Direct and selective synthesis of 3-arylphthalides via nickel-catalyzed aryl addition/intramolecular esterification

Article abstract of DOI:10.1016/j.tet.2021.132162

Herein we report a nickel-catalyzed aryl addition/intramolecular esterification in a cascade fashion. Under the combination of commercially available nickel precursor and tridentate ligand, the one pot protocol offers a direct, simple and regioselective approach to access 3-aryl phthalide derivatives from two readily available substrates with good efficiency, broad scope as well as satisfactory functional group compatibility.

Full text of DOI:10.1016/j.tet.2021.132162

Tetrahedron xxx (xxxx) xxx
Contents lists available at ScienceDirect
Tetrahedron
journal homepage: www.elsevier.com/locate/tet
Direct and selective synthesis of 3-arylphthalides via nickel-catalyzed
aryl addition/intramolecular esterification
Qing Qiang 1, Feipeng Liu 1, Zi-Qiang Rong*
Frontiers Science Center for Flexible Electronics (FSCFE), Shaanxi Institute of Flexible Electronics (SIFE) & Shaanxi Institute of Biomedical Materials and
Engineering (SIBME), Northwestern Polytechnical University (NPU), 127 West Youyi Road, Xi'an, 710072, China
a r t i c l e i n f o
a b s t r a c t
Article history:
Herein we report a nickel-catalyzed aryl addition/intramolecular esterification in a cascade fashion.
Under the combination of commercially available nickel precursor and tridentate ligand, the one pot
protocol offers a direct, simple and regioselective approach to access 3-aryl phthalide derivatives from
two readily available substrates with good efficiency, broad scope as well as satisfactory functional group
compatibility.
Received 27 February 2021
Received in revised form
8 April 2021
Accepted 12 April 2021
Available online xxx
© 2021 Elsevier Ltd. All rights reserved.
Keywords:
Nickel catalysis
3-Arylphthalides
Aryl addition
Intramolecular esterification
Cyclization
1. Introduction
reported strategies required the use of pre-functionalized and
advanced substrates, toxic catalyst or long reaction time, thus
Phthalide derivatives are important structural units which are
highly represented in various natural products and biologically
active molecules [1,2]. They also reveal great importance as versa-
tile building blocks for the preparation of more valuable fine
chemicals such as dye intermediates and drugs in material chem-
istry and medicinal chemistry (Fig. 1) [3,4]. And their ubiquitous
pharmaceutical properties have been proven to be high antibac-
terial [5], anticancer [6], and anti-HIV activities [7]. To date, the
conventional route for the synthesis of these valuable scaffolds
often relies on multistep synthetic pathways [8], in which stoi-
chiometric organic and organometallic reagents are needed. In
addition, many catalytic systems involving intramolecular process
or direct transformation of pre-synthesized analogues have also
been realized for the production of phthalides such as oxidative
lactonization [1g], oxidation [9], reduction of phthalaldehydic acids
or phthalic anhydrides [10], nucleophilic addition [11], electrophilic
and nucleophilic aromatic substitution [12], benzannulation/
cycloaddition [13], cyclocarbonylation [14], rearrangement [15],
electrocatalysis [16], photocatalysis [11,17] etc. However, all of these
leading to less efficiency. Therefore, the development of efficient
and economical access to these phthalide derivatives is highly
desirable. To this end, the direct cyclization of two easily available
precursors has received considerable attention, representing the
most distant approach to deliver these valuable five-membered
benzo-fused
The transition metal catalyzed functionalization of the aldehyde
CeH bond provides straightforward and atom-economical
g-butyrolactones.
a
approach to construct complex organic molecules [18,19]. Recent
development on this strategy has successfully extended to produce
phthalide derivatives, and many elegant catalytic systems were
achieved [20,21]. In 2009, Onomura and co-workers developed a
palladium-catalyzed arylation of aldehydes with organoboronic
acids for the synthesis of 3-arylphthalides in high efficiency [22].
Later, Cheng's group reported an aryl addition/intramolecular
esterification to access 3-aryl and 3-alkenyl phthalides via rhodium
catalysis [23]. In 2018, Shishido's group revealed that carboxylate-
directed addition of aromatic CeH bond to aromatic aldehydes
afforded the corresponding phthalides derivatives using ruthenium
catalyst [24]. Furthermore, Ellman and coworkers developed an
efficient rhodium (III)-catalyzed cascade addition and cyclization of
benzimidates with aldehydes, affording phthalides with broad
scope and good functional group tolerance [25]. Very recently, a
* Corresponding author.
E-mail address: iamzqrong@nwpu.edu.cn (Z.-Q. Rong).
These authors contributed equally to this work.
1
https://doi.org/10.1016/j.tet.2021.132162
0040-4020/© 2021 Elsevier Ltd. All rights reserved.
Please cite this article as: Q. Qiang, F. Liu and Z.-Q. Rong, Direct and selective synthesis of 3-arylphthalides via nickel-catalyzed aryl addition/
intramolecular esterification, Tetrahedron, https://doi.org/10.1016/j.tet.2021.132162

Q. Qiang, F. Liu and Z.-Q. Rong
Tetrahedron xxx (xxxx) xxx
phthalide derivatives with good efficiency and satisfactory func-
tional group compatibility (Scheme 1e).
2. Result and discussion
The optimization of this reaction was carried out by employing
the 2-formylphenyl trifluoromethanesulfonate 1a and benzalde-
hyde 2a as substrates under the nickel catalysis (Table 1). To our
delight, it exhibited that Ni(cod)2 could facilitate this trans-
formation with 74% yield by the use of triphos as ligand and 1-
methylpiperidine as base in toluene (entry 1, Table 1). Encour-
aged by this outcome, a series of nickel precursors were firstly
evaluated for the reaction. Nickel catalysts like Ni(PPh3)4 and
Ni(OTf)2 could promote this transformation, while the yields were
not fairly satisfactory (entries 2e3). The [Ni(TMHD)2] (Bis(2,2,6,6-
tetramethyl-3,5-heptanedionato)nickel (II)) and nickelocene cata-
lysts instead of Ni(cod)2 failed to catalyze this reaction (entries
4e5). It might be due to the poor solubility of these two catalysts in
toluene. Further efforts to improve the yield focused on the
screening of more ligands. Several phosphine ligands like dppb,
dcype or Davephos all proved to be much less efficient and only a
trace amount of the product was detected. Subsequently, the effect
of bases was screened and it turned out that 1-methylpiperdine
was still the best base for this cascade process. In contrast to
inorganic bases (see entry 9 and supporting information), the
Fig. 1. Selected phthalide natural products.
rhenium-catalyzed distinct annulation of benzamides and alde-
hydes to afford phthalide derivates with behaved superior func-
tional group tolerance was initiated by Wang and co-workers
(Scheme 1c) [26]. Among these reported strategies, rare transition
metal such as palladium, rhodium, ruthenium, or rhenium is
necessary for these protocols, while very limited examples on base
metal catalysis have been realized. In 2004, Cheng and co-workers
reported a highly chemoselective cyclization of o-halobenzoates
with aldehydes to afford substituted phthalides by utilizing
[NiBr2(dppe)] as catalyst, in which stoichiometric zinc powers as
reductant are needed (Scheme 1d) [27]. In view of this, the devel-
opment of a novel and facile approach for the preparation of
phthalide derivatives from easily available starting materials re-
mains an important goal. Here, we describe a nickel-catalyzed aryl
addition/intramolecular esterification, delivering the desired
Table 1
Selected results of screening the optimal conditions.
Entry
Variation
Yield %b
1
2
3
4
5
6
None
74 (70c)
37
12
ND
ND
7
Ni(PPh3)4 instead of Ni(cod)2
Ni(OTf)2 instead of Ni(cod)2
[Ni(TMHD)2] instead of Ni(cod)2
Nickelocene instead of Ni(cod)2
dppb instead of triphos
7
8
9
10
11
12
13
14
15
16
dcype instead of triphos
<5
ND
<5
48
42
49
44
27
47
35
Davephos instead of triphos
K2CO3 instead of 1-methylpiperidine
TMP instead of 1-methylpiperidine
DABCO instead of 1-methylpiperidine
Et3N instead of 1-methylpiperidine
TMEDA instead of 1-methylpiperidine
DME instead of Ph-Me
Ph-F instead of Ph-Me
Ph-CF3 instead of Ph-Me
Reaction.
a: 2-formylphenyl trifluoromethanesulfonate (76.3 mg, 0.3 mmol), benzaldehyde
(79.6 mg, 0.75 mmol), nickel precursor (10 mol%), ligand (10 mol%), base (2.0 equiv.)
in dry solvent (0.17 M), 110 ꢀC, 24 h, under N2.
b
NMR yield was given with 1,1,2,2-tetrachloroethane as the internal standard.
c
Isolated yield. DABCO ¼ 1,4-Diazabicyclooctane; triethylenediamine, TMEDA ¼
N,N,N0,N0-Tetramethylethylenediamine, TMP
DME ¼ Dimethoxyethane, cod ¼ cyclooctadiene, OTf ¼ trifluoromethanesulfonate.
¼
2,2,6,6-Tetramethylpiperidine,
Scheme 1. Strategies for the synthesis of phthalide derivatives.
2

Q. Qiang, F. Liu and Z.-Q. Rong
Tetrahedron xxx (xxxx) xxx
reaction could deliver the desired product by taking organic bases
such as Et3N, DABCO and TMEDA, albeit with lower yields (entries
10e13). On the basis of the screening of ligands and bases, the
investigation of various solvents was then conducted. Among
various solvents screened, toluene was found to be the preferred
choice for this transformation, although other solvents could still
provide the target product with moderate yields (entries 14e16). To
provide expected product with superior efficiency, the tempera-
ture, concentration and reaction time were also examined, while no
positive effect on the yield.
Based on the best optimal reaction conditions, we firstly
investigated the scope of substituted benzaldehydes (Scheme 2).
Generally, various substitutents at the different positions on the
aryl ring that are electron-donating, withdrawing or neutral can be
well tolerated to yield corresponding 3-aryl phthalides 3aa-3at in
uniformly moderate to good yields. It is worth noting that many
functional groups like methoxyl, methylthio, trifluoromethyl,
amide, amine which could behave good tolerance under the stan-
dard conditions. It is gratifying that ortho-substituted benzalde-
hydes successfully engaged in this transformation to convert to
corresponding 3-phenyl phthalides (3 al-3ao), however, morpho-
line substitutent proved to be too sterically hindered and lower
yield was obtained for 3ap. Moreover, the reaction of different
meta-substituted benzaldehydes with 2-formylphenyl tri-
fluoromethanesulfonate 1a could take place to deliver 3aq-3at in
good to excellent yields. Delightfully, subjecting 2-furaldehyde 2u
to the standard condition led to the desired product 3au in 40%
yield, which further expanded the substrate scope of this cyclo-
addition reaction.
Next, the scope and generality of o-triflatebenzaldehydes were
evaluated (Scheme 3). As it turned out, the standard reaction
conditions delivered 3-arylphthalides 3ba-3ma in good yield and
again excellent selectivity. Nonetheless, attempts to enable this
reaction with electron-withdrawing substitutents at the different
positions on the aryl ring remain a limitation yet, showing low
efficiency (for details, see supporting information). Gratifyingly,
sterically hindered substrates, such as 3g and 3i, showed good
reactivity. However, 3-phenyl phthalide with fluoro group 3ha was
isolated in low yield probably due to electron-withdrawing effect
and enhanced steric hindrance. Moreover, to demonstrate the
synthetic potential of this transformation, a more complex o-tri-
flate arylaldehyde 1m derived from natural product estrone was
subjected to the optimal conditions, producing the corresponding
3ma in 45% yield.
On the basis of the previous reports [28], a plausible reaction
mechanism is proposed as shown in Scheme 4. Initially, the
oxidative addition of a nickel (0) into the weak CꢁX bond generates
the active intermediate I, which can further occur aryl addition
with aromatic aldehyde to afford II. And then corresponding nickel
Scheme 2. Nickel-catalyzed aryl addition/intramolecular esterification of 2-
formylphenyl trifluoromethanesulfonate with various substituted benzaldehydesa.
Scheme
3. Substrates
scope
of
substituted
2-formylphenyl
trifluoromethanesulfonatesa.
3

Q. Qiang, F. Liu and Z.-Q. Rong
Tetrahedron xxx (xxxx) xxx
3.2.1. 3-Phenylisobenzofuran-1(3H)-one (3aa)
White solid; Yield: 43.5 mg, 69%. 1H NMR (500 MHz, CDCl3)
d
7.99e7.95 (m, 1H), 7.69e7.64 (m, 1H), 7.59e7.54 (m, 1H),
7.43e7.35 (m, 4H), 7.31e7.28 (m, 2H), 6.42 (s, 1H). 13C NMR
(126 MHz, CDCl3)
d 170.6, 149.7, 136.5, 134.4, 129.4, 129.3, 129.0,
127.0, 125.6, 125.6, 122.9, 82.8.
3.2.2. 3-(p-tolyl)isobenzofuran-1(3H)-one (3ab)
White solid; Yield: 38.1 mg, 56%. 1H NMR (500 MHz, CDCl3)
d
7.97 (d, J ¼ 7.6 Hz, 1H), 7.68e7.63 (m, 1H), 7.58e7.53 (m, 1H), 7.34
(d, J ¼ 6.8 Hz, 1H), 7.22e7.15 (m, 4H), 6.39 (s, 1H), 2.36 (s, 3H). 13
C
NMR (126 MHz, CDCl3)
d 170.6, 149.9, 139.4, 134.3, 133.4, 129.7,
129.3, 127.1, 125.7, 125.6, 122.9, 82.8, 21.2.
3.2.3. 3-(4-isobutylphenyl)isobenzofuran-1(3H)-one (3ac)
White solid; Yield: 38.3 mg, 48%; Melting point: 47e49 ꢀC. 1H
NMR (500 MHz, CDCl3)
d
7.98 (d, J ¼ 7.6 Hz, 1H), 7.68e7.64 (m, 1H),
7.58 (t, J ¼ 7.5 Hz, 1H), 7.36 (d, J ¼ 7.6 Hz, 1H), 7.21e7.15 (m, 4H), 6.41
(s, 1H), 2.49 (d, J ¼ 7.2 Hz, 2H), 1.92e1.82 (m, 1H), 0.91 (d, J ¼ 6.6 Hz,
Scheme 4. Proposed mechanism.
6H). 13C NMR (126 MHz, CDCl3)
d 170.6, 149.8, 143.2, 134.3, 133.6,
129.7, 129.3, 127.0, 125.8, 125.6, 123.0, 82.8, 45.1, 30.2, 22.3. HRMS
alkoxide species III is generated through one more insertion of the
CeO bond. Subsequent -H elimination leads to the formation of
(ESI): Calculated for C18H19O2 (M þ Hþ): 267.1380, found: 267.1377.
p
b
desired 3-phenylphthalides product 3aa with release of the Ni
catalyst IV. Further base assisted elimination of HX from nickel (II)
complex IV regenerates the active Ni(0) catalyst and complete the
catalytic cycle.
3.2.4. 3-([1,10-biphenyl]-4-yl)isobenzofuran-1(3H)-one (3ad)
White solid; Yield: 43.1 mg, 50%. 1H NMR (500 MHz, CDCl3)
d
8.01 (d, J ¼ 7.7 Hz, 1H), 7.71e7.67 (m, 1H), 7.65e7.57 (m, 5H),
7.48e7.45 (m, 2H), 7.43e7.36 (m, 4H), 6.48 (s, 1H). 13C NMR
(126 MHz, CDCl3) 170.5, 149.6, 142.4, 140.3, 135.3, 134.4, 129.4,
In summary, we have exploited a nickel-catalyzed aryl addition/
intramolecular esterification in a cascade fashion. Under the com-
bination of commercially available nickel precursor and tridentate
ligand, two easily available substrates are efficiently converted to
the corresponding 3-aryl phthalide derivatives with good effi-
ciency, broad scope as well as functional group compatibility.
Current efforts towards further extension of this catatlytic system
to access more functionalized molecules and the development of
chiral catalytic system to promote asymmetric transformations is
under going.
d
128.9, 127.8, 127.7, 127.5, 127.2, 125.8, 125.7, 122.9, 82.5.
3.2.5. 3-(4-fluorophenyl)isobenzofuran-1(3H)-one (3ae)
White solid; Yield: 33.1 mg, 48%. 1H NMR (500 MHz, CDCl3)
d
7.98 (d, J ¼ 7.7 Hz, 1H), 7.68 (t, J ¼ 7.5 Hz, 1H), 7.59 (t, J ¼ 7.5 Hz,
1H), 7.34 (d, J ¼ 7.7 Hz, 1H), 7.28e7.25 (m, 2H), 7.10e7.06 (m, 2H),
6.41 (s, 1H). 13C NMR (126 MHz, CDCl3)
170.3, 163.2 (d,
d
J ¼ 249.0 Hz), 149.4, 134.5, 132.3 (d, J ¼ 3.5 Hz), 129.6, 129.1 (d,
J ¼ 8.3 Hz), 125.7, 125.7, 122.9, 116.0 (d, J ¼ 22.0 Hz), 82.0.19F NMR
3. Experimental section
(471 MHz, CDCl3)
d
ꢁ111.7.
3.1. General procedure
3.2.6. 3-(4-chlorophenyl)isobenzofuran-1(3H)-one (3af)
White solid; Yield: 40.2 mg, 55%. 1H NMR (500 MHz, CDCl3)
Chemicals were either purchased or purified by standard tech-
niques without special instructions [1]. H NMR and 13C NMR
spectra were measured on a 500 MHz Bruker spectrometer (1H
500 MHz, 13C 126 MHz), using CDCl3 as the solvent with tetrame-
thylsilane (TMS) as the internal standard at room temperature.
d
7.98 (d, J ¼ 7.6 Hz, 1H), 7.68 (t, J ¼ 7.5 Hz, 1H), 7.59 (t, J ¼ 7.5 Hz,
1H), 7.39e7.32 (m, 3H), 7.25e7.22 (m, 2H), 6.40 (s, 1H). 13C NMR
(126 MHz, CDCl3) 170.3, 149.2, 135.3, 135.0, 134.5, 129.6, 129.3,
d
128.4, 125.8, 125.6, 122.8, 81.9.
Chemical shifts (d) are given in parts per million relative to TMS, the
coupling constants J are given in hertz. Column chromatography
was performed using EM Silica gel 60 (300e400 mesh).
3.2.7. 3-(4-(trifluoromethyl)phenyl)isobenzofuran-1(3H)-one (3ag)
White solid; Yield: 41.4 mg, 50%. 1H NMR (500 MHz, CDCl3)
d
8.00 (d, J ¼ 7.6 Hz, 1H), 7.71e7.66 (m, 3H), 7.60 (t, J ¼ 7.5 Hz, 1H),
7.46 (d, J ¼ 8.0 Hz, 2H), 7.37 (d, J ¼ 7.7 Hz, 1H), 6.48 (s, 1H). 13C NMR
3.2. Typical experiment procedure for nickel-catalyzed annulation
of aryl addition/intramolecular esterification
(126 MHz, CDCl3)
d
170.1, 149.0, 140.5, 134.6, 131.5 (q, J ¼ 33.0 Hz),
129.8, 127.1, 126.1 (q, J ¼ 3.6 Hz), 125.3, 123.2 (q, J ¼ 274.2 Hz), 122.7,
81.6.19F NMR (471 MHz, CDCl3)
d
ꢁ62.8.
A flame-dried 15.0 mL vial were charged with 2-formylaryl tri-
fluoromethanesulfonate 1 (0.3 mmol, 1.0 equiv.) and benzaldehyde
2 (0.6 mmol, 2.0 equiv.). The vial was directly transferred into a
nitrogen-filled glovebox without cap. Then, Ni(cod)2 (8.3 mg,
0.03 mmol, 10 mol%), triphos (18.7 mg, 0.03 mmol, 10 mol%), 1-
methylpiperidine (59.6 mg, 0.6 mmol, 2.0 equiv.) and 1.8 mL dry
toluene were added. The vial was tightly sealed, transferred out of
glovebox and stirred at 110 ꢀC for 24 h. The reaction mixture was
filtered through Celite and the solvent evaporated in vacuo to give
the crude product, which was purified by flash chromatography to
give the desired product 3.
3.2.8. N-(4-(3-oxo-1,3-dihydroisobenzofuran-1-yl)phenyl)
acetamide (3ah)
White solid; Yield: 58.1 mg, 73%. Melting point: 202e205 ꢀC. 1H
NMR (500 MHz, DMSO‑d6)
d
10.05 (s, 1H), 7.92 (d, J ¼ 7.6 Hz, 1H),
7.82e7.74 (q, J ¼ 6.9 Hz, 1H), 7.66e7.60 (m, 3H), 7.45e7.42 (m, 1H),
7.24e7.21 (m, 2H), 6.66 (s, 1H), 2.05 (s, 3H). 13C NMR (126 MHz,
DMSO‑d6)
d 170.4, 169.0, 150.4, 140.5, 135.2, 131.5, 129.9, 128.1,
125.5, 125.3, 123.7, 119.7, 82.4, 24.5. HRMS(ESI): Calculated for
C
16H14NO3(M þ Hþ): 268.0968, found: 268.0954.
4

Q. Qiang, F. Liu and Z.-Q. Rong
Tetrahedron xxx (xxxx) xxx
3.2.9. 3-(4-methoxyphenyl)isobenzofuran-1(3H)-one (3ai)
1H), 7.57 (t, J ¼ 7.5 Hz, 1H), 7.42e7.39 (m, 1H), 7.30e7.26 (m, 2H),
7.10 (t, J ¼ 7.4 Hz, 1H), 6.97 (s, 1H), 6.94 (d, J ¼ 7.7 Hz, 1H), 3.80e3.73
(m, 4H), 3.09e3.05 (m, 2H), 2.92e2.84 (m, 2H). 13C NMR (126 MHz,
White solid; Yield: 35.7 mg, 50%. 1H NMR (500 MHz, CDCl3)
d
7.99e7.96 (m,1H), 7.69e7.65 (m,1H), 7.59e7.55 (m,1H), 7.35e7.31
(m, 1H), 7.22e7.17 (m, 2H), 6.94e6.88 (m, 2H), 6.39 (s, 1H), 3.82 (s,
3H). 13C NMR (126 MHz, CDCl3)
170.5, 160.5, 149.8, 134.3, 129.3,
CDCl3)
d 171.0, 153.0, 150.5, 134.1, 132.1, 130.7, 129.3, 129.1, 126.6,
d
125.5, 125.3, 122.9, 122.0, 79.5, 67.3, 53.9. HRMS (ESI): Calculated
128.8, 128.3, 126.0, 125.6, 123.0, 114.4, 82.8, 55.4.
for C18H18NO (M þ Hþ): 296.1281, found: 296.1278.
3.2.10. 3-(4-(methylthio)phenyl)isobenzofuran-1(3H)-one (3aj)
3.2.17. 3-(m-tolyl)isobenzofuran-1(3H)-one (3aq)
White solid; Yield: 42.9 mg, 560%. Melting point: 124e128 ꢀC.
White solid; Yield: 45.1 mg, 67%. 1H NMR (500 MHz, CDCl3)
1H NMR (500 MHz, CDCl3)
1H), 7.56 (t, J ¼ 7.5 Hz, 1H), 7.33 (d, J ¼ 7.7 Hz, 1H), 7.26e7.22 (m,
d
7.98e7.94 (m, 1H), 7.66 (t, J ¼ 7.5 Hz,
d
7.98 (d, J ¼ 7.6 Hz, 1H), 7.68e7.64 (m, 1H), 7.57 (t, J ¼ 7.5 Hz, 1H),
7.36 (d, J ¼ 7.7 Hz, 1H), 7.29 (t, J ¼ 7.6 Hz, 1H), 7.20 (d, J ¼ 7.6 Hz, 1H),
2H), 7.21e7.16 (m, 2H), 6.38 (s, 1H), 2.47 (s, 3H). 13C NMR (126 MHz,
7.14e7.06 (m, 2H), 6.39 (s, 1H), 2.35 (s, 3H). 13C NMR (126 MHz,
CDCl3)
d
170.5, 149.6, 140.4, 134.4, 132.9, 129.4, 127.62 126.6, 125.7,
CDCl3) d 170.6, 149.9, 138.9, 136.4, 134.3, 130.1, 129.3, 128.9, 127.5,
125.6, 122.9, 82.5, 15.5. HRMS (ESI): Calculated for C15H13O2S
125.6, 125.6, 124.1, 122.9, 82.8, 21.4.
(M þ Hþ): 257.0631, found: 257.0629.
3.2.18. 3-(3-fluorophenyl)isobenzofuran-1(3H)-one (3ar)
3.2.11. 3-(4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenyl)
isobenzofuran-1(3H)-one (3ak)
White solid; Yield: 56.2 mg, 82%. 1H NMR (500 MHz, CDCl3)
d
7.99 (d, J ¼ 7.7 Hz, 1H), 7.69 (t, J ¼ 7.5 Hz, 1H), 7.60 (t, J ¼ 7.5 Hz,
White solid; Yield: 54.7 mg, 54%. Melting point: 172e176 ꢀC. 1H
1H), 7.41e7.36 (m, 2H), 7.14 (d, J ¼ 7.7 Hz, 1H), 7.11e7.07 (m, 1H),
NMR (500 MHz, CDCl3)
2H), 7.63 (d, J ¼ 7.5 Hz, 1H), 7.55 (t, J ¼ 7.5 Hz, 1H), 7.31 (t, J ¼ 8.1 Hz,
3H), 6.42 (s, 1H), 1.35 (s, 12H). 13C NMR (126 MHz, CDCl3)
170.6,
d
7.97 (d, J ¼ 7.6 Hz, 1H), 7.84 (d, J ¼ 7.7 Hz,
7.00 (d, J ¼ 9.4 Hz,1H), 6.41 (s,1H). 13C NMR (126 MHz, CDCl3)
d 170,
162.9 (d, J ¼ 248.3 Hz), 149.1, 139.0 (d, J ¼ 7.3 Hz), 134.5, 130.7 (d,
J ¼ 8.3 Hz), 129.7, 125.9, 125.4, 122.8, 122.6 (d, J ¼ 2.8 Hz), 116.3 (d,
J ¼ 21.1 Hz), 113.9 (d, J ¼ 22.9 Hz), 81.7.19F NMR (471 MHz, CDCl3)
d
149.7, 139.4, 135.4, 134.4, 129.4, 126.0, 125.7, 125.4, 122.8, 84.0, 82.6,
24.9, 24.8. HRMS (ESI): Calculated for C20H21BO4Na (M þ Naþ):
359.1425, found: 359.1422.
d
ꢁ111.5.
3.2.19. 3-(3-chlorophenyl)isobenzofuran-1(3H)-one (3as)
3.2.12. 3-(o-tolyl)isobenzofuran-1(3H)-one (3al)
White solid; Yield: 48.5 mg, 70%. 1H NMR (500 MHz, CDCl3)
White solid; Yield: 35.4 mg, 53%. 1H NMR (500 MHz, CDCl3)
d
7.98 (d, J ¼ 7.7 Hz, 1H), 7.69 (t, J ¼ 7.5 Hz, 1H), 7.59 (t, J ¼ 7.5 Hz,
1H), 7.38e7.33 (m, 3H), 7.28 (t, J ¼ 2.0 Hz, 1H), 7.23e7.20 (m, 1H),
6.38 (s, 1H). 13C NMR (126 MHz, CDCl3)
170.2, 149.1, 138.5, 135.0,
d
7.99 (d, J ¼ 7.6 Hz, 1H), 7.69 (t, J ¼ 7.5 Hz, 1H), 7.59 (t, J ¼ 7.5 Hz,
1H), 7.36 (d, J ¼ 7.6 Hz, 1H), 7.31e7.26 (m, 2H), 7.17e7.13 (m, 1H),
d
6.94 (d, J ¼ 7.7 Hz, 1H), 6.70 (s, 1H), 2.52 (s, 3H). 13C NMR (126 MHz,
134.6, 130.4, 129.7, 129.5, 127.0, 125.9, 125.4, 125.1, 122.8, 81.7.
CDCl3)
d 170.7, 149.3, 137.2, 134.2, 134.1, 131.2, 129.4, 129.4, 127.3,
127.0, 126.5, 125.8, 123.1, 80.6, 19.4.
3.2.20. 3-(3-methoxyphenyl)isobenzofuran-1(3H)-one (3at)
White solid; Yield: 47.7 mg, 66%. 1H NMR (500 MHz, CDCl3)
3.2.13. 3-(2-fluorophenyl)isobenzofuran-1(3H)-one (3am)
d
7.96 (d, J ¼ 7.6 Hz, 1H), 7.67e7.64 (m, 1H), 7.56 (t, J ¼ 7.5 Hz, 1H),
White solid; Yield: 40.1 mg, 58%. 1H NMR (500 MHz, CDCl3)
7.37 (d, J ¼ 7.7,1H), 7.31 (t, J ¼ 7.9 Hz,1H), 6.94e6.87 (m, 2H), 6.80 (t,
d
7.96 (d, J ¼ 7.7 Hz,1H), 7.67 (t, J ¼ 7.5 Hz,1H), 7.57 (t, J ¼ 7.5 Hz,1H),
7.45 (d, J ¼ 7.8 Hz, 1H), 7.39e7.32 (m, 1H), 7.19e7.09 (m, 3H), 6.75 (s,
1H). 13C NMR (126 MHz, CDCl3)
J ¼ 2.1 Hz, 1H), 6.38 (s, 1H), 3.78 (s, 3H). 13C NMR (126 MHz, CDCl3)
d
170.5, 160.1, 149.6, 138.0, 134.4, 130.1, 129.4, 125.6, 125.5, 122.9,
d
170.4, 160.6 (d, J ¼ 248.2 Hz),
119., 114.7, 112.4, 82.5, 55.3.
149.3, 134.6, 130.9, 129.5, 127.7 (d, J ¼ 3.6 Hz), 125.7 (d, J ¼ 3.7 Hz),
125.5,124.7 (d, J ¼ 3.7 Hz),124.1 (d, J ¼ 12.8 Hz),122.8 (d, J ¼ 2.6 Hz),
3.2.21. 3-(furan-2-yl)isobenzofuran-1(3H)-one (3au)
115.9 (d, J ¼ 21.1 Hz). 19F NMR (471 MHz, CDCl3)
d
ꢁ118.3.
Yellow oil; Yield: 24 mg, 40%. 1H NMR (500 MHz, CDCl3)
d 7.99
(d, J ¼ 7.7 Hz, 1H), 7.73 (td, J ¼ 7.5, 1.1 Hz, 1H), 7.62 (t, J ¼ 7.5 Hz, 1H),
3.2.14. 3-(2-methoxyphenyl)isobenzofuran-1(3H)-one (3an)
7.52e7.42 (m, 2H), 6.49 (s, 1H), 6.40 (d, J ¼ 1.4 Hz, 2H). 13C NMR
White solid; Yield: 55.5 mg, 77%. 1H NMR (500 MHz, CDCl3)
(126 MHz, CDCl3) d 169.9, 148.8, 146.5, 144.3, 134.3, 129.8, 126.4,
d
7.94 (d, J ¼ 7.6 Hz, 1H), 7.62 (t, J ¼ 7.5 Hz, 1H), 7.52 (t, J ¼ 7.5 Hz,
125.8, 123.0, 110.7, 110.6, 75.6.
1H), 7.46 (d, J ¼ 7.6 Hz, 1H), 7.36e7.32 (m, 1H), 7.11e7.07 (m, 1H),
6.98 (d, J ¼ 8.3 Hz, 1H), 6.92 (t, J ¼ 7.6 Hz, 1H), 6.87 (s, 1H), 3.92 (s,
3.2.22. 6-Methyl-3-phenylisobenzofuran-1(3H)-one (3ba)
3H). 13C NMR (126 MHz, CDCl3)
d
171.1, 157.1, 150.5, 134.2,
White solid; Yield: 40.6 mg, 60%. 1H NMR (500 MHz, CDCl3)
130.2129.1, 126.9, 125.7, 125.4, 125.1, 123.0, 120.9, 111.0, 78.1, 55.6.
d
7.76 (s, 1H), 7.47 (d, J ¼ 8.0 Hz, 1H), 7.44e7.35 (m, 3H), 7.29e7.27
(m, 2H), 7.23 (d, J ¼ 7.8 Hz, 1H), 6.38 (s, 1H), 2.48 (s, 3H). 13C NMR
3.2.15. 3-(2-(benzyloxy)phenyl)isobenzofuran-1(3H)-one (3ao)
(126 MHz, CDCl3) d 170.7, 147.2, 139.7, 136.7, 135.5, 129.2, 128.9,
127.0, 125.8, 125.5, 122.6, 122.6, 82.6, 21.3.
White solid; Yield: 67.1 mg, 71%. Melting point: 112e114 ꢀC. 1H
NMR (500 MHz, CDCl3)
d
7.89 (d, J ¼ 7.6 Hz, 1H), 7.62e7.58 (m, 1H),
7.50 (t, J ¼ 7.5 Hz, 1H), 7.45 (d, J ¼ 7.7 Hz, 1H), 7.43e7.40 (m, 4H),
7.37e7.34 (m, 2H), 7.17e7.14 (m, 1H), 7.06 (d, J ¼ 8.3 Hz, 1H),
6.97e6.93 (m, 1H), 6.90 (s, 1H), 5.20 (d, J ¼ 11.6 Hz, 1H), 5.11 (d,
3.2.23. 6-(tert-butyl)-3-phenylisobenzofuran-1(3H)-one (3ca)
White solid; Yield: 41.6 mg, 74%. Melting point: 71e74 ꢀC. 1H
NMR (500 MHz, CDCl3)
7.40 (dt, J ¼ 5.4, 2.7 Hz, 3H), 7.30 (dd, J ¼ 11.6, 6.2 Hz, 3H), 6.40 (s,
1H), 1.39 (s, 9H). 13C NMR (126 MHz, CDCl3)
171.0, 153.2, 147.1,
d
7.99 (s, 1H), 7.72 (dd, J ¼ 8.0, 1.8 Hz, 1H),
J ¼ 11.6 Hz, 1H). 13C NMR (126 MHz, CDCl3)
d 171.0, 156.4, 150.4,
136.4, 134.2, 130.4, 129.0, 128.7, 128.2, 127.6, 127.5, 125.8, 125.5,
125.3, 122.9, 121.2, 112.4, 78.5, 70.5. HRMS (ESI): Calculated for
d
136.7, 132.1, 129.2, 129.0, 127.0, 125.5, 122.4, 122.1, 82.6, 35.1, 31.3.
C
21H17O3 (M þ Hþ): 317.1172 found: 317.1170.
3.2.24. 6-Methoxy-3-phenylisobenzofuran-1(3H)-one (3da)
3.2.16. 3-(2-morpholinophenyl)isobenzofuran-1(3H)-one (3ap)
White solid; Yield: 41.6 mg, 58%. 1H NMR (500 MHz, CDCl3)
White solid; Yield: 36.2 mg, 41%. Melting point: 170e173 ꢀC. 1H
d
7.41e7.35 (m, 4H), 7.31e7.25 (m, 2H), 7.22 (d, J ¼ 1.6 Hz, 2H), 6.37
NMR (500 MHz, CDCl3)
d
7.99 (d, J ¼ 7.7 Hz, 1H), 7.65 (t, J ¼ 7.4 Hz,
(s, 1H), 3.89 (s, 3H). 13C NMR (126 MHz, CDCl3)
d
170.6, 160.9, 142.2,
5

Q. Qiang, F. Liu and Z.-Q. Rong
Tetrahedron xxx (xxxx) xxx
136.7, 129.3, 129.0, 127.1, 127.0, 123.8, 123.3, 107.4, 82.6, 55.8.
2.55e2.49 (m, 2H), 2.38e2.36 (m, 1H), 2.19e2.14 (m, 1H), 2.09e2.01
(m, 3H), 1.70e1.58 (m, 3H), 1.55e1.49 (m, 3H), 0.93 (d, J ¼ 6.5 Hz,
3.2.25. 5-Methyl-3-phenylisobenzofuran-1(3H)-one (3ea)
3H). 13C NMR (126 MHz, CDCl3)
d 220.2, 170.9, 147.4, 144.7, 142.1,
White solid; Yield: 41.2 mg, 61%. 1H NMR (500 MHz, CDCl3)
136.9, 129.2, 128.9, 126.9, 123.3, 122.9, 122.3, 82.3, 50.5, 47.8, 44.3,
37.6, 35.8, 31.4, 30.1, 26.0, 25.7, 21.6.
d
7.85 (d, J ¼ 7.8 Hz, 1H), 7.43e7.36 (m, 4H), 7.31e7.28 (m, 2H), 7.13
(s, 1H), 6.36 (s, 1H), 2.45 (s, 3H). 13C NMR (126 MHz, CDCl3)
d
170.6,
13.8. HRMS (ESI): Calculated for C26H27O3 (M þ Hþ): 387.1955
found: 387.1951.
150.3, 145.7, 136.7, 130.6, 129.2, 129.0, 127.0, 125.4, 123.1, 123.0, 82.5,
22.1.
Declaration of competing interest
3.2.26. 5-Methoxy-3-phenylisobenzofuran-1(3H)-one (3fa)
White solid; Yield: 43.1 mg, 60%. 1H NMR (500 MHz, CDCl3)
The authors declare that they have no known competing
financial interests or personal relationships that could have
appeared to influence the work reported in this paper.
d
7.87e7.85 (m, 1H), 7.43e7.35 (m, 3H), 7.32e7.27 (m, 2H), 7.06 (d,
J ¼ 8.4,1H), 6.74 (s,1H), 6.32 (s,1H), 3.84 (s, 3H)$13C NMR (126 MHz,
CDCl3)
d 170.3, 165.0, 152.6, 136.6, 129.3, 129.0, 127.1, 127.1, 117.9,
116.9, 106.7, 82.1, 55.9.
Acknowledgments
3.2.27. 4-Methyl-3-phenylisobenzofuran-1(3H)-one (3ga)
We acknowledge the financial support from the National Nat-
ural Science Foundation of China (21801206), the Chunhui Program
of Ministry of Education of China (5180210003), Program for Young
Talents of Shaanxi Province (5113190023), the Joint Research Funds
of Department of Science & Technology of Shannxi Province and
Northwestern Polytechnical University (2020GXLH-Z-015), and the
Ao'xiang Overseas Scholars Program of NPU.
White solid; Yield: 46.2 mg, 69%. Melting point: 124e128 ꢀC. 1H
NMR (500 MHz, CDCl3)
1H), 7.44 (d, J ¼ 7.6 Hz, 1H), 7.38e7.35 (m, 3H), 7.22e7.19 (m, 2H),
6.35 (s, 1H), 2.04 (s, 3H)$13C NMR (126 MHz, CDCl3)
170.8, 147.6,
d
7.84 (d, J ¼ 7.5 Hz, 1H), 7.50 (t, J ¼ 7.5 Hz,
d
135.6,135.3,133.5,129.8,129.6,129.0,128.2,126.2,123.07, 83.0,17.9.
3.2.28. 4-Fluoro-3-phenylisobenzofuran-1(3H)-one (3ha)
White solid; Yield: 17.7 mg, 26%. Melting point: 135e138 ꢀC. 1H
Appendix A. Supplementary data
NMR (500 MHz, CDCl3)
7.44e7.37 (m, 3H), 7.34e7.31 (m, 3H), 6.54 (s, 1H). 13C NMR
(126 MHz, CDCl3)
169.1, 157.1, (d, J ¼ 256.7 Hz), 135.5 (d,
d
7.81 (d, J ¼ 7.6 Hz, 1H), 7.61e7.57 (m, 1H),
Supplementary data to this article can be found online at
https://doi.org/10.1016/j.tet.2021.132162.
d
J ¼ 17.5 Hz), 134.9, 132.0 (d, J ¼ 6.4 Hz), 129.6, 129.0, 127.1, 121.7 (d,
J ¼ 4.0 Hz), 121.3, 121.2, 80.6.19F NMR (471 MHz, CDCl3)
d
ꢁ117.5.
Supplementary Material
3.2.29. 4-Methoxy-3-phenylisobenzofuran-1(3H)-one (3ia)
Supplementary material that may be helpful in the review
process should be prepared and provided as a separate electronic
file. That file can then be transformed into PD
White solid; Yield: 48.9 mg, 68%. 1H NMR (500 MHz, CDCl3)
d
7.57e7.52 (m, 2H), 7.36e7.34 (m, 3H), 7.30e7.27 (m, 2H), 7.11 (d,
J ¼ 7.4 Hz,1H), 3.76 (s, 3H). 13C NMR (126 MHz, CDCl3)
d 170.5,154.7,
137.2, 135.8, 131.5, 129.0, 128.5, 127.6, 127.5, 117.2, 115.7, 81.7, 55.7.
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9.08 (d, J ¼ 8.3 Hz, 1H), 8.09 (d, J ¼ 8.4 Hz, 1H), 7.96 (d, J ¼ 8.2 Hz,
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Tetrahedron xxx (xxxx) xxx
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