High-yielding synthesis of Weinreb amides via homogeneous catalytic carbonylation of iodoalkenes and iodoarenes

Article abstract of DOI:10.1016/j.tet.2010.04.076

Iodoarenes (iodobenzene and 2-iodothiophene) and iodoalkenes (1-iodocyclohexene, 1-iodo-4-tert-butylcyclohexene, 1-iodo-2-methylcyclohexene and 1-iodo-1-(1-naphthyl)ethene) were used as substrates in palladium-catalysed aminocarbonylation with N,O-dimethylhydroxylamine. The corresponding Weinreb amides were prepared in high isolated yields (up to 87%) when forcing conditions (40-60 bar of CO, 50 °C) were used. The aminocarbonylation provides the Weinreb amides as pure products in a chemoselective reaction. No formation of ketocarboxamides, due to double CO insertion, except for 2-iodothiophene, was observed even at 60 bar of CO pressure.

Full text of DOI:10.1016/j.tet.2010.04.076

Tetrahedron 66 (2010) 4479e4483
Contents lists available at ScienceDirect
Tetrahedron
journal homepage: www.elsevier.com/locate/tet
High-yielding synthesis of Weinreb amides via homogeneous catalytic
carbonylation of iodoalkenes and iodoarenes
*
Attila Takács, Andrea Petz, László Kollár
Department of Inorganic Chemistry, University of Pécs, H-7624 Pécs, PO Box 266, Hungary
a r t i c l e i n f o
a b s t r a c t
Article history:
Iodoarenes (iodobenzene and 2-iodothiophene) and iodoalkenes (1-iodocyclohexene, 1-iodo-4-tert-
butylcyclohexene, 1-iodo-2-methylcyclohexene and 1-iodo-1-(1-naphthyl)ethene) were used as sub-
strates in palladium-catalysed aminocarbonylation with N,O-dimethylhydroxylamine. The corre-
sponding Weinreb amides were prepared in high isolated yields (up to 87%) when forcing conditions
(40e60 bar of CO, 50 ꢀC) were used. The aminocarbonylation provides the Weinreb amides as pure
products in a chemoselective reaction. No formation of ketocarboxamides, due to double CO insertion,
except for 2-iodothiophene, was observed even at 60 bar of CO pressure.
Received 27 January 2010
Received in revised form 13 April 2010
Accepted 19 April 2010
Available online 24 April 2010
Keywords:
Aminocarbonylation
Carbon monoxide
Weinreb amide
Palladium
Ó 2010 Elsevier Ltd. All rights reserved.
Iodoalkene
1. Introduction
laboratory as a powerful tool for the functionalization of the tro-
pene8 and steroidal skeletons.9,10
Weinreb amides (N-methoxy-N-methyl amides), easily available
from the corresponding acids or esters, represent an important
family of acylating agents.1 Their synthetic utility is due to the facile
reaction with various organometallic reagents providing building
blocks of versatile structure.2 Their two major synthetic features,
that is, the excellent acylating agent property towards organo-
lithium or organomagnesium reagents and the synthetic equiva-
lency for an aldehyde group has been reviewed recently.3
A great variety of amides are available via palladium-catalysed
aminocarbonylation. The synthetic applicability of these catalytic
reactions is due to the ease in structural variation of amides both on
the amide nitrogen and on the carboxylic acid moieties. That is,
instead of the conventional carboxylic aciddacyl chloridedamide
route a direct carbonylation of haloaromatics or haloalkenes
(preferably iodo derivatives) as well as those of the corresponding
triflate surrogates can be used.4e7 It is worth mentioning that
aminocarbonylation has shown high tolerancy towards both the
structure of the primary and secondary amine and that of the or-
ganic halide derivative. The efficacy of these reactions can also be
demonstrated both by the synthesis of the great variety of simple
model compounds and by the functionalization of biologically
important skeletons.7 This methodology has been used also in our
Although several straightforward synthetic methods, such as
conversion of acid chlorides,11,12 esters13,14 and carboxylic acids15
towards Weinreb amides are known, only sporadic results on
their facile homogeneous catalytic synthesis, based on the use of
simple building blocks, have been reported.16e18 Recently, a gen-
eral palladium-catalysed carbonylation for the conversion of aryl
bromides to benzamide-type Weinreb amides17 and that of the
lactam-, lactone- and thiolactone-derived triflates into the corre-
sponding heterocyclic Weinreb amides have been published.18 To
the best of our knowledge, they have been the only examples
involving the application of N,O-dimethylhydroxylamine in cata-
lytic aminocarbonylation. Due to the reduced reactivity of this
N-nucleophile, from the variety of bidentate ligands tested, the
application of a diphosphine with rigid structure and a large bite
angle (Xantphos) was necessary to achieve yields of practical
interest.17
Guided by our earlier experience that iodoalkenes and iodoar-
enes can smoothly be converted to the corresponding amides by
using even hindered secondary amines and functionalised amines
such as amino acid esters, we decided to investigate the catalytic
synthesis of Weinreb amides based on the application of iodo de-
rivatives as substrates and N,O-dimethylhydroxylamine as N-nu-
cleophile. Accordingly,
methodology is reported here for the direct synthesis of aryl and
-unsaturated N-methoxy-N-methyl amides (i.e., aryl and un-
saturated Weinreb amides).
a
clean and quantitative synthetic
a
,
b
* Corresponding author. E-mail address: kollar@ttk.pte.hu (L. Kollár).
0040-4020/$ e see front matter Ó 2010 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2010.04.076

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A. Takács et al. / Tetrahedron 66 (2010) 4479e4483
Table 1
2. Results and discussion
Palladium-catalysed aminocarbonylation of 1e6 and 10 with N,O-dimethylhydrox-
ylamine as N-nucleophilea
The iodoaromatics (iodobenzene, 1 and 2-iodothiophene, 2) and
iodoalkenes (1-iodocyclohexene, 3, 1-iodo-4-tert-butylcyclohex-
ene, 4, 1-iodo-2-methylcyclohexene, 5 and 1-iodo-1-(1-naphthyl)
ethene, 6) were reacted with N,O-dimethylhydroxylamine at 1 bar
of CO in the presence of in situ generated palladium(0)-triphenyl-
phosphine catalysts (Scheme 1). The palladium(0) complexes, able
to activate both iodoarenes and iodoalkenes, were prepared in situ
from palladium(II) acetate as described previously in detail.19,20
All the iodoaromatics and iodoalkenes above have shown lower
reactivity towards N,O-dimethylhydroxylamine than towards the
generally used primary and secondary amines as N-nucleophiles.7
No reaction was observed with iodoaromatics at atmospheric CO
pressure. In order to achieve higher (practically complete) con-
version in a reasonable reaction time, higher CO pressure (60 bar)
was necessary. Interestingly, while the aminocarbonylation of
iodobenzene (1) is highly chemoselective yielding the expected
Weinreb amide (1a) only, the application of 2-iodothiophene (2) as
substrate resulted in the formation of both expected products, the
corresponding amide (2a) and ketoamide (2b) due to simple and
double CO insertion, respectively. It has to be added that 2b was
formed as a minor product (up to 8%) under all reaction conditions
used.
Entry
Subst.
p(CO) [bar]
R. time [h]
Conv.b [%]
Isolated yieldc
(amide) [%]
1
2
3
4
5
6
7
8
1
1
2
2
3
3
4
4
5
5
6
6
10
1
60
1
60
1
40
1
40
1
60
1
60
60
20
20
20
110
20
85
20
20
20
72
20
20
72
0
95
0
>98
60
>98
20
>98
25
>98
>98
>98
>98
d
82 (1a)
d
67 (2a), n.d.d (2b)
48 (3a)
77 (3a)
n.d. (4a)
87 (4a)
n.d. (5a)
85 (5a)
83 (6a)
86 (6a)
n.d. (11); 55 (12)
9
10
11
12
13
a
Reaction conditions: 0.025 mmol Pd(OAc)2; 0.05 mmol PPh3, 1 mmol substrate
(1e6, 10); 1.1 mmol N,O-dimethylhydroxylamine hydrochloride; 10 mL DMF.
b
Determined by GC/MS.
Based on the amount of the substrate used (1e6, 10).
n.d.¼not determined (i.e., the target compound was not isolated as a pure
c
d
substance).
featured by the highest reactivity among iodoalkenes also towards
N,O-dimethylhydroxylamine, as observed previously in conven-
tional palladium-catalysed aminocarbonylations.21 The increase in
the CO pressure resulted in practically complete conversions to-
wards the expected Weinreb amides (3ae6a). The reaction is
Contrary to iodoarenes, iodoalkenes (3e5) react even at atmo-
spheric CO pressure with conversion of 60%, 20% and 25%, re-
spectively (Table 1). The 1-iodo-1-aryl-ethene type substrate (6) is
OMe
I
O
N
Me
1
1a
O
Me
OMe
2
N
N
Me
I
OMe
S
S
2b
S
O
O
2a
OMe
N
O
O
I
Me
3a
3
+
CO HNMe(OMe)
Pd(OAc)2 / PPh3
OMe
N
I
Me
4
4a
OMe
N
O
I
Me
5a
5
Me
OMe
O
N
I
6
6a
Scheme 1. Palladium-catalysed aminocarbonylation of iodoarenes (1,2) and iodoalkenes (3e6) with N,O-dimethylhydroxylamine.

A. Takács et al. / Tetrahedron 66 (2010) 4479e4483
4481
completely chemoselective providing the expected N-methoxy-N-
methyl carboxamide as the only product in all cases. It has been
reported, that palladium(0)-catalysed aminocarbonylation is gen-
erally a highly selective reaction regarding the transformation of
the wide variety of substrates (triflates or iodo derivatives).4,7
However, the amine nucleophile, used commonly in excess, is
carbonylated to N,N0-dialkyl- or N,N,N0,N0-tetraalkylurea derivatives
(and, in less amount, to the corresponding glyoxylamides). During
this study, the carbonylation of the N,O-dimethylhydroxylamine
nucleophile did not take place (Scheme 2), so no nucleophile was
lost in the form of a urea-type derivative and a more facile isolation
technique could be used.
that the application of flame-dried apparatus decreased the
amount of 11 drastically. The bis(palladium-acyl) intermediate,
obtained from 10 by double oxidative addition followed by CO in-
sertion, could form 11 by hydrolysis or 12 by reacting with N,O-
dimethylhydroxylamine. To the best of our knowledge, the appli-
cation of N,O-dimethylhydroxylamine as a methylamine source
(‘masked methylamine’) in catalysis is unprecedented.
CH3
O
O
O
O
N
O
I
I
CO HNMe(OMe) / H O
+
2
+
O
O
R1
N
Pd(OAc)2 / PPh3
R1
R2
R1
R1
R1
+
CO 2 H
N
+
N
N
N
R2
R2
10
11
12
R2 R2
O
Pd(OAc)2 / PPh3
Scheme 3. The carbonylation reactions of 1,8-diiodonaphthalene.
R1, R2 = H, alkyl, aryl
O
A simplified reaction mechanism of the aminocarbonylation of
an iodoalkene with N,O-dimethylhydroxylamine towards the cor-
responding Weinreb amide is shown on Scheme 4. The oxidative
addition of the iodoalkene substrate on palladium(0) complex (A),
formed in situ from palladium(II) acetate and PPh3 (vide supra),
takes place. The resulted palladium(II)-alkenyl intermediate (B)
activates CO yielding the terminal carbonyl complex (C). The mi-
gratory insertion of CO into the palladiumealkenyl bond provides
the acyl intermediate (D), which undergoes reductive elimination in
the presence of a base (triethylamine) and N,O-dimethylhydroxyl-
amine in the product-forming step, while the catalytically active,
coordinatively unsaturated palladium(0) complex is re-formed.
OMe
Me
Me
Me
N
N
CO 2 H-N
+
MeO
OMe
Pd(OAc)2 / PPh3
Scheme 2. Palladium-catalysed carbonylation of N-nucleophiles as a side-reaction.
It is worth noting, that phosphine/palladium ratio as low as 2/1
has to be used. In this way, one equivalent of triphenylphosphine
acts as a reducing agent in the reduction of palladium(II) to palla-
dium(0) while it is oxidised to triphenylphoshine oxide. The other
PPh3 coordinates to Pd(0) resulting in coordinatively highly un-
saturated reactive species.19,20 In this way, an easy to handle, cheap,
highly active palladium(0)-triphenylphosphine in situ system of
synthetic interest was obtained.
Due to the highly polarizable iodo-substituent, conversions of
practical interest have been achieved with all substrates. Further-
more, the application of iodoalkenes/iodoarenes as enol-triflate/
aryltriflate surrogates leads to reaction mixtures, which could be
worked-up by simple methods. Consequently, the Weinreb amides
were isolated in high yields.
OMe
Me
N
I
O
Et3NHI
PdL
OMe
n
Me
N
A
Compared the above results with those obtained previously
with primary and secondary amines as N-nucleophiles,21,22 it could
be stated that N,O-dimethylhydroxylamine shows much lower re-
activity. Therefore more severe reaction conditions had to be used.
However, it has been revealed by detailed GC/MS analyses that in
case of 6 high conversions have been obtained even after a short
reaction time. The aminocarbonylation of this highly reactive sub-
strate towards 6a at atmospheric CO pressure resulted in 21%, 43%,
56%, 84%, 95% and 99% conversions in 15 min, 30 min, 1 h, 2 h, 3 h
and 5 h, respectively. In this way, high conversions can be obtained
in 20 h (Table 1), enabling the facile isolation of the exclusive amide
product.
H
Et3N
PdIL
n-2
PdIL
CO
O
n-2
D
B
PdI(CO)L
n-2
As for the limitations of the iodoaromatics-based catalytic
synthesis of Weinreb amides, it should be added, that 2-iodopyr-
idine (7) and its ortho-hydroxy-substituted derivative, 3-hydroxy-
2-iodo-6-methylpyridine (8), as well as 2-iodo-imidazole (9)
proved to be unreactive under the conditions used above. Neither
the corresponding carboxamides, the only products in the amino-
carbonylation of 7 with primary and secondary amines,21 nor the
ketocarboxamides were formed.
C
Scheme 4. A simplified reaction mechanism for the aminocarbonylation of an iodoalkene
with N,O-dimethylhydroxylamine.
3. Conclusion
We have found that various types of iodoalkenes and iodoar-
omatics show good reactivity in the palladium-catalysed
aminocarbonylation using N,O-dimethylhydroxylamine as the N-
nucleophile. A clean and quantitative catalytic synthetic method-
ology was developed for the direct synthesis of the corresponding
N-methoxy-N-methyl amides, i.e., for that of aryl and unsaturated
Weinreb amides. It is worthy of note that even the most simple and
An unexpected reaction was observed with 1,8-diiodonaph-
thalene (10). The mixture of two products, that of N-methyl-1,8-
naphthalimide (12) and naphthalene-1,8-dicarboxylic anhydride
(11) was obtained in a ratio of ca. 80/20 (Scheme 3). The formation
of 11 can be explained by the low reactivity of the nucleophile and
the presence of traces of water in the solvent (and even the
adsorbed water on the wall of the glass flask). It should be noted

4482
A. Takács et al. / Tetrahedron 66 (2010) 4479e4483
easily available palladium-triphenylphosphine in situ catalyst
proved to be active under relatively mild reaction conditions. In this
way, a high-yielding, simple method for the synthesis of these
widely used synthetic building blocks is provided.
3.35 (s, 3H, NCH3). dC (100.6 MHz, CDCl3) 170.0; 134.2; 130.5; 128.1;
128.0; 61.0; 33.8. IR (KBr, (cmꢂ1)): 1648 (CON). MS m/z (rel int. %):
165 (3), 105 (100), 77 (52), 51 (15). Anal. Calcd for C9H11NO2
(165.19): C, 65.44; H, 6.71; N, 8.48; found: C, 65.32, H, 6.86; N, 8.23;
Rf (10% EtOAc/CHCl3) 0.63; pale yellow oil.
4. Experimental
4.4.2. N-Methyl-N-methoxy-thiophene-2-carboxamide
(2a). dH
4.1. General procedures
(400 MHz, CDCl3) 7.95 (d, 3.7 Hz, 1H, Tioph); 7.55 (d, 4.9 Hz, 1H,
Tioph); 7.12 (d, 3.7 Hz, 4.9 Hz,1H, Tioph); 3.79 (s, 3H, OCH3); 3.40 (s,
3H, NCH3). dC (100.6 MHz, CDCl3) 162.3; 135.8; 134.4; 132.2; 126.8;
61.5; 33.1. IR (KBr, (cmꢂ1)): 1655 (CON). MS m/z (rel int. %): 171 (6),
111 (100), 83 (10), 57 (2). Anal. Calcd for C7H9NO2S (171.21): C,
49.11; H, 5.30; N, 8.18; found: C, 49.02, H, 5.45; N, 8.01; Rf (10%
EtOAc/CHCl3) 0.56; yellow oil.
1H and 13C NMR spectra were recorded in CDCl3 on a Varian
Inova 400 spectrometer at 400.13 MHz and 100.62 MHz, re-
spectively. Chemical shifts
d are reported in parts per million rela-
tive to residual CHCl3 (7.26 and 77.00 ppm for 1H and 13C,
respectively). Elemental analyses were measured on a 1108 Carlo
Erba apparatus. Samples of the catalytic reactions were analysed
with a Hewlett Packard 5830A gas chromatograph fitted with
a capillary column coated with OV-1.
4.4.3. N-Methyl-N-methoxy-cyclohex-1-enecarboxamide
(3a). dH
(400 MHz, CDCl3) 6.14 (br s, 1H, ]CH); 3.62 (s, 3H, OCH3); 3.21 (s,
3H, NCH3); 2.2e2.26 (m, 2H, CH2); 2.08e2.14 (m, 2H, CH2);
1.58e1.70 (m, 4H, 2ꢁCH2). dC (100.6 MHz, CDCl3) 172.0; 133.9;
131.0; 61.0; 33.7; 25.6; 25.0; 22.2; 21.7. IR (KBr, (cmꢂ1)): 1655
(CON); ca. 1620 (sh, C]C). MS m/z (rel int. %): 169 (2), 109 (100), 81
(70), 79 (45), 53 (16). Anal. Calcd for C9H15NO2 (169.22): C, 63.88; H,
8.93; N, 8.28; found: C, 63.70, H, 8.85; N, 8.03; Rf (10% EtOAc/CHCl3)
0.54; yellow oil.
The N,O-dimethylhydroxylamine and the iodoaromatics were
purchased from Aldrich. The iodoalkenes (1-iodocyclohexene,23 1-
iodo-4-tert-butylcyclohexene,23
and 1-iodo-1-(1-naphthyl)ethane22
scribed before.
1-iodo-2-methylcyclohexene23
)
were synthesised as de-
4.2. Aminocarbonylation experiments at normal pressure
In typical experiment solution of Pd(OAc)2 (5.6 mg,
a
a
4.4.4. N-Methyl-N-methoxy-4-tert-butyl-cyclohex-1-enecarbox-
amide (4a). dH (400 MHz, CDCl3) 6.19e6.22 (m, 1H, ]CH); 3.63 (s,
3H, OCH3); 3.21 (s, 3H, NCH3); 2.15e2.40 (m, 3H, CHtBuþ ]CHCH2);
1.80e1.96 (m, 2H, CH2); 1.10e1.35 (m, 2H, CH2). dC (100.6 MHz,
CDCl3) 171.9; 133.6; 131.8; 61.0; 43.5; 33.7; 32.2, 27.2; 27.1, 26.9;
23.7. IR (KBr, (cmꢂ1)): 1659 (CON); 1632 (C]C). MS m/z (rel int. %):
225 (2), 210 (4), 165 (100), 95 (20), 81 (31), 57 (38). Anal. Calcd for
C13H23NO2 (225.33): C, 69.29; H, 10.29; N, 6.22; found: C, 69.10, H,
10.45; N, 6.03; Rf (10% EtOAc/CHCl3) 0.65; yellow oil.
0.025 mmol), PPh3 (13.1 mg, 0.05 mmol), 1.0 mmol iodo substrate
(1e9), 1.1 mmol N,O-dimethylhydroxylamine hydrochloride
(107.3 mg, 1.1 mmol) were dissolved in 10 mL of DMF under argon.
Triethylamine (0.5 mL) was added to the homogeneous yellow
solution and the atmosphere was changed to CO. The colour
changed to dark red. The reaction was conducted for the given
reaction time at 50 ꢀC. Some metallic palladium was formed at the
end of the reaction, which was filtered off. A sample of this solution
was immediately analysed by GC/MS. The mixture was then con-
centrated to dryness. The residue was dissolved in chloroform
(20 mL) and washed with water (20 mL). The organic phase was
thoroughly washed with 5% HCl (2ꢁ20 mL), saturated NaHCO3
(20 mL), brine (20 mL), dried over Na2SO4 and concentrated to
a yellow waxy material or a thick oil. Chromatography (silica,
chloroform, then chloroform/ethyl acetate mixtures) afforded the
desired compounds typically as pale brown viscous materials or
yellow solids.
4.4.5. N-Methyl-N-methoxy-2-methyl-cyclohex-1-enecarboxamide
(5a). dH (400 MHz, CDCl3) 3.63 (s, 3H, OCH3); 3.21 (s, 3H, NCH3);
1.25e2.20 (m, 8H, 4ꢁCH2); 1.62 (s, 3H, ]CCH3). dC (100.6 MHz,
CDCl3) 171.6; 139.1; 129.6; 60.9; 33.9; 30.9; 30.5; 30.0; 25.2; 20.0. IR
(KBr, (cmꢂ1)): 1641 (CON). MS m/z (rel int. %): 183 (2), 123 (100), 95
(61), 67 (33). Anal. Calcd for C10H17NO2 (183.25): C, 65.54; H, 9.35;
N, 7.64; found: C, 65.37, H, 9.51; N, 7.50; Rf (20% EtOAc/CHCl3) 0.56;
pale yellow oil.
The synthesis of compounds 1a,14,15,24 2a,25,26 3a18 and 1227 by
conventional methods have been previously reported. Our analyt-
ical data below are in good agreement with the reported values.
Due to some minor differences in the analytical data (e.g., coupling
constants) full characterization are given here also for these
compounds.
4.4.6. N-Methyl-N-methoxy-2-(1-naphthyl)acrylamide (6a). dH (400
MHz, CDCl3) 8.12 (d, 7.8 Hz, 1H, Naph); 7.77e7.85 (m, 2H, Naph);
7.40e7.51 (m, 5H, Naph); 6.11 (s, 1H, ]CH); 5.65 (s, 1H, ]CH); 3.10
(s, 3H, OCH3); 2.93 (s, 3H, NCH3). dC (100.6 MHz, CDCl3) 171.3; 144.6;
136.2; 133.6; 131.1; 128.3; 128.2; 126.4; 125.9 (double intensity);
125.3; 125.2; 123.9; 60.3; 33.1. IR (KBr, (cmꢂ1)): 1656 (CON). MS m/z
(rel int. %): 241 (11), 181 (10), 153 (100), 76 (5). Anal. Calcd for
C15H15NO2 (241.29): C, 74.67; H, 6.27; N, 5.80; found: C, 74.50, H, 6.45;
N, 5.66; Rf (10% EtOAc/CHCl3) 0.75; yellow viscous material.
4.3. Aminocarbonylation experiments at high pressure
A mixture of 1 (or 2e9) (1 mmol), palladium(II) acetate (5.6 mg,
0.025 mmol) and PPh3 (13.1 mg, 0.05 mmol) was dissolved in 10 mL
of DMF under argon, and NEt3 (0.5 mL) and N,O-dimethylhydrox-
ylamine hydrochloride (107.3 mg, 1.1 mmol) as N-nucleophile was
added. The reaction mixture was then transferred under argon into
a 100 mL stainless steel autoclave, which was pressurized to 60 bar
with CO and the magnetically stirred mixture was heated in an oil
bath at 50 ꢀC for the reaction time given in Table 1. The work-up
procedure was identical with that given above.
4.4.7. N-Methyl-N-methoxy-thiophen-2-yl-glyoxylamide (2b). dH (400
MHz, CDCl3) 8.41 (d, 3.6 Hz,1H, Tioph); 7.79 (d, 4.8 Hz, 1H, Tioph); 7.18
(dd, 3.6 Hz, 4.8 Hz, 1H, Tioph); 3.72 (s, 3H, OCH3); 3.35 (s, 3H, NCH3).
dC (100.6 MHz, CDCl3) 178.4; 166.4; 135.9; 135.8; 133.3; 128.5; 62.3;
31.7. MS m/z (rel int. %): 199 (1), 111 (100), 83 (10), 57 (5). Compound
2b could not be isolated as pure compound. The above data were
obtained from a mixture of 2a/2b¼3/1.
4.4. Characterization of the amide and ester products
4.4.8. N-Methyl-1,8-naphthalimide (12). 1H NMR(CDCl3)
7.3 Hz, 2H, Naph); 8.21 (d, 8.3 Hz, 2H; Naph); 7.77 (dd, 7.3 Hz, 8.3 Hz,
2H, Naph); 3.57 (s, 3H, NCH3).13C NMR (CDCl3)
: 163.1; 133.9; 132.5;
d: 8.60 (d,
4.4.1. N-Methyl-N-methoxy-benzamide (1a). dH (400 MHz, CDCl3)
7.66 (d, 8.0 Hz, 2H, Ph); 7.38e7.50 (m, 3H, Ph); 3.57 (s, 3H, OCH3);
d

A. Takács et al. / Tetrahedron 66 (2010) 4479e4483
4483
132.0; 129.8; 125.5; 121.1; 37.2. IR (KBr, (cmꢂ1)): 1771,1736 (OCNCO).
MS m/z (relint. %): 211 (60),198 (24),183 (12),167(93),166 (100),154
(49), 139 (17), 126 (73). Anal. Calcd. for C13H9NO2 (211.22): C, 73.92;
H, 4.29; N, 6.63; found: C, 73.74; H, 4.49; N, 6.40; Rf (10% EtOAc/
CHCl3) 0.73; white solid, mp 200e201 ꢀC.
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Acknowledgements
ꢀ
1723e1725.
The authors thank the Hungarian Research Fund (OTKA
CK78553), the Joint Project of the European UniondHungarian
National Development Program (GVOP-3.2.1-2004-04-0168/3) and
Science, Please! Research Team on Innovation (SROP-4.2.2./08/1/
2008-0011) for the financial support and Johnson Matthey for the
generous gift of palladium(II) acetate.
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bowski, E. J. J. Tetrahedron Lett. 1995, 36, 5461e5464.
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