Novel C-C bond cleavage from arylacetonitriles in alcohols to aryl carboxylic esters using potassium iodide and catalytic amount of samarium

Article abstract of DOI:10.1080/00397910600770680

A novel way to cleave the carbon-carbon bond from arylacetonitriles in alcohols to their corresponding aryl carboxylic esters using potassium iodide and a catalytic amount of samarium under mild and neutral conditions is described. Useful yields of the reaction can be obtained with electron-deficient subsistent groups in aromatic rings, and the yields are higher when the subsistent group is an electron-withdrawing group (EWG) rather than an electron-donating group (EDG). Products were characterized by IR, ¹H NMR, ¹³C NMR, and MS. Copyright Taylor & Francis Group, LLC.

Full text of DOI:10.1080/00397910600770680

Synthetic Communicationsw, 36: 2851–2857, 2006
Copyright # Taylor & Francis Group, LLC
ISSN 0039-7911 print/1532-2432 online
DOI: 10.1080/00397910600770680
Novel C-C Bond Cleavage from
Arylacetonitriles in Alcohols to Aryl
Carboxylic Esters using Potassium Iodide
and Catalytic Amount of Samarium
Mingxin Yu, Weijiang Wen, and Zhiyuan Wang
Department of Chemistry, Zhejiang University, Hangzhou, China
Abstract: A novel way to cleave the carbon–carbon bond from arylacetonitriles
in alcohols to their corresponding aryl carboxylic esters using potassium iodide
and a catalytic amount of samarium under mild and neutral conditions is
described. Useful yields of the reaction can be obtained with electron-deficient
subsistent groups in aromatic rings, and the yields are higher when the
subsistent group is an electron-withdrawing group (EWG) rather than an
electron-donating group (EDG). Products were characterized by IR, 1H NMR,
13C NMR, and MS.
Keywords: Arylacetonitrile, aryl carboxylic ester, C-C bond cleavage, potassium
iodide, samarium
Since samarium diiodide was introduced into organic synthesis by Kagan,[1] it
caused a great public interest in organic synthesis using the samarium
reagent.[2–5] Now, many new reactions have been found to be relevant to
several samarium reagents such as samarium metal,[6,7] samarium/auxiliary
systems,[5] samarium diiodide[8–10] and triiodide.[11] In samarium/auxiliary
systems, there are many reactions promoted by Sm/cat.I2, Sm/Cp2TiCl2,
Sm/TiCl4, Sm/TMSCl, Sm/DMF, and so on. Our group has also reported
research on samarium/auxiliary systems.[4,5]
Esters are among the most widespread of naturally occurring
compounds. The ester linkage is also present in animal fats and other
Received in R.O.C. December 27, 2005
Address correspondence to Mingxin Yu, Department of Chemistry, Zhejiang
University, Hangzhou 310027, China. E-mail: mingxinyu@css.zju.edu.cn
2851

2852
M. Yu, W. Wen, and Z. Wang
biologically important molecules. Many approaches to synthesizing esters
have been reported, including direct and indirect methods.[12] More
recently, many new methods to prepare aryl carboxylic esters were
described, for example, (a) direct conversion of aldehydes in alcoholic
solvents to their corresponding ester products utilizing oxone or peroxova-
nadium as the oxidant;[13,14] (b) conversion of electron-deficient aryl alkyl
ketones to aryl esters in methanol;[15] (c) condensation reaction of car-
boxylic acids with alcohols to provide esters promoted by dimethylmalonyl-
trialkylphos phoranes.[16]
Herein we report a novel C-C bond cleavage from arylacetonitriles in
alcohols to their corresponding aryl carboxylic esters using potassium
iodide and a catalytic amount of samarium. Reaction steps are outlined in
Scheme 1. Yields of products are obtained using potassium iodide and a
catalytic amount of samarium (Table 1). Products were characterized by IR,
1H NMR, 13C NMR, and MS.
To the best of our knowledge, this is the first time aryl carboxylic esters
have been prepared in one pot directly from arylacetonitriles and
methanol using potassium iodide and a catalytic amount of samarium. The
Sm/KI system is easy to obtain and insensitive to air. The success of this
methodology was further demonstrated by carbon–carbon cleavage from 4-
nitrophenylacetonitrile with other alcohols such as 1-propanol, which gives
89% yield of the corresponding esters. Esters of more branched alcohols
such as 2-propanol and tert-butyl alcohol could be obtained with long
reaction times and in poor yields as reported in Table 1. The reaction rate
and yield of the major product have been affected by catalytic amounts of
samarium. Yield of the side product (4,40-azoxybisbenzoic acid dimethyl
ester) largely decreases, and the corresponding aryl carboxylic esters were
obtained in good to excellent yields. Unfortunately, 3-nitrophenylacetonitrile
and 4-methoxyphenylacetonitrile consistently give poor conversion and poor
yields of the corresponding esters.
In conclusion, we have demonstrated a simple and effective one-pot
protocol to transform arylacetonitriles to aryl carboxylic esters by novel
C-C bond cleavage in alcohols. The Sm/KI system is easy to obtain and
insensitive to air. It uses easily available reagents and creates fewer side
products in the reaction. The Sm/KI system would make a suitable
practical method.
Scheme 1. R1 ¼ H, p-C1, p-NO2, m-NO2, p-OCH3; R ¼ Methyl, Ethyl, Pr, i-Pr, t-Bu,
benzyl, cyclohexyl.

Novel C-C Bond Cleavage from Arylacetonitriles
2853
Table 1. Reaction conditions and yields of aryl carboxylic esters
Entry
R1
R
Temp (8C)
Time (h)
Yields (%)a
2a
2b
2c
2d
2e
2f
p-NO2
p-NO2
p-NO2
p-NO2
p-NO2
p-NO2
p-NO2
p-NO2
H
CH3
CH3
rt
rt
24
72
24
24
72
72
48
72
72
48
48
72
72
92
63b
90
89
76
5c
CH3CH2
CH3CH2CH2
i-Pr
rt
rt
50
50
rt
t-Bu
2g
2h
2i
PhCH2
Cyclohexyl
CH3
80
62
14c
74
60
2
rt
50
rt
2j
p-Cl
p-Cl
CH3
2k
2l
CH3CH2
CH3
CH3
rt
p-OCH3
m-NO2
rt
2m
rt
38
aIsolated yields based on arylacetonitrilles.
bNot added samarium.
cYields by GC-MS.
EXPERIMENTAL
Chemicals were purchased from Aldrich. Thin-layer chromatography
(TLC) on commercial plates of silica gel GF254 was used to monitor
the progress of the reactions. Yields refer to isolated products after puri-
fication. Melting points were determined on a Yanaco melting-point
apparatus and are uncorrected. Infrared (IR) spectra were taken on a
Nicolet 230 FT-IR spectrophotometer. 1H NMR and 13C NMR spectra
were recorded in CDCl3 on a Bruker Avance 500 DMX and 400 DMX
spectrometer using TMS as internal standard. Elemental analysis was
measured on a Eager 200. GC-MS spectrum was obtained from HP
6890, 5973.
Typical Procedure for Synthesis of Aryl Carboxylic Esters
Potassium iodide (0.19 g, 1.1 mmol) and alcohol (10 mL) were placed in a
three-necked, round-bottom flask with magnetic stirring bar. Then
samarium powder (0.015 g, 0.1 mmol) and arylacetonitrile (1 mmol) were
added. The reaction mixture was stirred for an appropriate time at room temp-
erature or with heat. After filtration and removal of solvents, the crude product
was obtained and purified by column chromatography on silica gel using
acetic ether/hexane as eluents.

2854
M. Yu, W. Wen, and Z. Wang
Data
4-Nitro-benzoic acid methyl ester (2a): Yield 92%; pale yellow solid; mp:
1
93–958C (lit.[17] 93–948C); H NMR (500, CDCl3) dH: 8.30 (d, J ¼ 9.0 Hz,
2 H), 8.22 (d, J ¼ 9.0 Hz, 2 H), 3.99 (s, 3 H); 13C NMR (500, CDCl3) dC:
165.44 (C), 150.82 (C), 135.75 (C), 130.97 (CH), 123.81 (CH), 53.09
(CH3); IRymax (KBr)/cm21: 3079, 2958, 1719, 1609, 1525, 1348, 1276,
1103, 822.
4-Nitro-benzoic acid ethyl ester (2c): Yield 90%; pale yellow solid; mp: 54–
568C (lit.[18] 55–578c); 1H NMR (500, CDCl3) dH: 8.29 (d, J ¼ 9.0 Hz, 2 H),
8.22 (d, J ¼ 9.0 Hz, 2 H), 4.44 (q, J ¼ 7.0 Hz, 2 H), 1.43 (t, J ¼ 7.0 Hz, 3 H);
IRymax (KBr)/cm21: 3119, 2990, 1717, 1607, 1526, 1351, 1281, 1104, 841.
4-Nitro-benzoic acid propyl ester (2d): Yield 89%; pale yellow solid; mp:
1
32–338C (lit.[19] 348C); H NMR (500, CDCl3) dH: 8.28 (d, J ¼ 9.0 Hz, 2
H), 8.22 (d, J ¼ 9.0 Hz, 2 H), 4.34 (t, J ¼ 7.0 Hz, 2 H), 1.81–1.85 (m, 2
H), 1.05 (t, J ¼ 7.5 Hz, 3 H); IRymax(KBr)/cm21: 3109, 2968, 1719, 1606,
1524, 1341, 1271, 1103, 874, 721.
4-Nitro-benzoic acid isopropyl ester (2e): Yield 76%; pale yellow solid; mp:
104–1058C (lit.[20] 104–1068C); 1H NMR (500, CDCl3) dH: 8.28
(d, J ¼ 9.0 Hz, 2 H), 8.20 (d, J ¼ 9.0 Hz, 2 H), 5.28–5.30 (m, 1 H), 1.40
(d, J ¼ 6.0 Hz, 6 H); IRymax(KBr)/cm21: 3116, 2923, 1713, 1607, 1523,
1347, 1282, 1100, 841.
4-Nitro-benzoic acid phenyl methyl ester (2 g): Yield 80%; pale yellow
solid; mp: 82–848C (lit.[21] 83–848C); 1H NMR (500, CDCl3) dH: 8.28
(d, J ¼ 9.0 Hz, 2 H), 8.24 (d, J ¼ 9.0 Hz, 2 H), 7.37–7.46 (m, 5 H), 5.41
(s, 2 H); IRymax(KBr)/cm21: 3114, 2943, 1713, 1603, 1522, 1341, 1275,
1121, 1101, 845.
4-Nitro-benzoic acid cyclohexyl ester (2 h): Yield 62%; pale yellow solid;
mp: 47–498C (lit.[22] 49–518C); 1H NMR (500, CDCl3) dH: 8.29
(d, J ¼ 9.0 Hz, 2 H), 8.22 (d, J ¼ 9.0 Hz, 2 H), 5.06–5.08 (m, 1 H), 1.97–
1.99 (m, 2 H), 1.80–1.83 (m, 2 H), 1.58–1.63 (m, 4 H), 1.46–1.49 (m, 2 H);
IRymax(film)/cm21: 3114, 2856, 1723, 1607, 1530, 1348, 1278, 1115, 842, 720.
Benzoic acid methyl ester (2i): Yield 14%; pale yellow oil; bp: 197–1998C
1
(lit.[23] 198–2008C.); H NMR (400, CDCl3) dH: 8.04 (d, J ¼ 8.0 Hz, 2 H),
7.55 (t, J ¼ 7.6 Hz, 1 H), 7.41–7.45 (m, 2 H), 3.91 (s, 3 H); IRymax(KBr)/
cm21: 3062, 2955, 1724, 1600, 1451, 1432, 1278, 1111, 823.
4-Chloro-benzoic acid methyl ester (2j): Yield 74%; pale yellow solid; mp:
38–398C (lit.[24] 398C); 1H NMR (500, CDCl3) dH: 7.98 (d, J ¼ 9.0 Hz, 2 H),

Novel C-C Bond Cleavage from Arylacetonitriles
2855
7.42 (d, J ¼ 9.0 Hz, 2 H), 3.92 (s, 3 H); IRymax(KBr)/cm21: 3043, 2960,
1727, 1597, 1495, 1435, 1277, 1092, 823.
4-Chloro-benzoic acid ethyl ester (2 k): Yield 60%; pale yellow solid; mp:
103–1058C (lit.[25] 103–1058c); 1H NMR (500, CDCl3) dH: 7.97
(d, J ¼ 9.0 Hz, 2 H), 7.40 (d, J ¼ 9.0 Hz, 2 H), 4.37 (q, J ¼ 7.0 Hz, 2 H),
1.39 (t, J ¼ 7.0 Hz, 3 H); IRymax(KBr)/cm21: 3059, 2985, 1721, 1595,
1490, 1403, 1274, 1092, 827, 760.
3-Nitro-benzoic acid methyl ester (2 m): Yield 38%; pale yellow solid; mp:
1
76–788C (lit.[26] 788C); H NMR (400, CDCl3) dH: 8.88 (s, 1 H), 8.37–8.44
(m, 2 H), 7.66 (t, J ¼ 8.0 Hz, 1 H), 3.99 (s, 3 H); IRymax(KBr)/cm21: 3093,
2960, 1719, 1615, 1529, 1442, 1351, 1292, 1136.
4,40-Azoxybisbenzoic acid dimethyl ester (side product): Yield 28%
(without added samarium); mp 201–2038C (lit.[27] 203–2058C),1H NMR
(500, CDCl3) dH: 8.08 (d, J ¼ 9.0 Hz, 2 H), 7.89 (d, J ¼ 8.5 Hz, 2 H), 7.46
(d, J ¼ 9.0 Hz, 2 H), 6.74 (d, J ¼ 8.5 Hz, 2 H), 4.02 (s, 3 H), 3.88 (s, 3 H);
13C NMR (500, CDCl3) dC: 166.82 (C), 157.28 (C), 151.99 (C), 148.51 (C),
136.73 (C), 131.04 (CH), 130.34 (CH), 125.18 (C), 123.36 (CH), 121.25
(CH), 54.75 (CH3), 52.10 (CH3); IRmax(KBr)/cm21: 3001, 2946, 1717,
1659, 1524, 1348, 1279, 1104, 861; MS(EI) m/z: 314 (Mþ).
ACKNOWLEDGMENT
We are grateful to the Natural Science Foundation of the Education Depart-
ment of Zhejiang Province, China (Project No. 20050918).
REFERENCES
1. Girard, P.; Namy, J. L.; Kangan, H. B. Divalent lanthanide derivatives in organic
synthesis, 1: Mild preparation of samarium iodide and ytterbium iodide and their
use as reducing or coupling agents. J. Am. Chem. Soc. 1980, 102, 2693–2698.
2. Molander, G. A. Application of lanthanide reagents in organic synthesis.
Chem. Rev. 1992, 92, 29–68.
3. Molander, G. A.; Harris, C. R. Sequencing reaction with samarium(II) iodide.
Chem. Rev. 1996, 96, 307–338.
4. Yu, M. X.; Zhang, Y. M.; Bao, W. L. Application of samarium reagents in organic
synthesis. Chin. J. Chem. 1999, 17, 4–15.
5. Liu, Y. J.; Zhang, Y. M. New progress in the application of samarium reagent to
organic synthesis. Chin. Actc. Chimica Sinica 2005, 63 (5), 341–351.
6. Concellon, J. M.; Rodriguez-Solla, H.; Llavona, R. Sequential elimination–
cyclo propanation reactions promoted by samarium: Highly diastereoselective
synthesis of cyclopropylamindes. J. Org. Chem. 2003, 68, 1132–1133.

2856
M. Yu, W. Wen, and Z. Wang
7. Talukdar, S.; Fang, J. M. Reduction and coupling reactions of carbonyl compounds
using samarium metal in aqueous media. J. Org. Chem. 2001, 66, 330–333.
8. Howells, D. M.; Barker, S. M.; Watson, F. C.; Light, M. E.; Hursthouse, M. B.;
Kilburn, J. D. Samarium diiodide coupling of enones: A remarkable cascade
sequence. Org. Lett. 2004, 6, 1943–1945.
9. Ricci, M.; Blakskjaer, P.; Skrydstrup, T. Selective side chain introduction onto
small peptide mediated by samarium diiodide: A potential route to peptide
libraries. J. Am. Chem. Soc. 2000, 122, 12413–12421.
10. Blakskjaer, P.; Hoj, B.; Riber, D.; Skrydstrup, T. SmI2 reduced thioesters as
synthons of unstable acyl radicals: Direct synthesis of potential protease inhibitors
via intermolecular radical addition. J. Am. Chem. Soc. 2003, 125, 4030–4031.
11. Concellon, J. M.; Huerta, M. Synthesis of (E)-alpha, beta-unsaturated ketones
with total or high diastereoselectivity by using samarium diiodide or triiodide.
Tetrahedron Lett. 2003, 44, 1931–1934.
12. Carey, F. A.; Sundberg, R. J. Advanced Organic Chemistry, Part B: Reactions and
Synthesis; Kluwer Academin/Plenum Publishers: New York, 2001; pp. 172–177.
13. Travis, B. R.; Sivakumer, M.; Hollist, G. O.; Borhan, B. Facile oxidation of
aldehydes to acids and esters with oxone. Org. Lett. 2003, 5 (7), 1031–1034.
14. Gopinath, R.; Barkakaty, B.; Talukdar, B.; Patel, B. K. Peroxovanadium-catalyzed
oxidative esterification of aldehydes. J. Org. Chem. 2003, 68, 2944–2947.
15. Zhang, N.; Vozzolo, J. Novel C-C bond cleavage under mild, neutral conditions:
Conversion of electron-deficient aryl alkyl ketones to aryl carboxylic esters.
J. Org. Chem. 2002, 67, 1703–1704.
16. McNulty, J.; Capretta, A.; Laritchev, V.; Dyck, J.; Robertson, A. J. Dimethylma-
lonyltrialkylphosphoranes: New general reagents for esterification reactions
allowing controlled inversion or retention of configuration on chiral alcohols.
J. Org. Chem. 2003, 68, 1597–1600.
17. Raber, D. J.; Gariano, P. Jr.; Brod, A. O. Esterification of carboxylic acids with
trialkyloxonium salts. J. Org. Chem. 1979, 44, 1149–1154.
18. Brook, M. A.; Chan, T. H. A simple procedure for the esterification of carboxylic
acids. Synthesis 1983, 3, 201–203.
19. Huang, H. M.; Zhu, S. X.; Qi, W. S.; Na, C. W. New method for the synthesis of
aromatic carboxylic esters. Jilin Daxue Ziran Kexue Xuebao 1987, 4, 71–75.
20. Barry, J.; Bram, G.; Decodts, G.; Loupy, A.; Orange, C.; Petit, A.; Sansoulet, J.
Solid–liquid phase-transfer catalysis without added solvent: A simple, efficient,
and inexpensive synthesis of aromatic carboxylic esters by alkylation of
potassium carboxylates. Synthesis 1985, 1, 40–45.
21. Shintou, T.; Kikuchi, W.; Mukaiyama, T. Efficient method for the preparation of
carboxylic acid alkyl esters or alkyl phenyl ethers by a new type of oxidation–
reduction condensation using 2,6-dimethyl-1,4-benzoquinone and alkoxydiphe-
nylphosphines. Bull. Chem. Soc. Japan 2003, 76, 1645–1667.
22. Fairfull-Smith, K. E.; Jenkins, I. D.; Loughlin, W. A. Novel polymer-supported
coupling/dehydrating reagents for use in organic synthesis. Org. Biomol. Chem.
2004, 2, 1979–1986.
23. Hajipour, A. R.; Mazloumi, G. H. An efficient and simple procedure for
preparation of esters and anhydrides from acid chlorides in the presence of 1,4-
diazabicyclo[2.2.2]octane (DABCO) under solvent-free conditions. Synth.
Commun. 2002, 32, 23–30.
24. Olah, G. A.; Narang, S. C.; Garcia-Luna, A. Synthetic methods and reactions:
Sulfuryl chloride fluoride–mediated esterification of carboxylic acids with
alcohols. Synthesis 1981, 10, 790–791.

Novel C-C Bond Cleavage from Arylacetonitriles
2857
25. Al-Aseer, M. A.; Allison, B. D.; Smith, S. G. Mechanism of the reaction of lithium
reagents with esters. J. Org. Chem. 1985, 50, 2715–2719.
26. Ramana, M. M. V.; Malik, S. S.; Parihar, J. A. Guanidinium nitrate: A novel
reagent for aryl nitrations. Tetrahedron Lett. 2004, 45, 8681–8683.
27. Waldrep, D.; Yager, B. J. Preparation of dimethyl 4,40-azoxydibenzoate: An
anomalous benzoin condensation reaction. Texas J. Sci. 1976, 27, 397–399.