Electroreductive Intermolecular Coupling of Chromones with Benzophenones: Synthesis of 2-Diarylmethylchromones and Tetrasubstituted Furans

Article abstract of DOI:10.1002/ejoc.201900519

The electroreductive coupling of chromones with benzophenones in the presence of TMSCl gave adducts reacted at the 2-position of chromones as trimethylsilyl ethers. From 3-methyl- and 3-phenylchromones, 2,3-cis-adducts were formed predominantly. The cis-adducts were isomerized to trans-ones by treatment with DBU. The detrimethylsilylation of the adducts with 1 M HCl aq/dioxane produced the corresponding alcohols. The dehydrosiloxylation of the adducts or dehydration of the desilylated alcohols brought about 2-diarylmethylchromones. The detrimethylsilylation of the adducts with TBAF and subsequent treatment with NaH afforded ring-opening products. The dehydration of the ring-opening products obtained from 3-methyl- and 3-phenylchromons brought about tetrasubstituted furans or dihydrobenzofuran-3-ones. The dehydrogenation of the adducts with DDQ and subsequent desilylation with 1 M HCl aq/dioxane gave 2-(diarylhydroxymethyl)chromones.

Full text of DOI:10.1002/ejoc.201900519

A Journal of
Accepted Article
Title: Electroreductive Intermolecular Coupling of Chromones with
Benzophenones: Synthesis of 2-Diarylmethylchromones and
Tetrasubstituted Furans
Authors: Naoki Kise, Hiroaki Nagamine, and Toshihiko Sakurai
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To be cited as: Eur. J. Org. Chem. 10.1002/ejoc.201900519
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10.1002/ejoc.201900519
European Journal of Organic Chemistry
FULL PAPER
synthetic route to 2-subsutituted chromones. Although the
titanium(III)-mediated double-reductive coupling of chromones
with acrylonitrile has been reported,[7] the reductive coupling of
chromones with carbonyl compounds is hitherto unknown
(Scheme 1). We report in this paper that the cross-coupled
products reacted at the 2-position of chromones were obtained as
trimethylsilyl ethers by the electroreduction of chromones with
benzophenones in the presence of TMSCl. From 2-substituted
chromones (R1 = Me, Ph; R2 = H), 2,3-cis-adducts were produced
with complete stereoselectivity (Scheme 1). In addition, we
investigated several transformations of the adducts (Scheme 2).
Direct dehydrosiloxylation of the adducts (R2 = H) with cat. p-
TsOH in refluxing xylene gave 2-diarylmethylchromones. The
same compounds were obtained by desilylation of the
trimethylsilyl ethers with 1 M HCl aq and subsequent dehydration
of the resultant alcohols by reflux in cat. p-TsOH/toluene. In
contrast, desilylation of the adducts with TBAF and subsequent
treatment with NaH brought about ring-opening products. The
ring-opening products (R1 = Me, Ph; R2 = H) were transformed to
tetrasubstituted furans, which were attracting as pharmaceuticals
and functional materials,[8] by reflux in cat. TsOH/toluene. The
cis-adducts (R1 = Me, Ph; R2 = H) could be isomerized to trans-
alcohols by treatment with DBU and subsequent desilylation with
1 M HCl aq. The dehydrogenation of the adducts with DDQ in
dioxane and following desilylation with 1 M HCl aq gave 2-
(diarylhydroxymethyl)chromones. Reaction mechanisms of the
electroreductive coupling and the transformations of the adducts
were also discussed.
Reductive Coupling
Electroreductive Intermolecular
Coupling of Chromones with
Benzophenones: Synthesis of
2-Diarylmethylchromones and
Tetrasubstituted Furans
Naoki Kise,*[a],[b] Hiroaki Nagamine,[a] and Toshihiko
Sakurai[a],[b]
Abstract: The electroreductive coupling of chromones with
benzophenones in the presence of TMSCl gave adducts reacted at
the 2-position of chromones as trimethylsilyl ethers. From 3-methyl-
and 3-phenylchromones, 2,3-cis-adducts were formed predominantly.
The cis-adducts were isomerized to trans-ones by treatment with DBU.
The detrimethylsilylation of the adducts with 1 M HCl aq/dioxane
produced the corresponding alcohols. The dehydrosiloxylation of the
adducts or dehydration of the desilylated alcohols brought about 2-
diarylmethylchromones. The detrimethylsilylation of the adducts with
TBAF and subsequent treatment with NaH afforded ring-opening
products. The dehydration of the ring-opening products obtained from
3-methyl- and 3-phenylchromons brought about tetrasubstituted
furans or dihydrobenzofuran-3-ones. The dehydrogenation of the
adducts with DDQ and subsequent desilylation with 1 M HCl
aq/dioxane gave 2-(diarylhydroxymethyl)chromones.
Introduction
Chromone ring is the core skeleton of plant-derived flavonoids
such as flavones and isoflavones (Figure 1).
Recently,
chromones are attracting much attention as a valid scaffold in
medicinal chemistry.[1] Therefore, the conjugate additions to
chromones have extensively been studied for the synthesis of 2-
substituted chromone derivatives.[2] On the other hand, we have
reported the electroreductive cross-coupling of heterocycles,
such as phthalimides,[3] indoles,[4] uracils,[5] and coumarins[6] with
Figure 1. Chromone and Flavonoids (Flavones and Isoflavones).
carbonyl compounds.
In this regard, we attempted the
electroreductive cross-coupling of chromones with carbonyl
compounds, since this reaction is expected to provide a new
[a]
[b]
Prof. N. Kise, H. Nagamine, Dr. T. Sakurai
Department of Chemistry and Biotechnology,
Graduate School of Engineering, Tottori University
4-101, Koyama-cho Minami, Tottori 680-8552, (Japan)
E-mail: kise@tottori-u.ac.jp
Prof. N. Kise, Dr. T. Sakurai
Scheme 1. Titanium-mediated double-coupling and electroreductive coupling
of chromones.
Center for Research on Green Sustainable Chemistry
Graduate School of Engineering, Tottori University
4-101, Koyama-cho Minami, Tottori 680-8552, (Japan)
Supporting information for this article is available on the WWW
under http://dx.doi.org/10.1002/chem.2019xxxxx.
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10.1002/ejoc.201900519
European Journal of Organic Chemistry
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during workup. When R1 is methyl or phenyl group, protonation
at the 3-position in C occurs completely from the less hindered
side ( side) to produce 2,3-cis-isomer of 3.
Table 1. Electroreductive coupling of chromones 1a-d with benzophenones
2a-f.[a]
Scheme 2. Transformation of adducts.
Run
1
1
R1
H
R2
H
2
Ar2C=O
3
% Yield[b]
1a
1a
2a
2b
Ar = Ph
3a
3b
87
75
Results and Discussion
2
H
H
Ar = 4-FC6H4
Electroreductive
benzophenones
coupling
of
chromones
with
3
1a
H
H
2c
3c
52
The electroreduction of chromones 1a-d with benzophenones 2a-
f (2 equiv) was carried out in THF containing TMSCl (5 equiv)
according to our already reported method[3-6] and the results are
summarized in Table 1. In all cases, the adducts coupled at the
2-position of 1a-d with 2a-f were obtained as trimethylsilyl ethers
4
5
6
1a
1a
1a
H
H
H
H
H
H
2d
2e
2f
3d
3e
3f
64
94
55
3a-m in moderate to high yields.
It is noted that the
electroreductive coupling of 3-methylchromone (1b) and
isoflavone (1c) with 2a,b,d gave the adducts 3g-k as single
diastereomers (>99% selectivity by 1H NMR analysis) (runs 7-11).
In addition, the electroreduction of substituted isoflavones 1e-h
with benzophenone (2a) also gave the corresponding adducts 3n-
q in moderate yields with complete stereoselectivity (Table 2).
Of these adducts, the stereochemistry of 3i was confirmed to be
cis by X-ray crystallographic analysis. Therefore, the other
adducts 3g,h,j,k,n-q could be assumed to be cis-isomers. We
have already observed similar cis-stereoselectivity in the
7
8
1b
1b
Me
Me
H
H
2a
2b
Ar = Ph
cis-3g
cis-3h
75
61
Ar = 4-FC6H4
electroreductive
coupling
of
1-alkoxycarbonyl-3-
methoxycarbonylindoles,[4] 5-substituted 1,3-dimethyluracils,[5]
and 3-methylcoumarin[6] with aromatic ketones.
9
1b
Me
H
2d
cis-3i
76
When the electroreductive coupling of 1a with 4,4’-
dimethoxybenzophenone (2g) was carries out under the same
conditions as above, the desired cross-coupled product was not
obtained at all; hydrodimer of chromone (i) and 4-
(trimethylsilyl)chroman-2-one (ii) were formed in 35% (60:40 dr)
and 8% yields, respectively. Incidentally, the electroreduction of
chromone alone in the presence of TMSCl gave i (41%, 60:40 dr)
and ii (10%) as shown in Scheme 3. Since we already reported
CV data of benzophenones 2a-g,[6] we measured the CV of
chromones 1a-g under the same conditions to compare their first
reduction peaks (Table 3). These results revealed that 1a (-2.05
V vs SCE) is less reducible than 2a (-1.85 V) but slightly more
reducible than 2g (-2.08 V). Hence, the reaction mechanism of
the electroreductive coupling of chromones with benzophenones
can be presumed as illustrated in Scheme 4. Initially, carbanion
A is generated by the consecutive two-electron transfer to 2a and
O-silylation with TMSCl. The nucleophilic 1,4-addition of A to the
2-position in 1 and following O-silylation of resulting enolate anion
B give silyl enol ether C. The labile C is readily desilylated to 3
10
11
12
13
1c
1c
1d
1d
Ph
Ph
H
H
2a
2b
2a
2b
Ar = Ph
cis-3j
cis-3k
3l
64
54
69
64
H
Ar = 4-FC6H4
Ar = Ph
Me
Me
H
Ar = 4-FC6H4
3m
[a] Electroreduction was carried out in 0.3 M Bu4ClO4/THF using a Pt
cathode at a constant current of 0.2 A (400 C; 4 F/mol). [b] Isolated yields.
.
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Table 2. Electroreductive coupling of isoflavones 1e-h with 2a.
Run
1
1
X
X’
3
% Yield[a]
1e
1f
6-MeO
7-MeO
7-MeO
5,7-(MeO)2
H
cis-3n
cis-3o
cis-3p
cis-3q
71
61
55
56
2
H
3
1g
1h
MeO
MeO
Scheme 4. Presumed reaction mechanism of electroreductive coupling of
chromones 1 with benzophenones 2.
4
[a] Electroreduction was carried out in 0.3 M Bu4ClO4/THF using a Pt
Dehydrosiloxylation of 3
cathode at a constant current of 0.2 A (400 C; 4 F/mol). [b] Isolated yields.
Dehydrosiloxylation of the adducts (R2 = H), 3a-e and cis-3g-k,n-
q, was carried out by reflux in xylene containing a catalytic amount
of p-TsOH for 1-6
h
(Table 4).
In all cases, 4-
diarylmethylchromones 4 were obtained as the sole products in
good to excellent yields. These results show that initially formed
exo-alkenes by dehydrosiloxylation of 3 rapidly isomerized to
endo-alkenes 4 under the reflux conditions.
Desilylation of 3 with 1 M HCl/dioxane and subsequent
dehydration
Scheme 3. Electroreduction of 1a in the presence of TMSCl.
Table 3. Ep Values of 1a-h and 2a-f derived from CV at 25 ºC.
The trimethylsilyl ethers 3a-q were stirred in 1 M HCl aq and
dioxane (1:1) until almost all of 3a-q were consumed (Table 5).
From 3a-f, desilylated alcohols 5a-f were obtained after stirring at
25 ºC for 2-6 h in high yields (runs 1-6). From 3- and 4-substituted
adducts 3g-q, the corresponding alcohols 5g-q were obtained
after stirring at 50 ºC for 2-12 h in good to high yields (runs 7-17).
In particular, cis-5g-k and cis-5n-q were formed as the sole
products with retaining the stereochemistry (runs 7-11 and 14-17).
The stereostructures of cis-5g,i,o were confirmed by X-ray
crystallography. Dehydration of the resultant alcohols (R2 = H),
5a-e and cis-5g-k,n-q, with reflux in toluene containing a catalytic
amount of p-TsOH for 1-3 h afforded 4-diarylmethylchromones 4
in good to excellent yields (runs 1-5, 7-11, and 14-17). Strangely
enough, the hydration of 5f under the same conditions resulted in
a complex mixture (run 6).
1
Ep (V vs. SCE)[a}
−2.05
2
Ep (V vs. SCE)[a,b]
−1.85
1a
1b
1c
1d
1e
1f
2a
2b
2c
2d
2e
2f
−2.16
−1.85
−2.13
−1.78
−1.97
−1.79
−1.95
−1.76
Ring-opening of adducts 3 to 6 by successive treatment
with TBAF/THF and NaH, and subsequent recyclisation
of 6 to 7 or 8
−2.08
−1.38
1g
−2.14
2g
−2.08
The treatment of 3a with TBAF in THF at 25 ºC for 10 min gave a
mixture of the desilylated alcohol 5a and its ring-opening product
6a in 98% combined yield (5a:6a = 2:1~1:1). Therefore, the
reaction mixture was successively treated in situ with one molar
equivalent of NaH at 25 ºC for 30 min to obtain 6a as a sole
product. The other adducts 3b-d,f-i,l were treated under the
same conditions to give 6b-d,f-i,l as sole geometric isomers in
[a] 1st reduction peak in CV of 3 mM solution in 0.03 M Bu4NClO4/DMF
at a Pt cathode at 0.1 V/s. In THF, clear reduction peaks could not be
observed. [b] Reported data in ref. 6.
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10.1002/ejoc.201900519
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good to excellent yields (Table 6). Of these products, 6a,c,f were
confirmed to be E-form by X-ray diffraction. The other 6 could
also be estimated to be E-form. Next, we attempted the
recyclisation of 6. The dehydration of 6g,h (R1 = Me, R2 = H) in
refluxing toluene containing a catalytic amount of p-TsOH for 1 h
gave tetrasubstituted furans 7g,h, while that of 6a-f,i,l (R1 = H)
under the same conditions resulted in formation of complex
mixtures (Scheme 5). The adducts cis-3j,k,n-q derived from
isoflavones 1c,e-h were also transformed to the corresponding
ring-opening products 6. However, these compounds were
unstable and could not be isolated. Therefore, the crude ring-
opening products 6j,k,n-q were immediately subjected to
dehydration without isolation and the results are shown in Table
7. Tetraaryl-substituted furans 7j,k,n were obtained from cis-
3j,k,n (runs 1-3), whereas dihydrobenzofuran-3-ones 8o-q were
formed from cis-3o-q (runs 4-6). In later cases (runs 4-6), PPTS
gave better results than p-TsOH as an acid-catalyst for
dehydration.
Table 5. Desilylation of 3 with 1 M HCl aq/dioxane and subsequent
dehydration.
Ru
n
3
R1
R2
5
% Yield[a]
4
% Yield[a]
1
3a
H
H
5a
90
89
94
89
88
86
79
77
95
95
88
76
82
92
94
82
93
4a
4b
4c
4d
4e
4f
92
87
97
80
77
No[b]
70
98
87
71
82
−
2
3b
H
H
5b
3
3c
H
H
5c
4
3d
H
H
5d
Table 4. Detrimethylsiloxylation of 3 (R2 = H).
5
3e
H
H
5e
6
3f
H
H
5f
7
cis-3g
cis-3h
cis-3i
cis-3j
cis-3k
3l
Me
Me
Me
Ph
Ph
H
H
cis-5g
cis-5h
cis-5i
cis-5j
cis-5k
5l
4g
4h
4i
8
H
9
H
Run
1
3
R1
X
Time
1 h
6 h
6 h
4 h
3 h
3 h
1 h
3 h
1 h
1 h
1 h
1 h
2 h
1 h
4
% Yield[a]
89
10
11
12
13
14
15
16
17
H
4j
3a
H
H
4a
4b
4c
4d
4e
4g
4h
4i
H
4k
2
3b
H
H
98
Me
Me
H
3
3c
H
H
77
3m
H
5m
−
4
3d
H
H
92
cis-3n
cis-3o
cis-3p
cis-3q
Ph
Ph
An[b]
An[b]
cis-5n
cis-5o
cis-5p
cis-5q
4n
4o
4p
4q
93
82
82
84
5
3e
H
H
75
H
6
cis-3g
cis-3h
cis-3i
cis-3j
cis-3k
cis-3n
cis-3o
cis-3p
cis-3q
Me
H
81
H
7
Me
H
96
H
8
Me
H
98
[a] Isolated yields. [b] Not obtained. [c] An = 4-MeOC6H4.
9
Ph
H
4j
89
10
11
12
13
14
Ph
H
4k
4n
4o
4p
4q
90
Ph
6-MeO
7-MeO
7-MeO
5,7-(MeO)2
91
Ph
93
4-MeOC6H4
4-MeOC6H4
92
85
[a] Isolated yields.
Scheme 5. Recyclisation of 6g,h.
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The presumed reaction mechanism of the transformation of 3
to 6 and subsequent dehydration of 6 to 7 and 8 is exhibited in
Scheme 6. Desilylation of 3 with TBAF generates alkoxide anion
D, and then enolate anion E is formed by proton migration of D.
Ring-opening of E to F by retro 1,4-addition of phenoxide anion
and subsequent protonation give ring opening product 6. In the
recyclisation of 6, allyl cation G is formed by dehydration after
protonation to the tert-hydroxy group of 6. Intramolecular
nucleophilic addition of the carbonyl oxygen atom to the allyl
cation in G (path a), aryl migration in cyclized cation H, and
subsequent deprotonation of resultant carbocation I produce
tetrasubstituted furan 7. On the other hand, nucleophilic addition
of the phenolic hydroxyl oxygen atom to the allyl cation in G (path
b) and following deprotonation of cyclized cation J afford
dihydrobenzofuran-3-one 8. From the results shown in Scheme
5 and Table 6, it seems that 7-methoxy substitution in 3 (X = 7-
MeO) makes path b more favourable than path a, although the
reason is unclear at present.
Table 6. Desilylation of 3a-l with TBAF and subsequent ring-opening.
Run
1
3
R1
H
R2
H
6
% Yield[a]
98
3a
6a
6b
6c
6d
6f
2
3b
H
H
91
3
3c
H
H
68
4
3d
H
H
89
5
3f
H
H
98
6
cis-3g
cis-3h
cis-3i
3l
Me
Me
Me
H
H
6g
6h
6i
90
7
H
64
8
H
97
9
Me
6l
91
[a] Isolated yields.
Table 7. Desilylation, ring-opening, and recyclisation of cis-3j,k,n-q.
Run
1
3
X
Cat.
Product
7j
% Yield[a]
cis-3j
cis-3k
cis-3n
cis-3o
cis-3p
cis-3q
H
p-TsOH
p-TsOH
p-TsOH
PPTS
75
50
61
74
95
87
2
H
7k
Scheme 6. Presumed reaction mechanism of transformation of 3 to 6 and
dehydration of 6 to 7 and 8.
3
6-MeO
7-MeO
7-MeO
5,7-(MeO)2
7n
4
8o
Isomerization of cis-3 and subsequent desilylation to 5
The isomerization of cis-3g was carried out by treatment with cat.
DBU in THF at 50 ºC for 24 h to give an equilibrium diastereomeric
mixture of 3g (65:35 dr). Since the diastereomers of 3g could not
be separated, the mixture was subsequently desilylated with 1 M
HCl aq/dioxane (1:1) at 50 ºC for 2 h to give 5g (trans:cis = 65:35).
The other cis-isomers of 3h-k,n-q were isomerized and
desilylated to trans-alcohols 5h-k,n-q under the same conditions
5
PPTS
8p
6
PPTS
8q
[a] Isolated yields.
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10.1002/ejoc.201900519
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(Table 8). Of these, the stereoconfigurations of trans-5g,h,j were
unambiguously confirmed to be trans by X-ray crystallography.
The 1H NMR chemical shifts of 2-H and 3-H, and coupling
constants between 2-H and 3-H (J2,3) of cis- and trans-5g-k,n-q
are exhibited in Table 9. In 3-methyl substituted chromones 5g-i,
the J2,3 values for trans-isomers were larger (4.6-6.6 Hz) than
those for cis-ones (1.7-2.4 Hz). However, the J2,3 values for both
isomers were similar (2.3-3.4 Hz) in 3-aryl substituted chromones
5j,k,n-q. The chemical shifts of 3-H for cis-isomers were more
upfield (0.39-0.60 ppm) than those for trans-ones in all cases,
whereas the chemical shifts of 2-H for both isomers were very
close with differences within 0.10 ppm.
reaction of cis-5g (run 6). Unfortunately, the treatment of cis-5j
(R1 = Ph) with DDQ brought about 1d and 2a (70% each yields)
and the desired dehydrogenated product 9j could not be obtained
at all (run 8).
Table 9. 1H NMR chemical shifts of 2-H and 3-H, and coupling constants
(J2,3) of 2,3-cis- and trans-substituted chromones 5g-k,n-q.
cis
trans
3-H ()
2.85
2.83
2.65
4.03
4.03
4.01
3.97
3.92
3.83
5
2-H ()
5.33
5.23
5.24
5.64
5.54
5.59
5.66
5.64
5.60
3-H ()
2.33
2.31
2.05
3.59
3.56
3.56
3.54
3.50
3.44
J2,3 (Hz)
1.7
2-H ()
5.23
5.13
5.15
5.70
5.61
5.65
5.68
5.64
5.58
J2,3 (Hz)
4.6
5g
5h
5i
1.9
5.0
Table 8. Isomerization of cis-3 and subsequent desilylation with 1 M HCl.
2.4
6.6
5j
2.7
2.3
5k
5n
5o
5p
5q
2.7
3.4
2.7
2.4
2.7
2.4
Run
1
cis-3
R1
5
% Yield{a}
trans:cis[b]
65:35
66:34
70:30
95:5
2.8
2.6
cis-3g
cis-3h
cis-3i
cis-3j
cis-3k
cis-3n
cis-3o
cis-3p
Me
5g
5h
5i
86
89
88
69
64
65
80
87
2.7
2.6
2
Me
3
Me
4
Ph
5j
Table 10. Dehydrogenation of 5 (R2 = H).
5
Ph
5k
5n
5o
5p
95:5
6
Ph
94:6
7
Ph
90:10
92:8
8
4-MeOC6H4
9
cis-3q
4-MeOC6H4
5q
74
76:24
% Yield[a]
Run
5
R1
9
[a] Isolated yields. [b] Determined by 1H NMR analysis.
1
2
3
4
5
6
7
8
5a
H
9a
9b
9c
9d
9e
9g
9h
9j
90
5b
H
92
5c
H
50[b]
75
Dehydrogenation of 5
Dehydrogenation of 5 (R1 = H, Me; R2 = H) with DDQ in refluxing
5d
H
dioxane
in
the
presence
of
TMSCl
gave
2-
The
(diarylhydroxymethyl)chromones
9
(Table 10).
5e
H
91
corresponding 9a-e were obtained in good to excellent yields from
5a-e (R1 = H) (runs 1-5), although further dehydrogenated product
9d was formed as a by-product in the case of the oxidation of 5c
(run 3). The oxidation of 3a under the same conditions also gave
9a (84%) with a small amount of silyl ether of 9a (>5%). From
cis-5g and cis-5h (R1 = Me), the yields of 9g and 9h were
decreased, since benzophenones 2a (34%) and 2b (12%) were
also formed together with 1b by oxidative cleavage of cis-5g and
cis-5h, respectively (runs 6 and 7). The oxidation of trans-5g
gave the result (9g in 45% yield) substantially same as the
cis-5g{c}
cis-5h
cis-5j
Me
Me
Ph
46
60
No[d]
[a] Isolated yields. [b] 9d (24%) was formed as a by-product.
[c] trans-5g gave the same result. [d] Not obtained.
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10.1002/ejoc.201900519
European Journal of Organic Chemistry
FULL PAPER
7.08 (m, 2H), 7.21-7.34 (m, 8H), 7.44-7.53 (m, 3H), 7.87-7.91 (m, 1H). 13
C
Conclusions
NMR (125 MHz, CDCl3): δ = 2.0 (q), 37.7 (t), 80.2 (d), 82.0 (s), 117.8 (d),
121.2 (s), 121.7 (d), 126.7 (d), 127.1 (d), 127.2 (d), 127.3 (d), 127.8 (d),
128.1 (d), 128.2 (d), 136.1 (d), 136.1 (s), 144.1 (s), 144.2 (s), 160.8 (s),
192.9 (s). IR (ATR): 휈̃
= 1684, 1607 cm-1. HRMS (ESI+) calcd for
C25H27O3Si [M + H+] 403.1729, found 403.1722.
The electroreductive intermolecular coupling of chromones 1a-h
with benzophenones 2a-f in the presence of TMSCl in THF gave
the adducts reacted at the 2-position of 1a-h as TMS ethers 3a-q.
From 2-methylchromone (1b) and 2-arylchromones (Isoflavones)
1c,e-h, only 2,3-cis-adducts cis-3g-k,n-q were selectively
obtained. The detrimethylsiloxylation of 3a-e and cis-3g-k,n-q
2-(Bis(4-fluorophenyl)((trimethylsilyl)oxy)methyl)chroman-4-one
(3b): White solid (329 mg, 75%). Rf: 0.5 (hexanes/ethyl acetate, 10:1). Mp
148-149 ºC. 1H NMR (500 MHz, CDCl3): δ = −0.06 (s, 9H,), 2.33 (dd, 1H,
J = 1.9, 17.0 Hz), 2.69 (dd, 1H, J = 13.8, 17.0 Hz), 5.28 (dd, 1H, J = 1.9,
13.8 Hz), 6.95-7.09 (m, 6H), 7.25-7.29 (m, 2H), 7.39-7.44 (m, 2H), 7.50-
7.54 (m, 1H), 7.88-7.91 (m, 1H). 13C NMR (125 MHz, CDCl3): δ = 1.9 (s),
37.6 (t), 80.0 (d), 81.2 (s), 114.7 (d, JCCF = 21.6 Hz), 115.0 (d, JCCF = 21.9
Hz), 117.6 (d), 121.1 (s), 121.9 (d), 127.1 (d), 128.6 (d, JCCCF = 7.2 Hz),
129.8 (d, JCCCF = 7.8 Hz), 136.1 (s), 139.7 (s, JCCCCF = 2.7 Hz), 139.8 (s,
JCCCCF = 2.7 Hz), 160.5 (s), 161.9 (s, JCF = 247.1 Hz), 162.0 (s, JCF = 247.1
with
refluxing
in
cat.
p-TsOH/xylene
afforded
2-
diarylmethylchromones 4a-e,g-k,n-q. The treatment of 3a-q with
1 M HCl/dioxane gave the corresponding desilylated alcohols 5a-
q. The dehydration of 5a-e and cis-5g-k,n-q with refluxing in cat.
p-TsOH/toluene also afforded 4a-e,g-k,n-q. The successive
treatment of 3a-d,f,l and cis-3g-i with TBAF and NaH gave ring-
opening products 6a-d,f-i,l. The dehydration of 6g,h produced
tetrasubstituted furans 7g,h. The successive treatment of cis-
3j,k,n-q with TBAF and NaH, and the dehydration of the crude
resultant ring-opening products afforded tetraaryl-substituted
furans 7j,k,n and dihydrobenzofuran-3-ones 8o-q. The treatment
of cis-3g-k,n-q with DBU and following desilylation with 1 M
HCl/dioxane gave isomerized alcohols trans-5g-k,n-q. The
dehydrogenation of 5a-e and cis-5g,h with DDQ in dioxane
formed 2-(diarylhydroxymethyl)chromones 9a-e,g,h.
Hz), 192.3 (s). IR (ATR): 휈̃
= 1694, 1605 cm-1. HRMS (ESI+) calcd for
C25H25F2O3Si [M + H+] 439.1541, found 439.1531.
2-(5-((Trimethylsilyl)oxy)-10,11-dihydro-5H-dibenzo[a,d][7]annulen-
5-yl)chroman-4-one (3c): Colorless paste (223 mg, 52%). Rf: 0.35
(hexanes/ethyl acetate, 20:1). 1H NMR (500 MHz, CDCl3): δ = −0.14 (s,
9H), 2.17 (dd, 1H, J = 13.5, 16.6 Hz), 2.85-2.92 (m, 2H), 3.02 (dd, 1H, J =
11.3, 15.5 Hz), 3.15 (dd, 1H, J = 7.5, 15.5 Hz), 3.71 (dd, 1H, J = 11.3, 14.0
Hz), 5.02 (dd, 1H, J = 2.4, 13.2 Hz), 6.71-6.75 (m, 1H), 6.87-6.91 (m, 1H),
7.09-7.16 (m, 2H), 7.19-7.28 (m, 4H), 7.30-7.34 (m, 1H), 7.73-7.76 (m, 1H),
7.77-7.80 (m, 1H), 7.85-7.89 (m, 1H). 13C NMR (125 MHz, CDCl3): δ = 1.8
(q), 36.4 (t), 36.8 (t), 38.9 (t), 84.4 (s), 87.5 (d), 117.6 (d), 120.8 (s), 120.9
(d), 124.9 (d), 126.0 (d), 126.4 (d), 127.6 (d), 128.0 (d), 129.4 (d), 130.1
(d), 131.4 (d), 131.7 (d), 135.4 (d), 138.6 (s), 141.8 (s), 143.0 (s), 160.9 (s),
Experimental Section
General methods. Column chromatography was performed on silica gel
60. THF was freshly distilled from sodium benzophenone ketyl radical.
DMF, TMSCl, and TEA were distilled from CaH2. 1H NMR (500 MHz) and
13C NMR (125 MHz) spectra were measured on a JEOL JNM-ECP500
spectrometer in the solvents indicated; chemical shifts (δ) are given in ppm
relative to tetramethylsilane (TMS) as an internal standard. IR spectra
193.0 (s). IR (ATR): 휈̃
= 1690, 1605 cm-1. HRMS (ESI+) calcd for
C27H29O3Si [M + H+] 429.1886, found 429.1875.
2-(5-((Trimethylsilyl)oxy)-5H-dibenzo[a,d][7]annulen-5-yl)chroman-4-
one (3d): White solid (273 mg, 64%). Rf: 0.25 (hexanes/ethyl acetate,
20:1). Mp 230-231 ºC. 1H NMR (500 MHz, CDCl3): δ = 0.38 (s, 9H), 1.72
(dd, 1H, J = 4.3, 17.8 Hz), 2.70 (dd, 1H, J = 14.8, 17.8 Hz), 5.62 (dd, 1H,
J = 4.3, 14.8 Hz), 6.68-6.72 (m, 1H), 6.90-6.97 (m, 2H), 7.02 (d, 1H, J =
11.6 Hz), 7.27-7.39 (m, 5H), 7.43-7.51 (m, 2H), 7.77-7.81 (m, 1H), 7.81-
7.85 (m, 1H), 7.93-7.97 (m, 1H). 13C NMR (125 MHz, CDCl3): δ = 3.8 (q),
37.8 (t), 75.1 (d), 83.3 (s), 113.1 (d), 120.7 (s), 121.4 (d), 124.9 (d), 126.0
(d), 126.6 (d), 126.9 (d), 127.0 (d), 128.3 (d), 129.1 (d), 129.2 (d), 129.4
(d), 131.3 (d), 131.4 (s), 131.8 (d), 131.9 (s), 136.0 (d), 138.6 (s), 139.5 (s),
were recorded on
a Shimadzu IRAffinity-1 infrared spectrometer;
wavenumbers (휈
̃
Scientific Exactive FTMS spectrometer. Melting points were uncorrected.
Starting materials. Chromones 1a,[2f] 1b,[7] 1c,[2f] and isoflavones 1d,[7]
1e,[9] 1f,[9] 1g,[10] 1h,[11] were prepared by reported methods.
Typical procedure of electroreductive coupling. A 0.3 M solution of
Bu4NClO4 in THF (15 mL) was placed in the cathodic chamber of a divided
cell (40 mL beaker, 3 cm diameter, 6 cm height) equipped with a platinum
cathode (5 × 5 cm2), a platinum anode (2 × 1 cm2), and a ceramic
cylindrical diaphragm (1.5 cm diameter). A 0.3 M solution of Et4NOTs in
DMF (4 mL) was placed in the anodic chamber (inside the diaphragm).
Chromone (1a) (146 mg, 1.0 mmol), benzophenone (2a) (368 mg, 2.0
mmol), TMSCl (0.64 mL, 5.0 mmol), and TEA (0.70 mL, 5.0 mmol) were
added to the cathodic chamber. After 400 C (4.0 F/mol) of electricity was
passed at a constant current of 200 mA at 25 ºC under nitrogen
atmosphere, the catholyte was evaporated in vacuo. The residue was
dissolved in diethyl ether (20 mL) and insoluble solid was filtered off. After
removal of the solvent in vacuo, the residue was purified by column
chromatography on silica gel (hexanes-EtOAc) to give 3a (350 mg, 0.869
mmol) in 87% yield.
160.9 (s), 192.7 (s). IR (ATR): 휈̃
= 1686, 1605 cm-1. HRMS (ESI+) calcd
for C27H27O3Si [M + H+] 427.1729, found 427.1716.
2-(9-((Trimethylsilyl)oxy)-9H-xanthen-9-yl)chroman-4-one (3e): White
solid (392 mg, 94%). Rf: 0.3 (hexanes/ethyl acetate, 20:1). Mp 167-168 ºC.
1H NMR (500 MHz, CDCl3): δ = −0.13 (s, 9H), 2.47 (dd, 1H, J = 13.2, 16.6
Hz), 2.58 (dd, 1H, J = 3.0, 16.6 Hz), 4.63 (dd, 1H, J = 3.0, 13.2 Hz), 6.85-
6.93 (m, 2H), 7.13-7.19 (m, 4H), 7.33-7.41 (m, 3H), 7.55-7.59 (m, 1H),
7.71-7.75 (m, 1H), 7.77-7.80 (m, 1H). 13C NMR (125 MHz, CDCl3): δ = 1.7
(q), 38.0 (t), 72.6 (s), 85.1 (d), 116.0 (d), 116.5 (d), 118.0 (d), 120.8 (s),
121.1 (d), 122.6 (s), 122.8 (d), 122.9 (d), 123.3 (s), 126.5 (d), 128.1 (d),
128.8 (d), 129.5 (d), 129.8 (d), 135.7 (d), 150.4 (s), 150.6 (s), 161.1 (s),
192.3 (s). IR (ATR): 휈̃
= 1690, 1607, 1576 cm-1. HRMS (ESI+) calcd for
C25H25O4Si [M + H+] 417.1522, found 417.1510.
2-(9-((Trimethylsilyl)oxy)-9H-fluoren-9-yl)chroman-4-one (3f): Yellow
paste (220 mg, 55%). Rf: 0.3 (hexanes/ethyl acetate, 20:1). 1H NMR (500
MHz, CDCl3): δ = −0.28 (s, 9H), 2.45 (dd, 1H, J = 3.3, 16.8 Hz), 2.54 (dd,
1H, J = 12.7, 16.8 Hz), 4.72 (dd, 1H, J = 3.3, 12.7 Hz), 6.93-6.97 (m, 1H),
7.03-7.06 (m, 1H), 7.27-7.33 (m, 2H), 7.38-7.47 (m, 3H), 7.54-7.57 (m, 1H),
2-(Diphenyl((trimethylsilyl)oxy)methyl)chroman-4-one (3a): White
solid (350 mg, 87%). Rf: 0.5 (hexanes/ethyl acetate, 10:1). Mp 205-207 ºC.
1H NMR (500 MHz, CDCl3): δ = −0.06 (s, 9H), 2.29 (dd, 1H, J = 2.4, 17.2
Hz), 2.76 (dd, 1H, J = 13.9, 17.2 Hz), 5.36 (dd, 1H, J = 2.4, 13.9 Hz), 6.99-
This article is protected by copyright. All rights reserved.

10.1002/ejoc.201900519
European Journal of Organic Chemistry
FULL PAPER
7.63-7.66 (m, 2H), 7.69-7.71 (m, 1H), 7.78-7.81 (m, 1H). 13C NMR (125
MHz, CDCl3): δ = 1.2 (q), 37.8 (t), 82.6 (d), 84.8 (s), 117.9 (d), 120.0 (d),
120.1 (d), 120.98 (d), 121.00 (d), 125.3 (d), 126.51 (d), 126.53 (d), 127.6
(d), 127.7 (d), 129.4 (d), 129.5 (d), 135.7 (d), 139.9 (s), 140.4 (s), 144.9
128.1 (d), 128.7 (d), 129.5 (d), 130.0 (d, JCCCF = 8.4 Hz), 130.4 (d, JCCCF
7.8 Hz), 133.8 (s), 136.2 (d), 138.9 (s, JCCCCF = 2.4 Hz), 140.5 (s, JCCCCF
=
=
2.4 Hz), 160.7 (s), 161.6 (s, JCF = 245.9 Hz), 162.2 (s, JCF = 248.3 Hz),
191.4 (s). IR (ATR): 휈̃
= 1690, 1605, 1504 cm−1. HRMS (ESI+) calcd for
(s), 145.6 (s), 161.7 (s), 192.4 (s). IR (ATR): 휈
̃
= 1690, 1605 cm-1. HRMS
C31H29F2O3Si [M + H+] 515.1854, found 515.1837.
(ESI+) calcd for C25H25O3Si [M + H+] 401.1573, found 401.1562.
2-(Diphenyl((trimethylsilyl)oxy)methyl)-2-methylchroman-4-one (3l):
White solid (287 mg, 69%). Rf: 0.35 (hexanes/ethyl acetate, 20:1). Mp 145-
147 ºC. 1H NMR (500 MHz, CDCl3): δ = −0.17 (brs, 9H), 1.56 (brs, 3H),
2.26 (brs, 1H) 3.39 (brs, 1H), 6.99-7.04 (m, 1H), 7.05-7.09 (m, 1H), 7.24-
(2R*,3R*)-2-(Diphenyl((trimethylsilyl)oxy)methyl)-3-methylchroman-
4-one (cis-3g): Colorless paste (312 mg, 75%). Rf: 0.35 (hexanes/ethyl
acetate, 20:1). 1H NMR (500 MHz, CDCl3): δ = −0.04 (s, 9H), 1.11 (d, 3H,
J = 7.5 Hz), 2.18-2.24 (m, 1H), 5.27 (d, 1H, J = 2.3 Hz), 7.08-714 (m, 2H),
7.22-7.31 (m, 8H), 7.34-7.39 (m, 2H), 7.54-7.58 (m, 1H), 7.91-7.94 (m, 1H).
13C NMR (125 MHz, CDCl3): δ = 2.0 (q), 11.5 (q), 42.4 (d), 81.3 (d), 82.1
(s), 117.3 (d), 119.8 (s), 121.8 (d), 125.9 (d), 127.1 (d), 127.4 (d), 127.9
(d), 128.0 (d), 128.2 (d), 128.4 (d), 135.9 (d), 144.9 (s), 145.8 (s), 160.8
7.32 (m, 6H), 7.40-7.47 (m, 2H), 7.50-7.66 (m, 3H), 7.85-7.90 (m, 1H). 13
C
NMR (125 MHz, CDCl3): δ = 1.7 (q), 20.5 (q), 44.7 (t), 86.1 (brs), 87.0 (brs),
118.2 (d), 120.6 (s), 120.8 (d), 126.4 (d), 127.2 (d), 127.3 (d), 127.37 (d),
127.41 (d), 129.3 (brd), 130.6 (brd), 136.2 (d), 144.4 (s), 159.2 (s), 192.7
(s). IR (ATR): 휈̃
= 1680, 1603 cm-1. HRMS (ESI+) calcd for C26H29O3Si [M
+ H+] 417.1886, found 417.1872.
(s), 197.0 (s). IR (ATR): 휈
̃
= 1690, 1605 cm-1. HRMS (ESI+) calcd for
C26H29O3Si [M + H+] 417.1886, found 417.1875.
2-(Bis(4-fluorophenyl)((trimethylsilyl)oxy)methyl)-2-methylchroman-
4-one (3m): White solid (290 mg, 64%). Rf: 0.3 (hexanes/ethyl acetate,
20:1). Mp 166-167 ºC. 1H NMR (500 MHz, CDCl3): δ = −0.16 (s, 9H), 1.53
(brs, 3H), 2.24 (brs, 1H), 3.33 (brd, 1H, J = 16.0 Hz), 6.95-7.07 (m, 6H),
7.35-7.43 (m, 2H), 7.50-7.64 (m, 3H), 7.85-7.91 (m, 1H). 13C NMR (125
MHz, CDCl3): δ = 1.8 (q), 20.5 (q), 44.5 (t), 85.5 (s), 86.9 (s), 114.2 (d, JCCF
= 19.2 Hz), 114.3 (d, JCCF = 20.4 Hz), 118.1 (d), 120.5 (s), 121.1 (d), 126.5
(d), 131.1 (brd), 132.3 (brd), 136.3 (d), 139.8 (brs), 140.0 (s, JCCCCF = 2.7
Hz), 159.0 (s), 161.98 (s, JCF = 248.3 Hz), 162.01 (s, JCF = 248.3 Hz), 192.3
(2R*,3R*)-2-(Bis(4-fluorophenyl)((trimethylsilyl)oxy)methyl)-3-
methylchroman-4-one (cis-3h): Colorless paste (276 mg, 61%). Rf: 0.25
(hexanes/ethyl acetate, 20:1). 1H NMR (500 MHz, CDCl3): δ = −0.03 (s,
9H), 1.06 (d, 3H, J = 7.5 Hz), 2.24 (q, 1H, J = 7.5 Hz), 5.18 (s, 1H), 6.95-
7.03 (m, 4H), 7.09-7.13 (m, 2H), 7.23-7.28 (m, 2H), 7.33-7.37 (m, 2H),
7.54-7.59 (m, 1H), 7.91-7.94 (m, 1H). 13C NMR (125 MHz, CDCl3): δ = 2.0
(q), 11.3 (q), 42.3 (d), 81.4 (s), 81.5 (d), 114.8 (d, JCCF = 20.7 Hz), 115.1
(d, JCCF = 21.3 Hz), 117.2 (d), 119.8 (s), 122.1 (d), 127.9 (d, JCCCF = 7.5
Hz), 128.1 (d), 130.2 (d, JCCCF = 7.5 Hz), 135.9 (d), 140.6 (s, JCCCCF = 3.6
Hz), 141.5 (s, JCCCCF = 3.3 Hz), 160.6 (s), 161.9 (s, JCF = 247.1 Hz), 162.0
(s). IR (ATR): 휈̃
= 1690, 1603 cm-1. HRMS (ESI+) calcd for C26H27F2O3Si
[M + H+] 453.1698, found 453.1686.
(s, JCF = 247.1 Hz), 196.4 (s). IR (ATR): 휈̃
= 1690, 1603 cm-1. HRMS (ESI+)
calcd for C26H27F2O3Si [M + H+] 453.1698, found 453.1685.
(2R*,3R*)-2-(Diphenyl((trimethylsilyl)oxy)methyl)-6-methoxy-3-
phenylchroman-4-one (cis-3n): Colorless paste (361 mg, 71%). Rf: 0.5
(hexanes/ethyl acetate, 5:1). 1H NMR (500 MHz, CDCl3): δ = −0.21 (s, 9H),
3.74 (d, 1H, J = 2.9 Hz), 3.80 (s, 3H), 5.48 (d, 1H, J = 2.9 Hz), 6.77-6.80
(m, 2H), 6.91-6.96 (m, 2H), 6.98-7.04 (m, 4H), 7.15-7.18 (m, 1H), 7.19-
7.25 (m, 5H), 7.28-7.32 (m, 3H), 7.35-7.37 (m, 1H). 13C NMR (125 MHz,
CDCl3): δ = 1.8 (q), 53.4 (d), 55.6 (q), 81.2 (s), 82.9 (d), 108.7 (d), 118.9
(d), 120.4 (s), 125.3 (d), 126.5 (d), 126.76 (d), 126.79 (d), 127.5 (d), 127.7
(d), 127.8 (d), 127.9 (d), 128.8 (d), 129.6 (d), 134.1 (s), 143.8 (s), 144.8
(2R*,3R*)-3-Methyl-2-(5-((trimethylsilyl)oxy)-5H-
dibenzo[a,d][7]annulen-5-yl)chroman-4-one (cis-3i): White solid (335
mg, 76%). Rf: 0.2 (hexanes/ethyl acetate, 20:1). Mp 198-199 ºC. 1H NMR
(500 MHz, CDCl3): δ = 0.47 (s, 9H), 0.85 (d, 3H, J = 7.5 Hz), 2.18-2.24 (m,
1H), 5.36 (d, 1H, J = 2.9 Hz), 6.76-6.80 (m, 1H), 6.93-7.06 (m, 3H), 7.23-
7.38 (m, 5H), 7.40-7.46 (m, 2H), 7.73-7.77 (m, 1H), 7.78-7.82 (m, 1H),
7.98-8.01 (m, 1H). 13C NMR (125 MHz, CDCl3): δ = 4.4 (q), 10.9 (q), 43.1
(d), 79.3 (d), 83.7 (s), 117.5 (d), 119.6 (s), 121.3 (d), 124.8 (d), 125.6 (d),
126.5 (d), 126.8 (d), 127.6 (d), 127.9 (d), 128.8 (d), 129.0 (d), 129.1 (d),
131.6 (d), 131.9 (s), 132.1 (s), 132.3 (d), 135.4 (d), 140.3 (s), 140.7 (s),
(s), 154.6 (s), 155.6 (s), 191.8 (s). IR (ATR): 휈̃
= 1686, 1616 cm−1. HRMS
(ESI+) calcd for C32H33O4Si [M + H+] 509.2148, found 509.2136.
160.9 (s), 196.4 (s). IR (ATR): 휈̃
= 1688, 1603 cm-1. HRMS (ESI+) calcd
for C28H29O3Si [M + H+] 441.1886, found 441.1875.
(2R*,3R*)-2-(Diphenyl((trimethylsilyl)oxy)methyl)-7-methoxy-3-
phenylchroman-4-one (cis-3o): White solid (310 mg, 61%). Rf: 0.25
(hexanes/ethyl acetate, 10:1). Mp 90-92 °C. 1H NMR (500 MHz, CDCl3): δ
= −0.20 (s, 9H), 3.72 (d, 1H, J = 2.9 Hz), 3.93 (s, 3H), 5.54 (d, 1H, J = 2.9
Hz), 6.65 (d, 1H, J = 2.3 Hz), 6.69 (dd, 1H, J = 2.3, 8.7 Hz), 6.75-6.78 (m,
2H), 6.90-6.94 (m, 2H), 6.97-7.05 (m, 4H), 7.20-7.24 (m, 4H), 7.29-7.32
(m, 3H), 7.88 (d, 1H, J = 8.7 Hz). 13C NMR (125 MHz, CDCl3): δ = 1.9 (q),
53.5 (d), 55.7 (q), 81.2 (s), 83.0 (d), 100.9 (d), 110.4 (d), 114.2 (s), 126.5
(d), 126.76 (d), 126.81 (d), 127.6 (d), 127.86 (d), 127.88 (d), 128.8 (d),
129.6 (d), 130.3 (d), 134.4 (s), 143.8 (s), 144.8 (s), 162.9 (s), 166.1 (s),
(2R*,3R*)-2-(Diphenyl((trimethylsilyl)oxy)methyl)-3-phenylchroman-
4-one (cis-3j): Colorless paste (306 mg, 64%). Rf: 0.3 (hexanes/ethyl
acetate, 20:1). IR (ATR): 휈̃
= 1690, 1605 cm-1. 1H NMR (500 MHz, CDCl3):
δ = −0.21 (s, 9H), 3.76 (d, 1H, J = 2.9 Hz), 5.53 (d, 1H, J = 2.9 Hz) 6.75-
6.81 (m, 2H), 6.91-6.96 (m, 2H), 6.98-7.06 (m, 4H), 7.10-7.14 (m, 1H),
7.19-7.33 (m, 8H), 7.59-7.64 (m, 1H), 7.93-7.97 (m, 1H). 13C NMR (125
MHz, CDCl3): δ = 1.9 (q), 53.7 (d), 81.3 (s), 82.9 (d), 117.7 (d), 120.7 (s),
122.3 (d), 126.6 (d), 126.9 (d), 127.6 (d), 127.88 (d), 127.93 (d), 128.0 (d),
128.7 (d), 128.9 (d), 129.7 (d), 134.1 (s), 136.2 (d), 143.9 (s), 144.8 (s),
190.8 (s). IR (ATR): 휈̃
= 1676, 1607, 1570 cm−1. HRMS (ESI+) calcd for
C32H33O4Si [M + H+] 509.2148, found 509.2134.
161.1 (s), 192.0 (s). IR (ATR): 휈̃
= 1690, 1605 cm-1. HRMS (ESI+) calcd
for C31H31O3Si [M + H+] 479.2042, found 479.2033.
(2R*,3R*)-2-(Diphenyl((trimethylsilyl)oxy)methyl)-7-methoxy-3-(4-
methoxyphenyl)chroman-4-one (cis-3p): White solid (296 mg, 55%). Rf:
0.4 (hexanes/ethyl acetate, 5:1). Mp 208-210 °C. 1H NMR (500 MHz,
CDCl3): δ = −0.19 (s, 9H), 3.68 (s, 3H), 3.70 (d, 1H, J = 2.9 Hz), 3.92 (s,
3H), 5.52 (d, 1H, J = 2.9 Hz), 6.44-6.49 (m, 2H), 6.63-6.64 (m, 1H), 6.66-
6.70 (m, 3H), 6.99-7.06 (m, 3H), 7.20-7.23 (m, 4H), 7.28-7.32 (m, 3H),
7.87-7.89 (m, 1H). 13C NMR (125 MHz, CDCl3): δ = 1.9 (q), 52.6 (d), 55.1
(q), 55.7 (q), 81.1 (s), 82.8 (d), 100.8 (d), 110.4 (d), 113.5 (d), 114.2 (s),
126.6 (d), 126.8 (d), 127.6 (d), 127.9 (d), 128.0 (d), 128.8 (d), 130.3 (d),
130.6 (d), 143.9 (s), 144.9 (s), 158.2 (s), 162.9 (s), 166.1 (s), 191.1 (s). IR
(2R*,3R*)-2-(Bis(4-fluorophenyl)((trimethylsilyl)oxy)methyl)-3-
phenylchroman-4-one (cis-3k): Colorless paste (278 mg, 54%). Rf: 0.3
(hexanes/ethyl acetate, 20:1). 1H NMR (500 MHz, CDCl3): δ = −0.14 (s,
9H), 3.92 (d, 1H, J = 2.9 Hz), 6.47 (d, 1H, J = 2.9 Hz), 6.58-6.63 (m, 2H),
6.73-6.76 (m, 2H), 6.88-6.93 (m, 2H), 6.97-7.02 (m, 3H), 7.11-7.16 (m, 3H),
7.17-7.22 (m, 3H), 7.59-7.63 (m, 1H), 7.93-7.95 (m, 1H). 13C NMR (125
MHz, CDCl3): δ = 1.9 (q), 53.6 (d), 80.3 (s), 82.3 (d), 113.4 (d, JCCF = 20.4
Hz), 114.8 (d, JCCF = 21.0 Hz), 117.6 (d), 120.4 (s), 122.5 (d), 126.7 (d),
This article is protected by copyright. All rights reserved.

10.1002/ejoc.201900519
European Journal of Organic Chemistry
FULL PAPER
(ATR): 휈
̃
= 1680, 1672, 1607, 1584, 1570, 1512 cm−1. HRMS (ESI+) calcd
(m, 2H), 5.16 (s, 1H), 5.94 (s, 1H), 7.14-7.19 (m, 2H), 7.19-7.28 (m, 5H),
7.31-7.36 (m, 3H), 7.54-7.59 (m, 1H), 8.12-8.15 (m, 1H). 13C NMR (125
MHz, CDCl3): δ = 32.1 (t), 57.8 (d), 111.2 (d), 118.0 (d), 123.3 (s), 124.9
(d), 125.4 (d), 126.4 (d), 128.1 (d), 130.6 (d), 131.7 (d), 133.4 (d), 135.4
for C33H35O5Si [M + H+] 539.2254, found 539.2239.
(2R*,3R*)-2-(Diphenyl((trimethylsilyl)oxy)methyl)-5,7-dimethoxy-3-(4-
methoxyphenyl)chroman-4-one (cis-3q): Colorless paste (318 mg,
56%). Rf: 0.35 (hexanes/ethyl acetate, 1:1). 1H NMR (500 MHz, CDCl3): δ
= −0.19 (s, 9H), 3.62 (d, 1H, J = 2.9 Hz), 3.68 (s, 3H), 3.83 (s, 3H), 3.91 (s,
3H), 5.48 (d, 1H, J = 2.9 Hz), 6.14 (d, 1H, J = 2.3 Hz), 6.28 (d, 1H, J = 2.3
Hz), 6.42-6.46 (m, 2H), 6.67-6.71 (m, 2H), 6.96-7.06 (m, 3H), 7.16-7.24 (m,
4H), 7.25-7.32 (m, 3H). 13C NMR (125 MHz, CDCl3): δ = 1.7 (q), 53.8 (d),
54.9 (q), 55.4 (q), 55.8 (q), 80.8 (s), 81.8 (d), 93.0 (d), 93.1 (d), 104.7 (s),
113.1 (d), 126.4 (d), 126.6 (d), 126.7 (s), 127.3 (d), 127.66 (d), 127.71 (d),
128.6 (d), 130.5 (d), 143.8 (s), 144.8 (s), 157.9 (s), 163.1 (s), 164.1 (s),
(s), 139.8 (s), 156,1 (s), 170.5 (s), 178.2 (s). IR (ATR): 휈̃
= 1643, 1607 cm-
1. HRMS (ESI+) calcd for C24H19O2 [M + H+] 339.1385, found 339.1378.
2-(5H-Dibenzo[a,d][7]annulen-5-yl)-4H-chromen-4-one (4d): White
solid (126 mg, 92%). Rf: 0.2 (hexanes/ethyl acetate, 5:1). Mp 207-209 ºC.
1H NMR (500 MHz, CDCl3): δ = 5.36 (d, 1H, J = 1.5 Hz), 5.69 (d, 1H, J =
1.5 Hz), 6.85 (s, 2H), 7.08-7.10 (m, 1H), 7.28-7.32 (m, 1H), 7.34-7.39 (m,
4H), 7.41-7.45 (m, 2H), 7.46-7.53 (m, 3H), 8.07-8.09 (m, 1H). 13C NMR
(125 MHz, CDCl3): δ = 57.1 (d), 110.2 (d), 117.8 (d), 123.3 (s), 124.8 (d),
125.3 (d), 127.6 (d), 128.9 (d), 129.6 (d), 130.3 (d), 130.7 (d), 133.2 (s),
165.8 (s), 189.5 (s). IR (ATR): 휈̃
= 1676, 1605, 1570, 1510 cm−1. HRMS
(ESI+) calcd for C34H37O6Si [M + H+] 569.2359, found 569.2345.
134.5 (s), 135.5 (s), 156.0 (s), 167.5 (s), 178.1 (s). IR (ATR): 휈̃
= 1639 cm-
1. HRMS (ESI+) calcd for C24H17O2 [M + H+] 337.1229, found 337.1224.
[2,2'-Bichromane]-4,4'-dione (i: 67:33 diastereomeric mixture): White
solid (60 mg, 41%). Rf: 0.5, 0.55 (hexanes/ethyl acetate, 2:1). 1H NMR
(500 MHz, CDCl3): δ = 2.79 (dd, 1.33H, J = 2.9, 17.0 Hz), 2.96-3.00 (m,
1.33H), 3.29 (dd, 1.33H, J = 13.2, 17.0 Hz), 4.64-4.69 (m, 1.33H), 4.70-
4.76 (m, 0.67 H), 7.00-7.10 (m, 4H), 7.49-7.55 (m, 2H), 7.90-7.95 (m, 2H).
13C NMR (125 MHz, CDCl3): δ = major: 38.9 (t), 77.5 (d), 117.92 (d), 120.8
(s), 121.9 (d), 127.97 (s), 136.3 (d), 160.7 (s), 191.4 (s), minor: 38.8 (t),
77.8 (d), 117.94 (d), 120.9 (s), 122.0 (d), 127.02 (s), 136.4 (d), 160.5 (s),
2-(9H-Xanthen-9-yl)-4H-chromen-4-one (4e): Yellow solid (122 mg,
75%). Rf: 0.3 (hexanes/ethyl acetate, 5:1). Mp 168-170 ºC. 1H NMR (500
MHz, CDCl3): δ = 5.23 (s, 1H,), 6.07 (s, 1H), 7.08-7.12 (m, 2H), 7.18-7.21
(m, 2H), 7.30-7.38 (m, 6H), 7.57-7.61 (m, 1H), 8.10-8.13 (m, 1H). 13C NMR
(125 MHz, CDCl3): δ = 43.7 (d), 109.8 (d), 117.0 (d), 117.9 (d), 118.8 (s),
123.5 (d), 125.0 (d), 125.5 (d), 129.1 (d), 129.2 (d), 133.5 (d), 151.6 (s),
156.3 (s), 169.2 (s), 178.3 (s). IR (ATR): 휈̃
= 1647, 1603 cm-1. HRMS
190.8 (s). IR (ATR): 휈
̃
= 1678, 1601, 1576 cm−1. HRMS (ESI+) calcd for
(ESI+) calcd for C22H15O3 [M + H+] 327.1021, found 327.1015.
C18H15O4 [M + H+] 295.0970, found 295.0963.
2-Benzhydryl-3-methyl-4H-chromen-4-one (4g): White solid (132 mg,
81%). Rf: 0.35 (hexanes/ethyl acetate, 5:1). Mp 185-186 ºC. 1H NMR (500
MHz, CDCl3): δ = 2.20 (s, 3H), 5.70 (s, 1H), 7.24-7.37 (m, 12H), 7.55-7.60
(m, 1H), 8.19-8.22 (m, 1H). 13C NMR (125 MHz, CDCl3): δ = 9.9 (q), 52.8
(d), 117.7 (d), 117.9 (s), 122.4 (s), 124.7 (d), 125.8 (d), 127.2 (d), 128.6
(d), 129.0 (d), 133.1 (d), 139.3 (s), 155.7 (s), 163.4 (s), 178.3 (s). IR (ATR):
2-(Trimethylsilyl)chroman-4-one (ii): Colorless paste (22 mg, 10%). Rf:
0.55 (hexanes/ethyl acetate, 10:1). 1H NMR (500 MHz, CDCl3): δ = 0.17
(s, 9H), 2.53-2.58 (m, 1H), 2.78-2.85 (m, 1H), 4.22-4.27 (m, 1H), 6.93-6.99
(m, 2H), 7.41-7.46 (m, 1H), 7.86-7.89 (m, 1H). 13C NMR (125 MHz, CDCl3):
δ = −4.3 (q), 38.3 (t), 72.5 (d), 117.8 (d), 120.7 (d), 121.2 (s), 124.1 (d),
135.5 (d), 163.7 (s), 192.7 (s). IR (ATR): 휈
̃
= 1690, 1605, 1574 cm−1. HRMS
휈̃
= 1624, 1609, 1599 cm-1. HRMS (ESI+) calcd for C23H19O2 [M + H+]
(ESI+) calcd for C12H17O2Si [M + H+] 221.0998, found 221.0994.
327.1385, found 327.1379.
Dehydrosiloxylation of 3. A solution of 3a (201 mg, 0.50 mmol) and p-
TsOH (10 mg) in xylene (10 mL) was refluxed using Dean-Stark apparatus
under nitrogen atmosphere for 1 h. After the solvent was removed in vacuo,
the residue was purified by column chromatography on silica gel (hexanes-
EtOAc) to give 4a (139 mg, 0.446 mmol) in 89% yield.
2-(Bis(4-fluorophenyl)methyl)-3-methyl-4H-chromen-4-one
(4h):
White solid (174 mg, 96%). Rf: 0.35 (hexanes/ethyl acetate, 5:1). Mp 154-
156 ºC. 1H NMR (500 MHz, CDCl3): δ = 2.18 (s, 3H), 5.65 (s, 1H), 7.00-
7.06 (m, 4H), 7.18-7.23 (m, 4H), 7.25-7.28 (m, 1H), 7.34-7.38 (m, 1H),
7.57-7.61 (m, 1H), 8.18-8.22 (m, 1H). 13C NMR (125 MHz, CDCl3): δ = 9.8
(q), 51.3 (d), 115.6 (d, JCCF = 21.6 Hz), 117.6 (d), 118.0 (s), 122.5 (s), 124.9
(d), 125.9 (d), 130.4 (d, JCCCF = 8.4 Hz), 133.3 (d), 135.0 (s, JCCCCF = 3.6
Hz), 155.6 (s), 162.0 (s, JCF = 246.5 Hz), 162.8 (s), 178.2 (s). IR (ATR): 휈
= 1632, 1605 cm-1. HRMS (ESI+) calcd for C23H17F2O2 [M + H+] 363.1197,
found 363.1190.
2-Benzhydryl-4H-chromen-4-one (4a): Yellow solid (139 mg, 89%). Rf:
0.35 (hexanes/ethyl acetate, 5:1). Mp 153-154 ºC. 1H NMR (500 MHz,
CDCl3): δ = 5.38 (s, 1H), 6.10 (s, 1H), 7.17-7.42 (m, 12H), 7.59-7.66 (m,
1H), 8.15-8.21 (m, 1H). 13C NMR (125 MHz, CDCl3): δ = 55.9 (d), 112.4
(d), 118.0 (d), 123.6 (s), 125.0 (d), 125.6 (d), 127.4 (d), 128.7 (d), 128.9
̃
(d), 133.6 (d), 138.8 (d), 156.4 (s), 169.8 (s), 178.3 (s). IR (ATR): 휈
̃
= 1651,
2-(5H-Dibenzo[a,d][7]annulen-5-yl)-3-methyl-4H-chromen-4-one (4i):
White solid (172 mg, 98%). Rf: 0.25 (hexanes/ethyl acetate, 5:1). Mp 188-
189 ºC. 1H NMR (500 MHz, CDCl3): δ = 1.82 (s, 3H), 5.53 (s, 1H), 6.91 (s,
2H), 7.04-7.08 (m, 1H), 7.26-7.33 (m, 3H), 7.34-7.40 (m, 4H), 7.47-7.53
(m, 3H), 8.09-8.13 (m, 1H). 13C NMR (125 MHz, CDCl3): δ = 9.9 (q), 55.4
(d), 117.6 (d), 117.7 (s), 122.2 (s), 124.5 (d), 125.7 (d), 127.1 (d), 128.7
(d), 129.2 (d), 129.5 (d), 130.9 (d), 132.8 (d), 135.3 (s), 136.2 (s), 154.9
1603 cm-1. HRMS (ESI+) calcd for C22H17O2 [M + H+] 313.1229, found
313.1222.
2-(Bis(4-fluorophenyl)methyl)-4H-chromen-4-one
paste (171 mg, 98%). Rf: 0.25 (hexanes/ethyl acetate, 5:1). 1H NMR (500
MHz, CDCl3 -7.08 (m, 4H), 7.15-7.21
(4b):
Colorless
(s), 162.7 (s), 178.4 (s). IR (ATR): 휈̃
= 1624, 1616, 1605 cm-1. HRMS
(m, 4H), 7.34-7.42 (m, 2H), 7.61-7.66 (m, 1H), 8.17-8.20 (m, 1H). 13C NMR
(125 MHz, CDCl3): δ = 54.4 (d), 112.3 (d), 115.8 (d, JCCF = 21.6 Hz), 117.9
(d), 123.6 (s), 125.2 (d), 125.7 (d), 130.5 (d, JCCCF = 7.8 Hz), 133.8 (d),
(ESI+) calcd for C25H19O2 [M + H+] 351.1385, found 351.1377.
134.4 (s), 156.3 (s), 162.1 (s, JCF = 247.1 Hz), 169.2 (s). IR (ATR): 휈
̃
=
2-Benzhydryl-3-phenyl-4H-chromen-4-one (4j): White solid (173 mg,
89%). Rf: 0.35 (hexanes/ethyl acetate, 5:1). Mp 182-184 ºC. 1H NMR (500
MHz, CDCl3): δ = 5.40 (s, 1H), 7.17-7.22 (m, 4H), 7.23-7.34 (m, 8H), 7.35-
7.47 (m, 5H), 7.59-7.65 (m, 1H), 8.21-8.26 (m, 1H). 13C NMR (125 MHz,
CDCl3): δ = 53.0 (d), 117.9 (d), 123.5 (s), 124.8 (s), 125.0 (d), 126.2 (d),
127.2 (d), 128.2 (d), 128.6 (d), 128.9 (d), 130.3 (d), 132.8 (s), 133.5 (d),
1647, 1601 cm-1. HRMS (ESI+) calcd for C22H15F2O2 [M + H+] 349.1040,
found 349.1033.
2-(10,11-Dihydro-5H-dibenzo[a,d][7]annulen-5-yl)-4H-chromen-4-one
(4c): Yellow solid (130 mg, 77%). Rf: 0.3 (hexanes/ethyl acetate, 5:1). Mp
165-167 ºC. 1H NMR (500 MHz, CDCl3): δ = 2.81-2.89 (m, 2H), 3.30-3.39
139.8 (s), 155.9 (s), 164.5 (s), 177.2 (s). IR (ATR): 휈̃ = 1643, 1622, 1599,
This article is protected by copyright. All rights reserved.

10.1002/ejoc.201900519
European Journal of Organic Chemistry
FULL PAPER
1574 cm-1. HRMS (ESI+) calcd for C28H21O2 [M + H+] 389.1542, found
389.1531.
column chromatography on silica gel (hexanes-EtOAc) to give 5a (149 mg,
0.452 mmol) in 90% yield.
2-(Bis(4-fluorophenyl)methyl)-3-phenyl-4H-chromen-4-one
(4k):
2-(Hydroxydiphenylmethyl)chroman-4-one (5a): White solid (149 mg,
90%). Rf: 0.4 (hexanes/ethyl acetate, 5:1). Mp 174-175 ºC. 1H NMR (500
MHz, CDCl3): δ = 2.26 (dd, 1H, J = 2.0, 17.2 Hz), 2.97 (s, 1H), 3.07 (dd,
1H, J = 13.8, 17.2 Hz), 5.41 (dd, 1H, J = 2.0, 13.8 Hz), 6.92-6.96 (m, 1H),
7.03-7.08 (m, 1H), 7.20-7.25 (m, 1H), 7.27-7.33 (m, 3H), 7.35-7.41 (m, 4H),
7.45-7.51 (m, 1H), 7.56-7.61(m, 2H), 7.87-7.91 (m, 1H). 13C NMR (125
MHz, CDCl3): δ = 37.5 (t), 78.7 (s), 80.5 (d), 117.9 (d), 121.1 (s), 121.9 (d),
125.6 (d), 126.8 (d), 127.0 (d), 127.4 (d), 128.3 (d), 128.5 (d), 136.1 (d),
White solid (191 mg, 90%): Rf: 0.40 (hexanes/ethyl acetate, 5:1). Mp 178-
179 ºC. 1H NMR (500 MHz, CDCl3): δ = 5.35 (s, 1H), 6.98-7.04 (m, 4H),
7.11-7.17 (m, 4H), 7.21-7.25 (m, 2H), 7.36-7.48 (m, 5H), 7.63-7.67 (m, 1H),
8.22-8.25 (m, 1H). 13C NMR (125 MHz, CDCl3): δ = 51.5 (d), 115.6 (d, JCCF
= 21.6 Hz), 117.7 (d), 123.4 (s), 124.7 (s), 125.2 (d), 126.3 (d), 128.3 (d),
128.7 (d), 130.2 (d) 130.4 (d, JCCCF = 8.4 Hz), 132.5 (s), 133.7 (d), 135.4
(s, JCCCCF = 3.0 Hz), 155.8 (s), 162.0 (s, JCF = 247.1 Hz), 162.9 (s), 177.1
(s). IR (ATR): 휈
̃
= 1639, 1622, 1614, 1601, 1576, 1504 cm−1. HRMS (ESI+)
141.9 (s), 144.3 (s), 160.9 (s), 192.8 (s). IR (ATR): 휈̃ = 3526 (br), 1686,
1605 cm-1. HRMS (ESI+) calcd for C22H19O3 [M + H+] 331.1334, found
calcd for C28H19F2O2 [M + H+] 425.1353, found 425.1343.
331.1315.
2-Benzhydryl-6-methoxy-3-phenyl-4H-chromen-4-one (4n): White
solid (190 mg, 91%). Rf: 0.55 (hexanes/ethyl acetate, 2:1). Mp 201-202 °C.
1H NMR (500 MHz, CDCl3): δ = 3.88 (s, 3H), 5.38 (s, 1H), 7.16-7.20 (m,
3H), 7.22 (dd, 1H, J = 2.9, 9.2 Hz), 7.25-7.35 (m, 10H), 7.38-7.46 (m, 3H),
7.59 (d, 1H, J = 2.9 Hz). 13C NMR (125 MHz, CDCl3): δ = 53.0 (d), 55.9 (q),
105.3 (d), 119.3 (d), 123.5 (d), 124.0 (s), 127.1 (d), 128.1 (d), 128.5 (d),
128.9 (d), 130.3 (d) 133.0 (s), 139.9 (s), 150.7 (s), 156.9 (s), 164.3 (s),
2-(Bis(4-fluorophenyl)(hydroxy)methyl)chroman-4-one (5b): Yellow
paste (163 mg, 89%). Rf: 0.35 (hexanes/ethyl acetate, 5:1). 1H NMR (500
MHz, CDCl3): δ = 2.24 (dd, 1H, J = 2.3, 17.2 Hz), 3.009 (dd, 1H, J = 13.8,
17.2 Hz), 3.012 (brs, 1H), 5.31 (dd, 1H, J = 13.8, 17.2 Hz), 6.89-6.94 (m,
1H), 6.97-7.10 (m, 5H), 7.30-7.37 (m, 2H), 7.45-7.56 (m, 3H), 7.86-7.90
(m, 1H). 13C NMR (125 MHz, CDCl3): δ = 37.4 (t), 78.2 (s), 80.4 (d), 115.2
(d, JCCF = 21.6 Hz), 115.4 (d, JCCF = 21.3 Hz), 117.8 (d), 121.0 (s), 122.2
(d), 127.1 (d), 127.5 (d, JCCCF = 8.4 Hz), 128.7 (d, JCCCF = 8.4 Hz), 136.2
(d), 137.6 (s, JCCCCF = 3.3 Hz), 139.9 (s, JCCCCF = 2.7 Hz), 160.6 (s), 162.0
177.0 (s). IR (ATR): 휈̃
= 1639, 1616, 1578 cm−1. HRMS (ESI+) calcd for
C29H23O3 [M + H+] 419.1647, found 419.1639.
(s, JCF = 247.1 Hz), 162.1 (s, JCF = 247.1 Hz), 192.3 (s). IR (ATR): 휈̃ = 3447
2-Benzhydryl-7-methoxy-3-phenyl-4H-chromen-4-one (4o): White
solid (195 mg, 93%). Rf: 0.25 (hexanes/ethyl acetate, 5:1). Mp 228-229 °C.
1H NMR (500 MHz, CDCl3): δ = 3.88 (s, 3H), 5.38 (s, 1H), 6.76 (d, 1H, J =
2.3 Hz), 6.95 (dd, 1H, J = 2.3, 9.0 Hz), 7.17-7.21 (m, 4H), 7.24-7.35 (m,
8H), 7.38-7.46 (m, 3H), 8.13 (d, 1H, J = 9.0 Hz). 13C NMR (125 MHz,
CDCl3): δ = 52.9 (d), 55.8 (q), 99.9 (d), 114.5 (d), 117.3 (s), 124.6 (s), 127.1
(d), 127.6 (d), 128.1 (d), 128.5 (d), 128.6 (d), 128.9 (d), 130.3 (d), 132.9
(s), 139.9 (s), 157.6 (s), 163.95 (s), 164.02 (s), 176.6 (s). IR (ATR): 휈̃ =
1647, 1622, 1597, 1568 cm−1. HRMS (ESI+) calcd for C29H23O3 [M + H+]
419.1647, found 419.1640.
(br), 1682, 1603 cm-1. HRMS (ESI+) calcd for C22H17F2O3 [M + H+]
367.1146, found 367.1138.
2-(5-Hydroxy-10,11-dihydro-5H-dibenzo[a,d][7]annulen-5-
yl)chroman-4-one (5c): White solid (168 mg, 94%). Rf: 0.2 (hexanes/ethyl
acetate, 10:1). Mp 153-155 ºC. 1H NMR (500 MHz, CDCl3): δ = 2.35 (dd,
1H, J = 2.9, 17.3 Hz), 2.93 (dd, 1H, J = 13.2, 17.3 Hz), 2.96-3.07 (m, 2H),
3.30-3.39 (m, 1H), 3.34 (brs, 1H), 3.46-3.54 (m, 1H), 5.49 (dd, 1H, J = 2.9,
13.2 Hz), 6.74-6.80 (m, 1H), 6.95-7.01 (m, 1H), 7.09-7.15 (m, 2H), 7.19-
7.31 (m, 4H), 7.36-7.42 (m, 1H), 7.79-7.84 (m, 1H), 7.86-7.91 (m, 1H),
7.95-8.00 (m, 1H). 13C NMR (125 MHz, CDCl3): δ = 33.7 (t), 33.9 (t), 38.1
(t), 78.8 (s), 82.0 (d), 118.0 (d), 120.8 (s), 121.7 (d), 126.0 (d), 126.6 (d),
126.8 (d), 126.9 (d), 127.0 (d), 127.8 (d), 128.2 (d), 130.8 (d), 130.9 (d),
135.9 (d), 137.6 (s), 137.7 (s), 139.3 (s), 141.3 (s), 160.7 (s), 192.7 (s). IR
2-Benzhydryl-7-methoxy-3-(4-methoxyphenyl)-4H-chromen-4-one
(4p): White solid (206 mg, 92%). Rf: 0.4 (hexanes/ethyl acetate, 2:1). Mp
181-182 °C. 1H NMR (500 MHz, CDCl3): δ = 3.84 (s, 3H), 3.88 (s, 3H),
5.43 (s, 1H), 6.75 (d, 1H, J = 2.4 Hz), 6.92-6.98 (m, 3H), 7.17-7.23 (m, 6H),
7.25-7.34 (m, 6H), 8.13 (d, 1H, J = 9.2 Hz). 13C NMR (125 MHz, CDCl3): δ
= 52.9 (d), 55.3 (q), 55.8 (q), 99.9 (d), 114.1 (d), 114.4 (d), 117.3 (s), 124.2
(s), 125.0 (s), 127.1 (d), 127.6 (d), 128.6 (d), 128.9 (d), 131.5 (d), 140.1
(ATR): 휈̃
= 3545 (br), 1695, 1605 cm-1. HRMS (ESI+) calcd for C24H21O3
[M + H+] 357.1491, found 357.1482.
(d), 157.6 (d), 159.4 (s), 164.0 (s), 176.8 (s). IR (ATR): 휈
̃
= 1632, 1611,
2-(5-Hydroxy-5H-dibenzo[a,d][7]annulen-5-yl)chroman-4-one
(5d):
1570, 1512 cm−1. HRMS (ESI+) calcd for C30H25O4 [M + H+] 449.1753,
White solid (158 mg, 89%). Rf: 0.25 (hexanes/ethyl acetate, 10:1). Mp 222-
224 ºC. 1H NMR (500 MHz, CDCl3): δ = 1.83 (dd, 1H, J = 2.7, 17.5 Hz),
2.84 (dd, 1H, J = 14.3, 17.5 Hz), 3.53 (s, 1H), 5.41 (dd, 1H, J = 2.7, 14.3
Hz), 6.64-6.70 (m, 1H), 6.90-7.01 (m, 3H), 7.28-7.40 (m, 5H), 7.43-7.48 (m,
1H), 7.50-7.56 (m, 1H), 7.75-7.81 (m, 1H), 7.97-8.07 (m, 2H). 13C NMR
(125 MHz, CDCl3): δ = 37.9 (t), 76.0 (d), 77.2 (s), 117.9 (d), 120.6 (s), 121.6
(d), 124.8 (d), 125.0 (d), 126.7 (d), 127.0 (d), 127.3 (d), 128.9 (d), 129.2
(d), 129.39 (d), 129.41 (d), 131.3 (d), 131.5 (d), 131.98 (s), 132.04 (s),
found 449.1740.
2-Benzhydryl-5,7-dimethoxy-3-(4-methoxyphenyl)-4H-chromen-4-
one (4q): White solid (203 mg, 85%). Rf: 0.35 (hexanes/ethyl acetate, 1:2).
Mp 225-226 °C. 1H NMR (500 MHz, CDCl3): δ = 3.83 (s, 3H), 3.84 (s, 3H),
3.88 (s, 3H), 5.35 (s, 1H), 6.31-6.35 (m, 2H), 6.90-6.95 (m, 2H), 7.14-7.22
(m, 6H), 7.24-7.34 (m, 6H). 13C NMR (125 MHz, CDCl3): δ = 52.5 (d), 55.2
(q), 55.7 (q), 56.2 (q), 92.4 (d), 96.0 (d), 108.8 (s), 113.8 (d), 125.0 (s),
125.2 (s), 127.1 (d), 128.5 (d), 128.9 (d), 131.7 (d), 140.2 (s), 159.2 (s),
135.8 (d), 136.6 (s), 139.8 (s), 160.7 (s), 192.7 (s). IR (ATR): 휈̃ = 3549 (br),
1690, 1599 cm-1. HRMS (ESI+) calcd for C24H19O3 [M + H+] 355.1334,
found 355.1326.
159.4 (s), 161.2 (s), 161.6 (s), 163.9 (s), 176.3 (s). IR (ATR): 휈̃ = 1636,
1609, 1572, 1510 cm−1. HRMS (ESI+) calcd for C31H27O5 [M + H+]
479.1858, found 479.1849.
2-(9-Hydroxy-9H-xanthen-9-yl)chroman-4-one (5e): White solid (152
mg, 88%). Rf: 0.25 (hexanes/ethyl acetate, 5:1). Mp 172-174 ºC. 1H NMR
(500 MHz, CDCl3): δ = 2.30-2.41 (m, 2H), 3.42 (s, 1H), 4.60 (dd, 1H, J =
4.2, 12.2 Hz), 6.93-7.01 (m, 2H), 7.15-7.22 (m, 4H), 7.34-7.40 (m, 2H),
7.42-7.47 (m, 1H), 7.70-7.75 (m, 2H), 7.80-7.85 (m, 1H). 13C NMR (125
MHz, CDCl3): δ = 37.8 (t), 70.3 (s), 83.9 (d), 116.2 (d), 116.4 (d), 117.8 (d),
120.6 (s), 121.5 (d), 122.6 (s), 122.8 (s), 123.36 (d), 123.40 (d), 126.7 (d),
126.8 (d), 127.7 (d), 129.6 (d), 129.8 (d), 135.9 (d), 150.8 (s), 150.9 (s),
Desilylation of 3 with 1 M HCl aq and dioxane. To a solution of 3a (201
mg, 0.50 mmol) in dioxane (5 mL) was added 1 M HCl aq (5 mL) at 25 ºC,
and then the solution was stirred at this temperature for 2 h. The mixture
was neutralized with sat. NaHCO3 aq and extracted with ethyl acetate (10
mL × 3). After removal of the solvent in vacuo, the residue was purified by
This article is protected by copyright. All rights reserved.

10.1002/ejoc.201900519
European Journal of Organic Chemistry
FULL PAPER
160.6 (s), 191.7 (s). IR (ATR): 휈
̃
= 3435 (br), 1667, 1601 cm-1. HRMS
(2R*,3R*)-2-(Bis(4-fluorophenyl)(hydroxy)methyl)-3-phenylchroman-
4-one (cis-5k): Colorless paste (195 mg, 88%). Rf: 0.4 (hexanes/ethyl
acetate, 5:1). 1H NMR (500 MHz, CDCl3): δ = 2.43 (brs, 1H), 3.56 (d, 1H,
J = 2.7 Hz), 5.54 (d, 1H, J = 2.7 Hz), 6.91-7.01 (m, 4H), 7.02-7.08 (m, 2H),
7.10-7.28 (m, 7H), 7.39-7.44 (m, 2H), 7.59-7.64 (m, 1H), 7.94-7.98 (m 1H).
13C NMR (125 MHz, CDCl3): δ = 53.2 (d), 79.2 (s), 82.6 (d), 115.1 (d, JCCF
= 21.0 Hz), 115.4 (d, JCCF = 21.0 Hz), 118.0 (d), 120.6 (s), 122.9 (d), 127.6
(d, JCCCF = 7.8 Hz), 127.96 (d, JCCCF = 7.8 Hz), 127.99 (d), 128.6 (d), 128.9
(d), 129.4 (d), 133.8 (s), 136.6 (d), 138.1 (s, JCCCCF = 2.4 Hz), 140.7 (s,
JCCCCF = 2.4 Hz), 160.9 (s), 161.8 (s, JCF = 247.1 Hz), 162.1 (s, JCF = 247.1
(ESI+) calcd for C22H17O4 [M + H+] 345.1127, found 345.1121.
2-(9-Hydroxy-9H-fluoren-9-yl)chroman-4-one (5f): Yellow paste (141
mg, 86%). Rf: 0.2 (hexanes/ethyl acetate, 5:1). 1H NMR (500 MHz, CDCl3):
δ = 2.11 (dd, 1H, J = 2.9, 17.0 Hz), 2.20 (dd, 1H, J = 13.9, 17.0 Hz), 3.29
(brs, 1H), 4.98 (dd, 1H, J = 2.9, 13.9 Hz), 7.00-7.06 (m, 1H), 7.17-7.21 (m,
1H), 7.26-7.35 (m, 2H), 7.38-7.5 (m, 2H), 7.51-7.56 (m, 2H), 7.63-7.68 (m,
2H), 7.73-7.77 (m, 1H), 7.79-7.83 (m, 1H). 13C NMR (125 MHz, CDCl3): δ
= 37.8 (t), 82.2 (d), 82.8 (s), 117.8 (d), 120.2 (d), 120.3 (d), 120.8 (s), 121.7
(d), 123.9 (d), 125.9 (d), 126.9 (d), 128.1 (d), 128.3 (d), 129.6 (d), 130.0
(d), 136.1 (d), 140.2 (s), 140.4 (s), 144.2 (s), 144.3 (s), 161.1 (s), 191.8 (s).
Hz), 190.9 (s). IR (ATR): 휈̃
= 3433 (br), 1686, 1603, 1506 cm−1. HRMS
(ESI+) calcd for C28H21F2O3 [M + H+] 443.1459, found 443.1447.
IR (ATR): 휈̃
= 3428 (br), 1684, 1605 cm-1. HRMS (ESI+) calcd for C22H17O3
[M + H+] 329.1178, found 329.1171.
2-(Hydroxydiphenylmethyl)-2-methylchroman-4-one (5l): Colorless
paste (131 mg, 76%). Rf: 0.35 (hexanes/ethyl acetate, 5:1). 1H NMR (500
MHz, CDCl3): δ = 1.54 (s, 3H), 2.53 (brd, 1H, J = 16.1 Hz), 3.12 (brs, 1H),
3.30 (brd, 1H, J = 16.1 Hz), 6.98-7.03 (m, 1H), 7.03-7.08 (m, 1H), 7.22-
(2R*,3R*)-2-(Hydroxydiphenylmethyl)-3-methylchroman-4-one (cis-
5g): White solid (136 mg, 79%). Rf: 0.55 (hexanes/ethyl acetate, 5:1). Mp
153-155 ºC. 1H NMR (500 MHz, CDCl3): δ = 1.30 (d, 3H, J = 6.9 Hz), 2.30-
2.36 (m, 1H), 3.10 (brs, 1H), 5.32 (d, 1H, J = 1.7 Hz), 6.97-7.01 (m, 1H),
7.07-7.11 (m, 1H), 7.21-7.36 (m, 6H), 7.39-7.43 (m, 2H), 7.48-7.53 (m, 3H),
7.90-7.93 (m, 1H). 13C NMR (125 MHz, CDCl3): δ = 11.3 (q), 42.3 (d), 79.6
(s), 81.2 (d), 117.5 (d), 119.8 (s), 122.1 (d), 125.3 (d), 126.6 (d), 127.27
(d), 127.32 (d), 128.0 (d), 128.3 (d), 128.5 (d), 135.8 (d), 141.9 (s), 145.9
7.35 (m, 6H), 7.48-7.53 (m, 1H), 7.60-7.67 (m, 4H), 7.82-7.86 (m, 1H). 13
C
NMR (125 MHz, CDCl3): δ = 19.6 (q), 44.2 (t), 81.7 (s), 86.5 (s), 118.3 (d),
120.5 (s), 121.2 (d), 126.4 (d), 127.3 (d), 127.4 (d), 127.68 (d), 127.72 (d),
128.3 (d), 128.8 (d), 136.2 (d), 143.2 (s), 143.5 (s), 158.6 (s), 192.5 (s). IR
(ATR): 휈̃
= 3466 (br), 1676, 1605 cm-1. HRMS (ESI+) calcd for C23H21O3
[M + H+] 345.1491, found 345.1483.
(s), 160.7 (s), 196.5 (s). IR (ATR): 휈̃
= 3385 (br), 1678, 1605 cm-1. HRMS
(ESI+) calcd for C23H21O3 [M + H+] 345.1491, found 345.1485.
2-(Bis(4-fluorophenyl)(hydroxy)methyl)-2-methylchroman-4-one
(5m): Colorless paste (156 mg, 82%). Rf: 0.3 (hexanes/ethyl acetate, 5:1).
1H NMR (500 MHz, CDCl3): δ = 1.53 (s, 3H), 2.50 (d, 1H, J = 16.6 Hz),
3.03 (brs, 1H), 3.24 (d, 1H, J = 16.6 Hz), 6.97-7.07 (m, 6H), 7.51-7.56 (m,
1H), 7.57-7.64 (m, 4H), 7.84-7.87 (m, 1H). 13C NMR (125 MHz, CDCl3): δ
= 19.6 (q), 44.1 (t), 81.2 (s), 86.4 (s), 114.7 (d, JCCF = 21.6 Hz), 118.2 (d),
(2R*,3R*)-2-(bis(4-fluorophenyl)(hydroxy)methyl)-3-methylchroman-
4-one (cis-5h): White solid (146 mg, 77%). Rf: 0.45 (hexanes/ethyl acetate,
5:1). Mp 152-154 ºC. 1H NMR (500 MHz, CDCl3): δ = 1.28 (d, 3H, J = 7.2
Hz), 2.28-2.34 (m, 1H), 3.11 (s, 1H), 5.23 (d, 1H, J = 1.9 Hz), 6.96-7.05 (m,
5H), 7.08-7.13 (m, 1H), 7.34-7.39 (m, 2H), 7.43-7.47 (m, 2H), 7.50-7.54
(m, 1H), 7.90-7.94 (m 1H). 13C NMR (125 MHz, CDCl3): δ = 11.2 (q), 42.3
(d), 79.0 (s), 81.1 (d), 115.2 (d, JCCF = 21.0 Hz), 115.5 (d, JCCF = 21.6 Hz),
117.4 (d), 119.8 (s), 122.4 (d), 127.1 (d, JCCCF = 8.4 Hz), 128.1 (d), 128.4
(d, JCCCF = 8.4 Hz), 136.0 (d), 137.7 (s, JCCCCF = 3.0 Hz), 141.6 (s, JCCCCF
= 3.6 Hz), 160.4 (s), 161.9 (s, JCF = 247.1 Hz), 162.0 (s, JCF = 247.1 Hz),
120.5 (s), 121.6 (d), 126.6 (d), 130.1 (d, JCCCF = 7.5 Hz), 130.6 (d, JCCCF
7.5 Hz), 136.4 (d), 138.8 (s), 139.1 (s), 158.4 (s), 161.9 (s, JCF = 247.1 Hz),
162.0 (s, JCF = 247.7 Hz), 192.1 (s). IR (ATR): 휈 = 3450 (br), 1678, 1603
=
̃
cm-1. HRMS (ESI+) calcd for C23H19F2O3 [M + H+] 381.1302, found
381.1290.
196.1 (s). IR (ATR): 휈
̃
= 3547 (br), 3460 (br), 1695, 1686, 1603 cm-1. HRMS
(2R*,3R*)-2-(Hydroxydiphenylmethyl)-6-methoxy-3-phenylchroman-
4-one (cis-5n): Colorless paste (201 mg, 92%). Rf: 0.35 (hexanes/ethyl
acetate, 5:1). 1H NMR (500 MHz, CDCl3): δ = 2.40 (brs, 1H), 3.56 (dd, 1H,
J = 2.7 Hz), 3.80 (s, 3H), 5.59 (dd, 1H, J = 2.7 Hz), 6.93-6.97 (m, 2H), 7.05
(d, 1H, J = 8.9 Hz), 7.17-7.36 (m, 12H), 7.37 (d, 1H, J = 3.3 Hz), 7.45-7.49
(m, 2H). 13C NMR (125 MHz, CDCl3): δ = 52.8 (d), 55.7 (q), 79.7 (s), 82.8
(d), 108.6 (d), 119.3 (d), 120.6 (s), 125.59 (d), 125.63 (d), 126.0 (d), 127.0
(d), 127.4 (d), 127.8 (d), 128.2 (d), 128.4 (d), 128.7 (d), 129.5 (d), 134.1
(ESI+) calcd for C23H19F2O3 [M + H+] 381.1302, found 381.1291.
(2R*,3R*)-2-(5-Hydroxy-5H-dibenzo[a,d][7]annulen-5-yl)-3-
methylchroman-4-one (cis-5i): White solid (175 mg, 95%). Rf: 0.45
(hexanes/ethyl acetate, 5:1). Mp 248-250 ºC. 1H NMR (500 MHz, CDCl3):
δ = 1.09 (d, 3H, J = 7.4 Hz), 2.02-2.07 (m, 1H), 3.82 (s, 1H), 5.24 (d, 1H,
J = 2.4 Hz), 6.72-6.77 (m, 1H), 6.93-7.00 (m, 3H), 7.28-7.38 (m, 5H), 7.43-
7.53 (m, 2H), 7.76-7.80 (m, 1H), 8.01-8.06 (m, 1H), 8.10-8.14 (m, 1H). 13
C
(s), 142.3 (s), 145.1 (s), 154.9 (s), 155.8 (s), 191.4 (s). IR (ATR): 휈̃ = 3551
(br), 1680, 1616 cm−1. HRMS (ESI+) calcd for C29H25O4 [M + H+] 437.1753,
found 437.1744.
NMR (125 MHz, CDCl3): δ = 10.8 (q), 42.8 (d), 77.6 (s), 77.9 (d), 117.5 (d),
119.2 (s), 121.8 (d), 124.7 (d), 124.9 (d), 126.9 (d), 127.2 (d), 127.7 (d),
128.9 (d), 129.0 (d), 129.3 (d), 129.5 (d), 131.5 (d), 131.7 (d), 131.8 (s),
132.3 (s), 135.5 (d), 136.7 (s), 141.1 (s), 160.4 (s), 196.2 (s). IR (ATR): 휈
= 3470 (br), 1682, 1607 cm-1. HRMS (ESI+) calcd for C25H21O3 [M + H+]
369.1491, found 369.1482.
̃
(2R*,3R*)-2-(Hydroxydiphenylmethyl)-7-methoxy-3-phenylchroman-
4-one (cis-5o): White solid (205 mg, 94%). Rf: 0.3 (hexanes/ethyl acetate,
5:1). Mp 101-102 °C. 1H NMR (500 MHz, CDCl3): δ = 2.36 (brs, 1H), 3.54
(d, 1H, J = 2.7 Hz), 3.87 (s, 3H), 5.66 (d, 1H, J = 2.7 Hz), 6.56 (d, 1H, J =
2.3 Hz), 6.70 (dd, 1H, J = 2.3, 8.7 Hz), 6.91-6.95 (m, 2H), 7.19-7.36 (m,
11H), 7.48-7.51 (m, 2H), 7.89 (d, 1H, J = 9.0 Hz). 13C NMR (125 MHz,
CDCl3): δ = 52.8 (d), 55.7 (q), 79.7 (s), 82.8 (d), 101.0 (d), 111.2 (d), 114.2
(s), 125.5 (d), 125.9 (d), 127.0 (d), 127.5 (d), 127.8 (d), 128.3 (d), 128.4
(d), 128.8 (d), 129.5 (d), 130.1 (d), 134.3 (s), 142.4 (s), 145.0 (s), 163.2 (s),
(2R*,3R*)-2-(Hydroxydiphenylmethyl)-3-phenylchroman-4-one (cis-
5j): Colorless paste (193 mg, 95%). Rf: 0.45 (hexanes/ethyl acetate, 5:1).
1H NMR (500 MHz, CDCl3): δ = 2.41 (s, 1H), 3.59 (d, 1H, J = 2.7 Hz), 5.64
(d, 1H, J = 2.7 Hz) 6.91-6.96 (m, 2H), 7.09-7.17 (m, 2H), 7.18-7.37 (m,
11H), 7.46-7.51 (m, 2H), 7.56-7.61 (m, 1H), 7.94-7.98 (m, 1H). 13C NMR
(125 MHz, CDCl3): δ = 53.1 (d), 79.8 (s), 82.7 (d), 118.1 (d), 120.7 (s),
122.6 (d), 125.6 (d), 126.1 (d), 127.1 (d), 127.5 (d), 127.9 (d), 128.3 (d),
128.48 (d), 128.54 (d), 128.8 (d), 129.6 (d), 134.1 (s), 136.5 (d), 142.3 (s),
166.4 (s), 190.1 (s). IR (ATR): 휈̃ = 3418 (br), 1728, 1670, 1599, 1578, 1560
cm−1. HRMS (ESI+) calcd for C29H25O4 [M + H+] 437.1753, found 437.1743.
145.0 (s), 161.2 (s), 191.3 (s). IR (ATR): 휈
̃
= 3447 (br), 1684, 1645, 1605
(2R*,3R*)-2-(Hydroxydiphenylmethyl)-7-methoxy-3-(4-
cm-1. HRMS (ESI+) calcd for C28H23O3 [M + H+] 407.1647, found 407.1636.
methoxyphenyl)chroman-4-one (cis-5p): White solid (191 mg, 82%). Rf:
0.55 (hexanes/ethyl acetate, 2:1). Mp 226-228 °C. 1H NMR (500 MHz,
CDCl3): δ = 2.42 (brs, 1H), 3.50 (d, 1H, J = 2.8 Hz), 3.76 (s, 3H), 3.86 (s,
This article is protected by copyright. All rights reserved.

10.1002/ejoc.201900519
European Journal of Organic Chemistry
FULL PAPER
3H), 5.63 (d, 1H, J = 2.8 Hz), 6.56 (d, 1H, J = 2.3 Hz), 6.69 (dd, 1H, J =
2.3, 8.7 Hz), 6.74-6.78 (m, 2H), 6.84-6.88 (m, 2H), 7.20-7.36 (m, 8H), 7.48-
7.52 (m, 2H), 7.88 (d, 1H, J = 8.7 Hz). 13C NMR (125 MHz, CDCl3): δ =
51.8 (d), 55.1 (q), 55.7 (q), 79.7 (s), 82.6 (d), 100.9 (d), 111.1 (d), 114.1
(s), 114.3 (d), 125.5 (d), 125.9 (d), 127.0 (d), 127.4 (d), 128.2 (d), 128.4
(d), 130.0 (d), 130.6 (d), 142.6 (s), 144.8 (s), 159.2 (s), 163.2 (s), 166.3 (s),
7.21-7.31 (m, 4H), 7.43-7.48 (m, 1H), 7.52 (d, 1H, J = 15.2 Hz), 7.57-7.60
(m, 1H), 7.87-7.93 (m, 2H), 12.53 (s, 1H). 13C NMR (125 MHz, CDCl3): δ
= 33.6 (t), 77.7 (s), 118.5 (d), 118.9 (d), 119.7 (s), 122.3 (d), 126.3 (d),
126.6 (d), 128.2 (d), 129.9 (d), 130.5 (d), 136.6 (d), 138.9 (s), 141.4 (s),
153.2 (s), 163.4 (s). IR (ATR): 휈̃
= 3242 (br), 1636, 1582 cm-1. HRMS
(ESI+) calcd for C24H21O3 [M + H+] 357.1491, found 357.1477.
190.3 (s). IR (ATR): 휈̃ .
= 3456 (br), 1672, 1599, 1599, 1578. 1510 cm−1
HRMS (ESI+) calcd for C30H27O5 [M + H+] 467.1858, found 467.1845.
(E)-3-(5-Hydroxy-5H-dibenzo[a,d][7]annulen-5-yl)-1-(2-
hydroxyphenyl)prop-2-en-1-one (6d): Yellow solid (158 mg, 89%). Rf:
0.25 (hexanes/ethyl acetate, 10:1). Mp 149-151 ºC. 1H NMR (500 MHz,
CDCl3): δ = 2.62 (brs, 1H), 6.79-6.87 (m, 2H), 6.92-6.97 (m, 1H), 7.03 (s,
2H), 7.30-7.52 (m, 9H), 7.95-8.00 (m, 2H), 12.47 (s, 1H). 13C NMR (125
MHz, CDCl3): δ = 75.5 (s), 118.4 (d), 118.8 (d), 119.5 (s), 123.26 (d),
123.29 (d), 127.1 (d), 128.8 (d), 129.2 (d), 129.9 (d), 131.7 (d), 132.7 (s),
136.5 (d), 140.7 (s), 151.4 (d), 163.2 (s), 194.5 (s). IR (ATR): 휈̃ = 3466 (br),
3377, 1634, 1578 cm-1. HRMS (ESI+) calcd for C24H19O3 [M + H+]
355.1334, found 355.1327.
(2R*,3R*)-2-(Hydroxydiphenylmethyl)-5,7-dimethoxy-3-(4-
methoxyphenyl)chroman-4-one (cis-5q): White solid (231 mg, 93%). Rf:
0.35 (hexanes/ethyl acetate, 1:1). Mp 116-117 °C. 1H NMR (500 MHz,
CDCl3): δ = 2.40 (brs, 1H), 3.44 (d, 1H, J = 2.7 Hz), 3.75 (s, 3H), 3.84 (s,
3H), 3.85 (s, 3H), 5.60 (d, 1H, J = 2.7 Hz), 6.15 (d, 1H, J = 2.2 Hz), 6.20
(d, 1H, J = 2.2 Hz), 6.73-6.77 (m, 2H), 6.87-6.91 (m, 2H), 7.19-7.38 (m,
8H), 7.47-7.51 (m, 2H). 13C NMR (125 MHz, CDCl3): δ = 53.1 (d), 55.1 (q),
55.7 (q), 56.1 (q), 79.6 (s), 81.8 (d), 93.5 (d), 93.7 (d), 104.9 (s), 114.2 (d),
125.5 (d), 125.9 (d), 126.1 (s), 126.9 (d), 127.4 (d), 128.2 (d), 128.4 (d),
130.7 (d), 142.7 (s), 144.8 (s), 159.1 (s), 163.2 (s), 164.6 (s), 166.2 (s),
(E)-3-(9-Hydroxy-9H-fluoren-9-yl)-1-(2-hydroxyphenyl)prop-2-en-1-
one (6f): Yellow solid (161 mg, 98%). Rf: 0.3 (hexanes/ethyl acetate, 5:1).
Mp 158-159 ºC. 1H NMR (500 MHz, CDCl3): δ = 2.39 (brs, 1H), 6.91-7.01
(m, 3H), 7.29-7.35 (m, 2H), 7.39-7.52 (m, 5H), 7.65-7.70 (m, 2H), 7.76 (d,
1H, J = 15.0 Hz), 7.94-7.99 (m, 1H), 12.62 (brs, 1H). 13C NMR (125 MHz,
CDCl3): δ = 82.3 (s), 118.4 (d), 118.8 (d), 119.7 (s), 120.4 (d), 121.2 (d),
124.7 (d), 128.4 (d), 129.8 (d), 130.1 (d), 136.5 (d), 139.6 (s), 146.4 (s),
188.8 (s). IR (ATR): 휈
HRMS (ESI+) calcd for C31H29O6 [M + H+] 497.1964, found 497.1952.
̃ .
= 3534 (br), 1740, 1674, 1601, 1754, 1508 cm−1
Dehydration of 5. A solution of 5a (165 mg, 0.50 mmol) and p-TsOH (10
mg) in toluene (10 mL) was refluxed using Dean-Stark apparatus under
nitrogen atmosphere for 1 h. After the solvent was removed in vacuo, the
residue was purified by column chromatography on silica gel (hexanes-
EtOAc) to give 4a (144 mg, 0.462 mmol) in 92% yield.
149.3 (d), 163.5 (s), 194.0 (s). IR (ATR): 휈̃ = 3418 (br), 1639, 1618, 1587
cm-1. HRMS (ESI+) calcd for C22H17O3 [M + H+] 329.1178, found 329.1172.
Desilylation of 3 with TBAF and subsequent treatment with NaH. To a
solution of 3a (201 mg, 0.50 mmol) in THF (10 mL) was added 1 M TBAF
in THF (0.50 mL, 0.50 mmol) at 25 ˚C. After being stirring for 10 min, to the
mixture was added NaH (40% in oil, 30 mg, 0.50 mmol) and the mixture
was stirred for 30 min at this temperature. After addition of AcOH (60 mg,
1.0 mmol), the solvent was removed in vacuo. The residue was purified by
column chromatography on silica gel (hexanes-EtOAc) to give 6a (162 mg,
0.491 mmol) in 98% yield.
(E)-4-Hydroxy-1-(2-hydroxyphenyl)-2-methyl-4,4-diphenylbut-2-en-1-
one (6g): Yellow paste (155 mg, 90%). Rf: 0.45 (hexanes/ethyl acetate,
5:1). 1H NMR (500 MHz, CDCl3): δ = 1.57 (d, 3H, J = 1.7 Hz), 2.57 (brs,
1H), 6.57-6.60 (m, 1H), 6.80-6.86 (m, 1H), 6.98-7.02 (m, 1H), 7.26-7.31
(m, 2H), 7.33-7.39 (m, 4H), 7.41-7.50 (m, 5H), 7.60-7.65 (m, 1H), 11.84 (s,
1H). 13C NMR (125 MHz, CDCl3): δ = 15.1 (q), 79.2 (s), 118.4 (d), 118.6
(d), 126.3 (d), 127.5 (d), 128.4 (d), 132.7 (d), 136.3 (d), 137.9 (s), 142.8
(d), 146.0 (s), 163.1 (s), 204.2 (s). IR (ATR): 휈̃
= 3447 (br), 1620, 1597 cm-
1. HRMS (ESI+) calcd for C23H21O3 [M + H+] 345.1491, found 345.1483.
(E)-4-Hydroxy-1-(2-hydroxyphenyl)-4,4-diphenylbut-2-en-1-one (6a):
Yellow solid (162 mg, 98%). Rf: 0.4 (hexanes/ethyl acetate, 5:1). Mp 140-
141 ºC. 1H NMR (500 MHz, CDCl3): δ = 2.51 (brs, 1H), 6.88-6.93 (m, 1H),
6.98-7.02 (m, 1H), 7.29-7.42 (m, 10H), 7.46-7.51 (m, 1H), 7.54 (d, 1H, J =
15.0 Hz), 7.73 (d, 1H, J = 15.0 Hz), 7.84-7.89 (m, 1H), 12.68 (s, 1H). 13C
NMR (125 MHz, CDCl3): δ = 79.4 (s), 118.4 (d), 118.9 (d), 119.7 (s), 121.0
(d), 126.8 (d), 127.9 (d), 128.5 (d), 130.1 (d), 136.6 (d), 144.2 (s), 152.5
(E)-4,4-Bis(4-fluorophenyl)-4-hydroxy-1-(2-hydroxyphenyl)-2-
methylbut-2-en-1-one (6h): Yellow paste (122 mg, 64%). Rf: 0.4
(hexanes/ethyl acetate, 5:1). 1H NMR (500 MHz, CDCl3): δ = 1.97 (d, 3H,
J = 1.3 Hz), 2.55 (s, 1H), 6.51 (q, 1H, J = 1.3 Hz), 6.81-6.86 (m, 1H), 6.99-
7.08 (m, 5H), 7.36-7.42 (m, 4H), 7.45-7.49 (m, 1H), 7.54-7.58 (m, 1H),
11.81 (s, 1H). 13C NMR (125 MHz, CDCl3): δ = 15.2 (q), 78.6 (s), 115.4 (d,
JCCF = 21.3 Hz), 118.3 (s), 118.6 (d), 118.7 (d), 128.1 (d, JCCCF = 8.4 Hz),
132.5 (d), 136.5 (d), 138.4 (s), 141.7 (d), 141.8 (s, JCCCCF = 3.6 Hz), 162.1
(d), 163.4 (s), 194.2 (s). IR (ATR): 휈̃
= 3431 (br), 1645, 1620, 1582 cm-1.
HRMS (ESI+) calcd for C22H19O3 [M + H+] 331.1334, found 331.1329.
(s, JCF = 248.0 Hz), 163.3 (s), 204.0 (s). IR (ATR): 휈̃ = 3449 (br), 1620,
1599 cm-1. HRMS (ESI+) calcd for C23H19F2O3 [M + H+] 381.1302, found
381.1294.
(E)-4,4-Bis(4-fluorophenyl)-4-hydroxy-1-(2-hydroxyphenyl)but-2-en-
1-one (6b): Yellow solid (153 mg, 91%). Rf: 0.35 (hexanes/ethyl acetate,
5:1). Mp 117-119 ºC. 1H NMR (500 MHz, CDCl3): δ = 2.40 (brs, 1H), 6.88-
6.93 (m, 1H), 6.96-7.00 (m, 1H), 7.01-7.07 (m, 4H), 7.32-7.37 (m, 4H),
7.46-7.52 (m, 2H), 7.63 (d, 1H, J = 15.0 Hz), 7.81-7.85 (m, 1H), 12.58 (brs,
1H). 13C NMR (125 MHz, CDCl3): δ = 78.7 (s), 115.5 (d, JCCF = 21.6 Hz),
118.5 (d), 119.0 (d), 119.7 (s), 121.4 (d), 128.7 (d, JCCCF = 8.4 Hz), 130.0
(d), 136.7 (d), 140.0 (s, JCCCCF = 30 Hz), 151.8 (d), 162.3 (s, JCF = 247.7
(E)-3-(5-Hydroxy-5H-dibenzo[a,d][7]annulen-5-yl)-1-(2-
hydroxyphenyl)-2-methylprop-2-en-1-one (6i): Yellow paste (179 mg,
97%). Rf: 0.45 (hexanes/ethyl acetate, 5:1). 1H NMR (500 MHz, CDCl3): δ
= 1.60 (d, 3H, J = 1.6 Hz), 2.70 (brs, 1H), 6.05 (s, 1H, J = 1.6 Hz), 6.84-
6.90 (m, 1H), 6.91-6.95 (m, 1H), 7.15 (s, 2H), 7.25-7.30 (m, 2H), 7.33-7.38
(m, 2H), 7.41-7.47 (m, 3H), 7.62-7.67 (m, 1H), 8.01-8.06 (m, 2H), 11.67 (s,
1H). 13C NMR (125 MHz, CDCl3): δ = 13.6 (q), 75.0 (s), 118.1 (s), 118.2
(d), 118.3 (d), 123.0 (d), 126.6 (d), 128.7 (d), 128.8 (d), 132.0 (d), 133.3
(d), 136.3 (d), 138.8 (s), 142.9 (s), 144.6 (s), 163.0 (s), 204.0 (s). IR (ATR):
Hz), 163.5 (s), 194.0 (s). IR (ATR): 휈̃
= 3447 (br), 1647, 1616, 1597 cm-1.
HRMS (ESI+) calcd for C22H17F2O3 [M + H+] 367.1146, found 367.1135.
(E)-3-(5-Hydroxy-10,11-dihydro-5H-dibenzo[a,d][7]annulen-5-yl)-1-(2-
hydroxyphenyl)prop-2-en-1-one (6c): Yellow solid (121 mg, 68%). Rf:
0.3 (hexanes/ethyl acetate, 10:1). Mp 122-123 ºC. 1H NMR (500 MHz,
CDCl3): δ = 2.53 (s, 1H), 2.98-3.06 (m, 2H), 3.29-3.38 (m, 2H), 6.83-6.88
(m, 1H), 6.95-6.98 (m, 1H), 7.01 (d, 1H, J = 15.2 Hz), 7.13-7.18 (m, 2H),
휈
̃
= 3460 (br), 1620, 1595 cm-1. HRMS (ESI+) calcd for C25H21O3 [M + H+]
369.1491, found 369.1480.
This article is protected by copyright. All rights reserved.

10.1002/ejoc.201900519
European Journal of Organic Chemistry
FULL PAPER
(E)-4-Hydroxy-1-(2-hydroxyphenyl)-3-methyl-4,4-diphenylbut-2-en-1-
one (6l): Yellow paste (157 mg, 91%). Rf: 0.45 (hexanes/ethyl acetate,
5:1). 1H NMR (500 MHz, CDCl3): δ = 2.11 (d, 3H, J = 1.2 Hz), 2.67 (brs,
1H), 6.82-6.86 (m, 1H), 6.96-6.99 (m, 1H), 7.02 (d, 1H, J = 1.2 Hz), 7.32-
7.47 (m, 11H), 7.57-7.60 (m, 1H), 12.64 (s, 1H). 13C NMR (125 MHz,
CDCl3): δ = 17.8 (q), 83.9 (s), 118.4 (d), 118.8 (d), 120.8 (s), 122.3 (d),
127.9 (d), 128.0 (d), 128.3 (d), 130.1 (d), 136.2 (d), 143.6 (s), 159.9 (s),
MHz, CDCl3): δ = 3.44 (s, 3H), 6.45 (brs, 1H), 6.63 (d, 1H, J = 3.0 Hz), 6.78
(dd, 1H, J = 3.0, 9.0 Hz), 6.90 (d, 1H, J = 9.0 Hz), 7.10-7.14 (m, 2H), 7.15-
7.20 (m, 2H), 7.21-7.30 (m, 9H), 7.44-7.46 (m, 2H). 13C NMR (125 MHz,
CDCl3): δ = 55.3 (q), 112.2 (d), 116.3 (s), 117.0 (d), 118.2 (d), 124.3 (s),
125.8 (d), 127.4 (d), 127.5 (d), 127.8 (d), 128.51 (d), 128.54 (d), 130.1 (d),
130.2 (s), 130.3 (d), 132.1 (s), 132.5 (s), 146.1 (s), 147.4 (s), 148.0 (s),
152.8 (s). IR (ATR): 휈
HRMS (ESI+) calcd for C29H23O3 [M + H+] 419.1647, found 419.1640.
̃ .
= 3545 (br), 3522 (br), 1618, 1603, 1595, 1558 cm−1
163.0 (s), 197.7 (s). IR (ATR): 휈̃
= 3435 (br), 1636, 1582 cm-1. HRMS
(ESI+) calcd for C23H21O3 [M + H+] 345.1491, found 345.1482.
2-(2,2-Diphenylvinyl)-6-methoxy-2-phenylbenzofuran-3(2H)-one (8o):
Colorless paste (77 mg, 74%). Rf: 0.5 (hexanes/ethyl acetate, 5:1). 1H
NMR (500 MHz, CDCl3): δ = 3.81 (s, 3H), 6.14 (d, 1H, J = 2.2 Hz), 6.52
(dd, 1H, J = 8.6, 2.2 Hz), 6.55 (s, 1H), 6.97-7.02 (m, 2H), 7.08-7.13 (m,
3H), 7.20-7.40 (m, 9H), 7.54-7.58 (m, 2H). 13C NMR (125 MHz, CDCl3): δ
= 55.8 (q), 91.5 (s), 95.8 (d), 111.6 (d), 112.5 (s), 125.2 (d), 125.9 (d),
126.2 (d), 126.9 (d), 127.3 (d), 127.4 (d), 127.9 (d), 128.0 (d), 128.1 (d),
128.5 (d), 129.6 (d), 138.9 (s), 139.0 (s), 141.7 (s), 146.7 (s), 168.0 (s),
Dehydration of 6. A solution of 6g (86 mg, 0.25 mmol) and p-TsOH (10
mg) in toluene (10 mL) was refluxed using Dean-Stark apparatus under
nitrogen atmosphere for 1 h. After the solvent was removed in vacuo, the
residue was purified by column chromatography on silica gel (hexanes-
EtOAc) to give 7g (76 mg, 0.233 mmol) in 93% yield.
2-(3-Methyl-4,5-diphenylfuran-2-yl)phenol (7g): Colorless paste (76 mg,
93%). Rf: 0.55 (hexanes/ethyl acetate, 5:1). 1H NMR (500 MHz, CDCl3): δ
= 2.07 (s, 3H), 6.95 (s, 1H), 6.99-7.03 (m, 1H), 7.06-7.09 (m, 1H), 7.18-
7.31 (m, 4H), 7.35-7.38 (m, 2H), 7.39-7.50 (m, 6H). 13C NMR (125 MHz,
CDCl3): δ = 10.1 (q), 116.8 (d), 117.0 (s), 120.29 (d), 120.32 (s), 125.3 (d),
125.6 (s), 127.4 (d), 127.7 (d), 128.4 (d), 128.5 (d), 128.9 (d), 129.6 (d),
130.0 (d), 130.3 (s), 133.3 (s), 145.7 (s), 147.4 (s), 153.5 (s). IR (ATR): 휈
= 3524 (br), 1601 cm-1. HRMS (ESI+) calcd for C23H19O2 [M + H+] 327.1385,
found 327.1379.
173.6 (s), 197.7 (s). IR (ATR): 휈̃
= 1705, 1609, 1593 cm−1. HRMS (ESI+)
calcd for C29H23O3 [M + H+] 419.1647, found 419.1639.
2-(2,2-Diphenylvinyl)-6-methoxy-2-(4-methoxyphenyl)benzofuran-
3(2H)-one (8p): Colorless paste (107 mg, 95%). Rf: 0.3 (hexanes/ethyl
acetate, 5:1). 1H NMR (500 MHz, CDCl3): δ = 3.77 (s, 3H), 3.80 (s, 3H),
6.09 (d, 1H, J = 2.1 Hz), 6.515 (s, 1H), 6.521 (dd, 1H, J = 2.1, 8.6 Hz),
6.83-6.87 (m, 2H), 6.98-7.02 (m, 2H), 7.09-7.14 (m, 3H), 7.20-7.26 (m, 5H),
7.37 (d, 1H, J = 8.6 Hz), 7.44-7.48 (m, 2H). 13C NMR (125 MHz, CDCl3): δ
= 55.3 (q), 55.8 (q), 91.5 (s), 95.8 (d), 111.5 (d), 112.6 (s), 113.9 (s), 125.9
(d), 126.1 (d), 126.7 (d), 126.8 (d), 127.3 (d), 127.4 (d), 127.9 (d), 128.1
(d), 129.5 (d), 131.8 (s), 139.0 (s), 141.8 (s), 146.4 (s), 159.4 (s), 168.0 (s),
̃
2-(4,5-Bis(4-fluorophenyl)-3-methylfuran-2-yl)phenol (7h): White solid
(69 mg, 76%). Rf: 0.45 (hexanes/ethyl acetate, 5:1). Mp 126-127 ºC. 1H
NMR (500 MHz, CDCl3): δ = 2.04 (s, 3H), 6.68 (s, 1H), 6.92-6.98 (m, 2H),
6.99-7.03 (m, 1H), 7.04-7.07 (m, 1H), 7.13-7.19 (m, 2H), 7.27-7.37 (m, 5H),
7.41-7.44 (m, 1H). 13C NMR (125 MHz, CDCl3): δ = 10.0 (q), 115.6 (d, JCCF
= 21.6 Hz), 116.1 (d, JCCF = 21.6 Hz), 116.8 (d), 116.9 (s), 120.2 (s), 120.4
(d), 124.2 (s), 126.5 (s, JCCCCF = 3.6 Hz), 127.2 (d, JCCCF = 8.4 Hz), 128.6
(d), 129.1 (s, JCCCCF = 3.0 Hz), 129.8 (d), 131.7 (d, JCCCF = 8.4 Hz), 145.8
(s), 147.0 (s), 153.5 (s), 162.0 (s, JCF = 248.3 Hz), 162.4 (s, JCCF = 247.1
173.5 (s), 198.0 (s). IR (ATR): 휈̃
= 1707, 1609, 1508 cm−1. HRMS (ESI+)
calcd for C30H25O4 [M + H+] 449.1753, found 449.1742.
2-(2,2-Diphenylvinyl)-4,6-dimethoxy-2-(4-
methoxyphenyl)benzofuran-3(2H)-one (8q): White solid (104 mg, 87%).
Rf: 0.3 (hexanes/ethyl acetate, 2:1). Mp 90-91 °C. 1H NMR (500 MHz,
CDCl3): δ = 3.768 (s, 3H), 3.774 (s, 3H), 3.84 (s, 3H), 5.67 (d, 1H, J = 1.7
Hz), 5.90 (d, 1H, J = 1.7 Hz), 6.52 (s, 1H), 6.80-6.84 (m, 2H), 7.01-7.05 (m,
2H), 7.13-7.17 (m, 3H), 7.21-7.25 (m, 5H), 7.42-7.46 (m, 2H). 13C NMR
(125 MHz, CDCl3): δ = 55.3 (q), 55.8 (q), 55.9 (q), 88.7 (d), 91.5 (s), 92.8
(d), 102.9 (s), 113.8 (d), 126.4 (d), 126.6 (d), 126.8 (d), 127.2 (d), 127.4
(d), 127.8 (d), 128.1 (d), 129.5 (d), 131.3 (s), 139.3 (s), 142.0 (s), 145.7 (s),
Hz). IR (ATR): 휈̃
= 3524 (br), 1601 cm-1. HRMS (ESI+) calcd for C23H17F2O2
[M + H+] 363.1197, found 363.1191.
2-(3,4,5-Triphenylfuran-2-yl)phenol (7j): White solid (73 mg, 75%). Rf:
0.55 (hexanes/ethyl acetate, 5:1). Mp 140-141 °C. 1H NMR (500 MHz,
CDCl3): δ = 6.65 (s, 1H), 6.75-6.80 (m, 1H), 6.96-7.00 (m, 1H), 7.05-7.09
(m, 2H), 7.12-7.31 (m, 13H), 7.43-7.47 (m, 2H). 13C NMR (125 MHz,
CDCl3): δ = 116.4 (s), 117.1 (d), 120.2 (d), 124.3 (s), 125.76 (s), 125.84
(d), 127.4 (d), 127.7 (d), 128.5 (d), 128.6 (d), 129.2 (d), 129.9 (d), 130.0
(d), 130.2 (s), 130.3 (d), 131.9 (s), 132.6 (s), 146.0 (s), 148.2 (s), 153.4 (s).
159.3 (s), 159.4 (s), 169.6 (s), 174.1 (s), 195.4 (s). IR (ATR): 휈̃ = 1699,
1614, 1591, 1508 cm−1. HRMS (ESI+) calcd for C31H27O5 [M + H+]
479.1858, found 479.1843.
IR (ATR): 휈
̃
= 3510 (br), 1603, 1578 cm-1. HRMS (ESI+) calcd for C28H21O2
Isomerization of cis-3 with DBU and subsequent desilylation. A
solution of cis-3g (104 mg, 0.25 mmol) and DBU (10 mg) in THF (5 mL)
was stirred at 50 ºC for 24 h. To a solution was added 1 M HCl aq (5 mL)
at 50 ºC, and then the solution was stirred at this temperature for 2 h. The
mixture was neutralized with sat. NaHCO3 aq and extracted with ethyl
acetate (10 mL × 3). After removal of the solvent in vacuo, the residue was
purified by column chromatography on silica gel (hexanes-EtOAc) to give
trans-5g (48 mg, 0.14 mmol) and cis-5g (26 mg, 0.075 mmol) in 86%
combined yield (trans:cis = 65:35).
[M + H+] 389.1542, found 389.1534.
2-(4,5-Bis(4-fluorophenyl)-3-phenylfuran-2-yl)phenol (7k): Red solid
(53 mg, 50%). Rf: 0.5 (hexanes/ethyl acetate, 5:1). Mp 168-169 °C. 1H
NMR (500 MHz, CDCl3): δ = 6.44 (brs, 1H), 6.77-6.81 (m, 1H), 6.95-7.01
(m, 5H), 7.03-7.07 (m, 2H), 7.09-7.16 (m, 3H), 7.20-7.27 (m, 4H), 7.38-
7.43 (m, 2H). 13C NMR (125 MHz, CDCl3): δ = 115.7 (d, JCCF = 21.6 Hz),
115.8 (d, JCCF = 21.6 Hz), 116.3 (s), 117.2 (d), 120.3 (d), 122.9 (s), 125.6
(s), 126.4 (s, JCCCCF = 3.6 Hz), 127.6 (d), 127.8 (d, JCCCF = 8.4 Hz), 128.4
(d, JCCCCF = 3.6 Hz), 128.6 (d), 129.3 (d), 129.9 (d), 130.1 (d), 131.6 (s),
(2R*,3S*)-2-(Hydroxydiphenylmethyl)-3-methylchroman-4-one (trans-
5g): White solid (48 mg, 56%). Rf: 0.4 (hexanes/ethyl acetate, 5:1). Mp
160-162 ºC. 1H NMR (500 MHz, CDCl3): δ = 1.13 (d, 3H, J = 7.5 Hz), 2.43
(brs, 1H), 2.82-2.87 (m, 1H), 5.23 (d, 1H, J = 4.6 Hz), 6.76-6.80 (m, 1H),
6.95-6.99 (m, 1H), 7.21-7.28 (m, 3H), 7.29-7.36 (m, 4H), 7.37-7.42 (m, 2H),
7.52-7.56 (m, 2H), 7.80-7.84 (m, 1H). 13C NMR (125 MHz, CDCl3): δ = 15.9
(q), 40.8 (d), 81.7 (s), 85.7 (d), 117.2 (d), 120.0 (s), 121.2 (d), 125.8 (d),
126.7 (d), 127.3 (d), 128.2 (d), 128.5 (d), 135.6 (d), 143.3 (s), 144.4 (s),
132.0 (d, JCCCF = 7.8 Hz), 146.1 (s), 147.6 (s), 153.4 (s), 162.2 (s, JCF
=
247.1 Hz), 163.3 (s, JCF = 248.3 Hz). IR (ATR): 휈 = 3530 (br), 1609, 1597,
̃
1574, 1514 cm−1. HRMS (ESI+) calcd for C28H19F2O2 [M + H+] 425.1353,
found 425.1345.
4-Methoxy-2-(3,4,5-triphenylfuran-2-yl)phenol (7n): White solid (64 mg,
61%). Rf: 0.5 (hexanes/ethyl acetate, 5:1). Mp 146-147 ºC. 1H NMR (500
This article is protected by copyright. All rights reserved.

10.1002/ejoc.201900519
European Journal of Organic Chemistry
FULL PAPER
159.5 (s), 194.9 (s). IR (ATR): 휈
̃
= 3474, 1686, 1609 cm-1. HRMS (ESI+)
191.0 (s). IR (ATR): 휈
̃
= 3311 (br), 1674, 1618 cm−1. HRMS (ESI+) calcd
calcd for C23H21O3 [M + H+] 345.1491, found 345.1484.
for C29H25O4 [M + H+] 437.1753, found 437.1743.
(2R*,3S*)-2-(bis(4-fluorophenyl)(hydroxy)methyl)-3-methylchroman-
4-one (trans-5h): White solid (56 mg, 59%). Rf: 0.45 (hexanes/ethyl
acetate, 5:1). Mp 170-171 ºC. 1H NMR (500 MHz, CDCl3): δ = 1.13 (d, 3H,
J = 7.5 Hz), 2.42 (brs, 1H), 2.79-2.85 (m, 1H), 5.13 (d, 1H, J = 5.0 Hz),
6.78 (d, 1H, J = 8.5 Hz), 6.96-7.05 (m, 5H), 7.32-7.44 (m, 3H), 7.46-7.52
(m, 2H), 7.79-7.83 (m, 1H). 13C NMR (125 MHz, CDCl3): δ = 15.7 (q), 40.8
(d), 80.8 (s), 85.6 (d), 115.0 (d, JCCF = 21.0 Hz), 115.4 (d, JCCF = 21.6 Hz),
117.1 (d), 120.0 (s), 121.4 (d), 126.8 (d), 127.8 (d, JCCCF = 8.4 Hz), 128.7
(d, JCCCF = 8.4 Hz), 135.7 (d), 139.2 (s, JCCCCF = 3.6 Hz), 139.9 (s, JCCCCF
= 3.0 Hz), 159.4 (s), 161.92 (s, JCF = 247.1 Hz), 161.94 (s, JCF = 247.1 Hz),
(2R*,3S*)-2-(Hydroxydiphenylmethyl)-7-methoxy-3-phenylchroman-
4-one (trans-5o): White solid. Rf: 0.15 (hexanes/ethyl acetate, 5:1). Mp
240-241 °C (recryst from ethyl acetate). 1H NMR (500 MHz, CDCl3): δ =
2.35 (brs, 1H), 3.79 (s, 3H), 3.97 (d, 1H, J = 2.4 Hz), 5.68 (d, 1H, J = 2.4
Hz), 6.27 (d, 1H, J = 2.3 Hz), 6.52 (dd, 1H, J = 2.3, 8.6 Hz), 7.11-7.17 (m,
2H), 7.19-7.36 (m, 9H), 7.37-7.42 (m, 2H), 7.51-7.56 (m, 2H), 7.74 (d, 1H,
J = 8.6 Hz). 13C NMR (125 MHz, CDCl3): δ = 50.8 (d), 55.6 (q), 82.4 (s),
85.6 (d), 100.6 (d), 109.4 (d), 114.2 (s), 126.0 (d), 126.8 (d), 127.4 (d),
127.5 (d), 127.9 (d), 128.2 (d), 128.6 (d), 128.7 (d), 128.9 (d), 138.4 (s),
143.0 (s), 144.0 (s), 161.5 (s), 166.0 (s), 189.6 (s). IR (ATR): 휈̃ = 3246 (br),
1668, 1609, 1582 cm−1. HRMS (ESI+) calcd for C29H25O4 [M + H+]
437.1753, found 437.1745.
194.5 (s). IR (ATR): 휈
̃
= 3420 (br), 1674, 1605 cm-1. HRMS (ESI+) calcd
for C23H19F2O3 [M + H+] 381.1302, found 381.1293.
(2R*,3S*)-2-(5-Hydroxy-5H-dibenzo[a,d][7]annulen-5-yl)-3-
(2R*,3S*)-2-(Hydroxydiphenylmethyl)-7-methoxy-3-(4-
methylchroman-4-one (trans-5i): Colorless paste (57 mg, 62%). Rf: 0.4
(hexanes/ethyl acetate, 5:1). 1H NMR (500 MHz, CDCl3): δ = 0.74 (d, 3H,
J = 7.5 Hz), 2.62-2.69 (m, 1H), 3.06 (s, 1H), 5.16 (d, 1H, J = 6.6 Hz), 6.42
(d, 1H, J = 8.3 Hz), 6.92-6.96 (m, 1H), 6.98 (d, 1H, J = 11.6 Hz), 7.07 (d,
1H, J = 11.6 Hz), 7.28-7.36 (m, 4H), 7.38-7.41 (m, 1H), 7.42-7.48 (m, 2H),
7.71 (d, 1H, J = 8.0 Hz), 7.78-7.81 (m, 1H), 7.96 (d, 1H, J = 8.1 Hz). 13C
NMR (125 MHz, CDCl3): δ = 13.8 (q), 41.4 (d), 80.0 (d), 80.4 (s), 117.2 (d),
119.9 (s), 121.2 (d), 123.8 (d), 124.8 (d), 126.8 (d), 126.9 (d), 127.4 (d),
128.9 (d), 129.3 (d), 129.4 (d), 129.5 (d), 131.2 (d), 132.0 (d), 132.2 (s),
132.5 (s), 135.4 (d), 137.7 (s), 140.3 (s), 160.0 (s), 194.9 (s). IR (ATR): 휈
= 3547 (br), 1686, 1599, 1582 cm-1. HRMS (ESI+) calcd for C25H21O3 [M +
H+] 369.1491, found 369.1484.
methoxyphenyl)chroman-4-one (trans-5p): White solid (93 mg, 80%).
Rf: 0.55 (hexanes/ethyl acetate, 2:1). Mp 177-178 °C. 1H NMR (500 MHz,
CDCl3): δ = 2.35 (brs, 1H), 3.73 (s, 3H), 3.78 (s, 3H), 3.92 (d, 1H, J = 2.6
Hz), 5.64 (d, 1H, J = 2.6 Hz), 6.26 (d, 1H, J = 2.4 Hz), 6.52 (dd, 1H, J =
2.4, 8.8 Hz), 6.73-6.78 (m, 2H), 7.03-7.08 (m, 2H), 7.20-7.36 (m, 6H), 7.36-
7.41 (m, 2H), 7.51-7.56 (m, 2H), 7.73 (d, 1H, J = 8.8 Hz). 13C NMR (125
MHz, CDCl3): δ = 50.1 (d), 55.2 (q), 55.5 (q), 82.3 (s), 85.7 (d), 100.6 (d),
109.3 (d), 114.1 (s), 114.3 (d), 126.0 (d), 126.8 (d), 127.35 (d), 127.39 (d),
128.2 (d), 128.5 (d), 128.7 (d), 129.0 (d), 130.2 (s), 143.1 (s), 144.0 (s),
̃
158.8 (s), 161.5 (s), 165.9 (s), 189.9 (s). IR (ATR): 휈̃ = 3258 (br), 1668,
1609, 1580, 1508 cm−1. HRMS (ESI+) calcd for C30H27O4 [M + H+]
467.1858, found 467.1846.
(2R*,3S*)-2-(Hydroxydiphenylmethyl)-3-phenylchroman-4-one (trans-
5j): White solid (70 mg, 69%). Rf: 0.4 (hexanes/ethyl acetate, 5:1). Mp 178-
(2R*,3S*)-2-(Hydroxydiphenylmethyl)-5,7-dimethoxy-3-(4-
methoxyphenyl)chroman-4-one (trans-5q): White solid (70 mg, 56%).
Rf: 0.35 (hexanes/ethyl acetate, 1:1). Mp 126-127 °C. 1H NMR (500 MHz,
CDCl3): δ = 2.39 (brs, 1H), 3.73 (s, 3H), 3.77 (s, 3H), 3.79 (s, 3H), 3.83 (d,
1H, J = 2.6 Hz), 5.58 (d, 1H, J = 2.6 Hz), 5.91-5.93 (m, 1H), 6.00-6.01 (m,
1H), 6.71-6.76 (m, 2H), 7.05-7.09 (m, 2H), 7.18-7.39 (m, 9H), 7.52-7.57
(m, 1H). 13C NMR (125 MHz, CDCl3): δ = 51.4 (d), 55.2 (q), 55.5 (q), 56.0
(q), 82.2 (s), 85.0 (d), 92.6 (d), 93.1 (d), 114.1 (d), 125.9 (d), 126.7 (d),
127.3 (d), 127.8 (d), 128.2 (d), 128.5 (d), 129.0 (d), 130.4 (s), 142.9 (s),
144.3 (s), 158.7 (s), 162.0 (s), 163.0 (s), 165.7 (s), 188.5 (s). IR (ATR): 휈
= 3460 (br), 1732, 1665, 1607, 1576, 1510 cm−1. HRMS (ESI+) calcd for
C31H29O7 [M + H+] 497.1964, found 497.1955.
179 ºC. 1H NMR (500 MHz, CDCl3): δ = 2.35 (s, 1H), 4.03 (d, 1H, J = 2.3
Hz), 5.70 (d, 1H, J = 2.3 Hz) 6.81-6.85 (m, 1H), 6.93-6.98 (m, 1H), 7.14-
7.35 (m, 11H), 7.37-7.44 (m, 3H), 7.50-7.55 (m, 2H), 7.76-7.81 (m, 1H).
13C NMR (125 MHz, CDCl3): δ = 51.0 (d), 82.5 (s), 85.1 (d), 117.3 (d),
120.4 (s), 121.2 (d), 126.0 (d), 126.8 (d), 127.45 (d), 127.48 (d), 127.9 (d),
128.2 (d), 128.6 (d), 128.9 (d), 135.9 (d), 137.9 (s), 143.0 (s), 143.9 (s),
159.7 (s), 190.8 (s). IR (ATR): 휈̃
= 3439 (br), 1672, 1605 cm-1. HRMS
(ESI+) calcd for C28H23O3 [M + H+] 407.1647, found 407.1634.
̃
(2R*,3S*)-2-(Bis(4-fluorophenyl)(hydroxy)methyl)-3-phenylchroman-
4-one (trans-5k): White solid (67 mg, 61%). Rf: 0.35 (hexanes/ethyl
acetate, 5:1). Mp 120-122 °C. 1H NMR (500 MHz, CDCl3): δ = 2.35 (brs,
1H), 4.03 (d, 1H, J = 3.4 Hz), 5.61 (d, 1H, J = 3.4 Hz), 6.85 (d, 1H, J = 8.3
Hz), 6.94-7.03 (m, 5H), 7.10-7.14 (m, 2H), 7.20-7.25 (m, 3H), 7.31-7.36 (m,
2H), 7.42-7.51 (m, 3H), 7.78 (dd 1H, J = 1.7, 7.7 Hz). 13C NMR (125 MHz,
CDCl3): δ = 51.3 (d), 81.5 (s), 85.0 (d), 115.1 (d, JCCF = 21.6 Hz), 115.4 (d,
JCCF = 21.0 Hz), 117.3 (d), 120.3 (s), 121.6 (d), 127.0 (d), 127.6 (d), 128.0
(d, JCCCF = 7.2 Hz), 128.1 (d), 128.8 (d, JCCCF = 8.1 Hz), 129.0 (d), 136.1
(d), 137.3 (s), 138.6 (s, JCCCCF = 2.7 Hz), 139.5 (s, JCCCCF = 3.0 Hz), 159.4
(s), 161.9 (s, JCF = 247.1 Hz), 162.0 (s, JCF = 247.1 Hz), 190.7 (s). IR
Dehydrogenation of 5 with DDQ. To a solution of 5a (66 mg, 0.20 mmol)
in dioxane (5 mL) was added DDQ (57 mg, 0.25 mmol) and TMSCl (0.035
mL, 0.25 mmol), and then the solution was refluxed for 6 h. After removal
of the solvent in vacuo, the residue was purified by column
chromatography on silica gel (hexanes-EtOAc) to give 9a (59 mg, 0.180
mmol) in 90% yield.
2-(Hydroxydiphenylmethyl)-4H-chromen-4-one (9a): White solid (90%).
Rf: 0.4 (hexanes/ethyl acetate, 2:1). Mp 216-217 °C. 1H NMR (500 MHz,
CDCl3): δ = 3.34 (brs, 1H), 6.37 (s, 1H), 7.32-7.44 (m, 12H), 7.62-7.67 (m,
1H), 8.16-8.21 (m, 1H). 13C NMR (125 MHz, CDCl3): δ = 80.5 (s), 111.3
(d), 118.0 (d), 123.6 (s), 125.4 (d), 125.8 (d), 127.6 (d), 128.39 (d), 128.42
(ATR): 휈̃
= 3235 (br), 1676, 1605, 1504 cm−1. HRMS (ESI+) calcd for
C28H21F2O3 [M + H+] 443.1459, found 443.1447.
(2R*,3S*)-2-(Hydroxydiphenylmethyl)-6-methoxy-3-phenylchroman-
4-one (trans-5n): White solid (67 mg, 61%). Rf: 0.3 (hexanes/ethyl acetate,
5:1). Mp 206-207 °C. 1H NMR (500 MHz, CDCl3): δ = 2.36 (brs, 1H), 3.75
(s, 3H), 4.01 (d, 1H, J = 2.4 Hz), 5.65 (d, 1H, J = 2.4 Hz) 6.77 (d, 1H, J =
9.2 Hz), 7.02 (dd, 1H, J = 3.2, 9.2 Hz), 7.13-7.18 (m, 2H), 7.19-7.35 (m,
10H), 7.37-7.41 (m, 2H), 7.50-7.55 (m, 2H). 13C NMR (125 MHz, CDCl3):
δ = 50.8 (d), 55.7 (q), 82.5 (s), 85.0 (d), 107.4 (d), 118.6 (d), 120.2 (s),
125.0 (d), 125.9 (d), 126.8 (d), 127.40 (d), 127.43 (d), 127.5 (d), 127.9 (d),
128.2 (d), 128.6 (d), 128.9 (d), 142.9 (s), 144.0 (s), 153.9 (s), 154.1 (s),
(d), 133.9 (d), 142.3 (s), 156.1 (s), 169.5 (s), 178.5 (s). IR (ATR): 휈̃ = 3177
(br), 1628, 1603 cm−1. HRMS (ESI+) calcd for C22H17O3 [M + H+] 329.1178,
found 329.1172.
2-(Bis(4-fluorophenyl)(hydroxy)methyl)-4H-chromen-4-one
(9b):
White solid (67 mg, 92%). Rf: 0.35 (hexanes/ethyl acetate, 2:1). Mp 173-
174 ºC. 1H NMR (500 MHz, CDCl3): δ = 3.79 (brs, 1H), 6.42 (s, 1H), 7.01-
7.07 (m, 4H), 7.32-7.42 (m, 6H), 7.62-7.67 (m, 1H), 8.13 (dd, 1H, J = 1.4,
This article is protected by copyright. All rights reserved.

10.1002/ejoc.201900519
European Journal of Organic Chemistry
FULL PAPER
7.9 Hz). 13C NMR (125 MHz, CDCl3): δ = 79.5 (s), 110.7 (d), 115.3 (d, JCCF
= 21.3 Hz), 117.9 (d), 123.4 (s), 125.5 (d), 125.8 (d), 129.5 (d, JCCCF = 8.4
Hz), 134.1 (d), 138.3 (s, JCCCCF = 3.0 Hz), 156.0 (s) 162.5 (s, JCF = 248.3
3.3 Hz), 155.0 (s) 162.5 (s, JCF = 248.3 Hz), 179.1 (s). IR (ATR): 휈̃ = 3292
(br), 1616, 1601, 1591, 1584, 1508 cm−1. HRMS (ESI+) calcd for
C23H17F2O3 [M + H+] 379.1146, found 379.1141.
Hz), 169.6 (s), 178.5 (s). IR (ATR): 휈̃ .
= 3196 (br), 1628, 1601, 1508 cm−1
HRMS (ESI+) calcd for C22H15F2O3 [M + H+] 365.0989, found 365.0982.
Conflict of interest
2-(5-Hydroxy-10,11-dihydro-5H-dibenzo[a,d][7]annulen-5-yl)-4H-
chromen-4-one (9c): Colorless paste (35 mg, 50%). Rf: 0.4
(hexanes/ethyl acetate, 2:1). 1H NMR (500 MHz, CDCl3): δ = 2.85-2.93 (m,
2H), 3.17-3.26 (m, 2H), 3.48 (brs, 1H), 6.15 (s, 1H), 7.11-7.14 (m, 2H),
7.20 (d, 1H, J = 8.4 Hz), 7.24-7.35 (m, 5H), 7.53-7.57 (m, 1H), 7.93-7.96
(m, 2H), 8.10 (dd, 1H, J = 1.6, 7.9 Hz). 13C NMR (125 MHz, CDCl3): δ =
32.7 (t), 78.7 (s), 110.4 (d), 118.3 (d), 123.5 (s), 125.4 (d), 125.6 (d), 126.5
(d), 128.5 (d), 130.6 (d), 133.9 (d), 137.8 (s) 139.5 (s), 156.1 (s), 170.8 (s),
The authors declare no conflict of interest.
Keywords: Electroreductive Coupling • Chromones •
Isoflavones • 2-Diarylmethylchromones • Tetrasubstituted
Furans
178.9 (s). IR (ATR): 휈̃
= 3285 (br), 1622, 1591, 1570 cm−1. HRMS (ESI+)
[1]
For recent reviews, see: a) J. Reis, A. Gaspar, N. Milhazes, F. J. Borges,
J. Med. Chem. 2016, 60, 7941-7957; b) A. Gasper, M. J. Matos, J.
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S. Keri, S. Budagumpi, R. K. Pai, R. G. Balakrishna, Eur. J. Med. Chem.
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calcd for C24H19O3 [M + H+] 355.1334, found 355.1328.
2-(5-Hydroxy-5H-dibenzo[a,d][7]annulen-5-yl)-4H-chromen-4-one
(9d): White solid (53 mg, 75%). Rf: 0.35 (hexanes/ethyl acetate, 2:1). Mp
268-269 ºC. 1H NMR (500 MHz, CDCl3): δ = 3.62 (brs, 1H), 5.72 (s, 1H),
6.86 (s, 2H), 7.02 (d, 1H, J = 8.2 Hz), 7.26-7.30 (m, 2H), 7.32-7.39 (m, 4H)
7.47-7.54 (m, 3H), 8.03 (dd, 1H, J = 1.6, 7.9 Hz), 8.07 (d, 1H, J = 8.2 Hz).
13C NMR (125 MHz, CDCl3): δ = 78.3 (s), 109.7 (d), 118.1 (d), 123.3 (s),
123.9 (d), 125.1 (d), 125.3 (d), 127.4 (d), 128.56 (d), 128.60 (d), 131.2 (d),
[2]
For recent reports, see: a) M. A. Ibrahim, N. M. El-Gohary, Tetrahedron
2018, 74, 512-518; b) T. Lepitre, C. Denhez, J. Moncol, M. Othman, A.
M. Lawson, A. Daïch, J. Org. Chem. 2017, 82, 12188-12201; c) J. K.
Matsui, G. A. Molander, Org. Lett. 2017, 19, 436-439; d) A. L. Gerten, L.
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C. Yang, Org. Lett. 2015, 17, 5590-5593; f) J. Liu, Z. Li, P. Tong, Z. Xie,
Y. Zhang, Y. Li, J. Org. Chem. 2015, 80, 1632-1643; g) Q. He, C. M. So,
Z. Bian, T. Hayashi, J. Wang, Chem. Asian J. 2015, 10, 540-543.
a) N. Kise, T. Sakurai. Tetrahedron Lett. 2010, 51, 70-74; b) N. Kise, S.
Isemoto, T. Sakurai, J. Org. Chem. 2011, 76, 9856-9860; c) N. Kise, S.
Isemoto, T. Sakurai, Tetrahedron, 2012, 68, 8805-8816.
132.9 (s), 133.6 (d), 138.5 (s), 155.8 (s) 170.3 (s), 178.9 (s). IR (ATR): 휈̃ =
3348 (br), 1630, 1614, 1593, 1560 cm−1. HRMS (ESI+) calcd for C24H17O3
[M + H+] 353.1178, found 353.1174.
[3]
2-(9-Hydroxy-9H-xanthen-9-yl)-4H-chromen-4-one (9e): White solid (62
mg, 91%). Rf: 0.4 (hexanes/ethyl acetate, 2:1). Mp 235-236 ºC. 1H NMR
(500 MHz, CDCl3): δ = 3.06 (brs, 1H), 7.01 (s, 1H), 7.10-7.17 (m, 3H), 7.21-
7.33 (m, 3H), 7.36-7.41 (m, 2H), 7.46-7.52 (m, 1H), 7.59 (dd, 2H, J = 1.4,
7.9 Hz), 8.12 (dd, 1H, J = 1.5, 8.0 Hz). 13C NMR (125 MHz, CDCl3): δ =
69.1 (s), 107.4 (d), 116.7 (d), 118.1 (d), 118.3 (s), 122.4 (s), 123.4 (s),
123.7 (d), 125.0 (d), 125.5 (d), 127.8 (d), 130.2 (d), 133.5 (d), 150.2 (s),
[4]
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N. Kise, A. Sueyoshi, S. Takeuchi, T. Sakurai, Org. Lett. 2013, 15, 2746-
2749.
a) N. Kise, H. Miyamoto, Y. Hamada, T. Sakurai, Tetrahedron Lett. 2015,
56, 4599-4602; b) N. Kise, Y. Hamada, T. Sakurai, J. Org. Chem. 2016,
81, 5101-5119.
156.1 (s) 170.0 (s), 178.9 (s). IR (ATR): 휈̃ = 3366 (br), 1643, 1601, 1570
cm−1. HRMS (ESI+) calcd for C22H15O4 [M + H+] 343.0970, found 343.0965.
[6]
[7]
N. Kise, Y. Hamada, T. Sakurai, J. Org. Chem. 2016, 81, 11043-11056.
P. Bichovski, T. M. Haas, D. Kratzert, J. Streuff, Chem. Eur. J. 2015, 21,
2339-2342.
2-(Hydroxydiphenylmethyl)-3-methyl-4H-chromen-4-one (9g): White
solid (31 mg, 46%). Rf: 0.15 (hexanes/ethyl acetate, 5:1). Mp 204-205 ºC.
1H NMR (500 MHz, CDCl3): δ = 1.83 (s, 3H), 3.46 (brs, 1H), 7.19 (d, 1H, J
= 8.6 Hz), 7.35-7.39 (m, 11H), 7.56-7.61 (m, 1H), 8.21 (dd, 1H, J = 1.6, 8.0
Hz). 13C NMR (125 MHz, CDCl3): δ = 10.6 (q), 82.3 (s), 117.7 (d), 119.6
(s), 122.0 (s), 124.9 (d), 125.8 (d), 127.5 (d), 128.2 (d), 128.3 (d), 133.4
(d), 143.2 (s) 155.0 (s), 164.3 (s), 179.3 (s). IR (ATR): 휈̃ = 3364 (br), 1611,
1603, 1566 cm−1. HRMS (ESI+) calcd for C23H19O3 [M + H+] 343.1334,
found 343.1331.
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Lou, Q. Wang, K. Wu, P. Wu, Z. Yu, Org. Lett. 2017, 19, 3287-3290; b)
N. M. Chobanov, M. G. Shaibakova, N. R. Popod’ko, L. O. Khafizova U.
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J. Org. Chem. 2016, 81, 11909-11915; d) S. Wang, C. Liu, J. Jia, C. Zha,
M. Xie, N. Zhang, Tetrahedron 2016, 72, 6684-6691; e) S. Hosseyni, Y.
Su, X. Shi, Org. Lett. 2015, 17, 6010-6013; f) S. Mao, X.-Q. Zhu, Y.-R.
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S. Mao, Y.-R. Gao, S.-L. Zhang, D.-D, Guo, Y.-Q. Wang, Eur. J. Org.
Chem. 2015, 876-885.
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Tetrahedron 2004, 60, 967-971.
2-(Bis(4-fluorophenyl)(hydroxy)methyl)-3-methyl-4H-chromen-4-one
(9h): White solid (45 mg, 60%). Rf: 0.45 (hexanes/ethyl acetate, 2:1). Mp
230-231 ºC. 1H NMR (500 MHz, CDCl3): δ = 1.83 (s, 3H), 3.68 (brs, 1H),
7.03-7.09 (m, 4H), 7.14 (d, 1H, J = 8.2 Hz), 7.32-7.37 (m, 5H), 7.55-7.59
(m, 1H), 8.16 (dd, 1H, J = 1.7, 8.0 Hz). 13C NMR (125 MHz, CDCl3): δ =
10.5 (q), 81.6 (s), 115.3 (d, JCCF = 21.3 Hz), 117.6 (d), 119.6 (s), 121.9 (s),
[10] T. Qin, P. Metz, Org. Lett. 2017, 19, 2981-2984.
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2005, 13, 4880-4890.
125.1 (d), 125.9 (d), 129.3 (d, JCCCF = 8.4), 133.5 (d), 139.1 (s, JCCCCF
=
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10.1002/ejoc.201900519
European Journal of Organic Chemistry
FULL PAPER
Entry for the Table of Contents
FULL PAPER
The electroreductive coupling of
chromones with benzophenones in
the presence of TMSCl gave adducts
reacted at the 2-position of chromones
as trimethylsilyl ethers. From 3-
methyl- and 3-phenylchromones, 2,3-
cis-adducts were formed
Naoki Kise,* Hiroaki Nagamine, and
Toshihiko Sakurai,
Page No. – Page No.
Electroreductive Intermolecular
Coupling of Chromones with
Benzophenones: Synthesis of 2-
Diarylmethylchromones and
Tetrasubstituted Furans
predominantly. 2-
Diarylmethylchromones were obtained
by dehydrosiloxylation of the adducts.
Tetrasubstituted furans were also
synthesized from the adducts through
ring-opening products.
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