Diethyl Azodicarboxylate-promoted Oxidative Coupling Reaction of N-Phenyl Tetrahydroisoquinoline with β-Keto Acids

Full text of DOI:10.1002/bkcs.11307

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DOI: 10.1002/bkcs.11307
BULLETIN OF THE
Y. H. Kim et al.
KOREAN CHEMICAL SOCIETY
Diethyl Azodicarboxylate-promoted Oxidative Coupling Reaction
of N-Phenyl Tetrahydroisoquinoline with β-Keto Acids
*
Yong Hwan Kim, Min Gyun Gil, and Dae Young Kim
Department of Chemistry, Soonchunhyang University, Chungnam 31538, Korea.
*E-mail: dyoung@sch.ac.kr
Received July 14, 2017, Accepted September 23, 2017
Keywords: Oxidative coupling reaction, Diethyl azodicarboxylate, Mannich-type reaction,
Tetrahydroisoquinolines
The direct oxidative cross-dehydrogenative coupling (CDC)
we report C1-phenacylmethylation of THIQs with β-keto
acids using DEAD as the oxidant.
of two C H bonds can be an atom-economic and environ-
mentally benign strategy the field of organic synthesis.1
Since the pioneering work on CDC demonstrated by Mura-
hashi and Li groups on oxidative iminium ions formation
from tetrahydroisoquinoline (THIQ) derivatives,2 various
nucleophiles have been utilized to combine the iminium
intermediates to form new C C bonds using numerous oxi-
dation methods.3 Several groups reported the efficient CDC
of C(sp3) H with fluorinated active methins, Grignard
reagents, and allyl silanes by using diethyl azodicarboxylate
(DEAD) as the oxidant.4 Recently, Akiyama and coworkers
have reported DEAD-promoted phenacylmethylation to
form C1-phenacylmethylated THIQ derivatives from the
reaction of silyl enol ethers with N-phenyl terahydroisoqui-
nolines (Scheme 1(a)).3g The decarboxylative additions of
β-keto acids as ketones or ketone enolate equivalents have
received much attention.5 We envisioned the decarboxyla-
tive Mannich-type reaction of the β-keto acids to the C1-
acylmethylated THIQs through DEAD-promoted oxidation
(Scheme 1(b)).
To determine optimum conditions for the DEAD-
promoted oxidative coupling reaction of THIQs, we exam-
ined the CDC reaction of N-phenyl tetrahydroisoquinoline
(1) with 3-oxo-3-phenylpropanoic acid (2a). This reaction
was initiated with N-phenyl tetrahydroisoquinoline (1) with
DEAD in toluene at room temperature for 0.5 h, subse-
quent addition of 3-oxo-3-phenylpropanoic acid (2a) at
room temperature gave the corresponding coupling product
3a in 43% yield (Table 1, entry 1). A survey of the reaction
media indicated that common solvents (Table 1, entries
1–10), such as toluene, benzene, dichloromethane, chloro-
form, THF, ethyl acetate, acetonitrile, DMF, DMSO, and
ethanol, were well tolerated in this conjugate addition.
Among the solvents probed, the best result was achieved
when the reaction was conducted in acetonitrile (Table 1,
entry 7, 77% yield).
With the optimal reaction conditions in hand, we investi-
gated the scope of this DEAD-promoted oxidative coupling
reaction of N-phenyl tetrahydroisoquinoline (1) with
3-oxoalkanoic acid 2 in acetonitrile at room temperature.
As shown in Table 2, various 3-oxoalkanoic acids 2 with
electron-donating or electron-withdrawing aryl groups furn-
ished the corresponding coupling products with moderate
to high yields (60–80%, Table 2, entries 1–10). The
naphthyl- and heteroaryl-substituted β-keto acids provided
the desired products with high yields (71–80%, Table 2,
entries 11, 12). In addition, alkyl-substituted β-keto acid
2m also afforded the corresponding product, but with rela-
tively lower yield (55%, Table 2, entry 13).
As part of a research program related to the development
of internal redox reaction, we recently reported the intramo-
lecular redox reactions via C H bond activation.6 Herein,
In order to check the synthetic viability of this oxidative
coupling system, we performed the DEAD-promoted cou-
pling reaction at the gram scale. As shown in Scheme 2,
when N-phenyl tetrahydroisoquinoline (1) was treated with
3-oxo-3-phenylpropanoic acid (2a) the optimal reaction
conditions, the reaction proceeded smoothly to afford the
desired 1-phenyl-2-(2-phenyl-1,2,3,4-tetrahydroisoquinolin-
1-yl)ethanone (3a) with 75% yield.
In conclusion, we have presented a mild and efficient
process for the oxidative coupling reaction of N-phenyl
Scheme 1. C1-phenacylmethylation of THIQs.
Bull. Korean Chem. Soc. 2017
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Table 1. Optimization of the reaction conditions.a
Scheme 2. Gram-scale oxidative coupling reaction of N-phenyl
tetrahydroisoquinoline
acid (2a).
(1)
with
3-oxo-3-phenylpropanoic
Entry
Solvent
PhMe
PhH
CH2Cl2
CHCl3
THF
EtOAc
CH3CN
DMF
DMSO
EtOH
Time (h)
Yieldb (%)
1
2
3
4
5
6
7
8
9
10
a
20
20
20
20
20
20
6
10
20
20
43
38
65
61
40
47
77
63
43
42
THIQ compounds. Further studies on oxidative coupling
reaction of other nucleophiles and on the more detailed
investigation of the reaction mechanisms are currently
underway in our laboratories.
Experimental
General Procedure for the DEAD-promoted Oxidative
Coupling Reaction of N-Phenyl Tetrahydroisoquinoline
with β-Keto Acids. To a stirred solution of N-phenyl tetra-
hydroisoquinoline (1, 63 mg, 0.3 mmol), in acetonitrile
(3 mL) was added DEAD (0.33 mmol) under N2 atmosphere.
The reaction mixture was stirred at room temperature for
0.5 h. Then, 3-oxoalkanoic acid 2 (0.45 mmol) was added
and the mixture was further stirred for 3–15 h at room tem-
perature. After the reaction was completed, the mixture was
directed purified by column chromatography on silica gel
(ethyl acetate:n-hexane = 1:20) to afford the C1-
acylmethylated THIQs 3.
Reactions were carried out N-phenyl tetrahydroisoquinoline (1,
0.3 mmol), DEAD (0.33 mmol) in solvent (3 mL) at room
temperature for 0.5 h, then, 3-oxo-3-phenylpropanoic acid (2a,
0.45 mmol) was added.
b
Isolated yield.
Table 2. Variation of substrates 2.a
1-Phenyl-2-(2-phenyl-1,2,3,4-tetrahydroisoquinolin-1-yl)
ethanone (3a). Pale yellow solid; yield = 77%; mp
o
1
106–107 C (lit.3 mp 104–106ꢀC); H NMR (400 MHz,
CDCl3): δ 7.86 (d, J = 7.5 Hz, 2H), 7.54 (t, J = 7.6 Hz,
1H), 7.42 (t, J = 7.6 Hz, 2H), 7.29–7.10 (m, 6H), 7.00 (d,
J = 8.4 Hz, 2H), 6.77 (d, J = 7.5 Hz, 1H), 5.68 (dd,
J = 6.8 Hz, 5.1 Hz, 1H), 3.70–3.60 (m, 2H), 3.60 (dd,
J = 16.4, 5.1 Hz, 1H), 3.40 (dd, J = 16.8, 7.2 Hz, 1H),
3.13 (m, 1H), 2.94 (m, 1H); 13C NMR (100 MHz, CDCl3):
δ 198.6, 148.7, 138.3, 137.3, 134.4, 133.0, 129.3, 128.5,
128.1, 127.1, 126.7, 126.2, 117.9, 114.3, 55.0, 45.4, 42.2,
27.5; EI-MS: m/z = 327.2 [M]+.
Entry
2, R
Time (h)
Yieldb (%)
1
2
3
4
5
6
7
8
Ph
6
8
3
3
7
8
9
9
10
13
10
6
3a, 77
3b, 71
3c, 63
3d, 75
3e, 68
3f, 64
3g, 75
3h, 60
3i, 65
3j, 67
3k, 80
3l, 71
3m, 55
4-F,C6H4
4-Cl,C6H4
4-Br,C6H4
4-OMe,C6H4
4-Me,C6H4
4-NO2,C6H4
3-Me,C6H4
3-Br,C6H4
2-Me,C6H4
2-Naphthyl
2-Thienyl
9
1-(4-Fluorophenyl)-2-(2-phenyl-1,2,3,4-tetrahydroiso-qui-
nolin-1-yl)ethanone (3b). Pale yellow solid; yield = 71%;
mp 78–79ꢀC; 1H NMR (400 MHz, CDCl3): δ 7.85 (dd,
J = 9.0, 5.2 Hz, 2H), 7.25–7.04 (m, 8H), 6.96 (d,
J = 8.4 Hz, 2H), 6.75 (t, J = 7.4 Hz, 1H), 5.63 (dd,
J = 7.4, 5.0 Hz, 1H), 3.69–3.57 (m, 2H), 3.54 (dd,
J = 16.4, 4.8 Hz, 1H), 3.34 (dd, J = 16.2, 7.2 Hz, 1H),
3.15–3.07 (m, 1H), 2.95–2.88 (m, 1H); 13C NMR
(100 MHz, CDCl3): δ 197.1, 167.0, 164.4, 148.7, 138.4,
134.5, 133.7, 130.8, 130.7 (d, J = 9.6 Hz), 129.4, 128.6,
127.1, 127.0 (d, J = 20.0 Hz), 126.3, 118.0, 115.7, 115.6
(d, J = 21.9 Hz), 114.3, 55.2, 45.2, 42.1, 27.5; 19F NMR
(376 MHz, CDCl3) : δ −106; EI-MS: m/z = 345.2 [M]+.
10
11
12
13
a
Benzyl
15
Reactions were carried out N-phenyl tetrahydroisoquinoline (1,
0.3 mmol), DEAD (0.33 mmol) in acetonitrile (3 mL) at room
temperature for 0.5 h, then, 3-oxo-alkanoic acids 2 (0.45 mmol) was
added.
b
Isolated yield.
tetrahydroisoquinoline (1) with 3-oxoalkanoic acids 2 using
DEAD as the oxidant. This process represents a robust
approach for the syntheses of diverse C1-acylmethylated
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1-(4-Chlorophenyl)-2-(2-phenyl-1,2,3,4-tetrahydroisoqui-
nolin-1-yl)ethanone (3c). Pale yellow solid; Yield = 63%;
mp 76–78 oC; 1H NMR (400 MHz, CDCl3): δ 7.79 (d,
J = 8.4 Hz, 2H), 7.40 (d, J = 8.4 Hz, 2H), 7.29–7.14 (m,
6H), 6.98 (d, J = 8.4 Hz, 2H), 6.79 (t, J = 7.6 Hz, 1H),
5.65 (dd, J = 6.8, 5.2 Hz, 1H), 3.70–3.60 (m, 2H), 3.57
(dd, J = 16.4, 4.8 Hz, 1H), 3.37 (dd, J = 16.4, 7.2 Hz,
1H), 3.14 (m, 1H), 2.95 (m, 1H); 13C NMR (100 MHz,
CDCl3): δ 197.5, 148.5, 139.6, 138.2, 135.5, 134.5, 129.5,
129.4, 128.9, 128.6, 127.1, 126.9, 126.3, 118.1, 114.5,
55.3, 45.3, 42.2, 27.5; EI-MS: m/z = 361.1 [M]+.
1-(4-Bromophenyl)-2-(2-phenyl-1,2,3,4-tetrahydroisoqui-
nolin-1-yl)ethanone (3d). Pale yellow solid; yield = 75%;
mp 80–81ꢀC; 1H NMR (400 MHz, CDCl3): δ 7.68 (d,
J = 8.8 Hz, 2H), 7.53 (d, J = 8.4 Hz, 2H), 7.23–7.02 (m,
6H), 6.95 (d, J = 7.5 Hz, 2H), 6.75 (t, J = 7.4 Hz, 1H),
5.61 (dd, J = 7.2, 6.2 Hz, 1H), 3.68–3.56 (m, 2H), 3.53
(dd, J = 16.4, 4.8 Hz, 1H), 3.31 (dd, J = 16.4, 7.6 Hz,
1H), 3.17–3.06 (m, 1H), 2.94–2.87 (m, 1H); 13C NMR
(100 MHz, CDCl3): δ 197.7, 148.6, 138.2, 135.9, 134.4,
131.8, 129.6, 129.3, 128.6, 128.2, 127.0, 126.9, 126.3,
118.1, 114.3, 55.3, 45.2, 42.1, 27.5; EI-MS: m/
z = 405.1 [M]+.
126.9, 126.3, 118.0, 114.3, 55.1, 49.7, 42.0, 27.0; EI-MS:
m/z = 372.1 [M]+.
2-(2-Phenyl-1,2,3,4-tetrahydroisoquinolin-1-yl)-1-(m-tolyl)
ethanone (3h). Pale yellow solid; yield = 60%; mp
103–105ꢀC;1H NMR (400 MHz, CDCl3): δ 7.65–7.63 (m,
2H), 7.34–7.08 (m, 8H), 6.97 (d, J = 8.4 Hz, 2H), 6.75 (t,
J = 7.2 Hz, 1H), 5.66 (dd, J = 6.8, 4.8 Hz, 1H), 3.68–3.60
(m, 2H), 3.56 (dd, J = 16.8, 4.8 Hz, 1H), 3.37 (dd,
J = 16.6, 7.4 Hz, 1H), 3.15–3.08 (m, 1H), 2.96–2.89 (m,
1H), 2.36 (s, 3H); 13C NMR (100 MHz, CDCl3): δ 198.8,
148.7, 138.6, 138.3, 137.2, 134.5, 133.8, 129.3, 128.7,
128.5, 128.4, 127.1, 126.8, 126.2, 125.3, 117.3, 114.2,
54.9, 45.4, 42.1, 27.6, 21.3; HRMS m/z calcd for
C24H24NO [M + H]+: 342.1858; found 342.1855.
1-(3-Bromophenyl)-2-(2-phenyl-1,2,3,4-tetrahydroisoqui-
nolin-1-yl)ethanone (3i). Pale yellow solid; yield = 65%;
1
mp 85–87ꢀC; H NMR (400 MHz, CDCl3): δ 7.95 (s, 1H),
7.74 (d, J = 7.6 Hz, 1H), 7.64 (d, J = 7.6 Hz, 1H),
7.29–7.09 (m, 7H), 6.95 (d, J = 8.0 Hz, 2H), 6.76 (t,
J = 7.2 Hz, 1H), 5.63 (dd, J = 6.8, 4.8 Hz, 1H),
3.69–3.3.59 (m, 2H), 3.55 (dd, J = 16.4, 5.2 Hz, 1H), 3.33
(dd, J = 16.8, 7.2 Hz, 1H), 3.15–3.07 (m, 1H), 2.95–2.89
(m, 1H); 13C NMR (100 MHz, CDCl3): δ 197.3, 148.7,
138.9, 138.2, 135.9, 134.5, 131.2, 130.1, 129.4, 128.6,
127.0, 126.9, 126.6, 126.3, 122.9, 118.2, 114.5, 55.1, 45.4,
42.1, 27.5; HRMS m/z calcd for C23H21BrNO [M + H]+:
406.0807; found 406.0810.
1-(4-Methoxyphenyl)-2-(2-phenyl-1,2,3,4-tetrahydroiso-
quinolin-1-yl)ethanone (3e). Pale yellow solid; yield =
1
68%; mp 99–100ꢀC; H NMR (400 MHz, CDCl3): δ 7.82
(d, J = 8.4 Hz, 2H), 7.23–7.09 (m, 6H), 6.96 (d,
J = 7.6 Hz, 2H), 6.85 (d, J = 6.8 Hz, 2H), 6.73 (t,
J = 7.4 Hz, 1H), 5.64 (dd, J = 7.4, 5.2 Hz, 1H), 3.83 (s,
3H), 3.69–3.56 (m, 2H), 3.50 (dd, J = 16.2, 5.2 Hz, 1H),
3.33 (dd, J = 16.2, 7.2 Hz, 1H), 3.14–3.06 (m, 1H),
2.94–2.88 (m, 1H); 13C NMR (100 MHz, CDCl3): δ 197.0,
163.4, 148.7, 138.6, 134.4, 130.4, 130.3, 129.3, 128.4,
127.1, 126.7, 126.2, 117.7, 114.1, 113.6, 55.4, 55.0, 44.8,
42.0, 27.5; EI-MS: m/z = 357.2 [M]+.
2-(2-Phenyl-1,2,3,4-tetrahydroisoquinolin-1-yl)-1-(o-tolyl)
ethanone (3j). Pale yellow solid; yield = 67%; mp
99–101ꢀC; 1H NMR (400 MHz, CDCl3): δ 7.37 (d,
J = 7.6 Hz, 1H), 7.30 (t, J = 7.4 Hz, 1H), 7.25–7.11 (m,
8H), 6.93 (d, J = 7.6 Hz, 2H), 6.75 (t, J = 7.2 Hz, 1H),
5.60 (t, J = 6.4 Hz, 1H), 3.67–3.54 (m, 2H), 3.48 (dd,
J = 16.2, 5.8 Hz, 1H), 3.30 (dd, J = 16.4, 7.6 Hz, 1H),
3.11–3.03 (m, 1H), 2.88–2.82 (m, 1H), 2.40 (s, 3H); 13C
NMR (100 MHz, CDCl3): δ 202.7, 148.8, 138.4, 138.4,
138.0, 134.5, 131.8, 131.5, 131.1, 129.3, 129.0, 128.7,
128.2, 126.9, 126.8, 126.4, 126.2, 125.5, 118.0, 114.4,
55.3, 48.4, 42.0, 27.2, 20.9; HRMS m/z calcd for
C24H24NO [M + H]+ : 342.1858; found 342.1855.
2-(2-Phenyl-1,2,3,4-tetrahydroisoquinolin-1-yl)-1-(p-tolyl)
ethanone (3f). Pale yellow solid; yield = 64%; mp
102–103ꢀC; 1H NMR (400 MHz, CDCl3): δ 7.88 (d,
J = 7.6 Hz, 2H), 7.25–7.06 (m, 8H), 6.94 (d, J = 8.4 Hz,
2H), 6.73 (d, J = 7.2 Hz, 1H), 5.64 (dd, J = 7.4, 4.8 Hz,
1H), 3.68–3.50 (m, 2H), 3.53 (dd, J = 16.8, 4.8 Hz, 1H),
3.34 (dd, J = 16.8, 7.2 Hz, 1H), 3.14–3.07 (m, 1H),
2.95–2.88 (m, 1H), 2.37 (s, 3H); 13C NMR (100 MHz,
CDCl3): δ 198.2, 143.9, 138.6, 134.8, 134.5, 129.3, 129.2,
128.5, 128.2, 127.1, 126.8, 126.2, 117.8, 114.2, 55.0, 45.2,
42.1, 27.6, 21.6; EI-MS: m/z = 341.2 [M]+.
1-(4-Nitrophenyl)-2-(2-phenyl-1,2,3,4-tetrahydroisoquino-
lin-1-yl)ethanone (3g). Pale yellow solid; yield = 75%; mp
81–83ꢀC; 1H NMR (400 MHz, CDCl3): δ 7.78 (dd,
J = 8.8, 5.6 Hz, 2H), 7.24–7.01 (m, 8H), 6.96 (d,
J = 7.6 Hz, 2H), 6.74 (t, J = 5.8 Hz, 1H), 5.63 (dd,
J = 9.8, 5.2 Hz, 1H), 3.68–3.57 (m, 2H), 3.54 (dd,
J = 16.4, 4.8 Hz, 1H), 3.34 (dd, J = 16.6, 7.2 Hz, 1H),
3.15–3.07 (m, 1H), 2.95–2.88 (m, 1H); 13C NMR
(100 MHz, CDCl3): δ 197.5 148.9, 139.6, 138.0, 135.2,
134.6, 131.7, 130.3, 129.4, 129.3, 128.8, 128.5, 127.0,
1-(Naphthalen-2-yl)-2-(2-phenyl-1,2,3,4-tetrahydroisoqui-
nolin-1-yl)ethanone (3k). Pale yellow solid; yield = 80%;
1
mp 76–78ꢀC; H NMR (400 MHz, CDCl3): δ 8.29 (s, 1H),
7.95 (dd, J = 8.0, 2.0 Hz, 1H), 7.90–7.79 (m, 3H),
7.62–7.45 (m, 2H), 7.25–7.08 (m, 6H), 6.99 (d, J = 8.4 Hz,
2H), 6.74 (t, J = 7.2 Hz, 1H), 5.71 (dd, J = 7.2, 5.6 Hz,
1H), 3.72–3.64 (m, 3H), 3.50 (dd, J = 16.6, 7.6 Hz, 1H),
3.16–3.08 (m, 1H), 2.97–2.91 (m, 1H); 13C NMR
(100 MHz, CDCl3): δ 198.5, 148.7, 138.4, 135.5, 134.5,
132.3, 129.8, 129.5, 129.3, 128.5, 128.4, 127.7, 127.1,
126.8, 126.7, 126.2, 123.8, 117.9, 114.3, 55.1, 45.3, 42.1,
27.5; EI-MS : m/z = 377.2 [M]+.
2-(2-Phenyl-1,2,3,4-tetrahydroisoquinolin-1-yl)-1-(thio-
phen-2-yl)ethanone (3l). Pale yellow solid; yield = 71%;
mp 81–82ꢀC; 1H NMR (400 MHz, CDCl3): δ 7.59 (d,
J = 5.2 Hz, 1H), 7.54 (d, J = 3.2 Hz, 1H), 7.25–7.08 (m,
Bull. Korean Chem. Soc. 2017
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6H), 7.04 (t, J = 4.4 Hz, 1H), 6.98 (d, J = 8.0 Hz, 2H),
6.75 (t, J = 7.4 Hz, 1H), 5.61 (dd, J = 7.2, 6.4 Hz, 1H),
3.69–3.59 (m, 2H), 3.53 (dd, J = 16.0, 5.2 Hz, 1H), 3.28
(dd, J = 15.8, 7.2 Hz, 1H), 3.15–3.08 (m, 1H), 2.94–2.87
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144.6, 138.1, 134.4, 133.9, 132.0, 129.3, 128.5, 128.0,
127.1, 126.8, 126.2, 117.9, 114.3, 55.5, 45.9, 41.9, 29.7,
27.4; EI-MS: m/z = 333.1 [M]+.
1-Phenyl-3-(2-phenyl-1,2,3,4-tetrahydroisoquinolin-1-yl)
propan-2-one (3m). Pale yellow solid; yield = 55%; mp
1
70–72ꢀC; H NMR (400 MHz, CDCl3): δ 7.28–7.21 (m,
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5H), 7.15–7.09 (m, 4H), 7.05–7.03 (m, 2H), 6.92–6.90 (d,
J = 8.4 Hz, 2H), 6.78–6.75 (t, J = 7.2 Hz, 1H), 5.41–5.37
(t, J = 6.4 Hz, 1H) 3.61–3.54 (m, 3H), 3.45–3.39 (m, 1H),
3.11–2.98 (m, 2H), 2.80–2.71 (m, 2H); 13C NMR
(100 MHz, CDCl3) δ 206.76, 148.81, 138.02, 134.51,
133.62, 129.48, 129.30, 128.64, 126.98, 126.90, 126.78,
126.21, 118.20, 114.70, 55.23, 51.17, 48.27, 41.84, 27.02;
EI-MS: m/z = 341.2 [M]+.
Acknowledgments. This research was supported by Soon-
chunhyang University Research Fund and Basic Science
Research Program through the National Research Founda-
tion of Korea (NRF-2016R1D1A1B03933723).
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