New synthetic route towards 2,2-dimethylchromene and synthesis of substituted 7-(dimethylpropargyl)chromene

Article abstract of DOI:10.1002/jhet.5570450340

(Chemical Equation Presented) Trifluoromethansufonic acid (TFA) was found a proper reagent for regioselectively ring closure of resorcinol to afford 7-hydroxy-2,2-dimethyl-2,3-dihydrochromen-4-one 3. The propargylation of 3 gave rise to 2,2-dimethyl-7-(2-methylbut-3-yn-2-yloxy)-2,3-dihydrochromen-4-one 4. Condensation of 4 with substituted phenyl or benzyl Grignard reagents afforded substituted phenyl or benzylidene chromenes 6a-d and 4-(substitutedbenzylidene)- 3,4-dihydro chromenes 8a-e, respectively.

Full text of DOI:10.1002/jhet.5570450340

May-Jun 2008
909
New Synthetic Route Towards 2,2-Dimethylchromene and
Synthesis of Substituted 7-(Dimethylpropargyl)chromene
Babak H. Alizadeha , Alireza Foroumadib, Abass Shafiee* b
a Iranian Research Institute of Plant Protection, Shahid Chamran Avenue, Yaman St. No.1;
PO.Box:1454,Tehran
b Department of Chemistry, Faculty of Pharmacy and Pharmaceutical Sciences Research Center, Tehran
University of Medical Sciences, Tehran,14174 Iran. ashafiee@ams.ac.ir
Received February 18, 2007
R
O
O
6 (a-d)
O
O
O
O
R2
OH
R3
R1
HO
DBU, (CF3CO)2O
CuCl2.H2O, CH3CN,
0 oC, 1h
O
3
4
O
O
8 (a-e)
Trifluoromethansufonic acid (TFA) was found a proper reagent for regioselectively ring closure of
resorcinol to afford 7-hydroxy-2,2-dimethyl-2,3-dihydrochromen-4-one 3. The propargylation of 3 gave
rise to 2,2-dimethyl-7-(2-methylbut-3-yn-2-yloxy)-2,3-dihydrochromen-4-one 4. Condensation of 4 with
substituted phenyl or benzyl Grignard reagents afforded substituted phenyl or benzylidene chromenes 6a-d
and 4-(substitutedbenzylidene)-3,4-dihydro chromenes 8a-e, respectively.
J. Heterocyclic Chem., 45, 909 (2008).
INTRODUCTION
R
2,2-Dimethyl-3-chromene ring as a common scaffold in
several novel synthetic and natural compounds has shown
considerable biological activities. Several compounds
with the 2,2-dimethyl-3-chromene moiety were tested and
their results showed that chromenes with an aromatic ring
substituted at the C-4 position may act as potent retinoic
acid receptor α-selective antagonists [1,2]. Moreover, the
chromene derivatives themselves have several biological
activities, and excellent results have been shown in a
decade of extensive research [3,4]. In addition,
benzopyranes are commonly found in many natural
products, in particular, the flavonoids and the glyasperins
(Figure 1). Furthermore, a recent study has shown that the
propargyl moiety present in chromone derivatives is
essential for biological activity [5,6,7]. The latter
hypothesis prompted us to investigate the possible
utilization of dimethylpropargyl moiety for the
preparation of 4-(substituted phenyl) chromenes 6a-d and
4-(substitutedbenzylidene)-3,4-dihydro chromenes 8a-e as
O
O
OMe
HO
O
O
6 (a-d)
OMe
Glyasperin
R2
R3
R1
8 (a-e)
O
O
Figure 1

910
B. H. Alizadeh , A. Foroumadi, A. Shafiee
Vol 45
possible biologically active compounds. Herein we report
the synthesis of (6a-d) and (8a-e).
yield of the propargylation of 3 depended on the reaction
temperature. Thus, the temperature of a solution of
compound 3 in acetonitrile was maintained at -5 °C for 45
minutes followed by carefully addition of resultant triflate
into the reaction mixture. Treatment of various substituted
phenyl Grignard reagents with 4, using the normal
reaction condition, afforded the required alcohol (5),
which after elimination of water afforded the
corresponding olefin (6a-d), in good yield.
RESULTS AND DISCUSSION
According to retrosynthetic analysis, the known
compound 3 is the key intermediate for the synthesis of
6a-d and 8a-e. A survey in the literature showed that most
procedures for the synthesis of compound 3 required
severe reaction conditions, lack of generality and they
were low yielding [3,8]. One important entry into this
structural type is through the treatment of resorcinol with
3,3-dimethylacrylic acid in the presence of a Lewis acid
For the preparation of compound 8, the Wittig reaction,
namely, reaction of substituted benzyl triphenylphos-
phonium with 4 was tried. However, compounds 8 could
Scheme 1
O
O
O
O
HOOC
i)POCl3, 60%
OH
+
HO
OH
ii)CF3SO3H, 80%
DBU, (CF3CO)2O
CuCl2.H2O, CHCN
0 oC, 1h
HO
O
3,3-dimethyl
acrylic acid
New reagent
resorsinol
4
3
2
1
R
R
6a: R=H
6b: R=Cl
6c: R=Me
6d: R=OMe
OH
HCl 1 N
80-90 oC, 3h
R-PhMgBr
Et2O, reflux
O
O
O
O
5
such as POCl3 or CF3COOH [9,10]. As Shown in Scheme
1, the key intermediate 3 was synthesized through the
reaction of resorcinol with 3,3-dimethylacrylic acid,
POCl3 and ZnCl2 and under the best condition gave 60%
yield of compound 3. Furthermore, the work up was
difficult, too sluggish, and basically, changing the
condition of the reaction had no appreciable effect on
increasing the yield. Observing this unsatisfactory result,
we turned our attention to develop an efficient, general,
and practical method. We observed that the reaction of
compound 2 with 3 equivalent of Lewis acid CF3SO3H at
70 °C gave smoothly compound 3 in good 80% overall
yield (Scheme 1).
not be isolated [12]. Finally the reaction of substituted
benzyl magnesium bromide with compound 4 in ether
under reflux afforded an unstable tertiary alcohols
7
which was converted to 8a-8e using a hot acidic condition
(Scheme 2) [13, 14]. Compounds 8a-8e was obtained as
90:10 to 60:40 mixtures of E and Z-isomers. The
structures of compounds were established by NMR. In E-
isomers H5 of E-chromen-4-one was more deshielded than
the Z-isomer. In fact in the Z-isomer the phenyl ring has
shielded the H5 of chromene-4-one.
CONCLUSION
In the next step, introduction of dimethyl propargyl into
3 was investigated. The latter group was shown to be
essential for biological activity [4,5,6]. Treatment of 2-
methylbut-3-yn-2-ol with trifluoroacetic anhydride gave
intermediate triflate which has been used as an effective
alkylating reagent in the presence of DBU and
CuCl2.2H2O in acetonitrile [11]. Different experimental
conditions were conducted and results showed that the
In conclusion, we have described an efficient, general,
and practical method for the preparation of 3 under mild
conditions, using trifluoromethansulfonic acid (TFA) as a
proper Lewis acid. Two types of the new 4-substituted
derivatives of 6a-d and 8a-e were prepared via the
reaction of several substituted phenyl and benzyl
magnesium halides with 4 as a versatile precursor for the
preparation of various derivatives of chromenes.

May-Jun 2008
Synthesis of substituted 7-(dimethylpropargyl)chromene
911
Scheme 2
(2.9 mL, 20.83 mmoles) was added over a 30 minutes period
while keeping the temperature at less than 0°C. The solution was
allowed to stir at 0°C for 1 hour before addition to 3.
To a solution of 3 (1 g, 5.2 mmoles) in CH3CN (10 mL) under
argon and cooled in an ice- salt bath (-5 °C) was added DBU
(1.1 mL, 7.8 mmoles) and CuCl2.2H2O (44 mg, 0.44 mmole) and
stirred for 30 minutes.
R1
R2
HO
R3
Rn-BnMgBr
Et2O, reflux
O
O
4
8
This solution, maintained at -5 °C, was added to the 2-methyl-
3-butyn-2-triflate solution over a 50 minutes period while keeping
the temperature below 0°C. After stirring for 30 minutes at 0°C,
water was added and the mixture was concentrated at reduced
pressure and residue was extracted by EtOAc (3×50 ml). The
combined organic phase was washed with 1N HCl (3×50 ml),
saturated NaHCO3, and brine. After drying with Na2SO4, the
solvent was removed at reduced pressure to give a residue, which
was purified by column chromatography (silicagel, 30g) and
eluted by hexane/ethyl acetate (4:1) to provide the compound 4
(1.09 g, 4.2 mmoles, 81%) as pale yellow oil and also starting
compound 3 (0.1 g, 0.5 mmole, 10%). 1H nmr (deuterio-
chloroform): δ 1.48 (s, 3H, 2-CH3), 1.49 (s, 3H, CH3), 1.73 (s, 3H,
CH3), 1.74 (s, 3H, CH3), 2.70 (s, 3H, -CH2-C=O, CH≡C), 6.79
(dd, 1H, J = 2.3, 8.7 Hz, H-6), 6.8 (d, 1H J = 2.1 Hz, H-8), 7.76
(d, 1H, J =8.7 Hz, H-5); ir (Nujol): 3290 (≡C-H), 2132 (C≡C),
1655 (C=O) cm-1; ms: m/z (%) 258 (M+, 19), 192 (33), 177 (100),
137 (54), 107 (32), 67 (53). Anal. Calcd. for C16H18O3: C, 74.39;
H, 7.02. Found: C, 74.12; H, 6.93.
7
Wittig
HCl 1 N
80-90 oC, 3h
R2
R3
R1
O
O
8a: R1=R2=R3=H
8b: R1=R2=H, R3=Cl
8c: R1=R3=H, R2=Cl
8d: R3=H, R1=R2=Cl
8e: R2=R3=H, R1=Cl
2,2-Dimethyl-7-(2-methylbut-3-yn-2-yloxy)-4-phenyl-2H-
chromene (6a). To a stirred solution of 4 (0.1 g, 0.4 mmole), in
dry ether (3 mL) was added phenylmagnesium bromide (1.25
mL, 1 mmole) under argon. The resulting mixture was stirred
and reflux for 18 hours. After cooling, the organic phase was
washed with 1 N HCl (3×5 mL). The solvent was evaporated
under reduce pressure to give an oil. To this oily residue was
added 2 N HCl (5 mL) and refluxed for 12 hours, after cooling,
it was extracted with ethyl acetate (3×10 mL), The organic layer
was washed with saturated aqueous NaHCO3 and dried with
anhydrous Na2SO4. After concentration, the residue was purified
by flash column chromatography (silica gel = 10 g, hexane /
EtOAc= 5) to give 6a (1.25 g, 4.99 mmoles, 90 %) as colorless
EXPERIMENTAL
1
General: H nmr spectra were measured using a Bruker 500
spectrometer and chemical shifts are expressed as δ (ppm) with
tetramethylsilane as internal standard. The ir spectra were
obtained on a Shimadzu 470 spectrophotometer (potassium
bromide disks). The purity of the compounds was monitored by
thin layer chromatography. Elemental analyses were carried out
on CHN rapid elemental analyzer (GmbH-Germany) for C and
H, and the results are within ±0.4% of the theoretical values. All
substrates and reagents were obtained from Merck and Aldrich
Chemical Co.
1
oil. H nmr (deuteriochloroform): δ 1.54 (s, 6H, CH3), 1.69 (s,
6H, CH3), 2.62 (s, 1H, CH≡C), 5.55 (s, 1H, H-3), 6.71-6.73
(dd, 1H, J = 2.47, 8.46 Hz, H-6), 6.85 (d, 1H, J = 2.38 Hz, H-8),
6.93 (d, 1H, J = 8.46 Hz, H-5), 7.38-7.42 (m, 5H, aromatic); ir
(Nujol): 3290 (≡C-H), 2158 (C≡C), 1608 (C=C) cm-1; ms:
m/z (%) 318 (M+, 23), 251 (10), 237 (100), 208 (20), 165 (21),
119 (15), 91 (20). Anal. Calcd. for C22H22O2: C, 82.99; H, 6.96.
Found: C, 82.68; H, 6.91.
7-Hydroxy-2,2-dimethyl-2,3-dihydrochromen-4-one (3). To
a stirred mixture of resorcinol (2.0 g, 18.2 mmoles) and 3,3-
dimethylacrylic acid (1.8 g, 18.2 mmoles) was added trifluoro-
methanesulfonic acid (5.5 mL, 54.6 mmoles) in one portion. The
solution was warmed to 70 °C for 2 hours, cooled to room
temperature over 15 min, and poured into chloroform (40 mL).
The solution was slowly poured into water (50 mL), and the
layers were separated. The aqueous layer was extracted with
CH2Cl2 (3 x 20 mL). The combined organic layers were washed
with brine, dried over Na2SO4, and filtered. Concentration in
vacuum gave 2.7 g (14.6 mmoles, 80% yield) of an orange solid
[9]. mp 164-165°C; 1H nmr (deuteriochloroform): δ 1.43 (s, 6H,
2-CH3), 2.61 (s, 2H, -CH2-C=O), 6.29 (d, 1H, J = 2.1 Hz, H-8),
6.45 (dd, 1H, J = 2.1, 8.5 Hz, H-6), 7.61 (d, 1H, J = 8.5 Hz, H-
5); ir (Nujol): 3200 (OH), 1655 (C=O) cm-1; ms: m/z (%) 193
(39), 178 (100), 132 (11), 102 (39), 78 (24). Anal. Calcd. for
C11H12O3: C,68.74; H,6.29. Found: C, 68.98; H, 6.13.
4-(4-Chlorophenyl)-2,2-dimethyl-7-(2-methylbut-3-yn-2-
yloxy)-2H-chromene (6b). A colorless oil (85%), 1H nmr
(deuteriochloroform): δ 1.51 (s, 6H, CH3), 1.71 (s, 6H, CH3),
2.63 (s, 1H, CH≡C), 5.54 (s, 1H, H-3), 6.72-6.74 (dd, 1H, J =
2.47, 8.43 Hz, H-6), 6.85 (d, 1H, J = 2.41 Hz, H-8), 6.89 (d, 1H,
J = 8.46 Hz, H-5), 7.32 (d, 2H, J = 8.41 Hz, aromatic), 7.39-7.40
(d, 2H, J = 8.41 Hz, CH of CH2); ir (Nujol): 3296 (≡C-H),
2158 (C≡C), 1604 (C=C) cm-1; ms: m/z (%) 353 (M+, 24), 352
(71), 337 (60), 286 (38), 284 (51), 271 (100), 242 (37), 222 (43),
188 (60), 152 (87), 133 (39), 91 (42). Anal. Calcd. for
C22H21ClO2: C, 74.89; H, 6.00. Found: C, 74.91; H, 5.73.
2,2-Dimethyl-7-(2-methylbut-3-yn-2-yloxy)-4-p-tolyl-2H-
chromene (6c). A colorless oil (65%), 1H nmr (deutério-
chloroform): δ 1.51 (s, 6H, CH3), 1.70 (s, 6H, CH3), 2.43 (s, 3H,
Ph-CH3), 2.62 (s, 1H, CH≡C), 5.53 (s, 1H, H-3), 6.70-6.72
2,2-Dimethyl-7-(2-methylbut-3-yn-2-yloxy)-2,3-dihydro
chromen-4-one (4). To a solution of 2-methyl-3-butyn-2-ol
(2 mL, 20.83 mmoles) in anhydrous acetonitrile (10 ml) under
argon and cooled in an ice-salt bath at −5 °C, was added DBU
(4.7 mL, 31.25 mmoles) dropwise. Trifluoroacatic anhydride

912
B. H. Alizadeh , A. Foroumadi, A. Shafiee
Vol 45
(dd, 1H, J = 2.42, J = 8.45 Hz, H-6), 6.85 (d, 1H, J = 2.41 Hz,
H-8), 6.94-6.96 (d, 1H, J= 8.57 Hz, H-5), 7.23 (d, 2H, J = 7.9
Hz, aromatic), 7.28-7.29 (d, 2H, J = 7.9 Hz, aromatic); ir
(Nujol): 3283 (≡C-H), 2105 (C≡C), 1622 (C=C) cm-1; ms:
m/z (%) 332 (M+, 25), 258 (23), 250 (100), 243 (25), 176 (99),
137 (26), 91 (23), 83 (32). Anal. Calcd. for C23H24O2: C, 83.10;
H, 7.28. Found: C, 83.03; H, 7.44.
4-(4-Methoxyphenyl)-2,2-dimethyl-7-(2-methylbut-3-yn-2-
yloxy)-2H-chromene (6d). A colorless oil (70%), 1H nmr
(deuteriochloroform): δ 1.52 (s, 6H, CH3), 1.70 (s, 6H, CH3), 2.62
(s, 1H, CH≡C), 3.89 (s, 3H, -OCH3), 5.51 (s, 1H, H-3), 6.72 (dd,
1H, J= 2.4, 8.50 Hz, H-6), 6.83 (d, 1H, J= 6.5 Hz, Ph), 6.85 (d,
1H, J= 2.4 Hz, H-8), 6.95 (d, 1H, J= 8.41 Hz, H-5), 6.97 (d, 1H,
J= 8.5 Hz, Ph), 7.33 (d, 1H, J= 6.5 Hz, Ph), 7.43 (d, 1H, J= 8.5
Hz, Ph); ir (Nujol): 3288 (≡C-H), 2117 (C≡C), 1611 (C=C)
cm-1; ms: m/z (%) 348 (M+, 22) , 333 (34), 265 (100), 233 (22),
214 (76), 151 (62), 148 (72), 135 (44), 90 (72). Anal. Calcd. for
C23H24O3: C, 79.28; H, 6.94. Found: C, 78.98; H, 6.72.
4-Benzylidene-2,2-dimethyl-7-(2-methylbut-3-yn-2-yloxy)-
3,4-dihydro-2H-chromene (8a). A colorless oil (85%), as E and
Z mixture (90:10): 1H nmr (deuteriochloroform): δ 1.30 and 1.32
(2s, 3H, 2−CH3), 1.44 and 1.45 (2s, 3H, 2−CH3), 1.66 and 1.67
(2s, 3H, C≡CCH3), 1.70 and 1.71 (2s, 3H, C≡CCH3), 1.78 and
1.80 (2d, 2H, J = 2.8 Hz, 3-CH2), 2.75 (bs, 1H, CH≡C), 6.69 and
6.71 (2d, 1H, J = 2.4 Hz, H8), 6.75 and 6.79 (2dd, 1H, J = 2.4 Hz,
8.4 Hz, H6), 7.10 (bs, 1H, Ph_CH=C), 7.22 - 7.36 (m, 5H, Ph),
7.39 and 7.59 (2d, 1H, J = 8.4 Hz, H5); ir (Nujol): 3290 (≡C-H),
2128 (C≡C), 1606 (C=C) cm-1. ms: m/z (%) 322 (M+, 91), 280
(13), 242 (12), 202 (22), 188 (100), 150 (94), 84 (24). Anal. Calcd.
for C23H24O2: C, 83.10; H, 7.28. Found: C, 83.31; H, 7.01.
4-(2,3-Dichlorobenzylidene)-2,2-dimethyl-7-(2-methylbut-
3-yn-2-yloxy)-3,4-dihydro-2H-chromene (8d). A colorless oil
(80%).as E and Z mixture (95:5): 1H nmr (deuteriochloro-
form): δ 1.31 and 1.32 (2s, 3H, 2-CH3), 1.44 and 1.45 (2s, 3H, 2-
CH3), 1.67 and 1.68 (2s, 3H, C≡C_CH3), 1.71 and1.72 (2s, 3H,
_
C≡ C CH3), 1.77 (2d, 2H, J = 2.9 Hz, 3-CH2), 2.57 (2s, 1H,
CH≡), 6.78 and 6.80 (2d, 1H, J = 2.4 Hz, H8), 6.74 and 6.83
(2dd, 1H, J = 2.4 Hz, 8.4 Hz, H6), 7.06 (bs, 1H, 2,3-di-
ClPh_CH=C), 7.15 and 7.30 (m, 3H, 2,3-di-ClPh), 7.39 and 7.60
(2d, 1H, J = 8.4 Hz, H5). IR (KBr) cm-1: 3380 (≡C-H). 2128
(C≡C), MS m/z (%): 403 (M++3, 15), 402 (M++2, 65), 401
(M++1, 24), 400 (M+, 95), 384 (69), 319 (98), 255 (21), 251 (17),
177 (20), 175 (70), 158 (100), 134 (52), 91 (47). Anal. Calcd for
C23H22Cl2O2: C, 68.83; H, 5.53. Found: C, 68.53; H, 5.85.
4-(2-Chlorobenzylidene)-2,2-dimethyl-7-(2-methylbut-3-yn-
2-yloxy)-3,4-dihydro-2H-chromene (8e). A colorless oil (85%)
as E and Z mixture (65:35): 1H nmr (deuteriochloro-form): δ
1.32 and 1.33 (2s, 3H, 2−CH3), 1.43 and 1.44 (2s, 3H, 2−CH3),
1.67 and 1.68 (2s, 3H, C≡C_CH3), 1.71 and 1.72 (2s, 3H,
C≡C_CH3), 1.77 and 1.78 (2d, 2H, J = 3.0 Hz, 3−CH2), 2.61 and
2.62 (2s, 1H, CH≡C), 6.72 and 6.77 (2d, 1H, J = 2.4 Hz, H8), 6.78
and 6.84 (2dd, 1H, J = 2.4 Hz, 8.4 Hz, H6), 7.10 (bs, 1H, 2-
ClPh_CH=C), 6.21 and 7.30 (m, 4H, 2-ClPh), 7.45 and 7.59 (2d,
1H, J = 8.4 Hz, H5). IR (KBr) cm-1: 3300 (≡C-H). 2132 (C≡C),
MS m/z (%): 368 (M++2, 3), 366 (M+, 10), 350 (10), 300 (45), 285
(100), 221 (11), 175 (16), 125 (18). Anal. Calcd for C23H23ClO2:
C, 75.30; H, 6.32. Found: C, 75.35; H, 6.52.
Acknowledgement. This research was supported by a grant
from Iran National Science Foundation (No. 83181) awarded to
Dr. B.H. Alizadeh Special thanks to Dr. M. Amini and Kh. Abdi
for their helps in measuring Mass and IR spectra.
4-(4-Chlorobenzylidene)-2,2-dimethyl-7-(2-methylbut-3-
yn-2-yloxy)-3,4-dihydro-2H-chromene (8b). A colorless oil
1
(90%) as E and Z mixture (67:33): H nmr (deuteriochloroform):
REFERENCES
δ 1.31 and 1.32 (2s, 3H, 2−CH3), 1.44 and 1.45 (2s, 3H, 2−CH3),
1.65 and 1.67 (2s, 3H, C≡CCCH3), 1.69 and 1.71 (2s, 3H,
C≡CCCH3), 1.77 and 1.79 (2d, 2H, J = 2.8 Hz, 3-CH2), 2.70 and
2.71 (2s, 1H, CH≡C), 6.68 and 6.75 (2d, 1H, J = 2.4 Hz, , H8),
6.76 and 6.78 (2dd, 1H, J = 2.4 Hz, 8.4 Hz, H6), 7.04 (bs, 1H, 4-
ClPh_CH=C), 7.21 and 7.26 (2d, 2H, J = 8.4 Hz, H3,5-4-ClPh),
7.31 and 7.37 (2d, 2H, J = 8.4 Hz , H2,6-4-ClPh), 7.36 and 7.54
(2d, 1H, J = 8.4 Hz, H5). IR (film) cm-1: 3288 (≡C-H). 2130
(C≡C), MS m/z (%): 368 (M++2, 32), 366 (M+, 100), 351 (59),
302 (48) 284 (98), 250 (26), 189 (20), 175 (57), 124 (99), 89 (78),
67 (87). Anal. Calcd for C23H23ClO2: C, 75.30; H, 6.32. Found: C,
75.53; H, 6.45.
4-(3-Chlorobenzylidene)-2,2-dimethyl-7-(2-methylbut-
3-yn-2-yloxy)-3,4-dihydro-2H-chromene(8c). A colorless oil
(85%) as E and Z mixture (60:40): 1H nmr (deuteriochloro-
form): δ 1.32 and 1.33 (2s, 3H, 2−CH3), 1.45 and 1.46 (2s, 3H,
2−CH3), 1.66 and 1.67 (2s, 3H, C≡CCCH3), 1.70 and 1.71 (2s, 3H,
C≡CCCH3), 1.78 and 1.79 (2d, 2H, J = 2.9 Hz, 3-CH2), 2.72 and
2.73 (2s, 1H, -C≡CH), 6.69 and 6.77 (2d, 1H, J = 2.4 Hz, H8), 6.77
and 6.82 (2dd, 1H, J = 2.4 Hz, 8.4 Hz, H6), 7.07 (bs, 1H,
3-ClPh_CH=C), 7.15 and 7.30 (m, 4H, 3-ClPh), 7.35 and 7.51 (2d,
1H, J = 8.4 Hz, H5). IR (film) cm-1: 3290 (≡C-H). 2128 (C≡C),
MS: m/z (%): 368 (M++2, 12), 364 (M+, 37), 350 (14), 301 (37), 298
(73), 283 (100), 132 (14), 124 (22), 90 (13), 66 (24). Anal. Calcd
for C23H23ClO2: C, 75.30; H, 6.32. Found: C, 75.55; H, 6.14.
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