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4H), 2.8–3.1 (m, 4H), 3.2 (m, 4H), 3.85 (s, 3H), 4.1 (t, 2H),
5.6 (m, 1H), 6.5–8.0 (m, 12H, Ar).
42.3), 402 (84.9), 388 (100). 4k: d 1.82 (m, 4H), 2.61 (m,
4H), 2.90 (m, 2H), 3.08 (d, 1H), 3.24 (d, 1H), 3.84 (s, 3H),
4.02 (m, 2H), 5.78 (s, 1H), 6.3–7.7 (m, 10H, Ar). MS: m/z
(rel. abundance): 455 (M+, 3.6), 98 (14.9), 84 (100). 4l: d
1.82 (m, 4H), 2.61 (m, 4H), 2.90 (m, 2H), 3.08 (d, 1H), 3.24
(d, 1H), 3.78 (s, 3H), 3.84 (s, 3H), 4.02 (m, 2H), 5.78 (s, 1H),
6.3–7.7 (m, 10H, Ar). MS: m/z (rel. abundance): 485 (M+,
10.44), 388 (3.2), 98 (45.55), 84 (100). 4m: d 1.9 (m, 2H),
2.2 (m, 4H), 2.75 (m, 2H), 2.85–3.1 (m, 6H), 3.8 (s, 3H), 4.0
(t, 2H), 5.8 (s, 1H), 6.3–7.5 (m, 11H, Ar). 4n: d 1.9 (m, 2H),
2.2 (m, 4H), 2.75 (m, 2H), 2.85–3.1 (m, 6H), 3.7 (s, 3H), 3.8
(s, 3H), 4.0 (t, 2H), 5.8 (s, 1H), 6.3–7.5 (m, 10H, Ar). MS:
m/z (rel. abundance): 499 (M+, 14.94), 418 (25.2), 406 (100).
4o: d 1.85 (m, 8H), 2.2 (m, 2H), 2.8 (m, 4H), 3.15 (m, 2H),
3.8 (s, 3H), 4.0 (t, 2H), 5.75 (s, 1H), 6.3–7.5 (m, 11H, Ar).
MS: m/z (rel. abundance): 483 (M+, 100), 357 (27.2), 291
(62.08). 4p: d 1.85 (m, 8H), 2.2 (m, 2H), 2.8 (m, 4H), 3.25
(m, 2H), 3.7 (s, 3H), 3.8 (s, 3H), 4.0 (t, 2H), 5.75 (s, 1H),
6.3–7.5 (m, 10H, Ar). MS: m/z (rel. abundance): 513 (M+,
44.6), 388 (100), 347 (31.28). 4q: d 1.85 (m, 8H), 2.15 (m,
2H), 2.7 (m, 4H), 3.15 (m, 4H), 3.8 (s, 3H), 3.9 (t, 2H), 5.75
(s, 1H), 6.3–7.5 (m, 11H, Ar). MS: m/z (rel. abundance): 497
(M+, 65.16), 376 (23.12), 357 (100). 4r: d 1.85 (m, 8H), 2.15
(m, 2H), 2.7 (m, 4H), 3.15 (m, 4H), 3.7 (s, 3H), 3.8 (s, 3H),
3.9 (t, 2H), 5.75 (s, 1H), 6.3–7.5 (m, 10H, Ar). MS: m/z (rel.
abundance): 527 (M+, 12.26), 387 (20.48), 211 (100). 4s: d
2.55 (m, 4H), 2.8 (m, 2H), 3.08 (d, 1H), 3.25 (d, 1H), 3.75
(m, 4H), 3.9 (s, 3H), 4.1 (t, 2H), 5.75 (s, 1H), 6.3–7.5 (m,
11H, Ar). MS: m/z (rel. abundance): 471 (M+, 9.36), 114
(68.12), 100 (100). 4t: d 2.55 (m, 4H), 2.8 (m, 2H), 3.08 (d,
1H), 3.25 (d, 1H), 3.75 (m, 4H), 3.8 (s, 3H), 3.9 (s, 3H), 4.1
(t, 2H), 5.75 (s, 1H), 6.3–7.5 (m, 10H,Ar). MS: m/z (rel. abun-
dance): 501 (M+, 9.44), 114 (85.46), 100 (100). 4u: d 1.5–
1.85 (m, 6H), 2.85–3.2 (m, 8H), 3.8 (s, 3H), 4.4 (t, 2H), 5.75
(s, 1H), 6.3–7.5 (m, 11H, Ar). 4v: d 2.75 (m, 4H), 2.85 (t,
2H), 3.2 (m, 6H), 3.8 (s, 3H), 4.15 (t, 2H), 5.75 (s, 1H), 6.3–
7.5 (m, 16H, Ar). MS: m/z (rel. abundance): 501 (M+, 9.44),
114 (85.46), 100 (100). 4w: d 2.75 (m, 4H), 2.85 (t, 2H), 3.2
(m, 6H), 3.7 (s, 3H), 3.8 (s, 3H), 4.15 (t, 2H), 5.75 (s, 1H),
6.3–7.5 (m, 15H, Ar). MS: m/z (rel. abundance): 576 (M+,
26.52), 189 (63.46), 175 (100). 8a: d 1.45 (s, 6H), 3.45 (s,
2H), 3.8 (s, 3H), 6.4–7.45 (m, 7H, Ar). MS: m/z (rel. abun-
dance): 294 (M+, 5.48), 279 (15.19), 91 (100). 8b: d 1.5 (s,
6H), 3.45 (s, 2H), 3.8 (d, 6H), 6.45–7.45 (m, 6H, Ar). MS:
m/z (rel. abundance): 324 (M+, 13.78), 309 (100), 294 (6.88).
General method for the preparation of compounds (I)
4b–e, 4g, 4j–w, 8a,b
To a cold solution of 98% HCOOH (10 ml) and pyridine
(10 ml), 1 g of the selected pyrilium salt was added portion-
wise. The mixture was refluxed for 2 min, and then poured
into ice. The separated solid was collected by filtration, puri-
fied by flash chromatography and crystallized from ligroin.
Method for the preparation of compounds 4f and 4h
To a suspension of 11f or 11h (1 g) in benzene (50 ml),
P2O5 (11g) was added and the mixture was refluxed for 4h.
The mixture was cooled to room temperature, and poured
into ice. The organic phase was separated, washed with H2O,
dried, and evaporated. The residue was then purified by flash
chromatography and crystallized from ligroin.
General method for the preparation of compounds (II) 4i,
4k–w
To a suspension of NaBH4 (2 g) in THF (100 ml), 1.5 g of
the selected pyrilium salt was added portionwise under stir-
ring. Hydrogen gas developed and the reaction mixture decol-
orized. The mixture was then poured into ice and 10 ml HCl
and filtered (4i). Hydrochloride salts (4k–w) were resus-
pended in H2O, basified with K2CO3, extracted with CH2Cl2,
dried and evaporated to dryness. The residue was then puri-
fied by flash chromatography and crystallized from ligroin.
1H NMR and mass spectrum data for compounds 4b–w,
8a,b
4b: d 3.03 (d, 1H), 3.28 (d, 1H), 3.75 (s, 3H), 5.82 (s, 1H),
6.5–7.65 (m, 12H, Ar). MS: m/z (rel. abundance): 342 (M+,
95.2), 265 (100), 221 (6). 4c: d 3.08 (d, 1H), 3.30 (d, 1H),
3.78 (s, 3H), 5.78 (s, 1H), 6.7–7.65 (m, 12H, Ar). MS: m/z
(rel. abundance): 342 (M+, 100), 235 (69.01), 206 (6.18). 4d:
d 3.06 (d, 1H), 3.28 (d, 1H), 3.72 (s, 3H), 3.78 (s, 3H), 5.80
(s, 1H), 6.5–7.65 (m, 11H, Ar). MS: m/z (rel. abundance):
372 (M+, 100), 265 (85.06), 186 (12.5). 4e: d 3.1 (d, 1H),
3.26 (d, 1H), 3.78 (s, 3H), 5.82 (s, 1H), 6.3–7.6 (m, 12H, Ar).
MS: m/z (rel. abundance): 342 (M+, 65.95), 265 (100), 222
(6.71). 4f: d 3.08 (d, 1H), 3.28 (d, 1H), 3.72 (s, 3H), 3.78 (s,
3H), 5.81 (s, 1H), 6.4–7.65 (m, 11H, Ar). MS: m/z (rel. abun-
dance): 372 (M+, 100), 265 (85.06), 186 (12.5). 4g: d 3.04 (d,
1H), 3.27 (d, 1H), 3.75 (s, 3H), 3.77 (s, 3H), 5.81 (s, 1H),
6.3–7.6 (m, 11H, Ar). MS: m/z (rel. abundance): 372 (M+,
72.25), 295 (100), 186 (5.0). 4h: d 3.06 (d, 1H), 3.28 (d, 1H),
3.76 (s, 3H), 3.78 (s, 3H), 3.81 (s, 3H), 5.80 (s, 1H), 6.35–
7.55 (m, 10H, Ar). MS: m/z (rel. abundance): 402 (M+, 100),
387 (13.11), 295 (73.71). 4i: d (DMSO) 3.08 (d, 1H), 3.31 (d,
1H), 5.85 (s, 1H), 6.7–7.5 (m, 12H, Ar), 9.6 (s, 1H, OH). 4j:
d 1.8 (m, 4H), 2.65 (m, 4H), 2.90 (m, 2H), 3.08 (d, 1H), 3.2
(d, 1H), 3.7 (s, 3H), 3.8 (s, 3H), 4.02 (m, 2H), 5.78 (s, 1H),
6.35–7.75 (m, 10H, Ar). MS: m/z (rel. abundance): 485 (M+,
6-(4-Methoxyphenyl)-6a,12a-dihydro-6H,7H-chromeno
[4,3-b]chromene (6)
A solution of 4c (0.5 g, 0.0015 mol) in THF was hydroge-
nated at room temperature and pressure over Pd/C. The sol-
vent was evaporated, and the mixture purified by flash chro-
matography (toluene): 0.24 g (50%) of 6 were obtained, mp
143–144 °C (ligroin). 1H NMR: d 2.2–2.4 (m, 1H), 2.7–2.8
(m, 2H), 3.8 (s, 3H), 5.5 (s, 1H), 5.8 (m, 1H) 6.7–7.6 (m,
12H, Ar). Anal. (C23H18O3): C, H.