SmI3-catalyzed addition of amines to α,β-unsaturated N-acylbenzotriazoles

Article abstract of DOI:10.1080/00397910802431180

The addition of amines to α,β-unsaturated N-acylbenzotriazoles could be catalyzed by samarium triiodide (SmI3) at ambient temperature. α,β-Unsaturated aliphatic N-acylbenzotriazoles afforded bis-addition products (β-amino amides), whereas N-cinnamoylbenzo

Full text of DOI:10.1080/00397910802431180

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SmI3-Catalyzed Addition of
Amines to α,β-Unsaturated N-
Acylbenzotriazoles
Xiaoxia Wang a , Liang He a , Zhifang Li b , Wencun
Wang a & Junhua Liu a
a Zhejiang Key Laboratory for Reactive Chemistry
on Solid Surfaces , College of Chemistry and Life
Sciences, Zhejiang Normal University , Jinhua, China
b Key Laboratory of Organosilicon Chemistry and
Material Technology of Ministry of Education,
Hangzhou Normal University , Hangzhou, China
Published online: 29 Jan 2009.
To cite this article: Xiaoxia Wang , Liang He , Zhifang Li , Wencun Wang & Junhua Liu
(2009) SmI3-Catalyzed Addition of Amines to α,β-Unsaturated N-Acylbenzotriazoles,
Synthetic Communications: An International Journal for Rapid Communication of
Synthetic Organic Chemistry, 39:5, 819-829, DOI: 10.1080/00397910802431180
To link to this article: http://dx.doi.org/10.1080/00397910802431180
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Synthetic Communications1, 39: 819–829, 2009
Copyright # Taylor & Francis Group, LLC
ISSN: 0039-7911 print=1532-2432 online
DOI: 10.1080/00397910802431180
SmI3-Catalyzed Addition of Amines to
a,b-Unsaturated N-Acylbenzotriazoles
Xiaoxia Wang,1 Liang He,1 Zhifang Li,2 Wencun Wang,1
and Junhua Liu1
1Zhejiang Key Laboratory for Reactive Chemistry on Solid Surfaces,
College of Chemistry and Life Sciences, Zhejiang Normal University,
Jinhua, China
2Key Laboratory of Organosilicon Chemistry and Material Technology of
Ministry of Education, Hangzhou Normal University, Hangzhou, China
Abstract: The addition of amines to a,b-unsaturated N-acylbenzotriazoles
could be catalyzed by samarium triiodide (SmI3) at ambient temperature. a,b-
Unsaturated aliphatic N-acylbenzotriazoles afforded bis-addition products
(b-amino amides), whereas N-cinnamoylbenzotriazoles gave acylated products
(cinnamoylamides) exclusively.
Keywords: Acylation, amines, bis-addition, SmI3, a,b-unsaturated N-acylbenzo-
triazoles
Much attention has been paid to the amine-mediated aza-Michael addi-
tion to a,b-unsaturated carbonyl compounds and their analogs (electron-
deficient alkenes) in recent years mainly because of the importance of the
resulting b-amino derivatives.[1]
a,b-Unsaturated N-acylbenzotriazoles, essentially a,b-unsaturated
amides due to the –C¼C–CO– structure included therein, can be viewed
as a special kind of a,b-unsaturated carbonyl compound. Although they
were frequently used as acylating reagents (1,2-addition reaction),[2] their
Received May 30, 2008.
Address correspondence to Xiaoxia Wang, Zhejiang Key Laboratory for
Reactive Chemistry on Solid Surfaces, College of Chemistry and Life Sciences,
Zhejiang Normal University, Jinhua 321004, China. E-mail: wangxiaoxia@
zjnu.cn
819

820
X. Wang et al.
potential to act as Michael addition acceptors has recently been
demonstrated.[3]
SmI3 was reported to be an efficient catalyst for the aza-Michael
addition between aromatic amines and a,b-unsaturated nitriles or
esters.[4] It was also found that aza-Michael addition, catalyzed by
samarium diiodide (SmI2), as well as bis-addition (Michael addition
followed by acylation)[5] could occur between aromatic amines and
a,b-unsaturated N-acyloxazolidinones.
Herein we report that with SmI3 as catalyst, both aliphatic and
aromatic amines undergo bis-addition with aliphatic a,b-unsaturated
N-acylbenzotriazoles, while they were acylated exclusively by N-cinna-
moylbenzotriazoles, to afford cinnamoylamides in good to excellent yields.
Our initial experiment engaged N-crotonylbenzotriaole and p-methy-
laniline as the substrates with the molar ratio of 1:1. THF, CH3CN, or
CH2Cl2 as the solvent and ZnCl2, AlCl3, or SmI3 as the catalyst were
screened to establish the optimized reaction conditions. It was found that
the reaction catalyzed by SmI3 (10 mol%) proceeded the most efficiently in
CH2Cl2. The product obtained was characterized as a bis-addition product
3a based on 1H NMR, 13C NMR, infrared (IR), mass spectrometry (MS),
and elemental analysis. Consequently, a 1:2 molar ratio of aliphatic a,b-
unsaturated N-acylbenzotriazole to amine was employed in subsequent
addition reactions (Scheme 1), and the results are summarized in Table 1.
To ascertain the sequence of the bis-addition, two control experi-
ments were carried out. First, a possible intermediate 5[3a] was reacted
with p-methoxyaniline (Scheme 2), and the anticipated acylation reac-
tion[6] did occur to afford unsymmetrical bis-addition product 6 in 80%
yield. Therefore, a reaction sequence of Michael addition followed by
acylation is reasonable.
Then an alternative reaction sequence of acylation followed by
Michael addition was also investigated. Thus a,b-unsaturated amide 7
Scheme 1. Bis-addition of amines to aliphatic a,b-unsaturated N-acylbenzotriazoles.

SmI3-Catalyzed Addition of Amines
821
Table 1. SmI3-catalyzed bis-addition of amines to aliphatic a,b-unsaturated
N-acylbenzotriazoles
Entry Substrates 1 R3 of amines 2 Products 3 Reaction time (h) Yield (%)a
1
2
3
4
5
1a
1a
1a
1a
1a
3a
3b
3c
3d
3e
18
12
8.5
14
22
73
75
82
77
66
6
7
1a
1b
n-C4H9-
3f
0.5
6
92
81
3g
aIsolated yields.
as the other possible intermediate for the bis-addition was reacted with
m-toluidine under the same conditions, only to find no reaction occurred
(Scheme 3). The fact that the bis-addition product 6 could not be
obtained this way indicates that the reaction sequence of acylation
followed by Michael addition can be excluded.
Scheme 2. Rationalization of the reaction sequence for the bis-addition.

822
X. Wang et al.
Scheme 3. Exclusion of an alternative reaction sequence for the bis-addition.
Subsequent studies employed N-cinnamoylbenzotriazoles as the
substrates to react with a series of amines. However, only the acylated
products were obtained in all cases even when the ratio of 1 to 2 was
1:2 (Scheme 4). The results are listed in Table 2. Aliphatic amines afford
better yields in shorter time than aromatic amines; aromatic amines with
electron-donating groups on the aromatic rings react more readily than
those with electron-withdrawing groups.
The formation of 4 instead of bis-addition product 3 can be ascribed
to steric hindrance resulting from the b-aryl substitution, which prohib-
ited the required reaction sequence where a Michael addition of amines
should take place first.
In conclusion, a,b-unsaturated N-acylbenzotriazoles reacting with a
series of amines could afford either bis-addition or acylated products
depending on the structure of the a,b-unsaturated N-acylbenzotriazoles.
The good regioselectivity and mild conditions of the reactions are extre-
mely useful for the preparation of b-amino amides and cinnamoylamides.
EXPERIMENTAL
Tetrahydrofuran (THF) was distilled from sodium-benzophenone imme-
diately prior to use. CH2Cl2 was a commercially available reagent used
without further treatment. Melting points are uncorrected. 1H NMR
(400-MHz) spectra were recorded on a Bruker AV400 NMR instrument
as CDCl3 solutions using TMS as internal standard. Chemical shifts (d)
are reported in parts per million (ppm) and coupling constants J are given
in hertz (Hz). IR spectra were recorded in film or using KBr disks with a
Nexus 670 Fourier transform infrared (FTIR) spectrometer. Mass spec-
Scheme 4. Acylation of amines with N-cinnamoylbenzotriazoles.

SmI3-Catalyzed Addition of Amines
823
Table 2. Acylation of amines with N-cinnamoylbenzotriazoles catalyzed by SmI3
Entry
1
Ar of 1
2
Products 4 Reaction time (h) Yield (%)a
4a
4b
4c
4d
4e
4f
19
12
20
2
85
86
72
84
89
88
2
3
4
5
6
7
n-C4H9NH2
n-C4H9NH2
3.5
2
b
—
4g
20
8
9
n-C4H9NH2
Et2NH
4h
4i
1.5
2
93
90
aIsolated yields.
bNo reaction.
tra were recorded on a HP 5989B MS spectrometer. Elemental analyses
were performed on a Vario-ELIII instrument.
General Procedure for the Preparation of 3 or 4
Sm powder (0.015 g, 0.1 mmol) and I2 (0.039 g, 0.015 mmol) were added
to 10 mL of dry THF. The mixture was stirred at rt for 0.5 h to obtain
the SmI3–THF solution. Removal of THF in vacuo followed by addition
of CH2Cl2 (10 mL) afforded an SmI3-CH2Cl2 suspension, to which was
then added aromatic or aliphatic amine (2 mmol for the formation of 3
and 1 mmol for 4) and a,b-unsaturated N-acylbenzotriazoles (1 mmol).
The mixture was stirred at rt for the time indicated in the table

824
X. Wang et al.
(monitored by thin-layer chromotography, TLC). The reaction was
quenched by dilute hydrochloric acid (1 N, 10 mL). The resulting reaction
mixture was extracted with CH2Cl2 (10 mL ꢀ 3), and the combined
organic layer was washed by saturated Na2CO3 and brine, then dried over
anhydrous Na2SO4. Removal of the solvent gave the products, which were
either pure enough for characterization or further purified by preparative
TLC with ethyl acetate and petroleum ether (1:6) as an eluent.
Data
Compound 3a
White solid, mp 103–105 ꢁC. nmax (KBr)=cmꢂ1: 3125, 1651, 1599, 1546,
1400. dH (CDCl3): 8.51 (br, s, 1H), 7.42 (d, J 7.6 Hz, 2H), 7.32–7.02
(m, 4H), 6.65 (d, J 7.6 Hz, 2H), 3.90 (m, 1H), 3.51 (br, s, 1H), 2.52 (d,
J 5.6 Hz, 2H), 2.30–2.25 (m, 6H), 1.27 (d, J 6.0 Hz, 3H). 13C NMR
(CDCl3): 169.5, 143.9, 135.3, 133.7, 130.0, 129.4, 126.8, 120.0, 115.3,
48.0, 43.5, 20.9, 20.8, 20.4. m=z (%): 282 (Mþ, 31.56), 267 (9.83), 134
(100). Anal. calcd. for C18H22N2O: C, 76.56; H, 7.85; N, 9.92. Found:
C, 76.29; H, 7.88; N, 9.78.
Compound 3b
White solid, mp 88–90 ꢁC. nmax (KBr)=cmꢂ1: 3278, 3137, 2965, 1649, 1600,
1550, 1441. dH (CDCl3): 8.33 (br, s, 1H), 7.44 (d, J 7.6 Hz, 2H), 7.29–7.10
(m, 5H), 6.80–6.72 (m, 3H), 3.99–3.98 (m, 1H), 3.76 (br, s, 1H), 2.59 (d, J
6.0 Hz, 2H), 1.32 (d, J 6.8 Hz, 3H). 13C NMR (CDCl3): 169.6, 146.4, 137.8,
129.5, 127.9, 124.2, 120.9, 120.0, 119.0, 47.4, 43.6, 20.9. m=z (%): 254 (Mþ,
30.09), 239 (9.08), 119 (100). Anal. calcd. for C16H18N2O: C, 75.56; H,
7.13; N, 11.01. Found: C, 75.38; H, 7.05; N, 11.10.
Compound 3c
White solid, mp 97–99 ꢁC. nmax (KBr)=cmꢂ1: 3284, 3130, 1649, 1600,
1512. dH (CDCl3): 8.70 (br, s, 1H), 7.35 (d, J 8.0 Hz, 2H), 6.82 (d, J
8.0 Hz, 4H), 6.73 (d, J 8.0 Hz, 2H), 3.84–3.81 (m, 1H), 3.77 (s, 6H),
2.53 (d, J 6.0 Hz, 2H), 1.26 (d, J 4.4 Hz, 3H). 13C NMR (CDCl3):
169.4, 156.2, 153.5, 140.0, 131.1, 121.7, 117.0, 115.0, 114.1, 55.7, 55.4,
49.0, 43.3, 20.9. m=z (%): 314 (Mþ, 5.74), 281 (4.58), 59 (100). Anal.
calcd. for C18H22N2O3: C, 68.77; H, 7.05; N, 8.91. Found: C, 68.91; H,
7.10; N, 8.78.

SmI3-Catalyzed Addition of Amines
825
Compound 3d
White solid, mp 148–150 ꢁC. nmax (KBr)=cmꢂ1: 3298, 3180, 3113, 2985,
2964, 2923, 1656, 1594, 1499. dH (CDCl3): 8.12 (br, s, 1H), 7.38 (d,
J 8.0 Hz, 2H), 7.25 (d, J 8.0 Hz, 2H), 7.16 (d, J 8.0 Hz, 2H), 6.64 (d,
J 8.0 Hz, 2H), 3.95–3.92 (m, 1H), 3.90 (br, s, 1H), 2.55 (d, J 4.0 Hz,
2H), 1.30 (d, J 4.0 Hz, 3H). 13C NMR (CDCl3): 169.2, 144.9, 136.2,
129.4, 129.3, 129.0, 123.7, 121.1, 115.7, 47.5, 43.4, 20.8. m=z (%): 323
(Mþ, 0.54), 220 (28.75), 205 (100). Anal. calcd. for C16H16Cl2N2O: C,
59.46; H, 4.99; N, 8.67. Found: C, 59.60; H, 5.06; N, 8.74.
Compound 3e
White solid, mp 116–118 ꢁC. nmax (KBr)=cmꢂ1: 3491, 3276, 3042, 2963,
2920, 1647, 1605, 1514. dH(CDCl3): 8.30 (br, s, 1H), 7.41–7.39 (d,
J 8.0 Hz, 2H), 7.20–7.01 (m, 4H), 6.78–6.71 (m, 2H), 4.09–4.04 (m,
1H), 2.67 (d, J 4.0 Hz, 2H), 2.17 (s, 3H), 2.05 (s, 3H), 1.35 (d, J 4.4.0
Hz, 3H). 13C NMR (CDCl3): 169.6, 144.4, 135.8, 130.6, 130.4, 128.7,
127.3, 126.7, 124.9, 123.4, 122.8, 118.5, 111.7, 46.9, 43.7, 21.1, 17.6.
m=z (%): 282 (Mþ, 39.25), 267 (9.27), 134 (100). Anal. calcd. for
C18H22N2O: C, 76.56; H, 7.85; N, 9.92. Found: C, 76.41; H, 7.92; N,
9.98.
Compound 3f
Colorless oil. nmax (film)=cmꢂ1: 3358, 3061, 2919, 1641. dH (CDCl3): 8.20
(br, s, 1H), 3.29–3.21 (m, 2H), 3.05–2.95 (m, 1H), 2.75–2.67 (m, 1H),
2.61–2.52 (m, 1H), 2.33 (dd, J 4.0, 15.6 Hz, 1H), 2.18 (dd, J 7.6,
15.6 Hz, 1H), 2.15 (br, s, 1H), 1.50–1.46 (m, 4H), 1.38–1.34 (m, 4H),
1.12 (d, J 6.4 Hz, 3H), 0.94–0.90 (m, 6H). 13C NMR (CDCl3): 172.0,
50.6, 46.3, 41.8, 38.6, 32.3, 31.6, 20.4, 20.3, 20.1, 13.8, 13.7. m=z (%):
214 (Mþ, 3.72), 199 (3.45), 171 (33.68), 99 (100). Anal. calcd. for
C12H26N2O: C, 67.24; H, 12.23; N, 13.07. Found: C, 67.41; H, 12.10;
N, 13.01.
Compound 3g
White solid, mp 140–142 ꢁC. nmax (KBr)=cmꢂ1: 3374, 3183, 3064, 2933,
1642, 1604, 1512. dH (CDCl3): 7.87 (br, s, 1H), 7.37 (d, J 8.0 Hz, 2H),
6.84–6.79 (m, 4H), 6.65 (d, J 8.0 Hz, 2H), 3.77 (s, 3H), 3.75 (s, 3H),
3.37? (dd, J 8.0, 12.0 Hz, 1H), 3.27 (dd, J 4.0, 16.0 Hz, 1H), 2.72–2.68

826
X. Wang et al.
(m, 1H), 1.28 (d, J 8.0 Hz, 3H). 13C NMR (CDCl3): 173.0, 156.4, 153.6,
140.3, 131.1, 121.7, 116.0, 115.1, 114.1, 55.8, 55.5, 49.7, 40.7, 15.5. m=z
(%): 220 (Mþ ꢂ 94, 21.96), 205 (100), 190 (23.43), 144 (19.25), 105 (13.46),
90 (22.47), 56 (48.63). Anal. calcd. for C18H22N2O3: C, 68.77; H, 7.05; N,
8.91. Found: C, 68.83; H, 7.13; N, 8.78.
Compound 4a
White solid, mp 152–154 ꢁC. nmax (KBr)=cmꢂ1: 3428, 3270, 3057, 1661,
1624, 1546. dH (CDCl3): 7.75 (d, J 15.2 Hz, 1H), 7.62 (d, J 8.0 Hz, 2H),
7.52–7.50 (m, 3H), 7.37–7.33 (m, 5H), 7.13 (t, J 7.2 Hz, 1H), 6.56 (d, J
15.2 Hz, 1H). 13C NMR (CDCl3): 166.7, 142.4, 138.0, 134.6, 129.9,
129.1, 128.8, 127.9, 124.4, 120.9, 120.0. m=z (%): 223 (M+, 32.53), 131
(100). Anal. calcd. for C15H13NO: C, 80.69; H, 5.87; N, 6.27. Found:
C, 80.89; H, 5.81; N, 6.18.
Compound 4b
White solid, mp 154–156 ꢁC. nmax (KBr)=cmꢂ1: 3428, 3308, 2931, 1659,
1624, 1513. dH (CDCl3): 7.64 (d, J 15.2 Hz, 1H), 7.54–7.52 (m, 4H),
7.40–7.36 (m, 4H), 6.88 (d, J 8.4 Hz, 2H), 6.54 (d, J 15.6 Hz, 1H), 3.80
(s, 3H). 13C NMR (CDCl3): 163.8, 156.5, 142.0, 134.7, 131.1, 129.9,
128.9, 127.9, 121.7, 120.9, 114.3, 55.5. m=z (%): 253 (Mþ, 0.47), 157
(29.53), 99 (100). Anal. calcd. for C16H15NO2: C, 75.87; H, 5.92; N,
5.53. Found: C, 75.73; H, 5.99; N, 5.40.
Compound 4c
White solid, mp 182–184 ꢁC (lit.[7] 185 ꢁC). nmax (KBr)=cmꢂ1: 3448, 3098,
2925, 1661, 1623. dH (CDCl3): 8.13 (br, s, 1H), 7.74 (d, J 15.6 Hz, 1H),
7.69–7.57 (m, 5H), 7.37–7.24 (m, 4H), 6.55 (d, J 15.6 Hz, 1H). 13C
NMR (CDCl3): 166.4, 144.0, 135.2, 134.0, 130.1, 129.9, 129.1, 128.9,
128.2, 128.0, 118.9.
Compound 4d
White solid, mp 64–66 ꢁC. nmax (KBr)=cmꢂ1: 3429, 3078, 2923, 1648,
1599, 1495. dH (CDCl3): 7.71 (d, J 15.6 Hz, 1H), 7.53 (m, 2H),
7.40–7.30 (m, 3H), 6.85 (d, J 15.6 Hz, 1H), 3.73–3.68 (m, 8H). 13C
NMR (CDCl3): 165.6, 143.2, 135.1, 129.8, 128.8, 127.7, 116.6, 66.9.

SmI3-Catalyzed Addition of Amines
827
m=z (%): 217 (Mþ, 28.73), 172 (11.27), 130 (100). Anal. calcd. for
C13H15NO2: C, 71.87; H, 6.96; N, 6.45. Found: C, 71.76; H, 7.03; N, 6.37.
Compound 4e
White solid, mp 81–83 ꢁC. nmax (KBr)=cmꢂ1: 3289, 3083, 2957, 2930,
2867, 1655, 1617, 1494. dH (CDCl3): 7.62 (d, J 15.6 Hz, 1H), 7.46–7.43
(m, 2H), 7.33–7.31 (m, 3H), 6.43 (d, J 15.6 Hz, 1H), 5.94 (br, s, 1H),
3.41–3.36 (m, 2H), 1.59–1.52 (m, 2H), 1.43–1.34 (m, 2H), 0.93 (t,
J 7.2 Hz, 3H). 13C NMR (CDCl3): 166.0, 140.7, 134.9, 129.5, 128.8,
127.7, 121.0, 39.5, 31.8, 20.1, 13.8. m=z (%): 203 (Mþ, 29.52), 188
(12.37), 131 (100). Anal. calcd. for C13H17NO: C, 76.81; H, 8.43; N,
6.89. Found: C, 76.95; H, 8.36; N, 6.95.
Compound 4f
White solid, mp 96–98 ꢁC. nmax (KBr)=cmꢂ1: 3293, 3085, 2930, 1657,
1617, 1513. dH (CDCl3): 7.59 (d, J 16.0 Hz, 1H), 7.37 (d, J 8.0 Hz, 2H),
7.13 (d, J 8.0 Hz, 2H), 6.40 (d, J 16.0 Hz, 1H), 3.40–3.35 (m, 2H), 2.34
(s, 3H), 1.59–1.51 (m, 2H), 1.43–1.33 (m, 2H), 0.93 (t, J 7.2 Hz, 3H).
13C NMR (CDCl3): 166.3, 140.6, 139.8, 132.2, 129.5, 127.7, 119.9, 39.5,
31.8, 21.4, 20.2, 13.8. m=z (%): 217 (Mþ, 23.53), 174 (14.65), 159
(42.92), 145 (100). Anal. calcd. for C14H19NO: C, 77.38; H, 8.81; N,
6.45. Found: C, 77.25; H, 8.90; N, 6.37.
Compound 4h
White solid, mp 120–122 ꢁC. nmax (KBr)=cmꢂ1: 3298, 3067, 2962, 2868,
1653, 1617, 1546. dH (CDCl3): 7.56 (d, J 15.6 Hz, 1H), 7.40 (d, J
8.0 Hz, 2H), 7.31 (d, J 8.0 Hz, 2H), 6.40 (d, J 15.6 Hz, 1H), 3.41–3.36
(m, 2H), 1.59–1.52 (m, 2H), 1.43–1.34 (m, 2H), 0.95–0.91 (t, J 7.2 Hz,
3H). 13C NMR (CDCl3): 165.7, 139.4, 135.4, 133.4, 129.0, 128.9, 121.5,
39.6, 31.7, 20.1, 13.8. m=z (%): 239 (Mþ, 8.3), 237 (Mþ, 22.6), 197
(8.7), 195 (22.4), 167 (33), 165 (100). Anal. calcd. for C13H16ClNO: C,
65.68; H, 6.78; N, 5.89. Found: C, 65.59; H, 6.82; N, 5.87.
Compound 4i
Colorless oil.[8] nmax (C2H5OH)=cmꢂ1: 3075, 2990, 1660, 1615, 1581.
dH (CDCl3): 7.64 (d, J 15.6 Hz, 1H), 7.44 (d, J 8.4 Hz, 2H), 7.32 (d,

828
X. Wang et al.
J 8.4 Hz, 2H), 6.80 (d, J 15.6 Hz, 1H), 3.49–3.43 (m, 4H), 1.27–1.16 (m,
6H). 13C NMR (CDCl3): 165.4, 140.8, 135.2, 133.9, 129.0, 128.9, 118.4,
42.3, 41.1, 15.1, 13.2.
Typical Procedure for the Formation of Bis-Addition Product 6
P-anisidine (0.068 g, 0.55 mmol) and b-amino-N-acylbenzotriazole 5
(0.147 g, 0.5 mmol), to a SmI3-CH2Cl2 suspension prepared as described
previously added were. The mixture was stirred at rt for 3 h, and dilute
hydrochloric acid (0.1 N, 5 mL) was then added. The organic layer was
separated, and the aqueous layer extracted with ethyl acetate
(10 mLꢀ3). The combined organic layer was washed by saturated
Na2CO3 and brine and dried over Na2SO4. The solvent was removed,
and the residue was purified by flash column chromatography (cyclohex-
ane–EtOAc 4:1) to afford 0.119 g of compound 6 (80% yield), white solid,
mp 116–118 ꢁC (lit.[3a] 117–119 ꢁC). dH (CDCl3): 7.62 (br, s, 1H, CONH),
7.36 (d, J 8.8 Hz, 2H), 7.06 (t, J 8.4 Hz, 1H), 6.84 (d, J 8.8 Hz, 2H), 6.58
(d, J 7.2 Hz, 1H), 6.46–6.48 (m, 2H), 3.76 (s, 3H, Me), 3.41 (dd, J 9.2,
10.2 Hz, 1H), 3.46 (dd, J 4.4, 9.6 Hz, 1H), 2.75–2.69 (m, 1H), 2.29 (s,
3H, Me), 1.29 (d, J 6.8 Hz, 3H). 13C NMR (CDCl3): d 173.1, 156.4,
147.4, 139.2, 130.9, 129.2, 121.8, 119.1, 114.2, 114.1, 110.5, 55.5, 47.7,
41.1, 21.5, 15.4.
ACKNOWLEDGMENTS
We are grateful to the Department of Science and Technology, Zhejiang
Province (Project No. 2006C11262), for financial support.
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