ˇ
42
Z. Stiplosˇek, M. Sindler-Kulyk, K. Jakopcˇic´, A.Visˇnjevac and B. Kojic´-Prodic´
Vol. 39
gave tarry material (106 mg, 22%). After repeated column chro-
matography and recrystallization from ethylacetate/methanol the
dimer 4a (51 mg, 23%) was obtained. Some minor quantities of
unidentified dimeric products (19 mg, 8.6%) were also obtained.
173.7 (s), 165.8 (s), 148.4 (s), 137.8 (s), 137.1 (d), 134.1 (s),
129.4 (d) and 126.9 (d) for C-2 of two pyrone rings, 114.2 (d,
pyrone C-3), 56.3 (q, OCH ), 45.4 (d) and 43.6 (d) for cyclobu-
3
tane carbons, 21.1 (q, CH ); ms: m/z (relative intensity) 485
3
+
+
(MH , 34), 484 (9), 242 (M /2, 100), 196 (38), 159 (8), 128 (7),
105 (6).
2-Methoxy-1H-naphtho[2,1-b]pyran-1-one (6a).
Colourless crystals of this compound (29 mg, 4%) melted at
Irradiation of 2-[2-(4-Methoxyphenyl)ethenyl]-5-methoxy-4H-
pyran-4-one (2c).
mp 212-214°; uv: (λ /nm) 310, 282, 250, 230; ir: 3350 (w),
max
2990 (w), 1645 (vs), 1639, vs, 1590 (s), 1570 (s), 1450 (s), 1370
(s), 1310 (s), 1250 (s), 1240 (s), 1190 (s), 1075 (s) 1000 (s), 950
A solution of 2c (500 mg, 1.94 mmoles) in 300 ml methanol
after irradiation (13 hours) and evaporation of the solvent was
fractionated by column chromatography on silica gel into several
fractions as follows: a small quantity (10 mg, 2%) of unidentified
1
(s), 880 (s), 820 (s), 760 (s), 715 (s); H nmr (deuteriochloroform):
δ 9.95 (d, 1H, J = 8.52 Hz, H-10), 8.39 (s, 1H, H-3), 8.27 (d, 1H,
J = 9.06 Hz, H-5), 8.08 (d, 1H, J = 8.01 Hz, H-7), 7.78 (dd, 1H,
J = 8.52, 7.08 Hz, H-9), 7.69 (d, 1H, J = 9.06 Hz, H-6), 7.68 (dd,
material (uv: λ
220, 260, 345 nm) followed by the mixture of
max
13
1H, J = 8.01, 7.08 Hz, H-8) 3.78 (s, 3H, OCH ); C nmr (deuteri-
starting compound (131 mg, 26%) and the mixture of dimers (231
mg, 46%). The last fractions eluted with methanol were some
tarry material (46 mg, 9.2%). After second column chromatogra-
phy of the dimeric mixture and recrystallization from ethylacetate/
methanol, a dimer 4c (116 mg, 50%) was isolated and the rest was
a mixture of other unidentified dimers (39 mg, 8%).
3
ochloroform): δ 173.4 (s, C-1), 156.4 (s, C-4a), 146.2 (s, C-2),
138.1 (d, C-3), 135.6 (d, C-6), 130.1 (s) and 129.9 (s) for C-6a and
C-10a, 129.2 (d), 128.7 (d), 126.6 (d), 126.0 (d) for C-7, C-8, C-9
and C-10, 118.2 (d, C-5), 115.9 (s, C-10b), 56.8 (q, OCH ).
3
Anal. Calcd for C
H O (226.23): C, 74.33; H, 4.46. Found:
14 10 3
Anal. Calcd. for dimeric mixture C
H O (516.54): C, 69.76;
C, 74.48; H, 4.52.
30 28 8
H, 5.46. Found; C, 69.57; H, 5.31.
r-1,t-3-Di(5-methoxy-4-pyron-2-yl)-c-2,t-4-diphenylcyclobutane
[r-ctt htt dimer] [25] (4a).
r-1,t-3-Di(5-methoxy-4-pyron-2-yl)-c-2,t-4-di(4-methoxy-
phenyl)cyclobutane [r-ctt htt dimer] [25](4c).
The colourless crystals of 4a (51 mg, 23%) melted at mp 217-
-1
1
218°; uv: (λ /nm) 266; ir: 1645 cm (ν
); H nmr (deuterio-
This compound (116 mg, 50%), colourless crystals, melted at
max
C=O
chloroform): δ 7.63 (s, 2H, pyrone H-6), 7.09-7.38 (m, 10H, Ar-
mp 178-179°; uv: (λ /nm) 266; ir: 3050 (w), 2900 (w), 2800
max
H), 6.26 (s, 2H, pyrone H-3), 4.38 (m, 2H) and 4.28 (m, 2H) for
(w), 1640 (vs), 1630 (s), 1580 (s), 1500 (s), 1450 (s), 1410 (s),
1260 (vs), 1220 (vs), 1170 (s), 1020 (s), 1000 (s), 980 (w), 920
(w), 820 (s), 800 (s); H nmr (deuteriochloroform): δ 7.32 (s, 2H,
a
b
cyclobutane H and H respectively; 3.63 (s, 6H, OCH ); ms: m/z
3
+
1
(relative intensity) 279 (18), 249 (43), 235 (100), 227 (M /2, 93),
197 (15), 183 (14), 169 (18), 155 (18), 141 (19), 127 (26), 113
(32), 99 (33), 85 (40), 71 (28), 57 (20).
pyrone H-6), 7.11 (d, 4H, J = 8.42 Hz), 6,81 (d, 4H, J = 8.42 Hz),
a
6.23 (s, 2H, pyrone H-3), 4.33 (m, 2H, H ), 4.17 (dd, 2H, J =
b
8.65, 8.56 Hz, H ), 3.77 (s, 6H, aryl OCH ), 3.54 (s, 6H, pyrone
Anal. Calcd for C
H O (456.49): C, 73.67; H, 5.29. Found:
3
28 24 6
13
OCH ); C nmr (deuteriochloroform): δ 173.5 (s), 165.7 (s),
C, 73.49; H, 5.14.
3
158.6 (s), 148.2 (s), 137.2 (d), 128.9 (s), 128.0 (d), 114.0 (d), 56.3
Irradiation of 2-[2-(4-Methylphenyl)ethenyl]-5-methoxy-4H-
pyran-4-one (2b).
(q, pyrone OCH ), 55.1 (q, aryl OCH ), 45.6 (d), 43.1 (d); ms:
3
3
+
+
m/z (relative intensity) 516 (M , 1), 259 (M /2, 100), 154 (51),
136 (36), 121 (16), 91(22).
After 9 hours of irradiation of 2b (500 mg, 2.06 mmoles) in
300ml methanol and evaporation of the reaction mixture (a yel-
low-red oil) was eluted with petroleum ether/acetone on a column
of silica gel to give several different fractions. The first fractions
were small quantities of unidentified product (9 mg, 1.8%), the
middle fractions were the mixture of unreacted starting compound
2b (265 mg, 53%) and the later fractions the mixture of dimeric
products (185 mg, 37%). Tarry material remained on the column.
By repeated column chromatography (ethylacetate/petroleum
ether 5:1) from the mixture of dimeric isomers only one dimer
was isolated in a greater extent (4b, 91 mg, 49%).
Irradiation of 2-[2-(4-Chlorophenyl)ethenyl]-5-methoxy-4H-
pyran-4-one (2d).
After 15 hours of irradiation of 2d (700 mg, 2.66 mmoles) in
300 ml methanol, and column chromatography on silica gel by
elution with ether/acetone 10:1, the photodehydrocyclization
product 6d (57 mg, 8%) and two dimers 4d and 5d (216 mg,
31%) were obtained. The starting material 2d (298 mg, 42.5%)
was also recovered. The tarry material (108 mg, 15.43%) was
obtained by elution with methanol. The preparative thin layer
chromatography using chloroform/petroleum ether 9:1 gives
pure isomers 4d and 5d beside the minor quantity of some
unidentified dimers.
Anal. Calcd. for dimeric mixture C
H O (484.54): C, 74.37;
30 28 6
H, 5.82. Found: C, 74.56, H, 5.97.
r-1,t-3-Di(5-methoxy-4-pyron-2-yl)-c-2,t-4-di(4-methylphenyl)-
cyclobutane [r-ctt htt dimer] [25] (4b).
Anal. Calcd. for the mixture of dimeric products C
H Cl O
28 22 2 6
(525.38): C, 64.01; H, 4.22; Cl, 13.50. Found: C, 63.81; H, 4.02;
Cl, 13.35.
Colourless crystals of this compound (91 mg, 49%) melted at
mp 215-216°; uv: (λ /nm) 265; ir: 3090 (w), 2900 (w), 1640
max
9-Chloro-2-methoxy-1H-naphtho[2,1-b]pyran-1-one (6d).
Colourless crystals of 6d (21 mg, 3%) melted at mp 167-169°;
(vs), 1610 (vs), 1585 (vs), 1510 (s), 1440 (s), 1410 (s), 1380 (s),
1240 (vs), 1230 (vs), 1189 (vs), 1150 (s), 1000 (vs), 950 (s), 870
-1
1
1
uv: (λ /nm) 310, 250, 220; ir: 1645 cm (ν
); H nmr: δ
(s), 800 (vs); H nmr (deuteriochloroform): δ 7.99 (s, 2H, pyrone
max
C=O
10.01 (d, 1H, J = 2.19 Hz), 8.43 (s, 1H), 8.32 (d, 1H, J = 9.06
Hz), 8.14 (d, 1H, J = 8.57 Hz), 7.75 (d, 1H, J = 9.06 Hz), 7.73 (d,
H-6), 7.39 (d, 4H, J = 8.49 Hz,), 7.24 (d, 4H, J = 8.49 Hz), 6.37
(s, 2H, pyrone H-3), 4.51 (m, 2H), 4.47 (m, 2H), 3.64 (s, 6H,
13
13
1H, J = 8.57, 2.19 Hz), 3.79 (s, 3H, OCH ); C nmr: δ 173.8 (s),
OCH ), 2.35 (s, 6H, CH ); C nmr (deuteriochloroform): δ
3
3
3