New conjugated dienamides via palladium-catalyzed selective aminocarbonylation of enynes

Article abstract of DOI:10.1016/j.tetlet.2012.09.084

New conjugated dienamides have been synthesized effectively via palladium-catalyzed aminocarbonylation of enynes in the presence of various amines, diaminoalkanes, and aminoalcohols. The products have been utilized as substrates in alkoxycarbonylation rea

Full text of DOI:10.1016/j.tetlet.2012.09.084

Tetrahedron Letters 53 (2012) 6535–6539
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Tetrahedron Letters
journal homepage: www.elsevier.com/locate/tetlet
New conjugated dienamides via palladium-catalyzed selective
aminocarbonylation of enynes
S. M. Shakil Hussain a, Rami Suleiman b, Bassam El Ali c,
⇑
a Center for Petroleum and Minerals, King Fahd University of Petroleum & Minerals (KFUPM), Dhahran 31261, Saudi Arabia
b Center of Research Excellence in Corrosion, King Fahd University of Petroleum & Minerals (KFUPM), Dhahran 31261, Saudi Arabia
c Chemistry Department, King Fahd University of Petroleum & Minerals (KFUPM), Dhahran 31261, Saudi Arabia
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 8 June 2012
Revised 6 September 2012
Accepted 20 September 2012
Available online 27 September 2012
New conjugated dienamides have been synthesized effectively via palladium-catalyzed aminocarbonyla-
tion of enynes in the presence of various amines, diaminoalkanes, and aminoalcohols. The products have
been utilized as substrates in alkoxycarbonylation reactions using methanol as the nucleophile and
Pd(PPh3)2Cl2 as the catalyst to afford novel
x-amidoesters in high yields and selectivities. Interestingly,
the product obtained from the alkoxycarbonylation reaction of the dienamide product of enyne 1b was
observed to undergo carbonylation of the
erization of the second isolated double bond.
a
,b-double bond with respect to the carbonyl group and isom-
Ó 2012 Elsevier Ltd. All rights reserved.
Keywords:
Aminocarbonylation
Enyne
Dienamides
Palladium
Alkoxycarbonylation
Dienamides are recognized as key reactive intermediates in or-
ganic synthesis due to their synthetic potential and occurrence in
Nature.1 A variety of dienamide derivatives have been isolated
from natural sources and have been reported to have antioxidant
and cytotoxic activities.2 Several alkaloids have been synthesized
using dienamides as starting materials.3 Acyclic dienamides are
also key constituents in a number of biologically active natural
products and pharmaceutically relevant units.4 Despite their utility
and biological potential, available synthetic routes for dienamides
are still very limited.5 Moreover, reports on the synthesis of diena-
mides via metal-catalyzed carbonylation are rare in the literature.
Imanda and Alper reported the palladium-catalyzed regioselective
carbonylation of propargyl amines into 2,4- or 2,3-dienamides.6
The need to develop efficient, mild and simple methods for the
synthesis of more versatile and new dienamides remains an inter-
esting challenge. Aminocarbonylation of enynes can be considered
as an attractive route toward the simple, efficient and practical
preparation of a variety of dienamides. Encouraged by the impor-
tance of aminocarbonylation reactions in organic syntheses,7 our
group has succeeded in the development of different palladium
catalyst systems for the aminocarbonylation of various internal
and terminal alkyl and aromatic alkynes, using different types of
amines as nucleophiles.8
In this Letter, we report a one-step protocol for the regioselec-
tive synthesis of new dienamides, in high yields, via palladium-cat-
alyzed aminocarbonylation of enyne substrates using a modified
catalytic system that we reported previously for the aminocarb-
onylation of terminal alkynes.8a Different reaction parameters have
been screened and optimized in order to maximize the yield and
the regioselectivity of the aminocarbonylation. Moreover, the
dienamides obtained from the aminocarbonylation step were sub-
jected to further catalytic alkoxycarbonylation with methanol to
produce new
x-amidoesters with interesting structural properties.
The aminocarbonylation of 1-ethynylcyclohexene (1a), adopted
as a model substrate, with diisobutylamine (2a) in the presence of
a palladium-diphosphine catalyst system was carefully optimized
by varying the reaction conditions (Eq. (1)) and the results are
summarized in Table 1. Excellent conversion and regioselectivity
toward the (2-gem)-4-dienamide 3aa was achieved, while
(2-trans)-4-dienamide 4aa was obtained as a minor product. The
use of 1,3-bis(diphenylphosphino)propane (dppp) as the ligand
(Table 1, entry 2) led to a higher conversion of 1a and excellent
selectivity toward 3aa, and better reproducibility compared to
1,4-bis(diphenylphosphino)butane (dppb) (Table 1, entry 1), 1,1’-
bis(diphenylphosphino)ferrocene (dppf) (Table 1, entry 3), and
2,20-bis(diphenylphosphino)-1,10-binaphthyl (BINAP) (Table 1, en-
try 4) as ligands and Pd(OAc)2 as the catalyst precursor. Low to
average conversions (12% and 48%) were obtained with the mono-
phosphine ligands PPh3 and P(p-Tol)3 (Table 1, entries 12 and 13),
respectively. The major carbonylation product of the reaction with
⇑
Corresponding author. Tel.: +966 3 8604491; fax: +966 3 8604277.
E-mail address: belali@kfupm.edu.sa (B.E. Ali).
0040-4039/$ - see front matter Ó 2012 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.tetlet.2012.09.084

6536
S. M. Shakil Hussain et al. / Tetrahedron Letters 53 (2012) 6535–6539
Table 1
We next investigated the aminocarbonylation of 1a with a
range of primary and secondary amines and the results are sum-
marized in Table 2. Excellent conversions (82–98%) and selectivi-
ties (94–99%) were achieved with alkyl amines 2a–d (Table 2,
entries 1–4) and benzylamine 2e (Table 2, entry 5) yielding the cor-
responding (2-gem)-4-dienamide isomers 3aa–ae as the predomi-
nant products. Surprisingly, no catalytic activity was observed in
the presence of aromatic amines such as aniline 2f and naphthyl-
amine 2g (Table 2, entries 6 and 7), probably due to the low nucle-
ophilicity of these nucleophiles.
These interesting results have encouraged us to initiate a sepa-
rate computational mechanistic study to clarify the possible cata-
lytic pathways for the aminocarbonylation of these enynes, and
also to compare them with our previously reported mechanistic
study for the aminocarbonylation of terminal alkynes.9
The palladium-catalyzed aminocarbonylation reaction was also
successfully applied for the carbonylation of 1a in the presence of
diaminoalkanes 5a–c (Scheme 1). Interestingly, the two amino
groups in the diaminoalkanes, regardless of the number of carbon
atoms in the chain, were reactive as amines in the aminocarbony-
lation of two molecules of 1a leading to the formation of new
alkyl-di-(2-gem)-4-dienamides 6aa–ac in excellent isolated yields
(81–91%).
It is worth noting that the catalyst system composed of
Pd(OAc)2 and dppp was also active and selective in the aminocarb-
onylation of 2-methyl-1-buten-3-yne (1b) using the amines 2a, 2h,
and 1,3-propanediamine (5a) as nucleophiles.10 Excellent isolated
yields (78–95%) of dienamides 3ba, 3bh, and 6ba were obtained
(Scheme 2).
The most interesting results were obtained when we utilized
the described catalyst system [Pd(OAc)2/dppp] for the aminocarb-
onylation of enyne 1a with aminoalcohols 7a–c as nucleophiles.
These are considered as interesting molecules having two different
functionalities that are typically available as nucleophiles for
aminocarbonylation as well as alkoxycarbonylation reactions. Sur-
prisingly, aminocarbonylation products were obtained exclusively
(Scheme 3), and the OH function remained intact. This result was
confirmed by the absence of any catalytic activity for our amino-
carbonylation catalyst system in the alkoxycarbonylation reaction
of 1a with different alcohols. It is important to note that new
dienamides 8aa–ac, having diene, amine, and hydroxy functions
are important for the synthesis of new and useful heterocyclic
compounds.
Selected experimental results for the optimization of the catalyst system for the
aminocarbonylation of 1aa
Entry Catalyst
precursor
Ligand Conversion of
Product
distributionb
(%)
10ab
(%)
1ab (%)
3aa
4aa
1
2
3
4
5
6
7
Pd(OAc)2
Pd(OAc)2
Pd(OAc)2
Pd(OAc)2
PdSO4
PdCl2(PPh3)2
Pd(NO3)2
Pd(OAc)2
Pd(OAc)2
Pd(OAc)2
Pd(OAc)2
Pd(OAc)2
Pd(OAc)2
dppb
dppp
dppf
BINAP
dppp
dppp
dppp
dppp
dppp
dppp
—
92
98
92
83
97
80
100
65
86
78
50
20
48
93
94
82
88
93
92
94
84
85
72
—
5
4
12
9
4
1
5
4
6
2
2
6
3
3
7
1
12
9
22
100
48
45
8c
9d
10e
11f
12
13
6
—
3
PPh3
P(p-
49
42
13
Tol)3
a
Reaction conditions: catalyst precursor (0.02 mmol), ligand (0.08 mmol),
1-ethynylcyclohexene (1a) (2 mmol), diisobutylamine (2a) (2.2 mmol), p-TsOH
(0.3 mmol), CO (200 psi), CH3CN (10 ml), 110 °C, 6 h.
b
Determined by GC based on 1a.
Solvent = CH2Cl2.
Temperature = 90 °C.
No p-TsOH was added.
c
d
e
f
No ligand was added.
PPh3 and P(p-Tol)3 was 3aa (49% and 42%, respectively) in addition
to the homocoupling product (48% and 45%, respectively). It is clear
that the mechanism of the carbonylation reaction of enynes using
monosphosphine ligands differs from that occurring in the pres-
ence of diphosphines.9
Comparable activities and selectivities were obtained in the
aminocarbonylation of 1a when dppp was applied with other pal-
ladium(II) precursors (Table 1, entries 5–7). The use of CH2Cl2 as
the solvent or a lower temperature of 90 °C resulted in a decrease
in both the activity and selectivity of the aminocarbonylation reac-
tion of 1a (Table 1, entries 8 and 9). The catalyst system still
showed good activity in the aminocarbonylation of 1a even in
the absence of p-TsOH as an additive (Table 1, entry 10). However,
the absence of the ligand resulted only in the formation of the
product 10a obtained via homocoupling of 1a, and no carbonylation
products were identified (Table 1, entry 11). Furthermore, no poly-
merization by-products of 1a were identified from any of the
experiments.
The presence of the interesting diene functionality in the prod-
ucts of the aminocarbonylation of enynes encouraged us to consider
the obtained dienamides as substrates for alkoxycarbonylation
H
O
NRR'
Pd/[L], p-TsOH
NRR'
+
+
HNRR'
+
CH3CN, CO
O
110 oC, 6 h
1a
2a [R=R'=CH2CH(CH3)2]
2b [R=CH(CH3)2; R'=H]
2c [R=R'=CH(CH3)2]
ð1Þ
3aa-ae
1'a
4aa-ae
2d [R=CH2(CH2)4CH3; R'=H]
2e [R=CH2C6H5; R'=H]
2f [R=C6H5; R'=H]
2g [R=C10H7; R'=H]

S. M. Shakil Hussain et al. / Tetrahedron Letters 53 (2012) 6535–6539
6537
Table 2
Pd(II)-catalyzed aminocarbonylation of 1a in the presence of amines 2a–ga
Entry
Amine
Conversion (%)b
Product distributionb (%)
3 [ ]c
4
10a
1
2
3
4
5
Diisobutylamine (2a)
Isopropylamine (2b)
Diisopropylamine (2c)
Hexylamine (2d)
98
91
93
96
82
3aa
95 [93]
3ab
97 [84]
3ac
89 [85]
3ad
99 [90]
3ae
98 [81]
—
4aa
3
4ab
3
4ac
5
4ad
1
2
0
6
0
1
Benzylamine (2e)
4ae
1
—
6
7
Aniline (2f)
Naphthylamine (2g)
0
0
—
—
a
Reaction conditions: Pd(OAc)2 (0.02 mmol), dppp (0.08 mmol), 1-ethynylcyclohexene (1a) (2 mmol), amine (2.2 mmol), p-TsOH (0.3 mmol), CO (200 psi), CH3CN (10 ml),
110 °C, 6 h.
b
Determined by GC based on 1a.
Isolated yield.
c
H
H
N
H
N
Pd(OAc)2 / dppp / p-TsOH / CH3CN
0.02 mmol / 0.08 mmol / 0.30 mmol / 10 mL
X
H2N
NH2
+
X
o
O
O
110 C, CO (200 psi), 15 h
1a
5
6aa-ac
Isolated yield
(2.0 mmol)
(1.1 mmol)
X = -(CH2)3- (5a)
-(CH2)4- (5b)
87%
91%
81%
-(CH2)6- (5c)
Scheme 1. Aminocarbonylation of enyne 1a using diamines 5a–c.
O
2a (2.2 mmol)
N
3ba
94%
H2N
O
Pd(OAc)2 / dppp / p-TsOH / CH3CN
2h
(2.2 mmol)
0.02 mmol / 0.08 mmol / 0.30 mmol / 10 mL
NH
110 oC, CO (200 psi), 6 h
H
1b
(2.0 mmol)
3bh
78%
H2N
NH2
(1.1 mmol)
5a
NH
NH
O
O
6ba
95%
Scheme 2. Aminocarbonylation of enyne 1b using amines 2a, 2h, and 5a.
reactions with methanol using Pd(PPh3)2Cl2 as the catalyst.11 To
our delight, the reactions proceeded smoothly to yield the required
alkoxycarbonylation products in excellent isolated yields (92–
95%). Interestingly, the alkoxycarbonylation of dienamide 3bh
proceeded with isomerization of the second isolated double bond.
This isomerization behavior was not observed for the isolated
double bonds located in the cyclic moiety of substrate 6ab (Eqs. 2
and 3).12

6538
S. M. Shakil Hussain et al. / Tetrahedron Letters 53 (2012) 6535–6539
O
O
Pd(PPh3)2Cl2 (0.04 mmol)
NH
CH3OH (8 mL), CO (100 psi)
110 oC, 6 h
NH
CH3O
ð2Þ
ð3Þ
O
3bh
9bh
95%
O
H
N
O
CH3O
H
N
O
Pd(PPh3)2Cl2 (0.04 mmol)
N
H
N
H
CH3OH (8 mL), CO (100 psi)
110 oC, 6 h
O
O
OCH3
6ab
O
10ab
92%
H
H
N
Pd(OAc)2 / dppp / p-TsOH / CH3CN
OH
0.02 mmol / 0.08 mmol / 0.30 mmol / 10 mL
X
H2N
OH
+
X
110 oC, CO (200 psi), 15 h
O
1a
7
8aa-ac
Isolated yield
(2.0 mmol)
(2.2 mmol)
X = -(CH2)2- (7a)
-(CH2)3- (7b)
81%
79%
78%
-(CH2)4- (7c)
Scheme 3. Aminocarbonylation of enyne 1a using aminoalcohols 7a–c.
622, 84–88; (d) Gadge, S. T.; Khedkar, M. V.; Lanke, S. R.; Bhanage, B. M. Adv.
Synth. Catal. 2012, 354, 2049–2056.
8. (a) Suleiman, R.; Tijani, J.; El Ali, B. Appl. Organomet. Chem. 2010, 24, 38–46; (b)
El Ali, B.; Tijani, J. Appl. Organomet. Chem. 2003, 17, 921–931; (c) El Ali, B.;
Tijani, J.; El-Ghanam, A. M. J. Mol. Cat. 2002, 187, 17–33.
In conclusion, an efficient palladium-diphosphine catalyst sys-
tem was applied for the aminocarbonylation of enyne substrates
using various mono and diaminoalkanes, and aminoalcohols. The
catalyst system showed excellent regioselectivity to produce
(2-gem)-4-dienamide as the predominant product. Interesting
9. Suleiman, R.; Ibdah, A.; El Ali, B. J. Organomet. Chem. 2011, 696, 2355–2363.
10. General Procedure for the aminocarbonylation of enynes;
A mixture of
and novel
x-amidoesters were obtained through the palladium-
Pd(OAc)2 (0.02 mmol), dppp (0.08 mmol), p-TsOH (0.3 mmol), enyne
(2.0 mmol) and amine (2.2 mmol) or aminoalcohol (2.2 mmol) or diamine
(1.1 mmol) in CH3CN (10 ml) was placed in a glass liner, equipped with a stirrer
bar, and then placed in a 45 ml Parr autoclave. The autoclave was vented three
times with CO and then pressurized at room temperature with CO (200 psi).
The mixture was stirred and heated at 110 °C for 6 h or 15 h. After cooling, the
pressure was released, and the solid products were filtered and washed with
catalyzed alkoxycarbonylation of the dienamides prepared in this
study.13 A computational study of plausible mechanisms for the
above noted reactions is in progress.
Acknowledgment
methanol and dried under vacuum. The products were identified by 1H and 13
NMR, and FT-IR spectroscopy and EI-MS analyses.
C
We thank the King Fahd University of Petroleum & Minerals
(KFUPM-Saudi Arabia) for providing support for this work.
11. Suleiman, R.; El Ali, B. Tetrahedron Lett. 2010, 51, 3211–3215.
12. General Procedure for the alkoxycarbonylation of dienamides. A mixture of
Pd(PPh3)2Cl2 (0.04 mmol) and dienamide (0.5 mmol) in MeOH (8 ml) was
placed in a glass liner, equipped with a stirring bar, and placed in a 45 ml Parr
autoclave. The autoclave was vented three times with CO and then pressurized
at room temperature with CO (100 psi). The mixture was stirred and heated at
110 °C for 6 h. After cooling, the pressure was released, the reaction mixture
was filtered after adding anhydrous Na2SO4 and a sample of the filtrate was
immediately analyzed by GC and GC–MS. The solvent was removed and the
products were separated by preparative TLC (30% EtOAc/petroleum ether, 40–
70 °C).
References and notes
1. Mathieson, J. E.; Crawford, J. J.; Schmidtmann, M.; Marquez, R. Org. Biomol.
Chem. 2009, 7, 2170–2175.
2. Mollataghi, A.; Hadi, A. H. A.; Cheah, S.-C. Molecules 2012, 17, 4197–4208.
3. Yasukouchi, T.; Kanematsu, K. J. Chem. Soc., Chem. Commun. 1989, 953–954.
4. Diyabalange, T.; Amsler, C. D.; McClintock, J. B.; Baker, B. J. J. Am. Chem. Soc.
2006, 128, 5630–5631.
5. Tracey, M. R.; Hsung, R. P.; Antoline, J.; Kurtz, K. C. M.; Shen, L.; Slafer, B. W.;
Zhang, Y., online ed. In Science of Synthesis; Houben-Weyl, 2005; Vol. 21, pp
3875–475.
13. Spectral
data
for
representative
compounds.
t
2-Cyclohexenyl-N,N-
diisobutylacrylamide (3aa): Oil, IR (CH2Cl2)
(cmꢀ1) 1621 (CO), 1H NMR d
(ppm) (500 MHz, CDCl3): 0.79 [d, 6H, CH(CH3)2, J = 5.0 Hz], 0.80 [d, 6H,
CH(CH3)2, J = 5.0 Hz], 1.55–1.57 [m, 4H, cyclohexenyl], 1.66–1.68 [m, 1H,
CH(CH3)2], 1.87–1.89 [m, 1H, CH(CH3)2], 2.08–2.10 [m, 4H, cyclohexenyl], 2.97
(d, 2H, NCH2 of isobutyl group, J = 7.5 Hz), 3.26 (d, 2H, NCH2 of isobutyl group,
6. Imada, Y.; Alper, H. J. Org. Chem. 1996, 61, 6766–6767.
7. (a) Li, Y.; Alper, H.; Yu, Z. Org. Lett. 2006, 8, 5199–5201; (b) Driller, K. M.;
Prateeptongkum, S.; Jackstell, R.; Beller, M. Angew. Chem., Int. Ed. 2011, 50, 537–
541; (c) Gabriele, B.; Salerno, G.; Veltri, L.; Costa, M. J. Organomet. Chem. 2001,
J = 7.5 Hz), 4.92 (s, 1H
a, @CH2), 5.15 (s, 1Hb, @CH2), 5.80–5.83 (m, 1H, CH,
cyclohexenyl); 13C NMR d (ppm) (125 MHz, CDCl3), 20.0 (CH3)2, 20.3 (CH3)2,

S. M. Shakil Hussain et al. / Tetrahedron Letters 53 (2012) 6535–6539
6539
21.9 [CH2, cyclohexenyl], 22.4 [CH2, cyclohexenyl], 24.4 (CH), 25.7 (CH), 25.8
[CH2, cyclohexenyl], 28.7 [CH2, cyclohexenyl], 50.6 (NCH2 of isobutyl group),
55.6 (NCH2 of isobutyl group), 109.9 (C CH2 attached to cyclohexenyl), 129.1
(CH, cyclohexenyl), 138.1 (C, cyclohexenyl), 147.6 (C CH2 attached to
cyclohexenyl), 172.2 (CO); GC–MS m/z 264 (M+1). Anal. Calcd for C17H29NO
(263.42): C, 77.51; H, 11.10; N, 5.32. Found: C, 77.42; H, 11.07; N, 5.57.
3.69 (q, 2H, OCH2, J = 5.50 Hz), 4.4 (br s, 1H, OH), 5.18 (s, 1H
a
, @CH2), 5.32 (s,
1Hb, @CH2), 5.92–5.94 (m, 1H, CH, cyclohexenyl), 6.45 [br s, 1H (NH)]; 13C NMR
d (ppm) (125 MHz, CDCl3), 21.8 (CH2, cyclohexenyl), 22.4 (CH2, cyclohexenyl),
25.6 (CH2, cyclohexenyl) 25.7 (CH2, cyclohexenyl), 42.4 (NCH2), 61.9 (OCH2),
113.6 (C CH2 attached to cyclohexenyl), 129.5 (CH, cyclohexenyl), 133.0 (C,
cyclohexenyl), 147.3 (C CH2 attached to cyclohexenyl), 170.8 (CO); GC–MS m/z
196 (M+1). Anal. Calcd for C11H17NO2 (195.26): C, 67.66; H, 8.78; N, 7.17.
Found: C, 67.69; H, 8.47; N, 8.56.
N,N-(Propane-1,3-diyl)bis(2-cyclohexenyl)acrylamide (6aa): Oil, IR (CH2Cl2)
t
(cmꢀ1) 1649 (CO), 3381 (NH); 1H NMR d (ppm) (500 MHz, CDCl3): 1.51–1.54
[m, 2H], 1.63–1.65 [m, 8H cyclohexenyl], 2.06–2.07 [m, 8H, (cyclohexenyl)],
Dimethyl-4,40-butane-1,4-diylbisazanediylbis-3-cyclohexenyl-4-oxobutanoate
3.30 [q, 4H, J = 5.19 Hz], 5.15 (s, 2H
a
, @CH2), 5.27 (s, 2Hb, @CH2), 5.88–5.91 (m,
(10ab): Oil, IR (CH2Cl2) t
(cmꢀ1) 1664 (CO), 3316 (NH); 1H NMR d (ppm)
2H, CH, cyclohexenyl), 6.67 [br s, 2H (NH)]; 13C NMR d (ppm) (125 MHz, CDCl3),
21.7 [CH2, cyclohexenyl], 22.3 [CH2, cyclohexenyl], 25.6 [(CH2)2, cyclohexenyl],
29.7 (NCH2CH2), 35.8 ((NCH2)2), 113.1 (C CH2 attached to cyclohexenyl), 129.2
(CH, cyclohexenyl), 133.0 (C, cyclohexenyl), 147.5 (C CH2 attached to
cyclohexenyl), 170.4 (CO); GC–MS m/z 343 (M+1). Anal. Calcd for C21H30N2O2
(342.48): C, 73.65; H, 8.83; N, 8.18. Found: C, 73.52; H, 8.77; N, 8.32.
(500 MHz, CDCl3): 1.47–1.49 (m, 8H), 1.97–2.07 (m, 8H), 2.11–2.14 (m, 4H),
2.89–2.92 (m, 4H), 3.26 [q, 4H, J = 5.5 Hz], 3.62 (s, 6H), 5.60–5.63 (m, 2H, CH),
5.85–5.87 (m, 2H, CH), 5.93 [br s, 2H (NH)]; 13C NMR d (ppm) (125 MHz, CDCl3),
21.9 [CH2, cyclohexenyl], 22.6 [CH2, cyclohexenyl], 25.2 [(CH2), cyclohexenyl]
25.4 [(CH2), cyclohexenyl], 26.7 ((NCH2CH2)2), 34.2 (COCH), 39.0 ((NCH2)2),
50.6 (COCH2), 51.6 (OCH3), 128.1 (CH, cyclohexenyl), 132.0 (C, cyclohexenyl),
172.1 (COOCH3); 172.9 (CONH). Anal. Calcd for C26H40N2O6 (476.61): C, 65.52;
H, 8.46; N, 5.88. Found: C, 65.64; H, 8.55; N, 5.95.
2-Cyclohexenyl-N-(2-hydroxyethyl)acrylamide (8aa): Oil, IR (CH2Cl2)
t )
(cmꢀ1
1658 (CO), 3354 (NH); 1H NMR d (ppm) (500 MHz, CDCl3): 1.54–1.56 [m, 4H,
cyclohexenyl], 2.07–2.10 [m, 4H cyclohexenyl], 3.43 (q, 2H, NCH2, J = 6.10 Hz),