Supporting Information
Heterogeneous synthesis of indole-2-carboxylic esters via Bischler
cyclization under the catalysis of organosulfonic acid-functionalized
SBA-15 silicas
Nan Sun,* Xiayue Zhu, Jiali Luo, Weimin Mo, Baoxiang Hu, Xinquan Hu*
College of Chemical Engineering, Zhejiang University of Technology, Hangzhou 310014,
China
E-mail: sunnan@zjut.edu.cn and xinquan@zjut.edu.cn
Table of Contents
Procedure for the preparation of the catalysts…………………………..……….………..S-2
Preparation of 4-nitrobenzyl 3-hydroxy-2-(N-methyl-N-arylamino)-2-enoates 1a-1o..…S-3
Characterization data for indole-2-carboxylic PNB esters (2a-2i and 2l-2o)…………..…S-9
Proton NMR and 13 C NMR Spectra ................................………………........…….........S-14
S-1
Procedure for the preparation of the catalysts
Pure siliceous mesoporous SBA-15 catalyst (SBA-15) was prepared with Pluronic 123 as
template agent and tetraethoxysilane (TEOS) as silicon source according to the reported
procedure.1 A typical preparative procedure was as follows: 4 g of Pluronic 123 was
dissolved in 125 g of 1.9 M HCl aqueous solution under room temperature, followed by
adding 8.7 g of TEOS. The resulting mixture was stirred at 40 oC for 20 h and then aged at
100 oC for an additional 24 h under static condition. The formed solid was collected by
filtration, washed with ethanol and dried at room temperature overnight. The template was
removed from the above as-synthesized material by refluxing in ethanol (400 mL) for 24 h.
And then, the resulted SBA-15 was washed with ethanol and dried at 70 oC overnight.
Phenylsulfonic acid functionalized SBA-15 catalyst (SBA-15-PhSO3H) was prepared by
co-condensation method according to the procedure described in the literature.2 The
procedure was similar to that of SBA-15 except that TEOS and CSPTMS were used as
mixed silicon sources and the amount of CSPTMS was fixed to 10% of total silicon atoms.
CSPTMS was added after pre-hydrolysis of TEOS at 40 oC for 45 min. The molar
composition of the mixture for 4 g of Pluronic 123 was: 0.0369 TEOS, 0.0041 CSPTMS,
0.24 HCl and 6.67 H2O.
Propylsulfonic acid functionalized SBA-15 catalyst (SBA-15-PrSO3H) was similarly
prepared in one-pot process by co-condensation method according to the procedure
described in literature.3 In this case, TEOS and MPTMS were used as mixed silicon sources
and the amount of MPTMS was also fixed to 10% of total silicon atoms. After
pre-hydrolysis of TEOS at 40 oC for 45 min, MPTMS and 40% H2O2 were added at once.
The molar composition of the mixture for 4 g of Pluronic 123 was: 0.0369 TEOS, 0.0041
MPTMS, 0.0246 H2O2, 0.24 HCl and 6.67 H2O.
S-2
References:
1. Zhao DY, Huo QS, Feng JL, Chmelka BF, Stucky GD (1998) J Am Chem Soc 120:6024.
2. Melero JA, Stucky GD, van Grieken R, Morales G (2002) J Mater Chem 12:1664.
3. Margolese D, Melero JA, Christiansen SC, Chmelka BF, Stucky GD (2000) Chem Mater
12:2448.
Preparation of 4-nitrobenzyl 3-hydroxy-2-(N-methyl-N-arylamino)-2-enoates 1a-1o
A 25 mL round-bottomed flask was successively charged with N-methyl anilines 3 (2
mmol), and 4-nitrobenzyl α-diazo-β-keto-carboxylates 4 (2 mmol), Cu(TFA)2 (0.02 mmol)
and toluene (10 mL). After the addition, the mixture was heated to reflux for 20-30 minutes
until the reaction was completed based on HPLC determination. In the course of the
reaction, a significant amount of N2 gas was released. Then the mixture was cool to room
temperature and evaporated in vacuo. The residual was finally purified by flash column
chromatography on SiO2 (petroleum ether/ethyl acetate) to afford the desired 4-nitrobenzyl
3-hydroxy-2-(N-methyl-N-arylamino)-2-enoates.
Table 1S Preparation of 4-nitrobenzyl 3-hydroxy-2-(N-methyl-N-arylamino)-2-enoates
from N-methyl anilines and 4-nitrobenzyl α-diazo-β-keto-carboxylatesa
H
N
R1
O
R2
+
N2
3
CO2PNB
Cu(TFA)2
Toluene, reflux
4
HO
R1
N
1
PNB: 4-Nitro Benzyl
S-3
R2
CO2PNB
Entry
3 (R1)
4 (R2)
Product
1
Yieldb (%)
1a
83
1b
100
1c
87
1d
73
1e
90
1f
93
1g
82
1h
69
1i
76
HO
1
3a (H)
4a (Me)
N
O
2
3b (4-OMe)
CO2PNB
HO
4a (Me)
N
CO2PNB
HO
3
3c (4-Me)
4a (Me)
N
CO2PNB
HO
4
3d (2-Me)
4a (Me)
N
CO2PNB
HO
5
3e (3-Me)
4a (Me)
N
F
6
3f (4-F)
HO
4a (Me)
N
Cl
7
3g (4-Cl)
CO2PNB
CO2PNB
HO
4a (Me)
N
CO2PNB
HO
8
3h (2-Cl)
4a (Me)
N
CO2PNB
Cl
Br
9
3i (4-Br)
4a (Me)
HO
N
S-4
CO2PNB
F3C
10
3j (4-CF3)
4a (Me)
N
NC
11
3k (4-CN)
HO
CO2PNB
1j
72
1k
71
1l
88
1m
93
1n
89
1o
80
HO
4a (Me)
N
CO2PNB
HO
12
3a (H)
4b (Et)
N
CO2PNB
HO
13
3a (H)
4c ((CH)2CH3)
N
CO2PNB
HO
14
3a (H)
4d ((CH(CH3)2)
N
CO2PNB
HO
15
3a (H)
4e (Ph)
N
a
CO2PNB
Reaction conditions: N-methyl anilines 3 (2 mmol) and 4-nitrobenzyl α-diazo-β-ketocarboxylates 4 (2 mmol), Cu(TFA)2 (0.02 mmol) and toluene (10 mL) at refluxing
temperature for 20-30 minutes.
b
Isolated yield.
4-Nitrobenzyl 3-hydroxy-2-((N-methyl-N-phenyl)amino)but-2-enoate (1a):
Yield: 83%, yellowish solid, mp: 99.2 oC; 1H NMR (500 MHz, CDCl3): δ = 2.07 (3H, s,
CH3), 3.08 (3H, s, CH3), 5.07-5.37 (2H, dd, J1 = 14.0 Hz, J2 = 132.2 Hz, CH2), 6.67-8.07
(9H, m, Ar-H), 12.01 (1H, s, OH); 13C NMR (125 MHz, CDCl3): δ = 17.6, 39.0, 64.4, 110.9,
112.3, 117.6, 123.6, 127.5, 129.3, 143.0, 147.5, 149.2, 171.3, 177.1; ESI-HRMS m/z calcd
for C18H18N2NaO5 [M+Na]+ 365.1113, found 365.1101.
S-5
4-Nitrobenzyl 3-hydroxy-2-(N-methyl-N-(4-methoxyphenyl)amino)but-2-enoate (1b):
Yield: 100%, light brown solid, mp: 135.5 oC; 1H NMR (500 MHz, CDCl3): δ = 2.08 (3H, s,
CH3), 3.04 (3H, s, CH3), 3.80 (3H, s, CH3), 5.08-5.35 (2H, dd, J1 = 14.0 Hz, J2 = 122.0 Hz,
CH2), 6.60-8.08 (8H, m, Ar-H), 11.99 (1H, s, OH); 13C NMR (125 MHz, CDCl3): δ = 36.4,
55.4, 65.4, 114.6, 123.6, 128.1, 129.1, 133.5, 141.5, 147.8, 159.5, 161.3, 162.3; ESI-HRMS
m/z calcd for C19H19N2O6 [M-H]- 371.1243, found 371.1236.
4-Nitrobenzyl 3-hydroxy-2-(N-methyl-N-(4-methylphenyl)amino)but-2-enoate (1c):
Yield: 87%, yellowish solid, mp: 98.7 oC; 1H NMR (500 MHz, CDCl3): δ = 2.06 (3H, s,
CH3), 2.32 (3H, s, CH3), 3.05 (3H, s, CH3), 5.09-5.35 (2H, dd, J1 = 14.0 Hz, J2 = 114.2 Hz,
CH2), 6.58-8.08 (8H, m, Ar-H), 11.99 (1H, s, OH); 13C NMR (125 MHz, CDCl3): δ = 17.5,
20.3, 39.1, 64.4, 111.0, 112.3, 123.5, 126.6, 127.6, 129.8, 143.1, 147.0, 147.5, 171.4, 177.0;
ESI-HRMS m/z calcd for C19H20N2NaO5 [M+Na]+ 379.1270, found 379.1272.
4-Nitrobenzyl 3-hydroxy-2-(N-methyl-N-(2-methylphenyl)amino)but-2-enoate (1d):
Yield: 73%, yellowish solid, mp: 134.2 oC; 1H NMR (500 MHz, CDCl3): δ = 2.10 (3H, s,
CH3), 2.12 (3H, s, CH3), 3.06 (3H, s, CH3), 5.04-5.38 (2H, dd, J1 = 12.1 Hz, J2 = 156.2 Hz,
CH2), 6.87-8.10 (8H, m, Ar-H), 12.01 (1H, s, OH); 13C NMR (125 MHz, CDCl3): δ = 18.3,
20.2, 41.9, 64.6, 113.4, 117.7, 120.5, 123.6, 126.6, 127.87, 127.97, 132.2, 142.9, 147.5,
149.4, 171.5, 175.3; ESI-HRMS m/z calcd for C19H21N2O5 [M+H]+ 357.1450, found
357.1457.
4-Nitrobenzyl 3-hydroxy-2-(N-methyl-N-(3-methylphenyl)amino)but-2-enoate (1e):
Yield: 90%, yellowish solid, mp: 120.4 oC; 1H NMR (500 MHz, CDCl3): δ = 2.06 (3H, s,
CH3), 2.32 (3H, s, CH3), 3.06 (3H, s, CH3), 5.08-5.37 (2H, dd, J1 = 13.9 Hz, J2 = 132.7 Hz,
CH2), 6.48-8.07 (8H, m, Ar-H), 12.00 (1H, s, OH); 13C NMR (125 MHz, CDCl3): δ = 17.6,
21.9, 39.1, 64.4, 109.6, 111.0, 113.0, 118.5, 123.6, 127.6, 129.2, 139.0, 143.1, 147.5, 149.3,
S-6
171.3, 177.0; ESI-HRMS m/z calcd for C19H21N2O5 [M+H]+ 357.1450, found 357.1461.
4-Nitrobenzyl 3-hydroxy-2-(N-methyl-N-(4-fluorophenyl)amino)but-2-enoate (1f):
Yield: 93%, yellowish solid, mp: 105.0 oC; 1H NMR (500 MHz, CDCl3): δ = 2.07 (3H, s,
CH3), 3.05 (3H, s, CH3), 5.11-5.33 (2H, dd, J1 = 13.8 Hz, J2 = 94.1 Hz, CH2), 6.57-8.11 (8H,
m, Ar-H), 12.00 (1H, s, OH);
13
C NMR (125 MHz, CDCl3): δ = 17.5, 39.4, 64.5, 111.0,
112.96 (d, J = 7.1 Hz), 115.6 (d, J = 21.9 Hz), 123.6, 127.6, 142.9, 145.7 (d, J = 1.8 Hz),
147.6, 156.0 (d, J = 234.5 Hz), 171.2, 177.2; ESI-HRMS m/z calcd for C18H17FN2NaO5
[M+Na]+ 383.1019, found 383.1011.
4-Nitrobenzyl 3-hydroxy-2-(N-methyl-N-(4-chlorophenyl)amino)but-2-enoate (1g):
Yield: 82%, yellowish solid, mp: 122.9 oC; 1H NMR (500 MHz, CDCl3): δ = 2.05 (3H, s,
CH3), 3.06 (3H, s, CH3), 5.12-5.32 (2H, dd, J1 = 13.7 Hz, J2 = 86.6 Hz, CH2), 6.57-8.12
(8H, m, Ar-H), 12.01 (1H, s, OH); 13C NMR (125 MHz, CDCl3): δ = 17.5, 39.2, 64.6, 110.6,
113.4, 122.5, 123.6, 127.7, 129.0, 142.8, 147.6, 147.9, 171.0, 177.2; ESI-HRMS m/z calcd
for C18H17ClN2NaO5 [M+Na]+ 399.0724, found 399.0715.
4-Nitrobenzyl 3-hydroxy-2-(N-methyl-N-(2-chlrorophenyl)amino)but-2-enoate (1h):
Yield: 69%, yellowish solid, mp: 130.4 oC; 1H NMR (500 MHz, CDCl3): δ = 2.10 (3H, s,
H3), 3.09 (3H, s, CH3), 5.08-5.39 (2H, dd, J1 = 13.6 Hz, J2 = 139.9 Hz, CH2), 6.84-8.12 (8H,
m, Ar-H), 12.07 (1H, s, OH);
13
C NMR (125 MHz, CDCl3): δ = 18.4, 41.9, 64.6, 112.6,
119.3, 121.1, 123.6, 123.9, 127.3, 128.1, 131.6, 142.9, 147.0, 147.6, 171.1, 176.3;
ESI-HRMS m/z calcd for C18H17ClN2O5 [M+H]+ 377.0904, found 377.0904.
4-Nitrobenzyl 3-hydroxy-2-(N-methyl-N-(4-bromophenyl)amino)but-2-enoate (1i):
Yield: 76%, yellowish solid, mp: 144.3 oC; 1H NMR (500 MHz, CDCl3): δ = 2.04 (3H, s,
CH3), 3.05 (3H, s, CH3), 5.12-5.32 (2H, dd, J1 = 13.8 Hz, J2 = 88.4 Hz, CH2), 6.53-8.13
S-7
(8H, m, Ar-H), 12.01 (1H, s, OH); 13C NMR (125 MHz, CDCl3): δ = 17.5, 39.2, 64.6, 109.7,
110.6, 114.0, 123.7, 127.7, 131.9, 142.8, 147.6, 148.3, 170.9, 177.1; ESI-HRMS m/z calcd
for C18H17BrN2NaO5 [M+Na]+ 443.0219, found 443.0198.
4-Nitrobenzyl 3-hydroxy-2-(N-methyl-N-(4-trifluorophenyl)amino)but-2-enoate (1j):
Yield: 72%, white solid, mp: 144.1 oC; 1H NMR (500 MHz, CDCl3): δ = 2.04 (3H, s, CH3),
3.12 (3H, s, CH3), 5.14-5.32 (2H, dd, J1 = 13.7 Hz, J2 = 73.5 Hz, CH2), 6.69-8.10 (8H, m,
Ar-H), 12.05 (1H, s, OH); 13C NMR (125 MHz, CDCl3): δ = 17.5, 39.2, 64.7, 110.2, 111.8,
119.3 (q, J = 32.4 Hz,), 123.6, 124.9 (q, J = 268.8 Hz), 126.5, 127.8, 142.6, 147.6, 151.6,
170.7, 177.2; ESI-HRMS m/z calcd for C19H18F3N2O5 [M+H]+ 411.1168, found 411.1163.
4-Nitrobenzyl 3-hydroxy-2-(N-methyl-N-(4-cyanophenyl)amino)but-2-enoate (1k):
Yield: 71%, yellowish solid, mp: 129.7 oC; 1H NMR (500 MHz, CDCl3): δ = 2.01 (3H, s,
CH3), 3.13 (3H, s, CH3), 5.24 (2H, s, CH2), 6.66-8.15 (8H, m, Ar-H), 12.07 (1H, s, OH);
C NMR (125 MHz, CDCl3): δ = 17.6, 39.3, 65.0, 99.8, 109.7, 112.2, 120.0, 123.7, 127.9,
13
133.6, 142.5, 147.7, 152.1, 170.5, 177.3; ESI-HRMS m/z calcd for C19H17N3NaO5 [M+Na]+
390.1066, found 390.1053.
4-Nitrobenzyl 3-hydroxy-2-((N-methyl-N-phenyl)amino)pent-2-enoate (1l)
Yield: 88%, yellowish solid, mp: 101.9 oC; 1H NMR (500 MHz, CDCl3): δ = 1.16 (3H, t, J
= 7.6 Hz, CH3), 2.43 (2H, d, J = 7.6 Hz, CH2), 3.08 (3H, s, CH3), 5.06-5.37 (2H, dd, J1 =
14.0 Hz, J2 = 139.0 Hz, CH2), 6.68-8.06 (9H, m, Ar-H), 12.11 (1H, s, OH); 13C NMR (125
MHz, CDCl3): δ = 10.5, 24.3, 39.5 64.4, 110.0, 112.4, 117.5, 123.6, 127.5, 129.2, 143.1,
147.4, 149.5, 171.4, 181.0; ESI-HRMS m/z calcd for C19H21N2O5 [M+H]+ 357.1450, found
357.1448.
4-Nitrobenzyl 3-hydroxy-2-((N-methyl-N-phenyl)amino)hex-2-enoate (1m):
S-8
Yield: 93%, Yellowish solid, mp: 81.3 oC; 1H NMR (500 MHz, CDCl3): δ = 0.95 (3H, t, J =
7.5 Hz, CH3), 1.66 (2H, q, J = 7.5 Hz, CH2), 2.37-2.40 (2H, m, CH2), 3.08 (3H, s, CH3),
5.05-5.37 (2H, dd, J1 = 14.0 Hz, J2 = 144.8 Hz, CH2), 6.68-8.06 (9H, m, Ar-H), 12.11 (1H,
s, OH); 13C NMR (125 MHz, CDCl3): δ = 14.1, 19.5, 32.8, 39.6, 64.4, 110.7, 112.4, 117.6,
123.6, 127.5, 129.2, 149.5, 171.4, 180.1; ESI-HRMS m/z calcd for C20H23N2O5 [M+H]+
371.1607, found 371.1602.
4-Nitrobenzyl 3-hydroxy-4-methyl-2-((N-methyl-N-phenyl)amino)pent-2-enoate (1n):
Yield: 89%, yellowish solid, mp: 137.2 oC; 1H NMR (500 MHz, CDCl3): δ = 1.11 (3H, d, J
= 6.9 Hz, CH3), 1.8 (3H, d, J = 6.9 Hz, CH3), 3.02-3.05 (1H, m, CH), 3.09 (3H, s, CH3),
5.05-5.37 (2H, dd, J1 = 14.0 Hz, J2 = 146.0 Hz, CH2), 6.68-8.06 (9H, m, Ar-H), 12.1 (1H, s,
OH);
13
C NMR (125 MHz, CDCl3) δ = 19.2, 19.6, 29.1, 39.8, 64.4, 109.0, 112.4, 117.5,
123.6, 127.5, 129.2, 143.1, 147.4, 149.6, 171.6, 183.9; ESI-HRMS m/z calcd for
C20H23N2O5 [M + H]+ 371.1607, found 371.1611.
4-Nitrobenzyl 3-hydroxy-2-((N-methyl-N-phenyl)amino)-3-phenylprop-2-enoate (1o):
Yield: 80%, yellowish solid, mp: 92.4 oC; 1H NMR (500 MHz, CDCl3): δ = 2.96 (3H, s,
CH3), 5.06-5.45 (2H, dd, J1 = 14.0 Hz, J2 = 179.6 Hz, CH2), 6.79-8.06 (14H, m, Ar-H),
12.16 (1H, s, OH); 13C NMR (125 MHz, CDCl3): δ = 39.0, 64.8, 110.9, 112.8, 117.9, 123.5,
127.5, 128.0, 128.3, 129.4, 131.0, 132.8, 142.8, 147.4, 149.4, 171.4, 172.4; ESI-HRMS m/z
calcd for C23H21N2O5 [M+H]+ 405.1450, found 405.1442.
Characterization data for indole-2-carboxylic PNB esters (2a-2i and 2l-2p)
4-Nitrobenzyl 1,3-dimethyl-1H-indole-2-carboxylate (2a)
Yield: 98%, white solid, mp: 140.6 oC; 1H NMR (500 MHz, CDCl3): δ = 2.62 (3H, s, CH3),
4.02 (3H, s, CH3), 5.51 (2H, s, CH2), 7.15-8.28 (8H, m, Ar-H);
13
C NMR (125 MHz,
CDCl3): δ = 11.2, 32.2, 64.8, 110.1, 119.9, 120.9, 121.6, 124.0, 125.8, 127.0, 128.5, 139.1,
S-9
143.5, 147.9, 150.6, 162.5; ESI-HRMS m/z calcd for C18H16N2NaO4 [M+Na]+ 347.1008,
found 347.1006.
4-Nitrobenzyl 1,3-dimethyl-5-methoxy--1H-indole-2-carboxylate (2b)
Yield: 97%, yellowish solid, mp: 143.3 oC; 1H NMR (500 MHz, CDCl3): δ = 2.59 (3H, s,
CH3), 3.90 (3H, s, OCH3), 4.00 (3H, s, CH3), 5.50 (2H, s, CH2), 7.03-8.29 (7H, m, Ar-H);
C NMR (125 MHz, CDCl3): δ = 11.2, 32.3, 55.8, 64.7, 100.8, 111.1, 117.4, 120.6, 123.89,
13
124.27, 127.1, 128.5, 134.7, 143.5, 147.7, 154.3, 162.4; ESI-HRMS m/z calcd for
C19H18N2NaO5 [M+Na]+ 377.1113, found 377.1110.
4-Nitrobenzyl 1,3,5-trimethyl-1H-indole-2-carboxylate (2c)
Yield: 99%, yellowish solid, mp: 127.8 oC; 1H NMR (500 MHz, CDCl3): δ = 2.48 (3H, s,
CH3), 2.60 (3H, s, CH3), 4.00 (3H, s, CH3), 5.50 (2H, s, CH2), 7.21-8.28 (7H, m, Ar-H); 13C
NMR (125 MHz, CDCl3): δ = 11.2, 21.4, 32.2, 64.7, 109.8, 120.11, 120.98, 123.89,
123.097, 127.16, 127.78, 128.4, 129.2, 137.7, 143.5, 147.7, 162.5; ESI-HRMS m/z calcd
for C19H18N2NaO4 [M+Na]+ 361.1164, found 361.1174.
4-Nitrobenzyl 1,3,7-trimethyl-1H-indole-2-carboxylate (2d)
Yield: 97%, yellowish solid, mp: 130.7 oC; 1H NMR (500 MHz, CDCl3): δ = 2.57 (3H, s,
CH3), 2.80 (3H, s, CH3), 4.24 (3H, s, CH3), 5.50 (2H, s, CH2), 7.02-8.28 (7H, m, Ar-H); 13C
NMR (125 MHz, CDCl3): δ = 11.2, 20.8, 34.8, 64.8, 118.9, 120.1, 121.91, 122.01, 123.9,
125.2, 128.02, 128.49, 128.70, 138.9, 143.4, 147.8, 162.5; ESI-HRMS m/z calcd for
C19H18N2NaO4 [M+Na]+ 361.1164, found 361.1147.
4-Nitrobenzyl 1,3,4-trimethyl-1H-indole-2-carboxylate and 4-Nitrobenzyl 1,3,6-trimethyl1H-indole-2-carboxylate (2e)
Yield: 98%, yellowish solid, mp: 112.0 oC; 1H NMR (500 MHz, CDCl3): for 4-Nitrobenzyl
S-10
1,3,4-trimethyl-1H-indole-2-carboxylate δ = 2.76 (1.75H, s, CH3), 2.83 (1.75H, s, CH3),
3.96 (1.75H, s, CH3), 5.510 (1.17H, s, CH2), 6.85-8.29 (4.1H, m, Ar-H); for 4-Nitrobenzyl
1,3,6-trimethyl- 1H-indole-2-carboxylate δ = 2.52 (1.25H, s, CH3), 2.60 (1.25H, s, CH3),
3.99 (1.25H, s, CH3), 5.497 (0.83H, s, CH2), 6.85-8.29 (2.9H, m, Ar-H); 13C NMR (125
MHz, CDCl3): δ = 11.3, 13.4, 21.1, 22.2, 32.03, 32.26, 64.61, 64.79, 108.1, 109.7, 120.5,
121.76, 121.81, 122.08, 122.47, 123.9, 124.2, 125.05, 125.54, 125.68, 128.42, 128.49,
133.7, 136.1, 139.57, 139.60, 143.38, 143.59, 147.8, 162.53, 162.58; EI-HRMS m/z calcd
for C19H18N2O4 [M]+ 338.1267, found 338.1270.
4-Nitrobenzyl 1,3-dimethyl-5-fluoro-1H-indole-2-carboxylate (2f)
Yield: 91%, white solid, mp: 156.4 oC; 1H NMR (500 MHz, CDCl3): δ = 2.57 (3H, s, CH3),
4.02 (3H, s, CH3), 5.51 (2H, s, CH2), 7.13-8.30 (7H, m, Ar-H);
13
C NMR (125 MHz,
CDCl3): δ = 11.2, 32.4, 64.9, 105.1 (J = 22.9 Hz), 111.1 (J = 9.2 Hz), 114.8 (J = 26.7 Hz),
121.0 (J = 5.5 Hz), 123.9, 125.3, 127.0 (J = 9.3 Hz), 128.5, 135.7, 143.3, 147.8, 157.8 (J =
235.5 Hz), 162.3; ESI-HRMS m/z calcd for C18H15FN2NaO4 [M+Na]+ 365.0914, found
365.0921.
4-Nitrobenzyl 5-chloro-1,3-dimethyl-1H-indole-2-carboxylate (2g)
Yield: 90%, white solid, mp: 160.6 oC; 1H NMR (500 MHz, CDCl3): δ = 2.57 (3H, s, CH3),
4.01 (3H, s, CH3), 5.51 (2H, s, CH2), 7.28-8.29 (7H, m, Ar-H);
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C NMR (125 MHz,
CDCl3): δ = 11.1, 32.4, 64.9, 111.3, 120.17, 120.72, 124.0, 125.10, 125.72, 126.2, 127.9,
128.6, 137.3, 143.2, 147.9, 162.2; EI-HRMS m/z calcd for C18H15ClN2O4 [M]+ 358.0720,
found 358.0722.
4-Nitrobenzyl 7-chloro-1,3-dimethyl-1H-indole-2-carboxylate (2h)
Yield: 89%, white solid, mp: 147.5 oC; 1H NMR (500 MHz, CDCl3): δ = 2.56 (3H, s, CH3),
4.36 (3H, s, CH3), 5.51 (2H, s, CH2), 7.03-8.30 (7H, m, Ar-H);
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C NMR (125 MHz,
CDCl3): δ = 11.1, 34.7, 65.1, 117.6, 119.7, 120.4, 121.7, 124.0, 126.4, 127.6, 128.6, 130.2,
134.8, 143.1, 147.9, 162.0; ESI-HRMS m/z calcd for C18H15ClN2NaO4 [M+Na]+ 381.0618,
found 381.0630.
4-Nitrobenzyl 5-bromo-1,3-dimethyl-1H-indole-2-carboxylate (2i)
Yield: 93%, white solid, mp: 162.9 oC; 1H NMR (500 MHz, CDCl3): δ = 2.57 (3H, s, CH3),
4.01 (3H, s, CH3), 5.51 (2H, s, CH2), 7.24-8.30 (7H, m, Ar-H);
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C NMR (125 MHz,
CDCl3): δ = 11.1, 32.4, 65.0, 111.7, 113.1, 120.6, 123.39, 123.99, 124.9, 128.58, 128.63,
130.6, 137.6, 143.2, 147.9, 162.2; APCI-HRMS m/z calcd for C18H14BrN2O4 [M-H]401.0137, found 401.0119.
4-Nitrobenzyl 3-ethyl-1-methyl-1H-indole-2-carboxylate (2l)
Yield: 95%, yellowish solid, mp: 102.6 oC; 1H NMR (500 MHz, CDCl3): δ = 1.24 (3H, t, J
= 7.5 Hz, CH3), 3.11 (2H, q, J = 7.5 Hz, CH2), 4.02 (3H, s, CH3), 5.51 (2H, s, CH2),
7.15-8.29 (8H, m, Ar-H);
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C NMR (125 MHz, CDCl3): δ = 15.9, 18.9, 32.2, 64.9, 110.2,
119.98, 120.80, 123.32, 123.93, 125.7, 126.2, 128.23, 128.62, 139.2, 143.3, 147.8, 162.4;
ESI-HRMS m/z calcd for C19H18N2NaO4 [M+Na]+ 361.1164, found 361.1149.
4-Nitrobenzyl 1-methyl-3-propyl-1H-indole-2-carboxylate (2m)
Yield: 97%, yellowish solid, mp: 80.7 oC; 1H NMR (500 MHz, CDCl3): δ = 0.91 (3H, t, J =
7.5 Hz, CH3), 1.58-1.66 (2H, m, CH2), 3.03-3.06 (2H, m, CH2), 4.03 (3H, s, CH3), 5.49 (2H,
s, CH2), 7.14-8.30 (8H, m, Ar-H); 13C NMR (125 MHz, CDCl3): δ = 14.3, 24.7, 27.6, 32.2,
64.9, 110.2, 119.9, 121.0, 123.67, 123.92, 125.7, 126.61, 126.70, 128.8, 139.1, 143.2, 147.9,
162.4; EI-HRMS m/z calcd for C20H20N2O4 [M]+ 352.1423, found 352.1434.
4-Nitrobenzyl 1-methyl-3-iso-propyl-1H-indole-2-carboxylate (2n)
Yield: 91%, yellowish solid, mp: 111.7 oC; 1H NMR (500 MHz, CDCl3): δ = 1.47-1.49 (6H,
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d, J = 7.0 Hz, CH3), 3.94 (3H, s, CH3), 3.97-4.01 (1H, m, CH), 5.52 (2H, s, CH2), 7.11-8.30
(8H, m, Ar-H); 13C NMR (125 MHz, CDCl3): δ = 23.1, 26.4, 32.2, 65.0, 110.5, 119.5, 122.9,
123.35, 123.93, 124.95, 125.14, 128.5, 131.5, 139.5, 143.2, 147.8, 162.6; ESI-HRMS m/z
calcd for C20H20N2NaO4 [M+Na]+ 375.1321, found 375.1313.
4-Nitrobenzyl 1-methyl-3-phenyl-1H-indole-2-carboxylate (2o)
Yield: 87%, yellow solid, mp: 142.3 oC; 1H NMR (500 MHz, CDCl3): δ = 4.13 (3H, s, CH3),
5.26 (2H, s, CH2), 6.94-8.06 (13H, m, Ar-H); 13C NMR (125 MHz, CDCl3): δ = 32.0, 64.8,
110.1, 120.9, 121.8, 123.49, 123.80, 125.48, 125.83, 126.9, 127.1, 127.9, 128.1, 130.5,
135.0, 138.7, 142.6, 147.4, 162.2; ESI-HRMS m/z calcd for C23H18N2NaO4 [M+Na]+
409.1164, found 409.1166.
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Proton NMR and 13 C NMR Spectra
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