Molecular iodine catalyst promoted synthesis of chromans and 4-aryl-3,4-dihydrobenzopyran-2-ones via [3+3] cyclocoupling

Article abstract of DOI:10.1016/j.tet.2014.05.093

Molecular iodine as an inexpensive catalyst is described in the construction of 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 % I₂while [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.

Full text of DOI:10.1016/j.tet.2014.05.093

Accepted Manuscript
Molecular Iodine Catalyst Promoted Synthesis of Chromans and 4-Aryl-3,4-
dihydrobenzopyran-2-ones via [3+3] Cyclocoupling
Mayuri M. Naik , Durga P. Kamat , Santosh G. Tilve , Vijayendra P. Kamat
PII:
S0040-4020(14)00799-6
10.1016/j.tet.2014.05.093
TET 25642
DOI:
Reference:
To appear in: Tetrahedron
Received Date: 6 February 2014
Revised Date: 8 May 2014
Accepted Date: 23 May 2014
Please cite this article as: Naik MM, Kamat DP, Tilve SG, Kamat VP, Molecular Iodine Catalyst
Promoted Synthesis of Chromans and 4-Aryl-3,4-dihydrobenzopyran-2-ones via [3+3] Cyclocoupling,
Tetrahedron (2014), doi: 10.1016/j.tet.2014.05.093.
This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to
our customers we are providing this early version of the manuscript. The manuscript will undergo
copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please
note that during the production process errors may be discovered which could affect the content, and all
legal disclaimers that apply to the journal pertain.

ACCEPTED MANUSCRIPT
Graphical Abstract
Molecular iodine catalyst promoted synthesis
of chromans and 4-aryl-3,4-
Leave this area blank for abstract info.
dihydrobenzopyran-2-ones via [3+3]
cyclocoupling
Mayuri M. Naik, Durga P. Kamat, Santosh G. Tilve∗ and Vijayendra P. Kamat
Department of Chemistry, Goa University,
Taleigao-Plateau, Goa 403 206, India
OH
R''
COOH
OH
O
O
Ar
R''
R'
O
2
R'
4
R
R
2
0 mol% I2
30 mol% I2
CHCl , reflux
o
R
1
20-130 C, neat
5-85%
Ar
3
1
3
5
2
0-92%
1

ACCEPTED MANUSCRIPT
Molecular Iodine Catalyst Promoted Synthesis of Chromans and 4-Aryl-
3
,4-dihydrobenzopyran-2-ones via [3+3] Cyclocoupling
Mayuri M. Naik, Durga P. Kamat, Santosh G. Tilve∗ and Vijayendra P. Kamat
Department of Chemistry, Goa University, Taleigao-Plateau, Goa 403 206, India
*Phone: 0832-6519317; Email: stilve@unigoa.ac.in; santoshtilve@yahoo.com;
Key words: Chroman, 3,4-Dihydrobenzopyran-2-one, Iodine, Cyclocoupling, Solvent-free,
Phenol, Allylic alcohol, Cinnamic acid
Abstract: Molecular iodine as an inexpensive catalyst is described in the construction of 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% I
2
while [3+3] cyclocoupling of phenols and cinnamic
. Later
acids proceeded to give 4-aryl-3,4-dihydrobenzopyran-2-ones using 30 mol% I
2
reaction occurs via a tandem hydroarylation–esterification process at 120-130 ⁰C 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.
1. Introduction: Molecular iodine is a mild Lewis acid used in plethora of functional group
transformations in organic synthesis either as a catalyst or in stoichiometric amount and many
1
reviews have documented its applications. A large number of heterocycles such as
benzofurans, furans, benzothiophenes, thiophenes, benzopyrans, benzoselenophenes,
selenophenes, α-pyrones, isocoumarins, isoxazoles, chromones, β-lactams, 2,3-
dihydropyrroles, pyrroles, furopyridines, furanones, and isochromenes have been prepared by
iodine-mediated domino or one-pot multicomponent reactions. Iodine has gained
considerable attention as it is readily available, non-toxic, cheap, easy to handle and, hence
has become a preferred alternative for toxic and expensive acid catalysts. Also it has high
tolerance to air as well as moisture and can be easily removed from reaction systems by
washing with reducing agents.
2
Continuing our interest in catalytic usage of iodine for the synthesis of heterocycles, we in a
preliminary communication reported the synthesis of 4-aryl-3,4-dihydrobenzopyran-2-ones
2b
via the [3+3] cyclocoupling of phenols with cinnamic acids (Scheme 1). Herein we disclose
full account of our work in exploring iodine as catalyst for the synthesis of chromans and 4-
2

ACCEPTED MANUSCRIPT
aryl-3,4-dihydrobenzopyran-2-ones. 3,4-Dihydrobenzopyran-2-ones or dihydrocoumarins are
3
4
5
well known for fragrance in cosmetics, food flavouring and perfumery industries. 4-Aryl-
6
3
,4-dihydrocoumarins are naturally occurring compounds exhibiting some interesting
7
8
9
biological activities such as aldose reductase inhibition, antiherpetic, protein kinases and
are important synthetic intermediates for pharmaceutical compounds. Many methods are
1
0
reported for the synthesis of dihydrocoumarins.
Dihydrobenzopyran (chroman) ring system constitutes the basic unit in number of naturally
1
1
occurring biologically active scaffolds. It prevalently appears in important bioactive
12
13
compounds such as vitamin E or α-tocopherol, flavonoids, etc. Many chroman derivatives
14
15
are used as antioxidants for fats and oils and some exhibit weak estrogenic activity.
Owing to this property they have attracted the attention of several chemists in recent years
and are important drug targets. Most of the reported routes couple phenols and dienes by
1
6
homogenous or heterogenous acids as catalyst which is an atom economical way of
constructing these heterocycles. Cyclocoupling of phenol derivatives with other unsaturated
17
18
compounds like allylic alcohols, allylic halides have also appeared. Direct aromatic
19
carbon-oxygen bond formation reactions leading to chromans are also well known.
Recently devised environmentally sound catalytic systems include annulations of phenols
16m
with 1,3-dienes using AgOTf under mild reaction conditions,
3
recyclable Sc(OTf) /ionic
16n
16o
liquid and Cu(OTf) -bipy, cyclocoupling of phenols with allylic alcohols using Mo/o-
2
17d
17e
17f
19e
chloranil,
CuAl-SBA-15, PPh
3
AuNTf
2
,
6
and allyl prenyl ethers using Mo(CO) .
Conventional methods make use of either hazardous or costly catalysts which prompted us to
devise the chroman synthesis using an environmentally benign inexpensive iodine catalyst.
2. Results and discussion:
HO
O
OH
O
O
2
0 mol% I2
R
R
+
o
1
20-130 C, neat
Ar
Ar
1
2
3
Scheme 1. Reaction of phenol with cinnamic acid.
Our work commenced with the synthesis of 4-aryl-3,4-dihydrobenzopyran-2-ones (Scheme
). Initial studies were done using β-naphthol and cinnamic acid. Solvent studies proved
1
xylene to be the best solvent in refluxing condition to give maximum yield of 70% after 5 h.
0
Under solvent-free condition at 120-130 C maximum yield of 80% was isolated after 1 h.
3

ACCEPTED MANUSCRIPT
Hence further studies were done for solvent-free condition only. Iodine concentration was
also optimized wherein 20 mol% was found to be optimum to give maximum yield of the
product and without iodine no product was observed even after heating for 24 h. Generality
of this reaction was proved by synthesizing the following derivatives (Table 1). Several
electron rich phenols with substituted methyl group were rapidly converted into
dihydrocoumarins in good yields (3b-3h). Quinol rapidly converted to give product (3i) in
good yield. Parent phenol gave 60% yield of product (3j) in 4 hours while α- naphthol gave
product (3k) in 65% yield. Also, electron deficient p-chlorophenol gave the product (3l) in
good yield (70%). However phenols with strong electron withdrawing nitro groups at para
and meta positions resulted in formation of the corresponding nitro phenyl cinnamates (3m
and 3n) instead of expected dihydrocoumarins after 24 hours in low yields. Similarly p-
fluorophenol resulted in the formation of ester (3o) in 50% yield. Resorcinol gave a mixture
of two regioisomeric dihydrocoumarins (3p) in 5:1 ratio. Bisphenol A gave a complex
mixture from which 5% of product dihydrocoumarin (3j) was separated. The formation of
dihydrocoumarin could be explained by the concomitant dearylation. The reaction was also
performed with substituted cinnamic acids resulting in a series of dihydrocoumarins (3q-3z).
4-methoxy cinnamic acid smoothly reacted with various phenols to give dihydrocoumarins
(3q-3u) in good yields. Similarly 3,4-dimethoxy cinnamic acid underwent cyclization to form
desired products (3v-3y) in good yields whereas 3,4,5-trimethoxy cinnamic acid on reaction
with 3,5-dimethyl phenol gave the corresponding dihydrocoumarin (3z) in 63% yield. The
reaction of acrylic acid with m-cresol failed to give the corresponding dihydrocoumarin. The
formation of dihydrocoumarins could be accounted via esterification followed by
hydroarylation pathway.
Table 1. Various 4-aryl-3,4-dihydrobenzopyran-2-one derivatives 3a-l, p-z and substituted
phenyl cinnamates 3m-o produced under optimized reaction conditions
a
Entry
Substituted Phenol
Product
Time (h)
Yield(%)
1
1a
1b
3a
3b
1
80
Ph
O
OH
O
2
1
83
O
O
OH
H C
H C
3
3
Ph
4

ACCEPTED MANUSCRIPT
3
4
1c
3c
1.5
78
60
H C
O
O
H C
OH
3
3
Ph
1d
3d
3e
3f
3
CH3
CH3
OH
O
O
Ph
CH3
5
6
1e
1f
4
5
83
65
CH3
H C
OH
H C
O
O
3
3
Ph
CH3
CH3
CH3
OH
O
O
CH3 Ph
7
1g
3g
2
85
H C
O
O
3
H C
OH
OH
3
CH3 Ph
O
CH3
8
9
1h
1i
3h
2
2
85
77
H C
O
3
H C
3
H C
3
H C
3
Ph
O
3i
OH
O
HO
HO
Ph
1
1
0
1
1j
3j
4
4
60
65
O
O
OH
OH
Ph
O
1k
3k
O
Ph
1
2
1l
3l
3
70
OH
O
O
Cl
Cl
Ph
5

ACCEPTED MANUSCRIPT
1
1
3
4
1m
3m
24
24
20
30
OH
O
Ph
Ph
O
O N
O N
2
2
1n
3n
O N
O
O N
OH
2
2
O
1
1
5
6
1o
3o
24
50
70
OH
O
Ph
O
F
F
1p
HO
3pa:3pb (~5:1)
5
OH
O
O
HO
O
O
+
Ph
OH Ph
1
1
7
8
1q
3j
10
5
H C
O
O
3
OH
HO
CH3
Ph
b
1a
3q
4
85
OH
(4-OMe) H C
4
6
O
O
b
1
2
9
0
1b
1r
3r
1.5
78
68
OH
OH
O
O
H C
H
3
C
3
C H ( 4-OMe)
6
4
b
3s
4
O
O
O
O
O
O
C H (4-OMe)
6
4
b
2
2
1
2
1g
1e
3t
3
1
82
83
H C
O
O
3
H C
OH
3
CH3 C H (4-OMe)
6
4
CH3
CH3
b
3u
CH
3
H C
O
O
H C
OH
3
3
C H (4-OMe)
6
4
6

ACCEPTED MANUSCRIPT
c
2
2
2
3
4
5
1a
3v
1.45
80
72
77
(
3,4-di OMe) H C
O
OH
OH
3 6
O
c
1i
3w
4
O
O
HO
HO
C H (3,4-di OMe)
6
3
c
1g
3x
2
H C
OH
3
H C
O
O
3
CH3
CH3 C H (3,4-di OMe)
6
3
c
2
6
1e
3y
2
60
CH3
CH3
H C
OH
3
H C
O
O
3
C H (3,4-di OMe)
6
3
d
2
7
1g
3z
2.3
63
H C
OH
H
3
C
O
O
3
CH3 C H (3,4,5-tri OMe)
CH3
6 2
a
b
c
d
Isolated % yield after column chromatography.
In this case 4-methoxy cinnamic acid was used.
In this case 3,4-dimethoxy cinnamic acid was used.
In this case 3,4,5-trimethoxy cinnamic acid was used.
We then conceived that the Lewis acidity of iodine can be put to use for the synthesis of
chromans (Scheme 2).
H C
CH3
3
CH3
CH3
OH
30 mol% I2
O
R
R
+
CHCl , reflux
3
OH
1
4a
5
Scheme 2. Reaction of substituted phenols with prenyl alcohol.
At the outset we examined the effect of iodine catalyst (30 mol%) on cyclization of β-
naphthol (1a) and prenyl alcohol (4a) as substrates at room temperature in chloroform. After
prolonged stirring some formation of product chroman 5a was observed. To reduce the time,
7

ACCEPTED MANUSCRIPT
the reaction was refluxed wherein product formation was observed within 1 hour. Next we
examined the stoichiometry of substrates. It was observed that when phenol was used in
excess (4 equivalents) optimum yield of 92% was observed after 4 hours (Table 2, entry 4).
Use of excess of prenyl alcohol led to a complex mixture.
Table 2. Optimization of stoichiometry of starting materials 1a and 4a
a,b
Entry
1a
4a
Time (h)
% yield
1
2
3
4
5
1
2
3
4
5
1
1
1
1
1
4
4
4
4
4
78
80
88
92
85
a
Isolated yields based on substrate 4a
b
Trace amount of 5a’ (figure 1) was formed
I
CH
3
CH
3
O
Figure 1. Structure of 5a’.
Optimization of iodine concentration was studied by varying the amount of iodine (Table 3).
No product formation was observed in the absence of iodine (entry 1). When 10 mol% iodine
was used, the formation of 5a was seen and the product yield was found to increase with
increase in catalyst loading and with reduction in time. 30 Mol % of iodine in refluxing
chloroform was found to be the optimum concentration (entry 4). Further increase in iodine
concentration resulted in decreased product yield (entry 5). When the reaction was carried out
with stoichiometric amount of iodine at room temperature with 1:1 ratio of 1a:4a the
formation of mixture of 3,3-dimethyl-2,3-dihydro-1H-benzo[f]chromene (5a) and 2-iodo-3,3-
dimethyl-2,3-dihydro-1H-benzo[f]chromene (5a’) in ~1.2:1 ratio was observed.
Table 3. Optimization of iodine concentration in refluxing chloroform
a
Entry
1
Iodine (mol %)
0
Time (h)
24
% yield
0
8

ACCEPTED MANUSCRIPT
2
3
4
5
6
10
20
24
24
4
85
89
30
92
40
2
79
b
c
100
1.3
58, 31
a
Isolated yields of 5a based on substrate 4a
b
Reaction carried out at room temperature
c
%
yield of 5a’
Effect of solvents was studied by carrying out this reaction in different solvents (Table 4).
Formation of product was seen in almost all solvents. Refluxing in protic solvents like
ethanol and methanol found to require longer time. Better results were obtained in chlorinated
solvents like chloroform and dichloromethane with less duration of time, of which
chloroform was giving maximum yield. Other solvents like toluene, tetrahydrofuran, 1,4-
dioxane, 1,2-dichloroethane and acetonitrile resulted in moderate yields.
Table 4. Solvent screening
a
Entry
Solvent
Time (h)
% yield
1
2
3
4
5
6
7
8
9
Methanol
Ethanol
24
24
4
50
45
92
90
30
65
60
68
25
Chloroform
Dichloromethane
Toluene
4
24
7
Tetrahydrofuran
1,4-Dioxane
1,2-Dichloroethane
Acetonitrile
7
5
24
a
Isolated yields based on substrate 4a
Inorder to explore the generality of this reaction, various phenols were subjected to the
optimum reaction condition (Table 5). The reaction of ß-naphthol with 4a and 2-methylbut-3-
en-2-ol 4b gave chroman (5a) in 92% and 87% yields respectively. Electron rich phenols
were converted to respective chromans (5b-5e) in good to moderate yields. Similarly 3,4-
methylenedioxyphenol underwent cyclization readily to afford chroman (5f). Naturally
9

ACCEPTED MANUSCRIPT
20
occurring dihydrolapachenole (5g) isolated from Tabebuia chrysantha was synthesised from
-methoxynaphthol in good yield. Dihydroxy compounds like resorcinol and quinol which
4
are insoluble in chloroform, when refluxed in methanol afforded respective chromans (5h)
and (5i) in moderate yields. Resorcinol resulted exclusively in one isomer (5h). Similarly
phloroglucinol in refluxing methanol afforded chroman (5j) in 56% yield. p-Chlorophenol
was converted to corresponding chroman (5k) in low yield. The slow reaction and low yield
is attributed to the electron withdrawing effect of chloro group. Also, we examined the
reaction of ß-naphthol with phytol 4c and cinnamyl alcohol 4d to afford desired chromans
(5l) and (5m) respectively in good yields.
Table 5. Various chroman derivatives 5a-m produced under optimized reaction conditions
a
Entry
Substituted Phenol
Product
Time (h) Yield(%)
b
1
1a
1b
5a
4
92, 87
CH3
CH3
OH
O
2
3
4
5
5b
5c
5d
5e
4
2
4
4
48
77
58
45
CH3
CH3
OH
O
O
H C
H C
3
3
1c
CH3
CH3
MeO
MeO
OH
MeO
MeO
1d
CH3
O
CH3
OH
MeO
MeO
1e
MeO
CH3
CH3
OH
MeO
O
6
7
1f
5f
4
2
58
60
CH
OH
O
3
O
O
O
CH
3
O
1g
5g
CH
3
O
OH
CH3
MeO
MeO
10

ACCEPTED MANUSCRIPT
*
8
9
1h
HO
5h
4
4
46
33
CH3
HO
O
CH3
OH
OH
*
1i
5i
5j
CH3
CH3
O
HO
HO
HO
1j
*
1
0
4
56
CH3
O
HO
OH
CH3
HO
OH
1
1
1
2
1l
5k
5l
24
20
OH
CH
CH
3
O
3
Cl
Cl
c
1a
4
76
CH3
CH3
3
OH
OH
O
CH3
d
1
3
1a
5m
4
60
Ph
O
a
Isolated % yield after column chromatography based on unsaturated alcohol substrate
b
c
d
2
-methylbut-3-en-2-ol 4b, phytol 4c, cinnamyl alcohol 4d were used
Reaction carried out in methanol
Unreacted and excess phenols were recovered.
*
As a further application to our work, synthesis of naturally occurring precocene II 5ca and
lapachenole 5ga was performed (Scheme 3). 5ca is an insect growth regulator, genotoxic and
21
produces hepatic centrolobular necrosis in rats whereas 5ga has been used as a fluorescent
22
23
photoaffinity label as well as shown to have cancer chemopreventive activity. Chroman 5c
24
was refluxed in benzene with DDQ for 6 hours to give 5ca in 60% yield. Similarly chroman
g on refluxing for 1.3 h in benzene delivered 5ga in 52% yield.
5
11

ACCEPTED MANUSCRIPT
MeO
MeO
O
MeO
O
DDQ
Benzene, reflux, 6h MeO
0%
6
5c
5ca
O
O
DDQ
MeO
Benzene, reflux, 1.3h MeO
52%
5g
5ga
Scheme 3. Synthesis of precocene II 5ca and lapachenole 5ga.
R'
R'
O
R''
H
O
R"
R
I
I
H
I
I
cat I2
- H-O-I
I
H
O
-
O
- I
path A
R''
H
R'
excess I2
R'
O
O
R''
+ H I + I O
R'
R
R
I
I-
R
H
2
H C
R''
H
H
path B
2
-H O
-I
2
R'
R'
O
R''
O
R''
I
O
R'
R''
I
R
R
HI
R
5
5'
5''
not observed
Scheme 4. Proposed mechanism for the formation of chromans
The proposed mechanistic pathway for the formation of chroman is shown in scheme 4. Loss
of alcoholic OH group takes place by coordination of iodine making it a better leaving group
facilitated by allylic double bond. Intermolecular electrophillic attack by the phenolic arene
ring on less hindered carbon atom of thus formed carbocation followed by intramolecular
oxygen attack on more substituted carbon atom of double bond and subsequent aromatization
delivered chroman. On the other hand if the double bond coordinates with iodine to form
12

ACCEPTED MANUSCRIPT
iodinium ion prior to the intramolecular oxygen attack, oxygen attack can take place either by
path A or path B to give 5’ or 5’’ respectively. But the obtained product 5a’ indicates the
attack at more substituted carbon atom which is favoured when excess of iodine is used.
3. Conclusion
In summary, we have demonstrated utility of molecular iodine as mild Lewis acid for the
synthesis of important oxygen heterocycles 4-aryl-3,4-dihydrocoumarins and chromans via
cyclocoupling. The usefulness of the method is demonstrated by synthesis of naturally
occurring chroman dihydrolapachenole 5g. Further these chromans can be used for the
synthesis of chromenes by conventional dehydrogenation which is demonstrated by synthesis
of precocene II 5ca and lapachenole 5ga.
4. Experimental
4.1. General remarks. All the dihydrocoumarins, chromans and chromenes formed were
1
13
characterized by spectral analysis (IR; H NMR; C NMR) and comparison of their melting
points with the literature reports. Commercial reagents were used without further purification
except p-methoxyphenol and m-methoxyphenol which were prepared using standard
procedure from respective dihydroxy compounds. Solvents were distilled prior to use.
1
13
Column chromatography was performed on 60-120 mesh silica gel. H (400 MHz) and C
100 MHz) NMR spectra were recorded on a Bruker AVANCE 400 instrument in CDCl as
(
3
solvent and TMS as an internal standard. Infrared Spectra (IR) were recorded in a Shimadzu
FTIR instrument. Elemental analyses were carried out using Elementar Variomicro Cube
CHNS Analyser. High resolution mass spectrum (HRMS) was recorded on a Micro Mass
ESQTOF Mass spectrometer at IISc, Bangalore. Melting points are uncorrected. Coupling
constants are reported in Hz.
4.2. General procedures
(I) General procedure for the synthesis of dihydrocoumarins.
Iodine (0.13 mmol) was added into a mixture of phenol (0.69 mmol) and cinnamic acid (0.69
mmol) under an air atmosphere and the mixture was neat heated at 120-130 ⁰C for a period of
time (1-4 hours). Following completion of the reaction as monitored by TLC, the reaction
mixture was cooled, diluted with ethyl acetate, washed with aqueous sodium thiosulphate
solution and dried over sodium sulphate. The solvent was removed under vacuum to provide
13

ACCEPTED MANUSCRIPT
the crude products. Further purification was done by column chromatography on silica gel
with hexanes/ethyl acetate (4:1) as an eluent.
(II) General procedure for the synthesis of chromans.
In a 50 mL round bottom flask, prenyl alcohol (1.16 mmol) was mixed with chloroform (10
mL). To it, substituted phenol (4.0 equivalence) and iodine (0.3 equivalence) were added at
room temperature. This reaction mixture was subjected to reflux with stirring for 4 hours. It
was then cooled to room temperature. Chloroform was directly washed with saturated
solution of sodium thiosulphate followed by dilute sodium hydroxide solution. Finally
chloroform layer was washed with water, dried over sodium sulphate and concentrated to
furnish the crude product. This was then purified using 60-120 mesh silica gel column
chromatography (hexanes-ethyl acetate) to give chroman.
(III) General procedure for the synthesis of chromenes.
To 3,4-dimethoxychroman (0.45 mmol) in a 50 mL round bottom flask, was added DDQ
0.45 mmol) and was subjected to reflux in benzene (10 mL). After completion of reaction,
(
benzene was removed by distillation and crude reaction mixture thus obtained was purified
by column chromatography (hexanes-ethyl acetate) to furnish chromene.
4.3. Experimental Procedures and Characterization:
Various 4-aryl-3,4-dihydrobenzopyran-2-one derivatives and substituted phenyl
cinnamates:
25
5,6-Benzo-4-phenyl-3,4-dihydrobenzopyran-2-one (3a)
Ph
O
O
2
5
A colourless solid (78% yield); mp 115-117 ⁰C; Lit 115-116 ⁰C; IR (KBr): νmax = 1778,
-1 1
1
764 cm ; H NMR (CDCl , 400 MHz): δ 3.16-3.27 (m, 2 H), 4.98 (d, J = 6.0 Hz, 1 H), 7.15
3
(d, J = 7.6 Hz, 2 H), 7.25-7.31 (m, 3 H), 7.38 (d, J = 9.2 Hz, 1 H), 7.48-7.52 (m, 2 H), 7.82
13
(
3 2
d, J = 8.0 Hz, 1 H), 7.90 (d, J = 8.8 Hz, 2 H); C NMR (CDCl , 100 MHz): δ 37.5 (CH ),
14

ACCEPTED MANUSCRIPT
37.7 (CH), 117.6 (CH), 117.7 (Cq), 123.1 (CH), 125.3 (CH), 126.9 (2 X CH), 127.5 (CH),
127.6 (CH), 128.8 (CH), 129.3 (2 X CH), 129.9 (CH), 131.0 (Cq), 131.1 (Cq), 140.6 (Cq),
149.8 (Cq), 167.2 (Cq).
2
6
6-Methyl-4-phenyl-3,4-dihydrobenzopyran-2-one (3b)
O
O
H C
3
Ph
26
-1 1
A colourless solid (83% yield); mp 80-83 ⁰C; Lit 83 ⁰C; IR (KBr) 1757 cm . H NMR
(CDCl
3
, 400 MHz) δ 2.28 (s, 3 H), 2.99-3.11 (m, 2 H), 4.32 (t, J = 6.8 Hz, 1 H), 6.81 (s, 1 H),
7.05 (d, J = 8.0 Hz, 1 H), 7.15 (d, J = 8.0 Hz, 1 H), 7.18 (d, J = 7.2 Hz, 2 H), 7.29-7.40 (m, 3
1
3
H); C NMR (CDCl , 100 MHz): δ 20.8 (CH ), 37.2 (CH ), 40.7 (CH), 116.9 (CH), 125.3
3
3
2
(Cq), 127.6 (2 X CH), 127.6 (CH), 128.7 (CH), 129.2 (2 X CH), 129.3 (CH), 134.4 (Cq),
140.5 (Cq), 149.7 (Cq), 167.9 (Cq).
2
7
7-Methyl-4-phenyl-3,4-dihydrobenzopyran-2-one (3c)
H C
O
O
3
Ph
27
-1
A colourless solid (78% yield); mp 124 ⁰C; Lit 124 ⁰C; IR (KBr): ν =1778, 1764 cm ;
max
1
H NMR (CDCl
.89 (q, J = 8.0 Hz, 2 H), 6.97 (s, 1 H), 7.17 (d, J = 7.6 Hz, 2 H), 7.28-7.32 (m, 3 H); C
NMR (CDCl , 100 MHz): δ 21.1 (CH ), 37.2 (CH ), 40.4 (CH), 117.5 (CH), 122.7 (Cq),
25.5 (CH), 127.6 (2 X CH), 127.6 (CH), 128.1 (CH), 129.1 (2 X CH), 139.2 (Cq), 140.6
Cq), 151.6 (Cq), 167.9 (Cq).
3
, 400 MHz): δ 2.38 (s, 3 H), 2.99-3.11 (m, 2 H), 4.33 (t, J = 6.8 Hz, 1 H),
13
6
3
3
2
1
(
2
8
8-Methyl-4-phenyl-3,4-dihydrobenzopyran-2-one (3d)
CH3
O
O
Ph
2
8
-1 1
A colourless solid (60% yield); mp 106-108 ⁰C; Lit 108 ⁰C; IR (KBr): νmax = 1764 cm ; H
NMR (CDCl , 400 MHz): δ 2.36 (s, 3 H), 2.99-3.10 (m, 2 H), 4.32 (t, J = 6.8 Hz, 1 H), 6.81
d, J = 7.6 Hz, 1 H), 6.98 (t, J = 7.6 Hz, 1 H), 7.15 (d, J = 7.2 Hz, 3 H), 7.26-7.33 (m, 3 H);
3
(
15

ACCEPTED MANUSCRIPT
1
3
C NMR (CDCl
25.9 (CH), 126.5 (Cq), 127.6 (2 X CH), 127.6 (CH), 129.1 (2 X CH), 130.3 (CH), 140.5
Cq), 150.0 (Cq), 167.9 (Cq).
3 3 2
, 100 MHz): δ 15.9 (CH ), 36.9 (CH ), 40.8 (CH), 124.2 (CH), 125.6 (Cq),
1
(
7,8-Dimethyl-4-phenyl-3,4-dihydrobenzopyran-2-one (3e)
CH3
H C
O
O
3
Ph
-1
1
A colourless solid (83% yield); mp 119-120 ⁰C; IR (KBr): νmax = 1768 cm ; H NMR
CDCl , 400 MHz): δ 2.27 (s, 3 H), 2.29 (s, 3 H), 3.00-3.03 (m, 2 H), 4.29 (t, J = 6.8 Hz, 1
H), 6.70 (d, J = 7.6 Hz, 1 H), 6.88 (d, J = 7.6 Hz, 1 H), 7.14 (d, J = 7.2 Hz, 2 H), 7.25-7.35
(
3
13
(
m, 3 H); C NMR (CDCl
23.1 (Cq), 124.9 (CH), 125.6 (CH), 127.5 (2 X CH), 127.6 (CH), 129.1 (2 X CH), 137.8
Cq), 140.7 (Cq), 149.8 (Cq), 168.2 (Cq), 168.2 (Cq).
3 3 3 2
, 100 MHz): δ 11.9 (CH ), 19.9 (CH ), 37.0 (CH ), 40.7 (CH),
1
(
28
5,8-Dimethyl-4-phenyl-3,4-dihydrobenzopyran-2-one (3f)
CH3
O
O
CH3 Ph
2
8
-1 1
A colourless solid (65% yield); mp 78-80 ⁰C; Lit 78 ⁰C IR (KBr): νmax = 1764 cm ; H
NMR (CDCl , 400 MHz): δ 2.14 (s, 3 H), 2.34 (s, 3 H), 3.02-3.04 (m, 2 H), 4.38-4.40 (dd, J
5.6, 3.6 Hz, 1 H), 6.89 (d, J = 7.6 Hz, 1 H), 7.03 (d, J = 6.8 Hz, 2 H), 7.09 (d, J = 7.6 Hz, 1
3
=
13
H), 7.21-7.28 (m, 3 H); C NMR (CDCl
8.3 (CH), 123.0 (Cq), 124.1 (Cq), 125.9 (CH), 127.0 (2 X CH), 127.4 (CH), 129.1 (2 X
CH), 130.1 (CH), 134.1 (Cq), 140.1 (Cq), 150.4 (Cq), 167.5 (Cq).
3 3 3 2
, 100 MHz): δ 15.8 (CH ), 18.6 (CH ), 37.6 (CH ),
3
2
6
5,7-Dimethyl-4-phenyl-3,4-dihydrobenzopyran-2-one (3g)
H C
O
O
3
CH3 Ph
2
6
-1 1
A colourless solid (85% yield); mp 130-132 ⁰C; Lit 134 ⁰C; IR (KBr): νmax = 1753 cm ; H
NMR (CDCl , 400 MHz): δ 2.16 (s, 3 H), 2.37 (s, 3 H), 3.01-3.11 (m, 2 H), 4.39 (d, J = 6.0
3
16

ACCEPTED MANUSCRIPT
1
3
Hz, 1 H), 6.86 (d, J = 5.6 Hz, 2 H), 7.06 (d, J = 7.6 Hz, 2 H), 7.22-7.31 (m, 3 H); C NMR
(CDCl , 100 MHz): δ 18.7 (CH ), 21.1 (CH ), 37.8 (CH ), 38.0 (CH), 115.5 (CH), 120.1
3 3 3 2
(Cq), 126.9 (2 X CH), 127.4 (CH), 127.4 (CH), 129.1 (2 X CH), 136.6 (Cq), 138.8 (Cq),
140.4 (Cq), 152.1 (Cq), 167.6 (Cq).
2
8
6,7-Dimethyl-4-phenyl-3,4-dihydrobenzopyran-2-one (3h)
H C
O
O
3
H C
3
Ph
2
8
-1 1
A pale yellow solid (85% yield); mp 110-113 ⁰C; Lit 111 ⁰C; IR (KBr): ν = 1759 cm ; H
max
NMR (CDCl
3
, 400 MHz): δ 2.17 (s, 3 H), 2.27 (s, 3 H), 2.97-3.09 (m, 2 H), 4.29 (t, J = 6.8
Hz, 1 H), 6.75 (s, 1 H), 6.94 (s, 1 H), 7.17 (d, J = 7.2 Hz, 2 H), 7.31 ( d, J = 7.2 Hz, 1 H),
1
3
7
.35-7.38 (m, 2 H); C NMR (CDCl
3 3 3 2
, 100 MHz): δ 19.1 (CH ), 19.6 (CH ), 37.4 (CH ), 40.5
(CH), 117.9 (CH), 122.5 (Cq), 127.5 (2 X CH), 127.5 (CH), 129.0 (CH), 129.1 (2 X CH),
133.0 (Cq), 137.5 (Cq), 140.9 (Cq), 149.7 (Cq), 168.1 (Cq).
29
6-Hydroxy-4-phenyl-3,4-dihydrobenzopyran-2-one (3i)
O
O
HO
Ph
2
9
-1
A colourless solid (77% yield); mp 125-130 ⁰C; Lit 133 ⁰C; IR (KBr): νmax = 3331 cm &
-1 1
1
741 cm ; H NMR (CDCl
3
, 400 MHz): δ 2.96-3.08 (m, 2 H), 4.27 (t, J = 6.8 Hz, 1 H), 5.55
(bs, 1 H), 6.43 (s, 1 H), 6.77 (d, J = 8.4 Hz, 1 H), 7.00 (d, J = 8.8 Hz, 1 H), 7.17 (d, J = 7.6
1
3
Hz, 2 H), 7.29-7.38 (m, 3 H); C NMR (CDCl , 100 MHz): δ 36.9 (CH ), 40.7 (CH), 114.7
3
2
(CH), 115.5 (CH), 118.0 (CH), 126.9 (Cq), 127.5 (2 X CH), 127.8 (CH), 129.2 (2 X CH),
139.9 (Cq), 145.4 (Cq), 152.6 (Cq), 168.5 (Cq).
2
7
4-Phenyl-3,4-dihydrobenzopyran-2-one (3j)
O
O
Ph
A colourless solid (60% yield from phenol and 5% yield from bisphenol A); mp 78-80 ⁰C;
2
7
-1 1
Lit 78 ⁰C; IR (KBr): ν = 1759 cm ; H NMR (CDCl , 400 MHz): δ 3.02-3.14 (m, 2 H),
max
3
17

ACCEPTED MANUSCRIPT
4
8
4
1
.37 (t, J = 7.2 Hz, 1 H), 7.00 (d, J = 7.6 Hz, 1 H), 7.11 (t, J = 7.6 Hz, 1 H), 7.15 (s, 1 H),
1
3
.40 (d, J = 7.2 Hz, 2 H), 7.32-7.35 (m, 4 H); C NMR (CDCl , 100 MHz): δ 37.0 (CH ),
3
2
0.7 (CH), 117.2 (CH), 124.7 (CH), 125.8 (Cq), 127.6 (2 X CH), 127.7 (CH), 128.4 (CH),
28.8 (CH), 129.2 (2 X CH), 140.3 (Cq), 151.7 (Cq), 167.7 (Cq).
28
7,8-Benzo-4-phenyl-3,4-dihydrobenzopyran-2-one (3k)
O
O
Ph
28
-1 1
A pale yellow solid (65% yield); mp 112 ⁰C; Lit 112 ⁰C; IR (KBr): νmax = 1762 cm ; H
NMR (CDCl , 400 MHz): δ 3.14-3.26 (m, 2 H), 4.51 (s, 1 H), 7.13 (d, J = 8.0 Hz, 1 H), 7.20
d, J = 6.4 Hz, 2 H), 7.32 (s, 1 H), 7.35 (d, J = 6.8 Hz, 2 H), 7.57 (s, 1 H), 7.60 (d, J = 10.4
3
(
1
3
Hz, 2 H), 7.85 (d, J = 7.2 Hz, 1 H), 8.33 (d, J = 7.6 Hz, 1 H); C NMR (CDCl
7.3 (CH ), 41.1 (CH), 119.9 (Cq), 121.4 (CH), 123.7 (Cq), 124.3 (CH), 125.3 (CH), 126.8
CH), 126.9 (CH), 127.5 (2 X CH), 127.6 (CH), 127.7 (CH), 129.2 (2 X CH), 133.7 (Cq),
3
, 100 MHz): δ
3
2
(
140.7 (Cq), 146.8 (Cq), 167.5 (Cq).
30
6-Chloro-4-phenyl-3,4-dihydrobenzopyran-2-one (3l)
O
O
Cl
Ph
3
0
-1 1
A colourless solid (70% yield); mp 110 ⁰C; Lit 103-104 ⁰C; IR (KBr): νmax = 1770 cm ; H
3
NMR (CDCl , 400 MHz): δ 3.00-3.12 (m, 2 H), 4.33 (t, J = 6.8 Hz, 1 H), 6.96 (s, 1 H), 7.10
1
3
(
(
(
(
d, J = 8.8 Hz, 1 H), 7.17 (d, J = 7.6 Hz, 2 H), 7.30 (s, 1 H), 7.35-7.40 (m, 3 H); C NMR
CDCl , 100 MHz): δ 36.6 (CH ), 40.6 (CH), 118.5 (CH), 127.5 (2 X CH), 127.6 (Cq), 128.0
3
2
CH), 128.2 (CH), 128.9 (CH), 129.4 (2 X CH), 129.8 (Cq), 139.4 (Cq), 150.2 (Cq), 166.9
Cq).
3
1
4-Nitro-phenyl cinnamate (3m)
O
Ph
O
O N
2
18

ACCEPTED MANUSCRIPT
3
1
-
A colourless solid (20% yield); mp 142-144 ⁰C; Lit 142-146 ⁰C; IR( KBr): νmax = 1735 cm
1
1
;
H NMR (CDCl , 400 MHz): δ 6.56 (d, J = 16.0 Hz, 1 H), 7.31 (d, J = 8.8 Hz, 2 H), 7.37-
3
13
7
.39 (m, 3 H), 7.53-7.55 (m, 2 H), 7.85 (d, J = 16.0 Hz, 1 H), 8.24 (d, J = 8.8 Hz, 2 H); C
NMR (CDCl , 100 MHz): δ 115.1 (CH), 121.4 (2 X CH), 124.2 (2 X CH), 127.5 (2 X CH),
28.1 (2 X CH), 130.2 (CH), 132.7 (Cq), 144.2 (Cq), 147.0 (CH), 154.6 (Cq), 163.3 (Cq).
3
1
3
1
3-Nitro-phenyl cinnamate (3n)
O N
O
Ph
2
O
3
1
-
A colourless solid (30% yield); mp 106-108 ⁰C; Lit 108-110 ⁰C; IR( KBr): νmax = 1732 cm
1
1
;
3
H NMR (CDCl , 400 MHz): δ 6.64 (d, J = 16.0 Hz, 1 H), 7.45-7.47 (m, 3 H), 7.56-7.63
13
(
m, 4 H), 7.92 (d, J = 16.0 Hz, 1 H), 8.09 (t, J = 2.4 Hz, 1 H), 8.13-8.15 (m, 1 H); C NMR
CDCl , 100 MHz): δ 115.1 (CH), 116.4 (CH), 119.7 (CH), 126.7 (CH), 127.4 (2 X CH),
28.1 (2 X CH), 129.0 (CH), 130.1 (CH), 132.8 (Cq), 146.9 (CH), 147.8 (Cq), 150.1 (Cq),
(
3
1
1
63.7 (Cq).
32
4-Fluoro-phenyl cinnamate (3o)
O
Ph
O
F
3
2
-1
A colourless solid (50% yield); mp 70-75 ⁰C; Lit 73-74.5 ⁰C; IR( KBr): ν = 1735 cm ;
max
1
H NMR (CDCl
3
, 400 MHz): δ 6.64 (d, J = 15.6 Hz, 1 H), 7.12-7.15 (m, 4 H), 7.46 (s, 3 H),
13
7
.61 (s, 2 H), 7.89 (d, J = 16.0 Hz, 2 H); C NMR (CDCl , 100 MHz): δ 115.9 (CH), 116.2
3
(CH), 116.9 (CH), 123.0 (CH), 123.1 (CH), 128.4 (2 X CH), 129.1 (2 X CH), 130.8 (CH),
134.1 (Cq), 146.9 (CH), 159.0 (Cq), 161.5 (Cq), 165.4 (Cq).
7
-Hydroxy-4-phenyl-3,4-dihydro-2H-chromen-2-one and 5-hydroxy-4-phenyl-3,4-
33
dihydro-2H-chromen-2-one (3pa+3pb)
HO
O
O
O
O
+
Ph
OH Ph
1
A colourless solid (70% yield); 3pa (3pb) 5:1; H NMR (CDCl
3
, 400 MHz): δ 2.99-3.12 (m),
4.30 (4.65) (t), 6.60 (d), 6.71 (s), 6.84 (d), 7.17 (d), 7.29-7.38 (m).
19

ACCEPTED MANUSCRIPT
3
4
5,6-Benzo-4-(4-methoxyphenyl)-3,4-dihydrobenzopyran-2-one (3q)
(
4-OMe) H C6
O
4
O
34
-1
A colorless solid (85% yield); mp 128-130 ⁰C; Lit 130-131 ⁰C; IR (KBr): ν =1762 cm ;
max
1
3
H NMR (CDCl , 400 MHz): δ 3.04-3.16 (m, 2 H), 3.66 (s, 3 H), 4.85 (dd, J = 6.4, 2 Hz, 1
H), 6.72 (d, J = 6.4 Hz, 2 H), 6.97 (d, J = 6.4 Hz, 2 H), 7.27 (d, J = 9.2 Hz, 1 H), 7.37-7.43
1
3
(
m, 2 H), 7.72 (d, J = 8.0 Hz, 1 H), 7.79 (d, J = 9.2 Hz, 2 H) ; C NMR (CDCl
3
, 100 MHz): δ
3
1
1
6.8 (CH), 37.7 (CH ), 55.2 (OCH ), 114.6 (2 X CH), 117.6 (CH), 118.1 (Cq), 123.1 (CH),
2 3
25.3 (CH), 127.5 (CH), 128.1 (2 X CH), 128.8 (CH), 129.9 (CH), 131.0 (Cq), 131.1 (Cq),
32.6 (Cq), 149.7 (Cq), 158.9 (Cq), 167.4 (Cq).
28
6-Methyl-4-(4-methoxyphenyl)-3,4-dihydrobenzopyran-2-one (3r)
O
O
H C
3
C H ( 4-OMe)
6
4
28
-1 1
A colourless solid (78% yield); mp 115 ⁰C; Lit 120 ⁰C; IR (KBr): νmax = 1757 cm ; H
NMR (CDCl
3
, 400 MHz): δ 2.27 (s, 3 H), 2.95-3.07 (m, 2 H), 3.82 (s, 3 H), 4.27 (t, J = 6.8
Hz, 1 H), 6.79 (s, 1 H), 6.89 (d, J = 7.2 Hz, 2 H), 7.03 (d, J = 8.4 Hz, 1 H), 7.08-7.11 (m, 3
1
3
H); C NMR (CDCl
X CH), 116.8 (CH), 125.8 (Cq), 128.6 (2 X CH), 128.6 (CH), 129.2 (CH), 132.5 (Cq), 134.3
Cq), 149.6 (Cq), 158.9 (Cq), 168.1 (Cq).
3 3 2 3
, 100 MHz): δ 20.8 (CH ), 37.3 (CH ), 39.9 (CH), 55.3 (CH ), 114.5 (2
(
3
4
6,7-Methylenedioxy-4-(4-methoxyphenyl)-3,4-dihydrobenzopyran-2-one (3s)
O
O
O
O
C H (4-OMe)
6
4
20

ACCEPTED MANUSCRIPT
34
A colorless solid (68% yield); mp 136-138 ⁰C; Lit 136.5-137.5 ⁰C; IR (KBr): νmax = 1753
-1 1
cm ; H NMR (CDCl , 400 MHz): δ 2.83-2.97 (m, 2 H), 3.73 (s, 3 H), 4.11 (dd, J = 8.0, 6.0
3
Hz, 1 H), 5.88 (dd, J = 3.2, 1.6 Hz, 2 H), 6.32 (s, 1 H), 6.58 (s, 1 H), 6.79-6.82 (m, 2 H),
1
3
6
.98-7.01 (m, 2 H); C NMR (CDCl
3 2 3
, 100 MHz): δ 37.2 (CH ), 39.9 (CH), 55.3 (OCH ),
9
9.1 (CH), 101.7 (CH ), 107.3 (CH), 114.5 (2 X CH), 118.4 (Cq), 128.6 (2 X CH), 132.4
2
(Cq), 144.4 (Cq), 146.1 (Cq), 147.5 (Cq), 159.0 (Cq), 167.8 (Cq).
3
5
5,7-Dimethyl-4-(4-methoxyphenyl)-3,4-dihydrobenzopyran-2-one (3t)
O
O
C H (4-OMe)
6
4
35
-1
A colorless solid (82% yield); mp 166-168 ⁰C; Lit 166-168 ⁰C; IR (KBr): ν = 1766 cm ;
max
1
H NMR (CDCl
3
, 400 MHz): δ 2.08 (s, 3 H), 2.27 (s, 3 H), 2.89-2.99 (m, 2 H), 3.68 (s, 3 H),
4.26 (dd, J = 6.0, 2.4 Hz, 1 H), 6.72 (d, J = 8.0 Hz, 2 H), 6.76 (d, J = 3.2 Hz, 2 H), 6.88 (d, J
1
3
=
8.4, 2 H); C NMR (CDCl
), 114.4 (2 X CH), 115.4 (CH), 120.5 (Cq), 127.3 (CH), 128.0 (2 X CH), 132.3
Cq), 136.6 (Cq), 138.7 (Cq), 152.0 (Cq), 158.8 (Cq) 167.8 (Cq).
3 3 3 2
, 100 MHz): δ 18.7 (CH ), 21.1 (CH ), 37.2 (CH), 37.9 (CH ),
55.3 (OCH
3
(
36
7,8-Dimethyl-4-(4-methoxyphenyl)-3,4-dihydrobenzopyran-2-one (3u)
O
O
C H (4-OMe)
6
4
36
-1 1
A colorless solid (83% yield); mp 112-114 ⁰C; Lit 114 ⁰C IR (KBr): νmax = 1749 cm ; H
NMR (CDCl , 400 MHz): δ 2.19 (s, 3 H), 2.22 (s, 3 H), 2.86-2.97 (m, 2 H), 3.72 (s, 3 H),
.18 (t, J = 6.8 Hz, 1 H), 6.63 (d, J = 7.6 Hz, 1 H), 6.78-6.82 (m, 3 H), 6.99 (d, J = 8.8 Hz, 2
3
4
1
3
H); C NMR (CDCl
OCH ), 114.4 (2 X CH), 123.5 (Cq), 124.9 (CH), 124.9 (Cq), 125.6 (CH), 128.6 (2 X CH),
32.6 (Cq), 137.7 (Cq), 149.7 (Cq), 158.9 (Cq), 168.4 (Cq).
3 3 3 2
, 100 MHz): δ 11.9 (CH ), 19.9 (CH ), 37.2 (CH ), 39.9 (CH), 55.3
(
3
1
3
4
5,6-Benzo-4-(3,4-dimethoxyphenyl)-3,4-dihydrobenzopyran-2-one (3v)
(
3,4-di OMe) H C6
O
3
O
21

ACCEPTED MANUSCRIPT
34
-1
A colorless solid (80% yield); mp 152-154 ⁰C; Lit 156-159 ⁰C; IR (KBr): νmax =1757 cm ;
1
H NMR (CDCl , 400 MHz): 3.05-3.16 (m, 2 H), 3.72 (s, 6 H), 4.82-4.84 (m, 1 H), 6.50-6.53
3
(dd, J = 2.0 Hz, 1 H), 6.62-6.63 (m, 1 H), 6.65 (s, 1 H), 7.27 (d, J = 8.8 Hz, 1 H), 7.35-7.44
1
3
(
m, 2 H), 7.74 (d, J = 8.0 Hz, 1 H), 7.79 (d, J = 8.8 Hz, 2 H); C NMR (CDCl
7.3 (CH), 37.7 (CH ), 55.9 (CH ), 55.9 (CH ), 110.0 (CH), 111.6 (CH), 117.5 (CH), 117.9
Cq), 119.1 (CH), 123.1 (CH), 125.3 (CH), 127.5 (CH), 128.8 (CH), 129.9 (CH), 131.0 (Cq),
3
, 100 MHz): δ
3
2
3
3
(
131.1 (Cq), 133.0 (Cq), 148.4 (Cq), 149.5 (Cq), 149.7 (Cq), 167.4 (Cq).
3
7
6-Hydroxy-4-(3,4-dimethoxyphenyl)-3,4-dihydrobenzopyran-2-one (3w)
O
O
HO
C H (3,4-di OMe)
6
3
3
7
A colorless solid (72% yield); mp 164-166 ⁰C; Lit 168-170 ⁰C; IR (KBr): νmax = 3267, 1710
-1 1
cm ; H NMR (CDCl
3
, 400 MHz): δ 2.87-2.99 (m, 2 H), 3.77 (s, 3 H), 3.80 (s, 3 H), 4.15
(dd, J = 8.8, 6.0 Hz, 1 H), 4.86 (bs, 1 H), 6.35 (dd, J = 2.8, 0.4 Hz, 1 H), 6.60 (d, J = 2.0 Hz,
1
6
H), 6.64 (dd, J = 8.4, 2.0 Hz, 1 H), 6.68 (dd, J = 8.8, 2.8 Hz, 1 H), 6.77 (d, J = 8.0 Hz, 1 H),
13
.94 (d, J = 8.8 Hz, 1 H); C NMR (CDCl
), 110.6 (CH), 111.5 (CH), 114.6 (CH), 115.4 (CH), 117.9 (CH), 119.9 (CH), 127.3
Cq), 132.4 (Cq), 145.3 (Cq), 148.4 (Cq), 149.3 (Cq), 152.7 (Cq), 168.4 (Cq).
3 2
, 100 MHz): δ 37.0 (CH ), 40.4 (CH), 55.9 (2 X
OCH
3
(
3
8
5,7-Dimethyl-4-(3,4-dimethoxyphenyl)-3,4-dihydrobenzopyran-2-one (3x)
H C
O
O
3
CH3 C H (3,4-di OMe)
6
3
38
-1 1
A colorless solid (77% yield); mp 137-139 ⁰C; Lit 135 ⁰C; IR (KBr): νmax = 1764 cm ; H
NMR (CDCl , 400 MHz): δ 2.07 (s, 3 H), 2.25 (s, 3 H ), 2.92-2.94 (m, 2 H), 3.71 (s, 3 H),
3
3
6
.73 (s, 3 H), 4.22-4.25 (m, 1 H), 6.42-6.45 (dd, J = 2.0 Hz, 1 H), 6.52 (d, J = 2.0 Hz, 1 H),
13
3 3
.64 (d, J = 8.4 Hz, 1 H), 6.74 (s, 2 H); C NMR (CDCl , 100 MHz): δ 18.7 (CH ), 21.1
(CH ), 37.6 (CH), 37.9 (CH ), 55.9 (2 X CH ), 110.2 (CH), 111.5 (CH), 115.4 (CH), 119.0
3 2 3
(
CH), 120.3 (Cq), 127.3 (CH), 132.9 (Cq), 136.6 (Cq), 138.7 (Cq), 148.3 (Cq), 149.3 (Cq),
52.0 (Cq), 167.7 (Cq).
1
22

ACCEPTED MANUSCRIPT
3
8
7,8-Dimethyl-4-(3,4-dimethoxyphenyl)-3,4-dihydrobenzopyran-2-one (3y)
CH3
H C
O
O
3
C H (3,4-di OMe)
6
3
3
8
-1 1
A colorless solid (60% yield); mp 98-100 ⁰C; Lit 98-99 ⁰C; IR (KBr): νmax = 1766 cm ; H
NMR (CDCl , 300 MHz): δ 2.28 (s, 3 H), 2.30 (s, 3 H ), 2.98-3.02 (m, 2 H), 3.84 (s, 3 H),
.87 (s, 3 H), 4.22-4.24 (m, 1 H), 6.68-6.70 (m, 2 H ), 6.74 (s, 1 H), 6.82 (m, 1 H), 6.90 (d, J
3
3
13
=
7.8 Hz, 1 H); C NMR (CDCl
CH), 55.9 (2 X CH ), 110.7 (CH), 111.6 (CH), 119.8 (CH), 123.4 (Cq), 124.8 (CH), 124.9
Cq), 125.5 (CH), 133.1 (Cq), 137.7 (Cq), 148.4 (Cq), 149.4 (Cq), 149.7 (Cq), 168.2 (Cq).
3 3 3 2
, 75 MHz): δ 11.8 (CH ), 19.9 (CH ), 37.1 (CH ), 40.4
(
(
3
5,7-Dimethyl-4-(3,4,5-trimethoxyphenyl)-3,4-dihydrobenzopyran-2-one (3z)
H C
O
O
3
CH3 C H (3,4,5-tri OMe)
6
2
A mixture of 3.5-dimethyl phenol (0.69 mmol), 3,4,5-trimethoxycinnamic acid (0.69 mmol)
and iodine (0.13 mmol) was neat heated at 120-130 ⁰C under an air atmosphere for a period
of 2.3 hours. Following completion of the reaction as monitored by TLC, the reaction mixture
was cooled, diluted with ethyl acetate, washed with aqueous sodium thiosulphate solution and
dried over sodium sulphate. The solvent was removed under vacuum to provide the crude
product. Further purification was done by using 60-120 mesh silica gel column
chromatography (hexanes/ethyl acetate, 7.5:2.5) as an eluent to give 5,7-dimethyl-4-(3,4,5-
trimethoxyphenyl)-3,4-dihydrobenzopyran-2-one (3z) (709.0 mg, 63%) as a colourless solid;
-1 1
Rf (hexanes/ethyl acetate, 7:3) 0.47; mp 110-112 ⁰C; IR (KBr): νmax = 1774 cm ; H NMR
CDCl , 400 MHz): δ 2.10 (s, 3 H), 2.27 (s, 3 H), 2.94-2.96 (m, 2 H), 3.68 (s, 6 H), 3.72 (s, 3
H), 4.21-4.23 (m, 1 H), 6.16 (s, 2 H), 6.76 (s, 2 H); C NMR (CDCl
(
3
13
3
, 100 MHz): δ 18.8
(CH ), 21.1 (CH ), 37.9 (CH ), 38.3 (CH), 56.1 (2 X CH ), 60.8 (CH ), 103.9 (2 X CH),
3 3 2 3 3
115.4 (CH), 119.9 (Cq), 127.4 (CH), 136.2 (Cq), 136.7 (Cq), 137.2 (Cq), 138.9 (Cq), 152.0
+
(
Cq), 153.6 (2 X Cq), 167.7 (Cq); HRMS: m/z calcd for C H O Na [M+Na] : 365.1365;
2
0
22
5
found: 365.1362.
23

ACCEPTED MANUSCRIPT
Various chroman derivatives:
1
7d
3
,3-Dimethyl-2,3-dihydro-1H-benzo[f]chromene (5a)
CH
3
CH3
O
1
7d
A colourless solid (92% yield from 4a and 87% yield from 4b); mp 68-70 ⁰C, Lit 68-69
-1 1
⁰
C; IR (KBr): νmax = 2974, 1620, 1597, 1236 cm ; H NMR (CDCl
H), 1.95 (t, J = 6.8 Hz, 2 H), 3.03 (t, J = 6.8 Hz, 2 H), 7.02 (d, J = 8.8 Hz, 1 H), 7.32 (ddd, J
8.0, 7.6, 0.8 Hz, 1 H), 7.47 (ddd, J = 8.4, 6.8, 1.2 Hz, 1 H), 7.61 (d, J = 8.8 Hz, 1 H), 7.75
3
, 400 MHz): δ 1.38 (s, 6
=
13
(
d, J = 8.0 Hz, 1 H), 7.82 (d, J = 8.4 Hz, 1 H); C NMR (CDCl
3
, 100 MHz): δ 19.3 (CH
2
),
2
1
6.6 (2 X CH ), 32.7 (CH ), 74.0 (Cq), 112.4 (Cq), 119.8 (CH), 121.9 (CH), 122.9 (CH),
3 2
26.2 (CH), 127.7 (CH), 128.4 (CH), 128.7 (Cq), 133.1 (Cq), 151.3 (Cq).
2-Iodo-3,3-dimethyl-2,3-dihydro-1H-benzo[f]chromene (5a’)
I
O
A mixture of prenyl alcohol (1.16 mmol), β-naphthol (1.16 mmol) and iodine (1.16 mmol) in
chloroform (10 mL) was stirred for 1.3 hours at room temperature. Chloroform was then
directly washed with saturated solution of sodium thiosulphate followed by dilute sodium
hydroxide solution. Finally chloroform layer was washed with water, dried over sodium
sulphate and concentrated to furnish the crude product. This was then purified using 60-120
mesh silica gel column chromatography (hexanes/ethyl acetate, 9.8:0.2) to give 2-iodo-3,3-
dimethyl-2,3-dihydro-1H-benzo[f]chromene (5a’) (120.5 mg, 31%) as a colourless solid; Rf
-1
(
hexanes/ethyl acetate, 9.5:0.5) 0.56; mp 108-110 ⁰C; IR (KBr) 2974, 1622, 1597, 1236 cm .
1
3
H NMR (CDCl , 400 MHz) δ 1.45 (s, 3 H), 1.57 (s, 3 H), 3.55-3.75 (m, 2 H), 4.51 (dd, J =
9
7
.6, 6.0 Hz, 1 H), 6.96 (d, J = 9.2 Hz, 1 H), 7.29 (t, J = 7.2 Hz, 1 H), 7.43 (t, J = 7.2 Hz, 1 H),
1
3
.60 (d, J = 9.2 Hz, 1 H), 7.67 (d, J = 8.8 Hz, 1 H), 7.71 (d, J = 8.0 Hz, 1 H); C NMR
), 26.6 (CH ), 33.1 (CH ), 34.3 (CH), 76.1 (Cq), 111.5 (Cq),
(DMSO, 100 MHz) δ 24.3 (CH
3
3
2
24

ACCEPTED MANUSCRIPT
1
19.0 (CH), 121.9 (CH), 123.4 (CH), 126.6 (CH), 128.2 (2 X CH), 128.5 (Cq), 131.9 (Cq),
49.6 (Cq). Anal. Calcd. For C H IO: C, 53.3; H, 4.4 %; Found: C, 53.4; H, 4.5 %.
1
15
15
1
7d
6-Methyl-2,2-dimethyl-3,4-dihydro-2H-1-benzopyran (5b)
CH3
O
CH3
H C
3
-1
1
A colourless oil (48% yield); IR (neat): νmax = 2976, 1498, 1261, 1105 cm ; H NMR
CDCl , 400 MHz): δ 1.23 (s, 6 H), 1.69 (t, J = 6.8 Hz, 2 H), 2.16 (s, 3 H), 2.64 (t, J = 6.8 Hz,
H), 6.60 (d, J = 8.0 Hz, 1 H), 6.78 (s, 1 H), 6.80 (d, J = 8.4 Hz, 1 H); C NMR (CDCl
MHz): δ 19.4 (CH ), 21.4 (CH ), 25.8 (2 X CH ), 31.8 (CH ), 72.8 (Cq), 115.9 (CH), 119.5
(
3
13
2
3
, 100
3
2
3
2
(Cq), 126.9 (CH), 127.6 (Cq), 128.7 (CH), 150.6 (Cq).
39
6
,7-Dimethoxy-2,2-dimethyl-3,4-dihydro-2H-chromene (5c)
CH
3
MeO
O
CH
3
MeO
-1 1
A colourless oil (77% yield); IR (neat): νmax = 2974, 2933, 1620, 1514, 1122 cm ; H NMR
CDCl , 400 MHz): δ 1.24 (s, 6 H), 1.70 (t, J = 6.8 Hz, 2 H), 2.61 (t, J = 6.8 Hz, 2 H), 3.74 (s,
H), 6.30 (s, 1 H), 6.48 (s, 1 H); C NMR (CDCl
CH ), 32.9 (CH ), 55.8 (CH ), 56.4 (CH ), 73.9 (Cq), 101.2 (CH), 111.2 (Cq), 112.2 (CH),
(
3
1
3
6
3 2
, 100 MHz): δ 22.1 (CH ), 26.7 (2 X
3
2
3
3
142.6 (Cq), 147.6 (Cq), 148.3 (Cq).
1
6m
6
-Methoxy-2,2-dimethyl-3,4-dihydro-2H-1-benzopyran (5d)
CH
3
O
CH3
MeO
-1 1
A colourless oil (58% yield); IR (neat): νmax = 2972, 1492, 1247 cm ; H NMR (CDCl
3
, 400
MHz): δ 1.23 (s, 6 H), 1.69 (t, J = 6.8 Hz, 2 H), 2.66 (t, J = 6.8 Hz, 2 H), 3.65 (s, 3 H), 6.52
13
(
d, J = 2.4 Hz, 1 H), 6.60-6.64 (m, 2 H); C NMR (CDCl
3 2
, 100 MHz): δ 22.8 (CH ), 26.8 (2
X CH ), 32.8 (CH ), 55.7 (CH ), 73.8 (Cq), 113.4 (CH), 113.9 (CH), 117.8 (CH), 121.5 (Cq),
3
2
3
148.0 (Cq), 152.9 (Cq).
1
9d
7-Methoxy-2,2-dimethyl-3,4-dihydro-2H-1-benzopyran (5e)
25

ACCEPTED MANUSCRIPT
CH3
MeO
O
CH3
-1
1
A colourless oil (45% yield); IR (neat): νmax = 2974, 1620, 1504, 1151 cm ; H NMR
CDCl , 400 MHz): δ 1.25 (s, 6 H), 1.71 (t, J = 6.8 Hz, 2 H), 2.63 (t, J = 6.8 Hz, 2 H), 3.67 (s,
H), 6.28 (d, J = 2.4 Hz, 1 H), 6.36 (dd, J = 8.4, 2.4 Hz, 1 H), 6.87 (d, J = 8.4 Hz, 1 H); C
NMR (CDCl , 100 MHz): δ 21.8 (CH ), 26.9 (2 X CH ), 32.9 (CH ), 55.2 (CH ), 74.3 (Cq),
01.7 (CH), 106.9 (CH), 112.9 (Cq), 129.9 (CH), 154.7 (Cq), 159.1 (Cq).
(
3
13
3
3
2
3
2
3
1
16m
6
,6-Dimethyl-7,8-dihydro-6H-[1,3]dioxolo[4,5-g]chromene (5f)
CH
3
O
O
CH
3
O
-1
1
A colourless oil (58% yield); IR (neat): νmax = 2974, 1504, 1479, 1151 cm ; H NMR
CDCl , 400 MHz): δ 1.22 (s, 6 H), 1.67 (t, J = 6.8 Hz, 2 H), 2.59 (t, J = 6.8 Hz, 2 H), 5.77 (s,
H), 6.26 (s, 1 H), 6.42 (s, 1 H); C NMR (CDCl
CH ), 32.8 (CH ), 73.9 (Cq), 98.9 (CH), 100.7 (CH
46.4 (Cq), 148.4 (Cq).
(
3
1
3
2
2
3, 100 MHz): δ 22.6 (CH ), 26.6 (2 X
3
2
2
), 108.1 (CH), 112.2 (Cq), 140.9 (Cq),
1
17d
6-Methoxy-2,2-dimethyl-3,4-dihydro-2H-benzo[h]chromene (5g)
H C
3
CH3
O
OMe
1
7d
A colourless solid (60% yield); mp 74-75 ⁰C, Lit 77-78 ⁰C; IR (KBr): νmax = 2974, 1633,
-1 1
1
597, 1273 cm ; H NMR (CDCl , 400 MHz): δ 1.30 (s, 6 H), 1.79 (t, J = 6.8 Hz, 2 H), 2.73
3
(t, J = 6.8 Hz, 2 H), 3.82 (s, 3 H), 6.38 (s, 1 H), 7.33 (dt, J = 7.6, 1.6 Hz, 1 H); 7.37 (dt, J =
1
3
7
.2, 1.6 Hz, 1 H); 8.05 (dd, J = 8.4, 1.6 Hz, 1 H); 8.08 (dd, J = 8.8, 1.6 Hz, 1 H); C NMR
(CDCl , 100 MHz): δ 23.4 (CH ), 26.9 (2 X CH ), 33.1 (CH ), 55.8 (CH ), 73.9 (Cq), 105.4
3 2 3 2 3
(CH), 113.4 (Cq), 121.4 (CH), 121.7 (CH), 125.0 (CH), 125.3 (Cq), 125.7 (CH), 126.5 (Cq),
142.5 (Cq), 148.5 (Cq).
1
6g
7-Hydroxy-2,2-dimethyl-3,4-dihydro-2H-1-benzopyran (5h)
CH3
HO
O
CH3
26

ACCEPTED MANUSCRIPT
1
6g
A colourless solid (46% yield); mp 68-70 ⁰C, Lit 72-73 ⁰C; IR (KBr): νmax = 3383, 2974,
-1 1
1
593, 1149 cm ; H NMR (CDCl , 400 MHz): δ 1.24 (s, 6 H), 1.69 (t, J = 6.8 Hz, 2 H), 2.60
3
(t, J = 6.8 Hz, 2 H), 6.22 (s, 1 H), 6.28 (dd, J = 8.4, 2.0 Hz, 1 H), 6.81 (d, J = 8.4 Hz, 1 H);
1
3
3 2 3 2
C NMR (CDCl , 100 MHz): δ 20.7 (CH ), 25.8 (2 X CH ), 31.9 (CH ), 73.5 (Cq), 102.7
(CH), 106.5 (CH), 112.2 (Cq), 129.1 (CH), 153.5 (Cq), 153.8 (Cq).
1
6l
6-Hydroxy-2,2-dimethyl-3,4-dihydro-2H-1-benzopyran (5i)
CH3
O
CH3
HO
1
6l
A colourless solid (33% yield); mp 77-78 ⁰C, Lit 77-78 ⁰C; IR (KBr): νmax = 3379, 2974,
-1 1
1
502, 1195 cm ; H NMR (CDCl
3
, 400 MHz): δ 1.23 (s, 6 H), 1.69 (t, J = 6.8 Hz, 2 H), 2.63
(t, J = 6.8 Hz, 2 H), 6.48 (d, J = 2.8 Hz, 1 H), 6.52 (dd, J = 8.8, 2.8 Hz, 1 H), 6.57 (d, J = 8.4
13
Hz, 1 H); C NMR (CDCl
3 2 3 2
, 100 MHz): δ 21.6 (CH ), 25.7 (2 X CH ), 31.7 (CH ), 72.9 (Cq),
113.4 (CH), 114.4 (CH), 116.8 (CH), 120.8 (Cq), 146.8 (Cq), 147.5 (Cq).
16g,40
2,2-Dimethyl-3,4-dihydro-2H-chromene-5,7-diol (5j)
CH3
HO
O
CH3
HO
1
6g,40
A colourless solid (56% yield); mp 158-160 ⁰C, Lit
163-164 ⁰C; IR (KBr): νmax = 3375,
-
1 1
1
600, 1144, 1053 cm ; H NMR (CDCl
H), 2.39 (t, J = 6.4 Hz, 2 H), 5.81 (s, 2 H); C NMR (CDCl
2 X CH ), 32.2 (CH ), 74.4 (Cq), 94.7 (CH), 96.6 (CH), 100.9 (Cq), 154.6 (Cq), 155.0 (Cq),
55.5 (Cq).
3
, 400 MHz): δ 1.13 (s, 6 H), 1.56 (t, J = 6.4 Hz, 2
1
3
3 2
, 100 MHz): δ 16.4 (CH ), 26.6
(
3
2
1
1
7d
6
-Chloro-2,2-dimethyl-3,4-dihydro-2H-1-benzopyran (5k)
CH
3
O
CH3
Cl
-1
1
A colourless oil (20% yield); IR (neat): νmax = 2976, 1479, 1261, 1122 cm ; H NMR
CDCl , 400 MHz): δ 1.31 (s, 6 H), 1.77 (t, J = 6.8 Hz, 2 H), 2.73 (t, J = 6.8 Hz, 2 H), 6.70
(
3
27

ACCEPTED MANUSCRIPT
1
3
(
d, J = 9.2 Hz, 1 H), 7.02 (d, J = 9.6 Hz, 1 H), 7.03 (s, 1 H); C NMR (CDCl
3
, 100 MHz): δ
2
1
2.4 (CH ), 26.8 (2 X CH ), 32.4 (CH ), 74.5 (Cq), 118.6 (CH), 122.5 (Cq), 124.2 (Cq),
2
3
2
27.2 (CH), 128.9 (CH), 152.6 (Cq).
3-Methyl-3-(4,8,12-trimethyltridecyl)-2,3-dihydro-1H-benzo[f]chromene (5l)
CH3
CH3
3
O
CH3
A mixture of phytol (1.16 mmol), β-naphthol (4.65 mmol), and iodine (0.35 mmol) in
chloroform (10 mL) was subjected to reflux with stirring for 4 hours. It was then cooled to
room temperature. Chloroform was directly washed with saturated solution of sodium
thiosulphate followed by dilute sodium hydroxide solution. Finally chloroform layer was
washed with water, dried over sodium sulphate and concentrated to furnish the crude product.
This was then purified using 60-120 mesh silica gel column chromatography (hexanes/ethyl
acetate,
9.8:0.2)
to
give
3-methyl-3-(4,8,12-trimethyltridecyl)-2,3-dihydro-1H-
benzo[f]chromene (5l) (108.7 mg, 76%) as a pale yellow oil; Rf (hexanes/ethyl acetate,
-1 1
9
.5:0.5) 0.50; IR (neat): νmax = 2951, 1625, 1598, 1234 cm ; H NMR (CDCl
3
, 400 MHz): δ
0.80-0.87 (m, 12 H), 1.10-1.15 (m, 7 H), 1.24-1.67 (m, 14 H), 1.32 (s, 3 H), 1.89-1.99 (m, 2
H), 2.99 (t, J = 6.8 Hz, 2 H) 7.03 (d, J = 8.8 Hz, 1 H), 7.31 (t, J = 7.6 Hz, 1 H), 7.47 (t, J =
.6 Hz, 1 H), 7.60 (d, J = 8.8 Hz, 1 H), 7.74 (d, J = 8.0 Hz, 1 H), 7.81 (d, J = 8.4 Hz, 1 H);
7
1
3
C NMR (CDCl
2.8 (2 peak tops, CH
0.8-30.9 (2 peak tops, CH
9.4-39.6 (3 peak tops, CH
26.2 (CH), 127.7 (CH), 128.4 (CH), 128.7 (Cq), 133.1 (Cq), 151.4 (Cq); Anal. Calcd. For
3
, 100 MHz): δ 19.1 (CH
), 23.9 (CH ), 24.5 (CH
), 32.7-32.8 (4 peak tops, CH), 37.3-37.6 (6 peak tops, CH
), 76.1 (Cq), 112.6 (Cq), 119.9 (CH), 121.9 (CH), 122.9 (CH),
2
), 19.7-19.8 (3 peak tops, CH
3
), 21.2 (CH
), 28.0 (CH),
),
2
), 22.7-
2
3
3
1
3
3
2
), 24.8-24.9 (2 peak tops, CH
2
2
2
2
C
30
H
46O: C, 85.3; H, 10.9 %; Found: C, 85.6; H, 11.1 %; GCMS: m/z calcd for C30
H
46
O
+
[
M] : 422.68; found: 422.22.
4
1
3-Phenyl-2,3-dihydro-1H-benzo[f]chromene (5m)
Ph
O
28

ACCEPTED MANUSCRIPT
4
1
A colourless solid (60% yield); mp 84-86 ⁰C, Lit 86 ⁰C; IR (KBr): νmax = 3062, 2924, 1597,
-1 1
1
236 cm ; H NMR (CDCl , 400 MHz): δ 2.11-2.19 (m, 1 H), 2.28-2.33 (m, 1 H), 3.06-3.10
3
(m, 2 H), 5.04 (dd, J = 10.0, 2.0 Hz, 1 H), 7.07 (d, J = 8.8 Hz, 1 H), 7.23-7.43 (m, 7 H), 7.56
1
3
(
d, J = 8.8 Hz, 1 H), 7.69 (d, J = 8.0 Hz, 1 H), 7.73 (d, J = 8.8 Hz, 1 H); C NMR (CDCl
00 MHz): δ 21.8 (CH ), 29.7 (CH ), 77.5 (CH), 113.6 (Cq), 119.2 (CH), 121.9 (CH), 123.3
CH), 126.1 (2 X CH), 126.4 (CH), 127.8 (CH), 127.9 (CH), 128.5 (CH), 128.6 (2 X CH),
3
,
1
2
2
(
129.0 (Cq), 133.0 (Cq), 141.6 (Cq), 152.7 (Cq).
4
2,43
6,7-Dimethoxy-2,2-dimethyl-2H-chromene (5ca)
MeO
MeO
O
A colourless solid; (60% yield); mp 46-48 ⁰C; IR (KBr): νmax = 2974, 1500, 1458, 1278, 1195
-
1 1
cm ; H NMR (CDCl
0.0 Hz, 1 H), 6.17 (d, J = 10.0 Hz, 1 H), 6.34 (s, 1 H), 6.46 (s, 1 H); C NMR (CDCl
MHz): δ 26.6 (2 X CH ), 54.9 (OCH ), 55.5 (OCH ), 74.9 (Cq), 99.9 (CH), 108.7 (CH),
12.0 (Cq), 120.9 (CH), 127.2 (CH), 142.0 (Cq), 146.2 (Cq), 148.6 (Cq).
3
, 400 MHz): δ 1.34 (s, 6 H), 3.75 (s, 3 H), 3.76 (s, 3 H), 5.41 (d, J =
13
1
3
, 100
3
3
3
1
44,45
6-Methoxy-2,2-dimethyl-2H-benzo[h]chromene (5ga)
O
MeO
A colourless solid (52% yield); mp 63-64 ⁰C; IR (KBr): νmax = 2974, 2933, 1641, 1597, 1276
-
1 1
cm ; H NMR (CDCl
.33 (d, J = 9.6 Hz, 1 H), 6.44 (s, 1 H), 7.34-7.42 (m, 2 H), 8.08 (d, J = 8.4 Hz, 2 H); C
NMR (CDCl , 100 MHz): δ 27.6 (2 X CH ), 55.8 (OCH ), 76.2 (Cq), 102.5 (CH), 114.8
Cq), 121.7 (CH), 121.8 (CH), 123.0 (CH), 125.5 (CH), 125.9 (CH), 126.0 (Cq), 128.3 (Cq),
3
, 400 MHz): δ 1.42 (s, 6 H), 3.89 (s, 3 H), 5.58 (d, J = 9.6 Hz, 1 H),
1
3
6
3
3
3
(
129.9 (CH), 141.9 (Cq), 149.3 (Cq).
5. Acknowledgment
29