Diastereoselective [3 + 3] cycloaddition reaction of 2-arylideneindan-1,3-diones with β-naphthols: Efficient assemble of immunosuppressive pentacyclic chromanes

Article abstract of DOI:10.1016/j.tetlet.2019.151579

A base promoted diastereoselective formal [3 + 3] cycloaddition reaction of 2-arylideneindan-1,3-diones with β-naphthols towards the synthesis of functionalized pentacyclic indeno[1,2-b]chromen-(4bH)-ones has been developed. This methodology is appreciated in terms of diastereoselectivity and mild conditions. In addition, the immunosuppressive assay indicates that one of the products has selective inhibition on T-cell proliferation (IC₅₀ value of 8.73 μM).

Full text of DOI:10.1016/j.tetlet.2019.151579

Journal Pre-proofs
Diastereoselective [3+3] cycloaddition reaction of 2-arylideneindan-1,3-diones
with β-naphthols: efficient assemble of immunosuppressive pentacyclic chro-
manes
Na Li, Liang Tu, Guiguang Cheng, Houling Sa, Zhenghui Li, Tao Feng,
Yongsheng Zheng, Jikai Liu
PII:
S0040-4039(19)31378-4
DOI:
https://doi.org/10.1016/j.tetlet.2019.151579
TETL 151579
Reference:
Tetrahedron Letters
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Revised Date:
Accepted Date:
27 November 2019
25 December 2019
27 December 2019
Please cite this article as: Li, N., Tu, L., Cheng, G., Sa, H., Li, Z., Feng, T., Zheng, Y., Liu, J., Diastereoselective
[3+3] cycloaddition reaction of 2-arylideneindan-1,3-diones with β-naphthols: efficient assemble of
immunosuppressive pentacyclic chromanes, Tetrahedron Letters (2019), doi: https://doi.org/10.1016/j.tetlet.
2019.151579
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Diastereoselective [3+3] cycloaddition reaction of 2-arylideneindan-1,3-diones with
β-naphthols: efficient assemble of immunosuppressive pentacyclic chromanes
Na Li,a Liang Tu,a Guiguang Cheng,b Houling Sa,a Zhenghui Li,a Tao Feng,a Yongsheng Zhenga and Jikai
Liua
a. School of Pharmaceutical Sciences, South-Central University for Nationalities, Wuhan, 430074, China
b. Yunnan Institute of Food Safety, Kunming University of Science and Technology, Kunming 650500, China
———
ARTICLE INFO
ABSTRACT
 Corresponding author.
E-mail adress: zhysh@mail.scuec.edu.cn (Y.-S. Zheng),
Article history:
A base promoted diastereoselective formal [3+3] cycloaddition reaction of 2-arylideneindan-1,3-
Received
Received in revised form
Accepted
diones with β-naphthols towards the synthesis of functionalized pentacyclic indeno[1,2-
b]chromen-(4bH)-ones has been developed. This methodology is appreciated in terms of
diastereoselectivity and mild conditions. In addition, the immunosuppressive assay indicates that
one of the products has selective inhibition on T-cell proliferation (IC50 value of 8.73 μM).
jkliu@mail.kib.ac.cn (J.-K. Liu)
Available online
2009 Elsevier Ltd. All rights reserved.
Keywords:
β-Naphthols
[3+3] Cycloaddition
Pentacyclic chromanes
Immunosuppressant
In the past few decades, great progress has been made in the
synthesis of biologically active complex molecular structure via
cycloaddition reactions. Functionalized chroman complexes
represent a privileged structural motif that is found in a broad
range of biologically active natural products1 (e.g., carpanone2
and (+)-machaeriol3) and pharmaceutically active compounds4,
such as (-)-nabilone, which is used as an antiemetic and analgesic
agent,5 CB1 full agonist6 and GPR40 receptor antagonist7 (Figure
1). Particularly, the polycyclic chroman cores are recurring
structural motifs in natural product comprising (e.g., (-)-
siccanin).1,8 Owing to the importance of chroman framework, the
construction of this privileged skeleton and its analogues has
attracted considerable attention, and several elegant strategies
have been developed.9 However, most prepared chroman
scaffolds are bicyclic and tricyclic chromans.9,10 In sharp contrast,
the development of efficient methods for construction of
functionalized polycyclic chromans has received much less
attention and still remained challenging. For selected example,
the Wu group described the C(sp3)−H bond functionalization of
Me
H
O
H
Me
H
OH
H
OH
O
O
O
H
O
Me
Me
H
O
Me
O
Me
5
Ph
O
O
Me
Me
Me
Carpanone
N
(+)-Machaeriol A
(-)-Nabilone
F
O
OH
MeO
H
Me
Me
O
COOH
H
H
Me
Me
O
Me
(-)-Siccanin
GPR40 receptor agonist
Figure 1. Natural product and pharmaceutical compounds with
polycyclic chroman motifs
hemiketalization/lactonization cascade has been established for
the synthesis of polycyclic bridged 2-chromanol lactones by
Kontham.15 Despite these elegant examples, the development of
synthetic method to construct the structurally attractive and
biologically important polycyclic chroman framework from
readily available starting material is still demanded.
benzo[c]oxepines
via
C−O
bond
cleavage/Michael
additinon/annulation reaction for the synthesis of multisubstituted
chromans.11 Wang’s group achieved the FeCl3-catalyzed cascade
reaction of indoles and o-hydroxychalcones for the assembly of
indole-bridged polycyclic chromans.12 The Lin group developed
the cascade reaction of azomethine imines and 2-benzalidene-
1,3-indanediones to generate the structurally complex polycyclic
bridged chroman framework.13 Schneider reported the Brønsted
acid catalyzed intramolecular oxa-Diels-Alder reaction of ortho-
During the past decades, due to the 1C,3O-bisnucleophilic
reactivity, β-naphthols have emerged as powerful and versatile
building blocks in a variety of [3+n] cycloaddition reactions with
biselectrophilic compounds for the synthesis of various
biologically active heterocycles.16 On the other hand, since the
widely application of immunosuppressive agents in organ
transplantation and immunity-associated disorders, the past half
century has witnessed the fast progress of this research field,
especially, the development of selective immunosuppressive
quinone
dihydrochromenochromenes.14 Recently,
diastereoselective Friedel-Crafts
methides
with
dienophiles
to
construct
a
Fe(III)-catalyzed
alkylation/

2
Tetrahedron Letters
drugs.17 As our continuous research in discovery of novel
range of 2-arylideneindan-1,3-diones was subsequently surveyed
(Table 1, entry 10) and the results are outlined in Table 2. The
reaction proceeded smoothly and delivered the corresponding
pentacyclic chroman (±)-3 (3aa-sa) in moderate to excellent
yield in single diastereoisomer except for 3ta and 3ua. Generally,
obvious electronic effect has been observed. The substrates with
electron-withdrawing substituents on the phenyl ring of 2-
arylideneindan-1,3-diones gave higher yields than the electron-
neutral and electron-donating ones (3aa-fa, 3ja and 3ka vs 3ga,
3ha, 3la). 2-arylideneindan-1,3-diones bearing substituents at the
ortho and meta position of the phenyl ring were also good
substrates for this reaction (3ia, 3ja and 3ka). Interestingly,
substrates with a sterically more bulky group on the phenyl ring
of 2-arylideneindan-1,3-diones exerted a negligible effect on the
reaction efficiency (3ja, 3ka and 3ma). Then, naphthyl and
heterocyclic substituents were investigated. The electron-
donating heterocycles had significant influence on the yields,
giving only 47-63% yields (3qa, 3ra and 3sa). We also tried the
pyrrole substituted 2-arylideneindan-1,3-dione. However, no
desired product was detected, and the starting material
decomposed. When the 1u was applied, no reaction was observed
even at 50 ︒C, mainly due to the electron donating nature of the
isopropyl group. Although the multisubstituted 2-arylideneindan-
1,3-diones were compatible in this reaction (3la and 3ma), 3ua
was not obtained mainly because of the poor solubility of 1u.
immunosuppressants,18 herein, we report the synthesis of
pentacyclic chromanes via the formal [3+3] cycloaddition
reactions of β-naphthols with 2-arylideneindan-1,3-diones and its
promising selective inhibition on T-cell proliferation. Although
Wu et al discribed the C(sp3)−H bond functionalization of
benzo[c]oxepines
via
C−O
bond
cleavage/Michael
additinon/annulation reaction of β-naphthols with structurally
complex benzo[c]oxepines under harsh conditions,11 the
development of more rapid access to pentacyclic chromans with
readily available starting material under mild reaction conditions
is still desirable. To the best of our knowledge, there is no report
on the synthesis and immunosuppressive activity of pentacyclic
chromanes by using β-naphthols and 2-arylideneindan-1,3-diones
as the starting material.
The initial study was conducted by using 2-arylideneindan-
1,3-dione 1a and β-naphthol 2a as model substrates with various
bases at room temperature. The results are summarized in Table 1.
To our delight, the Friedel-crafts reaction and intramolecular
hemiketalization proceeded smoothly and the desired compound
3aa was obtained in a single diastereoisomer in 13% yield when
Na2CO3 was used as the base. Then different bases were screened
in toluene at room temperature. The organic bases proved to be
the effective catalyst in this transformation, and TEA afforded
the product in 88% yield. Further investigations on the reaction
media were conducted with various solvents by using TEA (20
Then, we turned our attention to further investigate the scope
and limitation by reacting 1a with a variety of β-naphthol 2
bearing different substituents. As shown in Table 3, a wide range
of β-naphthols underwent the Friedel-crafts reaction and
Table 1
Optimization of the reaction conditions.a
O
O
H
Table 4
OH
base
Immunosuppressive effects of the products on murine
lymphocyte proliferation induced by ConA or LPS.
(IC50 in μM)
Ph
solvent
rt
HO
O
O
1a
2a
3aa
Entry
Catalyst
Solvent
Toluene
Toluene
Toluene
Toluene
Toluene
THF
Time (h)
48
Yield %
13
Table 2
cmpd
ConA-induced
LPS-induced B-
1
Na2CO3
K2CO3
TEA
Substrate scope and Tli-mceiltlaptiroonlifeoraftio2n-arylidceenlel ipnrdolainfe-r1a,t3io-n
a,b 3aa
12.7
18.2
11.7
>100
17.7
95.7
28.8
31.4
35.1
65.8
diones
2
48
16
O
3ba O
H
R
3
48
88
3ca
3ea
OH
TEA
HO
R
CHCl
15.6
4
DIPEA
DBU
TEA
48
46
O
3
rt
O
1b-u
2a
3ba-ua
3fa
3ha
3iaX
3ja
3ka
3la
13.5
5
48
57
11.9
18.6
11.6
17.2
R
6
48
34
O
O
O
X
O
O
O
NO2
H
H
H
H
70.8
7
TEA
MeCN
Dioxane
MeOH
CHCl3
48
79
74.9
HO
HO
O
HO
HO
O
8
TEA
48
40
49.2
26.3
16.9
15.7
27.5
63.3
42.5
3ea, R = CN, 99%
3fa, R = NO2, 99%
3ga, R = CH3, 68%
3ba, X = F, 77%
3ia, 99%
3ja, X = F, 82%
3ma
>100
3ca, X = Cl, 90%
3ka, X = Br, 98%
9
TEA
48
79
3da, X = Br, 91%
R
3oa
>100
3ha, R = OCH3, 84%
OCH3
OCH3
F
10
11
TEA
36
98
3pa
>100
F
O
O
O
H
O
OCH3
3qa
3ra
3ab
29.3
H
H
H
TEA
DCM
48
93
27.9
a
HO
HO
HO
HO
O
Unless otherwise noted, the reactions were performed with 1a
(0.20 mmol), 2a (0.24 mmol) and base (0.04 mmol) in 2.0 ml
O
O
O
8.7
73.2
3na, 92%
3oa, 74%
3la, 55%
3ma, 87%
3ad
3ae
16.4
19.2
1.6
47.3
57.9
solvent.
O
O
O
H
O
b
Dexamethasone
0.8
Isolated yield of the product, only one diastereoisomer was
observed by crude NMR analysis.
H
H
H
X
S
N
HO
O
HO
O
HO
HO
O
O
mol%) as catalyst. Comparable results were observed when
acetonitrile or methanol was used (Table 1, entries 7 and 9).
However, the ether solvents resulted in drastically decreased
yields (Table 1, entries 6 and 8). Chlorinated solvent such as
dichloromethane and chloroform is beneficial to the reaction
efficiency, and chloroform gave the best results, yielding 3aa in
98% yield. The products in all the cases retained excellent
diastereoselectivities and only one diastereoisomer was observed.
3ta, 0%
3pa, X = C, 75%
3qa, X = N, 63%
3ra, 53%
3sa, 47%
Br
O2
N
O
H
HO
O
3ua, 0%
a Unless otherwise noted, the reactions were performed with 1 (0.20
mmol), 2a (0.24 mmol) and base (0.04 mmol) in 2.0 ml solvent.
b Isolated yield of the product, only one diastereoisomer was
observed by crude NMR analysis.
With the optimal conditions established, the substrate scope
and limitation of this formal [3+3] cycloaddition reaction with a

Table 3
Substrate scope and limitation of β-naphtholsa,b
O
O
H
R
OH
TEA
R
Ph
CHCl3
rt
HO
O
O
1a
2b-e
3ab-ae
O
O
O
O
O
O
O
O
H
H
H
H
Br
HO
Br
HO
HO
CN
HO
Br
3ab, 77%
3ac, 50%
3ad, 73%
3ae, 53%
unsuccessful substrates:
OH
OCH3
NH2
H
2N
OH
HO
OH
OH
HO
OH
H
3CO
OH
a Unless otherwise noted, the reactions were performed with 1 (0.20
mmol), 2a (0.24 mmol) and base (0.04 mmol) in 2.0 ml solvent.
b
X-ray crystal structure of 3da
Isolated yield of the product, only one diastereoisomer was
observed by crude NMR analysis.
Figure 2. X-ray crystal structure of 3da
compounds exhibited impressive inhibitive activity against
ConA-induced T-cell proliferation. Particularly, compound 3ab
exhibited promising selective inhibition against the T-cell
proliferation with IC50 value 8.7 μM.
intramolecular hemiketalization process smoothly and yielded
corresponding pentacyclic chromans 3ab−ae in 50−77% yields
(Table 3). The electron deficient substituent on β-naphthol had
detrimental effects on the reaction efficiency, which could be
ascribed to the low nucleophilicity caused by the electron-
withdrawing cyanogroup (3ac). However, the electron-rich 8-
aminonaphthalen-2-ol did not undergo any reaction under the
standardized condition. Other electron-rich phenols were also
applied in this reaction, however, no reaction was observed,
perhaps because of the decreased electrophilicity of the phenols.
Conclusions
In summary,
a
diastereoselective formal [3+3]
cycloaddition reaction of 2-arylideneindan-1,3-diones with
β-naphthols has been developed for the first time, affording
a
library of functionalized pentacyclic indeno[1,2-
To evaluate the synthetic potential of the reaction, a gram-
scale synthesis of 3da was carried out. As shown in Scheme 1,
3.5 mmol of 1d reacted smoothly with 4.2 mmol of 2a under the
optimized reaction conditions, delivering the corresponding
product 3da in 85% yield (1.36 g). In addition, some chemical
transformations were conducted to decorate the product. By
treatment of 3aa with trifluoroacetic, the dehydrated elimination
occurred, affording the α,β-unsaturated ketone 4 in 98% yield,
which could be further reduced to alcohol 5 by NaBH4 in single
diastereoisomers in 71% yield.
b]chromen-(4bH)-ones in good to excellent yields. Member
3ab of this library showed selective inhibition against
ConA-induced T-cell proliferation with IC50 value 8.7 μM.
This synthetic methodology and the discovery of this type of
selective immunosuppressants provide new possibilities to
explore novel immunosuppressants by inhibiting T cell
proliferation.
Acknowledgments
The relative configuration of the product (±)-3da was
unambiguously determined by X-ray crystallographic analysis
(CCDC 1962616) (Figure 2). Consequently, all of the other
pentacyclic chromans can be assigned to have the same relative
configurations by analogy.
Y.S.Z gratefully acknowledges the funding from the
National Natural Science Foundation of China (81973208),
Hubei Provincial Natural Science Foundation of China
(2019CFB624). We also thanks the National Natural
Science Foundation of China (81773590, 31870513,
81872762), the funding from the National Key R&D Plan
(2017YFC1704007) and “the Fundamental Research Funds
for the Central Universities”, South-Central University for
Nationalities (CZP1800). Analytical data were obtained
from the Analytical & Measuring Center, School of
Pharmaceutical Sciences, South Central University for
Nationalities.
Having synthesized a variety of chroman-fused derivatives, we
performed preliminary studies of their immunosuppressive
Br
Br
O
O
O
H
OH
TEA
CHCl3
rt
HO
O
1d
2a
3da
3.5 mmol
4.2 mmol
1.36 g
OH
O
O
O
H
References and notes
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89% yield
4:1 dr
toluene
reflux
98% yield
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Diastereoselective [3+3] cycloaddition
reaction of 2-arylideneindan-1,3-diones with
β-naphthols: efficient assemble of
Leave this area blank for abstract info.
immunosuppressive pentacyclic chromanes
Na Li, Liang Tu, Guiguang Cheng, Houling Sa, Zhenghui Li, Tao Feng, Yongsheng Zheng and Jikai Liu
O
O
H
Ar
R
OH
R
TEA
Ar
CHCl3
rt
HO
O
O
# 23 examples # up to 99% yield # Mild conditions
# Selective inhibition against the T-cell proliferation with IC50 value 8.7 μM
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Graphical Abstract
For selected examples, see: (a) Z.H. You, Y.H. Chen, Y. Tang,
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