Efficient catalytic-free method to produce α-aryl cycloalkanones through highly chemoselective coupling of aryl compounds with oxyallyl cations

Article abstract of DOI:10.1039/c4ra01043d

Catalytic-free coupling of aryl compounds and α-halo cycloketones via in situ generated oxyallyl cation intermediates is reported here. The reactions efficiently afford α-naphthol cycloalkanones with moderate to excellent yields. Electron-rich aromatic compounds are also used to produce the corresponding α-aryl cycloalkanones, and in some cases, analytically pure products are obtained after simple filtration followed by evaporation.

Full text of DOI:10.1039/c4ra01043d

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Efficient catalytic-free method to produce a-aryl
cycloalkanones through highly chemoselective
coupling of aryl compounds with oxyallyl cations†
Cite this: RSC Adv., 2014, 4, 17370
a
a
c
ab
Juan Luo,ab Hui Zhou, Jiwei Hu, Rui Wang and Qiang Tang
*
Catalytic-free coupling of aryl compounds and a-halo cycloketones via in situ generated oxyallyl cation
intermediates is reported here. The reactions efficiently afford a-naphthol cycloalkanones with moderate
to excellent yields. Electron-rich aromatic compounds are also used to produce the corresponding a-
aryl cycloalkanones, and in some cases, analytically pure products are obtained after simple filtration
followed by evaporation.
Received 6th February 2014
Accepted 24th March 2014
DOI: 10.1039/c4ra01043d
www.rsc.org/advances
Introduction
a-Aryl cycloalkanones are important building blocks for concise
preparation of medicines or organic functional materials, such
as naphthonone,1 brazan,2 and electroluminescence devices.3
The synthesis of a-aryl cycloalkanones, particularly a-naphthol
cycloalkanones, can be realized by nucleophilic substitution of
a-hydroxylketones with oxygen protected naphthols via
Grignard reagents and nal deprotection,4 or by direct electro-
philic substitution of a-hydroxylketones with phenols under
acidic conditions.5 a-Arylation of b-dicarbonyl compounds, as a
powerful technology, needs to be catalyzed by transition
metals,6 organocatalysts7 or enzymes.8 Pappo and colleagues
have recently reported an efficient cross-dehydrogenative
coupling reaction between phenols and a-substituted
b-ketoesters catalyzed by iron trichloride.9
It has been reported that reaction of b-naphthol with
a-cyclohexanone in xylene under reuxing temperature produces
compound V directly.10 However, a high temperature is neces-
sary, the yield is moderate (22–57%), and a large amount of by-
product III is evolved. It is worth noting that direct substitution of
a-haloketones with naphthols under basic conditions produces
phenol ethers III (Scheme 1) as the main product.11
Scheme
naphthols.
1 Different reaction pathways of a-haloketones with
The literature is replete with examples of cycloaddition reac-
tions of such species, especially (4 + 3) cycloaddition reactions.13
Moreover, aromatic groups have been extensively used to trap
oxyallyl cations in the context of Nazarov cyclization.14 However,
there are only a few reports on the interrupted cycloaddition
reactions of aromatic compounds with oxyallyl cations derived
from a-halo ketones.15 Recently, MacMillan and colleagues and
ourselves both reported an efficient synthesis of a-indole
carbonyl compounds via electrophilic aromatic substitution of
unprotected indoles to in situ generated oxyallyl cations.16 To
further expand the reaction scope, we started to use naphthols
as nucleophiles to react with oxyallyl cations generated from
a-halo cycloalkanones. To our delight, the reaction proceeded
smoothly and produced a-naphthol cycloalkanones IV (Scheme
1) which are eventually transformed to product V (Scheme 1)
with high yield.
Here we report an efficient catalyst-free coupling of unpro-
tected naphthols and oxyallyl cation intermediates generated
from a-halocycloketones at room temperature. Oxyallyl cations
have been extensively explored for more than half a century.12
aChongqing Key Laboratory of Biochemistry and Molecular Pharmacology, College of
Pharmacy, Chongqing Medical University, Chongqing 400016, P. R. China. E-mail:
tangqiang@cqmu.edu.cn
Results and discussion
bThe Faculty of Laboratory Medicine, Chongqing Medical University, Chongqing
401331, P. R. China
We rst explored the reaction between 2-chlorocyclohexanone
(Ia) and 2-naphthol (IIb). At room temperature, most of the
starting materials remain unreacted in common organic
solvents such as DMF, DMSO, THF, toluene, Et2O, CH2Cl2,
cSchool of Pharmacy
& Bioengineering, Chongqing University of Technology,
Chongqing 400054, P. R. China
† Electronic supplementary information (ESI) available: Chemical shis
assignments, and spectral data for compounds. See DOI: 10.1039/c4ra01043d
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Table 1 Model reaction optimizationa
Entry
Base
Solvent
Temperature (ꢀC)
Time (h)
Productb (yield%)
1
2
3
4
5
6
7
8
Na2CO3
Na2CO3
Na2CO3
Na2CO3
Na2CO3
Na2CO3
Na2CO3
NaHCO3
NaOH
Solventsc
Xylene
Xylene
H2O
TFE
TFE
HFIP
TFE
TFE
TFE
TFE
25
25
140
25
25
80
25
25
25
25
25
48
48
24
12
12
10
10
48
4
1 (<5)
1 (<5)
1/2 (42/33)d
1/3 (8/85)d
1 (91)e
1/4 (88/5)d
1 (86)e
1 (<5)
9
10
11
1/5 (48/5)d
1/4 (71/6)d
1/4 (80/6)d
Pyrrolidine
Et3N
48
48
Reaction condition: I (0.5 mmol), II (0.5 mmol), base (0.6 mmol) in solvent (1 mL). b Isolated yields. c DMF, DMSO, THF, Et2O, toluene, CH2Cl2,
EtOAc, CH3CN. d Yield of minor product was determined by crude NMR integration. e No other product was isolated. TFE ¼ 2,2,2-triuoroethanol;
HFIP ¼ hexauoro-2-propanol.
a
EtOAc, CH3CN, toluene and xylene (Table 1, entries 1 and 2). the substitution position of bromo is (Table 2, entries 3–5). For
Although cough medicine, product 1, is evolved when xylene is a-naphthols, the reaction shows excellent chemoselectivity,
used as a solvent under high temperature, 33% yield of ether by- naphthols are regioselectively alkylated at C-4, and no C-2
product 2, which is not transformed to product 1 within the alkylated product is obtained (Table 2, entries 7 and 8). To
prolonged reaction time, is also obtained (Table 1, entry 3). In further examine the regioselectivity, 4-chloro-1-naphthol was
the case where water was used as a solvent, hydrolysis of selected as substrate (Table 2, entry 8). No C-2 alkylated product
2-chlorocyclohexanone becomes the preferred reaction pathway was detected under our standard reaction conditions. Most of
to produce compound 3 serving as the main product,17 while the starting material is recovered aer reacting for 12 h.
very little of compound 1 could be isolated (Table 1, entry 4).
Noncyclic haloketones were also examined. Unfortunately,
Owing to their high ionizing power and low nucleophilicity, when 1,1-dichloropropan-2-one or 1,3-dichloropropan-2-one
uorinated alcohols, such as triuoroethanol (TFE) and hexa- was used, we found that most of the 2-naphthol remained
uoro isopropanol (HFIP), are the best solvents for generation unreacted. Similarly, for substrates 1,3-dibromo-3-methyl-
of oxyallyl cations.18 So the uorinated alcohols were then butan-2-one and 1-chloro-1,3-diphenylpropan-2-one, a small
evaluated (Table 1, entries 5–11). Under the reaction conditions amount of 2-naphthol is consumed without isolating any
of Na2CO3 in TFE at room temperature, a clean reaction with desired products. Only 2-bromo-3-pentanone produces a small
high yield is realized (Table 1, entry 5). Higher temperature amount of condensed product 14 in the presence of excessive
(Table 1, entry 6) or higher ionizing power (Table 1, entry 7) is haloketone (Table 2, entry 10).
benecial for the reaction rate rather than the reaction effi-
To explore the reaction scope further, we screened different
ciency. With TFE as the solvent, the choice of base has a hydroxyquinolines, wherein 5-hydroxy and 7-hydroxy isoquino-
signicant effect on the reaction purity and yield. Organic line gave acceptable yields of a-aryl cycloalkanones along with
bases, e.g. pyrrolidine and Et3N, effectively initiate the reaction their corresponding ether products III (Table 3, entries 1 and 2).
(Table 1, entries 10 and 11). However, when a relatively weak It should be noted that product 16 is the ketone isomer, not the
base, e.g. sodium bicarbonate, was chosen, virtually no reaction hemiketal form. When excessive haloketone Ib was used,
takes place (Table 1, entry 8). In contrast, when a strong base, disubstituted product 22 was obtained as a mixture of stereo-
e.g. NaOH, was used, the reaction becomes complex with isomers (Table 3, entry 3).
formation of Favorskii rearrangement adduct 5 among the side
products (Table 1, entry 9).19
We think that the reaction mechanism is just like that of
Friedel–Cras alkylation, so we used different types of aromatic
Then we examined various naphthols in reaction with compound to react with 2-chlorocyclopentanone. We found that
2-chlorocyclopentanone. Both protected and unprotected an electron-rich system of aromatic compounds plays an
b-naphthols are alkylated at C-1 to produce compounds IV or V important role in the reaction efficiency. When phenol (IIm)
in moderate to excellent yields (Table 2, entries 1–6). Bromo- was used as a substrate, only ether product 23 is obtained
substituted naphthols show excellent outcomes no matter what (Table 4, entry 1). For the reaction of substrates IIn and IIo, the
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Table 2 Addition of naphthols to a-halo alkanonesa,b
Entry
1
Haloketone
Naphthol
Product
Yield
91% (dr > 20 : 1)c
2
3
4
5
92% (dr ¼ 10 : 1)c
93% (dr ¼ 10 : 1)c
93% (dr ¼ 8 : 1)c
94% (dr ¼ 8 : 1)c
6
7
8
9
88%
89%d,e
f
—
87%d,g
10
11%h,i
a
b
c
I (0.5 mmol), II (0.5 mol), Na2CO3 (0.6 mmol) in TFE (1 mL). Isolated yields. Ratio of diastereomers was determined by integration of
benzylic proton signals in 1H NMR spectrum. No another isomer was detected. The structure is conrmed by 2D NMR spectra (COSY,
d
e
HMQC and HMBC). No desired product is obtained. The 1H and C NMR spectra are the same as that reported in the literature.4a Ic (1.0
f
g
13
h
i
mmol), IIi (0.5 mol), Na2CO3 (1.1 mmol) in HFIP (1 mL). The ether product (15), 2-(naphthalen-2-yloxy)pentan-3-one, is also isolated.
main products are, respectively, ether 24 and amine 25, both of an almost quantitative reaction takes place. Aer simple ltra-
which are accompanied by several other complex compounds. tion followed by evaporation, analytically pure product 26 is
However, when the more electron-rich compound IIp was used, obtained (Table 4, entry 4). The reaction efficiency is
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Table 3 Addition of hydroxyquinolines to a-chloropentanonea
Table 4 Addition of aryl compounds to a-chloropentanonea,b
Entry
1
Aryl compounds
Product
Yield
46%
Entry
1b
Quinine
Product IV
Product III
Product VI
e
—
2
3
38%
32%
e
2b
—
4
5
99%
48%
3c
a
Isolated yield. b I (0.5 mmol), II (0.5 mol), Na2CO3 (0.6 mmol) in TFE (1
c
mL). I (1.5 mmol), II (0.5 mol), Na2CO3 (1.6 mmol) in TFE (1 mL).
d
Yield of product 15 was determined by integration of proton signals
in 1H NMR spectrum. Not detected. Ratio of diastereomers was
e
f
determined by integration of proton signals in 1H NMR spectrum.
c
6
—
g
The structure is conrmed by 2D NMR spectra (COSY, HMQC and
HMBC).
I (0.5 mmol), II (0.5 mol), Na2CO3 (0.6 mmol) in TFE (1 mL). b Isolated
a
yields. c Not detected.
dramatically lowered if there is an electron-withdrawing group
on the arene ring. Moderate yield is obtained in the presence of
substrate IIq, while no reaction occurs for substrate IIr (Table 4,
entries 5 and 6).
(400 MHz), AV500 (500 MHz) or BBFO400 (400 MHz) spec-
trometers. H NMR chemical shis were recorded in parts per
1
million (ppm, d) relative to tetramethylsilane (d 0.00) or DMSO
(d ¼ 2.50, singlet), and the splitting patterns were designated as
singlet (s), doublet (d), triplet (t), quartet (q), dd (doublet of
doublets); m (multiplets), etc. All rst-order splitting patterns
were assigned on the basis of the appearance of the multiplet.
Splitting patterns that could not be easily interpreted were
designated as multiplet (m) or broad (br). High resolution mass
spectral analysis (HRMS) was performed on a Finnigan MAT 95
XP mass spectrometer (Thermo Electron Corporation). Analyt-
ical thin-layer chromatography (TLC) was carried out on Merck
60 F254 pre-coated silica gel plates (0.2 mm thickness). Visu-
alization was performed using a UV lamp or chemical stains
such as KMnO4 and 2,4-dinitrophenyl hydrazine solutions.
Commercially available materials purchased from Alfa Aesar
or Aldrich were used as received, apart from a-haloketones that
were further puried via distillation or column chromatography
over silica gel prior to use. Some of the a-chloroketones
(2-bromo-3-pentanone and 1,3-dibromo-3-methylbutan-2-one)
were prepared using a literature method.20
Conclusions
We developed a highly efficient and practical method for che-
moselective coupling of a-halo cycloalkanones with electron-
rich aromatic compounds, especially naphthols, at room
temperature. No protection of naphthol substrates and no
catalysts are required in our protocol. a-Aryl cycloalkanone 26 is
obtained in quantitative yield, and analytically pure products
are obtained aer simple ltration followed by evaporation. An
electron-rich system of aryl compounds plays an important role
in the reaction efficiency. Further research on the interrupted
cycloaddition reaction of oxyallyl cations is being pursued in
our lab.
Experimental section
General information
Nuclear magnetic resonance spectra (1H and 13C) were recorded
on JEOL ECA400 (400 MHz), Bruker AV300 (300 MHz), AV400
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129.62, 129.35, 128.96, 126.78, 123.01, 122.44, 121.74, 121.24,
111.83, 51.48, 40.03, 32.71, 24.84 ppm. HRMS (ESI) calcd for
C
Typical procedure for metal-free coupling of aromatic
compounds with a-haloketones
15H15O2 (M + 1)+: 227.1072, found: 227.1069.
A 4 mL vial equipped with a magnetic stir bar was charged with
fresh distilled a-halo ketone I (0.5–1.5 mmol), aromatic
compound II (0.5 mmol) and TFE or HFIP (1.0 mL). Anhydrous
Na2CO3 (0.6–1.6 mmol) was added to the reaction mixture and
stirred at room temperature. Aer completion of the reaction
3-Bromo-8,9,10,10a-tetrahydro-7aH-cyclopenta[b]naphtha
1
ꢀ
[1,2-d]furan-7a-ol (7). White solid; Mp: 86–87 C; H NMR (400
MHz, CDCl3) d ¼ 7.94 (s, 1H), 7.58 (d, J ¼ 8.8 Hz, 1H), 7.49 (q, J ¼
8.7 Hz, 2H), 7.08 (d, J ¼ 8.8 Hz, 1H), 3.79 (d, J ¼ 8.9 Hz, 1H),
3.60–3.30 (brs, 1H), 2.48–2.17 (m, 2H), 2.10 (dd, J ¼ 18.1, 11.9
Hz, 1H), 1.94–1.73 (m, 2H), 1.74–1.52 (m, 2H) ppm. 13C NMR
(101 MHz, CDCl3) d ¼ 155.76, 130.87, 130.72, 130.03, 128.93,
128.53, 124.11, 121.86, 121.58, 116.51, 112.87, 51.38, 40.07,
32.78, 24.87 ppm. HRMS (ESI) calcd for C15H14BrO2 (M + 1)+:
306.1745, found: 306.1744.
1
(about 12–24 h, monitored by TLC or crude H NMR analysis),
the reaction mixture was ltered through a celite pad using Et2O
or CH2Cl2 and the ltrate was concentrated under reduced
pressure. The crude residue was further puried by silica gel
ash chromatography using EtOAc/hexanes as eluent to give
pure products. In some cases, analytically pure products could
be obtained merely by simple ltration and evaporation under
reduced pressure.
7a,8,9,10,11,11a-Hexahydronaphtho[2,1-b]benzofuran-7a-ol
(1). White solid, Mp: 136–137 ꢀC; 1H NMR (400 MHz, CDCl3) d ¼
7.81 (d, J ¼ 8.3 Hz, 1H), 7.69 (t, J ¼ 9.2 Hz, 2H), 7.45 (ddd, J ¼ 8.2,
6.9, 1.2 Hz, 1H), 7.31 (ddd, J ¼ 8.1, 6.8, 1.1 Hz, 1H), 7.17 (d, J ¼
8.7 Hz, 1H), 3.41 (dd, J ¼ 10.2, 6.8 Hz, 1H), 3.26 (d, J ¼ 3.1 Hz,
1H), 2.46–2.27 (m, 2H), 1.90 (ddd, J ¼ 14.1, 12.3, 5.2 Hz, 1H),
1.85–1.74 (m, 1H), 1.64–1.28 (m, 4H), 1.15 (dddd, J ¼ 14.0, 12.0,
10.3, 3.9 Hz, 1H) ppm. 13C NMR (100 MHz, CDCl3) d ¼ 154.23,
130.61, 129.91, 129.04, 126.72, 124.64, 123.18, 122.79, 113.05,
109.78, 46.62, 33.37, 30.86, 21.79, 21.76 ppm. HRMS (ESI) calcd
for C16H17O2 (M + 1)+: 241.1229, found: 241.1233.
2-(Naphthalen-2-yloxy)cyclohexanone (2).11a White solid, Mp:
104–106 ꢀC; 1H NMR (400 MHz, CDCl3) d ¼ 7.66 (dd, J ¼ 2.8, 9.2
Hz, 2H), 7.58 (d, J ¼ 8.0 Hz, 1H), 7.33 (t, J ¼ 7.2 Hz, 1H), 7.23 (t, J
¼ 7.2 Hz, 1H), 7.10 (dd, J ¼ 2.4, 8.8 Hz, 1H), 6.93 (d, J ¼ 2.0 Hz,
1H), 4.72–4.65 (m, 1H), 2.59–2.52 (m, 1H), 2.34–2.21 (m, 2H),
2.01–1.89 (m, 3H), 1.74–1.62 (m, 2H) ppm.
2-Hydroxycyclohexanone (3).21 White solid; Mp: 110–112 ꢀC;
1H NMR (400 MHz, CDCl3) d ¼ 4.13 (dd, J ¼ 11.9, 7.0 Hz, 1H),
3.64 (s, 1H), 2.57 (ddt, J ¼ 13.8, 4.3, 2.3 Hz, 1H), 2.52–2.43 (m,
1H), 2.36 (tdd, J ¼ 13.7, 6.4, 1.5 Hz, 1H), 2.16–2.06 (m, 1H), 1.96–
1.84 (m, 1H), 1.81–1.68 (m, 1H), 1.68–1.58 (m, 2H), 1.56–1.40
(m, 2H) ppm.
2-(2,2,2-Triuoroethoxy)cyclohexanone (4).22 Colorless oil;
1H NMR (400 MHz, CDCl3) d ¼ 4.20 (dq, J ¼ 12.7, 9.0 Hz, 1H),
4.01 (dd, J ¼ 10.4, 5.8 Hz, 1H), 3.76 (dq, J ¼ 12.7, 8.5 Hz, 1H),
2.58–2.45 (m, 1H), 2.30 (dtd, J ¼ 12.3, 5.4, 2.4 Hz, 2H), 2.08–1.88
(m, 2H), 1.85–1.62 (m, 3H) ppm. 13C NMR (101 MHz, CDCl3) d ¼
208.47, 128.00, 125.23, 122.45, 119.68, 83.86, 67.88, 67.54,
67.20, 66.86, 40.53, 34.23, 27.25, 23.22 ppm. HRMS (ESI) calcd
for C 8H12F3O2 (M + 1)+: 197.0789, found: 197.0784.
8,9,10,10a-Tetrahydro-7aH-cyclopenta [ꢀb] naphtha [1,2-d]
furan-7a-ol (6). White solid; Mp: 128–129 C; further purica-
tion could be realized by recrystallization using ethanol. 1H
NMR (400 MHz, CDCl3) d ¼ 7.80 (d, J ¼ 8.2 Hz, 1H), 7.69 (d, J ¼
8.8 Hz, 1H), 7.63 (d, J ¼ 8.4 Hz, 1H), 7.46 (ddd, J ¼ 8.2, 6.9, 1.2
Hz, 1H), 7.31 (ddd, J ¼ 8.1, 6.9, 1.1 Hz, 1H), 7.09 (d, J ¼ 8.8 Hz,
1H), 3.84 (dd, J ¼ 9.3, 3.0 Hz, 1H), 3.33 (s, 1H), 2.49–2.19 (m,
2H), 2.11 (ddd, J ¼ 13.0, 10.9, 6.4 Hz, 1H), 1.93 (dddd, J ¼ 8.6,
6.5, 5.4, 3.3 Hz, 1H), 1.81 (dtd, J ¼ 9.6, 6.3, 3.0 Hz, 1H), 1.72–1.58
(m, 1H) ppm. 13C NMR (101 MHz, CDCl3) d ¼ 155.38, 130.48,
2-Bromo-8,9,10,10a-tetrahydro-7aH-cyclopenta[b]naphtha
[1,2-d]furan-7a-ol (8). Colorless oil; 1H NMR (500 MHz, CDCl3) d
¼ 7.75 (s, 1H), 7.65 (dd, J ¼ 8.6, 3.6 Hz, 2H), 7.37 (dd, J ¼ 8.7, 1.8
Hz, 1H), 7.07 (dd, J ¼ 8.7, 3.4 Hz, 1H), 3.81–3.70 (m, 1H), 3.50–
3.40 (brs, 1H), 2.49–2.34 (m, 1H), 2.34–2.20 (m, 1H), 2.19–2.04
(m, 1H), 1.94–1.72 (m, 2H), 1.64 (dq, J ¼ 10.6, 6.3 Hz, 1H) ppm.
13C NMR (101 MHz, CDCl3) d ¼ 156.09, 131.62, 130.61, 129.39,
127.93, 126.38, 124.57, 122.02, 121.22, 120.68, 112.18, 51.13,
40.02, 32.70, 24.80 ppm. HRMS (ESI) calcd for C15H14BrO2 (M +
1)+: 306.1745, found: 306.1742.
6-Bromo-8,9,10,10a-tetrahydro-7aH-cyclopenta[b]naphtha
[1,2-d]furan-7a-ol (9). Colorless oil, 94% yield. 1H NMR (500
MHz, CDCl3) d ¼ 7.90 (s, 1H), 7.71 (t, J ¼ 10.8 Hz, 1H), 7.60 (d, J
¼ 8.3 Hz, 1H), 7.47 (dd, J ¼ 8.1, 7.1 Hz, 1H), 7.33 (dd, J ¼ 8.1, 7.0
Hz, 1H), 3.99–3.88 (m, 1H), 3.51 (d, J ¼ 10.4 Hz, 1H), 2.52–2.35
(m, 2H), 2.19–2.08 (m, 1H), 1.99–1.88 (m, 1H), 1.83 (ddd, J ¼
12.7, 6.4, 3.5 Hz, 1H), 1.76–1.64 (m, 1H) ppm. 13C NMR (101
MHz, CDCl3) d ¼ 152.39, 131.06, 130.53, 129.43, 128.02, 127.00,
123.93, 122.92, 122.61, 122.23, 104.75, 52.34, 40.20, 32.80, 24.94
ppm. HRMS (ESI) calcd for C15H14BrO2 (M + 1)+: 306.1745,
found: 306.1740.
2-(2-Methoxynaphthalen-1-yl)cyclopentanone (10). White
solid; Mp: 92–93 ꢀC; 1H NMR (400 MHz, CDCl3) d ¼ 7.79 (dd, J ¼
8.5, 4.4 Hz, 2H), 7.47 (t, J ¼ 7.3 Hz, 1H), 7.39–7.30 (m, 1H), 7.30–
7.22 (m, 2H), 3.85 (s, 3H), 2.60 (ddd, J ¼ 18.4, 11.9, 8.6 Hz, 1H),
2.45 (ddd, J ¼ 19.3, 12.4, 8.0 Hz, 2H), 2.33–2.10 (m, 2H), 2.09–
1.84 (m, 1H) ppm. 13C NMR (101 MHz, CDCl3) d ¼ 219.87,
129.62, 128.98, 128.76, 126.69, 123.51, 122.48, 114.12, 56.07,
47.79, 38.22, 30.83, 22.08 ppm. HRMS (ESI) calcd for C15H17O2
(M + 1)+: 241.1229, found: 241.1230.
2-(1-Hydroxynaphthalen-4-yl)cyclopentanone (11). Yellow
solid; Mp: 102–103 ꢀC; 1H NMR (400 MHz, CDCl3) d ¼ 8.22–8.08
(m, 1H), 7.78 (dd, J ¼ 8.4, 3.4 Hz, 1H), 7.57–7.34 (m, 2H), 6.96
(dd, J ¼ 9.8, 7.9 Hz, 1H), 6.59 (dd, J ¼ 15.7, 7.8 Hz, 1H), 5.99 (brs,
1H), 4.06–3.88 (m, 1H), 2.71–2.53 (m, 2H), 2.53–2.36 (m, 1H),
2.30–2.10 (m, 2H), 2.10–1.89 (m, 1H) ppm. 13C NMR (101 MHz,
CDCl3) d ¼ 221.02, 151.09, 132.87, 127.01, 126.41, 125.37,
125.12, 124.74, 123.33, 122.64, 108.31, 52.34, 39.10, 32.48, 21.06
ppm. HRMS (ESI) calcd for C16H17O2 (M + 1)+: 241.1229, found:
241.1231.
2-(4-Methoxy naphthalen-2-yl)cyclopentanone (13).4a Color-
less oil, 1H NMR (400 MHz, CDCl3) d ¼ 8.31 (dd, J ¼ 8.3, 1.2 Hz,
1H), 7.81 (d, J ¼ 8.0 Hz, 1H), 7.60–7.38 (m, 2H), 7.14 (d, J ¼ 8.0
Hz, 1H), 6.77 (d, J ¼ 8.0 Hz, 1H), 4.01–3.93 (m, 1H), 3.98 (s, 3H),
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2.68–2.51 (m, 2H), 2.51–2.35 (m, 1H), 2.30–2.12 (m, 2H), 2.04 120.26, 107.63, 79.54, 35.28, 29.42, 17.33 ppm. HRMS (ESI)
(dddd, J ¼ 14.1, 12.2, 7.1, 3.3 Hz, 1H) ppm. 13C NMR (101 MHz, calcd for C14H14NO2 (M + 1)+: 228.1025, found: 228.1027.
CDCl3) d ¼ 219.12, 154.76, 132.88, 127.33, 126.58, 126.16,
2-(8-Hydroxy-2-methylquinolin-5-yl)cyclopentanone
125.12, 125.02, 123.46, 122.78, 103.47, 55.54, 52.03, 38.94, With an excess amount of a-haloketone, three products were
(20).
32.45, 21.08 ppm. HRMS (ESI) calcd for C15H17O2 (M + 1)+: obtained. Product 19 was a white solid, Mp: 114–115 C, 15%
241.1229, found: 241.1234.
ꢀ
1
yield. H NMR (400 MHz, CDCl3) d ¼ 8.08 (d, J ¼ 8.7 Hz, 1H),
2-Ethyl-1-methyl-1,2-dihydronaphtho[2,1-b] furan-2-ol (14). 7.32 (d, J ¼ 8.7 Hz, 1H), 7.15 (d, J ¼ 7.9 Hz, 1H), 7.08 (d, J ¼ 7.9
Freshly distilled 2-chloro-3-pentanone (1.0 mmol) was added Hz, 1H), 3.88 (dd, J ¼ 10.4, 8.7 Hz, 1H), 2.72 (s, 3H), 2.63–2.48
into the solution of 2-naphthol (0.5 mmol), anhydrous Na2CO3 (m, 2H), 2.41 (ddd, J ¼ 19.1, 10.4, 8.6 Hz, 1H), 2.32–2.13 (m, 2H),
(0.6 mmol) and HFIP (1.0 mL). The mixture was stirred at r.t. 2.13–1.95 (m, 1H) ppm. 13C NMR (101 MHz, CDCl3) d ¼ 218.07,
over 2 days, and then ltered through a celite pad using CH2Cl2. 156.53, 150.89, 138.08, 133.04, 125.50, 124.98, 124.87, 122.50,
The ltrate was concentrated under reduced pressure and 109.19, 51.27, 38.51, 31.50, 24.73, 21.04 ppm. HRMS (ESI) calcd
separated by silica gel ash chromatography to give two pure for C15H16NO2 (M + 1)+: 242.1181, found: 242.1177.
products. Product 13 was white solid, Mp: 101–103 ꢀC, 11%
2-((2-Methylquinolin-8-yl)oxy)cyclopentanone (21). White
yield. H NMR (400 MHz, CDCl3) d ¼ 8.38 (d, J ¼ 8.4 Hz, 1H), solid, Mp: 87–89 ꢀC, 43% yield. 1H NMR (400 MHz, CDCl3) d ¼
7.93 (d, J ¼ 8.0 Hz, 1H), 7.66–7.50 (m, 3H), 7.44 (t, J ¼ 7.6 Hz, 8.01 (d, J ¼ 8.4 Hz, 1H), 7.47–7.33 (m, 2H), 7.33–7.28 (m, 1H),
1H), 2.84 (dd, J ¼ 15.2, 7.6 Hz, 2H), 2.57 (s, 3H), 1.33 (t, J ¼ 7.6 7.22 (dd, J ¼ 7.5, 1.2 Hz, 1H), 5.09–4.89 (m, 1H), 2.77 (s, 3H),
Hz, 3H) ppm. 13C NMR (101 MHz, CDCl3) d ¼ 162.04, 157.26, 2.72–2.58 (m, 1H), 2.46–2.36 (m, 1H), 2.28 (dddd, J ¼ 14.1, 10.3,
130.32, 128.43, 127.51, 125.75, 124.22, 124.10, 123.09, 122.21, 6.6, 4.7 Hz, 2H), 2.13–1.79 (m, 2H) ppm. 13C NMR (101 MHz,
121.72, 113.01, 27.90, 25.00, 23.93 ppm. HRMS (ESI) calcd for CDCl3) d ¼ 214.01, 158.31, 153.25, 140.07, 136.16, 127.82,
1
C
17H19O2 (M + 1)+: 211.1123, found: 211.1125.
125.49, 122.51, 121.08, 112.90, 81.11, 35.38, 29.37, 25.60, 17.20
2-(Naphthalen-2-yloxy)pentan-3-one (15). Brown oil, 7% ppm. HRMS (ESI) calcd for C15H16NO2 (M + 1)+: 242.1181,
yield. 1H NMR (500 MHz, CDCl3) d ¼ 7.81–7.72 (m, 2H), 7.69 (d, J found: 242.1180.
¼ 8.2 Hz, 1H), 7.48–7.41 (m, 1H), 7.39–7.30 (m, 1H), 7.17 (dd, J ¼
2-((2-Methyl-5-(2-oxocyclopentyl)quinolin-8-yl)oxy)cyclopen-
8.9, 2.5 Hz, 1H), 6.98 (d, J ¼ 2.4 Hz, 1H), 4.80 (q, J ¼ 6.9 Hz, 1H), tanone (22). White solid, mixture of two diastereomers (dr ¼
2.73 (dq, J ¼ 18.9, 7.2 Hz, 1H), 2.47 (dq, J ¼ 18.9, 7.3 Hz, 1H), 1 : 1), Mp: 76–79 ꢀC, 11% yield. 1H NMR (400 MHz, CDCl3) d ¼
2.20–2.04 (m, 1H), 1.56 (d, J ¼ 7.0 Hz, 3H), 1.01 (t, J ¼ 7.3 Hz, 3H) 8.08 (dd, J ¼ 11.5, 8.8 Hz, 1H), 7.31 (dd, J ¼ 8.7, 3.2 Hz, 1H),
ppm. 13C NMR (101 MHz, CDCl3) d ¼ 213.20, 155.48, 134.33, 7.20–7.08 (m, 2H), 5.07–4.82 (m, 1H), 3.92 (dd, J ¼ 18.8, 8.8 Hz,
129.94, 129.26, 127.63, 126.89, 126.63, 124.10, 118.75, 107.42, 1H), 2.76 (d, J ¼ 2.1 Hz, 3H), 2.67–2.49 (m, 3H), 2.49–2.33 (m,
79.13, 29.89, 18.07, 7.11 ppm. HRMS (ESI) calcd for C15H17O2 (M 3H), 2.33–2.13 (m, 4H), 2.13–1.98 (m, 1H), 1.98–1.80 (m, 1H)
+ 1)+: 229.1229, found: 229.1224.
ppm. 13C NMR (101 MHz, CDCl3) d ¼ 218.07, 217.80, 214.13,
2-(7-Hydroxyisoquinolin-8-yl)cyclopentanone (16). Yellow 213.94, 157.91, 157.86, 152.57, 152.51, 140.74, 140.52, 132.69,
solid; Mp: 92–93 ꢀC, 1H NMR (400 MHz, CDCl3) d ¼ 9.28 (s, 1H), 132.52, 128.47, 128.26, 126.70, 126.58, 124.15, 123.85, 122.30,
8.50 (d, J ¼ 5.8 Hz, 1H), 8.14 (d, J ¼ 5.8 Hz, 1H), 7.16 (dd, J ¼ 122.21, 113.27, 112.37, 81.38, 81.16, 51.47, 51.07, 38.71, 38.61,
17.2, 8.2 Hz, 1H), 7.07–6.96 (m, 1H), 4.14–4.02 (m, 1H), 2.71– 35.44, 35.39, 31.80, 31.69, 29.40, 25.40, 21.04, 21.02, 17.22 ppm.
2.52 (m, 2H), 2.52–2.34 (m, 1H), 2.22 (tt, J ¼ 17.4, 6.0 Hz, 2H), HRMS (ESI) calcd for C20H22NO3 (M + 1)+: 324.1600, found:
2.12–2.03 (m, 1H) ppm. 13C NMR (101 MHz, CDCl3) d ¼ 218.72, 324.1603.
152.19, 147.69, 140.26, 129.17, 128.13, 127.12, 126.39, 116.83,
2-Phenoxycyclopentanone (23).11a White solid; Mp: 69–71 ꢀC;
112.65, 51.10, 38.65, 32.18, 20.98 ppm. HRMS (ESI) calcd for 1H NMR (300 MHz, CDCl3) d ¼ 7.28 (t, J ¼ 8.1 Hz, 2H), 6.96–7.00
C
14H14NO2 (M + 1)+: 228.1025, found: 228.1022.
(m, 3H), 4.58–4.63 (m, 1H), 2.46–2.55 (m, 1H), 2.33–2.41 (m,
2-(5-Hydroxyisoquinolin-8-yl)cyclopentanone (18). White 2H), 2.11–2.19 (m, 1H), 1.89–2.04 (m, 2H).
1
solid, Mp: 103–104 ꢀC, 36% yield. 1H NMR (400 MHz, CDCl3) d ¼
2-(2-Methoxyphenoxy)cyclopentanone (24). Colorless oil; H
8.92 (s, 1H), 8.15 (d, J ¼ 5.6 Hz, 1H), 7.54 (d, J ¼ 8.8 Hz, 1H), 7.45 NMR (400 MHz, CDCl3) d ¼ 7.08–6.94 (m, 2H), 6.94–6.82 (m,
(d, J ¼ 5.6 Hz, 1H), 7.21 (d, J ¼ 5.6 Hz, 1H), 3.87 (t, J ¼ 6.8 Hz, 2H), 4.60 (dd, J ¼ 9.2, 8.0 Hz, 1H), 3.85 (s, 3H), 2.51–2.40 (m,
1H), 2.43–2.34 (m, 2H), 2.23–2.18 (m, 1H), 1.84–1.81 (m, 2H), 1H), 2.35 (dt, J ¼ 9.5, 6.8 Hz, 2H), 2.21–2.08 (m, 1H), 2.10–1.98
1.71–1.52 (m, 1H) ppm. 13C NMR (101 MHz, CDCl3) d ¼ 205.73, (m, 1H), 1.95–1.76 (m, 1H) ppm. 13C NMR (101 MHz, CDCl3) d ¼
157.01, 146.54, 138.91, 131.63, 130.83, 130.24, 127.65, 121.76, 213.77, 150.31, 147.32, 122.81, 120.82, 117.09, 112.34, 81.00,
108.57, 50.42, 39.91, 33.32, 24.56 ppm. HRMS (ESI) calcd for 55.95, 35.24, 29.53, 17.20 ppm. HRMS (ESI) calcd for C12H15O3
C
14H14NO2 (M + 1)+: 228.1025, found: 228.1026.
(M + 1)+: 207.1021, found: 207.1024.
2-(Isoquinolin-5-yloxy)cyclopentanone (19). Colorless oil,
2-((3-Methoxyphenyl) amino)cyclopentanone (25). White
15% yield. 1H NMR (400 MHz, CDCl3) d ¼ 9.14 (s, 1H), 8.42 (d, J solid; Mp: 121–122 ꢀC; 1H NMR (400 MHz, CDCl3) d ¼ 7.10 (t, J ¼
¼ 5.7 Hz, 1H), 7.75 (d, J ¼ 9.0 Hz, 1H), 7.59 (d, J ¼ 5.7 Hz, 1H), 8.1 Hz, 1H), 6.37–6.27 (m, 2H), 6.22 (t, J ¼ 2.3 Hz, 1H), 4.42 (s,
7.42 (dd, J ¼ 8.9, 2.5 Hz, 1H), 7.34 (d, J ¼ 2.4 Hz, 1H), 4.79 (t, J ¼ 1H), 3.77 (s, 3H), 3.69 (dd, J ¼ 11.4, 7.9 Hz, 1H), 2.76 (ddd, J ¼
8.4 Hz, 1H), 2.70–2.57 (m, 1H), 2.51–2.31 (m, 2H), 2.31–2.17 (m, 12.5, 7.6, 6.3 Hz, 1H), 2.56–2.41 (m, 1H), 2.21 (dd, J ¼ 19.5, 9.4
1H), 2.13–1.88 (m, 2H) ppm. 13C NMR (101 MHz, CDCl3) d ¼ Hz, 1H), 2.17–2.07 (m, 1H), 1.99–1.84 (m, 1H), 1.58 (qd, J ¼ 12.3,
213.42, 156.68, 151.17, 141.44, 131.80, 129.63, 128.24, 123.89, 6.8 Hz, 1H) ppm. 13C NMR (101 MHz, CDCl3) d ¼ 215.63, 160.86,
148.85, 130.09, 106.57, 103.21, 99.66, 61.96, 55.15, 34.68, 31.83,
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17.79 ppm. HRMS (ESI) calcd for C12H16NO2 (M + 1)+: 206.1181,
found: 206.1180.
K. M. Reddy, A. Barik, B. K. D. Reddy, P. Reddanna,
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2-(2,4,6-Trimethoxyphenyl)cyclopentanone (26). Freshly
distilled a-chlorocyclopentanone (0.5 mmol) was added into the
solution of 1,3,5-trimethoxybenzene (0.5 mmol), anhydrous
Na2CO3 (0.6 mmol) and TFE (1.0 mL). Aer stirring at r.t. for 8 h,
a white solid was obtained merely by ltration through a celite
pad using dichloromethane and evaporation under reduced
¨
R. Frohlich and A. Patra, Tetrahedron, 2004, 60, 10197–10205.
1
pressure. Mp: 117–118 ꢀC, H NMR (400 MHz, CDCl3) d ¼ 6.12
6 (a) E. Motti, N. Della Ca, D. Xu, S. Armani, B. M. Aresta and
M. Catellani, Tetrahedron, 2013, 69, 4421–4428; (b) V. Bhat,
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Kimpe, Tetrahedron, 2009, 65, 1716–1723; (d) X. Guo, R. Yu,
H. Li and Z. Li, J. Am. Chem. Soc., 2009, 131, 17387–17393;
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(s, 2H), 3.79 (s, 3H), 3.74 (s, 6H), 3.68 (dd, J ¼ 11.0, 8.7 Hz, 1H),
2.37 (dd, J ¼ 9.6, 5.5 Hz, 2H), 2.28–2.17 (m, 1H), 2.09 (ddt, J ¼
16.8, 11.7, 4.2 Hz, 2H), 1.93–1.75 (m, 1H) ppm. 13C NMR (101
MHz, CDCl3) d ¼ 220.63, 160.28, 158.55, 109.34, 91.18, 55.61,
55.35, 45.06, 38.05, 29.92, 21.82 ppm. HRMS (ESI) calcd for
C
14H19O4 (M + 1)+: 251.1283, found: 251.1280.
2-(3-Acetyl-2,4,6-trimethoxyphenyl)cyclopentanone
(27).
White solid, Mp: 86–87 ꢀC, 48% yield. 1H NMR (500 MHz,
CDCl3) d ¼ 6.25 (s, 1H), 3.82 (s, 3H), 3.78 (s, 3H), 3.67 (s, 3H),
3.57 (dd, J ¼ 10.6, 9.0 Hz, 1H), 2.50 (s, 3H), 2.38 (dd, J ¼ 9.8, 4.5
Hz, 2H), 2.31–2.20 (m, 1H), 2.20–2.08 (m, 2H), 1.95–1.81 (m, 1H)
ppm. 13C NMR (126 MHz, CDCl3) d ¼ 219.98, 201.97, 159.24,
157.22, 157.11, 114.77, 91.82, 55.90, 55.63, 45.66, 37.96, 32.51,
30.25, 21.72 ppm. HRMS (ESI) calcd for C16H21O5 (M + 1)+:
293.1389, found: 293.1390.
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Acknowledgements
The project was sponsored by the Scientic Research Founda-
tion for the Returned Overseas Chinese Scholars, State Educa-
tion Ministry, and the Scientic and Technological Research
Program of Chongqing Municipal Education Commission.
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