Base-Mediated Cyclization Reaction of 2-(5-Hydroxy-1-pentynyl)benzonitriles to 4-Amino-2,3-dihydronaphtho[2,3-b]furanes and Synthesis of Furanonaphthoquinones

Article abstract of DOI:10.1021/acs.joc.5b02514

An efficient transformation of 2-(5-hydroxy-1-pentynyl)benzonitriles 5 to furanonaphthoquinones 11 is presented. Treatment of 5 with 1.5 equiv of NaOMe in DMSO at 140 °C for 0.5 h gave 6 in good yields. Conversion of 6 to 11 was carried out by oxidation of 6 with Fremy's salt and KH₂PO₄ in acetone and water, followed by dehydrogenation using palladium on charcoal in diphenylether at reflux temperature.

Full text of DOI:10.1021/acs.joc.5b02514

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Note
Base-Mediated Cyclization Reaction of 2-(5-Hydroxy-1-
pentynyl)benzonitriles to 4-Amino-2,3-dihydronaphtho[2,3-
b]furanes and Synthesis of Furanonaphthoquinones
Chih-Jyun Tsai, Chin-Chau Chen, Chih-Wei Tsai, and Ming-Jung Wu
J. Org. Chem., Just Accepted Manuscript • DOI: 10.1021/acs.joc.5b02514 • Publication Date (Web): 05 Apr 2016
Downloaded from http://pubs.acs.org on April 6, 2016
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Base-Mediated Cyclization Reaction of
2-(5-Hydroxy-1-pentynyl)benzonitriles to
4-Amino-2,3-dihydronaphtho[2,3-b]furanes and
Synthesis of Furanonaphthoquinones
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Chih-Jyun Tsai,a Chin-Chau Chen,a Chih-Wei Tsaib and Ming-Jung Wua,b,*
aDepartment of Chemistry, National Sun Yat-sen University, Kaohsiung, Taiwan
bDepartment of Medicinal and Applied Chemistry, Kaohsiung Medical University,
Taiwan
E-mail: mijuwu@faculty.nsysu.edu.tw
Abstract
An efficient transformation of 2-(5-Hydroxy-1-pentynyl)benzonitriles 5 to
furanonaphthoquinones 11 is presented. Treatment of 5 with one and half
equivalents of NaOMe in DMSO at 140 oC for 0.5 h gave 6 in good yields. Conversion
of 6 to 11 was carried out by oxidation of 6 with Fremy's salt and KH2PO4 in acetone
and water and followed by dehydrogenation using palladium on charcoal in diphenyl
ether at reflux temperature.
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Many nature occurring or synthetic furanonaphthoquinones have been found to
exhibit broad spectrum of biological activities, especially the antitumor activity.1 For
instance, kigelinone (1) was isolated from the wood of Kigelia pinnata by Inoue and
showed good antitumor activity.1a Compounds 2 and 3 were isolated from Crescentia
cujete by Kingston and exhibited high cytotoxicity against Vero cells.1c The synthetic
compound FNQ3 (4) reported by Takegami was found good antiviral activity against
Japanese encephalitis virus (JEV).1d (Scheme 1) Because of the importance of
furanonaphthoquinones to the drug development, several synthetic methods have
been developed to construct this ring system.2 But most of them suffer from either
long synthetic sequence or limitation of using 2-hydroxy-1,4-naphthoquinone as the
starting material. We herein wish to report an efficient synthesis of
furanonaphthoquinones by the cyclization of 2-(5-hydroxy-1-pentynyl)benzonitriles 5
to 4-amino-2,3-dihydronaphtho[2,3-b]furanes 6 followed by oxidation and
dehydrogenation reactions.
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The starting 2-(5-hydroxy-1-pentynyl)benzonitrile (5a) was prepared by the
Sonogashira coupling reaction of 2-bromobenzonitrile and 4-petyn-1-ol using
palladium as the catalyst.3 During our investigation of the reaction of internal alkynes
with sodium azide to triazoles,4 we found that reaction of 5a with one and half
equivalents of NaN3 gave compound 6a albeit in low yield. (Scheme 2) Apparently
sodium azide reacts as a base in this reaction followed by nucleophilic addition and
subsequent cyclization reactions to give compound 6a. We then anticipated that if a
more suitable base was employed into this reaction, compound 6a should be
obtained in higher yield. Compound 6a could further be oxidized to
furanonaphthoquinones.
Six different bases were screened for this study and the results were summarized in
Table 1. It was found that reaction of 5a with one and half equivalents of NaOMe in
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DMSO at 140 oC for 0.5 h gave compound 6a in 66% yield. Bases, such as NaOH,
K2CO3 and Na2CO3, were found to be not as efficient as NaOMe for the formation of
6a. Using the stronger bases, such as KOtBu and NaH, compound 9a was obtained as
the major products. Apparently compound 9a came from the further elimination
reaction of product 6a. Various solvents have also been tested. The polar aprotic
solvents, such as DMF and NMP, also provided compound 6a but in lower yields and
the major products is 7a. When the reaction was carried out in CH3CN, 1,4-dioxane
or toluene, only 7a and 8a were obtained, no 6a was formed. To summarize the
screening study, the optimized reaction conditions for compound 6a is the treatment
of 5a with one and half equivalents of NaOMe in DMSO at 140 oC for 0.5 h.
Table 1. Screening the base, temperature and solvent effects on
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the cyclization reactions of 5a.
Entry Base
Solvent Temp. (oC) Products/Yields
1
NaOH
DMSO
140
6a/49;7a/40; 8a/8
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K2CO3
DMSO
140
140
140
140
140
140
140
140
7a/63; 8a/10
7a/44; 8a/9
Na2CO3 DMSO
NaH
DMSO
DMSO
DMSO
DMF
6a/16; 9a/43
6a/8; 9a/38
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KOtBu
NaOMe
NaOMe
NaOMe
NaOMe
6a/66
6a/18; 7a/63; 8a/12
6a/24; 7a/61; 8a/11
7a/64; 8a/11
7a/36; 8a/51
7a/55; 8a/24
6a/43;7a/22; 8a/5
6a/26;7a/53; 8a/8
NMP
CH3CN
10 NaOMe 1,4-dioxane 140
11 NaOMe
toluene
140
120
100
12 NaOMe DMSO
13 NaOMe DMSO
With the optimized reaction conditions in hand, other substrates5 5b-l were carried
out for the cyclization reaction to give various
4-amino-2,3-dihydronaphtho[2,3-b]furanes 6b-l in modest to good chemical yields.
The results are summarized in scheme 3. Compounds 5b-e bearing primary hydroxyl
group gave the cyclization products 6b-e in 70-77% yields. Compounds 5f-h bearing
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secondary hydroxyl group and R2 is an alkyl group also produced the cyclization
products 6f-i in good chemical yields. However, when R2 is a vinyl or an aryl group,
such as 5j-m, the cyclization products 6j-m was obtained in lower yields.
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On the other hand, treatment of 5n under the optimized reaction conditions gave a
complex product mixture. Although we did not isolate any identified product, the
acetal cleavage must take place under this reaction conditions. Therefore we carried
out the cyclization reaction of 5n in DMSO at 140 oC using the less nucleophilic base,
NaH, and the reaction time was reduced to 15 min, product 6n was obtained in 58%
yield. (Scheme 4)
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The proposed mechanism for the cyclization of 5a to 6a is shown in scheme 5. The
first step is the deprotonation of 5a with base to form alkoxide I that would undergo
intramolecular 5-exo-dig cyclization to form the vinyl anions 7a' and 8a'. The vinyl
anions 7a' or 8a' could undergo direct proton transformation and equilibration to
give anion II or protonation to give the intermediates 7a and 8a. Under the described
reaction conditions, compounds 7a and 8a undergo equilibrium to each other.
Further deprotonation of 8a would also give anion II that could directly attack the
cyano group to give the iminium ion IV6 or undergoes tautomerization to form
ketenimine anion III, then the electrocyclic ring closure reaction to give IV.7 Finally
protonation of IV to give imine V and following the imine-enamine tautomerization,
to convert the imine V to the final product 6a.
To understand more insight of the reaction mechanism, we carried out the
experiments by recharging either compound 7a or 8a into the optimized reaction
conditions, both of them were converted to 6a slowly. After stirring for 24 hours,
only 52% of 6a was obtained and isolated both the staring material and its isomer.
Comparing to the one-pot reaction, conversion of 5a to 6a under the optimized
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reaction conditions requires only 0.5 hour. We therefore conclude that the
intramolecular proton transfer from 7a' or 8a' to anion II must be faster than the
formation of 7a and 8a and these two isomers can undergo equilibrium to each other
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under this reaction conditions.
Scheme 5. Proposed mechanism for the formation of 6a
-O
OH
base
O
O
CN
CN
CN
H+
H
5a
CN
7a'
8a'
8a
H+
H
I
H
O
NaOCH3
CH3OH
7a' 8a'
or
O
proton transfer
and equilibration
CN
CN
H
7a
O
O
base
8a
C
N
C
N-
II
III
O
O
O
H+
N-
NH2
IV
V
6a
NH
For the conversion of 4-amino-2,3-dihydronaphtho[2,3-b]furanes 6 to
furanonaphthoquinones 11 are summarized in Table 2. Oxidation of compounds 6a-k,
6n were carried out by using Fremy's salt8 and KH2PO4 in acetone and water to give
dihydrofuranonaphthoquinones 10a-k and 10n in good yields except compound 6b.
The low yield for the conversion of 6b to 10b could be due to the steric hindrance of
the methyl group at 8-position to prevent the oxidation take place at the 9-position.
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Finally, all of the dihydrofuranonaphthoquinones 10a-k and 10n were
5
6
7
8
9
dehydrogenated using palladium on charcoal in diphenyl ether at reflux temperature9
to give furanonaphthoquinones 11a-e, 4, 11g-i, 11k and 11n in 48-86% yields. Only
compound 10j gave a complex mixture of products under this reaction conditions.
Table 2. Oxidation and dehydrogenation of 6 to Furanonaphthoquinones 11.
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O
Fremy's salt (3 equiv)
O
KH2PO4 ( 3 equiv)
O
R2
R1
R1
R2
acetone/H2O (1/2)
2 h
O
O
NH2
O
6
10
Pd/C
O
R1
R2
diphenyl ether
reflux, 8 h
11
Compounds
Products/Yields (%)
6a
6b
6c
6d
6e
6f
10a/88
10b/46
10c/92
10d/92
10e/88
10f/92
10g/81
10h/77
10i/88
10j/93
10k/84
10n/75
11a/75
11b/62
11c/77
11d/72
11e/68
4/65(80)a
6g
6h
6i
11g/48
11h/38b
11i/86
6j
11j/decomposed
11k/63
6k
6n
11n/52
athe value in parentheses is carried out in 1.85 mmole scale.
b26% of 11k was also obtained.
In conclusion, we have developed an efficient synthesis of
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4-amino-2,3-dihydronaphtho[2,3-b]furanes through the base-mediated cyclization of
2-(5-hydroxy-1-pentynyl)benzonitriles. The base, such as NaOMe, used in this
transformation is ready available, easy to handle and not expensive. The
4-amino-2,3-dihydronaphtho[2,3-b]furanes have been demonstrated to be easily
converted to furanonaphthoquinones by oxidation and dehydrogenation,
respectively.
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Experimental Section
The general procedure for the preparation of compound 5a (5a-e, 5n): To
the solution of 2-bromobenzonitrile (10.0 g, 55.0 mmol) in THF (50 mL) was added
Pd(PPh3)4 (0.50 g, 0.43 mmol), alkyne (66.0 mmol), CuI (0.521 g, 2.74 mmol) and Et3N
(6.65g, 65.93 mmol), respectively. The reaction mixture was well stirred at room
temperature for 8 hours. The reaction mixture was quenched with saturated
aqueous solutions of NH4Cl and extracted with EtOAc. The combined organic extracts
were dried over anhydrous MgSO4(S). After filtration and removal of solvent, the
residue was purified by column chromatography to give compound 5a-e, 5n.
2-(5-Hydroxypent-1-ynyl)benzonitrile (5a)
Yield 9.04 g, 89%. A yellow oil: Rf = 0.48 (2:1 Hex/EtOAc); 1H NMR (500 MHz,
CDCl3) δ 1.89 (quin, J = 6.5 Hz, 2H), 1.94 (brs, 1H), 2.62 (t, J = 6.5 Hz, 2H), 3.86 (t,
J = 6.0 Hz, 2H), 7.34 (td, J = 8.0, 2.0 Hz, 1H), 7.41ꢀ7.52 (m, 2H), 7.60 (dd, J = 8.0,
0.5 Hz, 1H); 13C NMR (125 MHz, CDCl3) δ 16.0, 30.8, 61.1, 77.6, 97.0, 115.2, 117.9,
127.7, 127.9, 132.1, 132.3, 132.4; MS (70 eV) m/z (%): 185 (6) [M+], 85 (85), 71
(100); HRMS (EIꢀmagnetic sector) Calcd for C12H11ON, 185.0841; Found, 185.0839.
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2-(5-Hydroxypent-1-ynyl)-3-methylbenzonitrile (5b)
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7
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9
Yield 2.38 g, 47%. A yellow oil: Rf = 0.43 (2:1 Hex/EtOAc); H NMR (500 MHz,
CDCl3) δ 1.93ꢀ1.91 (m, 3H), 2.44 (s, 3H), 2.67 (t, J = 7.0 Hz, 2H), 3.88 (t, J = 6.0 Hz,
2H), 7.23 (t, J = 7.5 Hz, 1H), 7.40 (d, J = 7.5 Hz, 1H), 7.45 (d, J = 7.5 Hz, 1H); 13C
NMR (125 MHz, CDCl3) δ 16.1, 20.8, 31.0, 61.2, 76.7, 100.9, 115.4, 118.3, 127.4,
127.4, 129.8, 138.4, 141.2; MS (70 eV) m/z (%): 199 (82) [M+], 181 (88), 180 (100);
HRMS (EIꢀmagnetic sector) Calcd for C13H13ON, 199.0997; Found, 199.0999.
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2-(5-Hydroxypent-1-ynyl)-4-methylbenzonitrile (5c)
1
Yield 4.51 g, 89%. A yellow oil: Rf = 0.44 (4:1 Hex/EtOAc); H NMR (500 MHz,
CDCl3) δ 1.91ꢀ1.87 (m, 3H), 2.37 (s, 3H), 2.62 (t, J = 7.0 Hz, 2H), 3.87 (brs, 2H),
7.15 (d, J = 5.0 Hz, 1H), 7.30 (s, 1H), 7.48 (d, J = 7.5 Hz, 1H); 13C NMR (125 MHz,
CDCl3) δ 16.0, 21.6, 30.9, 61.2, 77.8, 96.3, 112.3, 118.2, 127.7, 128.7, 132.3, 132.7,
143.3; MS (70 eV) m/z (%): 199 (70) [M+], 181 (93.63), 180 (100); HRMS
(EIꢀmagnetic sector) Calcd for C13H13ON, 199.0997; Found, 199.0998.
2-(5-Hydroxypent-1-ynyl)-5-methylbenzonitrile (5d)
1
Yield 4.56 g, 90%. A yellow oil: Rf = 0.47 (2:1 Hex/EtOAc); H NMR (500 MHz,
CDCl3) δ 1.91ꢀ1.82 (m, 3H), 2.35 (s, 3H), 2.60 (t, J = 7.0 Hz, 2H), 3.87 (t, J = 6.0 Hz,
2H), 7.29 (dd, J = 8.0, 1.0 Hz, 1H), 7.37 (d, J = 8.0 Hz, 1H), 7.40 (s, 1H); C NMR
13
(125 MHz, CDCl3) δ 16.0, 21.0, 30.9, 61.2, 77.6, 95.9, 115.1, 118.0, 125.0, 132.0,
132.7, 133.3, 138.2; MS (70 eV) m/z (%): 199 (58) [M+], 181 (94), 180 (100); HRMS
(EIꢀmagnetic sector) Calcd for C13H13ON, 199.0997; Found, 199.0997.
2-(5-Hydroxypent-1-ynyl)-5-methoxybenzonitrile (5e)
1
Yield 4.61g, 91%. A yellow oil: Rf = 0.40 (2:1 Hex/EtOAc); H NMR (500 MHz,
CDCl3) δ 1.87 (quin, J = 6.5 Hz, 2H), 2.00 (brs, 1H), 2.58 (t, J = 7.0 Hz, 2H), 3.81 (s,
3H), 3.85 (t, J = 4.8 Hz, 2H),7.02 (dd, J = 9.0, 3.0Hz, 1H), 7.07 (d, J = 2.5 Hz, 1H),
7.37 (d, J = 8.5 Hz, 1H); 13C NMR (125 MHz, CDCl3) δ 16.0, 31.0, 55.6, 61.2, 94.8,
116.1, 116.9, 117.7, 119.1, 120.1, 133.4, 158.6; MS (70 eV) m/z (%): 215 (90) [M+],
197 (100), 182 (66); HRMS (EIꢀmagnetic sector) Calcd for C13H13O2N, 215.0946;
Found, 215.0949.
The general procedure for the preparation of compound 5f (5f-m): The
solution of compound 12 (183 mg, 1.0 mmol) in THF (10 mL) under nitrogen was
cooled to 0oC. The Grignard reagent (1.2 mL, 1M) was then added dropwise to the
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solution for 0.5 hour. The reaction mixture was warmed to room temperature
subsequently quenched with saturated NH4Cl(aq) and extracted with CH2Cl2. The
combined organic extracts were dried over anhydrous MgSO4(S). After filtration and
removal of solvent, the residue was purified by column chromatography to give
compound 5f-m.
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2-(5-Oxohex-1-ynyl)benzonitrile (5f)
Yield 179.13 mg, 90%. A yellow oil: Rf = 0.52 (2:1 Hex/EtOAc); 1H NMR (500 MHz,
CDCl3) δ 1.22 (d, J = 6.5 Hz, 3H), 1.74 (q, J =7.0 Hz, 2H), 2.41 (brs, 1H), 2.52ꢀ2.64
(m, 2H), 4.01ꢀ4.07 (m, 1H), 7.31 (td, J = 8.0, 1.0 Hz, 1H), 7.43ꢀ7.48 (m,2H) 7.56 (d, J
= 7.5 Hz, 1H); 13C NMR (125 MHz, CDCl3) δ 16.0, 23.3, 37.1, 66.4, 77.3, 97.3, 115.0,
117.7, 127.6, 127.8, 132.0, 132.2, 132.3; MS (70 eV) m/z (%): 199 (45) [M+], 180
(100), 154 (55); HRMS (EIꢀmagnetic sector) Calcd for C13H13ON, 199.0997; Found,
199.0997.
2-(5-Oxoundec-1-ynyl)benzonitrile (5g)
Yield 231.34 mg, 86%. A yellow oil: Rf= 0.60 (2:1 Hex/EtOAc); 1H NMR (500 MHz,
CDCl3) δ 0.86 (t, J = 7.0 Hz, 3H), 1.24ꢀ1.51 (m, 10H), 1.67ꢀ1.84 (m, 2H), 1.95 (brs,
1H), 2.57ꢀ2.68 (m, 2H), 3.83ꢀ3.88 (m, 1H), 7.33 (td, J = 7.5, 1.5 Hz, 1H), 7.45ꢀ7.50
(m, 2H), 7.58 (d, J = 7.5 Hz, 1H); 13C NMR (125 MHz, CDCl3) δ 14.0, 16.0, 22.5,
25.5, 29.3, 31.7, 35.5, 37.4, 70.4, 77.4, 97.5, 115.3, 117.8, 127.6, 127.9, 132.1, 132.2,
132.3; MS (70 eV) m/z (%): 269 (29) [M+], 184 (100), 153 (73); HRMS (EIꢀmagnetic
sector) Calcd for C18H23ON, 269.1780; Found, 269.1781.
2-(5-Cyclohexyl-5-oxopent-1-ynyl)benzonitrile (5h)
Yield 240.3 mg, 90%. A yellow solid: Rf = 0.60 (2:1 Hex/EtOAc); 1H NMR (500 MHz,
CDCl3) δ 0.99ꢀ1.27 (m, 5H), 1.31ꢀ1.38 (m, 1H), 1.63ꢀ1.86 (m, 7H), 1.93 (brs, 1H),
2.63 (t, J = 7.0 Hz, 2H), 3.59ꢀ3.63 (m, 1H), 7.33 (td, J = 7.5, 1.5 Hz, 1H), 7.45ꢀ7.50
(m, 2H), 7.59 (d, J = 7.5 Hz, 1H); 13C NMR (125 MHz, CDCl3) δ 16.3, 26.1, 26.2,
26.4, 27.8, 29.0, 32.4, 43.7, 77.3, 77.4, 97.6, 115.2, 117.8, 127.6, 127.9, 132.1, 132.2,
132.3; MS (70 eV) m/z (%): 267 (21) [M+], 184 (100), 140 (58); HRMS (EIꢀmagnetic
sector) Calcd for C18H21ON, 267.1623; Found, 267.1626.
2-(6,6-Dimethyl-5-oxohept-1-ynyl)benzonitrile (5i)
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Yield 183.27 mg, 76%. A colorless oil: Rf = 0.63 (2:1 Hex/EtOAc); 1H NMR (500
MHz, CDCl3) δ 0.94 (s, 9H), 1.56ꢀ1.64 (m, 1H), 1.79 (brs, 1H), 1.83ꢀ1.90 (m, 1H),
2.67 (t, J = 6.5 Hz, 2H), 3.52 (d, J = 10.5 Hz, 1H), 7.34 (td, J = 7.0, 2.0 Hz, 1H),
7.47ꢀ7.52 (m, 2H), 7.61 (d, J = 8.0 Hz, 1H); 13C NMR (125 MHz, CDCl3) δ 17.0, 25.6,
29.9, 34.9, 77.6, 78.2, 97.7, 115.3, 117.9, 127.6, 128.0, 132.1, 132.3, 132.4; MS (70
eV) m/z (%): 241 (10) [M+], 184 (100), 142 (43); HRMS (EIꢀmagnetic sector) Calcd
for C16H19ON, 241.1467; Found, 241.1466.
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2-(5-Oxohept-6-en-1-ynyl)benzonitrile (5j)
Yield 122.38 mg, 58%. A brown oil: Rf = 0.62 (2:1 Hex/EtOAc); 1H NMR (500 MHz,
CDCl3) δ 1.85 (q, J = 7.0 Hz, 2H), 2.35 (brs, 1H), 2.52ꢀ2.67 (m, 2H), 4.40 (q, J = 6.5
Hz, 1H), 5.14 (d, J = 10.5 Hz, 1H), 5.32 (d, J = 17.0 Hz, 1H), 5.85ꢀ5.92 (m, 1H), 7.33
(td, J = 7.5, 1.5 Hz, 1H), 7.45ꢀ7.50 (m, 2H), 7.58 (d, J = 7.5 Hz, 1H); 13C NMR (125
MHz, CDCl3) δ 15.7, 35.1, 71.4, 77.5, 97.0, 115.1, 115.1, 117.7, 127.6, 127.8, 132.1,
132.3, 132.3, 140.3; MS (70 eV) m/z (%): 211 (8) [M+], 154 (100), 140 (73); HRMS
(EIꢀmagnetic sector) Calcd for C14H13ON, 211.0997; Found, 211.0994.
2-(5-Oxo-5-phenylpent-1-ynyl)benzonitrile (5k)
Yield 229.68 mg, 88%. A yellow oil: Rf = 0.58 (2:1 Hex/EtOAc); 1H NMR (500 MHz,
CDCl3) δ 1.97ꢀ2.13 (m, 2H), 2.48ꢀ2.72 (m, 3H), 5.01 (t, J = 5.0 Hz, 1H), 7.27 (t, J =
7.5 Hz, 1H), 7.33ꢀ7.37 (m, 3H), 7.43ꢀ7.41 (m, 2H), 7.48ꢀ7.52 (m, 2H), 7.60 (d, J = 8.0
Hz, 1H); 13C NMR (125 MHz, CDCl3) δ 16.2, 37.2, 72.6, 77.7, 97.0, 115.2, 117.8,
125.8, 125.8, 127.5, 127.6, 127.8, 128.4, 128.4, 132.1, 132.3, 132.4, 144.1; MS (70
eV) m/z (%): 261 (33) [M+], 107 (100), 79 (90); HRMS (EIꢀmagnetic sector) Calcd
for C18H15ON, 261.1154; Found, 261.1152.
2-(5-Hydroxy-5-(naphthalen-1-yl)pent-1-yn-1-yl)benzonitrile (5l)
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Yield 202.0 mg, 65%. A yellow oil: Rf= 0.25 (4:1 Hex/EtOAc); H NMR (500 MHz,
CDCl3) δ 8.22 (d, J = 8.0 Hz, 1H), 7.87 (d, J = 8.0 Hz, 1H), 7.78 (d, J = 8.0 Hz, 1H),
7.72 (d, J = 8.0 Hz, 1H), 7.63 (d, J = 8.0 Hz, 1H), 7.53ꢀ7.47 (m, 3H), 7.49 (d, J = 8.0
Hz, 1H), 7.48 (d, J = 8.0 Hz, 1H), 7.39ꢀ7.35 (m, 1H), 5.80 (dd, J = 9.0, 4.0 Hz, 1H),
2.90ꢀ2.80 (m, 1H), 2.68ꢀ2.62 (m, 1H), 2.46 (brs, 1H), 2.32ꢀ2.26 (m, 1H), 2.21ꢀ2.14 (m,
1H); 13C NMR (125 MHz, CDCl3) δ 139.8, 133.8, 132.4, 132.3, 132.2, 130.2, 128.8,
128.0, 127.8, 127.7, 126.1, 125.5, 125.4, 123.2, 122.9, 117.9, 115.2, 97.1, 77.9, 69.7,
36.4, 16.5; MS (ESI) m/z (%): 334 (100) [M+Na]+; HRMS (ESIꢀTOF) Calcd for
C22H17NONa [M+Na]+, 334.1208; Found, 334.1206.
2-(5-Hydroxy-5-(4-methoxyphenyl)pent-1-yn-1-yl)benzonitrile (5m)
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Yield 221.0 mg, 76%. Ayellowoil: Rf= 0.15 (4:1 Hex/EtOAc); H NMR (500 MHz,
CDCl3) δ 7.62 (d, J = 8.0 Hz, 1H), 7.51 (d, J = 8.0 Hz, 1H), 7.50 (t, J = 8.0 Hz, 1H),
7.36 (t, J = 8.0 Hz, 1H), 7.35 (d, J = 8.0, 2H), 6.89 (d, J = 8.0 Hz, 2H), 4.97 (dd, J =
8.0, 5.5 Hz, 1H), 3.80 (s, 3H), 2.70ꢀ2.64 (m, 1H), 2.54ꢀ2.47 (m, 1H), 2.20 (brs, 1H),
2.14ꢀ2.07 (m, 1H), 2.04ꢀ1.95 (m, 1H); 13C NMR (125 MHz, CDCl3) δ 159.1, 136.2,
132.4, 132.3, 132.2, 127.9, 127.7, 117.9, 115.3, 113.9, 97.0, 77.8, 72.4, 55.2, 37.2,
16.3; MS (ESI) m/z (%): 314 [M+Na]+; HRMS (ESIꢀTOF) Calcd for C19H17NO2Na
[M+Na]+, 314.1157; Found, 314.1156.
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6-(5-Hydroxypent-1-yn-1-yl)benzo[d][1,3]dioxole-5-carbonitrile (5n)
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Yield 4.30 g, 85%. A yellow solid: Rf= 0.41 (2:1 Hex/EtOAc); H NMR (500 MHz,
CDCl3) δ 1.77 (brs, 1H), 1.87 (quin, J = 6.5 Hz, 2H), 2.59 (t, J = 7.0 Hz, 2H), 3.84 (t,
J = 6.0 Hz, 2H), 6.06 (s, 2H), 6.87 (s, 1H), 6.96 (s, 1H); 13C NMR (125 MHz, CDCl3)
δ 15.9, 30.8, 61.1, 77.5, 95.4, 102.5, 108.5, 111.2, 111.8, 118.0, 123.7, 147.3, 151.1;
MS (70 eV) m/z (%): 229 (8) [M+], 88 (100), 73 (63), 70 (96), 61 (98); HRMS
(EIꢀmagnetic sector) Calcd for C13H11O3N, 229.0739; Found, 229.0739.
General Procedure for the preparation of
4-Amino-2,3-dihydronaphtho[2,3-b]furanes 6a-m. The solution of compound 5a-m
(0.5 mmol) in DMSO (2.0 mL) containing NaOMe (0.75 mmol) was heated to 140 oC.
The reaction mixture was stirred at that temperature for 0.5 hour. The reaction
mixture was cooled to room temperature, subsequently quenched with saturated
NH4Cl(aq) and extracted with EtOAc. The combined organic extracts were dried over
anhydrous MgSO4(S). After filtration and removal of solvent, the residue was purified
by silica gel column chromatography to give compound 6a-m. The physical and
spectral data of 6a-m are illustrated as follows.
2,3-Dihydronaphtho[2,3-b]furan-4-amine (6a)
Yield 61.05 mg, 66%. A white solid: Rf = 0.60 (1:2:3 EA/DCM/Hex); 1H NMR (500
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MHz, CDCl3) δ 3.16 (t, J =8.0Hz, 2H), 4.06 (brs, 2H), 4.66 (t, J = 8.5 Hz, 2H), 6.56
(s, 1H), 7.25 (t, J = 8.0 Hz, 1H), 7.35 (t, J = 7.0 Hz, 1H), 7.67ꢀ7.62 (m, 2H); 13C
NMR (125 MHz, CDCl3) δ 27.1, 71.3, 95.3, 110.1, 119.7, 120.2, 122.1, 125.8, 127.5,
135.6, 137.9, 159.1; mp: 140ꢀ142 oC; MS (70 eV) m/z (%):185 (19) [M+], 85 (86), 71
(100); HRMS (EIꢀmagnetic sector) Calcd for C12H11ON, 185.0841; Found, 185.0843.
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8-Methyl-2,3-dihydronaphtho[2,3-b]furan-4-amine (6b)
Yield 74.6 mg, 75%. A white solid: Rf = 0.54 (1:2:3 EA/DCM/Hex); 1H NMR (500
MHz, CDCl3) δ 2.57 (s, 3H), 3.19 (t, J = 8.5 Hz, 2H), 4.09 (brs, 2H), 4.68 (t, J = 8.5
Hz, 2H), 6.79 (s, 1H), 7.17 (t, J = 8.5 Hz, 1H), 7.23 (d, J = 7.0 Hz, 1H), 7.56 (d, J =
8.0 Hz, 1H);13C NMR (125 MHz, CDCl3) δ 20.2, 27.1, 71.3, 92.1, 109.7, 118.4, 119.5,
121.6, 126.7, 133.6, 134.7, 138.4, 159.2 ; mp: 202ꢀ204 oC; MS (70 eV) m/z (%): 199
(100) [M+], 170 (20), 57 (16); HRMS (EIꢀmagnetic sector) Calcd for C13H13ON,
199.0997; Found, 199.0998.
7-Methyl-2,3-dihydronaphtho[2,3-b]furan-4-amine (6c)
Yield 69.6 mg, 70%. A white solid: Rf = 0.55 (1:2:3 EA/DCM/Hex); 1HNMR (500
MHz, CDCl3) δ 2.44 (s, 3H), 3.14 (t, J = 8.0 Hz, 2H), 4.03 (brs, 2H), 4.64 (t, J = 8.5
Hz, 2H), 6.57 (s, 1H), 7.08 (dd, J = 8.5, 1.5Hz, 1H), 7.40 (s, 1H), 7.55 (d, J = 8.5 Hz,
1H); 13C NMR (125 MHz, CDCl3) δ 21.4, 27.0, 71.2, 94.8, 109.2, 117.9, 120.0, 124.2,
126.7, 135.4, 135.9, 137.8, 159.2; mp: 154ꢀ156 oC; MS (70 eV) m/z (%): 199 (100)
[M+], 170 (23), 156 (123); HRMS (EIꢀmagnetic sector) Calcd for C13H13ON,
199.0997; Found, 199.0994.
6-Methyl-2,3-dihydronaphtho[2,3-b]furan-4-amine (6d)
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Yield 76.6 mg, 77%. A white solid: Rf = 0.56 (1:2:3 EA/DCM/Hex); H NMR (500
MHz, CDCl3) δ 2.48 (s, 3H), 3.16 (t, J = 8.5 Hz, 2H), 4.04 (brs, 2H), 4.66 (t, J = 8.0
Hz, 2H), 6.63 (s, 1H), 7.20 (dd, J = 8.5, 1.5 Hz, 1H), 7.44 (s, 1H), 7.54 (d, J = 8.5 Hz,
1H); 13C NMR (125 MHz, CDCl3) δ 21.7, 27.1, 71.2, 95.1, 110.2, 119.5, 119.8, 127.4,
o
127.9, 131.5, 133.6, 137.3, 158.4; mp: 112ꢀ114 C; MS (70 eV) m/z (%): 199 (100)
[M+], 200 (39), 170 (52); HRMS (EIꢀmagnetic sector) Calcd for C13H13ON, 199.0997;
Found, 199.0999.
6-Methoxy-2,3-dihydronaphtho[2,3-b]furan-4-amine (6e)
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Yield 77.4 mg, 72%. A white solid: Rf = 0.48 (1:2:3 EA/DCM/Hex); H NMR (500
MHz, CDCl3) δ 3.16 (t, J = 8.0 Hz, 2H), 3.91(s, 3H), 3.94 (brs, 2H), 4.65 (t, J = 8.5
Hz, 2H), 6.63 (s, 1H), 6.98 (d, J =2.5 Hz, 1H), 7.07 (dd, J =9.0, 2.5 Hz, 1H), 7.56 (d,
J =9.0 Hz, 1H); 13C NMR (125 MHz, CDCl3) δ 27.3, 55.4, 71.1, 95.4, 100.4, 111.1,
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117.5, 120.3, 128.9, 130.6, 136.7, 155.4, 157.5; mp: 156ꢀ158 oC; MS (70 eV) m/z (%):
215 (24) [M+],70 (66), 61 (100); HRMS (EIꢀmagnetic sector) Calcd for C13H13O2N,
215.0946; Found, 215.0948.
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Yield 66.65 mg, 67%. A white solid: Rf = 0.54 (1:2:3 EA/DCM/Hex); H NMR (500
MHz, CDCl3) δ 1.52 (d,J = 6.5 Hz, 3H), 2.76 (dd, J = 8.0, 7.0 Hz, 1H), 3.27 (dd, J =
15.0, 8.5 Hz, 1H), 5.03 (brs, 2H), 5.04ꢀ5.02 (m, 1H), 6.64 (s, 1H), 7.27ꢀ7.26 (m, 1H),
7.36ꢀ7.34 (m, 1H), 7.67ꢀ7.63 (m, 2H); 13C NMR (125 MHz, CDCl3) δ 22.0, 34.4, 79.7,
95.3, 110.4, 119.7, 120.2, 122.0, 125.7, 127.5, 135.6, 137.8, 158.7; MS (70 eV) m/z
(%): 199 (100) [M+], 184 (48), 156 (48); HRMS (EIꢀmagnetic sector) Calcd for
C13H13ON, 199.0997; Found, 199.0996.
2-Hexyl-2,3-dihydronaphtho[2,3-b]furan-4-amine (6g)
Yield 87.4 mg, 65%. A white solid: Rf = 0.56 (1:2:3 EA/DCM/Hex); 1H NMR (500
MHz, CDCl3) δ 0.91 (t, J =7.0 Hz, 3H), 0.92ꢀ1.56 (m, 9H), 1.69ꢀ1.76 (m,1H),
1.85ꢀ1.92 (m, 1H), 2.80 (dd, J =15.0, 7.0 Hz, 1H), 3.23 (dd, J = 15.0, 8.5 Hz, 1H),
4.87 (quin, J = 7.5 Hz, 1H), 6.63 (s, 1H), 7.25 (t, J = 8.5 Hz, 1H), 7.35 (t, J = 8.0 Hz,
1H), 7.65 (dd, J = 13.0, 8.0 Hz, 2H); 13C NMR (125 MHz, CDCl3) δ 14.1, 22.6, 25.4,
29.2, 31.8, 32.8, 36.3, 83.7, 95.2, 110.4, 119.6, 120.1, 121.9, 125.7, 127.5, 135.6,
137.7, 158.8; mp: 56ꢀ58 oC; MS (70 eV) m/z (%): 269 (100) [M+], 172 (55), 57 (59);
HRMS (EIꢀmagnetic sector) Calcd for C18H23ON, 269.1780; Found, 269.1781.
2-Cyclohexyl-2,3-dihydronaphtho[2,3-b]furan-4-amine (6h)
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Yield 100.1 mg, 75%. A white solid: Rf = 0.58 (1:2:3 EA/DCM/Hex); H NMR (500
MHz, CDCl3) δ 1.08ꢀ1.34 (m,5H), 1.65ꢀ1.81 (m, 5H), 2.01 (d, J = 13.0 Hz, 1H), 2.89
(dd, J = 15.0, 7.5 Hz, 1H), 3.12 (dd, J = 15.0, 9.0 Hz, 1H), 4.02 (brs, 2H), 4.60 (q, J =
7.5 Hz, 1H), 6.63 (s, 1H), 7.24 (td, J = 7.0, 1.0 Hz, 1 H), 7.35 (td, J = 7.5, 0.5 Hz, 1H),
13
7.65 (t, J = 8.5 Hz, 2H); C NMR (125 MHz, CDCl3) δ 25.7, 25.9, 26.4, 28.3, 28.6,
30.3, 43.3, 87.7, 94.9, 110.5, 119.5, 120.1, 121.8, 125.6, 127.4, 135.6, 137.6, 159.0;
mp: 56ꢀ58 C; MS (70 eV) m/z (%): 267 (49) [M+], 172 (100), 57 (54); HRMS
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(EIꢀmagnetic sector) Calcd for C18H21ON, 267.1623; Found, 267.1622.
2-Tert-butyl-2,3-dihydronaphtho[2,3-b]furan-4-amine (6i)
Yield 77.1 mg, 64%. A white solid: Rf = 0.58 (1:2:3 EA/DCM/Hex); 1H NMR (500
MHz, CDCl3) δ 1.02 (s, 9H), 2.95 (dd, J =15.0, 8.0 Hz, 1H), 3.05 (dd, J = 15.0, 9.0
Hz, 1H), 4.04 (brs, 2H), 4.58 (t, J = 8.0 Hz, 1H), 6.65 (s, 1H), 7.24 (td, J =8.0, 1.0 Hz,
1 H), 7.35 (t, J =7.5 Hz, 1H), 7.65 (t, J = 10.0 Hz, 2H); 13C NMR (125 MHz, CDCl3)
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δ25.1, 28.2, 34.6, 91.1, 94.7, 110.7, 119.5, 120.1, 121.8, 125.7, 127.5, 135.6, 137.5,
159.4; mp: 114ꢀ116 oC; MS (70 eV) m/z (%): 241 (100) [M+], 172 (92), 143 (39);
HRMS (EIꢀmagnetic sector) Calcd for C16H19ON, 241.1467; Found, 241.1469.
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Yield 50.6 mg, 48%. A white solid: Rf = 0.56 (1:2:3 EA/DCM/Hex); H NMR (500
MHz, CDCl3) δ 2.93(dd, J = 15.0, 7.0 Hz, 1H), 3.33 (dd, J = 15.0, 9.0 Hz, 1H), 4.04
(brs, 2H), 5.25ꢀ5.31(m, 2H), 5.43 (dt, J = 17.5, 1.0 Hz, 1H), 6.03ꢀ6.10 (m, 1H), 6.68
(s, 2H), 7.26 (td, J = 6.5, 1.0 Hz, 1H), 7.36 (td, J = 8.0, 1.0 Hz, 1H), 7.65 (t, J = 7.5
Hz, 2H); 13C NMR (125 MHz, CDCl3) δ 33.2, 83.6, 95.3, 109.7, 116.9, 119.7, 120.2,
122.1, 125.8, 127.6, 135.6, 137.3, 137.9, 158.5; mp:102ꢀ104 oC; MS (70 eV) m/z (%):
211 (100) [M+], 196 (100), 165 (23); HRMS (EIꢀmagnetic sector) Calcd for
C14H13ON, 211.0997; Found, 211.1000.
2-Phenyl-2,3-dihydronaphtho[2,3-b]furan-4-amine(6k)
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Yield 67.8 mg, 52%. A white solid: Rf = 0.50 (1:2:3 EA/DCM/Hex); H NMR (500
MHz, CDCl3) δ 3.13 (dd, J = 15.0, 7.0 Hz, 1H), 3.60 (dd, J = 15.0, 9.0 Hz, 1H), 4.05
(brs, 2H), 5.86 (t, J = 7.0 Hz, 1H), 6.77 (s, 1H), 7.27ꢀ7.44 (m, 7H), 7.69 (dd, J = 8.0,
5.0 Hz, 2H); 13C NMR (125 MHz, CDCl3) δ 35.8, 84.2, 95.3, 109.6, 119.8, 120.2,
122.1, 125.7, 125.9, 127.6, 128.1, 128.7, 135.7, 137.9, 142.1, 158.8; mp: 116ꢀ118 oC;
MS (70 eV) m/z (%): 261 (68) [M+], 61 (90), 57 (100); HRMS (EIꢀmagnetic sector)
Calcd for C18H15ON, 261.1154; Found, 261.1154.
2-(Naphthalen-1-yl)-2,3-dihydronaphtho[2,3-b]furan-4-amine (6l)
Yield 70.0 mg, 45%. A brown solid: Rf= 0.60 (3:1 Hex/EtOAc); 1H NMR (500 MHz,
CDCl3) δ 7.94 (d, J = 8.0 Hz, 1H), 7.90 (d, J = 8.0 Hz, 1H), 7.80 (d, J = 8.0 Hz, 1H),
7.71 (d, J = 8.0 Hz, 1H), 7.67 (d, J = 8.0 Hz. 1H), 7.65 (d, J = 8.0 Hz, 1H), 7.55ꢀ7.50
(m, 2H), 7.43 (d, J = 8.0 Hz, 1H), 7.39 (d, J = 8.0 Hz, 1H), 7.27 (d, J = 8.0 Hz, 1H),
6.86 (s, 1H), 6.53 (dd, J = 9.5, 7.0 Hz, 1H), 4.03 (brs, 2H), 3.80 (dd, J = 15.0, 9.5 Hz,
1H), 3.18 (dd, J = 15.0, 7.0 Hz, 1H); 13C NMR (125 MHz, CDCl3) δ 158.9, 138.1,
137.5, 135.8, 133.9, 129.7, 129.1, 128.3, 127.6, 126.3, 125.9, 125.7, 125.5, 123.1,
122.7, 122.2, 120.2, 119.9, 109.5, 95.5, 82.1, 35.6;mp: 161ꢀ162 oC; MS (ESI) m/z (%):
312 [M+H]+; HRMS (ESIꢀTOF) Calcd for C22H18NO [M+H]+, 312.1388; Found,
312.1386.
2-(4-Methoxyphenyl)-2,3-dihydronaphtho[2,3-b]furan-4-amine (6m)
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Yield 66.0 mg, 45%. A yellow oil: Rf= 0.50 (2:1 Hex/EtOAc); H NMR (500 MHz,
CDCl3) δ 7.69 (d, J = 7.5 Hz, 1H), 7.67 (d, J = 7.5 Hz, 1H), 7.38 (t, J = 7.5 Hz, 1H),
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7.36 (d, J = 9.0 Hz, 2H), 7.28 (t, J = 7.5 Hz, 1H), 6.91 (d, J = 9.0 Hz, 2H), 6.73 (s,
1H), 5.81 (dd, J = 9.0, 7.5 Hz, 1H), 4.10 (brs, 2H), 3.81 (s, 3H), 3.56 (dd, J = 15.0, 9.0
Hz, 1H), 3.14 (dd, J = 15.0, 7.5 Hz, 1H); 13C NMR (125 MHz, CDCl3) δ 159.5, 158.8,
137.8, 135.7, 134.0, 127.6, 127.2, 125.9, 122.1, 120.2, 119.8, 114.0, 109.9, 95.3, 84.1,
55.3, 35.7; MS (ESI) m/z (%): 292 [M+H]+; HRMS (ESIꢀTOF) Calcd for C19H18NO2
[M+H]+, 292.1337; Found, 292.1338.
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Furo[2',3':6,7]naphtho[2,3-d][1,3]dioxol-9-amine (6n)
Yield 66.4 mg, 58%. A colorless solid: Rf= 0.48 (1:2:3 EA/DCM/Hex); 1H NMR (500
MHz, CDCl3) δ 3.15 (t, J = 8.0 Hz, 2H), 3.86 (brs, 2H), 4.64 (t, J = 8.0 Hz, 2H), 5.99
(s, 2H), 6.55 (s, 1H), 6.96 (s, 1H), 7.1 (s, 1H); 13C NMR (125 MHz, CDCl3) δ 27.2,
71.3, 95.8, 97.6, 100.9, 104.1, 109.3, 115.1, 132.4, 137.3, 145.2, 147.5, 158.3; mp:
o
214ꢀ216 C; MS (70 eV) m/z (%): 229 (34) [M+], 61 (100), 57 (53); HRMS
(EIꢀmagnetic sector) Calcd for C13H11O3N, 229.0739; Found, 229.0741.
(Z)-2-Benzylidenetetrahydrofuran (7a)
Yield 70.0 mg, 64%. A colorless oil: Rf = 0.80 (2:1 Hex/EtOAc); 1H NMR (400 MHz,
CDCl3) δ 8.17 (d, J = 8.0 Hz, 1H), 7.54 (d, J = 8.0 Hz, 1H), 7.47 (t, J = 8.0 Hz, 1H),
7.10 (t, J = 8.0 Hz, 1H), 5.68 (s, 1H), 4.39 (t, J = 7.2 Hz, 2H), 2.82 (t, J = 7.2 Hz, 2H),
2.08 (quin, J = 7.2 Hz, 2H); 13C NMR (100 MHz, CDCl3) δ 161.9, 140.4, 132.5, 132.4,
127.6, 124.3, 118.9, 108.6, 93.1, 73.0, 31.6, 24.0; MS (ESI) m/z (%): 208 [M+Na]+,
186 [M+H]+; HRMS (ESIꢀTOF) Calcd for C12H11NONa [M+Na]+, 208.0738; Found,
208.0736.
(E)-2-Benzylidenetetrahydrofuran (8a)
Yield 13.0 mg, 51%. A colorless oil: Rf = 0.78 (2:1 Hex/EtOAc); 1H NMR (400 MHz,
CDCl3) δ 7.57 (d, J = 8.0 Hz, 1H), 7.47 (t, J = 8.0 Hz, 1H), 7.33 (d, J = 8.0 Hz, 1H),
7.14 (t, J = 8.0 Hz, 1H), 6.23 (s, 1H), 4.31 (t, J = 7.2 Hz, 2H), 2.82 (t, J = 7.2 Hz, 2H),
2.14 (quin, J = 7.2 Hz, 2H); 13C NMR (100 MHz, CDCl3) δ 163.2, 141.6, 133.0, 132.2,
126.5, 124.6, 118.5, 110.6, 95.9, 70.2, 28.9, 25.0; MS (ESI) m/z (%): 208 [M+Na]+,
186 [M+H]+; HRMS (ESIꢀTOF) Calcd for C12H11NONa [M+Na]+, 208.0738; Found,
208.0737.
4-Amino-3-vinylnaphthalen-2-ol (9a)
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Yield 41.0 mg, 43%. A yellow oil: Rf = 0.60 (2:1 Hex/EtOAc); H NMR (400 MHz,
CDCl3) δ 8.46 (s, 1H), 7.95 (d, J = 8.0 Hz, 1H), 7.49 (d, J = 8.0 Hz, 1H), 7.29 (t, J =
8.0 Hz, 1H), 7.17 (t, J = 8.0 Hz, 1H), 6.96 (dd, J = 18.4, 12.0 Hz, 1H), 6.63 (s, 1H),
5.76 (dd, J = 18.4, 2.0 Hz, 1H), 5.55 (dd, J = 12.0, 2.0 Hz, 1H), 5.30 (brs, 2H); 13C
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NMR (100 MHz, CDCl3) δ 155.7, 143.9, 136.3, 132.5, 127.7, 127.6, 123.6, 123.0,
120.6, 118.8, 110.3, 100.5; MS (ESI) m/z (%): 186 [M+H]+; HRMS (ESIꢀTOF) Calcd
for C12H12NO [M+H]+, 186.0919; Found, 186.0917.
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General Procedure for the preparation of dihydrofuranonaphthoquinones 10a-k
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and 10n: To the stirred solution of Fermy’s salt (402 mg, 1.5 mmol) in H2O (2 mL)
containing KH2PO4 (204 mg, 1.5 mmol) was added a solution of compound 6a-k or 6n
(0.5 mmol) in acetone (1 mL) at room temperature. The reaction mixture was stirred
at room temperature for 2 hours. Subsequently the saturated NaCl(aq) was added and
the mixture was extracted with CH2Cl2. The combined organic extracts were dried
over anhydrous MgSO4(S). After filtration and removal of solvent, the residue was
purified by silica gel column chromatography to give compound 10a-k and 10n. The
physical and spectral data of 10a-k and 10n are illustrated as follows.
2,3-Dihydronaphtho[2,3-b]furan-4,9-dione (10a)
Yield 88.0 mg, 88%. A yellow solid: Rf = 0.62 (1:2:3 EA/DCM/Hex); 1H NMR (500
MHz, CDCl3) δ 3.22 (t, J = 10.0 Hz, 2H), 4.80 (t, J = 10 Hz, 2H), 7.66ꢀ7.14 (m, 2H),
8.07 (dd, J = 7.5, 1.5 Hz, 2H); 13C NMR (125 MHz, CDCl3) δ 27.3, 73.2, 124.4, 126.0,
126.2, 131.4, 133.0, 133.0, 134.1, 160.7, 177.7, 182.1; mp: 200ꢀ202 oC; MS (70 eV)
m/z (%): 200 (100) [M+], 172 (39), 104 (47); HRMS (EIꢀmagnetic sector) Calcd for
C12H8O3, 200.0473; Found, 200.0475.
8-Methyl-2,3-dihydronaphtho[2,3-b]furan-4,9-dione (10b)
Yield 49.22 mg, 46%. A yellow solid: Rf = 0.62 (1:2:3 EA/DCM/Hex); 1H NMR (500
MHz, CDCl3) δ 2.74 (s, 3H), 3.21 (t, J = 9.5Hz, 2H), 4.78 (t, J = 9.5 Hz, 2H), 7.45 (dd,
J = 7.5, 0.5 Hz, 1H), 7.56 (t, J = 7.5 Hz, 1H), 8.01 (dd, J = 8.0, 1.0 Hz, 1H); 13C NMR
(125 MHz, CDCl3) δ 22.8, 27.2, 73.2, 122.6, 125.0, 128.9, 133.2, 134.7, 137.17,
141.8, 161.5, 179.6, 182.2; mp: 168ꢀ170 oC; MS (70 eV) m/z (%): 214 (52) [M+], 61
(83), 57 (100); HRMS (EIꢀmagnetic sector) Calcd for C13H10O3, 214.0630; Found,
214.0633.
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7-Methyl-2,3-dihydronaphtho[2,3-b]furan-4,9-dione (10c)
Yield 98.4 mg, 92%. A yellow solid: Rf = 0.64 (1:2:3 EA/DCM/Hex); 1H NMR (500
MHz, CDCl3) δ 2.47 (s, 3H), 3.20 (t, J = 10.0 Hz, 2H), 4.79 (t, J = 9.5 Hz, 2H), 7.45
(d, J = 8.0 Hz,1H), 7.85 (s, 1H), 7.94 (d, J = 8.0 Hz, 1H); 13C NMR (125 MHz, CDCl3)
δ 21.6, 27.3, 73.2, 124.3, 126.2, 126.8, 130.7, 131.4, 134.7, 144.0, 160.6, 178.0, 182.2;
mp: 196ꢀ198 oC; MS (70 eV) m/z (%): 214 (100) [M+], 186 (64), 118 (46); HRMS
(EIꢀmagnetic sector) Calcd for C13H10O3, 214.0630; Found, 214.0633.
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6-Methyl-2,3-dihydronaphtho[2,3-b]furan-4,9-dione (10d)
Yield 98.4 mg, 92%. A yellow solid: Rf = 0.60 (1:2:3 EA/DCM/Hex); 1H NMR (500
MHz, CDCl3) δ 2.48 (s, 3H), 3.20 (t, J = 10.0 Hz, 2H), 4.79 (t, J =10.0 Hz, 2H), 7.46
(d, J = 8.0 Hz, 1H), 7.86 (s, 1H), 7.95 (d, J = 8.0 Hz, 1H); 13C NMR (125 MHz,
CDCl3) δ 21.9, 27.3, 73.3, 124.1, 126.5, 126.6, 129.2, 133.0, 133.5, 145.5, 160.9,
177.7, 182.5; mp: 182ꢀ184 oC; MS (70 eV) m/z (%):214 (100) [M+], 186 (65), 57 (70);
HRMS (EIꢀmagnetic sector) Calcd for C13H10O3, 214.0630; Found, 214.0633.
6-Methoxy-2,3-dihydronaphtho[2,3-b]furan-4,9-dione (10e)
Yield 101.2 mg, 88%. A yellow solid: Rf = 0.55 (1:2:3 EA/DCM/Hex);1HNMR (500
MHz, CDCl3) δ 3.20 (t, J = 10.0 Hz, 2H), 3.94 (s, 3H), 4.79 (t, J = 10.0 Hz, 2H), 7.10
(dd, J = 8.5, 3.5 Hz, 1H), 7.53 (d, J = 2.0 Hz, 1H), 8.01 (d, J = 8.5 Hz, 1H); 13C NMR
(125 MHz, CDCl3) δ 27.3, 55.9, 73.4, 110.6, 118.4, 123.8, 124.8, 128.8, 135.6, 161.3,
164.6, 176.9, 182.0; mp: 182ꢀ184 oC; MS (70 eV) m/z (%): 230 (15) [M+], 71 (71), 57
(100); HRMS (EIꢀmagnetic sector) Calcd for C13H10O4, 230.0579; Found, 230.0578.
2-Methyl-2,3-dihydronaphtho[2,3-b]furan-4,9-dione (10f)
Yield 98.42 mg, 92%. A yellow solid: Rf = 0.60 (1:2:3 EA/DCM/Hex); 1H NMR (500
MHz, CDCl3) δ 1.56 (d, J = 6.0 Hz, 3H), 2.80 (dd, J = 17.0, 9.0 Hz, 1H), 3.33 (dd, J =
17.0, 10.0 Hz, 1H), 5.15ꢀ5.22 (m, 1H), 7.65ꢀ7.72 (m, 2H), 8.06 (dd, J = 6.0, 4.5 Hz,
2H); 13C NMR (125 MHz, CDCl3) δ 21.9, 34.3, 83.1, 123.8, 126.0, 126.3, 131.5,
132.9, 133.1, 134.1, 159.8, 178.0, 182.4; MS(70 eV) m/z (%): 214 (100) [M+], 186
(56), 158 (42); HRMS (EIꢀmagnetic sector) Calcd for C13H10O3, 214.0630; Found,
214.0632.
2-Hexyl-2,3-dihydronaphtho[2,3-b]furan-4,9-dione (10g)
Yield 115.0 mg, 81%. A yellow solid: Rf = 0.60 (1:2:3 EA/DCM/Hex); 1H NMR (500
MHz, CDCl3) δ 0.87 (t, J = 6.5 Hz, 3H), 1.23ꢀ1.53 (m, 8H), 1.69ꢀ1.76 (m, 1H),
1.86ꢀ1.93 (m, 1H), 2.83 (dd, J = 17.0, 8.5 Hz, 1H), 3.26 (dd, J = 17.0, 10.0 Hz, 1H),
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4.99ꢀ5.06 (m, 1H), 7.62ꢀ7.70 (m, 2H), 8.03 (td, J = 7.0, 1.0 Hz, 2H); 13C NMR (125
MHz, CDCl3) δ 14.0, 22.5, 24.7, 28.9, 31.6, 32.5, 35.9, 86.8, 123.9, 125.9, 126.2,
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131.5, 132.8, 133.0, 134.0, 160.0, 177.9, 182.3; mp: 84ꢀ86 C; MS (70 eV) m/z
(%):284 (36) [M+], 71 (89), 57 (100); HRMS (EIꢀmagnetic sector) Calcd for C18H20O3,
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284.1412; Found, 284.1410.
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2-Cyclohexyl-2,3-dihydronaphtho[2,3-b]furan-4,9-dione (10h)
Yield 108.5 mg, 77%. A yellow solid: Rf = 0.60 (1:2:3 EA/DCM/Hex); 1H NMR (500
MHz, CDCl3) δ 1.07ꢀ1.31 (m, 5H), 1.70ꢀ1.81 (m , 5H), 1.96 (d, J = 13.0 Hz, 1H),
2.96 (dd, J = 17.0, 8.5 Hz, 1H), 3.17 (dd, J = 17.5, 10.5 Hz, 1H), 4.78ꢀ4.83 (m, 1H),
7.65ꢀ7.72 (m, 2H), 8.07 (td, J = 7.5, 1.0 Hz, 2H); 13C NMR (125 MHz, CDCl3) δ 25.5,
25.7, 26.2, 27.6, 28.0, 29.7, 30.0, 42.7, 90.7, 124.1, 125.9, 126.3, 131.6, 132.9, 133.1,
134.1, 160.3, 177.9, 182.3; mp: 54ꢀ56 oC; MS (70 eV) m/z (%):282 (32) [M+], 71 (86),
57 (100); HRMS (EIꢀmagnetic sector) Calcd for C18H18O3, 282.1256; Found,
282.1256.
2-(Tert-butyl)-2,3-dihydronaphtho[2,3-b]furan-4,9-dione (10i)
Yield 112.6 mg, 88%. A yellow solid: Rf= 0.62 (1:2:3 EA/DCM/Hex); 1H NMR (500
MHz, CDCl3) δ 1.01 (s, 3H), 2.99 (dd, J = 17.5, 9.0 Hz,1H), 3.10 (dd, J = 17.5, 11.0
Hz, 1H), 4.74 (t, J = 9.5 Hz, 1H), 7.65ꢀ7.72 (m, 2H), 8.07 (td, J =7.5, 1.0 Hz, 2H);
13C NMR (125 MHz, CDCl3) δ 24.7, 28.3, 34.7, 94.2, 124.4, 125.9, 126.3, 131.6,
132.9, 133.0, 134.1, 160.4, 177.8, 182.4; mp: 116ꢀ118 oC; MS (70 eV) m/z (%): 256
(40) [M+], 70 (100), 57 (100); HRMS (EIꢀmagnetic sector) Calcd for C16H16O3,
256.1099; Found, 256.1098.
2-Vinyl-2,3-dihydronaphtho[2,3-b]furan-4,9-dione (10j)
Yield 105.1 mg, 93%. A yellow solid: Rf = 0.61 (1:2:3 EA/DCM/Hex); 1H NMR (500
MHz, CDCl3) δ 3.00 (dd, J = 17.0, 8.0 Hz, 1H), 3.39 (dd, J = 17.5, 11.0 Hz, 1H),
5.33 (d, J = 10.5 Hz, 1H), 5.42ꢀ5.48 (m, 2H), 5.99ꢀ6.06 (m, 1H), 7.65ꢀ7.73 (m, 2H),
8.06 (td, J = 7.5, 1.0 Hz, 2H); 13C NMR (125 MHz, CDCl3) δ 33.0, 86.1, 118.4, 123.8,
126.0, 126.3, 131.5, 133.0, 134.1, 135.1, 159.7, 177.7, 182.2; mp: 102ꢀ104 oC; MS
(70 eV) m/z (%): 226 (58) [M+], 198 (100), 104 (99); HRMS (EIꢀmagnetic sector)
Calcd for C14H10O3, 226.0630; Found, 226.0632.
2-Phenyl-2,3-dihydronaphtho[2,3-b]furan-4,9-dione (10k)
Yield 115.9 mg, 84%. A yellow solid: Rf= 0.58 (1:2:3 EA/DCM/Hex); 1H NMR (500
MHz, CDCl3) δ 3.27 (dd, J = 17.5, 8.5 Hz, 1H), 3.67 (dd, J = 17.0, 11.0 Hz, 1H),
5.02 (dd, J = 11.0, 7.5 Hz, 1H), 7.35ꢀ7.41 (m, 5H), 7.68ꢀ7.75 (m, 2H), 8.10 (td, J =
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8.5, 1.0 Hz, 2H); 13C NMR (125 MHz, CDCl3) δ 35.3, 86.8, 123.8, 126.0, 126.1,
126.4, 128. 9, 131.6, 133.0, 134.2, 139.5, 159.8, 177.7, 182.2; mp: 102ꢀ104 oC; MS
(70 eV) m/z (%): 276 (6) [M+], 70 (100), 61 (100); HRMS (EIꢀmagnetic sector) Calcd
for C18H12O3, 276.0786; Found, 276.0789.
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7,8-Dihydrofuro[2',3':6,7]naphtho[2,3-d][1,3]dioxole-5,9-dione (10n)
Yield 91.5 mg, 75%. A yellow solid: Rf= 0.52 (1:2:3 EA/DCM/Hex); 1H NMR (500
MHz, CDCl3) δ 3.18 (t, J = 10.0 Hz, 2H), 4.77 (t, J = 10.0 Hz, 2H), 6.13 (s , 2H), 7.46
(d, J = 6.0 Hz, 1H); 13C NMR (125 MHz, CDCl3) δ 27.3, 73.4, 102.7, 106.0, 106.1,
123.4, 127.9, 130.4, 151.5, 152.5, 160.7, 176.7, 181.2; mp: 220ꢀ222 oC; MS (70 eV)
m/z (%): 244 (13) [M+], 71 (86), 57 (100); HRMS (EIꢀmagnetic sector) Calcd for
C13H8O5, 244.0372; Found, 244.0373.
General Procedure for the preparation of furanonaphthoquinones 11a-e, 4, 11g-i,
11k and 11n: The solution of 10a-i, 10k and 10n (0.1 mmol) in diphenyl ether (2 mL)
containing Pd/C (20.0 mg) was placed in the high pressure reactor and the reaction
mixture was heated to 260 oC and stirred for 8 hours. After cooling to room
temperature, the reaction mixture was directly purified by silica gel column
chromatography to give compound 11a-e, 4, 11g-i, 11k and 11n. The physical and
spectral data of 11a-e, 4, 11g-i, 11k and 11n are illustrated as follows.
Naphtho[2,3-b]furan-4,9-dione (11a)
Yield 14.8 mg, 75%. A yellow solid: Rf = 0.64 (1:2:3 EA/DCM/Hex); 1H NMR (500
MHz, CDCl3) δ 7.01 (d, J = 2.0 Hz, 1H), 7.75ꢀ7.78 (m, 3H), 8.19ꢀ8.24 (m, 2H); 13C
NMR (125 MHz, CDCl3) δ 108.6, 126.9, 127.1, 130.5, 132.5, 133.2, 133.9, 134.0,
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148.6, 152.7, 173.6, 180.5; mp: 198ꢀ200 C; MS (70 eV) m/z (%): 198 (100) [M+],
170 (42), 114 (40); HRMS (EIꢀmagnetic sector) Calcd for C12H6O3, 198.0317; Found,
198.0317.
8-Methylnaphtho[2,3-b]furan-4,9-dione (11b)
Yield 13.1 mg, 62%. A yellow solid: Rf = 0.60 (1:2:3 EA/DCM/Hex); 1H NMR (500
MHz, CDCl3) δ 2.84 (s, 3H), 6.95 (d, J = 1.5 Hz, 1H), 7.53 (d, J = 7.5 Hz, 1H), 7.59 (t,
J = 7.5 Hz, 1H), 7.72 (d, J = 1.5 Hz, 1H), 8.14 (d, J = 7.5 Hz, 1H); 13C NMR (125
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MHz, CDCl3) δ 23.0, 108.1, 126.1, 128.7, 129.6, 133.0, 134.9, 138.3, 142.5, 148.1,
153.5, 176.0, 180.6; mp: 230ꢀ232 oC; MS (70 eV) m/z (%): 212 (100) [M+], 61 (72),
57 (94); HRMS (EIꢀmagnetic sector) Calcd for C13H8O3, 212.0473; Found, 212.0473.
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7-Methylnaphtho[2,3-b]furan-4,9-dione (11c)
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Yield 16.3 mg, 77%. A yellow solid: Rf = 0.61 (1:2:3 EA/DCM/Hex); 1H NMR (500
MHz, CDCl3) δ 2.51 (s, 3H), 6.99 (d, J = 1.5 Hz, 1H), 7.53 (dd, J = 8.0, 1.0 Hz, 1H),
7.76 (d, J = 1.5 Hz, 1H), 8.02 (d, J = 0.5 Hz, 1H), 8.08 (d, J = 8.0 Hz, 1H); 13C NMR
(125 MHz, CDCl3) δ 21.8, 108.6, 127.3, 127.5, 130.5, 131.0, 132.4, 134.4, 145.2,
148.5, 152.7, 173.9, 180.5; mp: 184ꢀ186 oC; MS (70 eV) m/z (%): 212 (43) [M+], 85
(79), 57 (100); HRMS (EIꢀmagnetic sector) Calcd for C13H8O3, 212.0473; Found,
212.0473.
6-Methylnaphtho[2,3-b]furan-4,9-dione (11d)
Yield 15.2 mg, 72%. A yellow solid: Rf = 0.60 (1:2:3 EA/DCM/Hex); 1H NMR (500
MHz, CDCl3) δ 2.51 (s, 3H), 6.98 (d, J = 1.5 Hz, 1H), 7.55 (d, J = 8.0 Hz, 1H), 7.75
(d, J = 1.5 Hz, 1H), 7.98 (s, 1H), 8.10 (d, J = 8.0 Hz, 1H); 13C NMR (125 MHz,
CDCl3) δ 21.8, 108.6, 127.1, 127.6, 130.2, 130.3, 133.2, 134.5, 145.1, 148.4, 152.9,
173.6, 180.9; mp: 174ꢀ176 oC; MS (70 eV) m/z (%): 212 (100) [M+], 184 (26), 128
(35); HRMS (EIꢀmagnetic sector) Calcd for C13H8O3, 212.0473; Found, 212.0470.
6-Methoxynaphtho[2,3-b]furan-4,9-dione (11e)
Yield 16.4 mg, 68%. A yellow solid: Rf = 0.60 (1:2:3 EA/DCM/Hex);1H NMR (500
MHz, CDCl3) δ 6.16 (s, 2H), 6.95 (d, J = 2.0 Hz, 1H), 7.85 (s, 1H), 7.60 (s,1H), 7.72
(d, J = 2.0 Hz, 1H); 13C NMR (125 MHz, CDCl3) δ 29.7, 102.8, 106.6, 106.8, 108.6,
129.3, 123.0, 130.3, 148.2, 152.3, 152.6, 172.7, 179.5; mp: 184ꢀ186 oC; MS (70 eV)
m/z (%): 242 (25) [M+], 70 (65), 61 (100); HRMS (EIꢀmagnetic sector) Calcd for
C13H6O5, 242.0215; Found, 242.0212.
FNQ3 (4)
Yield 13.64 mg, 65%. A yellow solid: Rf = 0.65 (1:2:3 EA/DCM/Hex); 1H NMR (500
MHz, CDCl3) δ 2.52 (s, 3H), 6.61 (d, J = 0.5Hz, 1H), 7.72ꢀ7.74 (m, 2H), 8.15ꢀ8.21 (m,
2H); 13C NMR (125 MHz, CDCl3) δ 14.1, 29.7, 105.0, 126.8, 126.9, 131.9, 132.5,
133.1, 133.6, 133.8, 151.7, 160.5, 173.1, 180.9; MS (70 eV) m/z (%): 212 (100) [M+],
184 (37), 183 (81); HRMS (EIꢀmagnetic sector) Calcd for C13H8O3, 212.0473; Found,
212.0470.
2-Hexylnaphtho[2,3-b]furan-4,9-dione (11g)
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Yield 13.5 mg, 48%. A yellow solid: Rf = 0.65 (1:2:3 EA/DCM/Hex); 1H NMR (500
MHz, CDCl3) δ 0.88ꢀ0.91 (m, 3H), 1.25ꢀ1.33 (m, 8H), 1.58ꢀ1.77 (m, 2H), 2.80 (t, J =
7.5 Hz, 2H), 7.70ꢀ7.75 (m, 2H), 8.15ꢀ8.21 (m, 2H); 13C NMR (125 MHz, CDCl3) δ
14.0, 22.5, 27.4, 28.3, 28.7, 29.7, 31.4, 104.2, 126.8, 126.8, 131.8, 132.6, 133.1, 133.5,
133.8, 151.5, 164.9, 173.1, 181.0; mp: 86ꢀ88 oC; MS (70 eV) m/z (%): 282 (27) [M+],
61 (100), 57 (85); HRMS (EIꢀmagnetic sector) Calcd for C18H18O3, 282.1256; Found,
282.1258.
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2-Cyclohexylnaphtho[2,3-b]furan-4,9-dione (11h)
Yield 10.6 mg, 38%. A yellow solid: Rf = 0.66 (1:2:3 EA/DCM/Hex); 1H NMR (500
MHz, CDCl3) δ 1.24ꢀ1.54 (m, 6H), 1.72ꢀ1.86 (m, 2H), 2.80 (dd, J = 13.0, 3.0 Hz, 2H),
2.78ꢀ2.84 (m, 1H), 7.69ꢀ7.75 (m, 2H), 8.14ꢀ8.21 (m, 2H); 13C NMR (125 MHz,
CDCl3) δ 25.6, 25.7., 31.0, 37.5, 102.4, 126.8, 126.8, 131.7, 132.6, 133.1, 133.5,
133.8, 151.3, 168.9, 173.2, 181.1; mp: 106ꢀ108 oC; MS (70 eV) m/z (%): 280 (80)
[M+], 71(87), 57 (100); HRMS (EIꢀmagnetic sector) Calcd for C18H16O3, 280.1099;
Found, 280.1099.
2-(Tert-butyl)naphtho[2,3-b]furan-4,9-dione (11i)
Yield 21.8 mg, 86%. A yellow solid: Rf = 0.66 (1:2:3 EA/DCM/Hex); 1H NMR (500
MHz, CDCl3) δ1.40 (s, 9H), 7.69ꢀ7.75 (m, 2H), 8.14ꢀ8.21 (m, 2H); 13C NMR (125
MHz, CDCl3) δ 28.7, 29.7, 33.5, 101.6, 126.8, 131.6, 132.7, 133.1, 133.5, 133.8,
151.5, 172.2, 173.2, 181.1; mp: 54ꢀ56 oC; MS (70 eV) m/z (%): 254 (18) [M+], 240
(18), 239 (100); HRMS (EIꢀmagnetic sector) Calcd for C16H14O3, 254.0943; Found,
254.0943.
2-Phenylnaphtho[2,3-b]furan-4,9-dione (11k)
Yield 17.2 mg, 63%. A yellow solid: Rf = 0.62 (1:2:3 EA/DCM/Hex); 1H NMR (500
MHz, CDCl3) δ 7.20 (s, 1H), 7.43ꢀ7.51 (m, 3H), 7.73ꢀ7.79 (m, 2H), 7.90 (d, J = 7.5
Hz, 2H), 8.19ꢀ8.26 (m, 2H); 13C NMR (125 MHz, CDCl3) δ 102.9, 125.5, 126.9,
126.9, 128.3, 129.1, 130.3, 132.4, 132.8, 133.7, 133.6, 134.0, 151.6, 160.3, 173.0,
180.8; mp: 224ꢀ226 oC; MS (70 eV) m/z (%): 274 (7) [M+], 71 (93), 57 (100); HRMS
(EIꢀmagnetic sector) Calcd for C18H10O3, 274.0630; Found, 274.0627.
Furo[2',3':6,7]naphtho[2,3-d][1,3]dioxole-5,9-dione (11n)
Yield 12.5 mg, 52%. A yellow solid: Rf = 0.61 (1:2:3 EA/DCM/Hex); 1H NMR (500
MHz, CDCl3) δ 6.16 (s, 2H), 6.95 (d, J = 2.0 Hz, 1H), 7.85 (s, 1H), 7.60 (s, 1H), 7.72
(d, J = 2.0 Hz, 1H); 13C NMR (125 MHz, CDCl3) δ 29.7, 102.8, 106.6, 106.8, 108.6,
129.3, 123.0, 130.3, 148.2, 152.3, 152.6, 172.7, 179.5; mp: 184ꢀ186 oC; MS (70 eV)
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m/z (%): 242 (25) [M+], 70 (65), 61 (100); HRMS (EIꢀmagnetic sector) Calcd for
C13H6O5, 242.0215; Found, 242.0212.
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2-(5-Oxopent-1-yn-1-yl)benzonitrile (12)
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To the solution of oxalyl dichloride (5.14 g, 40.53 mmol) inCH2Cl2 (50 mL) at -78 C
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was added DMSO (3.16 g, 40.53 mmol) dropwise for 0.5 hour. Subsequently
compound 5a (5.0 g, 27.02 mmol) was added into the reaction mixture and stirred
for another 1.5 hours. Et3N (20.46 g, 202.65 mmol) was then injected slowly to the
reaction mixture. After warming to room temperature, the reaction mixture was
poured into saturated NH4Cl(aq) and extracted with EtOAc. The combined organic
extracts were dried over anhydrous MgSO4(S). After filtration and removal of solvent,
the residue was purified by column chromatography to give compound 12. Yield
3.95 g, 80%. A yellow oil: Rf = 0.41 (3:1 Hex/EtOAc); 1H NMR (500 MHz, CDCl3) δ
2.71ꢀ2.86 (m, 4H), 7.34ꢀ7.37 (m, 1H), 7.46ꢀ7.52 (m, 2H), 7.60 (d, J = 7.5 Hz, 1H),
9.85 (s, 1H); 13C NMR (125 MHz, CDCl3) δ 12.7, 15.2, 32.8, 77.9, 95.2, 115.3, 117.6,
127.3, 127.9, 132.1, 132.3, 132.3, 132.4, 132.4, 176.1, 199.9; MS (70 eV) m/z (%):
183 (11) [M+], 154 (100), 127 (85), 57 (72); HRMS (EIꢀmagnetic sector) Calcd for
C12H9ON, 183.0684; Found, 183.0684.
Acknowledgment: We thank the Ministry of Science and Technology of the Republic
of China for financial support.
Supporting Information Available: The supporting information is available free of
charge on the ACS Publication website at http://pubs.acs.org. The scheme for
1
preparation of compounds 5a-5n; H NMR and 13C NMR Spectra (PDF) of all
compounds.
References:
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