Samarium-mediated mild and facile method for the synthesis of amides

Article abstract of DOI:10.1016/j.tetlet.2010.09.048

Samarium-mediated facile method for the formation of amide bonds by the reaction of acyl chlorides and amines is described. The reaction afforded high yields of the desired amides under mild and neutral conditions.

Full text of DOI:10.1016/j.tetlet.2010.09.048

Tetrahedron Letters 51 (2010) 6049–6051
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Samarium-mediated mild and facile method for the synthesis of amides
a
a
a
a,b,
⇑
Feng Shi , Jian Li , Chunju Li , Xueshun Jia
a
Department of Chemistry, Shanghai University, Shanghai 200444, China
Key Laboratory of Synthetic Chemistry of Natural Substances, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, 345 Lingling Road, Shanghai 200032, China
b
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 8 July 2010
Revised 9 September 2010
Accepted 14 September 2010
Available online 17 September 2010
Samarium-mediated facile method for the formation of amide bonds by the reaction of acyl chlorides and
amines is described. The reaction afforded high yields of the desired amides under mild and neutral
conditions.
Ó 2010 Elsevier Ltd. All rights reserved.
The amide bond is an important functional group in organic
chemistry. It plays a major role in the elaboration and composition
yields. Aromatic acyl chlorides with electron-withdrawing and elec-
tron-donating groups gave high yields of the amides (Table 1, entry
1–4, 8–11, 16–18). Aliphatic acyl chlorides also provided higher
yields of the amides than aromatic acyl chlorides. The reaction pro-
ceeded efficiently even with highlysterically hindered pivaloyl chlo-
ride in high yields of the amides at room temperature (Table 1, entry
6). Especially, the reaction of pivaloyl chloride with sterically hin-
1
of biological and chemical systems. Amides are traditionally synthe-
sized by the reaction of amines with activated carboxylic acid deriv-
2
atives. Alternative approaches on the synthesis of amides are the
3
4
Staudinger reaction, the Schmidt reaction, Beckmann rearrange-
5
6
7
8
ment, aminocarbonylation of haloarenes, alkenes and alkynes,
oxidative amidation of aldehydes, hydrative amide synthesis with
9
2
dered t-BuNH can also be performed smoothly to give the amide
1
0
11
alkynes , and the amidation of thio acids with azides. However,
most of methods require the presence of a base or an acid and gen-
erate larger amounts of by-products. Thus, the synthesis of amides
under neutral conditions and without the generation of by-products
in 96% yield (Table 1, entry 15). However, the same reaction was car-
ried out under the same reaction conditions using zinc or indium
1
4b
metal to give the amide in low yields. More importantly, the reac-
tion proceeded smoothly in air at room temperature and carbon–
carbon double bond, chloro, alkoxyl, ester, and nitro groups of the
substrates were not affected under the reaction conditions. There
was no need to activate samarium metal with pretreatment. The
commercially available samarium was active enough to accomplish
the reactions, and epimerization does not occur under the reaction
conditions (Table 1, entry 21). We have also investigated the possi-
bility that samarium could function catalytically. However, high
yields of amides can only be achieved at least using 2/3 equiv of
samarium. The control experiments were conducted by the reaction
of aniline with benzoyl chloride using 1/3 equiv of samarium, or
without samarium to give the corresponding product in 69% and
trace yields, respectively.
1
2
is a challenging goal.
The synthesis of amides with acyl chlorides is generally con-
ducted in the presence of tertiary amines, but the use of tertiary
amines produces serious problem in the synthesis of peptide, such
1
3
as epimerization or premature deblocking of protecting groups.
However, these problems can be solved easily by using a metal
instead of tertiary amines.14 The chemistry of samarium metal in
organic synthesis has recently received increasing attention owing
to its stability in water and air.15 Our interests in utilizing samarium
metal in organic synthesis have led us to investigate samarium-pro-
moted reactions for the synthesis of amides.16 As a continuation of
our interest in samarium metal chemistry, herein we wish to report
a mild and convenient methodology for the formation of amide
bonds from amines and acid chlorides by using metallic samarium
as a promoter under neutral conditions (Scheme 1).
Treatment of aniline with benzoyl chloride in the presence of
samarium metal at room temperature resulted in the formation of
the corresponding amide in 93% yield (Table 1, entry 1). The reactiv-
ity of acyl chlorides under the present conditions was examined and
the results are summarized in Table 1. As can be seen from Table 1,
The acyl chloride reacted smoothly with aliphatic primary and sec-
ondary amines or aromatic amines to afford the amides in excellent
In conclusion, we have developed a simple and facile method
for the formation of amide bonds by using samarium metal as a
promoter under mild and neutral reaction conditions.17 The advan-
tages of the present method include high yields of products, simple
experimental procedure, avoiding poisonous solvent, no need for
dry solvent and no activation or pretreatment of samarium metal,
O
O
R1 NH2
Sm
NHR1
+
R2
R2
Cl
CH CN, rt
3
1
⇑
Corresponding author. Tel./fax: +86 21 66132408.
E-mail address: xsjia@mail.shu.edu.cn (X. Jia).
Scheme 1. The synthesis of various amides.
0
040-4039/$ - see front matter Ó 2010 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tetlet.2010.09.048

6
050
F. Shi et al. / Tetrahedron Letters 51 (2010) 6049–6051
Table 1
9. (a) Naota, T.; Murahashi, S. I. Synlett 1991, 693; (b) Tillack, A.; Rudloff, I.; Beller,
M. Eur. J. Org. Chem. 2001, 523; (c) Chang, J. W. W.; Chan, P. W. H. Angew. Chem.,
Int. Ed. 2008, 47, 1138; (d) Yoo, W. J.; Li, C. J. J. Am. Chem. Soc. 2006, 128, 13064.
Synthesis of amides from acyl chlorides and amines by using samarium metal at room
temperaturea
1
0. Cho, S.; Yoo, E.; Bae, I.; Chang, S. J. Am. Chem. Soc. 2005, 127, 16046.
11. (a) Zhang, X.; Li, F.; Lu, X. W.; Liu, C. F. Bioconjugate Chem. 2009, 20, 197; (b)
Kolakowski, R. V.; Shangguan, N.; Sauers, R. R.; Williams, L. J. J. Am. Chem. Soc.
Entry Amine
Acyl chloride
Time
h)
Yieldb
(%)
(
2
006, 128, 5695.
1
2
3
PhNH
PhNH
PhNH
2
2
2
PhCOCl
2
2
3
93 (1a)
95 (1b)
90 (1c)
1
1
2. Gunanathan, C.; Ben-David, Y.; Milstein, D. Science 2007, 317, 790.
3. (a) Scribner, R. M. Tetrahedron Lett. 1976, 17, 3853; (b) Bodanszky, M.; Conklin,
L. J. Chem. Soc., Chem. Commun. 1967, 773; (c) Zimmerman, J. E.; Anderson, G.
W. J. Am. Chem. Soc. 1967, 89, 7151; (d) Haver, A. C.; Smith, D. D. Tetrahedron
Lett. 1993, 34, 2239; (e) Miyazawa, T.; Otomatsu, T.; Yamada, T.; Kuwata, S.
Tetrahedron Lett. 1984, 25, 771; (f) Gamet, J. P.; Jacquier, R.; Verducci, J.
Tetrahedron 1984, 40, 1995; (g) Arendt, A.; Kolodziejczyk, A. M.; Sokolowska, T.
Tetrahedron Lett. 1978, 19, 2711; (h) Chen, F. M. S.; Stainauer, R.; Benoiton, N. L.
J. Org. Chem. 1983, 48, 2939; (i) Bodanszky, M.; Bodanszky, A. J. Chem. Soc.,
Chem. Commun. 1967, 591.
p-ClC
p-
6
H
4
COCl
MeOC
6
H
4
COCl
COCl
4
5
6
7
8
9
PhNH
PhNH
PhNH
PhNH
2
2
2
2
p-MeC
6
H
4
2
3
2
2
4
4
92 (1d)
99 (1e)
97 (1f)
97 (1g)
95 (1h)
92 (1i)
PhCH
t-BuCOCl
CH (CH
2
COCl
3
2
6
) COCl
p-MeOC
p-MeOC
6
H
H
4
NH
NH
2
2
p-ClC
p-
H COCl
6 4
6
4
MeOC
p-
MeOC
p-
6
6
6
H
H
H
4
COCl
COCl
COCl
14. (a) Meshram, H. M.; Reddy, G. S.; Reddy, M. M.; Yadav, J. S. Tetrahedron Lett.
1998, 39, 4103; (b) Cho, D. H.; Jang, D. O. Tetrahedron Lett. 2004, 45, 2285.
15. (a) Ghatak, A.; Becler, F. F.; Banik, B. K. Tetrahedron Lett. 2000, 41, 3793; (b) Liu,
Y.; Xu, X.; Zhang, Y. Tetrahedron 2004, 60, 4867; For review, see: (c) Banik, B. K.
Eur. J. Org. Chem. 2002, 2431.
6. (a) Jia, X.; Liu, X.; Li, J.; Zhao, P.; Zhang, Y. Tetrahedron Lett. 2007, 48, 971; (b) Li,
S.; Li, J.; Jia, X. Synlett 2007, 1115; (c) Bian, H.; Li, J.; Li, C.; Wang, G.; Duan, Z.;
Jia, X. Synlett 2010, 1412.
1
0
1
p-ClC
6
H
4
NH
2
4
3
91 (1j)
89 (1k)
4
4
1
p-MeC
6
H
NH
4 2
MeOC
1
1
1
2
3
t-BuNH
t-BuNH
2
2
PhCOCl
p-ClC
3
3
85 (1l)
87
6
H
4
COCl
(1m)
1
7. General procedure for the homocoupling of terminal alkynes: To
a stirred
1
4
t-BuNH
t-BuNH
c-Hexylamine
c-Hexylamine
c-Hexylamine
Morpholine
Morpholine
(S)-Ethyl 2-amino-3-
phenylpropanoate
2
2
p-O
2
N
2
92 (1n)
suspension of samarium powder (4 mmol) in CH CN (10 mL) were added
3
6 4
C H COCl
t-BuCOCl
PhCOCl
6 4
p-MeC H COCl
PhCH@CHCOCl
PhCOCl
t-BuCOCl
PhCOCl
acid chloride (6 mmol) and amine (6 mmol) successively at room temperature.
The reaction mixture was stirred at room temperature for given time (Table 1).
The progress of the reaction was monitored by TLC. After completion of the
reaction, the mixture was filtered and the solid was washed with
dichloromethane. The solvent was removed under reduced pressure. The
residue was purified by column chromatography on silica gel eluting with
petroleum ether/ethyl acetate (5:1) to afford the corresponding amides 1 in
excellent yields. All the compounds were reported in the literatures and were
identified by melting points, IR, 1H NMR, and C NMR spectra.
15
16
17
18
19
20
21
2
3
2
2
4
3
2
96 (1o)
94 (1p)
92 (1q)
96 (1r)
82 (1s)
85 (1t)
83 (1u)
13
1
8
1
Compound 1a: mp 162.7–163.2 °C (lit. 163 °C); H NMR (300 MHz, CDCl
3
) d:
7.89 (s, 1H), 7.86 (d, J = 9.0 Hz, 2H), 7.66–7.15 (m, 8H); C NMR (75.4 MHz,
CDCl ) d: 165.9, 137.6, 135.1, 131.7, 129.3, 129.1, 128.5, 126.9, 124.7, 120.0,
118.4, 114.9; IR (KBr)
Compound 1b: mp 200.8–201.1 °C (lit. 199.5–200 °C); 1H NMR (300 MHz,
CDCl ) d: 7.94 (s, 1H), 7.85 (d, J = 9.0 Hz, 2H), 7.66–7.12 (m, 7H); IR (KBr)
351, 1654, 1598 cm
Compound 1c: mp.173.4–174.1 °C (lit.20 170–171 °C); 1H NMR (300 MHz,
a
13
Reaction conditions: samarium (4 mmol), acid chloride (6 mmol), amine
6 mmol).
(
3
ꢀ
1
b
m: 3344, 1656, 1599 cm .
19
Isolated yields.
3
m:
ꢀ
1
3
.
the applicability of a wider range of substrates and the neutral con-
ditions. The procedure will also provide alternative opportunities
for the preparation of the amides.
CDCl
3
) d: 7.85 (d, J = 12.0 Hz, 2H), 7.82 (s, 1H), 7.64–6.95 (m, 7H), 3.88 (s,
ꢀ
1
1
3H); IR (KBr)
m
: 3338, 2959, 1656, 1599 cm
.
21
Compound 1d: mp 141–142 °C (lit. 145 °C). H NMR (300 MHz, CDCl
3
) d: 7.89
(
1
s, 1H), 7.78–7.14 (m, 9H), 2.42 (s, 3H); IR (KBr)
597 cm .
m
:
3340, 2958, 1657,
ꢀ
1
Acknowledgments
Compound 1e: mp 118.5-119.3 °C (lit.22 117–118 °C); 1H NMR (300 MHz,
CDCl
1601 cm
Compound 1f: mp 132–133 °C (lit. 132 °C); H NMR (300 MHz, CDCl
3
) d: 7.89 (s, 1H), 7.43–7.07 (m, 10H), 3.73 (s, 2H); IR (KBr) m: 3285, 1658,
ꢀ
1
The authors thank the National Natural Science Foundation of
China (Nos: 20872087 and 20902057), the Key Laboratory of
Synthetic Chemistry of Natural Substances, Chinese Academy of
Sciences and the Innovation Fund of Shanghai University for finan-
cial support.
.
23
1
3
) d: 7.46
m, 2H), 7.23 (m, 3H), 7.05 (m, 1H), 1.28(s, 9H); C NMR (75.4 MHz, CDCl ) d:
: 3314, 2986, 2963, 2931,
13
(
3
1
76.5, 138.1, 128.9, 124.1, 120.2, 39.5, 27.6; IR (KBr) m
ꢀ
1
1654, 1596 cm
.
Compound 1g: mp 50–52 °C (lit. 48–51 °C); 1H NMR (500 MHz, CDCl
24
) d: 8.03
br s, 1H), 7.53 (d, J = 8.0 Hz, 2H), 7.26 (d, J = 15.5 Hz, 2H), 7.06 (t, J = 7.0 Hz,
3
(
1
H), 2.31 (t, J = 15.0 Hz, 2H), 1.71–1.66 (m, 2H), 1.34–1.21 (m, 8H), 0.87 (t,
References and notes
J = 7.0 Hz, 3H); 13C NMR (125 MHz, CDCl ) d: 172.2, 138.2, 128.9, 124.2, 120.2,
3
3
7.8, 31.8, 29.3, 29.1, 25.8, 22.7, 14.1; IR (KBr) m: 3313, 2925, 2850, 1656,
ꢀ
1
1
.
(a) Bode, J. W. Curr. Opin. Drug Disco. Devel. 2006, 9, 765; (b) Humphrey, J. M.;
Chamberlin, A. R. Chem. Rev. 1997, 97, 2243; (c) Cupido, T.; Tulla-Puche, J.;
Spengler, J.; Albericio, F. Curr. Opin. Drug Discov. Devel. 2007, 10, 768.
(a) Larock, R. C. In Comprehensive Organic Transformations; VCH: New York,
1600 cm .
Compound 1h: mp 207.3–207.9 °C (lit. 209.3–210 °C); 1H NMR (300 MHz,
25
CDCl
3
) d: 7.81 (d, J = 12.0 Hz, 2H), 7.67 (s, 1H), 7.54–7.45 (m, 4H), 6.93 (d,
ꢀ
1
2
.
J = 9.0 Hz, 2H), 3.82 (s, 3H); IR (KBr)
Compound 1i: mp 201–202 °C (lit. 200–203 °C); H NMR (300 MHz, CDCl
m
: 3346, 2957, 1648, 1599 cm .
26
1
1
999; (b) Valeur, E.; Bradley, M. Chem. Soc. Rev. 2009, 38, 606; (c) Han, S. Y.;
3
) d:
Kim, Y. A. Tetrahedron 2004, 60, 2447; (d) Montalbetti, C. A. G. N.; Falque, V.
Tetrahedron 2005, 61, 10827.
(a) Pianowski, Z.; Gorska, K.; Oswald, L.; Merten, C. A.; Winssinger, N. J. Am.
Chem. Soc. 2009, 131, 6492; (b) Saxon, E.; Bertozzi, C. R. Science 2000, 287, 2007;
7.84 (d, J = 12.0 Hz, 2H), 7.65 (s, 1H), 7.53 (d, J = 12.0 Hz, 2H), 7.0–6.89 (m, 4H),
ꢀ
1
3.88 (s, 1H), 3.83 (s, 1H); IR (KBr)
Compound 1j: mp 205–206 °C (lit. 206.2–208.5 °C);
CDCl ) d: 7.80 (d, J = 9.0 Hz, 2H), 7.65 (s, 1H), 7.54–7.44 (m, 4H), 6.91 (d,
J = 9.0 Hz, 2H), 3.82 (s, 3H); IR (KBr)
Compound 1k: mp 153.1–153.8 °C (lit. 156–157 °C). H NMR (300 MHz,
CDCl ) d: 7.88 (s, 1H), 7.81 (d, J = 9.0 Hz, 2H), 7.50 (d, J = 12.0 Hz, 2H), 7.13 (d,
J = 9.0 Hz, 2H), 6.92 (d, J = 9.0 Hz, 2H), 3.82 (s, 2H), 2.32 (s, 3H); IR (KBr) : 3340,
m: 3327, 2955, 1647, 1605 cm .
2
5
1
3
.
.
H NMR (300 MHz,
3
ꢀ
1
(
c) Damkaci, F.; Deshong, P. J. Am. Chem. Soc. 2003, 125, 4408; (d) Gololobov, Y.
m: 3355, 2969, 1655, 1606 cm .
27 1
G.; Kasukhin, L. F. Tetrahedron 1992, 48, 1353.
4
(a) Lang, S.; Murphy, J. A. Chem. Soc. Rev. 2006, 35, 146; (b) Ribelin, T.; Katz, C.
E.; English, D. G.; Smith, S.; Manukyan, A. K.; Day, V. W.; Neuenswander, B.;
Poutsma, J. L.; Aube, J. Angew. Chem., Int. Ed. 2008, 47, 6233.
3
m
ꢀ
1
2962, 1652, 1601 cm
.
28
1
5
.
.
(a) Hashimoto, M.; Obora, Y.; Sakaguchi, S.; Ishii, Y. J. Org. Chem. 2008, 73, 2894;
Compound 1l: mp 134–135 °C (lit. 134–135 °C); H NMR (300 MHz, CDCl
3
) d:
7.70 (d, J = 9.0 Hz, 2H), 7.44–7.39 (m, 3H), 5.96 (s, 1H), 1.46 (s, 9H); C NMR
1
3
(
b) Owston, N. A.; Parker, A. J.; Williams, J. M. J. Org. Lett. 2007, 9, 3599.
6
(a) Nanayakkara, P.; Alper, H. Chem. Commun. 2003, 2384; (b) Martinelli, J. R.;
Clark, T. P.; Watson, D. A.; Munday, R. H.; Buchwald, S. L. Angew. Chem., Int. Ed.
(75.4 MHz, CDCl
3326, 2979, 1636, 1579 cm
Compound 1m: mp 136–137 °C (lit. 137–138 °C); 1H NMR (300 MHz, CDCl
d: 7.81 (d, J = 9.0 Hz, 2H), 7.54–7.44 (m, 2H), 6.0 (s, 1H), 1.47 (s,9H); IR (KBr) m
3
) d: 166.8, 136.0, 131.2, 128.3, 126.7, 51.7, 28.8; IR (KBr)
m
:
ꢀ
1
.
29
2
007, 46, 8460.
Beller, M.; Cornils, B.; Frohning, C. D.; Kohlpaintner, C. W. J. Mol. Catal. A: Chem.
995, 104, 17.
3
)
:
7
.
.
ꢀ
1
1
3357, 2979, 1636, 1592 cm
Compound 1n: mp 158–159 °C (lit. 159–160 °C); 1H NMR (300 MHz, CDCl
8.24 (d, J = 9.0 Hz, 2H), 7.87 (d, J = 9.0 Hz, 2H), 6.09 (s, 1H), 1.49 (s, 9H); IR (KBr)
.
29
8
(a) Park, J. H.; Kim, S. Y.; Kim, S. M.; Chung, Y. K. Org. Lett. 2007, 9, 2465; (b)
Uenoyama, Y.; Fukuyama, T.; Nobuta, O.; Matsubara, H.; Ryu, I. Angew. Chem.,
Int. Ed. 2005, 44, 1075; (c) Ali, B. E.; Tijani, J. Appl. Organomet. Chem. 2003, 17,
3
) d:
ꢀ
1
m
: 3308, 2969, 1638, 1600 cm .
30
Compound 1o: mp 117–118 (lit. 118–118.7 °C); 1H NMR (300 MHz, CDCl
) d:
3
9
21; (d) Knapton, D. J.; Meyer, T. Y. Org. Lett. 2004, 6, 687.

F. Shi et al. / Tetrahedron Letters 51 (2010) 6049–6051
6051
5
4
.30(s, 1H), 1.26 (s, 9H), 1.12 (s, 9H); 13C NMR (75.4 MHz, CDCl
3
) d: 178.9, 52.3,
131.9, 129.6, 128.8, 128.7, 127.3, 127.1, 61.8, 53.7, 38.1, 14.3; IR (KBr)
m
: 3363,
ꢀ
1
ꢀ1
0.2, 30.1, 28.9; IR (KBr)
m
: 3376, 2967, 2931, 1638 cm
.
3069, 2960, 2932, 1749, 1641, 1602 cm
.
3
1
1
Compound 1p: mp 147–148 °C (lit. 148–149 °C); H NMR (300 MHz, CDCl
7
1
3
) d:
18. Furukawa, M.; Hokama, N.; Okawara, T. Synthesis 1983, 42.
19. Pratt, E. F.; Lasky, J. J. Am. Chem. Soc. 1956, 78, 4310.
20. Walia, J. S.; Guillot, L.; Singh, J.; Chattha, M. S.; Satyanarayana, M. J. Org. Chem.
1972, 37, 135.
.76 (d, J = 12.0 Hz, 2H), 7.46 (m, 3H), 5.97 (s, J = 12.0 Hz, 1H), 4.02–3.98 (m,
ꢀ
1
H), 2.07–1.20 (m, 10H); IR (KBr)
m
: 3308, 2935, 1628, 1577 cm
.
3
2
1
Compound 1q: mp 150–151 °C (lit. 152–153 °C); H NMR (300 MHz, CDCl
3
) d:
7
3
1
.65 (d, J = 12.0 Hz, 2H), 7.23 (d, J = 12.0 Hz, 2H), 6.05 (d, J = 9.0 Hz, 1H), 3.98–
.95 (m, 1H), 3.38 (s, 3H), 2.04–1.16 (m, 10H); IR (KBr) : 3324, 2973, 2937,
21. Abramovitch, R. A.; Azogu, C. I.; Mcmaster, L. T.; Vanderpool, D. P. J. Org. Chem.
1978, 43, 1218.
22. Meyer, R. B.; Hauser, C. R. J. Org. Chem. 1961, 26, 3183.
23. Degnan, W. M.; Shoemaker, C. J. J. Am. Chem. Soc. 1946, 68, 104.
24. Yokozawa, T.; Asai, T.; Sugi, R.; Ishigooka, S.; Hiraoka, S. J. Am. Chem. Soc. 2000,
122, 8313.
m
ꢀ
1
627, 1573 cm
.
Compound 1r: mp 176–177 °C (lit. 179.2–180.2 °C); 1H NMR (300 MHz,
3
3
CDCl
3
) d: 7.61 (d, J = 18.0 Hz, 1H), 7.51–7.48 (m, 2H), 7.36–7.33 (m, 3H), 6.38
: 3277,
(
d, J = 18.0 Hz, 1H), 3.93–3.90 (m, 1H), 2.02–1.13 (m, 10H); IR (KBr)
m
ꢀ
1
2
916, 1654, 1618, 1496 cm
.
25. Su, W. K.; Zhang, Y.; Li, J. J.; Li, P. Org. Prep. Proced. Int. 2008, 40, 543.
26. Conley, R. T. J. Org. Chem. 1958, 23, 1330.
Compound 1s: mp 74–75 °C (lit. 73–74 °C); 1H NMR (300 MHz, CDCl
3
4
) d: 7.46
) d: 170.2, 135.1, 129.6,
3
1
3
(
m, 5H), 3.77–3.45 (m, 8H); C NMR (75.4 MHz, CDCl
28.6, 127.0, 66.7, 43.2; IR (KBr) : 2855, 1628, 1579 cm
Compound 1t: mp 72.1–72.8 °C (lit. 73 °C); H NMR (300 MHz, CDCl
3
27. Kageyama, H.; Tani, K.; Kato, S.; Kanda, T. Heteroat. Chem. 2001, 12, 250.
28. Campbell, K. N.; Sommers, A. H.; Campbell, B. K. J. Am. Chem. Soc. 1946, 68, 140.
29. Uchida, Y.; Kobayashi, Y.; Kozuka, S. Bull. Chem. Soc. Jpn. 1981, 54, 1781.
30. Hayon, E.; Ibata, T.; Lichtin, N. N.; Simic, M. J. Am. Chem. Soc. 1971, 93, 5388.
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ꢀ
1
1
m
.
2
3
1
3
) d: 3.50
(
m, 8H), 1.12 (s, 9H); 13C NMR (75.4 MHz, CDCl
3
) d: 177.6, 68.1, 47.3, 40.7, 29.5;
ꢀ
1
IR (KBr) m: 2966, 2855, 1615, 1419 cm .
35
20
Compound 1u: mp 104–105 °C (lit. 100–102 °C); ½
a
ꢁ
D
3
+0.20° (c 0.56, CHCl );
1
H NMR (500 MHz, CDCl
3
) d: 7.51 (d, J = 2.0 Hz, 2H), 7.50–7.14 (m, 8H), 6.61 (d,
J = 7.0 Hz, 1H), 5.09–5.05 (m, 1H), 4.21 (q, J = 7.0 Hz, 2H), 3.31–3.22 (m, 2H),
1
3
1
3
.28 (t, J = 7.0 Hz, 3H); C NMR (125 MHz, CDCl ) d: 171.8, 166.9, 136.0, 134.1,