K. Ghosh, R. Karmakar, D. Mal
FULL PAPER
1
3
201–202 °C. H NMR (400 MHz, CDCl
3
, 25 °C): δ = 8.50 (d, JH,H
112.4, 111.9, 61.5, 9.6 ppm. HRMS (ESI): calcd. for C20
+ H]+ 321.1128; found 321.1132.
16 4
H O [M
3
3
=
8.4 Hz, 1 H), 7.97 (d,
J
H,H = 8.8 Hz, 1 H), 7.86 (d,
J
H,H
=
3
3
9
1
1
2
1
.2 Hz, 1 H), 7.57 (t, JH,H = 7.2 Hz, 1 H), 7.48 (d, JH,H = 7.2 Hz,
3
4-Ethyl-isobenzofuran-1,3-dione (16b): This compound was pre-
pared from 2-ethyl furan (18b) in two steps. The mixture of 18b
1.07 g, 11.2 mmol) and maleic anhydride (1 g, 10.2 mmol) with a
H), 7.44 (s, 1 H), 3.13 (q, JH,H = 7.6 Hz, 2 H), 2.41 (s, 3 H),
3
13
3
.40 (t, JH,H = 7.6 Hz, 3 H) ppm. C NMR (100 MHz, CDCl ,
5 °C): δ = 159.0, 150.1, 141.4, 140.9, 132.8, 127.6, 127.4, 124.1,
21.1, 120.8, 120.7, 116.9, 110.6, 108.2, 26.4, 15.4, 8.9 ppm. HRMS
(
catalytic amount of hydroquinone in dry Et O (30 mL) was stirred
2
+
for overnight. Then, the reaction mixture was evaporated to give
the known oxo-bridged Diels–Alder adduct 17b. Without further
purification, this adduct (350 mg, 1.8 mmol) was added in small
fractions to concentrated H SO (40 mL) at 0 °C with 3 h of vigor-
2 4
ous stirring. The reaction mixture was then poured onto crushed
ice, and the resulting grey precipitate was filtered and dried under
(ESI): calcd. for C18
H
14
O
3
[M + H] 279.1022; found 279.1028.
From 33a: This compound was also synthesized in 60% yield from
3a (40 mg, 0.1 mmol), NMP (0.01 mL, 0.1 mmol), and Fe(acac)
3
3
through a coupling reaction that followed the same procedure as
described above for neo-tanshinlactone. In this case, EtMgBr (1 m
solution in THF, 0.12 mL, 0.15 mmol) was used in the same ratio
as above.
vacuum to give 16b (305 mg, 52%) as a grey powder; m.p. 135–
1
1
37 °C. H NMR (400 MHz, CDCl
H), 3.14 (q, JH,H = 7.6 Hz, 2 H), 1.33 (t, JH,H = 5.4 Hz, 3 H) ppm.
3
, 25 °C): δ = 7.87–7.68 (m, 3
3
3
Methyl
17-Methyl-12-oxo-12H-11,15-dioxacyclopenta[a]phen-
anthrene-6-carboxylate (15a): Phthalide 13a and furylacrylate 9a af-
forded 14a as well as coproduct 15a (27 mg, 12%) as a white solid;
m.p. 180–182 °C. IR (KBr): ν˜ = 761, 1110, 1235, 1609, 1741, 3467,
HRMS (ESI): calcd. for C10
177.0549.
H
8
O
3
[M + H]+ 177.0552; found
–
1
1
1-Oxo-1,3-dihydroisobenzofuran-4-yl
Trifluoromethanesulfonate
3
3
770 cm . H NMR (400 MHz, CDCl , 25 °C): δ = 8.64 (s, 1 H),
3
3
(19a): To a stirred solution of 19b (500 mg, 3.33 mmol) in dry
DCM under nitrogen was added 2,6-lutidine (0.3 mL, 3.33 mmol)
followed by triflic anhydride (0.55 mL, 3.33 mmol) at 0 °C to room
8
.41 (d, JH,H = 7.6 Hz, 1 H), 8.20 (d, JH,H = 8 Hz, 1 H), 7.86 (t,
3
3
J
H,H = 7.6 Hz, 1 H), 7.59 (t, JH,H = 7.6 Hz, 1 H), 7.53 (s, 1 H),
.05 (s, 3 H), 2.57 (s, 3 H) ppm. 1 C NMR (100 MHz, CDCl
3
4
2
1
3
,
2
temp. After 3 h, the usual workup with DCM, H O, and brine gave
5 °C): δ = 163.2, 158.9, 158.9, 149.6, 141.4, 134.4, 128.3, 128.2,
27.5, 124.9, 123.6, 122.8, 120.6, 117.3, 110.6, 108.6, 52.3, 8.9 ppm.
compound 19a (112 mg, 60%) as a white solid, which was used
without further purification; m.p. 70–72 °C. IR (KBr): ν˜ = 628,
+
HRMS (ESI): calcd. for C18
09.0770.
H
12
O
5
[M + H] 309.0764; found
–
1
1
7
(
60, 806, 944, 1059, 1136, 1214, 1424, 1762 cm . H NMR
3
3
6
400 MHz, [D ]DMSO, 25 °C): δ = 8.00 (d, JH,H = 7.6 Hz, 1 H),
3
3
Methyl 4,17-Dimethyl-12-oxo-12H-11,15-dioxacyclopenta[a]phen-
anthrene-6-carboxylate (15b): Phthalide 8a and furylacrylate 9a af-
forded 1 as well as coproduct 15b (36 mg, 17%) as a white solid;
m.p. 188–200 °C. IR (KBr): ν˜ = 1122, 1233, 1592, 1735, 3472, 362,
7.92 (d, JH,H = 8 Hz, 1 H), 7.80 (t, JH,H = 8 Hz, 1 H), 5.54 (s, 2
1
3
H) ppm. C NMR (100 MHz, [D
143.5, 139.1, 132.6, 129.2, 127.5, 126.3, 120.1, 67.7 ppm. HRMS
(ESI): calcd. for C
S [M + H]+ 283.9889; found 283.9893.
6
]DMSO, 25 °C): δ = 169.2,
9
5 3 5
H F O
–
1 1
7
8
7
3
52 cm . H NMR (400 MHz, CDCl , 25 °C): δ = 9.03 (s, 1 H),
3
3
Methyl 15,17-Dimethyl-12-oxo-12,15-dihydro-11-oxa-15-azacyclo-
penta[a]phenanthrene-6-carboxylate (23): The reaction of 24a
195 mg, 0.82 mmol) and 13a (100 mg, 0.75 mmol) in the presence
of LiHMDS (2.4 mL, 2.4 mmol) in dry THF (10 mL) at –78 °C
was carried out by following the general annulation procedure. Af-
ter the usual workup with ethyl acetate and H O, purification by
2
column chromatography gave 23 (92 mg, 32%) as yellowish solid;
m.p. 172–174 °C. IR (KBr): ν˜ = 773, 1058, 1187, 1248, 1617, 1711,
.41 (d, JH,H = 8 Hz, 1 H), 7.71 (d, JH,H = 7.2 Hz, 1 H), 7.55–
1
3
.50 (m, 2 H), 4.06 (s, 3 H), 3.01 (s, 3 H), 2.60 (s, 3 H) ppm.
, 25 °C): δ = 164.3, 159.7, 159.6, 150.3,
42.8, 139.5, 134.7, 129.4, 128.3, 128.1, 127.6, 126.9, 124.6, 124.2,
C
(
NMR (100 MHz, CDCl
3
1
1
C
16.2, 109.6, 52.5, 14.1, 9.8 ppm. HRMS (ESI): calcd. for
[M + H]+ 323.0920; found 323.0923.
19
H
14
O
5
Methyl
4-Ethyl-17-methyl-12-oxo-12H-11,15-dioxacyclopenta[a]-
–
1 1
phenanthrene-6-carboxylate (15c): The annulation between 13b and
1733, 2369 cm . H NMR (400 MHz, CDCl
3
, 25 °C): δ = 8.41 (d,
3
3
9a afforded 4-ethyl-neo-tanshinlactone (14b) as well as coproduct
JH,H = 8 Hz, 1 H), 8.33 (s, 1 H), 8.15 (d, JH,H = 8 Hz, 1 H), 7.32
1
3
3
1
5c (31 mg, 15%) as a white solid; m.p. 184–186 °C. H NMR (t, JH,H = 7.2 Hz, 1 H), 7.52 (t, JH,H = 7.6 Hz, 1 H), 6.84 (s, 1
3
13
(
1
400 MHz, CDCl
3
, 25 °C): δ = 8.94 (s, 1 H), 8.40 (d, JH,H = 7.6 Hz, H), 4.01 (s, 3 H), 3.86 (s, 3 H), 2.65 (s, 3 H) ppm. C NMR
H), 7.80 (d, JH,H = 7.2 Hz, 1 H), 7.64–7.59 (m, 2 H), 4.06 (s, 3 (100 MHz, CDCl , 25 °C): δ = 167.0, 161.1, 149.2, 135.9, 134.8,
130.6, 130.5, 127.4, 121.4, 120.2, 119.8, 113.3, 112.0, 107.7, 52.3,
3
3
3
3
H), 3.32 (q, JH,H = 7.6 Hz, 2 H), 2.59 (s, 3 H), 1.53 (t, JH,H
=
7
1
1
.6 Hz, 3 H) ppm. 13C NMR (100 MHz, CDCl
60.2, 155.3, 149.3, 142.9, 141.1, 138.7, 134.5, 133.6, 129.7, 129.3,
28.5, 121.7, 122.2, 116.5, 113.3, 111.4, 52.7, 15.1, 10.1 ppm.
, 25 °C): δ = 165.3, 37.8, 11.8 ppm. HRMS (ESI): calcd. for C19H15NO [M + H]
3 4
+
322.1080; found 322.1090.
+
Methyl
carboxylate (24a): To a stirred solution of 25a (150 mg, 0.66 mmol)
in dry DMF (15 mL) were added sequentially K CO (92 mg,
2-(1-Methoxycarbonylvinyl)-1,4-dimethyl-1H-pyrrole-3-
HRMS (ESI): calcd. for C20
37.1073.
H
16
O
5
[M + H] 337.1077; found
3
2
3
Ethyl 1-Methyl-11-oxo-10,11-dihydrophenanthro[1,2-b]furan-5-carb-
oxylate (15d): Following the general annulation procedure, the con-
densation of phthalide 13a (100 mg, 0.74 mmol) with ethyl furyl-
acrylate 9b (224 mg, 0.9 mmol) in dry THF (5 mL) gave 15d
0.66 mmol), CaO (37 mg, 0.66 mmol), and paraformaldehyde
(60 mg, 2 mmol), and the resulting mixture was heated at 75 °C for
8 h. The usual workup with ethyl acetate, H O, and brine solution
2
furnished compound 24a (100 mg, 63%) as light yellow oil, which
(
1
107 mg, 45%) as a white solid; m.p. 182–184 °C. IR (KBr): ν˜ =
was used without further purification. Upon refrigeration, the com-
–1
1
108, 1249, 1606, 1735, 3469, 3772 cm . H NMR (400 MHz, pound changed from an oil to white crystals, and the crystal struc-
3
CDCl
8
3
, 25 °C): δ = 8.52 (s, 1 H), 8.35 (d, JH,H = 8.0 Hz, 1 H),
ture was confirmed by XRD analysis, m.p. 60–62 °C. IR (KBr): ν˜
3
3
–1 1
.10 (d, JH,H = 8.0 Hz, 1 H), 7.82 (t, JH,H = 7.6 Hz, 1 H), 7.55 = 772, 1084, 1169, 1206, 1245, 1300, 1438, 1700 cm . H NMR
3
3
(t, JH,H = 7.6 Hz, 1 H), 7.49 (s, 1 H), 4.50 (q, JH,H = 7.2 Hz, 2
(400 MHz, CDCl
3
, 25 °C): δ = 6.65 (s, 1 H), 6.41 (s, 1 H), 5.70 (s,
3
13
H), 2.52 (s, 3 H), 1.49 (t,
JH,H = 7.2 Hz, 3 H) ppm. C NMR 1 H), 3.75 (s, 3 H), 3.70 (s, 3 H), 3.46 (s, 3 H), 2.23 (s, 3 H) ppm.
1
3
(100 MHz, CDCl
3
, 25 °C): δ = 164.1, 160.2, 155.3, 149.1, 142.9,
C NMR (100 MHz, CDCl
3
, 25 °C): δ = 166.9, 165.7, 133.9, 133.5,
135.1, 134.8, 130.6, 128.5, 128.3, 122.1, 121.9, 120.1, 119.1, 115.9,
130.4, 122.1, 121.3, 113.5, 52.5, 50.7, 34.3, 12.2 ppm. HRMS (ESI):
4044
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Eur. J. Org. Chem. 2013, 4037–4046