes back to the
corresponding enone and alcohol, and then the addition of
1a to enone occurs. The addition of alcohol to a,b-enone 9
is confirmed by the observation of b-alkoxy ketone 4g in
144
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Chem. Asian J. 2010, 5, 141 – 146

Platinum-Catalyzed Multi-Step Reaction
19.2 ppm; HRMS: m/z (%) calcd for C13H14BrNO: 279.0259; found:
279.0238.
1-(1-Methyl-1H-indol-3-yl)hexan-3-one (3k): Pale yellow oil; IR (KBr):
1
n˜ =3052, 1700
N
(d, J=7.2 Hz, 1H), 7.25 (d, J=7.6 Hz, 1H), 7.20 (t, J=7.2 Hz, 1H), 7.06
(t, J=7.2 Hz, 1H), 6.84 (s, 1H), 3.74 (s, 3H), 3.04 (t, J=6.8 Hz, 2H), 2.79
(t, J=7.6 Hz, 2H), 2.37 (t, J=7.6 Hz, 2H), 1.63–1.57 (m, 2H), 0.89 ppm
(t, J=7.2 Hz, 3H); 13C NMR (100 MHz, CDCl3): d=211.1, 127.8, 126.6,
121.8, 119.0, 118.9, 114.1, 109.4, 45.1, 43.6, 32.8, 19.5, 17.5, 14.0 ppm;
HRMS: m/z (%) calcd for C15H19NO: 229.1467; found: 229.1468.
4-(1-Phenyl-1H-pyrrol-2-yl)butan-2-one (3p): Pale yellow oil; IR (KBr):
1
n˜ =3106, 1712
N
(t, J=7.5 Hz, 2H), 7.35 (t, J=8.0 Hz, 1H), 7.29 (d, J=7.5 Hz, 2H), 6.73
(dd, J=2.5, 1.5 Hz, 1H), 6.18 (t, J=4.0 Hz, 1H), 6.00 (dd, J=3.0, 1.5 Hz,
1H), 2.80 (t, J=7.5 Hz, 2H), 2.63 (t, J=7.5 Hz, 2H), 2.07 ppm (s, 3H);
13C NMR (125 MHz, CDCl3): d=207.8, 140.1, 132.2, 129.2, 127.3, 126.1,
122.0, 107.9, 106.7, 42.8, 30.0, 21.0 ppm; HRMS: m/z (%) calcd for
C14H15NO: 213.1154; found: 213.1150.
Scheme 6. Platinum-catalyzed alkylation of N-methyl indole with alkyl
ethers.
the addition reaction of n-hexanol with ethyl vinyl ketone in
the presence of PtCl2.
General Procedure for the Reaction of 3-Phenylpropargyl Alcohols 2d
with Alcohols
A 25 mL round-bottomed flask containing PtCl2 (0.050 mmol, 5.0 mol%)
was evacuated and purged with nitrogen gas three times. Alcohols
(3.0 mL) and 3-phenylpropargyl alcohol 2d (1.00 mmol) were sequential-
ly added to the system, and the reaction mixture was stirred at 558C for
16 h. The mixture was filtered through a short celite and silica gel pad,
and washed with dichloromethane several times. The filtrate was concen-
trated, and the residue was purified on a silica gel column using hexanes-
ethyl acetate as eluent to afford product 4. The catalytic reaction also
worked equally when THF (6.0 mL) was used as the solvent in the pres-
ence of 10 equiv of alcohols. Product 4g was synthesized according to a
similar procedure by using ethyl vinyl ketone (1.0 mmol) instead of prop-
argyl alcohol.
Conclusions
We have developed a platinum-catalyzed multi-step reaction
of N-heteroaromatics with propargyl alcohols. The platinum
catalyst plays dual roles in this reaction. It first catalyzes the
transformation of propargyl alcohol into a,b-unsaturated
ketone and then the addition of heteroaromatics to the a,b-
unsaturated ketone in one pot. Further studies of alkylation
of other heteroaromatics with propargyl alcohols, addition
of other nucleophiles to propargyl alcohols, and the detailed
study of the mechanism are in progress.
3-Methoxy-1-phenylpropan-1-one (4a): Pale yellow oil; IR (KBr): n˜ =
1
3034, 1693ACTHNUTRGNEUNG
(nCO), 1554, 754 cmÀ1; H NMR (400 MHz, CDCl3): d=7.96 (d,
J=7.2 Hz, 2H), 7.56 (t, J=7.6 Hz, 1H), 7.46 (t, J=8.0 Hz, 2H), 3.82 (t,
J=6.4 Hz, 2H), 3.38 (s, 3H), 3.24 ppm (t, J=6.4 Hz, 2H); 13C NMR
(100 MHz, CDCl3): d=198.7, 137.5, 133.6, 128.9, 128.6, 66.9, 65.9,
39.5 ppm; HRMS: m/z (%) calcd for C10H12O2: 164.0837; found:
164.0840.
Experimental Section
3-(Hexyloxy)-1-phenylpropan-1-one (4c): Pale yellow oil; IR (KBr): n˜ =
General Procedure for the Multi-Step Reaction of Propargyl Alcohols
with Indoles
1
3065, 1698
N
J=7.2 Hz, 2H), 7.52 (t, J=6.8 Hz, 1H), 7.43 (t, J=8.0 Hz, 2H), 3.83 (t,
J=6.8 Hz, 2H), 3.44 (t, J=6.4 Hz, 2H), 3.23 (t, J=6.4 Hz, 2H), 1.54 (t,
J=7.2 Hz, 2H), 1.29–1.26 (bs, 6H), 0.85 ppm (t, J=6.4 Hz, 3H);
13C NMR (CDCl3, 100 MHz): d=198.4, 136.9, 132.9, 128.4, 128.0, 71.3,
65.9, 38.8, 31.5, 29.5, 25.7, 22.5, 13.9 ppm; HRMS: m/z (%) calcd for
C15H22O2: 234.1620; found: 234.1614.
A 25 mL round-bottomed flask containing PtCl2 (0.050 mmol, 5.0 mol%)
was evacuated and purged with nitrogen gas three times. MeOH
(6.0 mL), indole (1.00 mmol), and propargyl alcohol (1.20 mmol) were se-
quentially added to the system and the reaction mixture was stirred at
558C for 20 h. The mixture was filtered through a short celite and silica
gel pad, and washed with dichloromethane several times. The filtrate was
concentrated, and the residue was purified on a silica gel column using
hexanes-ethyl acetate as eluent to afford the addition product 3. Products
3p–q were synthesized according to a similar procedure by using N-
phenyl pyrrole (1.0 mmol) instead of indole.
General Procedure for the Substitution Reaction of Tertiary Propargyl
Alcohol 2h with Alcohols
A 25 mL round-bottomed flask containing PtCl2 (0.050 mmol, 5.0 mol%)
was evacuated and purged with nitrogen gas three times. MeOH or
EtOH (6.0 mL), and tertiary propargyl alcohol 2h (1.00 mmol) were se-
quentially added to the system, and the reaction mixture was stirred at
558C for 24 h. The mixture was filtered through a short celite and silica
gel pad, and washed with dichloromethane several times. The filtrate was
concentrated, and the residue was purified on a silica gel column using
hexanes-ethyl acetate as eluent to afford product 5.
4-(1-Methyl-1H-indol-3-yl)butan-2-one (3a): Pale yellow oil; IR (KBr):
1
n˜ =3218, 1709
N
(d, J=6.5 Hz, 1H), 7.26 (d, J=6.5 Hz, 1H), 7.20 (t, J=5.5 Hz, 1H), 7.09
(t, J=5.5 Hz, 1H), 6.83 (s, 1H), 3.71 (s, 3H), 3.02 (t, J=6.0 Hz, 2H), 2.82
(t, J=6.5 Hz, 2H), 2.12 ppm (s, 3H); 13C NMR (125 MHz, CDCl3): d=
208.8, 136.9, 127.5, 126.8, 121.6, 118.7, 118.6, 113.6, 109.2, 44.3, 32.5, 30.0,
19.2 ppm; HRMS: m/z (%) calcd for C13H15NO: 201.1154; found:
201.1149.
(3-Ethoxy-3-methylpent-1-ynyl)benzene (5b). Pale yellow oil; IR (KBr):
4-(5-Bromo-1-methyl-1H-indol-3-yl)butan-2-one (3c): Pale yellow oil; IR
(nCO), 817 cmÀ1 1H NMR (400 MHz, CDCl3): d=7.46–7.42
n˜ =2977, 1666AHCTUNGTERNNUNG ;
(KBr): n˜ =3026, 1701
(nCO), 1542, 783 cmÀ1
;
1H NMR (400 MHz, CDCl3):
(bs, 2H), 7.30–7.28 (bs, 3H), 3.68 (q, J=3.6 Hz, 2H), 1.83–1.78 (m, 2H),
1.50 (s, 3H), 1.24 (t, J=7.2 Hz, 3H), 1.15 ppm (t, J=7.2 Hz, 3H);
13C NMR (100 MHz, CDCl3): d 132.1, 128.4, 128.3, 127.9, 90.9, 84.8, 73.8,
59.1, 34.3, 25.7, 15.7, 8.7 ppm; HRMS: m/z (%) calcd for C14H18O:
202.1358; found: 202.1361.
d=7.67 (d, J=2.0 Hz, 1H), 7.28 (dd, J=8.8, 1.6 Hz, 1H), 7.13 (d, J=
8.8 Hz, 1H), 6.84 (s, 1H), 3.70 (s, 3H), 2.96 (t, J=7.6 Hz, 2H), 2.79 (t,
J=7.6 Hz, 2H), 2.14 ppm (s, 3H); 13C NMR (100 MHz, CDCl3): d=
208.6, 135.9, 129.5, 127.9, 124.6, 121.5, 113.6, 112.4, 110.9, 44.3, 33.0, 30.3,
Chem. Asian J. 2010, 5, 141 – 146
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145

C.-H. Cheng et al.
FULL PAPERS
Spectral data of remaining compounds and copies of 1H and 13C NMR
spectra of all compounds are given in the Supporting Information.
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Acknowledgements
We thank the National Science Council (NSC-96-2113M-007-020-MY3)
of Republic of China for the support of this research. We would also like
to express our appreciation to Dr. Kanniyappan Parthasarathy for his as-
sistance in acquiring some of the spectral data.
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Received: July 27, 2009
Published online: November 26, 2009
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