Synthesis of 1-aryl- benzocycloalkane derivatives via one-pot two-step reaction of benzocyclonone, tosylhydrazide, and arylboronic acid

Article abstract of DOI:10.1080/00397911.2019.1581893

A metal-free one-pot two-step reductive coupling reaction of benzocyclonone, tosylhydrazide, and arylboronic acid was developed for the formation of a C(sp³)–C(sp²) bond, which enabled the efficient synthesis of 1-aryl-benzocycloalkane compounds in moderate to good yields on a multi-gram scale. Moreover, five- and six-membered benzocyclic ketones are also suitable substrates for this reaction. Notably, this protocol was also found to be suitable for synthesizing 3-(3,4-dichlorophenyl)-2,3-dihydro-1H-inden-1-one, an important intermediate in the synthesis of indatraline.

Full text of DOI:10.1080/00397911.2019.1581893

Synthetic Communications
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Synthesis of 1-aryl- benzocycloalkane derivatives
via one-pot two-step reaction of benzocyclonone,
tosylhydrazide, and arylboronic acid
Shijuan Liu, Meitong Fang, Dongni Yin, Yanan Wang, Lei Liu, Xiuying Li &
Guangbo Che
To cite this article: Shijuan Liu, Meitong Fang, Dongni Yin, Yanan Wang, Lei Liu, Xiuying Li &
Guangbo Che (2019): Synthesis of 1-aryl- benzocycloalkane derivatives via one-pot two-step
reaction of benzocyclonone, tosylhydrazide, and arylboronic acid, Synthetic Communications, DOI:
10.1080/00397911.2019.1581893
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https://doi.org/10.1080/00397911.2019.1581893
Synthesis of 1-aryl- benzocycloalkane derivatives via one-
pot two-step reaction of benzocyclonone, tosylhydrazide,
and arylboronic acid
Shijuan Liua,b, Meitong Fangb, Dongni Yinb, Yanan Wangb, Lei Liub, Xiuying Lia,b
and Guangbo Chea
,
aMinistry of Education, Key Laboratory of Preparation and Application of Environmental Friendly
b
Materials, Jilin Normal University, Changchun, China; College of Chemistry, Jilin Normal University,
Siping, China
ABSTRACT
ARTICLE HISTORY
Received 26 September 2018
A metal-free one-pot two-step reductive coupling reaction of benzo-
cyclonone, tosylhydrazide, and arylboronic acid was developed for
the formation of a C(sp3)–C(sp2) bond, which enabled the efficient
synthesis of 1-aryl-benzocycloalkane compounds in moderate to
good yields on a multi-gram scale. Moreover, five- and six-mem-
bered benzocyclic ketones are also suitable substrates for this reac-
tion. Notably, this protocol was also found to be suitable for
synthesizing 3-(3,4-dichlorophenyl)-2,3-dihydro-1H-inden-1-one, an
important intermediate in the synthesis of indatraline.
KEYWORDS
1-Aryl-benzocycloalkane;
benzocyclonone; tosylhydra-
zones; arylboronic acid;
metal-free
GRAPHICAL ABSTRACT
Introduction
1-Aryl-benzocycloalkane is an important structural motif that is frequently found in
pharmaceutically active molecules, including an estrogen receptor ligand,[1] the hypolipi-
demic agent nafenopin,[2] a potent cell growth and tubulin polymerization inhibitor,[3]
and three drugs containing a 1-phenyl-2,3-dihydro-1H-indene skeleton[4,5] (Figure 1).
Thus, the efficient synthesis of 1-aryl-benzocycloalkane has attracted considerable atten-
tion. The construction of the 1-aryl-benzocycloalkane skeleton generally comprises the
following methods: (a) alkylation of aromatic ketones with an organolithium reagent
followed by lithium–ammonia reduction;[6] (b) transition-metal catalyzed or other
reagent-mediated cyclization;[7–10] and (c) transition-metal catalyzed enantioselective
hydrogenation of substituted benzo-fused five-, six-, and seven-membered alkenes.[11–13]
Although the synthetic strategies mentioned above have proved useful for preparing
CONTACT Guangbo Che
guangboche@jlnu.edu.cn
Ministry of Education, Key Laboratory of Preparation and
Application of Environmental Friendly Materials, Jilin Normal University, Changchun, 130103, China.
Supplemental data for this article is available online at on the publisher’s website.
ß 2019 Taylor & Francis Group, LLC

2
S. LIU ET AL.
Figure 1. Representative pharmaceutically active molecules based on the 1-aryl-benzocycloal-
kane motif.
1-aryl-benzocycloalkanes, a more efficient and comprehensive metal-free method is still
needed for the synthesis of 1-aryl-benzocycloalkanes with improved starting material
availability, broad substrate scope, and simple operation.
Tosylhydrazones as diazo precursors are useful synthetic intermediates that have been
used in organic chemistry.[14–19] In 1994, a facile metal-free alkylation of aryl aldehyde
tosylhydrazones with trialkylboranes was first reported by Kabalka et al.[20,21] In 2009,
the metal-free reductive coupling reaction between N-tosylhydrazones and boronic acids
was discovered by Barluenga et al.[22] Subsequently, this novel reaction was developed
for the successful synthesis of various types of structural skeletons by using different N-
tosylhydrazones (prepared by the reactions of various carbonyl compounds with sul-
fonyl hydrazide) and boronic acids as substrates, including heterocyclic aldehydes,[23]
cyclic ketones,[24,25] alkenylboronic acids,[26] fluorenones,[27] diaryl ketones,[28] and ace-
tyl naphthalene.[29] These studies demonstrated the versatility of the reductive coupling
reaction for the preparation of highly functionalized, highly polar compounds through
C–C bond formation. Herein, we decided to expand this reaction for the synthesis of 1-
aryl-benzocycloalkanes from Benzocycloketones and arylboronic acids.
Results and discussion
Initially, 1-tetralone (1a, 0.5 mmol) and phenylboronic acid (2a, 0.75 mmol) were
chosen as model substrates for the reductive coupling in the presence of tosylhydrazide
(1.5 equivalents) and potassium carbonate (K2CO3, 2 equivalents) (Table 1). First, the
ꢀ
condensation of 1-tetralone with tosylhydrazide in DMF for 2 hours at 80 C gave the
N-tosylhydrazone intermediate, which was reacted with K2CO3 and 2a for another 5
hours at 110 ꢀC affording the product 1-phenyltetralin 3a in 40% yield (entry 1).
Furthermore, a short list of solvents was screened for applicability in this reaction. A

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3
Table 1. Optimized reaction conditionsa.
Entry
Base
K2CO3
Solvent
DMF
THF
EtOH
DMSO
Yield(%)b
1
2
3
4
5
6
7
8
40
trace
trace
trace
10
89
92
85
55
28
60
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
K2CO3
Cs2CO3
NaOH
CH3CN
1,4-dioxane
Toluene
Toluene
Toluene
Toluene
Toluene
9
10
11
K3PO4ꢁH2O
Et3N
aReaction conditions: 0.50 mmol 1-tetralone, tosylhydrazide (1.5 equiv.), 0.75 mmol phenylboronic acid, 5 mL solvent,
T1 ¼ 80 ꢀC/t1 ¼ 2 h, T2 ¼ 110 ꢀC/t2 ¼ 5 h.
bIsolated yield.
lower yield was observed using THF, EtOH, DMSO, and CH3CN as the solvent compared
to that obtained using DMF (entries 2–5). Notably, a significantly higher yield was
obtained by using 1,4-dioxane or toluene as the solvent (entries 6 and 7). The screening
of different bases revealed K2CO3 and Cs2CO3 to be appropriate bases for delivering the
desired product in good yield, while other bases, namely NaOH, K3PO4ꢁH2O, and Et3N,
afforded significantly lower yields (28–60%, entries 8–11). Finally, the combination of 1-
tetralone (0.5 mmol), tosylhydrazide (1.5 equiv.), phenylboronic acid (0.75 mmol), and
ꢀ
ꢀ
K2CO3 (2 equivalents) at T1 = 80 C (t1 = 2 hours) and T2 = 110 C (t2 = 5 hours) in
toluene (5 mL) was found to be the most suitable reaction conditions.
Upon optimizing the reaction conditions, we further investigated the substrate scope
of this one-pot, two-step reductive coupling reaction. As shown in Table 2, the 4-substi-
tuted arylboronic acid substrates bearing electron-withdrawing or electron-donating
groups constantly afforded the desired products 3b–3g in 66–88% yields. Moreover,
difluoro- or trifluoro-substituted arylboronic acids were also used as coupling partners
to provide the products 3h–3j in 65–84% yields. Furthermore, reductive coupling reac-
tions involving meta- and ortho-substituted arylboronic acids as substrates were investi-
gated to give the desired products 3k and 3 l in 85% and 50% yields, respectively. Of
note, the reaction of naphthalen-2-ylboronic acid with 1-tetralone was also attempted
and the desired product 3 m was obtained in 96% yield. Similarly, thiophen-3-ylboronic
acid also shows good reactivity for conversion into the corresponding product 3n in
75% yield. In addition, 4-chromanone was treated with phenylboronic acid under the
optimized reaction conditions to give the corresponding product 3o in 50% yield.
To further investigate the range of substrates, a variety of 2,3-dihydro-1H-inden-1-
one derivatives were studied. As shown in Table 3, all arylboronic acids reacted well
with 2,3-dihydro-1H-inden-1-one to give the corresponding products 4a–4m in service-
able to good yields. Subsequently, a series of 1-indanone derivatives was examined. Both
electron-rich and electron-deficient 1-indanone derivatives proved competent coupling
partners in this reaction manifold and gave the desired products 4n–4q in
42–83% yields.

4
S. LIU ET AL.
Table 2. Substrate scope of 1-tetralone derivative and arylbor-
onic acida.
aReaction conditions: 0.50 mmol 1-tetralone derivative, 0.75 mmol phenylboronic
acid, 1.5 equiv. base, 5 mL toluene, T1 ¼ 80 ꢀC/t1 ¼ 2 h, T2 ¼ 110 ꢀC/t2 ¼ 5 h. The
isolated product yields are given.
Table 3. Substrate scope of 1-indanone derivative and arylbor-
onic acida.
aReaction conditions: 0.50 mmol 1-indanone derivative, 0.75 mmol arylboronic acid,
1.5 equiv. base, 5 mL toluene, T1 ¼ 80 ꢀC/t1 ¼ 2 h, T2 ¼ 110 ꢀC/t2 ¼ 5 h. The iso-
lated products yields are given.

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5
Scheme 1. A gram-scale synthesis of products 3a.
Scheme 2. An intermediate synthesis of products 4r.
Scheme 3. Intermolecular competition experiments.
To demonstrate the practical usefulness of this reaction, a gram-scale experiment was
executed (Scheme 1). The reaction was performed using 1a (10 mmol) with phenylbor-
onic acid (1.5 equiv.), and gave an excellent yield of 98%, leading to 2.041 g of the
desired product 3a.
Using this strategy, 5,6-dichloro-1H-indene-1,3(2H)-dione monotosylhydrazone can
be reacted with (3,4-dichlorophenyl)boronic acid to provide direct access to 3-(3,4-
dichlorophenyl)-2,3-dihydro-1H-inden-1-one 4r in 85% yield, an intermediate used in
the synthesis of the monoamine transport inhibitor indatraline.[30] (Scheme 2).
Next, an intermolecular competition experiment was carried out using 1a0 and 1b0
1
(Scheme 3). Inspection of the crude reaction mixture by H NMR spectroscopy showed
that the ratio of 3a to 4a was approximately 2.2:1, thus clearly indicating that the cou-
pling reaction of arylboronic acid and TsNHNH2 with 1-tetralone is favored over that
with 1-indanone. Namely, the reactivity of 1-tetralone was significantly higher than that
of 1-indanone.
Experimental section
Materials and instruments
Chemicals were obtained commercially and used as received. All products were isolated
by short chromatography on a silica gel (200–300 mesh) column using petroleum ether

6
S. LIU ET AL.
(60–90 ꢀC), unless otherwise noted. The NMR spectra were recorded on a Bruker
1
Avance III HD 400 spectrometer using TMS as internal standard (400 MHz for H
NMR, and 100 MHz for 13C NMR).
General procedure for one-pot two-step reductive coupling of benzocyclonone,
tosylhydrazide, and arylboronic acid
A solution of benzocyclonone 1 (0.5 mmol) and tosylhydrazide (0.75 mmol) in 5 mL of
ꢀ
toluene was stirred at 80 C for 2 h in a reaction tube. Potassium carbonate (1.0 mmol)
and the appropriate arylboronic acid 2 (0.75 mmol) were added to the reaction mixture.
ꢀ
The system was refluxed at 110 C for 5 h with stirring. When the reaction was com-
plete, the crude mixture was allowed to cool to room temperature. Dichloromethane
and a saturated solution of NaHCO3 were added and the layers were separated. The
aqueous phase was extracted three times using dichloromethane. The combined organic
layers were dried over Na2SO4 and then filtered. The solvent was removed under
reduced pressure. The products were purified by chromatography on silica gel.
Conclusion
In conclusion, we have reported a general and practical metal-free one-pot two-step
coupling reaction of benzocyclic ketone and tosylhydrazide with arylboronic acid. This
novel protocol provides an efficient method for the construction of 1-aryl-benzocycloal-
kanes in good yields. Remarkably, both five- and six-membered benzocyclic ketones are
suitable substrates for this reaction. The advantages of this method include: (i) metal-
free one-pot two-step reaction, (ii) readily available starting materials, (iii) broad sub-
strate scope, and (iv) gram-scale synthesis. Notably, this protocol was also found to be
suitable for synthesizing 3-(3,4-dichlorophenyl)-2,3-dihydro-1H-inden-1-one, an import-
ant intermediate in the synthesis of indatraline. We believe that this coupling reaction
will become a widely useful transformation in organic synthesis.
Disclosure statement
We state that none of the authors have any conflict of interest in the context of this
communication.
Acknowledgments
We gratefully acknowledge financial support of this work by the National Natural Science
Foundation of China [51603086], and the Science Development Project of Jilin Province
[20180623042TC, 20170520147JH].
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