4. ExperimentalThe general
experimental is described in [27].
Benz(f)inden-1-One 5c This compound was prepared from 14a.
Mp:
80–85°C; yellow; yield 93%; IR (cm−1): 1684; H1 NMR
(200 MHz), 8.20 (d, 1H, J = 8.1),
7.97 (d, 1H, J = 8.1), 7.57–7.41 (m,
3H), 6.01–5.88 (m, 1H), 5.23–5.12 (m, 2H),
4.28 (s, 3H), 4.02 (s, 3H), 3.11–3.07 (m, 2H); C13 NMR
(50 MHz): 193.99, 152.2, 144.6, 141.5, 139.8, 134.5, 132.9, 131.1, 129.4,
127.1, 126.2, 125.7, 123.0, 117.1, 115.5, 62.8, 62.7, 29.5; MS (m/z): 280 (M+,
100%), 265, 250, 223, 178, 165.
Benz(f)inden-1-One 5d This compound was prepared as a yellow oil in 90% yield from 14b. IR (cm−1): 1689; H1 NMR (300 MHz): 8.10 (d, 1H, J = 8.1), 7.97 (d,
1H, J = 8.1), 7.60–7.40 (m, 3H), 4.85
(d, 2H, J = 10.8), 4.28 (s, 3H), 4.02 (s, 3H), 3.04 (s, 2H),
1.79 (s, 3H); C13 NMR (75 MHz): 192.9, 152.0, 144.5, 142.6, 140.9,
140.4, 132.7, 131.0, 129.3, 127.0, 126.0, 125.6, 122.9, 115.3, 112.5, 62.9,
62.7, 33.3, 22.5; MS (m/z): 294 (M+, 100%), 279, 263, 236, 165, 152, 139.
Benzo(b)fluorenone 6: Method A To a stirred
solution of the nitro compound 7a (100 mg, 0.33 mmol), and methacrolein
(60 mg, 0.86 mmol) in benzene (5 mL) at 0°C was added DBU (10 mg,
0.066 mmol). Stirring was continued for 24 hours at rt. The reaction mixture was diluted with
diethyl ether (50 mL), washed with saturated sodium bicarbonate solution (10 mL) and then with brine (10 mL). The organic phase was dried (Na2SO4)
and concentrated. The resulting residue was purified by preparative TLC to give
a yellow crystalline solid of 6 (26 mg, 25%).
Method B To a stirred solution of aldehyde 11 (50 mg, 0.154 mmol) in
dichloromethane (6 mL) was added SnCl4⋅5H2O (5 mg) under nitrogen atmosphere. The stirring was
continued for 30 hours. After usual work up of the reaction mixture, the
residue was purified by preparative TLC to provide 6 (21 mg, 45%). Mp:
150-151°C; IR (cm−1): 1695; H1 NMR (200 MHz):
8.29 (d, 1H, J = 7.4), 8.04 (d, 1H, J = 7.4), 7.88 (d, 1H, J = 7.7), 7.65–7.36 (m, 4H), 4.28 (s,
3H), 4.00 (s, 3H), 2.42 (s, 3H); C13 NMR (50 MHz): 190.4,
153.7, 146.4, 140.0, 138.8, 136.4, 135.4, 133.6, 130.8, 129.4, 127.8, 126.7,
125.5, 124.4, 124.1, 122.4, 119.9, 63.1, 61.1, 21.3; MS (m/z): 304 (M+, 100%),
289, 218, 189, 149, 57.
Compound 7aThis was
prepared from benzindenone 5a and nitromethane in 89% yield according to the procedure described
earlier [25]. Mp: 124°C; IR (cm−1): 1711; H1
NMR (200 MHz): 8.37 (s, 1H, ArH) 8.03 (d, 1H, J = 8.1), 7.89–7.87 (m, 2H), 7.68–7.54 (m, 2H), 4.91–4.82 (ABq,
1H, J = 12.8, 5.8), 4.64–4.53 (ABq,
1H, J = 12.8, 5.8), 4.42–4.34 (m,
1H), 3.21–3.07 (ABq, 1H, J = 19.2,
8.2), 2.74–2.63 (ABq, 1H, J = 19.2, 3.9).
Compound 7bThis was prepared from 5b,
following the procedure described for compound 7a. Mp: 179-180°C; white solid; yield: 89%;
IR (cm−1): 1715; H1 NMR (200 MHz): 8.40 (d, 1H, J = 8.2), 8.10 (d, 1H, J = 8.5), 7.74–7.55 (m, 2H), 5.34–5.29
(m, 1H), 4.43–4.38 (m, 2H), 4.18 (s, 3H), 4.03 (s, 3H) 3.17–3.04 (m, 1H),
2.76–2.65 (m, 1H); C13 NMR (50 MHz):
200.4, 152.9, 148.6, 134.1, 132.7, 129.7, 126.9, 125.3, 122.7, 121.8, 77.8,
77.2, 63.4, 61.8, 42.3, 34.4; MS (m/z): 301 (M+), 254, 239, 197, 141, 115.
Compound 8To a mixture of enone 5b (0.178 g,
0.740 mmol) and 1,1-ethanediyldioxy-2-methyl-4-nitrobutane 9 (0.389 g, 2.22 mmol) in CH2Cl2 (4 mL) was added DBU (12 mg, 0.078 mmol)
and the mixture was stirred at rt for 6 hours. It was then
concentrated and purified by column chromatography to
afford 10 as an oil (0.2 g, 65%). H1
NMR spectrum revealed the presence of two isomers as indicated by three signals
δ 4.15, 4.08, and 4.05, corresponding to the methoxy groups. The peak at δ 4.15
was not resolved.
The methine hydrogens of CHNO2 appeared at δ 5.19. To a stirred
solution of above nitro acetal 10 (100 mg, 0.24 mmol) in THF (8 mL) was
added 10% HCl (1 mL) solution. Stirring was continued for 20 hours. After usual
work up of the reaction mixture, the
residue was chromatographed to
afford 6 (18 mg, 25%) and 8 (2.5 mg, 3%).
Compound 9 Yield:
50%; colorless oil; IR (cm−1):
1541; H1 NMR (200 MHz): 4.66 (d, 1H, J = 4), 4.46 (t, 2H, J = 6), 3.98–3.79 (m, 4H), 2.30–1.77
(m, 3H), 1.00 (d, 3H, J = 6.7); C13 NMR (50 MHz): 106.8, 74.1, 65.1, 65.0, 34.3, 29.0, 14.7.
Compound 11This was
prepared from compound 15b by Nef reaction [25]. Yield: 50%; purity > 80%; H1
NMR (500 MHz): 9.94 (s, 1H), 8.40 (d, 1H, J = 8.4), 8.10 (d, 1H, J = 8.4), 7.69
(t, 1H, J = 8.2), 7.52 (t, 1H, J = 8.2), 4.87 (s, 1H), 4.78 (s, 2H),
4.21 (s, 3H), 4.16 (brs, 1H), 4.02 (s, 3H) 3.31–3.27 (m, 1H); 2.78–2.75 (ABq,
1H, J = 14.0, 4.3) 1.75 (s, 3H).
Compound 12H1 NMR (200 MHz): 8.37
(d, 1H, J = 8.0, 1H), 8.05 (d, 1H, J = 8.0, 1H), 7.68–7.51 (m, 2H), 6.85
(brs, 1 H), 4.80–4.60 (m, 1H), 4.32 (s, 3H), 3.70 (s, 3H), 2.85 (brs, 1H),
2.22–2.15 (m, 1H), 1.5-1.4 (m, 2H), 1.25–1.21 (m, 3H).
Compound 14aThis
was prepared as thick brownish oil in 88% yield from pentacycle 12, following an earlier method [24]. IR (cm−1): 1705; H1
NMR (300 MHz): 8.33 (d, 1H, J = 8.7),
8.06 (d, 1H, J = 8.4), 7.61 (m, 1H),
7.49 (m, 1H), 6.05–6.02 (m, 1H), 5.65–5.50 (m, 2H), 5.07 (d, 1H, J = 16.8), 4.85 (d, 1H, J = 10.2), 4.08 (s, 3H), 4.03 (s, 3H),
3.78 (d, 1H, J = 4.2), 3.45 (brs,
1H), 2.89–2.91 (m, 2H), 2.45–2.38 (m, 1H), 2.0 (ABd, 1H, J = 8.7), 1.80 (ABd, 1H, J = 8.7); C13 NMR (75 MHz): 207.1, 151.2, 147.6, 138.0, 135.2, 135.1, 134.3, 132.4,
128.9, 126.6, 125.8, 125.0, 121.8, 117.5, 63.0, 62.4, 62.1, 50.8, 50.9, 47.0,
46.6, 41.6.
Compound 14bThis was prepared from pentacycle 12, following the
procedure adopted for compound 14a. Yield: 89%; thick
oil; IR (cm−1): 1705; H1
NMR (400 MHz): 8.32 (d, 1H, J = 8.1),
8.07 (d, 1H, J = 8.1), 7.62 (br t,
1H), 7.49 (br t, 1H), 6.00 (dd, 1H, J = 2.8, 5.6), 5.49 (dd, 1H, J = 2.8,
5.6), 4.70 (brs, 1H), 4.66 (brs, 1H), 4.08 (s, 3H), 4.03 (s, 3H), 3.93 (d, 1H, J = 4), 3.44 (brs, 1H), 3.05 (ABd, 1H, J = 13.8), 2.94 (brs, 1H), 2.41 (ABd,
1H, J = 13.8), 1.98 (ABd, 1H, J = 8.8), 1.79 (ABd, 1H, J = 8.8), 1.46 (s, 3H); C13
NMR (50 MHz): 207.4, 151.0, 147.6, 143.1, 138.3, 135.5, 135.3, 134.6, 132.3,
128.8, 126.7, 125.8, 125.0, 121.8, 114.3, 62.8, 61.8, 61.6, 52.5, 50.8, 46.8,
46.1, 45.7, 23.8.
Compound 15aThis
was prepared from 5c,
following the procedure described for compound 7a. Mp:
98-99°C; white solid; yield:
92%; IR (cm−1): 1712; H1 NMR (300 MHz): 8.40 (d, 1H, J = 8.7), 8.10 (d,
1H, J = 8.4), 7.72–7.66 (m, 1H), 7.58
(m, 1H), 5.75–5.61 (m, 1H), 5.23–5.04 (m, 3H), 4.54–4.47 (m, 1H), 4.20 (s, 3H), 4.10 4.05 (m, 1H), 4.01 (s,
3H), 2.83–2.78 (m, 1H); 2.65–2.51 (m, 2H); C13 NMR
(75 MHz): 202.7, 153.1, 148.7, 133.8, 133.3, 133.0, 129.8, 127.0, 125.4, 122.3,
121.9, 118.8, 77.7, 77.3, 63.4, 61.8, 52.2, 39.4, 36.1; MS (m/z): 341 (M+),
307, 290, 280 (100%), 265, 165.
Compound 15bThis
was prepared from 5d,
following the procedure adopted for compound 7a. Mp: 122-123°C; white solid; yield: 90%; IR
(cm−1): 1707; H1 NMR (300 MHz): 8.41 (d, 1H, J = 8.4), 8.10 (d, 1H, J = 8.4), 7.72–7.60 (m, 1H), 7.61–7.55
(m, 1H), 5.07 (dd, 1H, J = 12.8,
4.2), 4.88 (s, 1H), 4.76 (s, 1H), 4.59 (dd, 1H, J = 12.8, 8.7), 4.20 (s, 3H), 4.15–3.90 (m, 1H), 4.00 (s, 3H),
2.95–2.88 (m, 1H); 2.63 (dd, 1H, J = 13.8, 5.1), 2.34 (dd, 1H, J =
13.8, 9.0), 1.73 (s, 3H); C13 NMR (75 MHz):
202.8, 153.3, 148.8, 142.5, 133.3, 132.9, 129.9, 129.8, 126.9, 125.3, 122.0,
114.2, 77.8, 63.3, 61.9, 50.8, 40.5, 39.9, 21.9. MS (m/z): 355 (M+), 319, 304, 294 (100%), 279, 265, 253, 236,
223, 165, 152, 139; anal.
calcd for C20H21NO5: C, 67.59; H, 5.96; N,
3.94, found C, 67.51; H, 5.93; N, 3.93.