Expedient one-pot synthesis of N-aryliminoethers via mild electrophilic activation of secondary amides

Article abstract of DOI:10.1007/s00706-011-0603-6

The direct transformation of various secondary amides into N-aryliminoethers via mild electrophilic activation with trifluoromethanesulfonic anhydride in the presence of 2-chloropyridine is described. Low temperature amide activation followed by warming t

Full text of DOI:10.1007/s00706-011-0603-6

Monatsh Chem (2012) 143:455–460
DOI 10.1007/s00706-011-0603-6
ORIGINAL PAPER
Expedient one-pot synthesis of N-aryliminoethers via mild
electrophilic activation of secondary amides
•
Mehdi Ghandi Mohammad Hasani
•
Saleh Salahi
Received: 29 August 2010 / Accepted: 15 July 2011 / Published online: 16 August 2011
Ó Springer-Verlag 2011
Abstract The direct transformation of various secondary
amides into N-aryliminoethers via mild electrophilic acti-
vation with trifluoromethanesulfonic anhydride in the
presence of 2-chloropyridine is described. Low tempera-
ture amide activation followed by warming to 0 °C and
subsequent treatment with phenols provides the desired
products with short overall reaction times and moderate to
high reaction yields.
separated either by fractional distillation or precipitation
under anhydrous conditions. An alternative method for the
formation of of N-arylimidates includes the use of oxalyl
chloride as chlorinating agent in the presence of 2,6-luti-
dine at 0 °C, which generates the imidoyl chlorides in situ
without the formation of by-products [11]. Due to the low
reactivity of imidoyl chlorides, stoichiometeric amounts of
Lewis acids [12–14] or the use of more nucleophililic
phenoxide anions [6–9] are required.
Keywords N-aryliminoethers ꢀ
Trifluoromethanesulfonic anhydride ꢀ
Electrophilic addition ꢀ One-pot synthesis ꢀ
Nucleophilic substitution
Nitrilium ions generated as intermediates under Beck-
mann rearrangement conditions or via activation of imidoyl
chlorides with stoichiometeric amounts of Lewis acids play
a key role in the production of imidates. A combination of
Tf2O and pyridine in the pioneering work of Charette and
Grenon in their synthesis of amidines, thiazolines, thioam-
ides, cyclic orthoesters, and esters has proven to be a useful
reagent for the activation of amides and their subsequent
conversion into other functional groups [15–20]. In 2006,
Movassaghi developed an efficient method for the conver-
sion of amides into highly electrophilic 2-chloropyridinium
adducts by using a combination of Tf2O and 2-chloropyri-
dine [21], which enabled the synthesis of a variety of
azaheterocycles [22–25]. In contrast to pyridine as a strong
nucleophile, 2-chloropyridine was found not to add to Tf2O.
Compared to the reported methods for the synthesis
of N-arylimidates (vide supra), we considered that the
development of new methodologies would allow the
activation of a variety of amide substrates, including
N-arylamides, without requiring the isolation of sensitive
intermediates or the use of Lewis acid additives, and
shortening reaction times without the need for elevated
temperatures. Herein, we describe an expedient one-pot
transformation of various secondary amides into N-aryl-
imidates via mild electrophilic activation with Tf2O in the
presence of 2-chloropyridine.
Introduction
Aryliminoethers serve as starting materials in the Chapman
rearrangement for the production of N,N-diarylamides
[1–3]. The Beckmann rearrangement of ketoximes [4, 5]
and addition of alcohols to imidoyl chlorides [6–9] have
been reported as general methods for the production of
iminoethers. The dehydration of secondary amides for the
generation of imidoyl chlorides has generally been carried
out by reaction with chlorinating reagents such as PCl5,
SOCl2, and POCl3 in excess at elevated temperatures or
by treatment with Ph3P/CCl4 at room temperature [10].
Disadvantages of these methods are that the excess dehy-
drating agent- and reagent-derived by-products have to be
removed. Moreover, pure imidoyl chlorides should be
M. Ghandi (&) ꢀ M. Hasani ꢀ S. Salahi
School of Chemistry, College of Science, University of Tehran,
P.O. Box 14155-6455, Tehran, Iran
e-mail: ghandi@khayam.ut.ac.ir
123

456
M. Ghandi et al.
Results and discussion
Scheme 1). The reaction proceeds with less efficiency when
using the Hendrickson reagent (Table 1, entry 8) [26].
Therefore, the superiority of Tf2O/2-chloropyridine com-
bination as an amide-activating agent is evident.
Initially, we optimized the conditions for the synthesis of
phenyl N-p-tolylpivalimidate (3a) from N-p-tolylpivala-
mide (1a) and phenol (2a) (Table 1). 2-Chloropyridine
proved to be the best base and gave a 93% yield of 3a
(Table 1, entry 6). While base additives such as Et3N and
pyridine had no effect on the reaction progress (Table 1,
entries 3, 4), other bases activated amide 1a with moderate
efficiencies (Table 1, entries 2, 5, and 8). An excess of
2-chloropyridine was found to have an inhibitory effect
(Table 1, entry 8), perhaps by shifting the equilibrium away
from 6, the more active nitrilium intermediate, towards 5,
the less active amidinium intermediate, in order to coun-
teract the increasing concentration of 2-chloropyridine (see
Identification of the products was confirmed by their
analytical and spectral data. For example, no signals due to
1
OH group were evident in the H NMR and IR spectra of
1
3g. Moreover, characteristic H NMR signals appeared at
d = 1.21 (s, 9H) and 1.44 (s, 9H) for two t-Bu groups
together with two AB patterns at d = 6.61 (d, 2H,
J = 9.0 Hz), 6.68 (d, 2H, J = 6.8 Hz), 7.06 (d, 2H,
J = 6.8 Hz), and 7.85 (d, 2H, J = 9.0 Hz) because of
aromatic protons.
We next explored the substrate scope with the optimal
conditions with a variety of secondary amides and phenols.
Table 1 Effect of base on the direct conversion of amide 1a to N-aryliminoether 3a via mild electrophilic activation by Tf2O
Me
Me
Me
Me
Me
H
N
N
OH
Tf2O, Base/CH2Cl2
Me
O
25 °C,
3 h
+
-78 °C,
5 min
O
Me
Me
1a
2a
3a
Entry
Base
Equiv
Yield/%a
1
2
3
4
5
6
7
8
None
–
41
43
0
K2CO3
Et3N
1.2
1.2
1.2
1.2
1.2
2.0
1.2
Pyridine
0
2,6-Lutidine
73
93
85
80
2-Chloropyridine
2-Chloropyridine
Hendrickson reagentb
Reaction conditions: Amide (1.0 equiv), Tf2O (1.1 equiv), 2-chloropyridine (1.2 equiv), CH2Cl2, -78 °C, 5 min, then 25 °C, 1 h
a
Isolated yields
b
Triphenylphosphonium anhydride trifluoromethanesulfonate was used without 2-chloropyridine at 0 °C
Scheme 1
TfO
R1
N
R1
Cl
N
R2
H
TfO
H
N
- 2-ClPyr
TfOH
5
O
N
R2
R1
2-ClPyr
TfO
R2
Tf2O
R3
N
R2
TfO
O
1
H
OH
R1
R3
4
3
TfO
N
R2
+ 2-ClPyr
TfOH
R1
6
123

Expedient one-pot synthesis of N-aryliminoethers
457
Table 2 Results obtained for the direct conversion of amides to N-aryliminoethers 3a–3o via mild electrophilic activation by Tf2O
R2
Tf2O, 2-ClPyr
CH2Cl2
H
N
R2
OH
N
+
O
25 °C,
1h
-78 °C,
5 min
O
R1
R3
R1
R3
1
2
3
Entry
R1
4-Me–
R2
R3
Product
Yield/%a
1
t-Bu–
t-Bu–
t-Bu–
t-Bu–
t-Bu–
t-Bu–
t-Bu–
t-Bu–
t-Bu–
t-Bu–
t-Bu–
C6H11
Ph–
H–
H–
3a
3b
3c
3d
3e
3f
93
92
78
65
98
80
92
78
67
71
96
80
62
58
65
2
3,4-(Me)2–
4-Cl–
3
4-NO2–
H–
4
4-Cl–
5
4-Me–
4-NO2–
4-Cl–
4-t-Bu–
4-t-Bu–
4-t-Bu–
2,4-(Cl)2–
4-NO2–
2,4-(Cl)2–
H–
6
7
3g
3h
3i
8
4-OMe–
3,4-(Me)2–
4-Cl–
9
10
11
12
13
14
15
3j
4-MeO–
H–
3k
3l
2,4-(Cl)2–
4-t-Bu–
4-t-Bu–
H–
4-Me–
4-Cl–
3m
3n
3o
Ph–
4-OMe–
Ph–
Reaction conditions: Amide (1.0 equiv), Tf2O (1.1 equiv), 2-chloropyridine (1.2 equiv), CH2Cl2, -78 °C, 5 min, then 25 °C, 1 h
a
Isolated products
Scheme 2
Me Me
Me
OH
Me
Me
N
9
H
N
O
+
Me
O
Me
7
Tf2O, 2-ClPyr
CH2Cl2
(88%)
Me
Me Me
25 °C,
3 h
-78 °C,
5 min
Me
Me
Me
H
N
N
OH
O
Me
+
O
MeO
10
(94%)
MeO
8
Results are presented in Table 2. Inspection of the results
presented in Table 2 reveals that substrates with electron
donating as well as electron withdrawing groups were
tolerated in the reaction. While relatively electron-rich
pivalamides afford the corresponding N-aryliminoethers
with 92–98% yields (Table 2, entries 1, 2, 5), reaction of
relatively electron-deficient benzamides proceeds to the
products less efficiently (Table 2, entries 13, 14, 15).
Whereas relatively electron-rich pivalamides in reaction
with relatively electron-deficient phenols gave N-arylimi-
noethers in lower yields (Table 2, entries 8, 9), reactions of
electron-deficient benzamides with electron-rich phenols
proceeded in good to high yields (Table 2, entry 13).
To rationalize the reaction results, the previously sug-
gested reaction pathway depicted in Scheme 1 seems to be
operative in our method. As illustrated in Scheme 1,
123

458
M. Ghandi et al.
activation of amides 1 affords the imidoyl triflate 4. Sub-
sequent addition of 2-chloropyridine to 4 gives the
pyridinium adduct 5. This species is believed to be in
equilibrium with the nitrilium ion 6, a more powerful
electrophile [23–26]. Electron-rich amides with higher
propensity to form a nitrilium ion upon activation with
Tf2O/2-chloropyridine combination are expected to give
the highest yields. On the other hand, electron-deficient
amides reluctant to form the corresponding nitrilium ion
under the reaction conditions also afford the lowest yields,
likely owing to the inductive effect of the nitrogen
substituent.
-78 °C with dry ice in acetone; 0.181 cm3 Tf2O
(1.1 mmol) was then added with a syringe under argon
atmosphere. After 5 min, the reaction mixture was warmed
to 0 °C and 94 mg phenol (1.0 mmol) was added in one
portion. The mixture was allowed to warm to ambient
temperature and stirred for 3 h. The progress of the reac-
tion was monitored with TLC. After completion of the
reaction, 10 cm3 sodium hydroxide solution (0.1 M) was
added to neutralize the acidic salts. The organic phase was
then separated, washed with brine, and dried over anhy-
drous Na2SO4. The solvent was then evaporated under
reduced pressure, and the residue was purified with column
chromatography (silica gel, 5% ethyl acetate in hexane).
Finally, we examined the effect of 1- and 2-naphthol on
reaction efficiency (Scheme 2). Reactions with 1-naphthol
(7) and 2-naphthol (8) proceeded similarly to those with
phenols affording the corresponding N-arylimidates 9 and
10 in 88 and 94% yields, respectively.
Phenyl N-(4-methylphenyl)pivalimidate (3a, C18H21NO)
White solid; yield 250 mg (93%); m.p.: 50–52 °C;
ꢀ
Rf = 0.72; IR (KBr): m ¼ 3;071; 2;968; 2;889; 1;671;
1;589 cm-1
;
1H NMR (500 MHz, CDCl3): d = 1.42 (s,
In conclusion, we have developed a new and expedient
one-pot procedure for the transformation of secondary
amides into the corresponding N-aryliminoethers via
reaction of phenols with activated secondary amides using
Tf2O/2-chloropyridine combination. Advantages such as
highly effective activation of a variety of amide substrates,
including N-arylamides, without requiring the isolation of
the sensitive intermediates or the use of Lewis acid addi-
tives, and shortening reaction times without the need for
elevated temperatures are the outcome of our methodology.
We have also found that these mild conditions do not
produce the by-products observed in the previous cases,
which proceeded at elevated temperatures.
t-Bu), 2.19 (s, Me), 6.67 (d, J = 8.0 Hz, Ar-H), 6.77 (d,
J = 5.8 Hz, 2 Ar- H), 6.86 (d, J = 8.0 Hz, 2 Ar-H), 6.88
(s, Ar-H), 7.10 (t, J = 7.2 Hz, 2 Ar-H) ppm; 13C NMR
(125 MHz, CDCl3): d = 21.2, 28.5, 39.7, 118.4, 121.6,
122.8, 129.1, 129.3, 132.6, 143.9, 155.1, 163.1 ppm;
EI-MS: m/z (%) = 268 (M??1, 100), 248 (68), 219 (80),
191 (9), 131 (16), 77 (6), 47 (8).
Phenyl N-(3,4-dimethylphenyl)pivalimidate
(3b, C19H23NO)
Yellow oil; yield 259 mg (92%); Rf = 0.70; IR (KBr):
ꢀ
m ¼ 3;075; 2;967; 2;890; 1;675; 1;594; 1;487; 1;204; 1;086
cm-1
;
1H NMR (500 MHz, CDCl3): d = 1.43 (9H, s,
t-Bu), 2.11 (6H, s, Me), 6.53 (1H, d, J = 7.8 Hz, Ar- H),
6.55 (1H, s, Ar-H), 6.78 (2H, bd, J = 5.8 Hz, Ar-H), 6.82
(2H, d, J = 7.8 Hz, Ar-H), 6.87 (1H, bt, J = 6.8 Hz,
Ar-H), 7.10 (2H, bt, J = 7.1, Ar-H) ppm; 13C NMR
(125 MHz, CDCl3): d = 19.4, 20.0, 28.6, 39.6, 118.6,
119.0, 122.8, 123.1, 129.2, 129.7, 131.2, 136.4, 144.2,
155.1, 162.8 ppm; EI-MS: m/z (%) = 281 (M?, 9), 188
(87), 132 (100), 121 (42), 105 (21), 77 (15), 57 (25).
Experimental
All commercially available chemicals and reagents were
used without further purification. Melting points were
determined with an Electrothermal model 9100 apparatus.
IR spectra were recorded on a Shimadzu 4300 spectro-
1
photometer. H and 13C NMR spectra were obtained on a
Bruker DRX-500-AVANCE spectrometer at 500 (1H) and
125 MHz (13C) using CDCl3 as solvent and TMS as
internal standard. Mass spectra of the products were
obtained with a HP (Agilent technologies) 5937 mass
selective detector. Elemental analyses were carried out by a
CHN-O-Rapid Heraeus elemental analyzer (Wellesley,
MA). TLC of samples were carried out on silica gel plates
using a 10:1 hexane-ethyl acetate mixture.
4-Nitrophenyl N-(4-chlorophenyl)pivalimidate
(3c, C17H17ClN2O3)
Colorless solid; yield 216 mg (65%); m.p.: 79–80 °C;
ꢀ
Rf = 0.58; IR (KBr): m ¼ 3;081; 2;969; 2;891; 1;667; 1;587;
1;479; 1;275; 1;205; 1;089 cm-1
;
1H NMR (500 MHz,
CDCl3): d = 1.39 (9H, s, t-Bu), 6.72 (1H, d, J = 8.3 Hz,
Ar-H), 6.84 (1H, d, J = 6.8 Hz, Ar-H), 7.04 (1H, d,
J = 8.3 Hz, Ar-H), 7.26 (1H, d, J = 8.8 Hz, Ar-H), 7.49
(1H, d, J = 8.9 Hz, Ar-H), 8.01 (1H, d, J = 8.5 Hz,
Ar-H), 8.27 (1H, d, J = 8.8 Hz, Ar-H), 8.36 (1H, d,
J = 8.9 Hz, Ar-H) ppm; 13C NMR (125 MHz, CDCl3):
d = 27.4, 39.7, 118.0, 122.8, 122.9, 125.5, 125.8, 126.4,
129.0, 144.1, 145.6, 153.5, 156.4, 159.5, 176.5 ppm;
Typical procedure for the preparation of 3a–3i
A solution of amide (1.0 mmol) and 0.113 cm3 2-chloro-
pyridine (1.2 mmol) in 10 cm3 CH2Cl2 was cooled to
123

Expedient one-pot synthesis of N-aryliminoethers
459
EI-MS: m/z (%) = 334 (M??2, 4), 332 (11), 196 (34), 194
(81), 140 (44), 138 (100), 111 (19), 57 (34).
2,4-Dichlorophenyl N-(4-methoxyphenyl)pivalimidate
(3h, C18H19Cl2NO2)
Pale yellow solid; yield 275 mg (78%); m.p.: 52–53 °C;
Rf = 0.64; IR (KBr): ꢀm ¼ 3;075; 2;968; 2;886; 1;672; 1;608;
Phenyl N-(4-chlorophenyl)pivalimidate
(3d, C17H18ClNO)
1;465; 1;231; 1;076 cm-1 1H NMR (500 MHz, CDCl3):
;
White solid; yield 239 mg (83%); m.p.: 75–76 °C; Rf =
d = 1.39 (9H, s, t-Bu), 3.74 (3H, s, OMe), 6.65-6.73 (5H,
m, Ar-H), 6.98 (1H, bs, Ar-H), 7.23 (1H, bs, Ar-H) ppm;
13C NMR (125 MHz, CDCl3): d = 28.6, 39.8, 55.9, 114.1,
114.2, 114.3, 114.4, 120.2, 122.1, 127.6, 130.1, 149.2,
156.2 ppm; EI-MS: m/z (%) = 351 (M?, 6), 190 (46), 134
(100), 107 (14), 57 (79).
ꢀ
0.70; IR (KBr): m ¼ 3;085; 2;975; 2;888; 1;670; 1;589
cm-1
;
1H NMR (500 MHz, CDCl3): d = 1.42 (9H, s,
t-Bu), 6.65 (2H, d, J = 8.6 Hz, Ar-H), 6.74 (2H, d,
J = 7.3 Hz, Ar-H), 6.90 (1H, t, J = 7.3 Hz, Ar-H), 7.00
(2H, d, J = 8.6 Hz, Ar-H), 7.11 (2H, t, J = 7.5 Hz, Ar-H)
ppm; 13C NMR (125 MHz, CDCl3): d = 28.5, 39.7, 118.8,
122.9, 123.4, 128.3, 128.6, 129.5, 145.3, 154.9, 164.3 ppm;
EI-MS: m/z (%) = 287 (M?, 7), 196 (41), 194 (97), 140
(41), 138 (100), 111 (15), 57 (63).
4-Nitrophenyl N-(3,4-dimethylphenyl)pivalimidate
(3i, C19H22N2O3)
Yellow solid; yield 218 mg (67%); m.p.: 89–90 °C; Rf =
ꢀ
0.60; IR (KBr): m ¼ 3;074; 2;968; 2;885; 1;670; 1;584;
1;511; 1;376; 1;219; 1;075 cm-1
;
1H NMR (500 MHz,
4-tert-Butylphenyl N-(4-methylphenyl)pivalimidate
(3e, C22H29NO)
CDCl3): d = 1.41 (9H, s, t-Bu), 2.10 (6H, s, Me), 6.56
(1H, d, J = 7.8 Hz, Ar-H), 6.60 (1H, s, Ar-H), 6.83 (3H,
m, Ar-H), 7.99 (2H, bt, J = 8.7 Hz, Ar-H) ppm; 13C NMR
(125 MHz, CDCl3): d = 19.5, 20.0, 28.2, 39.6, 117.8,
119.1, 123.2, 125.6, 130.1, 132.6, 137.1, 140.5, 143.0,
159.9, 160.9 ppm; EI-MS: m/z (%) = 326 (M?, 13), 188
(97), 132 (100), 105 (21), 57 (21).
White solid; yield 316 mg (98%); m.p: 71–72 °C; Rf =
ꢀ
0.68; IR (KBr): m ¼ 2;963; 1;668; 1;503; 1;214; 1;082;
819 cm-1
;
1H NMR (500 MHz, CDCl3): d = 1.25 (s,
9H, t-Bu), 1.42 (s, 9H, t-Bu), 2.17 (s, 3H), 6.56 (d,
J = 8.2 Hz, 2H), 6.67 (bs, 2H), 6.80 (d, J = 7.4 Hz, 2H),
7.06 (bs, 2H) ppm; 13C NMR (125 MHz, CDCl3):
d = 21.1, 28.6, 31.8, 34.5, 39.5, 118.8, 121.4, 125.9,
128.9, 132.0, 144.3, 146.5, 152.8, 163.6 ppm; EI-MS: m/z
(%) = 323 (M?, 6), 174 (100), 118 (94), 91 (24), 57 (13).
2,4-Dichlorophenyl N-(4-chlorophenyl)pivalimidate
(3j, C17H16Cl3NO)
Yellow solid; yield 353 mg (71%); m.p.: 49–50 °C;
ꢀ
Rf = 0.61; IR (KBr): m ¼ 3;078; 2;971; 2;897; 1;690;
4-tert-Butylphenyl N-(4-nitrophenyl)pivalimidate
(3f, C21H26N2O3)
1;581; 1;473; 1;230; 1;083 cm-1
;
1H NMR (500 MHz,
CDCl3): d = 1.38 (9H, s, t-Bu), 6.66 (2H, d, J = 9.6 Hz,
Ar-H), 6.84 (1H, bd, J = 6.0 Hz, Ar-H), 7.08 (3H, m,
Ar-H), 7.28 (1H, bs, Ar-H) ppm; 13C NMR (125 MHz,
CDCl3): d = 28.9, 40.1, 121.9, 125.0, 127.9, 128.3, 128.4,
128.7, 130.3, 130.5, 145.0, 149.0, 162.1 ppm; EI-MS:
m/z (%) = 360 (M?, 4), 358 (19), 356 (19), 196 (46), 194
(100), 140 (23), 138 (65), 111 (12), 57 (43).
White solid; yield 283 mg (80%); m.p.: 100–102 °C;
Rf = 0.75; IR (KBr): ꢀm ¼ 3;078; 2;962; 2;891; 1;698;
1;585; 1;500; 1;322; 1;100 cm-1
;
1H NMR (500 MHz,
CDCl3): d = 1.21 (9H, s, t-Bu), 1.44 (9H, s, t-Bu), 6.61
(2H, d, J = 9.0 Hz, Ar-H), 6.68 (2H, d, J = 6.8 Hz,
Ar-H), 7.06 (2H, d, J = 6.8 Hz, Ar-H), 7.85 (2H, d,
J = 9.0 Hz, Ar-H) ppm; 13C NMR (125 MHz, CDCl3):
d = 28.5, 31.7, 34.6, 39.7, 120.3, 121.2, 124.3, 126.4,
142.7, 147.9, 152.1, 153.8, 164.9 ppm; EI-MS: m/z (%) =
354 (M?, 5), 205 (100), 149 (50), 57 (90).
Phenyl N-(4-methoxyphenyl)pivalimidate
(3k, C18H21NO2)
White solid; yield 272 mg (96%); m.p.: 67–68 °C; Rf =
ꢀ
0.73; IR (KBr): m ¼ 3;068; 2;977; 2;890; 1;665; 1;590;
4-tert-Butylphenyl N-(4-chlorophenyl)pivalimidate
(3g, C21H26ClNO)
1;491; 1;207; 1;060 cm-1
;
1H NMR (500 MHz, CDCl3):
d = 1.42 (9H, s, t-Bu), 3.70 (3H, s, OMe), 6.61 (2H, d,
J = 8.7 Hz, Ar-H), 6.74-6.76 (3H, m, Ar-H), 6.85 (2H, bt,
J = 6.8 Hz, Ar-H), 7.71 (2H, bt, J = 6.8 Hz, Ar-H) ppm;
13C NMR (125 MHz, CDCl3): d = 28.4, 39.6, 55.8, 114.0,
117.9, 122.7, 123.1, 129.3, 129.4, 155.0, 156.0, 163.0 ppm;
EI-MS: m/z = 283 (M?, 33), 190 (89), 134 (100), 107 (9),
57 (22).
Colorless solid; yield 316 mg (92%); m.p.: 49–51 °C;
ꢀ
Rf = 0.57; IR (KBr): m ¼ 3;073; 2;963; 2;889; 1;670;
1;595; 1;478; 1;214; 1;085 cm-1
;
1H NMR (500 MHz,
CDCl3): d = 1.26 (9H, s, t-Bu), 1.43 (9H, s, t-Bu), 6.55
(2H, d, J = 8.5 Hz, Ar-H), 6.64 (2H, d, J = 7.9 Hz,
Ar-H), 6.93 (2H, d, J = 8.5 Hz, Ar-H), 7.08 (2H, d,
J = 7.9 Hz, Ar-H) ppm; 13C NMR (125 MHz, CDCl3):
d = 28.5, 31.8, 34.5, 39.5, 119.2, 121.2, 122.8, 126.1,
126.6, 128.3, 146.6, 152.6, 164.7 ppm; EI-MS: m/z (%) =
345 (M??2, 6), 343 (13), 196 (42), 194 (95), 140 (46), 138
(100), 111 (20), 57 (51).
2,4-Dichlorophenyl N-phenylcyclohexanecarboximidate
(3l, C19H19Cl2NO)
Colorless solid; yield 278 mg (80%); m.p.: 49–53 °C;
ꢀ
Rf = 0.53; IR (KBr): m ¼ 3;076; 2;930; 2;855; 1;685;
123

460
M. Ghandi et al.
1;590; 1;461; 1;220 cm-1
;
1H NMR (500 MHz, CDCl3):
(s, 1H, Ar-H), 7.17 (t, J = 7.8 Hz, 1H, Ar-H), 7.39 (d,
J = 7.8 Hz, 1H, Ar-H), 7.47-8.17 (m, 4H, Ar-H) ppm; 13C
NMR (125 MHz, CDCl3): d = 21.0, 28.7, 40.0, 112.5,
121.1, 122.2, 122.9, 123.2, 125.5, 125.8, 126.5, 128.0,
129.0, 132.6, 134.9, 144.5, 150.4, 162.6 ppm; EI-MS:
m/z (%) = 317 (M?, 12), 174 (100), 118 (93), 91 (19), 57
(16).
d = 1.17–1.32 (3H, m, cyclohexane), 1.71-1.98 (7H, m,
cyclohexane), 2.57 (1H, tt, J = 11.2, 3.4 Hz, cyclohex-
ane), 6.77 (2H, d, J = 7.6 Hz, Ar-H), 7.08 (1H, t,
J = 7.4 Hz, Ar-H), 7.19 (1H, d, J = 8.6 Hz, Ar-H), 7.29-
7.33 (3H, m, Ar-H), 7.49 (1H, d, J = 2.3 Hz, Ar-H) ppm;
13C NMR (125 MHz, CDCl3): d = 25.9, 26.1, 30.1, 39.4,
121.0, 123.54, 125.1, 125.6, 128.3, 129.4, 130.5, 131.3,
147.9, 148.5, 165.3 ppm; EI-MS: m/z (%) = 351 (M?, 10),
348 (13), 214 (7), 186 (100), 111 (16), 104 (78), 83 (38).
Naphthalen-2-yl N-(4-methoxyphenyl)pivalimidate
(10, C22H23NO2)
White crystals; yield 313 mg (94%); m.p.: 64–65 °C; IR
ꢀ
4-tert-Butylphenyl N-(4-methylphenyl)benzimidate
(3m, C24H25NO)
(KBr): m ¼ 3;252; 3;054; 2;969; 1;672; 1;503; 1;242; 1;080
cm-1
;
1H NMR (500 MHz, CDCl3): d = 1.47 (s, 9H,
Orange solid; yield 213 mg (62%); m.p.: 62–65 °C;
t-Bu), 3.57 (s, 3H, OMe), 6.55 (d, J = 8.3 Hz, 2H, Ar-H),
6.82 (d, J = 8.3 Hz, 2H, Ar-H), 7.02 (bd, J = 8.6 Hz, 1H,
Ar-H), 7.10 (bs, 1H, Ar-H), 7.30–7.71 (m, 5H, Ar-H) ppm;
13C NMR (125 MHz, CDCl3): d = 28.5, 39.7, 55.7, 114.0,
118.9, 121.4, 123.1, 124.7, 126.7, 127.3, 127.4, 128.0,
129.5, 130.1, 134.3, 139.6, 152.7, 156.1 ppm; EI-MS:
m/z (%) = 333 (M?, 8), 190 (100), 134 (87), 115 (12), 77
(7), 57 (22).
ꢀ
Rf = 0.63; IR (KBr): m ¼ 3;078; 2;962; 1;661; 1;500;
1;267; 1;206; 1;079 cm-1
;
1H NMR (500 MHz, CDCl3):
d = 1.36 (9H, s, t-Bu), 2.33 (3H, s, Me), 6.77-7.45 (10H,
m, Ar-H), 7.52 (1H, d, J = 8.7 Hz, Ar-H), 7.58 (1H, t,
J = 7.7 Hz, Ar-H), 8.03 (1H, bs, Ar-H) ppm; 13C NMR
(125 MHz, CDCl3): d = 21.3, 31.9, 34.9, 117.2, 121.5,
121.7, 122.7, 126.7, 126.9, 128.7, 129.7, 130.2, 130.6,
133.9, 149.1, 165.8 ppm; EI-MS: m/z (%) = 343 (M?, 6),
348 (13), 254 (15), 214 (85), 194 (100), 105 (82), 91 (30),
77 (31).
Acknowledgments The authors acknowledge the University of
Tehran for financial support of this research.
4-tert-Butylphenyl N-4-(chlorophenyl)benzimidate
(3n, C23H22ClNO)
References
Yellow solid; yield 211 mg (58%); m.p.: 59–63 °C;
1. Chapman AW (1925) J Chem Soc 127:1992
2. Dauben WG, Hodgson RL (1950) J Am Chem Soc 72:3479
3. Schulenberg JW, Archer S (1965) Org React 14:151
4. Oxley S (1948) J Chem Soc 1514
ꢀ
Rf = 0.60; IR (KBr): m ¼ 3;080; 2;960; 2;888; 1;651;
1;495; 1;265; 1;209 cm-1
;
1H NMR (500 MHz, CDCl3):
d = 1.36 (9H, s, t-Bu), 6.75-7.51 (10H, m, Ar-H), 7.52
(1H, d, J = 8.7 Hz, Ar-H), 7.58 (1H, t, J = 7.8 Hz, Ar-H),
8.04 (1H, bs, Ar-H) ppm; 13C NMR (125 MHz, CDCl3):
d = 31.9, 34.7, 120.3, 121.5, 123.6, 126.2, 126.8, 126.9,
128.8, 129.0, 129.2, 129.9, 130.2, 130.6, 139.0 ppm;
EI-MS: m/z (%) = 363 (M?, 6), 348 (13), 254 (10), 216
(43), 214 (100), 105 (55), 77 (18).
5. Titus PE, Forte PA, Prokipack JM (1976) Can J Chem 54:647
6. Sechaud J (1956) Helv Chim Acta 39:1257
7. Chapman AW (1927) J Chem Soc 1748
8. Wheeler OH, Roman F, Santiago MV, Pages FQ (1969) Can J
Chem 47:503
9. Schenck TG, Bosnich B (1985) J Am Chem Soc 107:2058
10. Kantlehner W (1991) In: Trost BM, Fleming I (eds), Compre-
hensive organic synthesis, vol 6. Pergamon, New York, p 485
11. Manley PJ, Bilodeau MT (2002) Org Lett 4:3127
12. Gordon J, Turrell G (1959) J Org Chem 24:269
13. Zielinski W, Kudelko A (2000) Monatsh Chem 131:895
14. Meerwein H, Laasch P, Mersch R, Nentwig J (1956) Chem Ber
89:224
15. Charette AB, Grenon M (2000) Tetrahedron Lett 41:1677
16. Charette AB, Chua P (1998) J Org Chem 63:908
17. Charette AB, Chua P (1998) Tetrahedron Lett 39:245
18. Charette AB, Chua P (1998) Synlett 163
19. Charette AB, Chua P (1997) Tetrahedron Lett 38:8499
20. Sforza F, Dossena M, Corradini M, Virgili E, Marchelli R (1998)
Tetrahedron Lett 39:711
21. Movassaghi M, Hill MD (2006) J Am Chem Soc 128:14254
22. Movassaghi M, Hill MD, Ahmad OK (2007) J Am Chem Soc
129:10096
23. Movassaghi M, Hill MD (2008) Org Lett 10:3485
24. Movassaghi M, Hill MD (2007) Nat Protoc 2:2018
25. Medley JW, Movassaghi M (2009) J Org Chem 74:1341
26. Hendrickson JB, Schwartzman SM (1975) Tetrahedron Lett
16:277
Phenyl N-(4-methoxyphenyl)benzimidate
(3o, C20H17NO2)
Yellow solid; yield 197 mg (65%); m.p.: 66–67 °C; Rf =
ꢀ
0.64; IR (KBr): m ¼ 3;071; 2;964; 1;651; 1;589; 1;487;
1;203; 1;017 cm-1
;
1H NMR (500 MHz, CDCl3):
d = 3.80 (3H, s, OMe), 6.73–8.11 (14H, m, Ar-H) ppm;
13C NMR (125 MHz, CDCl3): d = 55.8, 114.4, 115.0,
117.4, 122.7, 123.2, 124.8, 125.2, 128.9, 129.1, 129.5,
130.1, 131.5, 133.6 ppm; EI-MS: m/z (%) = 303 (M?, 8),
210 (100), 107 (17), 105 (81), 77 (30).
Naphthalen-1-yl N-(4-methylphenyl)pivalimidate
(9, C22H23NO)
White crystals; yield 279 mg (88%); m.p.: 59–60 °C;
Rf = 0.72; IR (KBr): ꢀm ¼ 3;056; 2;972; 2;868; 1;666; 1;463;
1;207; 1;077 cm-1; 1H NMR (500 MHz, CDCl3): d = 1.51
(s, 9H, t-Bu), 2.05 (s, 3H, Me), 6.68 (bs, 4H, Ar-H), 6.78
123