A Pd(II)-catalyzed oxidative cyclization for the preparation of aryl-fused six-membered nitrogen heterocycles with 2-acetoxy functionality

Article abstract of DOI:10.1002/cjoc.201200963

A Pd(II)-catalyzed oxidative cyclization of olefinic tosylamides was developed for the preparation of aryl-fused and N-containing six-membered heterocycles. Under optimized conditions the reaction proceeded with high activity and selectivity, with yields

Full text of DOI:10.1002/cjoc.201200963

FULL PAPER
DOI: 10.1002/cjoc.201200963
A Pd(II)-Catalyzed Oxidative Cyclization for the Preparation of
Aryl-Fused Six-Membered Nitrogen Heterocycles with
2-Acetoxy Functionality†
Xiaolei Wang,a Zhengxing Wu,a Xiaowen Zhu,a
Chenghao Ye,a Feng Jiang,b and Wanbin Zhang*,a
a School of Chemistry and Chemical Engineering, Shanghai Jiao Tong University, Shanghai 200240, China
b State Key Laboratory Base of Novel Functional Materials and Preparation Science, Faculty of Materials
Science and Chemical Engineering, Ningbo University, Ningbo, Zhejiang 315211, China
A Pd(II)-catalyzed oxidative cyclization of olefinic tosylamides was developed for the preparation of aryl-fused
and N-containing six-membered heterocycles. Under optimized conditions the reaction proceeded with high activity
and selectivity, with yields of up to 83% being obtained. This procedure provides a facile and efficient route to the
aforementioned heterocycles with 2-acetoxy functionality.
Keywords palladium, oxidative cyclization, six-membered ring, nitrogen heterocycle, 2-acetoxy functionality
Introduction
these reaction conditions.[13d] Recently, during our re-
search on Pd(II)-catalyzed effective cyclization,[14] we
reported the first Pd(II)-catalyzed oxidative cyclization
for the preparation of 2-substituted 1,2,3,4-tetrahydro-
quinolines with CuBr2 as the oxidant.[14f] Although
yields of up to 86% were obtained for this reaction, the
reaction itself took 3 d to complete, thus modifications
to the procedure were required. In recent years, several
examples of metal-catalyzed aminoacetoxylation of al-
kenes were reported.[13f,15] Particularly, Pd(II)-catalyzed
aminoacetoxylation has proved to be an efficient
method.[13f,15a,15b] For example, Sorensen et al.[13f]
achieved the oxidative cyclization for a number alkenyl
sulfonamides with PhI(OAc)2 as the oxidant. Herein we
report the Pd(II)-catalyzed aminoacetoxylation for the
highly regioselective formation of aryl-fused and six-
membered ring nitrogen heterocycles with the oxidant
PhI(OAc)2.
Aryl-fused and N-containing six-membered hetero-
cycles possess important biological and pharmacologi-
cal properties thus considerable effort has been directed
toward their synthesis,[1] and two of the more important
structures are 1,2,3,4-tetrahydroquinoline and 1,2,3,4-
tetrahydroquinoxaline derivatives.[2-11] 1,2,3,4-Tetra-
hydroquinoline derivatives show promising activity for
use as anti-depressent[4] and anti-diabetic therapies.[5]
They have also shown use as pesticides,[6] antioxi-
dants,[7] and for use in various types of dyes.[8] 1,2,3,4-
Tetrahydroquinoxaline derivatives are present in a large
number of biologically active compounds,[9] for exam-
ple as D2 receptor antagonists[10] and as models for
tetrahydrofolic acid (coenzyme F) derivatives.[11]
Among these derivatives, 2-substituted 1,2,3,4-tetra-
hydroquinoline and 1,2,3,4-tetrahydroquinoxaline de-
rivatives are the most important compounds.[4,6,8,10,11]
Many syntheses of 1,2,3,4-tetrahydroquinoline and
1,2,3,4-tetrahydroquinoxaline derivatives have been
reported.[1b,12] Pd(II)-Catalyzed oxidative cyclizations
have become a powerful tool for the construction of
N-containing heterocycles using relatively mild condi-
tions.[13] This pioneering work was first established by
Hegedus and co-workers[13a-13e] who obtained five
membered nitrogen-containing heterocycles in the
presence of PdCl2(MeCN)2 or PdCl2. However the for-
mation of six-membered rings is problematic using
Experimental
General
All air- and moisture-sensitive manipulations were
carried out with standard Schlenk techniques under ni-
trogen. Methanol, AcOH, toluene, Et2O, THF, DMF,
acetone, dichloromethane, MeCN and ethyl acetate were
dried according to published procedures. The commer-
cially available reagents were used without further
purification. TLC was run on 2 cm×5 cm silica plate.
*
E-mail: wanbin@sjtu.edu.cn; Tel.: 0086-021-54743265; Fax: 0086-021-54743265
Received September 29, 2012; accepted November 27, 2012; published online December 27, 2012.
Supporting information for this article is available on the WWW under http://dx.doi.org/10.1002/cjoc.201200963 or from the author.
Dedicated to the Memory of Professor Weishan Zhou.
†
132
© 2013 SIOC, CAS, Shanghai, & WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Chin. J. Chem. 2013, 31, 132—138

Preparation of Aryl-Fused Six-Membered Nitrogen Heterocycles
1
Column chromatography was run on silica gel (100－
overall yield). White solid; m.p. 77－78 ℃; H NMR
1
200 mesh). H NMR (400 MHz) spectra and 13C NMR
(400 MHz, CDCl3) δ: 7.61 (d, J＝8.0 Hz, 2H), 7.23－
7.20 (m, 3H), 7.08 (dd, J＝12.0, 2.4 Hz, 1H), 7.04 (d,
J＝2.8 Hz, 1H), 6.75 (s, 1H), 5.64－5.56 (m, 1H),
4.90－4.79 (m, 2H), 2.38 (s, 3H), 2.31－2.29 (m, 2H),
2.26－2.17 (m, 1H), 0.90 (d, J＝6.4 Hz, 3H); 13C NMR
(100 MHz, CDCl3) δ: 144.3, 142.7, 136.6, 136.6, 133.1,
131.8, 130.9, 129.9, 127.4, 127.3, 126.4, 114.4, 38.4,
38.0, 21.8, 19.9; HRMS (ESI) calcd for C18H20ClN-
NaO2S [M＋Na＋] 372.0801, found 372.0802.
(100 MHz) spectra were obtained on a Varian MER-
CURY plus-400 spectrometer. HRMS was performed
on a Micromass LCT TM at the Instrumental Analysis
Center of Shanghai Jiao Tong University.
General procedure for the preparation of substrates
1g－1j
According to refs. [14f,16], 2-aminobenzylalcohol
(1.0 g, 8.0 mmol) was tosylated with tosyl chloride, to
give intermediate 5g after extraction with CH2Cl2. To a
solution of the intermediate 5g in CH2Cl2 (50 mL) was
added SOCl2 (0.70 mL, 11 mmol) at room temperature,
the reaction mixture was heated under reflux conditions
for 2 h. Solvent and excess SOCl2 were removed to give
6g. To a solution of magnesium (2.9 g, 0.12 mol) and a
pellet of iodine in THF (25 mL) were added a little
amount of 3-chloro-1-butene in THF (25 mL) to trigger
the reaction, then 3-chloro-1-butene (8.1 mL, 81 mmol)
in THF was slowly added at −10 ℃ to afford the
Grignard reagent. Then the Grignard reagent was added
to the residue 6g in THF at −10 ℃. The mixture was
stirred overnight at room temperature, and quenched by
the addition of water. The mixture was extracted with
CH2Cl2 and the combined organic layers were washed
with brine and dried over Na2SO4. After removal of the
solvent, the residue was purified by flash column chro-
matography to give the substrate 1g (1.3 g, 51% overall
yield). Compounds 1h－1j were prepared from 4h－4j
by a similar procedure with 1g.
4-Methyl-N-(2-(2-methylbut-3-en-1-yl)phenyl)ben-
zenesulfonamide (1g): White solid, m.p. 63－64 ℃; 1H
NMR (400 MHz, CDCl3) δ: 7.61 (d, J＝8.0 Hz, 2H),
7.32 (d, J＝8.0 Hz, 1H), 7.21 (d, J＝8.0 Hz, 2H),
7.15－7.04 (m, 3H), 6.62 (s, 1H), 5.68－5.60 (m, 1H),
4.90－4.81 (m, 2H), 2.38 (s, 3H), 2.35－2.32 (m, 2H),
2.28－2.15 (m, 1H), 0.90 (d, J＝6.4 Hz, 3H); 13C NMR
(100 MHz, CDCl3) δ: 144.0, 143.2, 136.9, 134.5, 134.3,
131.2, 129.8, 127.4, 127.2, 126.3, 124.9, 114.0, 38.4,
38.2, 21.8, 19.8; HRMS (ESI) calcd for C18H21NNaO2S
[M＋Na＋] 338.1191, found 338.1202.
N-(4-Methoxy-2-(2-methylbut-3-en-1-yl)phenyl)-4-
methylbenzenesulfonamide (1j): Compound 1j was
prepared from 4j by a similar procedure with 1g (58%
1
overall yield). Oily liquid; H NMR (400 MHz, CDCl3)
δ: 7.57 (d, J＝8.0 Hz, 2H), 7.19 (d, J＝8.0 Hz, 2H),
7.03 (d, J＝8.0 Hz, 1H), 6.73－6.65 (m, 1H), 6.62－
6.58 (m, 2H), 5.67－5.58 (m, 1H), 4.86－4.79 (m, 2H),
3.71 (s, 3H), 2.36 (s, 3H), 2.32－2.28 (m, 2H), 2.12－
2.00 (m, 1H), 0.88 (d, J＝6.8 Hz, 3H); 13C NMR (100
MHz, CDCl3) δ: 158.3, 143.8, 143.5, 137.1, 129.7,
128.6, 127.5, 127.5, 127.1, 116.3, 113.7, 112.0, 55.6,
38.5, 38.2, 21.7, 19.9; HRMS (ESI) calcd for
C19H23NNaO3S [M＋Na＋] 368.1296, found 368.1308.
Preparation of N-allyl-4-methyl-N-[2-(4-methyl-
phenylsulfonamido)phenyl]benzenesulfonamide (1k)
To a solution of o-phenylendiamine (0.36 g, 3.3
mmol) and KI (0.028 g, 0.17 mmol) in THF was added
pyridine (0.016 mL, 0.20 mmol), then a THF (5 mL)
solution of allyl chloride (0.14 mL, 1.7 mmol) was
added to the above solution, and the reaction mixture
was heated to 50 ℃ for 12 h. After purification, inter-
mediate was obtained. TsCl (0.63 g, 3.3 mmol) and
pyridine (0.27 mL, 3.3 mmol) were added to the solu-
tion of intermediate in dichloromethane (20 mL), and
the reaction mixture was refluxed for 18 h. After purifi-
cation, the substrate 1k was afforded with up to 69%
yield in the two steps. Orange solid; m.p. 170－171 ℃;
1H NMR (400 MHz, CDCl3) δ: 7.85－7.79 (m, 3H),
7.62 (d, J＝8.2 Hz, 1H), 7.45 (d, J＝8.2 Hz, 2H), 7.29
－7.24 (m, 3H), 7.19 (t, J＝8.0 Hz, 1H), 6.81 (t, J＝8.0
Hz, 1H), 6.29－6.26 (m, 1H), 5.36－5.24 (m, 1H), 4.87
－4.81 (m, 2H), 4.24－4.15 (m, 1H), 3.67－3.58 (m,
1H), 2.43 (s, 3H), 2.38 (s, 3H); 13C NMR (100 MHz,
CDCl3) δ: 144.7, 144.1, 137.2, 137.0, 133.7, 131.4,
129.8, 129.6, 128.8, 128.5, 128.3, 127.7, 123.9, 120.4,
120.1, 55.1, 21.9, 21.7; HRMS (ESI) calcd for
C23H25N2O4S2 [M＋H＋] 457.1256, found 457.1258.
4-Methyl-N-(4-methyl-2-(2-methylbut-3-en-1-yl)-
phenyl)benzenesulfonamide (1h): Compound 1h was
prepared from 4h by a similar procedure with 1g (55%
1
overall yield). Oily liquid; H NMR (400 MHz, CDCl3)
δ: 7.62 (d, J＝8.0 Hz, 2H), 7.20 (d, J＝8.0 Hz, 2H),
7.14 (d, J＝8.2 Hz, 1H), 6.95－6.91 (m, 1H), 6.87 (s,
1H), 6.74 (s, 1H), 5.70－5.60 (m, 1H), 4.93－4.83 (m,
2H), 2.37 (s, 3H), 2.30－2.19 (m, 3H), 2.26 (s, 3H),
0.90 (d, J＝6.4 Hz, 3H); 13C NMR (100 MHz, CDCl3) δ:
143.8, 143.3 137.1, 136.3 135.2, 131.8, 131.8, 129.8,
127.8, 127.5, 125.7, 113.7, 38.5, 38.1, 21.7, 21.2, 19.8;
HRMS (ESI) calcd for C19H24NO2S [M＋H＋] 330.1528,
found 330.1509.
General procedure for Pd(II)-catalyzed oxidative
cyclization
Pd(OAc)2 (2.2 mg, 0.010 mmol) and PhI(OAc)2 (64
mg, 0.20 mmol) were dissolved in AcOH (2 mL) at
room temperature for 0.5 h, and then 0.10 mmol of the
substrate was added to the solution. The reaction mix-
ture was stirred at room temperature for 12 h. The mix-
ture was treated with reduced pressure distillation then
was purified by flash column chromatography to afford
N-(4-Chloro-2-(2-methylbut-3-en-1-yl)phenyl)-4-
methylbenzenesulfonamide (1i): Compound 1i was
prepared from 4i by a similar procedure with 1g (41%
Chin. J. Chem. 2013, 31, 132—138
© 2013 SIOC, CAS, Shanghai, & WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
www.cjc.wiley-vch.de
133

Wang et al.
FULL PAPER
the products 2.
128.3, 126.1, 66.1, 54.6, 28.4, 26.4, 21.8, 20.9; HRMS
(ESI) calcd for C19H20ClNNaO4S [M＋Na＋] 416.0699,
found 416.0702.
(1-Tosyl-1,2,3,4-tetrahydroquinolin-2-yl)methyl-
acetate (2a): Oily liquid; 1H NMR (400 MHz, CDCl3) δ:
7.69 (d, J＝8.0 Hz, 1H), 7.35 (d, J＝8.2 Hz, 2H),
7.27－7.22 (m, 1H), 7.15 (d, J＝7.8 Hz, 2H), 7.15－
7.10 (m, 1H), 6.95 (d, J＝7.6 Hz, 1H), 4.54－4.46 (m,
1H), 4.16－4.10 (m, 1H), 4.03－3.98 (m, 1H), 2.37 (s,
3H), 2.33－2.25 (m, 1H), 2.06 (s, 3H), 2.04－1.94 (m,
1H), 1.60－1.52 (m, 1H), 1.43－1.33 (m, 1H); 13C
NMR (100 MHz, CDCl3) δ: 171.5, 143.8, 136.2, 135.1,
134.6, 129.7, 128.2, 127.9, 127.3, 126.4, 66.0, 54.5,
27.0, 24.9, 21.8, 21.1; HRMS (ESI) calcd for
C19H21NNaO4S [M＋Na＋] 382.1089, found 382.1071.
(6-Methyl-1-tosyl-1,2,3,4-tetrahydroquinolin-2-yl)-
(6-Methoxy-1-tosyl-1,2,3,4-tetrahydroquinolin-2-yl)-
1
methyl acetate (2f): Oily liquid; H NMR (400 MHz,
CDCl3) δ: 7.58 (d, J＝8.4 Hz, 1H), 7.33 (d, J＝8.0 Hz,
2H), 7.15 (d, J＝8.2 Hz, 2H), 6.81－6.77 (m, 1H), 6.49
(d, J＝2.8 Hz 1H), 4.48－4.40 (m, 1H), 4.13－4.08 (m,
1H), 4.01－3.96 (m, 1H), 3.79 (s, 3H), 2.38 (s, 3H),
2.24－2.16 (m, 1H), 2.07 (s, 3H), 2.02－1.93 (m, 1H),
1.45－1.23 (m, 2H); 13C NMR (100 MHz, CDCl3) δ:
171.2, 158.0, 143.7, 136.7, 136.2, 129.7, 129.6, 128.0,
127.3, 113.1, 112.3, 66.0, 55.6, 54.6, 27.1, 25.3, 21.8,
21.1; HRMS (ESI) calcd for C20H23NNaO5S [M＋Na＋]
412.1195, found 412.1195.
1
methyl acetate (2b): Oily liquid; H NMR (400 MHz,
CDCl3) δ: 7.55 (d, J＝8.0 Hz, 1H), 7.36 (d, J＝8.2 Hz,
2H), 7.16 (d, J＝8.0 Hz, 2H), 7.07－7.03 (m, 1H), 6.76
(s, 1H), 4.51－4.43 (m, 1H), 4.14－4.08 (m, 1H),
4.02－3.96 (m, 1H), 2.37 (s, 3H), 2.30 (s, 3H), 2.27－
2.19 (m, 1H), 2.06 (s, 3H), 2.00－1.90 (m, 1H), 1.56－
1.47 (m, 1H), 1.40－1.29 (m, 1H); 13C NMR (100 MHz,
CDCl3) δ: 171.2, 143.7, 136.3, 136.2, 134.5, 132.6,
129.6, 128.4, 128.1, 128.0, 127.3, 65.9, 54.5, 27.0, 24.9,
21.8, 21.2, 21.2; HRMS (ESI) calcd for C20H23NNaO4S
[M＋Na＋] 396.1245, found 396.1230.
(3-Methyl-1-tosyl-1,2,3,4-tetrahydroquinolin-2-yl)-
methyl acetate (2g): White solid; m.p. 124－125 ℃; 1H
NMR (400 MHz, CDCl3) δ: 7.61 (d, J＝8.0 Hz, 1H),
7.34 (d, J＝8.0 Hz, 2H), 7.25－7.23 (m, 1H), 7.16－
7.12 (m, 3H), 6.94 (d, J＝7.2 Hz, 1H), 4.24－4.20 (m,
1H), 4.09－4.03 (m, 1H), 3.93－3.89 (m, 1H), 2.37 (s,
3H), 2.13－2.09 (m, 1H), 2.05 (s, 3H), 1.57－1.48 (m,
1H), 1.05－1.00 (m, 4H); 13C NMR (100 MHz, CDCl3)
δ: 171.4, 143.7, 136.7, 136.2, 135.4, 129.7, 128.6, 127.4,
127.2, 127.1, 126.9, 66.0, 61.9, 36.3, 34.3, 21.8, 21.2,
21.2; HRMS (ESI) calcd for C20H23NNaO4S [M＋Na＋]
396.1245, found 396.1270.
(8-Methyl-1-tosyl-1,2,3,4-tetrahydroquinolin-2-yl)-
1
methyl acetate (2c): White solid; m.p. 94－95 ℃; H
NMR (400 MHz, CDCl3) δ: 7.46 (d, J＝8.0 Hz, 2H),
7.22 (d, J＝8.0 Hz, 2H), 7.21－7.17 (m, 1H), 7.10 (t,
J＝7.8 Hz, 1H), 6.81 (d, J＝7.6 Hz, 1H), 4.52－4.44 (m,
1H), 4.09－4.03 (m, 1H), 3.78－3.72 (m, 1H), 2.50 (s,
3H), 2.42 (s, 3H), 2.16－2.02 (m, 2H), 2.05 (s, 3H),
1.25－1.18 (m, 1H), 1.11－1.02 (m, 1H); 13C NMR
(100 MHz, CDCl3) δ: 171.5, 143.9, 139.7, 139.3, 136.9,
134.7, 130.0, 129.8, 127.8, 127.3, 125.0, 66.3, 55.0,
28.6, 26.1, 21.8, 21.1, 19.4; HRMS (ESI) calcd for
C20H23NNaO4S [M＋Na＋] 396.1245, found 396.1244.
(6-Chloro-1-tosyl-1,2,3,4-tetrahydroquinolin-2-yl)-
(3,6-Dimethyl-1-tosyl-1,2,3,4-tetrahydroquinolin-2-
yl)methyl acetate (2h): Oily liquid; 1H NMR (400 MHz,
CDCl3) δ: 7.49 (d, J＝8.0 Hz, 1H), 7.36 (d, J＝8.8 Hz,
2H), 7.17 (d, J＝8.4 Hz, 2H), 7.08－7.05 (m, 1H), 6.75
(s, 1H), 4.23－4.19 (m, 1H), 4.07－4.02 (m, 1H),
3.92－3.87 (m, 1H), 2.38 (s, 3H), 2.31 (s, 3H), 2.07 (s,
3H), 2.07－2.03 (m, 1H), 1.54－1.52 (m, 1H), 1.06－
0.96 (m, 4H); 13C NMR (100 MHz, CDCl3) δ: 171.5,
143.6, 136.7, 136.0, 132.6, 129.6, 128.4, 128.1, 127.8,
127.2, 65.7, 61.9, 36.3, 34.3, 21.8, 21.3, 21.2, 21.2;
HRMS (ESI) calcd for C21H25NNaO4S [M ＋Na ＋]
410.1402, found 410.1411.
1
methyl acetate (2d): Oily liquid; H NMR (400 MHz,
CDCl3) δ: 7.64 (d, J＝8.6 Hz, 1H), 7.37 (d, J＝8.2 Hz,
2H), 7.24－7.20 (m, 1H), 7.18 (d, J＝8.0 Hz, 2H), 6.96
(d, J＝2.4 Hz, 1H), 4.52－4.44 (m, 1H), 4.14－4.09 (m,
1H), 4.03－3.97 (m, 1H), 2.38 (s, 3H), 2.31－2.23 (m,
1H), 2.06 (s, 3H), 1.99－1.89 (m, 1H), 1.57－1.50 (m,
1H), 1.44－1.33 (m, 1H); 13C NMR (100 MHz, CDCl3)
δ: 171.1, 144.1, 136.2, 136.0, 134.0, 131.8, 129.9, 129.5,
127.8, 127.4, 127.3, 65.7, 54.5, 26.5, 24.8, 21.8, 21.1;
HRMS (ESI) calcd for C19H20ClNNaO4S [M＋Na＋]
416.0699, found 416.0701.
(6-Chloro-3-methyl-1-tosyl-1,2,3,4-tetrahydroquin-
olin-2-yl)methyl acetate (2i): White solid; m.p. 103－
104 ℃; 1H NMR (400 MHz, CDCl3) δ: 7.57 (d, J＝8.8
Hz, 1H), 7.37 (d, J＝8.4 Hz, 2H), 7.25－7.23 (m, 1H),
7.19 (d, J＝8.8 Hz, 2H), 6.95 (d, J＝2.4 Hz, 1H),
4.24－4.21 (m, 1H), 4.07－4.02 (m, 1H), 3.95－3.90
(m, 1H), 2.40 (s, 3H), 2.10－2.07 (m, 1H), 2.06 (s, 3H),
1.58－1.50 (m, 1H), 1.06－0.96 (m, 4H); 13C NMR
(100 MHz, CDCl3) δ: 171.3, 144.1, 137.8, 136.4, 134.1,
132.2, 129.8, 129.8, 127.5, 127.3, 127.1, 65.5, 61.9,
(8-Chloro-1-tosyl-1,2,3,4-tetrahydroquinolin-2-yl)-
methyl acetate (2e): Oily liquid; H NMR (400 MHz,
36.0, 34.1, 22.0, 21.2, 21.0; HRMS (ESI) calcd for
＋
1
C20H22ClNNaO4S [M ＋ Na
] 430.0856, found
CDCl3) δ: 7.73 (d, J＝8.0 Hz, 2H), 7.36 (d, J＝8.2 Hz,
1H), 7.28 (d, J＝8.0 Hz, 2H), 7.14 (t, J＝7.8 Hz, 1H),
6.98 (d, J＝7.6 Hz, 1H), 4.52－4.44 (m, 1H), 3.95－
3.89 (m, 1H), 3.76－3.70 (m, 1H), 2.43 (s, 3H), 2.35－
2.26 (m, 2H), 2.00－1.90 (m, 1H), 1.88 (s, 3H), 1.28－
1.18 (m, 1H); 13C NMR (100 MHz, CDCl3) δ: 171.1,
144.2, 141.6, 136.9, 135.0, 133.7, 129.8, 129.2, 128.5,
430.0885.
(6-Methoxy-3-methyl-1-tosyl-1,2,3,4-tetrahydroquin-
olin-2-yl)methyl acetate (2j): Oily liquid; 1H NMR (400
MHz, CDCl3) δ: 7.52 (d, J＝8.0 Hz, 1H), 7.34 (d, J＝
8.0 Hz, 2H), 7.17 (d, J＝8.4 Hz, 2H), 6.81－6.78 (m,
1H), 6.49 (d, J＝2.8 Hz, 1H), 4.21－4.18 (m, 1H),
4.04－4.00 (m, 1H), 3.93－3.88 (m, 1H), 3.97 (s, 3H),
134
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Chin. J. Chem. 2013, 31, 132—138

Preparation of Aryl-Fused Six-Membered Nitrogen Heterocycles
2.39 (s, 3H), 2.08 (s, 3H), 2.05－2.00 (m, 1H), 1.51－
1.42 (m, 1H), 1.04 (d, J＝6.4 Hz, 3H), 0.97－0.90 (m,
1H); 13C NMR (100 MHz, CDCl3) δ: 171.4, 158.4,
143.7, 137.9 136.6, 130.0, 129.7, 128.0, 127.2, 112.7,
112.1, 65.6, 61.9, 55.6, 36.3, 34.6, 21.8, 21.2, 21.1;
HRMS (ESI) calcd for C21H25NNaO5S [M ＋Na ＋]
426.1351, found 426.1375.
the Pd(II)-catalyzed oxidative cyclization with PhI-
(OAc)2 as the oxidant. Reaction of 1b with Pd(OAc)2
(0.1 equiv.) and PhI(OAc)2 (2 equiv.) in AcOH at room
temperature gave 2b in 77% yield after 12 h. No
seven-membered ring byproducts were observed. The
catalytic effect of the Pd(OAc)2 was confirmed by per-
forming the reaction in the absence of the Pd species
(Scheme 2). Only compound 3 (89% yield) was ob-
tained with no cyclic products being produced.
(1,4-Ditosyl-1,2,3,4-tetrahydroquinoxalin-2-yl)-
1
methyl acetate (2k): Oily liquid; H NMR (400 MHz,
CDCl3) δ: 7.76－7.72 (m, 1H), 7.56 (d, J＝8.0 Hz, 2H),
7.54－7.50 (m, 1H), 7.43 (d, J＝7.8 Hz, 2H), 7.25－
7.19 (m, 4H), 7.11－7.04 (m, 2H), 4.76－4.69 (m, 1H),
3.98 (d, J＝6.4 Hz, 2H), 3.93－3.87 (m, 1H), 3.37－
3.31 (m, 1H), 2.41 (s, 3H), 2.40 (s, 3H), 2.03 (s, 3H);
13C NMR (100 MHz, CDCl3) δ: 170.6, 144.6, 144.5,
135.3, 131.4, 130.1, 127.5, 127.2, 127.1, 126.4, 126.1,
124.3, 119.6, 63.2, 53.4, 46.1, 21.8, 21.8, 20.9; HRMS
(ESI) calcd for C25H27N2O6S2 [M＋H＋] 515.1311,
found 515.1301.
Scheme 2 Reactions with/without Pd(OAc)2
Me
Me
Pd(OAc)2 (0.1 equiv.)
NH
OAc
PhI(OAc)2 (2 equiv.)
AcOH, r.t., 12 h
N
Ts
Ts
2b
Yield 77%
1b (0.1 mmol)
Me
Me
N-Acetoxy-N-(2-(but-3-en-1-yl)-4-methylphenyl)-4-
methylbenzenesulfonamide (3): Oily liquid; H NMR
NH
PhI(OAc)2 (2 equiv.)
AcOH, r.t., 12 h
NTs
OAc
1
Ts
(400 MHz, CDCl3) δ: 7.86 (d, J＝8.0 Hz, 2H), 7.50 (d,
J＝8.2 Hz, 1H), 7.30 (d, J＝8.0 Hz, 2H), 6.84－6.80 (m,
1H), 6.58－6.55 (m, 1H), 5.75－5.63 (m, 1H), 4.94－
4.86 (m, 2H), 2.42 (s, 3H), 2.40－2.30 (m, 2H), 2.20－
2.13 (m, 2H), 2.02 (s, 3H), 1.49 (s, 3H); 13C NMR (100
MHz, CDCl3) δ: 169.5, 164.2, 149.0, 144.9, 143.6,
139.0, 137.8, 137.0, 129.6, 127.1, 121.8, 115.4, 74.8,
32.3, 30.0, 26.3, 21.8, 21.5; HRMS (ESI) calcd for
C20H23NNaO4S [M＋Na＋] 396.1245, found 396.1230.
1b (0.1 mmol)
3
Yield 89%
The Pd(II) source had a large effect on the reaction
(Table 1). PdBr2 and Pd(OAc)2 were found to be supe-
rior to other Pd(II) alternatives (Table 1, Entries 1－5).
Pd(OAc)2, being inexpensive and providing high yields,
was chosen as the catalyst for our reactions. The quan-
tity of catalyst also had a bearing on the reaction out-
come with low amounts of catalyst showing a marked
decrease in reaction activity (Table 1, Entry 6). Increas-
ing the quantity of Pd(OAc)2 from 0.1 equiv. to 0.2
equiv. did not markedly improve the reaction yield (Ta-
ble 1, Entry 7).
Results and Discussion
2-Substituted
1,2,3,4-tetrahydroquinoline
and
1,2,3,4-tetrahydroquinoxaline derivatives were prepared
from arylamines with an ortho olefinic side chain. The
formation of six-membered ring systems (Scheme 1,
path a) is generally much easier than the synthesis of
seven-membered ring systems (Scheme 1, path b), thus
high yields of the desired products were envisaged using
these starting materials.
Table 1 The effect of the Pd(II) source on the Pd(II)-catalyzed
oxidative cyclization
Me
Me
Pd(II)
OAc
Considering the potential for obtaining high yields in
PhI(OAc)2 (2 equiv.)
AcOH, r.t., 12 h
NH
Ts
N
our recent report using substrate 1b,[14f] it was used in
Ts
2b
1b
Scheme 1 Pd(II)-catalyzed oxidative cyclizations
Entry
Pd(II)
PdCl2
PdBr2
Quantity
0.1
Yielda/%
1
2
3
4
5
6
7
54
73
49
43
77
19
78
X
R1
0.1
R
OAc
N
PdCl2(MeCN)2
Pd(CF3CO2)2
Pd(OAc)2
0.1
path a
Ts
0.1
X
R1
0.1
R
Pd(OAc)2
0.05
0.2
NH
Ts
Pd(OAc)2
R1
OAc
a Isolated yield.
path b
X
N
R
Temperature effect on the reaction was examined
(Table 2, Entries 1－3). Increasing the reaction tem-
X = CH2, NTs
Ts
Chin. J. Chem. 2013, 31, 132—138
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135

Wang et al.
FULL PAPER
perature to 40 ℃ accelerated the reaction rate (2 h) but
reduced the yield of 2b (77% at room temperature to
40% at 40 ℃). Further increasing the temperature to 60
℃ decreased the yield of 2b to 31%. Reactions at lower
than room temperature were not performed because of
the relatively high freezing point of AcOH.
The effects of solvent on the Pd(II)-catalyzed oxida-
tive cyclization were examined (Table 2, Entries 1, 4, 7
－14). MeCN was discovered to be an efficient solvent
for the reaction (Table 2, Entry 4). Reactions in Et2O
and acetone only provided small amounts of product
(Table 2, Entries 9, 12). Only trace amounts of product
were obtained when using toluene, THF and EtOAc as
solvents. No reaction occurred when MeOH, DMF and
CH2Cl2 were used.
A variety of ligands are known to influence Pd(II)-
catalyzed oxidative cyclizations,[17] thus two ligands
were selected for our reaction (Table 2, Entries 5, 6).
MeCN was chosen as the solvent for the reaction be-
cause of the negative interactions between the Pd(II)
species and ligand when using AcOH as a solvent.
When using pyridine and 2,2'-bipyridine as ligands,
product 3 was obtained in place of 2b. The most prob-
able explanation for this outcome arises from the weak-
ened activating effect of Pd(II) on the double bond re-
sulting from the coordination between the Pd(II) and the
ligand. The competing reaction leading to 3 therefore
becomes the prominent reaction.
the Pd(II) catalyzed oxidative cyclization. 1a－1f were
synthesized according to
a previously published
route.[14f,16] These substrates were subjected to the opti-
mized catalytic conditions. 4-Substituted substrates 1b,
1d and 1f underwent cyclization with high yields of
products being obtained, irrespective of the substituent
being electron rich/poor (Table 3, Entries 2, 4, 6). A
6-Me substituted substrate 1c also underwent cycliza-
tion in good yield (Table 3, Entry 3). The 6-Cl substi-
tuted substrate 1e only cyclized in 28% yield (Table 3,
Entry 5). Substrates 1g－1j possessing an allylic methyl
group were prepared according to a similar route to 1a
－1f (Scheme 3). To our delight, the allylic methyl
group did not have an obvious effect on the cyclization
for these substrates. The substrates 1h and 1j with elec-
tron rich substituents (Table 3, Entries 8, 10) allowed
the cyclization to occur more efficiently than substrate
1i with electron-withdrawing substituent (Table 3, Entry
9). Very high diastereoselectivities were observed for
1
the cyclization of substrates 1g－1j. H NMR spectra
showed only one diastereomeric product. The indicated
stereochemistries of products 2g－2j were confirmed by
NOE analysis.[18] 1k possessing an allylamine group
was prepared using a simplified procedure (Scheme 4).
A 1,2,3,4-tetrahydroquinoxaline derivative was pre-
pared in moderate yield via the cyclization of 1k. 2c
was used to determine the structure of the products us-
ing X-ray crystallography because of its ready ability to
crystallize (Figure 1).[19]
Table 2 Condition optimization for the Pd(II)-catalyzed oxida-
tive cyclization
Scheme 3 Synthetic route to 1g－1j
Me
Me
Pd(OAc)2 (0.1 equiv.)
OAc
R
R
R
PhI(OAc)2 (2 equiv.)
Solvent, r.t.
NH
Ts
N
OH
OH
TsCl
SOCl2
Ts
2b
NH2
4g－4j
NHTs
1b
5g－5j
Time/h Yielda/%
ClMg
Entry Temp./℃ Solvent
Additive
－
R
1
2
r.t.
40
60
r.t.
r.t.
r.t.
r.t.
r.t.
r.t.
r.t.
r.t.
r.t.
r.t.
r.t.
AcOH
AcOH
AcOH
MeCN
MeCN
12
2
77
40
Cl
－
NH
NHTs
6g－6j
3
－
2
31
Ts
1g－1j
4
－
12
6
58
g: R = H; h: R = Me; i: R = Cl; j: R= OMe
5b
6b
7
Pyridine
－
MeCN 2,2'-Bipyridine
6
－
MeOH
Toluene
Et2O
－
－
－
－
－
－
－
－
12
12
12
12
12
12
12
12
－
Scheme 4 Synthetic route to 1k
8
Trace
12
9
H
N
NH2
NH2
Cl
10
11
12
13
14
THF
Trace
－
KI, pyridine
THF, 50 oC
DMF
NH2
8
Acetone
CH2Cl2
EtOAc
27
7
Ts
N
－
TsCl
Trace
pyridine
CH2Cl2, reflux
a Isolated yield. b 0.12 equiv. additive.
NH
Ts
A series of substrates (1a－1k) were prepared for
1k
136
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© 2013 SIOC, CAS, Shanghai, & WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Chin. J. Chem. 2013, 31, 132—138

Preparation of Aryl-Fused Six-Membered Nitrogen Heterocycles
Table 3 Different substrates
Continued
Yielda/%
Entry
10b
Substrate
Product
X
N
R1
X
R1
Pd(OAc)2 (0.1 equiv.)
R
MeO
MeO
Me
OAc
OAc
R
PhI(OAc)2 (2 equiv.)
AcOH, r.t., 12 h
NH
NH
Ts
72
Ts
N
Ts
Ts
2
2j
1
1j
X = CH2, NTs
Ts
N
Ts
N
Entry
1
Substrate
Product
Yielda/%
11c
OAc
61
NH
Ts
N
Ts
2k
OAc
1k
NH
Ts
N
a Isolated yield. b The stereochemistry was confirmed by the NOE
analysis. c The reaction was performed in the solvent of MeCN.
Ts
65
2a
1a
Me
Me
OAc
NH
Ts
1b
2
3
77
78
57
N
Ts
2b
OAc
NH
Ts
N
Ts
2c
Me
Me
1c
Cl
Cl
OAc
NH
Ts
4
N
Ts
Figure 1 X-ray single crystal diffraction of product 2c.
2d
1d
Conclusions
OAc
To summarize, aryl-fused and six-ring nitrogen het-
erocycles were prepared from olefinic tosylamides using
our new catalytic system. The reaction result depends
on the Pd(II) catalyst, reaction temperature, solvent, and
the substituents on the substrates. This method provides
direct access to 2-substituted 1,2,3,4- tetrahydroquino-
line and 1,2,3,4-tetrahydroquinoxaline derivatives with
acetoxy functionality, in up to 83% yield.
NH
Ts
5
N
Ts
28
Cl
Cl
2e
1e
MeO
MeO
OAc
NH
Ts
6
N
61
71
Ts
2f
1f
Me
Acknowledgement
OAc
7b
8b
9b
NH
N
This work was partly supported by the National
Natural Science Foundation of China (Nos. 20972095,
21172143, 21232004), Nippon Chemical Industrial Co.,
Ltd., the Nature Science Foundation of Ningbo (No.
2012A610086) and Shanghai Jiao Tong University. We
thank Prof. Tsuneo Imamoto and Dr. Masashi Sugiya
for helpful discussions and the Instrumental Analysis
Center of Shanghai Jiao Tong University for HRMS
determination.
Ts
Ts
1g
2g
Me
Cl
Me
Cl
Me
OAc
NH
83
59
N
Ts
Ts
2h
1h
1i
Me
OAc
NH
Ts
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N
Ts
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© 2013 SIOC, CAS, Shanghai, & WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
www.cjc.wiley-vch.de
137

Wang et al.
FULL PAPER
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(Zhao, C.)
138
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Chin. J. Chem. 2013, 31, 132—138