Condensation of aromatic aldehydes with VyV-dimethylacetamide in presence of dialkyl carbonates as dehydrating agents

Article abstract of DOI:10.1007/s00706-009-0248-x

Reactions of benzaldehydes with excess N,N- dimethylacetamide at 140 °C in the presence of diethyl carbonate as dehydrating agent and a base gave (E)-N,N- dimethylcinnamamides in good yields. If hydroxybenzal- dehydes are used as substrates the reaction is accompanied by alkylation. Springer-Verlag 2010.

Full text of DOI:10.1007/s00706-009-0248-x

Monatsh Chem (2010) 141:205–211
DOI 10.1007/s00706-009-0248-x
ORIGINAL PAPER
Condensation of aromatic aldehydes with N,N-dimethylacetamide
in presence of dialkyl carbonates as dehydrating agents
•
Tomas Weidlich Lubomır Prokes
•
´ˇ
Ales Ruzicka Zdenka Padelkova
´
ˇ
•
ˇ
˚ ˇ ˇ
ˇ
ˇ
´
Received: 14 August 2009 / Accepted: 23 December 2009 / Published online: 27 January 2010
Ó Springer-Verlag 2010
Abstract Reactions of benzaldehydes with excess N,N-
dimethylacetamide at 140 °C in the presence of diethyl
carbonate as dehydrating agent and a base gave (E)-N,N-
dimethylcinnamamides in good yields. If hydroxybenzal-
dehydes are used as substrates the reaction is accompanied
by alkylation.
Alkoxycinnamamides 2 have been patented as UV
absorbers for cosmetics [9] and as anti-allergic agents [10].
N,N-Dimethylcinnamamides are generally available via
the reactions of cinnamic acids [11], benzaldehydes
[12–18], halogenobenzenes [19, 20], styrenes [21], aryl-
acetylenes [22], benzylalcohols [23], and 2-chloro-3-
hydroxyamides [24]. However, each of the published
syntheses of N,N-dimethylcinnamamides [11–24] has some
disadvantages. Sometimes mixtures of (E) and (Z) stereo-
isomers of cinnamamides have been formed [17, 19, 21].
Stoichiometric amounts of by-products [11, 13, 18, 20–24]
were produced in some of the above mentioned synthetic
procedures. Palladium catalysts are well known for their
high activity for the coupling reaction of arylhalides with
unsaturated compounds, for example acrylamides [19, 20].
However, application of homogeneous catalysis causes
major problems in purification of products and separation
of the expensive heavy metal catalyst, and leads to toxic
waste. These problems are of environmental and economic
concern in large-scale synthesis.
Keywords C–C bond formation ꢀ Aldol-type reaction ꢀ
Alkylation ꢀ AOX removal ꢀ Al–Ni alloy
Introduction
b-Arylacrylamides (cinnamamides) are common in syn-
thetic chemistry. The cinnamamides have been used as
building blocks for cyclopentanone [1], for synthesis of
chiral 3-substituted-4-ketoamides [2], a,b-epoxy amides
[3], alcohols [4, 5], and as monomers for special polymeric
materials [6]. Some derivatives of cinnamamides have
antiestrogenic activity [7]. N,N-dimethylcinnamamides
serve as intermediates for ligand synthesis [8].
Formation of 2 by condensation of aldehydes 1 with
N,N-dimethylacetamide (DMA) was described as an
undesirable reaction during Suzuki coupling of phenylbo-
ronic acid with 4-chlorobenzaldehyde dissolved in DMA at
130–150 °C in the presence of Pd(OAc)2, n-Bu4NBr, and
K3PO4 [25].
T. Weidlich (&)
Institute of Environmental and Chemical Engineering,
Faculty of Chemical Technology, University of Pardubice,
Studentska 573, 53210 Pardubice, Czech Republic
e-mail: tomas.weidlich@upce.cz
Dialkylcarbonates (RO)2CO are well known as solvents
and alkylating compounds with low toxicity (similar to the
corresponding alcohols) [26], which could be produced
from renewable sources [26]. To the best of our knowl-
edge, application of (RO)2CO as dehydrating agents has
been mentioned in a few cases of ring-closure reactions
only [27, 28] although (RO)2CO are ideal for use at high
temperatures because of their ability to react smoothly with
water in the presence of base or acid [29].
ˇ
L. Prokes
Department of Chemistry, Faculty of Science,
Masaryk University, Kotlarska 2, 61137 Brno,
Czech Republic
ˇ
ˇ
´
˚ˇ
A. Ruzicka ꢀ Z. Padelkova
Department of General and Inorganic Chemistry,
Faculty of Chemical Technology, University of Pardubice,
Studentska 573, 53210 Pardubice, Czech Republic
123

206
T. Weidlich et al.
Herein we wish to report, for the first time, efficient and
with DMA was selected as model reaction; the results are
1
presented in Table 2. The reaction was monitored by H
straightforward methodology for synthesis of (E)-N,N-
dimethylcinnamamides using condensation of benzalde-
hydes with DMA in the presence of (RO)2CO as
dehydrating agents.
NMR spectroscopy of CDCl3 extracts of evaporated reac-
tion mixtures. It could be seen that addition of excess DEC
or DMC to the mixture of 1g, DMA, and K2CO3 provides
better results, whereas in the absence of (RO)2CO under
the same reaction conditions the conversion to 2g was low.
Formation of the appropriate alcohols was proved in dis-
tillates obtained during the condensation reaction of 1g
with DMA when DEC or DMC were added to the reaction
mixture (Table 2, entries 2–7).
Results and discussion
We discovered that the alkylation of vanillin (1a) with
diethyl carbonate (DEC) dissolved in excess DMA in the
presence of K2CO3 led to the formation of (E)-4-ethoxy-3-
methoxy-N,N-dimethylcinnamamide (2a) in nearly quan-
titative yield (Table 1, entry 1). This reaction was tested on
a series of hydroxybenzaldehydes 1a–1f using DEC,
dimethyl carbonate (DMC), and dibutyl carbonate (DBC)
as alkylating agents (Table 1, entries 1–9). Isolation of the
products from the evaporated reaction mixture was
achieved by simple crystallization from alkanes.
Replacement of K2CO3 with K3PO4, which is known as
a simple substitute for strong bases in polar aprotic solvents
[30], enables complete conversion of 1g to 2g (Table 2,
entries 3, 5–7). It was proved that application of excess of
DEC enables direct reuse of solvent distilled from the
reaction mixture (Table 2, entries 6–7) without the need for
additional dehydration.
In order to study the scope of the condensation reaction
between ArCHO and DMA, a series of cinnamamides 2g–
2p were synthesized and isolated simply by crystallization
of the evaporated reaction mixture (Table 3, entries 1–8).
DEC was used as more suitable (RO)2CO despite its
boiling point (126 °C). When we tried to expand the series
of benzaldehydes to ortho-nitro or para-nitrobenzaldehyde,
we found that these compounds were decomposed to an
unseparable mixture of products, probably because of
parallel SNAr reactions (Table 3, entries 9, 10).
Moreover, we demonstrated that the mixtures of unre-
acted DMA with (RO)2CO are simply recyclable without
loss of yield after refilling of spent DMA and (RO)2CO.
The structure of 2b was proved by X-ray crystallography
(Fig. 1).
Interestingly, the condensation reaction of vanillin (1a)
with DMA and base without addition of (RO)2CO does not
proceed (Table 1, entry 10). To evaluate the effect of
(RO)2CO, the reaction of 4-methoxybenzaldehyde (1g)
Table 1 Synthesis of (E)-alkoxy-N,N-dimethylcinnamamides 2 by reaction of hydroxybenzaldehydes 1 with (RO)2CO and DMA
H
C
O
C
CHO
OR
OR
O
CH3
K2CO3
C
H
N
+
+
O
CH3
C
C
G
- CO2
- R-OH
G
CH3
NMe2
OH
OR
1a-1f
2a-2i
Entry
Substituted hydroxybenzaldehyde as substrate
t (h)
Used (RO)2CO
Yield of 2 (%)a
Yield of purified 2 (%)b
1
2
4-Hydroxy-3-methoxy- (1a)
2-Hydroxynaphthalene-1-carbaldehyde (1b)
3-Hydroxy- (1c)
48
48
73
44
47
44
62
21
67
48
DEC
DEC
DEC
DMC
DMC
DMC
DMC
DBC
DBC
None
97 (2a)
90 (2b)
93 (2c)
91 (2d)
97 (2e)
93 (2f)
72 (2a)
67 (2b)
67 (2c)
62 (2d)
53 (2e)
69 (2f)
67 (2g)
65 (2h)
56 (2i)
–
3
4
2-Hydroxy- (1d)
5
3-Hydroxy- (1c)
6
3,4-Dihydroxy- (1e)
7
4-Hydroxy- (1f)
90 (2g)
92 (2h)
94 (2i)
8
3-Hydroxy- (1c)
9
3,4-Dihydroxy- (1e)
10
4-Hydroxy-3-methoxy- (1a)
Unreacted 1a
10 mmol 1 at 145-150 °C in air using 15 mmol base, 100 mmol DEC, and 50 cm3 DMA, each reaction proceeds with 100% conversion of
starting ArCHO
a
1
Based on H NMR
b
After crystallization
123

Condensation of aromatic aldehydes with N,N-dimethylacetamide
207
Fig. 1 The molecular structure
of 2b (CCDC No. 723820), an
ORTEP view showing the
thermal ellipsoids at 50%
probability (arbitrary spheres
for H atoms); selected bond
˚
lengths (A) and angles (°): O1
C1 1.360(2), O1 C11 1.441(2),
N1 C15 1.351(3), N1 C17
1.450(3), N1 C16 1.450(3), C2
C13 1.460(3), C14 C13
1.328(3), C14 C15 1.475(3),
C15 O2 1.229(3), C1 O1 C11
119.28(17), C15 N1 C17
124.1(2), C15 N1 C16 120.0(2),
C17 N1 C16 115.69(19), O1 C1
C2 116.95(18), O1 C1 C10
121.49(19)
Table 2 Optimization of
reaction conditions for
condensation of
Entry
t (h)
Base
Addition of
(RO)2CO
Conversion of 1g,
1
by H NMR (%)
Yield of 2g, by
1H NMR (%)
4-methoxybenzaldehyde (1g)
with DMA
1
44
42
43
42
44
46
46
1.1 eq. K2CO3
1.1 eq. K2CO3
1.1 eq. K3PO4
1.1 eq. K2CO3
1.1 eq. K3PO4
1.1 eq. K3PO4
1.1 eq. K3PO4
None
4
82
4
71
93
74
94
92
95
2
7.5 eq. DMC
7.5 eq. DMC
7.5 eq. DEC
7.5 eq. DEC
1 eq. DEC
1.2 eq. DEC
3
100
83.5
100
100
100
a
Recycled solvents from entry
5 (mixture of DMA and DEC)
were used
4
5
b
6a
7b
Recycled solvents from entry
6 (mixture of DMA and DEC)
were used
Upscaling of 2n preparation (X-ray structure of 2n is
shown in Fig. 2) was performed using two-times recycled
DMA and DEC which were distilled from the reaction
mixture during the work-up. Consumption of DEC and
DMA (less than 10% during each reaction cycle) was
supplemented with fresh DEC and DMA (compared with
the first reaction using commercial 99%? DEC and DMA)
without significant drop of the yield of 2n. During repeated
syntheses of 2n aqueous mother liquor from the reaction
work-up was collected, and contained undesirable quanti-
ties of 2-bromoaromatic compounds, mainly 2n.
satisfactorily for pretreatment of aqueous mother liquor
contaminated with 2n. The essentially quantitative de-
1
halogenation of 2n is supported by the H NMR spectral
pattern typical of a monosubstituted phenyl ring with a
CH2–CH2–G group. Subsequent GC–MS analysis verified
the formation of N,N-dimethyl-3-phenylpropionamide 3
(C11H15NO, M = 177) (Scheme 1).
Conclusions
Experiments were performed to reduce the quantity of
brominated aromatic compounds (adsorbable organic hal-
ogens, AOX) in this mother liquor by reductive
pretreatment [31]. The modified dehalogenation method
published by Lunn [31], based on addition of Raney
aluminum–nickel alloy to the alkaline aqueous solution
of halogenated aromatic compounds, has been tested
The reaction of hydroxybenzaldehydes in DMA using
dialkyl carbonates as inexpensive and non-toxic alkylating
agents serves as a simple and selective method for prepa-
ration of (E)-N,N-dimethylalkoxycinnamides. In addition,
the condensation reaction of aromatic aldehydes with
DMA was developed using DEC as dehydrating agent. All
the prepared cinnamamides were obtained exclusively in
123

208
T. Weidlich et al.
Table 3 Synthesis of (E)-N,N-dimethylcinnamamides 2 by condensation reaction of ArCHO 1 and DMA
H
OEt
O
H
K2CO3 or
K3PO4
+
CO2 + 2 EtOH
C
H
+
+
O
CH3
C
C
O
C
G
C
C
G
NMe2
OEt
O
NMe2
1
DMA
DEC
2
Entry
Ar-CHO 1
t (h)
Base
Yield of 2 (%)a
Yield of purified 2 (%)b
1
2
p-MeO–C6H4– (1g)
Ph– (1h)
44
48
42
45
64
47
21
72
40
40
K3PO4
K2CO3
K3PO4
K2CO3
K2CO3
K2CO3
K2CO3
K3PO4
94 (2g)
90 (2j)
92 (2k)
91 (2l)
92 (2m)
91 (2n)
93 (2o)
89 (2p)
74 (2g)
63 (2j)
3
p-Me–C6H4– (1i)
p-Cl–C6H4– (1j)
o-Cl–C6H4– (1k)
o-Br–C6H4– (1l)
m-NO2–C6H4– (1m)
56 (2k)
4
71 (2l)
5
62 (2m)
6
73 (2n)
7
75 (2o)
8
terephthaldehyde (1n)
o-NO2–C6H4– (1o)
p-NO2–C6H4– (1p)
61 (2p) (G = 4-CH=CH–CONMe2
c
9
K2CO3 or K3PO4
K2CO3 or K3PO4
–
–
–
c
10
–
10 mmol 1 at 145–150 °C in air using 15 mmol base, 100 mmol DEC, and 50 cm3 DMA
a
b
c
1
Based on H NMR spectra
After crystallization
Formation of complex mixture of compounds
Fig. 2 The molecular structure
of 2n (CCDC No. 691110), an
ORTEP view showing the
thermal ellipsoids at 50%
probability (arbitrary spheres
for H atoms); selected bond
˚
lengths (A) and angles (°): O1
C1 1.236(4), C2 C3 1.316(5),
C2 C1 1.491(4), N1 C1
1.341(4), N1 C11 1.454(4), N1
C10 1.455(5), C3 C4 1.469(4),
C3 C2 C1 118.9(3)
Scheme 1
H
Br
H
C
Ni
O
+ Al + 3 H2O + OH-
+ [Al(OH)4]- + Br-
CH2 CH2
C
C
H
O
NMe2
C
NMe2
2n
3
(E) configuration in good yields. It was demonstrated that
unreacted DEC and DMA could be simply recycled with-
out significant change of the yield of cinnamamides. The
advanced method for AOX minimization was tested
successfully using dehalogenation of bromoaromatic
compound 2n, which contaminated the aqueous mother
123

Condensation of aromatic aldehydes with N,N-dimethylacetamide
209
liquor. Samples of the reported compounds are available
from the authors.
Table 4 Crystallographic data for 2b and 2n
Compound
2b
2n
Empirical formula
Crystal system
Space group
C17H19NO2
Monoclinic
P 21/c
C11H12BrNO
Monoclinic
P 21/c
Experimental
˚
a (A)
8.0232(9)
8.1688(11)
22.9021(12)
102.284(7)
4
8.8470(6)
11.9740(7)
10.7030(6)
108.946(5)
4
All reactions were carried out in air. All chemicals were
purchased as reagent grade from commercial suppliers
(Across, Sigma–Aldrich) and used without further purifi-
cation. IR spectra were measured on a Mattson ATI Genesis
FT-IR spectrometer. Proton (1H NMR) and carbon (13C
NMR) nuclear magnetic resonance spectra of all products
were recorded at 25 °C on a Bruker 360 at 360.14 and
90.57 MHz, respectively. The chemical shifts are given in
˚
b (A)
˚
c (A)
b (°)
Z
3
˚
V (A )
1466.6(3)
1.301
1072.39(11)
1.574
Dc (g cm-3
Crystal size (mm3)
)
0.47 9 0.24 9 0.16
Colorless needle
0.089
0.19 9 0.17 9 0.11
Colorless needle
3.799
1
ppm on the delta scale (d). The H NMR spectra are ref-
Crystal shape
l (mm-1
F (000)
erenced to tetramethylsilane (d = 0 ppm) in CDCl3 or to
the signal of the solvent peak (DMSO-d6, d = 2.55 ppm).
Chemical shifts of 13C NMR spectra are reported in ppm
(CDCl3: d = 77.0 ppm, DMSO-d6: d = 39.6 ppm).
)
616
512
h; k; l range
-10, 10; -10, 10;
-28, 29
-11, 10; -15, 15;
-13, 13
1
Detailed H and 13C NMR spectra are available from the
h range (°)
1; 27.5
3.40; 27.5
10,530
authors. The elemental analyses (C, H, N) were conducted
using Elemental Analyzer EA 1108 (Fisons) and results
agreed favorably with calculated values. Melting points
were determined on a Boetius (Carl Zeiss Jena) apparatus.
Low-resolution mass spectra were recorded on a Shimadzu
GCMS QP 2010 GC–MS instrument equipped with a DB-
XLB capillary column (30 m 9 0.25 mm, 0.25 lm) and
operating at an ionization energy of 70 eV. The oven tem-
perature (GC) was 250 °C. The X-ray data for colorless
crystals of 2b (CCDC No. 723820) and 2n (CCDC No.
691110) were obtained at 150 K using an Oxford Cryo-
stream low-temperature device on a Nonius KappaCCD
Reflections measured
Independent Raint
Observed I [ 2r(I)
Parameters refined
16,875
3,324 (0.0482)
2,314
2,450 (0.0408)
1,924
191
127
-3
˚
Max/min Dq (eA
)
0.275/-0.381
1.088
0.519/-0.582
1.135
GOFb
Rc/wR
CCDC No.
a
0.0632/0.1406
723820
0.0434/0.0866
691110
Rint = R|F2o - F2o,mean|/RF2o
GOF = [R(w(F2o - F2c)2)/(Ndiffrs - Nparams)] for all data
b
‘
cR(F) = R||Fo| - |Fc||/R|Fo| for observed data, wR(F2) = [R(w(F2o -
F2c)2)/(Rw(F2o)2)] for all data
‘
˚
diffractometer with MoKa radiation (k = 0.71073 A), a
graphite monochromator, and the / and v scan mode
(Table 4). Data reductions were performed with DENZO-
SMN [32]. The absorption was corrected by integration
methods [33]. Structures were solved by direct methods
(Sir92) [34] and refined by full matrix least-square based on
F2 (SHELXL97) [35]. Hydrogen atoms were mostly
localized on a difference Fourier map, however to ensure
uniformity of treatment of the crystal, all hydrogens were
recalculated into idealized positions (riding model) and
assigned temperature factors Hiso(H) = 1.2 Ueq (pivot
atom) or 1.5 Ueq for the methyl moiety with C–H = 0.96,
General preparation of 2g–2p exemplified by 2n
(this procedure enables the recycling of solvent
without decrease of yield)
To 3.9 g 2-bromobenzaldehyde (1l, 0.02 mol) dissolved in
12 cm3 DEC (12.3 g, 0.104 mol) and 160 cm3 DMA
(153.5 g, 1.744 mol) 4.4 g anhydrous K3PO4 (0.02 mol)
was added. The reaction flask was fitted to a condenser
equipped with a CaCl2 tube. The reaction mixture was
stirred at 145 °C for 62 h, cooled, and the distillate was
weighed and analyzed by 1H NMR (5.2 g, contains
74.1 mol% EtOH and 25.9 mol% DEC). The cooled
reaction mixture was evaporated at max. 135 °C to dryness
under reduced pressure (1.33 kPa at the end of distillation),
˚
0.97, and 0.93 A for methyl, methylene, and hydrogen
˚
atoms in the aromatic ring, respectively, 0.86 and 0.82 A
for N–H and O–H groups, respectively. Crystallographic
data for structural analysis have been deposited with the
Cambridge Crystallographic Data Centre. Copies of this
information may be obtained free of charge from The
Director, CCDC, 12 Union Road, Cambridge CB2 1EY, UK
(fax: ?44-1223-336033; e-mail: deposit@ccdc.cam.ac.uk
or url: http://www.ccdc.cam.ac.uk).
1
cooled, the distillate (149.9 g) was analyzed by H NMR
(it contained 4.5 mol% DEC, 93.8 mol% DMA, and
1.7 mol% EtOH). This means that recovery of solvents was
91.8% (90.6%) for DMA (DEC). The distillation residue
was diluted with 200 cm3 water, heated under reflux for
123

210
T. Weidlich et al.
General preparation of 2a–2i exemplified with 2a
5 min, and cooled. The insoluble residue was crystallized
from diethoxymethane leading to pure 2n (3.3 g, 65%).
The next quantity (0.4 g, 8% of theory) of pure 2n crys-
tallized as yellowish needles after a few days of standing of
the aqueous mother liquor at room temperature.
To 1.52 g vanillin (1a, 0.01 mol) dissolved in 11.8 g DEC
(0.1 mol) and 90 cm3 DMA (82.5 g, 0.947 mol) 2.77 g
anhydrous K2CO3 (0.02 mol) was added. The reaction
mixture was heated at 145 °C with magnetic stirring for
48 h. The collected reaction distillate was weighed and
(E)-3-(2-Bromophenyl)-N,N-dimethyl-2-propenamide
(2n, C11H12BrNO)
1
analyzed by H NMR (1.4 g, contained 86.5 mol% EtOH,
M.p.: 85–86 °C (from cyclohexane); IR (KBr): m ¼ 1;645
10.38 mol% DEC, and 3.11 mol% DMA). The hot reaction
mixture was filtered, and the filtrates were evaporated to
dryness at max. 130 °C under reduced pressure (1.33 kPa).
The distillate (88.9 g) was analyzed by 1H NMR and
contained 7.9 mol% DEC and 92.1 mol% DMA (recovery
97.6% of DMA and 80.5% of DEC). The distillation resi-
due was crystallized from cyclohexane to afford 1.8 g
(72%) 2a.
(C=O, amide), 1,619 (C=C), 1,144 (C–N), 748 (C–H
1
arom.) cm-1; H NMR (360 MHz, CDCl3): d = 2.96 and
3.06 (s, 6H, 29 CH3), 6.73 (d, 1H, J = 15.4 Hz, CH=),
3
7.10–7.15 (m, 1H, H-arom.), 7.20–7.25 (m, 1H, H-arom.),
3
7.49–7.53 (m, 2H, H-arom.), 7.88 (d, 1H, J = 15.4 Hz,
CH=) ppm; 13C NMR (90 MHz, CDCl3): d = 35.6 (CH3),
37.2 (CH3), 120.6 (CH), 124.6 (Cq), 127.3 (CH), 127.4
(CH), 130.2 (CH), 133.0 (CH), 135.2 (Cq), 140.3 (CH),
165.9 (C=O) ppm; MS (70 eV): m/z (%) = 253 (M?, 6),
255 (M??2, 6), 209 (31), 211 (30), 174 (100), 102 (69), 98
(33).
(E)-3-(4-Ethoxy-3-methoxyphenyl)-N,N-dimethyl-2-
propenamide (2a, C14H19NO3)
M.p.: 125–127 °C; IR (KBr): m ¼ 1;653 (C=O, amide),
1,606 (C=C), 1,267 (R–O–Ar), 1,138 (C–N), 793 (C–H
1
arom.) cm-1; H NMR (360 MHz, CDCl3): d = 1.32 (t,
3H, CH3), 2.92 (s, 3H, CH3), 3.04 (s, 3H, CH3), 3.71 (s,
Reductive treatment of aqueous mother liquor
from preparation of 2n
3H, CH3O), 4.00 (q, 2H, CH2), 6.67 (d, 1H, 3J = 15.5 Hz,
3
CH=), 6.77 (d, 1H, J = 8.2 Hz, H-arom.), 6.96 (d, 1H,
The alkaline mother liquor from 2n was saturated with
bromo derivative 2n and contained DMA, as was con-
1
firmed by H NMR spectroscopy of the CDCl3 extract.
4J = 1.8 Hz, H-arom.), 7.01 (dd, 1H, 3J = 8.2 Hz,
3
4J = 1.8 Hz, H-arom.), 7.52 (d, 1H, J = 15.5 Hz, CH=)
ppm; 13C NMR (90 MHz, CDCl3): d = 14.6 (CH3), 35.8
(CH3), 37.3 (CH3), 55.9 (CH3), 64.2 (CH2), 110.2 (CH),
112.2 (CH), 114.9 (CH), 121.6 (CH), 128.1 (Cq), 142.2
(CH), 149.2 (Cq), 149.7 (Cq), 166.8 (Cq) ppm; MS (70 eV):
m/z (%) = 249 (M?, 67), 205 (100), 177 (28), 145 (59),
117 (18), 89 (16).
Al–Ni alloy (0.54 g, 50% Ni ? 50% Al, 0.01 mol of Al) was
added to 100 cm3 waste water (pH 11.2) from the synthesis
of 2n and vigorously stirred overnight by magnetic stirring
at room temperature. After filtration of the metal slurry the
filtrate was extracted with CDCl3 and analyzed by GC–MS
which indicated formation of N,N-dimethyl-3-phenylpro-
pionamide; MS (70 eV): m/z (%) = 177 (M?, 79), 105
(Ph–CH2CH2–, 59), 91 (PhCH2–, 98), 72 (CONMe2, 82),
58 (23), 45 (100).
(E)-3-(2-Ethoxy-1-naphthyl)-N,N-dimethyl-2-propenamide
(2b, C17H19NO2)
M.p.: 98–99 °C (from cyclohexane); IR (KBr): m ¼ 1;639
(C=O, amide), 1,589 (C=C), 1,294 (R–O–Ar), 808 (C–H
1
(E,E)-3,30-(1,4-phenylene)bis(N,N-dimethyl-
2-propenamide) (2p, C16H20N2O2)
arom.) cm-1; H NMR (360 MHz, CDCl3): d = 1.43 (t,
3H, CH3), 3.08 (s, 6H, 29 CH3), 4.14 (q, 2H, CH2), 7.17–
7.34 (m, 3H, CH= and 29 H-arom.), 7.43–7.47 (m, 1H, H-
arom.), 7.70–7.75 (m, 2H, H-arom.), 8.20–8.22 (d, 2H, H-
M.p.: 242–244 °C (from diethoxymethane–ethanol); IR
(KBr): m ¼ 1;645 (C=O, amide), 1,603 (C=C), 1,139
1
(C–N) cm-1; H NMR (360 MHz, CDCl3): d = 3.05 (bs,
6H, 29 CH3), 6.84 (d, 2H, J = 15.3 Hz, 29 CH=), 7.45
3
arom.), 8.28 (d, 1H, J = 15.5 Hz, CH=) ppm; 13C NMR
3
(90 MHz, CDCl3): d = 15.1 (CH3), 35.8 (CH3), 37.2
(CH3), 64.6 (CH2), 113.8 (CH), 117.5 (Cq), 122.6 (CH),
123.4 (CH), 123.6 (CH), 126.9 (CH), 128.3 (CH), 128.8
(Cq), 130.6 (CH), 132.9 (Cq), 134.9 (CH), 155.5 (Cq), 167.7
(Cq) ppm; MS (70 eV): m/z (%) = 269 (M?, 12), 224
(100), 197 (61), 168 (16), 141 (25), 139 (19), 72 (24).
3
(s, 4H, H-arom.), 7.58 (d, J = 15.3 Hz, 2H, 29 CH=)
ppm; 13C NMR (90 MHz, CDCl3): d = 36.6 (29 CH3),
117.9 (29 CH=), 128.1 (49 CH), 136.4 (Cq), 141.4 (29
CH=), 143.4 (CH), 166.4 (29 C=O) ppm; MS (70 eV): m/z
(%) = 272 (M?, 36), 228 (63), 229 (74), 201 (19), 183
(56), 155 (35), 128 (41), 127 (49), 72 (100).
Compounds 2j [21, 36], 2k [37, 38], 2l [37, 39], 2m
[40], and 2o [37] were characterized by comparison of their
spectral data (1H, 13C NMR) and melting points with data
found in literature.
(E)-3-(3-Ethoxyphenyl)-N,N-dimethyl-2-propenamide
(2c, C13H17NO2)
M.p.: 72–73 °C (from cyclohexane); IR (KBr): m ¼ 1;653
(C=O, amide), 1,614 (C=C), 1,261 (R–O–Ar), 777 (C–H
123

Condensation of aromatic aldehydes with N,N-dimethylacetamide
211
arom.) cm-1; 1H NMR (DMSO-d6): d = 1.36–1.40 (t, 3H,
CH3), 2.97 (s, 3H, CH3), 3.20 (s, 3H, CH3), 4.11 (q, 2H,
CH2), 6.96–6.99 (m, 1H, H-arom.), 7.21–7.37 (m, 4H,
H-arom.. and CH=), 7.44–7.49 (d, 1H, 3J = 15.4 Hz, CH=)
ppm; 13C NMR (DMSO-d6): d = 14.7 (CH3), 35.4 (CH3),
37.0 (CH3), 63.2 (CH2), 113.5 (CH), 115.7 (CH), 118.9
(CH), 120.6 (CH), 129.8 (CH), 136.7 (Cq), 141.0 (CH),
158.9 (Cq), 165.6 (C=O) ppm; MS (70 eV): m/z (%) = 219
(M?, 50), 176 (34), 175 (57), 147 (100), 119 (27), 91 (34).
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(E)-3-(3-Butoxyphenyl)-N,N-dimethyl-2-propenamide
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1
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3
(m, 1H, H-arom.), 7.60–7.65 (d, 1H, J = 15.4 Hz, CH=)
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(CH), 115.4 (CH), 117.5 (CH), 120.1 (CH), 129.6 (CH),
136.6 (Cq), 142.1 (CH), 159.3 (Cq), 166.5 (C=O) ppm; MS
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(E)-3-(3,4-Dibutoxyphenyl)-N,N-dimethyl-2-propenamide
(2i, C19H29NO3)
M.p.: 77 °C (from hexane); IR (KBr): m ¼ 2;958; 2,872
(C–H), 1,647 (C=O, amide), 1,595 (C=C), 1,259 (R–O–
Ar), 1,136 (C–N), 802 (C–H, arom.) cm1; 1H NMR
(CDCl3): d = 0.89–0.94 (m, 6H, 29 CH3), 1.42–1.46 (m,
4H, 29 CH2), 1.70–1.76 (m, 4H, 29 CH2), 3.04 (bd, 6H,
29 CH3), 3.92–3.98 (m, 4H, 29 CH2O), 6.67 (d, 1H,
3
3J = 15.3 Hz, CH=), 6.78 (d, 1H, J = 7.3 Hz, H-arom.),
6.98 (d, 1H, 4J = 1.7 Hz, H-arom.), 7.01 (dd, 1H,
3J = 7.3 Hz, 4J = 1.7 Hz), 7.53 (d, 1H, 3J = 15.3 Hz,
CH=) ppm;13C NMR (CDCl3): d = 13.6 (CH3), 13.7
(CH3), 18.9 (CH2), 19.0 (CH2), 31.0 (CH2), 31.1 (CH2),
35.7 (CH3), 37.2 (CH3), 68.5 (CH2), 68.9 (CH2), 112.6
(CH), 113.0 (CH), 114.7 (CH), 121.7 (CH), 128.0 (Cq),
142.2 (CH), 148.9 (Cq), 150.6 (Cq), 166.7 (C=O) ppm; MS
(70 eV): m/z (%) = 319 (M?, 80), 275 (53), 219 (60), 163
(100), 145 (23).
¨
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Compounds 2d [39], 2e [37], 2f [37, 41], and 2g [42]
were characterized by comparison of their spectral data
(1H, 13C NMR) and melting points with data provided in
literature.
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Acknowledgments We are grateful to the Grant Agency of the
Czech Republic, projects No. 203/07/P248, 104/09/0829 and Ministry
of Education, Youth and Sports of the Czech Republic MSM
0021627501 and MSM 0021627502 for financial support.
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123