Mandal, T. K.: Some novel synthesis of……
71
Review Article
Some novel synthesis of biologically active benzopyran derivatives
Tapas Kumar Mandal
Assistant Professor, Department of Chemistry, Fakir Chand College, Diamond Harbour, 24
Pgs (S), Pin – 743331.
Correspondence should be addressed to Tapas K. Mandal: [email protected]
Abstract
Compounds containing pyran, benzopyran and benzothiopyran ring systems display
interesting biological activities such as antiallergic, antitumor, antiviral, antioxidant and
antiinflammatory etc. The aim of the present paper was to review the various synthetic
approach of this type of compounds on this field.
Key words: Benzopyran derivatives
Indroduction
Heterocycles play an important role in the design and discovery of new
physiological/pharmacologically active compounds. Chemically, chromones (4H-chromen-4-
ones) are heterocyclic compounds with the benzopyrone framework. Molecules containing the
chromone or benzopyranone ring have a wide range of biological activities1-6. They have been
shown to be tyrosine and protein kinase inhibitors, as well as anti-inflammatory, antiviral,
antioxidant7, and antihypertensive agents. Chromone derivatives are also active at
benzodiazepine receptors, and on lipoxygenase and cyclooxygenase. In addition to this, they
have been shown to be anticancer agents8, possessing antimutagenic properties and the ability
to inhibit electron transport through inhibition at NADH. The main objectives of benzopyran
derivatives synthesis are not only for the development of more diverse and complex bioactive
compounds for biological activity and structure-activity relationship studies but also for other
applications in Medicinal Chemistry.
Prajnan O Sadhona ……., Vol. 4, 2017
72
Synthesis of 4H-1-Benzopyran Derivatives
Scheme 1
Rovis et al9. developed a highly enantio- and diastereoselective intramolecular Stetter
reaction. Subjection of α,α-disubstituted Michael acceptors to an asymmetric intramolecular
Stetter reaction results in a highly enantioselective conjugate addition. The reaction is
heterocyclic carbene catalyzed stereoselective cyclization.
Scheme 1
Scheme 2
Pawar et al10. synthesised flavones, a benzopyran derivative using recyclable ionic
liquid under microwave irradiation condition.
Scheme 2
Scheme 3
Lokenande et al11. developed dimethylsulfoxide- iodine catalysed one-pot oxidative
deallylation of 2′-Allyloxychalcones which undergo undergo deprotection and subsequent
oxidative cyclisation to give flavones.
Scheme 3
Scheme 4
Kabalka et al12. developed Cu (II) catalyzed MW assisted cyclization of enol. They
synthesised functionalized flavones and chromones via the cyclization of 1-(2-hydroxyaryl)-
3-aryl-1,3-propanedione .
Scheme 4
Ph
NN
NCF3
..
Tolune, 25oC, 24 hr
(50-95%)
O
O
R
EWR
O
O
R
EWRH
R2R2
OH
R1
O O
O
O
R1
MW (22-50 Sec)
[EtNH3]NO3
(80-90%)
R3
R4
O
O
R1
R2 I2, DMSO
130oC, 30 min.
R3
R4
O
O
R1
R2
(85-97%)
CuCl2, EtOH
MW,80oC,5 min.
OOH
R
O O
R
O(86-98%)
Mandal, T. K.: Some novel synthesis of……
73
Scheme 5
Mukaiyama and coworkers13 explored base-catalyzed [2,3]-Wittig rearrangement of
silyl enolates in DMF solvent at room temperature to produce α-allyloxy ketones in good yield.
Scheme 5
Scheme 6
Yang et al14. developed Pd-catalyzed copper-free carbonylative Sonogashira coupling
reaction which was utilized to synthesize flavones from terminal alkynes and aryl iodides by
using water as solvent. The reaction was carried out at room temperature under balloon pressure
of CO with Et3N as a base.
Scheme 6
Scheme 7
Ahmed et al15 . explored Silica gel supported InBr3 or InCl3 (15–20 mol %) as a new
solid-support catalysts for the facile and efficient oxidation, under solvent free conditions, of
2′-hydroxychalcones and flavanones to yield the corresponding flavones in >80% yield. The
catalysts are easily prepared, stable, and efficient under mild reaction conditions.
Scheme 7
NLi
O
DMF, rt, 1 hr
O
OOH
O
OSiMe3
O
H+
(93%)
I
OH
+ R'-C C H
CO, 25oC, 24 hr
PdCl2, PPh3, Et3N, H2O O
RR
R
O(35-91%)
Aryl-IPd(0)
Aryl-Pd-ICO
Aryl-CO-Pd-IR-C C-H
Aryl-CO-Pd R
Pd(0)
Aryl-C
O
C C-R
Et3N
OH
O
R2
R1 InBr3 or InCl3O
O
R2
R1
Solvent-free Condition
Prajnan O Sadhona ……., Vol. 4, 2017
74
Scheme 8
Seijas et al16. synthesised flavanone derivatives by microwave irradiation of
phloroglucinol and β-ketoesters under solvent free condition. The reaction goes through a
cycloaddition of an α-oxo ketene intermediate followed by an uncatalyzed thermal Fries
rearrangemen.
.
R1, R2, R3, R4 =H. OH. OMe, NO2
Scheme 8
Scheme 9
J. I. Lee et al17. synthesised flavones from1-(2-methoxyphenyl)-3-phenyl- 1,3-
propanediones. The cyclization was successfully accomplished by heating with hydriodic acid
in glacial acetic acid. The cyclization accompanied by the cleavage of the 2-methoxy group of
1-(2-methoxyphenyl)-3-phenyl-1,3- propanedione with 47% HI proceeded well in glacial
acetic acid for 1.5 h at 100 o C to afford flavone in 78% yield.
Scheme 9
Scheme 10
Choudary et al18. designed and developed a nano heterogeneous catalyst for the
Claisen–Schmidt condensation (CSC) of benzaldehydes with 2-hydroxyacetophenone to yield
substituted chalcones followed by isomerization to afford flavanones with excellent yields.
Scheme 10
OEt
O OR1
R2
R3
R4
HO O
OOH
R4
R3
R2
R1
OH
M W
OHHO
O O
R4OCH3
R3
R2
HI / HOAc
100oC, 2 hr
O
R4
O
R3
R2
R2
R2(60-78%)
R1
R2
O
H+
OH
CH3
R3
O
80oC, Ethanol
NAP-MgO
O
O
R1
R2
(50-90%)
R3
Mandal, T. K.: Some novel synthesis of……
75
Scheme 11
Chandrasekhar et al19. used L-Proline as an efficient organocatalyst for the synthesis of
substituted flavanones and chalcones in good yields. The efficiency of the catalyst was proved
with a variety of substrates ranging from electron-deficient to electron-rich aryl aldehydes and
2-hydroxyacetophenones.
Scheme 11
Scheme 12
A novel and conveient one‐pot synthesis of 3‐aroyl‐7‐hydroxy‐6‐nitroflavones from
2′,4′‐dihydroxy‐5′‐nitroacetophenone and (substituted)benzoyl chlorides in refluxing dry
acetone in the presence of anhydrous potassium carbonate was developed20.
Scheme 12
Scheme 13
Larock et al21. synthesised iodine substituted chromone derivatives by using
interhalogen compound ICl. They developed ICl induced cyclization of heteroatom-
substituted alkynones which provides a simple, highly efficient approach to various 3-
iodochromones, iodothiochromenones, iodoquinolinones and analogues in good to excellent
yields.
Scheme 13
R
R1
O
H
R
R1
O
+ R''
L-Proline
DMF, 80oC, 18 hr
OH
O O
R"
(60-73%)
OH
O2N
HO
O
+R
Cl
O
K2CO3, acetone
reflux, 35-46 hr
O
O2N
HO
O
O
R
R
CH2Cl2
ICl, -78oC or rt
X = O, S, NMe2
XMe
O
X
O
I
R
96-99%
R
Prajnan O Sadhona ……., Vol. 4, 2017
76
Scheme 14
Raghunathan et al22. Studies on synthesis of novel polycyclic thiopyrano
coumarin/chromone frameworks through intramolecular domino Knoevenagel hetero Diels–
Alder reactions of 4-hydroxycoumarin and its benzo-analogous with suitable S-prenylated
pyrazole aldehydes.
Scheme 14
Scheme 15
Fillio et al23. synthesised chromanone derivative by Yb(OTf)3 catalysed annulation
reaction of phenol with5-alkylidene Meldram’s acids. Conjugate addition followed by
cyclization occurs here. (only electron rich phenols react to give corresponding product).
Scheme 15
Scheme 16
Skouta et al24. synthesized Isoflavone derivatives rapidly via the annulation of
salicylaldehyde and arylacetylenes followed by IBX/DMSO oxidation of the isoflavanones.
Scheme 16
+
O
OH
O
S
CHOR
NN
54-91%
O O
S
N NR
O
H
H
O O
O S
N
NH
H
R
+
OMe
OHMeO
O
O O
O R2
R1+
Yb(OTf)3
CH3NO2,
100oC, 1.5 hr
(71-83%)
O
O
R2
R1
OMe
MeO
R2AuCN
O
R1
R2+
OH
R1
O[O]
O
O
R1
R2
O
Toluene, 150oC, 36 hr
IBX/DMSO85oC,
48 hr
45-63%
Mandal, T. K.: Some novel synthesis of……
77
Scheme 17
Zhang et. al25. synthesized a series of 2-methylchromanone derivatives by using
palladium-catalyzed Wacker-type oxidative cyclization, in which a 1,5-hydride alkyl to
palladium migration and a direct chirality transfer were involved.
Scheme 17
Scheme 18
Nguyen et al26.carried out acid-mediated ring-transformations of 5-alkylidene-2,5-
dihydropyrrol-2-ones, available by cyclization of 1,3-diketone dianions with bis(imidoyl)
dichlorides of oxalic acid, resulted in formation of functionalized pyran-4-ones, such as 5,6-
dihydrobenzo[h]chromones and 5,6,7,8-tetrahydrochromones.
Scheme 18
Scheme 19
Šket et al27. synthesised flavanone derivative by photochemical reaction of 2-halo-
substituted 1,3-diarylpropan-1,3-dione. The photochemical behaviour of this type of
compounds grately depend on the natutre og halogen and electron donating group present in
aromatic ring. In this reaction 2-choloro-2-fluro derivatives resulted 3-fluoroflavanone. 2-
chloro-1,3-diphenylpropan-1,3-dione cyclized to flavanones.
X= H, F
Scheme 19
OPd(OAc)2, K2CO3
EtOH, H2O, 35oC, 24 hr
OH
HO
O
H(D)
H H(D)
OLi OLi N
N Cl
Cl R
R
O
N
N
O
R
R
H
HCl, THF O
O
O
NHR
(37-95%)
OO
X Cl
R2
R3
R4
R1
CH3CN
hv
(45-55%)
R2
O
O
X
R1
R3
R4
Prajnan O Sadhona ……., Vol. 4, 2017
78
Scheme 20
Oxidative cyclization of 2′-hydroxychalcones by employing FeCl3.6H2O–methanol
under mild conditions for the synthesis of flavone derivatives was developed by K. H. Kumar
et al28.
Scheme 20
Scheme 21
Médebielle et al29. sythesized fluorinated 4H-benzo[h]chromen-4-one and 4H-
pyrano[3,2-h]quinolin-4-one derivatives in moderate to good yields, through a one-pot
aldolization–intramolecular SNAr process from the tetrakis(dimethylamino)ethylene (TDAE)
mediated reductive cleavage of two N,N-dimethylamino-bis-chlorodifluoroacetyl substrates in
the presence of heteroaryl aldehydes.
Scheme 21
Scheme 22
Bennardi et al30. reported the use of bulk and silica-supported Wells-Dawson acid
(H2P2W18O62.24H2O) as reusable, heterogeneous catalysts to obtain substituted flavones and
chromones. The cyclization of 1-(2-hydroxyphenyl)-3-aryl-1,3-propanediones was carried out
O
O
R
X
O
RFeCl3.6H2O
MeOH
N
OMe
R
N
OR
FeCl3.6H2O
MeOH
Reflux, 8-10 hrs Where X= OH.
Where X= NH2
Reflux, 5-7 hrs
(55-62%)
(55-78%)
X
COCF2Cl
NMe2O
CF2ClTDAE
ArCHOX
COCF2CHOHAr
O
OF
Ar
X
Y
NMe2
O
F
F
ArH
-O
X
Y
Me2N
O
F
F
ArH
O
-
TDAE
ArCHO
Y = COCF2CHOHAr
18-65%
Mandal, T. K.: Some novel synthesis of……
79
by the catalst. In the reaction toluene was used as solvent. The catalysts were easily recycled
and reused without loss of their catalytic activity. The presented synthetic method is a simple,
clean and environmentally friendly alternative for synthesizing substituted flavones and
chromones.
Scheme 22
Scheme 23
Muthukrishnan et al31. synthesized bis-spirochromanones from 4,6-diacetyl resorcinol
in one-pot by carrying out the Kabbe condensation in room temperature ionic liquid.
Scheme 23
Scheme 24
A series of fluorinated flavanone derivatives were synthesized by S. Zhu et al32. with
excellent diastereoselectivities under mild reaction conditions via one pot tandem procedure
procedure involving a proline-catalyzed Knoevenagel condensation, a Michael addition, and
an electrophilic fluorination by NFSI.
Scheme 24
Scheme 25
Capretta et al33. synthesized flavanone derivatives using Palladium complexes of
1,3,5,7-tetramethyl-2,4,8-trioxa-6-phenyl-6-phosphaadamantane which was effective catalytic
systems facilitating the sequential application of a microwave-assisted Sonogashira and
carbonylative annulation reaction for the preparation of substituted flavanones.
Scheme 25
OH
I
R + H C C R1
Pd2 (dba)3 / Pa-Ph
DMF, DBU
MW, 30 min
O
R
R1
O
OH
Ar
O O
O
O
ArH2P2W18O62
.24 H2O
110oCTolune,
(82-88%)
COCH3
OHHO
H3COCN
N Bu
BuBr
-
Cyclic or acyclic ketoneOO
OO
RR
R R
(58-84%)
R2
OH
O
OR
1
O
+ R3CHO
i) Proline, EtOH, rt
ii) NFSI, Na2CO3
O
O
R2
R3
CO2R1
F
Prajnan O Sadhona ……., Vol. 4, 2017
80
Scheme 26
X. Zhu et al34. described an efficient, mechanically activated solid-state synthesis of
flavones from 1-(2-hydroxyphenyl)-3-aryl-1,3-propanediones using high-speed ball milling.
This method has notable advantages in terms of good yield, short reaction time, and neat
conditions.
Scheme 26
Scheme 27
L-G Meng et al35. developed a facile synthesis of 2-alkyl-substituted chromanones
from ortho-acylphenols and terminal alkynoates. The method contains two
Scheme 27
consecutive processes in one-pot reaction through a DABCO-catalyzed condensation reaction
and a KOBut-mediated intramolecular cycloaddition to afford the desired products
Scheme 28
C. S. López et al36. developed a method of synthesis of chroman derivative from aryl
3-methy-2-butenoate esters through biphasic base catalysis-mediated photo-Fries
rearrangement reaction in good to high yield and in short reaction times (30–120 min) in a one-
pot photochemical reaction.
Scheme 28
OH
O O
R1
R2
KHSO4
HSBM O
O
R1
R2
R
O
OEt+
DABCO (10 mol%)
KOBut, DMF, rt, 2.5 hr
O
R
O
CO2Et
O
CH3
OH
38-76%
O
OCyclohexane, KOH
O
OLight
95%
OH
O
O-
O
Photo-FriesRearrangement
Intramolecular oxa-Michael cyclisation
Mandal, T. K.: Some novel synthesis of……
81
Scheme 29
Vedachalam et al37. developed an efficient strategy for the carbon-carbon bond
formation between aldehyde and nitrile intramolecularly using an N-heterocyclic carbene
catalyst. They described the formation of 3-amino chroman derivatives in good to eccellent
yields(80-90%)
Scheme 29
Scheme 30
E. A. Hillard et al38. Synthesized cytotoxic ferrocenyl flavones via a ferricenium-
mediated 1,6-oxidative cyclization of 2′-hydroxyferrocenyl chalcones. An oxidation of the
ferrocenyl group of 2′-hydroxyferrocenyl chalcones activates the β-position of the unsaturated
ketone to nucleophilic attack to yield the first examples of ferrocenyl flavones.
Scheme 30
Scheme 31
Mallik et al39. developed synthesis flavanones starting either from 2′-hydroxychalcones
using anhydrous potassium carbonate as an inexpensive, safe, and efficient basic catalyst. The
favored reaction condition was either refluxing in a solvent with added catalyst or microwave
irradiation on the catalyst.
Scheme 31
NN
N
Ph
BF4
DBU, 10 mol %
CH2Cl2, rt
+
-
RC
O
ON
R
O
O
NH280-95%
N
N
Ph
+
OHO
CN
_
R
R
O
O
NH
H
NN
Ph..
+
Base
O
OH
R2
R1Fe
NaH, AgOTf
THF, rt
O
O
R2
R1
Fe
80-90%
R4
R3
OH
O
R2
R1
R4
R3
O
O
R2
R1
Anhydrous K2CO3
Acetone, reflux (3-5 hr.)
Anhydrous K2CO3
MW(3-5 min.)
Prajnan O Sadhona ……., Vol. 4, 2017
82
Scheme 32
Venkatesan and Maruthavanan synthesized chroman derivatives containing heteroaryl
moiety in C-2 position by oxidative cyclization of 2’-hydroxy chalcone using DDQ/DMSO-I2
/diphenyl disulfide40. The biological activity of flavone has been enhanced by introducing
heteroaryl moiety in C-2 position of chromone derivatives. Thus, 2-(1H-Indol-3-yl)-4H-
chromen-4-one derivatives and 2-(2- chloroquinolin-3-yl)-4H-chromen-4-one derivatives
were synthesized from corresponding chalcone. Both the compounds have biological activity.
Scheme 32
Scheme 33
Jarho et al41.synthesized a series of bilogically active chroman derivatives. They
synthesized the derivatives in a one step procedure including a base catalyzed aldol
condeasation using microwave irradiation.
Scheme 33
Scheme 34
Taheri et al42. synthesized a series of chroman derivatives by using sulfone-containing
Brønsted acid ionic liquid as catalyst. The reactions were performed under solvent-free
conditions, and the only by-product was water. The Brønsted acid ionic liquid could be
recovered and reused without significant loss of its activity.
Scheme 34
OH
O
CH3
H
O
Het
Piperidine / EtOH
OH
O
Het
R1
R2
R3
R4
R1
R2
R3
R4
DDQ
DMSO / I2
Ph-S-S-Ph
O
O
Het
R1
R2
R3
R4
R
O
OH
+
O
H R1
DIPA, EtOH
170oC, 1 h, MWR
O
O R1
CHO
R1
+
OH
R2
NH+
O2S
SO3H
CF3SO3-
O
R1
R2
CHO
OH +
NH
Ph
O
HN
Ph
Mandal, T. K.: Some novel synthesis of……
83
Scheme 35
Synthesis of a series of chroman derivatives was described by Y. Zhou et al43. They
described the chroman synthesis via a one-pot reaction of phenol, paraformaldehyde, and 5-
benzylimidazolidin-4-one mediated by p-nitrobenzoic acid.The chroman derivatives
containing spirocyclic N,O-acetal skeleton can be obtained in moderate to good yields (up to
89%) with good to excellent diastereoselectivities.
Scheme 35
Scheme 36
Zhang et al. synthesized 4-carbonyl chroman derivatives with high yield . A Rh-
catalyzed intramolecular aromatic C–H insertion of α-diazo β-ketoesters was developed in this
process44.
Scheme 36
Scheme 37
Kamat et al45. described in the synthsis 2-substituted or 2,2-disubstituted chromans and
4-aryl-3,4-dihydrobenzopyran-2-ones via [3+3] cyclocoupling. For the synthesis of chromans,
phenols and allylic alcohols were refluxed in chloroform in presence of 20 mol % I2 while
[3+3] cyclocoupling of phenols and cinnamic acids proceeded to give 4-aryl-3,4-
dihydrobenzopyran-2-ones using 30 mol % I2. Later reaction occurs via a tandem
hydroarylation–esterification process at 120–130 °C under solvent free conditions. Chromans
were obtained in 20–92% yields and substituted 4-aryl-3,4-dihydrobenzopyran-2-ones were
obtained in 5–85% yields.
Scheme 37
OR3
N
N
R1
R2
O
R2
HN
N R1
O
+ (HCHO)n +
OH
R3
p-nitrobenzoic acid
100oC
R1
O
N2
OR2
O ORh
R1
OH
O
COOR2
OH
R
R'
"ROH
30 mol % I2
CHCl3, reflux
ArCOOH
20mol % I2
120o-130oC
O R"
R'R
O
R
O
Ar
Prajnan O Sadhona ……., Vol. 4, 2017
84
Scheme 38
Arumugam et al46. described the easy method for the regioselective synthesis of internal
alkenes through a dehydrative cross-coupling and direct coupling procedure using the
environmentally benign Ca(II) catalyst. Several alkenes and alcohols underwent the coupling
reaction under solvent-free conditions in a short time to produce the desired alkenes. Applying
this protocol they synthesized novel benzopyran molecules through a cascade strategy.
Scheme 38
Scheme 39
A facile photochemical preparation of 5-, 6-, and 7-substituted chroman-4-ones from
aryl 3-methyl-2-butenoate esters were described by S.M. Bonesi et al47.
Scheme 39
Scheme 40
Luthma et al48. synthesized tricyclic N-benzylated chroman-4-one
tetrahydropyrimidine derivatives through a multi-component reaction between various 2-
substituted chroman-4-one derivatives, N-methylenebenzylamine and a catalytic amount of
proline under mild reaction conditions.
Scheme 40
CH3 X
R1
OH
+Ca(OTf)2
X=H, R1 = Me
X=H
R1 R2
R3
R2
R3
or
R3R2
HO
X=OH
O
R1
R2
R3
R
O
Ohv, cyclohexane
KOH, 10% aq., 25oC, Ar
R
O
O
R
O
O-
O
Cl
Br
O
R O
Cl
Br
BnN
R
NBn
+O
Cl
Br
BnN NBn
R
Mandal, T. K.: Some novel synthesis of……
85
Conclusion
4H-1-Benzopyran derivatives show vast array of biologically activity and have been
used in traditional eastern medicine for thousands of years The importance and vastness of the
areas of biological activities, development of newer synthesis of different benzopyran
derivatives and different transformations of benzopyran derivatives are very much important.
Acknowledgment
The author acknowledges Prof. Asok Kumar Mallik, Research guide, Department of
Chemistry, Jadavpur University, for giving valuable suggestions during writing this review.
Author also thanks departmental colleague for their support.
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