Azido-Schmidt reaction for the formation of amides, imides and lactams from ketones in the presence of FeCl3

Article abstract of DOI:10.1016/j.tetlet.2008.05.113

Ketones undergo smooth rearrangement with TMSN₃ in the presence of FeCl₃ under extremely mild conditions to provide the corresponding amides, imides and lactams in good yields with high selectivity. This method is very useful for the preparation of a wide range of amides, imides and lactams from ketones. The use of FeCl₃ makes this method simple, convenient and cost-effective.

Full text of DOI:10.1016/j.tetlet.2008.05.113

Tetrahedron Letters 49 (2008) 4742–4745
Contents lists available at ScienceDirect
Tetrahedron Letters
journal homepage: www.elsevier.com/locate/tetlet
Azido-Schmidt reaction for the formation of amides, imides and lactams
from ketones in the presence of FeCl3
*
J. S. Yadav , B. V. Subba Reddy, U. V. Subba Reddy, K. Praneeth
Division of Organic Chemistry, Indian Institute of Chemical Technology, Hyderabad 500 007, India
a r t i c l e i n f o
a b s t r a c t
Article history:
Ketones undergo smooth rearrangement with TMSN3 in the presence of FeCl3 under extremely mild con-
ditions to provide the corresponding amides, imides and lactams in good yields with high selectivity. This
method is very useful for the preparation of a wide range of amides, imides and lactams from ketones.
Received 21 April 2008
Revised 22 May 2008
Accepted 25 May 2008
Available online 13 June 2008
3
The use of FeCl makes this method simple, convenient and cost-effective.
Ó 2008 Elsevier Ltd. All rights reserved.
Keywords:
Schmidt reaction
Ketones
Sodium azide
Amides
Imides and lactams
The amide bond is one of the most important linkages in pep-
tide chemistry. Although the majority of amide bonds are formed
by condensation of an amine and a carboxylic acid, alternative
In this Letter, we disclose a versatile and convenient approach
for the preparation of amides, imides and lactams from ketones
by means of the azido-Schmidt reaction. Whilst working on the
nucleophilic addition reactions of carbonyl compounds with
1
approaches to amide synthesis are of continuing interest. The
Schmidt reaction is a valuable transformation for the synthesis of
amides and lactams from aldehydes and ketones. It accomplishes
TMSN
mation of amides. This provided incentive for an extensive study.
Initially, we examined the reaction of cyclohexanone with TMSN
in the presence of a stoichiometric amount of FeCl . The reaction
proceeded rapidly in dichloroethane at 23 °C and the product, cap-
rolactam 3a was isolated in 82% yield (Scheme 1).
3 3
in the presence of FeCl , surprisingly, we observed the for-
2
both the cleavage of a carbon–carbon bond and the formation of a
carbon–nitrogen bond. It represents a powerful method particu-
larly for manufacturing amides and lactams in the chemical indus-
3
3
3
try. However, the classical Schmidt reaction requires strong protic
acids, such as concentrated sulfuric acid and trichloroacetic acid,
which result in a large number of byproducts and serious corrosion
problems. Furthermore, in situ generated hydrazoic acid is unsta-
Encouraged by this result, we turned our attention to various
cyclic ketones such as cycloheptanone, 1,4-cyclohexanedione, cyclo-
dodecanone, 1-tetralone, 2-phenylchroman-4-one and 2-tetralone.
These cyclic ketones were converted successfully into their corre-
sponding lactams by using this procedure (Table 1, entries b–g).
4
ble and also explodes at high temperature. Since the classical
Schmidt reaction was effected in strongly acidic media, this pre-
cludes its application to acid-sensitive substrates. Although the
Schmidt reaction utilizes hydrazoic acid as a nitrogen source, it is
Next, we examined the reactivity of a-ketoamides and a 1,2,3-
triketone. Interestingly, isatin and 5-methylisatin underwent facile
ring expansion under these conditions (Table 1, entries h and i).
Ninhydrin also participated in this reaction (Table 1, entry j).
Interestingly, acyclic ketones such as acetophenone, propiophenone,
4-hydroxyacetophenone, 4-iodoacetophenone and benzophenone
5
–7
now known that alkyl azides can be used in Schmidt chemistry.
Trimethylsilyl azide has been used as a safe and convenient azide
8
source for various organic transformations.
In recent years, iron(III) chloride has emerged as a powerful
Lewis acid catalyst and performs many useful organic transforma-
tions under mild reaction conditions.9 Moreover, iron salts are
inexpensive, easy to handle and are environmentally friendly.
O
O
However, there have been no reports on the use of the FeCl
TMSN system for the Schmidt reaction.
3
/
FeCl (1.0 eq)
3
NH
TMSN
3
3
+
ClCH CH Cl, r.t, 38 min.
2
2
1
2
3a
*
Corresponding author. Tel.: +91 40 27193535; fax: +91 40 27160512.
E-mail address: yadavpub@iict.res.in (J. S. Yadav).
Scheme 1.
0
040-4039/$ - see front matter Ó 2008 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tetlet.2008.05.113

J. S. Yadav et al. / Tetrahedron Letters 49 (2008) 4742–4745
4743
Table 1
3 3
FeCl -mediated Schmidt reaction of various ketones with TMSN /NaN
3
Entry
Substrate
Producta
FeCl
3
/TMSN
3
3 3
FeCl /NaN
Time (min)
38
Yieldb (%)
82
Time (h)
3.0
Yieldb (%)
O
O
a
NH
70
72
O
H
N
O
b
45
55
80
68
3.0
3.5
O
O
O
NH
c
68
O
O
O
d
e
65
40
81
80
4.0
2.5
65
75
NH
O
H
N
O
O
O
O
O
H
N
f
50
46
30
35
40
75
70
80
75
82
3.0
2.5
2.5
2.5
3.0
68
67
74
75
72
Ph
Ph
O
O
g
h
i
NH
O
O
NH
O
N
H
N
H
O
O
O
H C
H C
3
3
NH
O
N
N
O
H
H
O
O
O
NH
j
O
O
O
H
O
N
k
l
30
35
33
85
78
72
2.0
2.0
2.5
76
70
66
Ph
Ph
O
H
N
O
Ph
Ph
O
O
H
N
m
O
HO
HO
O
H
N
n
35
32
76
79
3.0
2.5
68
70
O
I
I
H
O
N
Ph
o
P
Ph
Ph
Ph Ph
O
O
O
H
N
45
49
81
78
3.5
3.5
73
70
Ph
O
H
N
q
O
MeO
MeO
a
All products were characterized by NMR, IR and mass spectrometry.
Yield refers to pure products after chromatography.
b

4
744
J. S. Yadav et al. / Tetrahedron Letters 49 (2008) 4742–4745
Table 2
O
O
The effects of various Lewis acid catalysts on the preparation of 3a
FeCl (1.0 eq)
3
R'
+
TMSN
3
R
N
H
R'
R
ClCH CH Cl, r.t.
O
2
2
O
1
(k-o)
2
3
(k-o)
catalyst
NH
+
TMSN3
Scheme 2.
ClCH CH Cl, r.t.
2
2
1
2
3a
Entry
Catalyst (equiv)
Time (h)
Yielda (%)
underwent a smooth rearrangement to furnish the corresponding
secondary amides in good yields (Scheme 2, Table 1, entries k–o).
Similarly, aryl cyclopropyl ketones such as phenyl cyclopropyl
ketone and p-methoxyphenyl cyclopropyl ketone also gave the
respective anilides (Table 1, entries p and q). The products were
characterized by H and C NMR, IR and mass spectrometry. As
solvent, 1,2-dichloroethane gave the best results. It is noteworthy
to mention that the reaction also proceeded smoothly with sodium
1
2
3
4
5
6
7
8
9
FeCl
FeCl
InBr
3
3
3
(1.0)
(0.1)
(0.5)
(0.5)
(0.5)
(0.5)
0.5
12
3
3
5
12
12
12
12
12
12
12
12
12
14
14
14
82
78
40
30
InCl
ZrCl
YbCl
3
4
15
1
13
3
No reaction
No reaction
No reaction
No reaction
No reaction
No reaction
No reaction
No reaction
No reaction
No reaction
No reaction
No reaction
Bi(OTf)
In(OTf)
3
(0.5)
(0.5)
3
Sm(OTf)
Yb(OTf)
3
3
(0.5)
(0.5)
3
azide instead of TMSN albeit with longer reaction times and the
10
results are presented in Table 1. The azido-Schmidt reaction
involves the addition of azide to the ketone followed by rearrange-
ment and ring expansion. Similar to the classical Schmidt reaction,
the mechanism would involve simple Lewis acid activation of the
carbonyl group followed by the addition of azide. The resulting
iminodiazonium ions, which by loss of nitrogen and migration of
the anti-substituent, either an alkyl or aryl group, to the elec-
11
12
Sc(OTf)3 (0.5)
CuI (1.0)
13
14
15
16
YCI
3
(0.5)
I
2
(2.0)
IBX (0.5)
CAN (2.0)
Oxone (1.5)
17
a
Yield refers to pure products after chromatography.
10,11
tron-deficient nitrogen gives the amide (Scheme 3).
For alkyl aryl ketones, aryl migration appears to be predomi-
nant unless the alkyl group is bulky.1 For example, simple alkyl
aryl ketones gave the corresponding amides by preferential migra-
tion of the aryl group over the alkyl group. Similarly, cyclopropyl
aryl ketones afforded the amide with preferential migration of
the aryl group over the cyclopropyl moiety.12 In the case of ben-
zocycloalkenylketones with an ether linkage ortho or para to the
carbonyl group, the alkyl migration was concurrent with aryl
1
conversion. Various metal triflates such as Bi(OTf)
3 3
, In(OTf) ,
Sm(OTf) , Yb(OTf) and Sc(OTf) were found to be ineffective for
3
3
3
this conversion. The scope and generality of this process is illus-
trated with respect to various ketones, and the results are pre-
1
7
sented in Table 1. The advantages of this procedure include
mild reaction conditions as well as short reaction times, easy
work-up and good yields.
1
3
migration. For example, flavanone (chroman-4-one), on treat-
ment with TMSN /FeCl , underwent exclusive alkyl migration to
afford the 2-phenyl-1,4-benzoxazepin-5-(4H)-one (Table 1, entry
In summary, anhydrous FeCl
highly efficient reagent for the azido-Schmidt reaction of ketones
with TMSN under mild conditions. In addition to its simplicity
3
has proved to be a useful and
3
3
1
3
3
f, Scheme 3). Although phenyl migration was observed in the
and efficiency, this method produces amides, imides and lactams
in good to excellent yields in short reaction times. This method
provides an access to a wide range of potentially valuable lactams.
case of 1-tetralone, conversely, alkyl migration was observed with
2
-tetralone which was consistent with previous reports.14 With
a-
diketones, exclusive carbonyl migration was observed during the
azido-Schmidt reaction, which was similar to the Baeyer–Villiger
Acknowledgement
1
5
reaction. In all cases, the rearrangement products were identified
16
with authentic samples prepared by reported procedures. In the
absence of catalyst, the reaction did not proceed even after a long
reaction time (10–24 h). Furthermore, we have examined the pos-
U.V.S.R. and K.P. thank UGC New Delhi for the award of
fellowships.
sibility of FeCl
stoichiometric amounts. Interestingly, the reaction was also
successful with 10 mol % FeCl , albeit a long reaction time was
required (12 h, Table 2). The effects of various Lewis acids such
as InCl , InBr , ZrCl , YbCl and YCl were studied for this conver-
sion, and the results are presented in Table 2. Of these catalysts,
anhydrous FeCl was found to be the most effective in terms of
3
functioning catalytically or, at least, in less than
References and notes
3
1.
For recent reviews on chemical methods for amide synthesis, see: (a) Albericio,
F. Curr. Opin. Chem. Biol. 2004, 8, 211–221; (b) Mahajan, Y. R.; Weinreb, S. M. Sci.
Synth. 2005, 21, 17–25; (c) Ziegler, T. Sci. Synth. 2005, 21, 43–75; (d) Bode, J. W.
Curr. Opin. Drug Discov. Dev. 2006, 9, 765–775.
3
3
4
3
3
2.
(a) Schmidt, K. F. Angew. Chem. 1923, 36, 511–524; (b) Schmidt, K. F. Chem. Ber.
1924, 57, 704–706.
3
+
O
O
Fe(III) O
O
-
+
N
2
TMSO
N
N
N
O
2
FeCl3
TMSN3
Ph
Ph
Ph
O
N
Ph
TMSO
O
+
H
-
N
Me SiO
N
3
N2
O
O
O
Ph
Ph
Ph
Scheme 3.

J. S. Yadav et al. / Tetrahedron Letters 49 (2008) 4742–4745
4745
3
4
.
.
Krow, G. R. Tetrahedron 1981, 37, 1283–1307.
(a) McEwen, W. E.; Conrad, W. E.; Vanderwerf, C. A. J. Am. Chem. Soc. 1952, 74,
purified by column chromatography on silica gel (Merck, 100–200 mesh) using
ethyl acetate/hexane (4:6) as eluent to afford the pure derivative. Replacing
1
168–1171; (b) Smith, P. A. S.; Horwitz, J. P. J. Am. Chem. Soc. 1950, 72, 3718–
3 3
TMSN with NaN , the same procedure afforded the same products in relatively
3
722.
longer reaction times (Table 1).
5
6
.
.
For reviews, see: (a) Bräse, S.; Gil, C.; Knepper, K.; Zimmermann, V. Angew.
Chem., Int. Ed. 2005, 44, 5188–5240; (b) Lang, S.; Murphy, J. A. Chem. Soc. Rev.
Compound 3d: 1-azacyclotridecan-2-one
(Table 1, entry d): White solid,
mp = 143–145 °C. IR (KBr)
mmax: 3307, 3082, 2931, 2856, 1639, 1550, 1448,
1283, 1185, 739, 691 cm . 1H NMR (CDCl
1H), 3.21–3.12 (m, 2H), 2.14–2.09 (m, 2H), 1.64–1.19 (m, 18H); C NMR
(CDCl , 75 MHz): d 173.5, 38.9, 36.7, 28.1, 26.6, 26.2, 26.1, 25.6, 25.1, 24.8, 24.5,
À1
2
006, 35, 146–156; (c) Nyfeler, E.; Renaud, P. Chimia 2006, 60, 276–284.
3
+ DMSO, 200 MHz): d 7.23 (br s,
13
(a) Briggs, L. H.; De Ath, G. C.; Ellis, S. R. J. Chem. Soc. 1942, 61–63; (b) Smith, P.
A. S. J. Am. Chem. Soc. 1948, 70, 320–323; (c) Pearson, W. H.; Schkeryantz, J. M.
Tetrahedron Lett. 1992, 33, 5291–5294; (d) Pearson, W. H.; Walavalkar, R.;
Schkeryantz, J. M.; Fang, W.-k.; Blickensdorf, J. D. J. Am. Chem. Soc. 1993, 115,
3
+
+
23.8; LCMS: m/z: 198 (M+H) . HRMS calcd for C12H24NO (M+H) : 198.1857.
Found: 198.1855.
1
5
4
0183–10194; (e) Pearson, W. H.; Fang, W.-k.; Kampf, J. W. J. Org. Chem. 1994,
9, 2682–2684; (f) Pearson, W. H.; Fang, W.-k. J. Org. Chem. 1995, 60, 4960–
961; (g) Pearson, W. H. J. Heterocycl. Chem. 1996, 33, 1489–1496; (h) Pearson,
Compound 3f: 3,4-Dihydro-2-phenylbenzo[f][1,4]oxazepin-5(2H)-one (Table 1,
entry f): Light brown solid, mp = 126–127 °C. IR (KBr) max: 3405, 3035, 2924,
3
2853, 1743, 1608, 1484, 1230, 1113, 1032, 769, 696 cm ; H NMR (CDCl ,
m
À1
1
W. H.; Fang, W.-k. Isr. J. Chem. 1997, 37, 39–46.
300 MHz): d 8.60–8.57, (m, 1H), 7.53–7.42 (m, 6H), 7.29–7.23 (m, 2H), 7.17–
7.14 (m, 1H), 5.22 (dd, J = 1.5, 8.3 Hz, 1H), 5.11 (dd, J = 1.5, 13.2 Hz, 1H), 4.82
7
.
(a) Aubé, J.; Milligan, G. L. J. Am. Chem. Soc. 1991, 113, 8965–8966; (b) Aube, J.;
Milligan, G. L.; Mossman, C. J. J. Org. Chem. 1992, 57, 1635–1637; (c) Aube, J.;
Rafferty, P. S.; Milligan, G. L. Heterocycles 1993, 35, 1141–1147; (d) Milligan, G.
L.; Mossman, C. J.; Aubé, J. J. Am. Chem. Soc. 1995, 117, 10449–10459; (e)
Mossman, C. J.; Aube, J. Tetrahedron 1996, 52, 3403–3408; (f) Desai, P.;
Schildknegt, K.; Agrios, K. A.; Mossman, C.; Milligan, G. L.; Aubé, J. J. Am. Chem.
Soc. 2000, 122, 7226–7232; (g) Sahasrabudhe, K.; Gracias, V.; Furness, K.; Smith,
B. T.; Katz, C. E.; Reddy, D. S.; Aube, J. J. Am. Chem. Soc. 2003, 125, 7914–7922.
(a) Groutas, W. C.; Felker, D. Synthesis 1980, 861–868; (b) Colvin, E. W. Silicon
Reagents for Organic Synthesis, San Diego, 1983.
(dd, J = 9.8, 4.7 Hz, 1H); 13C NMR (CDCl
+ DMSO, 100 MHz): d 158.6, 151.8,
3
136.4, 132.1, 129.0, 128.0, 127.9, 125.1, 122.8, 120.5, 112.0, 77.7, 54.9; LCMS:
+
m/z: 239 (20, M) , 218 (30), 192 (100), 139 (50), 116 (75).
Compound 3g: 2,3,4,5-tetrahydro-1H-3-benzazepin-2-one (Table 1, entry g): pale
yellow solid, mp = 148–150 °C. IR (KBr)
m
max: 3420, 2924, 2855, 1732, 1523,
H NMR (CDCl , 300 MHz): d 7.40–7.28 (m, 4H),
5.62 (s, 2H), 4.62 (br s, 1H), 3.41–3.33 (m, 2H), 3.26–3.21 (m, 2H); C NMR
(CDCl , 75 MHz): d 172.6, 135.4, 131.2, 130.1, 128.8, 127.1, 124.6, 42.1, 40.0,
À1
1
1457, 1246, 1081, 754 cm
.
3
13
8
.
.
3
+
34.3; LCMS: m/z: 184 (100) (M+Na) .
9
(a) Bolm, C.; Legros, J.; Le Paih, J.; Zani, L. Chem. Rev. 2004, 104, 6217–6254; (b)
Ruping, M.; Nactshim, B. J.; Scheidt, T. Org. Lett. 2006, 8, 3717–3719; (c)
Komeyama, K.; Morimoto, T.; Takaki, K. Angew. Chem., Int. Ed. 2006, 45, 2938–
Compound 3h: Quinazoline-2,4-(1H,3H)-dione (Table 1, entry h): White solid,
mp = 295–298 °C. IR (KBr)
1485, 1355, 1263, 1126, 1009, 756, 649 cm
200 MHz): d 9.68 (br s, 1H), 9.25 (br s, 1H), 8.13 (d, J = 9.5 Hz, 1H), 7.43–7.29
(m, 3H); 13C NMR (CDCl
+ DMSO, 50 MHz): d 178.3, 154.8, 141.6, 133.3, 132.5,
mmax: 3392, 3310, 3106, 3031, 2952, 1695, 1601,
À1
1
;
3
H NMR (CDCl + DMSO,
2941; (d) Kischel, J.; Jovel, I.; Mertins, K.; Zapf, A.; Beller, M. Org. Lett. 2006, 8,
19–22; (e) Diaz, D. D.; Miranda, P. O.; Padron, J. I.; Martin, V. S. Curr. Org. Chem.
2006, 10, 457–476; (f) Iovel, I.; Mertins, K.; Kischel, J.; Zapf, A.; Beller, M. Angew.
3
+
124.8, 122.6, 121.4; LCMS: m/z: 162 (90, M) , 135 (30), 118 (35), 87 (100).
Compound 3i: 6-Methylquinazoline-2,4-(1H,3H)-dione (Table 1, entry i): Pale
Chem., Int. Ed. 2005, 44, 3913–3917.
1
1
0. Smith, P. A. S. In Molecular Rearrangements. Part I; de Mayo, P., Ed.; John Wiley &
Sons: New York, 1963; p 510.
1. Kate, P. T.; Mphalele, M. J.; Brown, M. E. J. Chem. Soc., Perkin Trans. 2 1995, 835–
yellow solid mp = 287–289 °C. IR (KBr)
1536, 1302, 1244, 1157, 971, 831, 737, 616 cm
200 MHz) d: 9.74 (br s, 1H), 7.61 (br s, 1H), 7.42–7.32 (m, 2H), 7.07 (d,
J = 8.0 Hz, 1H), 2.37 (s, 3H); 13C NMR (CDCl
+ DMSO, 50 MHz) d: 179.2, 154.5,
147.5, 136.4, 134.0, 132.5, 123.6, 116.0, 19.9; LCMS: m/z: 199 (70, M+Na) , 173
(100), 143 (35), 101 (45).
mmax: 3457, 3301, 2924, 1682, 1591,
À1
1
;
3
H NMR (CDCl + DMSO,
8
38.
3
+
1
1
1
2. Bunce, S. C.; Cloke, J. B. J. Am. Chem. Soc. 1953, 76, 2244–2248.
3. Misiti, D.; Rimatori, V. Tetrahedron Lett. 1970, 11, 947–950.
4. (a) Knunyants, L.; Fabrichnyi, B. P. Dok. Akad. Nauk. S.S.S.R. 1949, 68, 523–526;
Knunyants, L.; Fabrichnyi, B. P. Chem. Abstr. 1950, 1469; (b) Katoh, M.; Inoue,
H.; Honda, T. Heterocycles 2007, 72, 497–516.
Compound 3j: Isoquinoline-1,3,4-(2H)-trione (Table 1, entry j): Light brown
solid, mp = 227–229 °C. IR (KBr)
1379, 1304, 1137, 1051, 712, 647 cm ; 1 H NMR (CDCl + DMSO, 200 MHz) d:
3
10.98 (br s, 1H, NH), 7.78–8.00 (m, 4H); C NMR (CDCl + DMSO, 100 MHz) d:
mmax: 3448, 2921, 2851, 1750, 1637, 1463,
À1
1
3
3
1
1
5. ten Brink, G.-J.; Arends, I. W. C. E.; Sheldon, R. A. Chem. Rev. 2004, 104, 4105–
4
123.
169.8, 159.1, 149.6, 135.4, 134.9, 133.5, 132.6, 132.3, 122.7; EIMS: m/z: 174
+
6. (a) Eshghi, H.; Hassankhani, A. J. Korean Chem. Soc. 2007, 51, 361–364; (b)
Arisawa, M.; Yamaguchi, M. Org. Lett. 2001, 3, 311–312; (c) Luca, L. D.;
Giacomelli, G.; Porcheddu, A. J. Org. Chem. 2002, 67, 6272–6274; (d)
Ramalingan, C.; Park, Y. T. J. Org. Chem. 2007, 72, 4536–4538; (e) Eshghi, H.;
Gordi, Z. Synth. Commun. 2003, 33, 2971–2978; (f) Capuano, G.; Giammanco, L.
Gazz. Chim. Ital. 1956, 86, 119; (g) Ling, K. Q.; Ye, J. H.; Chen, X. Y.; Ma, D. J.; Xu,
J. H. Tetrahedron 1999, 55, 9185–9204.
(20, M À H) , 147 (MÀCO), 132 (20), 104 (100).
Compound 3n: N-(4-Iodophenyl)acetamide (Table 1, entry n): Brown solid,
mp = 142–144 °C. IR (KBr)
1387, 1310, 1250, 1001, 817,726 cm
9.62 (br s, 1H), 7.54–7.33 (m, 4H), 2.07 (s, 3H); C NMR (CDCl
100 MHz) d: 167.8, 137.9, 136.2, 120.5, 85.2, 23.3; LCMS: m/z: 283 (M+Na) ;
HRMS (ESI): calcd for C NONaI, 283.9548; found, 283.9540.
Compound 3q: N-(4-Methoxyphenyl)cyclopropanecarboxamide (Table 1, entry
q): White solid, mp = 125–127 °C. IR (KBr) max: 3302, 3007, 2922, 2852, 1648,
mmax: 3304, 3183, 2923, 2852, 1668, 1599, 1483,
À1
1
;
H NMR (CDCl
3
+ DMSO, 200 MHz) d:
+ DMSO,
13
3
+
8 8
H
1
7. General procedure: To
a
stirred solution of ketone (1.0 mmol) in 1,2-
(1.5 mmol) and FeCl (1.0 mmol).
dichloroethane (5 mL) were added TMSN
3
3
m
1
À1
The resulting mixture was stirred at room temperature for the appropriate
time (Table 1). After complete conversion as indicated by TLC, the solvent was
removed by evaporation and the residue was diluted with water and extracted
with ethyl acetate (2 Â 10 mL). The combined organic layers were dried over
1532, 1413, 1246, 1175, 1031, 827 cm
9.56 (br s, 1H), 7.46 (d, J = 8.8 Hz, 2H), 6.75 (d, J = 8.8 Hz, 2H), 3.76 (s, 3H), 1.75–
1.63 (m, 1H), 0.96–0.86 (m, 2H), 0.76–0.67 (m, 2H). 13C NMR (CDCl
, 100 MHz):
d 171.9, 156.3, 131.1, 121.4, 114.2, 55.5, 15.4, 7.8; LCMS: m/z: 192 (M+H) ;
HRMS (ESI): calcd for C11 14NO , 192.1024; found, 192.1014.
3
; H NMR (CDCl + DMSO, 200 MHz) d:
3
+
anhydrous Na
2
SO
4
and concentrated in vacuo. The resulting product was
H
2