FeCl3/Nal-catalyzed allylic C-H oxidation of arylalkenes with a catalytic amount of disulfide under air

Article abstract of DOI:10.1021/jo201122s

This paper describes a FeCl₃/NaI-catalyzed formal allylic C-H oxidation of arylalkenes using a catalytic amount of disulfide with BnOH and 4-nitroaniline as nucleophiles and air as oxidant to form the corresponding allyl ethers and amines. A possible reaction mechanism has been proposed.

Full text of DOI:10.1021/jo201122s

NOTE
pubs.acs.org/joc
FeCl3/NaI-Catalyzed Allylic CꢀH Oxidation of Arylalkenes with a
Catalytic Amount of Disulfide under Air
Deshun Huang,† Haining Wang,† Fazhen Xue,† and Yian Shi*,†,‡
†Beijing National Laboratory for Molecular Sciences, CAS Key Laboratory of Molecular Recognition and Function, Institute of
Chemistry, Chinese Academy of Sciences, Beijing 100190, China
‡Department of Chemistry, Colorado State University, Fort Collins, Colorado 80523, United States
S Supporting Information
b
ABSTRACT: This paper describes a FeCl3/NaI-catalyzed formal allylic
CꢀH oxidation of arylalkenes using a catalytic amount of disulfide with
BnOH and 4-nitroaniline as nucleophiles and air as oxidant to form the
corresponding allyl ethers and amines. A possible reaction mechanism has
been proposed.
llylic CꢀH oxidation provides an important approach to
functionalize olefins. While various systems have been
giving the corresponding allyl amine in 86% yield (Table 1,
entry 20).
A
developed,1ꢀ6 there are still challenges, and new processes need
to be explored. Recently, we reported a mild acid-catalyzed
formal allylic CꢀH oxidation of aryl cycloalkenes with N-propyl-
thiosuccinimide in the presence of various nucleophiles, provid-
ing allyl ethers, esters, and sulfonamides (Scheme 1).7 However,
this process requires 2.2 equiv of N-propylthiosuccinimide and
generates a substantial amount of succinimide and disulfide as
byproduct, which prompted us to develop a new process requir-
ing only a catalytic amount of sulfur reagent. Along this line, we
have been investigating the possibility of replacing N-propylthio-
succinimide with a disulfide to mediate the allylic CꢀH oxidation
process while the disulfide can be regenerated in situ by an
oxidant.8,9 During our studies, we found that the allylic CꢀH
oxidation can be achieved using a catalytic amount of disulfide
and FeCl3/NaI with air as oxidant (Scheme 2). Herein we report
our studies on this subject.
The substrate scope was subsequently examined with BnOH
and 4-nitroaniline as nucleophiles. As shown in Table 2, various
substituted 1-phenylcyclohexenes (1aꢀe), 1-naphthylcyclohex-
ene (1f), 1-(3-thiophene-yl)cyclohexene (1g), 1-phenylcyclohep-
tene (1h), and 1-phenylcyclopentene (1i) were found to be
suitable substrates for the reaction, producing the corresponding
allyl ethers and amines in 50ꢀ86% yields (Table 2, entries 1ꢀ9).
The oxidation reaction can also be extended to acyclic olefins
(Table 2, entries 10ꢀ12). The oxidation appears to be highly
stereoselective, giving the corresponding allyl ethers and amines
with high E/Z ratio regardless of the geometry of olefin substrates.
When the reaction was monitored by 1H NMR, compounds
6a and 7a were detected along with allyl ether 4a during the
reaction process (Scheme 3). When preformed compound 6a
was treated with FeCl3 (10 mol %), NaI (20 mol %), and
nPrSSnPr (20 mol %) in CHCl3 at 60 °C for 18 h, allyl ether
4a was formed with a small amount of allyl sulfide 7a (Scheme 4).
When preformed compound 7a was subjected to the reaction
conditions, it was readily converted to allyl ether 4a (Scheme 5).
These results indicate that compounds 6a and 7a are likely to be
the intermediates involved in the reaction pathway. Control
studies showed that the transformations described in Scheme 4
and 5 require FeCl3 and are facilitated by NaI. No reaction
occurred without FeCl3. In the absence of NaI, the reaction
proceeded at a slower rate with more byproduct.
Initial studies were carried out with 1-phenylcyclohexene as
substrate and BnOH as nucleophile. After some screenings, it
was found that the allyl ether product was formed in the
presence of a catalytic amount of disulfide with FeCl3/NaI as
catalyst and air as oxidant (Table 1).10,11 Among the disulfides
studied, nPrSSnPr appears to be more effective, giving the allyl
benzyl ether in 79% yield (Table 1, entry 1). Other Fe species
such as FeCl3 6H2O, FeF3, FeBr3, and FeCl2 can also catalyze
3
this reaction, giving the product in 45ꢀ73% yield (Table 1,
entries 6ꢀ9), but no reaction was observed with Fe(acac)3
(Table 1, entry 10). Studies showed that both FeCl3 and iodide
sources are required for the reaction (Table 1, entries 11, 12)
with NaI being the most effective cocatalyst (Table 1, entries 1,
13ꢀ15). Further studies showed that other alcohols can also be
employed to form the corresponding allyl ethers in moderate
yields (Table 1, entries 16ꢀ19). Among various nitrogen
nucleophiles examined, 4-nitroaniline was found to be effective,
When deuterium-labeled 1-phenylcyclohexene (1l:1m =
80:20) was subjected to the reaction conditions, compounds 8
and 9 were obtained as a 1:1 mixture with the remaining 1l and
1m being 70:30 (Scheme 6). Since compound 1l could slowly
convert to 1m under the reaction conditions, the reaction was
Received: June 15, 2011
Published: July 15, 2011
r
2011 American Chemical Society
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dx.doi.org/10.1021/jo201122s J. Org. Chem. 2011, 76, 7269–7274
|

The Journal of Organic Chemistry
NOTE
Scheme 1
Table 2. Allylic Oxidation of Arylalkenesa
Scheme 2
Table 1. Studies on Reaction Conditions and Nucleophilesa
entry
NuH
BnOH
catalyst
RSSR
time (h) yield (%)
1
2
3
4
5
6
7
8
9
FeCl3/NaI
FeCl3/NaI
FeCl3/NaI
FeCl3/NaI
FeCl3/NaI
nPrSSnPr
PhSSPh
18
18
18
18
18
18
18
18
18
18
18
18
18
18
18
35
23
26
18
18
79
69
50
38
14
73
45
72
68
NR
trace
NR
54
43
49
43
53
62
71
86
BnOH
BnOH
BnOH
BnOH
BnOH
BnOH
BnOH
BnOH
BnSSBn
PhSeSePh
FeCl3•6H2O/NaI nPrSSnPr
FeF3/NaI
FeBr3/NaI
FeCl2/NaI
Fe(acac)3/NaI
FeCl3
nPrSSnPr
nPrSSnPr
nPrSSnPr
nPrSSnPr
nPrSSnPr
nPrSSnPr
nPrSSnPr
nPrSSnPr
nPrSSnPr
nPrSSnPr
nPrSSnPr
nPrSSnPr
nPrSSnPr
nPrSSnPr
10 BnOH
11 BnOH
12 BnOH
13 BnOH
14b BnOH
15 BnOH
16 MeOH
17 i-PrOH
18 n-BuOH
NaI
FeCl3/KI
FeCl3/I2
FeCl3/NIS
FeCl3/NaI
FeCl3/NaI
FeCl3/NaI
19 Cl(CH2)3OH FeCl3/NaI
20 4-nitroaniline FeCl3/NaI
a The reaction was carried out with 1a (0.5 mmol), NuH (1.0 mmol),
FeCl3 (10 mol %), X (20 mol %), and RSSR (20 mol %) in CHCl3
(0.5 mL) at 60 °C under air unless otherwise stated. b 10 mol % of I2
was used.
stopped with partial conversion so that the ratio of the remaining
1l and 1m could be determined.
While a precise understanding of the reaction mechanism for
the FeCl3/NaI-catalyzed allylic CꢀH oxidation awaits further
studies, a plausible catalytic pathway is proposed in Scheme 7.7
The disulfide initially reacts with the olefin to generate thiiranium
ion 10 with the assistance of FeCl3/NaI.8,9c Thiiranium ion 10 is
subsequentlyconverted to allyl sulfide12 directly orvia compound
a The reactions were carried out with 1 (0.5 mmol), BnOH or p-
NO2C6H4NH2 (1.0 mmol), FeCl3 (10 mol %), NaI (20 mol %), and
nPrSSnPr (20 mol %) in CHCl3 (0.5 mL) at 60 °C under air unless
otherwise stated. b E/Z ratios were determined by the 1H NMR analysis
of the crude reaction mixture. c At 40 °C. d At rt.
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The Journal of Organic Chemistry
NOTE
Scheme 3
the olefin, the formation of allyl sulfide and allyl cation, and the
regeneration of disulfide.9c
In summary, we have developed a FeCl3/NaI-catalyzed formal
allylic CꢀH oxidation of arylalkenes using a catalytic amount of
disulfide with air as oxidant. Various arylalkenes can be oxidized
to form allyl ethers and amines with BnOH and 4-nitroaniline as
nucleophiles. In the case of acyclic alkenes, the reaction is highly
stereoslective, giving the product with a high E/Z ratio. FeCl3/
NaI plays a crucial role in the catalytic cycle. The Fe(III) species
acts as both Lewis acid and oxidant. The current process provides
a new entry to the allylic CꢀH oxidation.
Scheme 4
’ EXPERIMENTAL SECTION
General Methods. All commercially available reagents were used
without further purification. All dry solvents were freshly distilled under
nitrogen from appropriate drying agents before use. Toluene, tetrahy-
drofuran, and ethyl ether were distilled from sodium benzophenone.
CH2Cl2, 1,2-DCE and MeCN were distilled from CaH2. CHCl3 was
distilled from P2O5. Columnchromatography was performed on silica gel
(200ꢀ300 mesh). 1H NMR spectra were recorded on a 400 MHz NMR
spectrometer, and 13C NMR spectra were recorded on a 100 MHz NMR
spectrometer. IR spectra were recorded on an FT-IR spectrometer.
Melting points were uncorrected. 1-Phenylcyclohexene (1a) was pur-
chased from a commercial supplier. Cycloalkenes 1bꢀf,h,i, and acyclic
alkene 1j (E/Z = 5/1) were prepared from the corresponding alkanones
by the addition of appropriate Grignard reagents and subsequent
dehydration with HCO2H, CF3CO2H, or p-TsOH. Alkenes 1g and 1k
(E/Z = 10/1) were prepared according to the reported procedure.13
Acyclic alkene 1j0 (E/Z = 1/12) was prepared by Wittig reaction of
1-phenylbutan-1-one and propyltriphenylphosphonium bromide.
Representative Procedure for Allylic CꢀH Oxidation
(Table 2, Entry 1). 4a: To a Schlenk tube charged with condenser
were added FeCl3 (0.0081 g, 0.050 mmol), NaI (0.015 g, 0.10 mmol),
CHCl3 (0.5 mL), BnOH (0.108 g, 1.0 mmol), 1-phenylcyclohexene
(0.079 g, 0.50 mmol), and nPrSSnPr (0.015 g, 0.10 mmol). The resulting
mixture was stirred at 60 °C for 18 h under air, quenched with 10%
aqueous Na2S2O3 (5 mL), extracted with CH2Cl2 (3 ꢁ 10 mL), washed
with brine (10 mL), dried over MgSO4, filtered, concentrated, and
purified by flash chromatography (silica gel, petroleum ether/ethyl
acetate = 200/1) to give allyl ether 4a as a pale yellow oil (0.104 g,
79%). [Reaction time: 4a, 4c (18 h); 4d, 4f (24 h); 4b (26 h); 4g, 4h
(30 h); 4i (43 h); 4e, 4k (48 h); 4j (90 h).]
Scheme 5
Scheme 6
Scheme 7. Proposed Catalytic Pathway
5a: To a Schlenk tube charged with condenser were added FeCl3
(0.0081 g, 0.050 mmol), NaI (0.015 g, 0.10 mmol), 4-nitroaniline (0.138
g, 1.0 mmol), CHCl3 (0.5 mL), 1-phenylcyclohexene (0.079 g, 0.50
mmol), and nPrSSnPr (0.015 g, 0.10 mmol). The resulting mixture was
stirred at 60 °C for 18 h under air, quenched with 10% aqueous Na2S2O3
(5 mL), extracted with CH2Cl2 (3 ꢁ 10 mL), washed with brine
(10 mL), dried over MgSO4, filtered, concentrated, and purified by flash
chromatography (silica gel, petroleum ether/ethyl acetate =10/1) to
give allyl amine 5a as yellow solid (0.127 g, 86%). [Reaction time: 5a (18
h); 5c, 5d, 5f, 5 h (24 h); 5b, 5g (30 h); 5e, 5i, 5k (48 h); 5j (90 h).]
6-Benzyloxy-1-phenylcyclohexene (4a):7 pale yellow oil; IR (film)
1494, 1453, 1067 cmꢀ1; 1H NMR (400 MHz, CDCl3) δ 7.38ꢀ7.32 (m,
2H), 7.30ꢀ7.14 (m, 8H), 6.17 (dd, J = 4.4, 3.6 Hz, 1H), 4.58 (d, J = 11.6
Hz, 1H), 4.46 (d, J = 11.6 Hz, 1H), 4.42ꢀ4.37 (m, 1H), 2.33ꢀ2.23 (m,
1H), 2.22ꢀ2.08 (m, 2H), 1.94ꢀ1.81 (m, 1H), 1.71ꢀ1.59 (m, 2H); 13C
NMR (100 MHz, CDCl3) δ 141.5, 138.8, 137.8, 129.8, 128.3, 128.2,
128.0, 127.5, 126.8, 126.2, 72.6, 70.7, 27.3, 26.2, 17.3.
11 under the reaction conditions. Allyl cation 13 is then generated
from allyl sulfide 12 by FeCl3/NaI and reacts with the nucleophile
to give product 4. The disulfide is finally regenerated by oxidation
of the thiolate with FeCl3/NaI and air.12 FeCl3/NaI plays multiple
roles in the catalytic cycle. It promotes the addition of disulfide to
6-(4-Nitrophenylamino)-1-phenylcyclohexene (5a): yellow solid;
1
mp 148ꢀ150 °C; IR (film) 3373, 1599, 1313, 1111 cmꢀ1; H NMR
(400 MHz, CDCl3) δ 8.08 (d, J = 9.2 Hz, 2H), 7.38ꢀ7.20 (m, 5H), 6.54
(d, J = 9.2 Hz, 2H), 6.40 (dd, J = 4.4, 3.6 Hz, 1H), 4.63ꢀ4.50 (m, 2H),
7271
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NOTE
2.40ꢀ2.18 (m, 2H), 2.16ꢀ2.07 (m, 1H), 1.85ꢀ1.60 (m, 3H); 13C NMR
(100 MHz, CDCl3) δ 152.3, 139.6, 138.1, 136.0, 130.2, 128.8, 127.6,
126.8, 125.5, 111.4, 48.3, 27.9, 26.0, 17.4. Anal. Calcd for C18H18N2O2:
C, 73.45; H, 6.16; N, 9.52. Found: C, 73.35; H, 6.21; N, 9.48.
6-Benzyloxy-1-(2-methoxyphenyl)cyclohexene (4b):7 white solid;
mp 46ꢀ47 °C; IR (film) 1597, 1489, 1453, 1243, 1066 cmꢀ1; 1H NMR
(400 MHz, CDCl3) δ 7.26ꢀ7.18 (m, 2H), 7.16ꢀ7.11 (m, 3H),
6.97ꢀ6.89 (m, 3H), 6.77 (d, J = 8.0 Hz, 1H), 5.86 (dd, J = 3.6, 3.2 Hz,
1H), 4.52ꢀ4.47 (m, 1H), 4.45 (d, J = 12.0 Hz, 1H), 4.30 (d, J = 12.0 Hz,
1H), 3.62 (s, 3H), 2.27ꢀ2.09 (m, 2H), 2.02ꢀ1.92 (m, 1H), 1.92ꢀ1.77
(m, 2H), 1.71ꢀ1.60 (m, 1H); 13C NMR (100 MHz, CDCl3) δ 156.9,
139.4, 138.8, 131.7, 131.2, 130.5, 128.1, 127.7, 127.1, 120.8, 110.5, 72.9,
70.8, 55.3, 28.0, 26.0, 18.3.
13C NMR (100 MHz, CDCl3) δ 140.5, 138.6, 137.0, 131.3, 130.6, 128.5,
128.2, 127.9, 127.7, 120.7, 72.4, 70.7, 27.2, 26.3, 17.3.
6-(4-Nitrophenylamino)-1-(4-bromophenyl)cyclohexene (5e): yel-
low solid; mp 130ꢀ133 °C; IR (film) 3372, 1598, 1313, 1111 cmꢀ1; 1H
NMR (400 MHz, CDCl3) δ 8.08 (d, J = 9.2 Hz, 2H), 7.40 (d, J = 8.8 Hz,
2H), 7.21 (d, J = 8.8 Hz, 2H), 6.55 (d, J = 9.2 Hz, 2H), 6.39 (dd, J = 4.4,
3.2 Hz, 1H), 4.56ꢀ4.47 (m, 2H), 2.38ꢀ2.17 (m, 2H), 2.14ꢀ2.06 (m,
1H), 1.84ꢀ1.60 (m, 3H); 13C NMR (100 MHz, CDCl3) δ 152.1, 138.6,
138.3, 135.2, 131.9, 130.9, 127.2, 126.8, 121.5, 111.4, 48.2, 27.8, 26.0,
17.3. Anal. Calcd for C18H17BrN2O2: C, 57.92; H, 4.59; N, 7.51. Found:
C, 57.75; H, 4.67; N, 7.13.
6-Benzyloxy-1-(1-naphthyl)cyclohexene (4f):7 pale yellow oil; IR
(film) 1453, 1066 cmꢀ1; 1H NMR (400 MHz, CDCl3) δ 8.01 (d, J = 8.0
Hz, 1H), 7.90ꢀ7.86 (m, 1H), 7.80 (d, J = 8.0 Hz, 1H), 7.50ꢀ7.43 (m,
3H), 7.40ꢀ7.37 (m, 1H), 7.15ꢀ7.05 (m, 3H), 6.90ꢀ6.85 (m, 2H), 5.95
(t, J = 3.6 Hz, 1H), 4.35 (d, J = 12.0 Hz, 1H), 4.27ꢀ4.22 (m, 1H), 4.16
(d, J = 12.0 Hz, 1H), 2.42ꢀ2.32 (m, 1H), 2.30ꢀ2.13 (m, 2H),
2.08ꢀ1.87 (m, 2H), 1.83ꢀ1.73 (m, 1H); 13C NMR (100 MHz, CDCl3)
δ 140.8, 138.9, 138.2, 133.9, 132.4, 131.8, 128.3, 128.1, 127.6, 127.2,
127.1, 126.4, 126.2, 125.7, 125.6, 125.4, 75.1, 71.5, 28.4, 25.9, 18.0.
6-(4-Nitrophenylamino)-1-(1-naphthyl)cyclohexene (5f): yellow
6-(4-Nitrophenylamino)-1-(2-methoxyphenyl)cyclohexene (5b).
yellow solid; mp 124ꢀ126 °C; IR (film) 3378, 1598, 1310,
1111 cmꢀ1; 1H NMR (400 MHz, CDCl3) δ 7.97 (d, J = 9.2 Hz, 2H),
7.24ꢀ7.18 (m, 1H), 7.13ꢀ7.08 (m, 1H), 6.89 (t, J = 3.2 Hz, 1H), 6.79
(d, J = 8.0 Hz, 1H), 6.38 (d, J = 9.2 Hz, 2H), 5.93 (dd, J = 3.6, 3.2 Hz,
1H), 4.74 (d, J = 7.6 Hz, 1H), 4.65ꢀ4.58 (m, 1H), 3.74 (s, 3H),
2.30ꢀ2.15 (m, 2H), 2.05ꢀ1.94 (m, 1H), 1.92ꢀ1.83 (m, 1H),
1.85ꢀ1.71 (m, 2H); 13C NMR (100 MHz, CDCl3) δ 156.8, 153.1,
137.5, 137.0, 131.4, 130.7, 130.6, 128.9, 126.6, 121.0, 111.2, 110.8, 55.6,
50.8, 28.9, 25.7, 18.7. Anal. Calcd for C19H20N2O3: C, 70.35; H, 6.21; N,
8.64. Found: C, 70.21; H, 6.37; N, 8.34.
1
solid; mp 167ꢀ171 °C; IR (film) 3372, 1598, 1306, 1111 cmꢀ1; H
NMR (400 MHz, CDCl3) δ 7.97ꢀ7.93 (m, 1H), 7.88ꢀ7.80 (m, 3H),
7.74ꢀ7.70 (m, 1H), 7.54ꢀ7.44 (m, 2H), 7.38ꢀ7.33 (m, 1H),
7.28ꢀ7.24 (m, 1H), 6.26 (d, J = 9.2 Hz, 2H), 6.04 (t, J = 3.6 Hz,
1H), 4.54ꢀ4.43 (m, 2H), 2.43ꢀ2.25 (m, 2H), 2.12ꢀ2.02 (m, 2H),
1.90ꢀ1.72 (m, 2H); 13C NMR (100 MHz, CDCl3) δ 152.5, 139.4,
137.8, 136.8, 134.0, 133.0, 132.1, 128.9, 127.9, 126.3, 126.04, 125.98,
125.4, 125.0, 111.4, 51.5, 28.6, 25.6, 18.0; HRMS calcd for
C22H20N2O2 (M+) 344.1525, found 344.1529.
6-Benzyloxy-1-(3-methoxyphenyl)cyclohexene (4c):7 pale yellow
1
oil; IR (film) 1598, 1453, 1285, 1051 cmꢀ1; H NMR (400 MHz,
CDCl3) δ 7.28ꢀ7.17 (m, 6H), 6.96ꢀ6.92 (m, 2H), 6.80ꢀ6.76 (m, 1H),
6.18 (dd, J = 4.4, 3.2 Hz, 1H), 4.60 (d, J = 11.6 Hz, 1H), 4.47 (d, J = 11.6
Hz, 1H), 4.40ꢀ4.36 (m, 1H), 3.75 (s, 3H), 2.34ꢀ2.24 (m, 1H),
2.23ꢀ2.08 (m, 2H), 1.95ꢀ1.82 (m, 1H), 1.71ꢀ1.60 (m, 2H); 13C
NMR (100 MHz, CDCl3) δ 159.7, 143.3, 138.9, 137.9, 130.2, 129.2,
128.4, 128.0, 127.5, 118.8, 112.6, 111.8, 72.8, 70.9, 55.3, 27.4, 26.2, 17.3.
6-(4-Nitrophenylamino)-1-(3-methoxyphenyl)cyclohexene (5c):
6-Benzyloxy-1-(3-thiophene-yl)cyclohexene (4g):7 yellow oil; IR
(film) 1453, 1349, 1068 cmꢀ1 1H NMR (400 MHz, CDCl3) δ
;
7.35ꢀ7.23 (m, 5H), 7.22ꢀ7.18 (m, 1H), 7.17ꢀ7.14 (m, 1H), 7.08ꢀ7.05
(m, 1H), 6.28(dd, J= 4.8, 3.2 Hz, 1H), 4.66 (d, J= 11.6 Hz, 1H), 4.52 (d, J=
11.6 Hz, 1H), 4.35ꢀ4.31 (m, 1H), 2.33ꢀ2.09 (m, 3H), 1.94ꢀ1.80 (m, 1H),
1.69ꢀ1.57 (m, 2H); 13C NMR (100 MHz, CDCl3) δ 142.5, 138.7, 132.8,
128.7, 128.4, 128.1, 127.6, 125.8, 124.9, 119.2, 73.0, 70.6, 26.8, 26.0, 17.2.
6-(4-Nitrophenylamino)-1-(3-thiophene-yl)cyclohexene (5g): yel-
low solid; mp 164ꢀ166 °C; IR (film) 3381, 1599, 1307, 1111 cmꢀ1; 1H
NMR (400 MHz, CDCl3) δ 8.12 (d, J = 9.2 Hz, 2H), 7.28ꢀ7.24 (m, 1H),
7.20ꢀ7.17 (m, 1H), 7.05ꢀ7.02 (m, 1H), 6.58 (d, J = 9.2 Hz, 2H), 6.44
(dd, J = 4.4, 3.2 Hz, 1H), 4.64 (d, J = 6.8 Hz, 1H), 4.51ꢀ4.44 (m, 1H),
2.38ꢀ2.17 (m, 2H), 2.15ꢀ2.06 (m, 1H), 1.80ꢀ1.60 (m, 3H); 13C NMR
(100 MHz, CDCl3) δ 152.3, 141.3, 138.2, 131.4, 128.9, 126.9, 126.1, 125.0,
119.3, 111.3, 49.0, 27.7, 25.7, 17.3. Anal. Calcd for C16H16N2O2S: C, 63.98;
H, 5.37; N, 9.33. Found: C, 63.93; H, 5.47; N, 9.14.
yellow solid; mp 98ꢀ101 °C; IR (film) 3372, 1598, 1306, 1111 cmꢀ1
;
1H NMR (400 MHz, CDCl3) δ 8.08 (d, J = 9.2 Hz, 2H), 7.23ꢀ7.17 (m,
1H), 6.97ꢀ6.92 (m, 1H), 6.90ꢀ6.88 (m, 1H), 6.82ꢀ6.76 (m, 1H), 6.55
(d, J = 9.2 Hz, 2H), 6.40 (dd, J = 4.4, 3.6 Hz, 1H), 4.59ꢀ4.52 (m, 2H),
3.73 (s, 3H), 2.39ꢀ2.18 (m, 2H), 2.14ꢀ2.04 (m, 1H), 1.84ꢀ1.60 (m,
3H); 13C NMR (100 MHz, CDCl3) δ 160.0, 152.3, 141.3, 138.2, 136.0,
130.5, 129.8, 126.8, 118.0, 112.8, 111.7, 111.4, 55.4, 48.5, 28.0, 26.0, 17.4.
Anal. Calcd for C19H20N2O3: C, 70.35; H, 6.21; N, 8.64. Found: C,
70.61; H, 6.38; N, 8.24.
6-Benzyloxy-1-(4-methoxyphenyl)cyclohexene (4d):7 pale yellow
1
oil; IR (film) 1607, 1511, 1453, 1248, 1038 cmꢀ1; H NMR (400
MHz, CDCl3) δ 7.32ꢀ7.18 (m, 7H), 6.81 (d, J = 8.8 Hz, 2H), 6.10 (dd,
J = 4.4, 3.6 Hz, 1H), 4.59 (d, J = 11.6 Hz, 1H), 4.47 (d, J = 11.6 Hz, 1H),
4.39ꢀ4.34 (m, 1H), 3.80 (s, 3H), 2.32ꢀ2.09 (m, 3H), 1.93ꢀ1.80 (m,
1H), 1.70ꢀ1.59 (m, 2H); 13C NMR (100 MHz, CDCl3) δ 158.7, 138.9,
137.2, 134.2, 128.5, 128.4, 128.1, 127.5, 127.2, 113.7, 72.7, 70.7, 55.4,
27.3, 26.2, 17.4.
7-Benzyloxy-1-phenylcycloheptene (4h):7 pale yellow oil; IR (film)
1492, 1444, 1089 cmꢀ1; 1H NMR (400 MHz, CDCl3) δ 7.35ꢀ7.20 (m,
10H), 6.17 (dd, J = 7.6, 6.0 Hz, 1H), 4.52ꢀ4.45 (m, 2H), 4.39 (d, J =
11.6 Hz, 1H), 2.66ꢀ2.56 (m, 1H), 2.25ꢀ2.10 (m, 3H), 1.85ꢀ1.70 (m,
3H), 1.60ꢀ1.48 (m, 1H); 13C NMR (100 MHz, CDCl3) δ 144.8, 144.0,
139.1, 133.8, 128.4, 128.2, 127.8, 127.4, 126.6, 126.5, 79.3, 70.6, 31.4,
27.8, 27.1, 26.0.
6-(4-Nitrophenylamino)-1-(4-methoxyphenyl)cyclohexene (5d):
yellow solid; mp 103ꢀ106 °C; IR (film) 3371, 1598, 1304, 1111 cmꢀ1
;
1H NMR (400 MHz, CDCl3) δ 8.08 (d, J = 9.2 Hz, 2H), 7.27 (d, J = 8.8
Hz, 2H), 6.82 (d, J = 8.8 Hz, 2H), 6.54 (d, J = 9.2 Hz, 2H), 6.30 (dd, J =
4.4, 3.6 Hz, 1H), 4.56ꢀ4.51 (m, 2H), 3.77 (s, 3H), 2.37ꢀ2.17 (m, 2H),
2.14ꢀ2.06 (m, 1H), 1.83ꢀ1.59 (m, 3H); 13C NMR (100 MHz, CDCl3)
δ 159.2, 152.4, 138.1, 135.4, 132.1, 128.4, 126.8, 126.6, 114.2, 111.4, 55.5,
48.4, 27.9, 26.0, 17.4. Anal. Calcd for C19H20N2O3: C, 70.35; H, 6.21; N,
8.64. Found: C, 70.41; H, 6.14; N, 8.30.
7-(4-Nitrophenylamino)-1-phenylcycloheptene (5h): yellow solid;
1
mp 106ꢀ107 °C; IR (film) 3384, 1599, 1305, 1111 cmꢀ1; H NMR
(400 MHz, CDCl3) δ 8.04 (d, J = 9.2 Hz, 2H), 7.30ꢀ7.18 (m, 5H), 6.48
(d, J = 9.2 Hz, 2H), 6.13 (t, J = 6.8 Hz, 1H), 4.75ꢀ4.63 (m, 2H),
2.45ꢀ2.37 (m, 2H), 2.23ꢀ2.13 (m, 1H), 1.97ꢀ1.80 (m, 3H),
1.80ꢀ1.60 (m, 2H); 13C NMR (100 MHz, CDCl3) δ 152.3, 144.7,
142.9, 138.2, 133.2, 128.6, 127.3, 126.7, 126.4, 111.5, 56.0, 30.6, 28.1,
26.9, 26.0; HRMS calcd for C19H20N2O2 (M+) 308.1525, found
308.1528.
6-Benzyloxy-1-(4-bromophenyl)cyclohexene (4e):7 white solid; mp
1
47ꢀ48 °C; IR (film) 1453, 1142, 1071 cmꢀ1; H NMR (400 MHz,
CDCl3) δ 7.39ꢀ7.35 (m, 2H), 7.30ꢀ7.17 (m, 7H), 6.17 (dd, J = 4.4, 3.2
Hz, 1H), 4.59 (d, J = 12.0 Hz, 1H), 4.44 (d, J = 12.0 Hz, 1H), 4.35ꢀ4.31
(m, 1H), 2.34ꢀ2.08 (m, 3H), 1.93ꢀ1.80 (m, 1H), 1.71ꢀ1.61 (m, 2H);
5-Benzyloxy-1-phenylcyclopentene (4i):7 yellow oil; IR (film) 1496,
1
1452, 1142, 1068 cmꢀ1; H NMR (400 MHz, CDCl3) δ 7.52ꢀ7.48
7272
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The Journal of Organic Chemistry
NOTE
(m, 2H), 7.33ꢀ7.20 (m, 8H), 6.38 (t, J = 2.4 Hz, 1H), 5.10ꢀ5.05
(m, 1H), 4.57 (d, J = 11.6 Hz, 1H), 4.49 (d, J = 11.6 Hz, 1H), 2.73ꢀ2.63
(m, 1H), 2.49ꢀ2.39 (m, 1H), 2.30ꢀ2.18 (m, 1H), 2.17ꢀ2.08 (m, 1H);
13C NMR (100 MHz, CDCl3) δ 142.5, 138.8, 135.5, 131.3, 128.5, 128.2,
127.7, 127.3, 126.4, 83.9, 69.8, 31.2, 29.9.
6-Butoxy-1-phenylcyclohexene (Table 1, entry 18):7 pale yellow oil;
IR (film) 1445, 1091 cmꢀ1; 1H NMR (400 MHz, CDCl3) 7.45ꢀ7.39
(m, 2H), 7.33ꢀ7.27 (m, 2H), 7.24ꢀ7.17 (m, 1H), 6.19 (dd, J = 4.4, 3.6
Hz, 1H), 4.23ꢀ4.18 (m, 1H), 3.57 (dt, J = 8.8, 6.4 Hz, 1H), 3.37 (dt, J =
8.8, 6.4 Hz, 1H), 2.32ꢀ2.22 (m, 1H), 2.19ꢀ2.08 (m, 2H), 1.90ꢀ1.77
(m, 1H), 1.67ꢀ1.47 (m, 4H), 1.35ꢀ1.23 (m, 2H), 0.85 (t, J = 7.2 Hz,
3H); 13C NMR (100 MHz, CDCl3) δ 141.7, 137.8, 129.5, 128.2, 126.8,
126.0, 73.2, 68.7, 32.5, 27.2, 26.3, 19.6, 17.2, 14.0.
5-(4-Nitrophenylamino)-1-phenylcyclopentene (5i): yellow solid;
1
mp 127ꢀ128 °C; IR (film) 3361, 1599, 1306, 1111 cmꢀ1; H NMR
(400 MHz, CDCl3) δ 8.10 (d, J = 8.8 Hz, 2H), 7.45ꢀ7.40 (m, 2H),
7.35ꢀ7.29 (m, 2H), 7.29ꢀ7.23 (m, 1H), 6.56 (d, J = 8.8 Hz, 2H),
6.49ꢀ6.45 (m, 1H), 5.02ꢀ4.96 (m, 1H), 4.57 (d, J = 6.8 Hz, 1H),
2.74ꢀ2.63 (m, 1H), 2.62ꢀ2.52 (m, 1H), 2.51ꢀ2.40 (m, 1H), 2.05ꢀ1.96
(m, 1H); 13C NMR (100 MHz, CDCl3) δ152.8, 141.8, 138.2, 134.1, 131.4,
129.0, 128.0, 126.7, 126.2, 111.6, 59.1, 31.7, 31.2. Anal. Calcd for
C17H16N2O2: C, 72.84; H, 5.75; N, 9.99; Found: C, 72.78; H, 5.83; N, 9.90.
(E)-5-Benzyloxy-4-phenyl-3-heptene (4j): pale yellow oil; IR (film)
1454, 1308, 1067 cmꢀ1; 1H NMR (400 MHz, CDCl3) δ 7.42ꢀ7.20 (m,
8H), 7.17 (d, J = 7.6 Hz, 2H), 5.66 (dd, J = 7.6, 7.2 Hz, 1H), 4.77 (d, J =
12.0 Hz, 1H), 4.47 (d, J = 12.0 Hz, 1H), 3.80 (t, J = 6.4 Hz, 1H),
2.06ꢀ1.93 (m, 2H), 1.50ꢀ1.40 (m, 2H), 0.97 (t, J = 7.6 Hz, 3H), 0.86 (t,
J = 7.6 Hz, 3H); 13C NMR (100 MHz, CDCl3) δ 139.2, 139.0, 138.7,
133.5, 129.4, 128.5, 128.1, 128.0, 127.6, 126.9, 86.0, 70.1, 27.5, 22.2, 14.8,
10.5; HRMS calcd for C20H24O (M+) 280.1827, found 280.1831.
(E)-5-(4-Nitrophenylamino)-4-phenyl-3-heptene (5j): yellow solid;
mp 80ꢀ82 °C; IR (film) 3373, 1600, 1307, 1112 cmꢀ1; 1H NMR (400
MHz, CDCl3) δ 8.12 (d, J = 9.2 Hz, 2H), 7.36ꢀ7.27 (m, 3H), 6.98 (d,
J = 7.2 Hz, 2H), 6.60 (d, J = 9.2 Hz, 2H), 5.69 (dd, J = 7.6, 7.2 Hz, 1H),
4.38 (d, J = 7.6 Hz, 1H), 3.98 (q, J = 7.2 Hz, 1H), 1.92ꢀ1.78 (m, 2H),
1.70ꢀ1.47 (m, 2H), 1.04 (t, J = 7.6 Hz, 3H), 0.90 (t, J = 7.6 Hz, 3H); 13C
NMR (100 MHz, CDCl3) δ 153.2, 138.5, 138.0, 137.9, 133.2, 129.2,
128.3, 127.3, 126.5, 112.0, 61.9, 27.4, 22.2, 14.6, 10.9; HRMS calcd for
C19H22N2O2 (M+) 310.1681, found 310.1685.
6-(3-Chloropropoxy)-1-phenylcyclohexene (Table 1, entry 19): pale
yellow oil; IR (film) 1599, 1444, 1354, 1093 cmꢀ1; 1H NMR (400 MHz,
CDCl3) 7.43ꢀ7.37 (m, 2H), 7.34ꢀ7.27 (m, 2H), 7.26ꢀ7.19 (m, 1H),
6.21 (dd, J = 4.4, 3.2 Hz, 1H), 4.32ꢀ4.26 (m, 1H), 3.76ꢀ3.68 (m, 1H),
3.56ꢀ3.41 (m, 3H), 2.33ꢀ2.22 (m, 1H), 2.20ꢀ2.08 (m, 2H),
1.97ꢀ1.88 (m, 2H), 1.86ꢀ1.73 (m, 1H), 1.70ꢀ1.59 (m, 2H); 13C
NMR (100 MHz, CDCl3) δ 141.3, 137.6, 129.6, 128.4, 127.0, 126.0,
73.5, 64.9, 42.3, 33.2, 27.3, 26.3, 17.4. Anal. Calcd for C15H19ClO: C,
71.84; H, 7.64. Found: C, 71.81; H, 7.66.
Procedure for Scheme 4. To a Schlenk tube charged with
condenser were added FeCl3 (0.0041 g, 0.025 mmol), NaI (0.0075 g,
n
0.050 mmol), PrSSnPr (0.0075 g, 0.050 mmol), 6a (0.085 g, 0.25
mmol) (prepared according to the reported procedure7), and CHCl3
(0.25 mL). The resulting mixture was stirred at 60 °C under air for 18 h,
filtered through a plug of silica with CH2Cl2 as eluent, concentrated, and
analyzed by 1H NMR.
Procedure for Scheme 5. To a Schlenk tube charged with
condenser were added FeCl3 (0.0041 g, 0.025 mmol), NaI (0.0075 g,
0.050 mmol), nPrSSnPr (0.0075 g, 0.050 mmol), BnOH (0.054 g, 0.50
mmol), 7a (0.058 g, 0.25 mmol) (prepared according to the reported
procedure7), and CHCl3 (0.25 mL). The resulting mixture was stirred at
60 °C under air for 18 h, filtered through a plug of silica with CH2Cl2 as
eluent, concentrated, and analyzed by 1H NMR.
(E)-5-Benzyloxy-4-(3-thiophene-yl)-3-heptene (4k): yellow oil; IR
Procedure for Scheme 6. To a Schlenk tube charged with
condenser were added FeCl3 (0.0041 g, 0.025 mmol), NaI (0.0075 g,
0.050 mmol), nPrSSnPr (0.0075 g, 0.050 mmol), BnOH (0.054 g, 0.50
mmol), deuterium-labeled 1-phenylcyclohexene (0.0395 g, 0.25 mmol,
1l:1m = 80:20) (prepared according to the reported procedure7), and
CHCl3 (0.25 mL). The resulting mixture was stirred at 60 °C under air
for 4 h, filtered through a plug of silica with CH2Cl2 as eluent,
concentrated, and analyzed by 1H NMR. The crude product contained
1:1 mixture of 8 and 9 along with unreacted 1l and 1m (1l/1m = 70:30)
(56% conversion).
(film) 1454, 1377, 1067 cmꢀ1 1H NMR (400 MHz, CDCl3) δ
;
7.42ꢀ7.20 (m, 6H), 7.13ꢀ7.10 (m, 1H), 7.04ꢀ6.99 (m, 1H), 5.66 (t,
J = 7.2 Hz, 1H), 4.72 (d, J = 12.0 Hz, 1H), 4.44 (d, J = 12.0 Hz, 1H), 3.77
(t, J = 6.8 Hz, 1H), 2.19ꢀ2.08 (m, 2H), 1.62ꢀ1.35 (m, 2H), 1.01 (t, J =
7.6 Hz, 3H), 0.83 (t, J = 7.6 Hz, 3H); 13C NMR (100 MHz, CDCl3) δ
139.2, 137.9, 134.9, 134.0, 129.1, 128.6, 128.0, 127.6, 124.5, 122.8, 86.3,
69.9, 27.4, 22.5, 14.8, 10.5; HRMS (ESI) calcd for C18H22OS (M + Na)
309.1284, found 309.1284.
(E)-5-(4-Nitrophenylamino)-4-(3-thiophene-yl)-3-heptene (5k):
1
yellow oil; IR (film) 3373, 1600, 1308, 1112 cmꢀ1; H NMR (400
MHz, CDCl3) δ 8.08 (d, J = 7.6 Hz, 2H), 7.31ꢀ7.27 (m, 1H), 6.90ꢀ6.87
(m, 1H), 6.80ꢀ6.76 (m, 1H), 6.57 (d, J = 7.6 Hz, 2H), 5.71 (t, J = 7.2 Hz,
1H), 4.48 (d, J = 7.2 Hz, 1H), 3.94 (q, J = 7.2 Hz, 1H), 1.98ꢀ1.88 (m,
2H), 1.66ꢀ1.52 (m, 2H), 1.00 (t, J = 7.2Hz, 3H), 0.91 (t, J = 7.2 Hz, 3H);
13C NMR (100 MHz, CDCl3) δ 153.0, 138.2, 137.4, 134.5, 133.8, 128.7,
126.5, 125.4, 122.8, 112.1, 61.8, 27.7, 22.4, 14.6, 11.0; HRMS (ESI) calcd
for C17H20N2O2S (M + Na) 339.1138, found 339.1140.
’ ASSOCIATED CONTENT
Supporting Information. 1HNMRand13CNMRspectra.
S
b
This material is available free of charge via the Internet at
http://pubs.acs.org.
6-Methoxy-1-phenylcyclohexene (Table 1, entry 16):7 pale yellow
’ AUTHOR INFORMATION
oil; IR (film) 1455, 1071 cmꢀ1 1H NMR (400 MHz, CDCl3) δ
;
Corresponding Author
*E-mail: yian@lamar.colostate.edu.
7.44ꢀ7.38 (m, 2H), 7.33ꢀ7.27 (m, 2H), 7.26ꢀ7.21 (m, 1H), 6.19
(dd, J = 4.4, 3.2 Hz, 1H), 4.18ꢀ4.14 (m, 1H), 3.34 (s, 3H), 2.33ꢀ2.23
(m, 1H), 2.20ꢀ2.09 (m, 2H), 1.88ꢀ1.74 (m, 1H), 1.67ꢀ1.55 (m, 2H);
13C NMR (100 MHz, CDCl3) δ 141.6, 137.6, 129.7, 128.4, 126.9, 126.0,
74.5, 56.5, 29.5, 26.3, 17.1.
’ ACKNOWLEDGMENT
6-Isopropoxy-1-phenylcyclohexene (Table 1, entry 17):7 pale yellow
We gratefully acknowledge the National Basic Research
Program of China (973 program, 2011CB808600) and the
Chinese Academy of Sciences for financial support.
1
oil; IR (film) 1599, 1444, 1064 cmꢀ1; H NMR (400 MHz, CDCl3)
7.48ꢀ7.40 (m, 2H), 7.32ꢀ7.25 (m, 2H), 7.23ꢀ7.18 (m, 1H), 6.09 (dd, J
= 4.4, 3.2 Hz, 1H), 4.36ꢀ4.29 (m, 1H), 3.68 (septet, J = 6.0 Hz, 1H),
2.32ꢀ2.22 (m, 1H), 2.18ꢀ2.03 (m, 2H), 1.92ꢀ1.78 (m, 1H),
1.67ꢀ1.56 (m, 2H), 1.15 (d, J = 6.0 Hz, 3H), 1.03 (d, J = 6.0 Hz,
3H); 13C NMR (100 MHz, CDCl3) δ 142.2, 138.6, 129.9, 128.2, 126.7,
126.6, 71.2, 70.0, 28.6, 26.3, 24.2, 22.4, 17.0.
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The Journal of Organic Chemistry
NOTE
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(11) When the reaction was carried out under N2, only 6.8%
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(12) As shown in Table 1, entry 5, the oxidation product was also
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likely involving I2 might be operating in the absence of disulfide, but with
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