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Can. J. Chem. Vol. 84, 2006
lution was then concentrated down to a few mL of volume
by rotary evaporator, applied to the top of a SiO2 column,
and eluted with hexane–EtOAc (9:1), which after removal of
solvent afforded 3.2 g of carbene complex 17 as a red solid
(80% yield). Rf = 0.275 (hexane–EtOAc, 9:1). IR (neat film,
NaCl, cm–1): 2062 (m), 1988 (w), 1940 (s). 1H NMR
(300 MHz, CD2Cl2) δ: 2.47 (m, 2H), 2.86 (m, 2H), 4.14
(br s, 3H, methoxy), 5.76 (t, 1H, J = 4.5 Hz), 7.38 (t, 6H,
J = 7.0 Hz), 6.78 (s, 1H), 7.52 (d, 6H, J = 7.6 Hz), 7.24–
7.57 (m, 5H). 13C NMR (75 MHz, CD2Cl2) δ: 22.7, 27.8,
66.1, 123.4, 128.3, 128.6, 129.7, 130.0, 130.1, 132.2, 134.3,
135.9, 136.4, 136.6, 137.8, 216.5 (CO), 225.1 (CO), 358.6
(carbene C). MS (FAB, nitrobenzyl alcohol) m/z (%): 622
[M+] (3), 594 [M+ – CO] (5), 483 (44), 482 (87), 467 (37),
452 (18), 259 (100).
Aromatization of the B-ring of intermediate (18)
AcO
Ph
AcO
Ph
NBS
SiPh3
SiPh3
OMe
OMe
19 91%
18
A 500 mL RB flask was charged with starting material 18
(2.17g, 3.6 mmol), N-bromosuccinimide (673 mg,
3.78 mmol), benzoyl peroxide (89 mg, 0.36 mmol), and ben-
zene (200 mL). The magnetically stirred solution was
refluxed for 9 h. Upon cooling, the solution was filtered
through a short plug of Al2O3 and then purified by SiO2
chromatography (hexane–EtOAc, 5:1) to afford 1.97 g of 19
as a white crystalline solid (91% yield); mp 237 to 238 °C.
Rf = 0.31 (hexane–EtOAc, 4:1). IR (neat film, NaCl, cm–1):
3066 (w), 3048 (w), 2922 (w), 1763 (m), 1428 (m), 1197 (s),
The benzannulation reaction of complex 17 with
phenylacetylene (3)
1
1108 (ms), 1049 (mw). H NMR (500 MHz, CDCl3) δ: 2.14
(s, 3H), 3.61 (s, 3H), 6.98 (s, 1H), 7.28–7.39 (m, 11H), 7.47
(d, 2H, J = 7.3 Hz), 7.63 (d, 6H, J = 7.2 Hz), 7.73 (m, 4H),
7.83 (d, 1H, J = 7.8 Hz), 9.89 (s, 1H). 13C NMR (75MHz,
CDCl3) δ: 20.7, 55.4, 109.6, 120.5, 120.8, 127.6, 127.9,
128.4, 128.8, 129.1, 129.5, 132.0, 132.8, 132.9, 133.0,
133.2, 134.6, 136.6, 136.9, 137.3, 137.8, 138.0, 156.6,
169.7, (1C not located). EI-MS m/z (%): 602 [M+ + 2] (8),
601 [M+ + 1] (15), 600 [M+] (30), 560 (21), 559 (45), 558
[M+ – ketene] (100), 481 (8), 465 (10), 387 (10), 260 (17),
259 Ph3Si+ (66,), 230 (19), 181 (14), 220 (15), 181 (8).
1) PhC
/
CH
AcO
Ph
SiPh3
SiPh3
2) Ac2O, NEt3
MeO
Cr(CO)5
17
OMe
18 74%
Carbene complex 17 (3.2 g, 5.15 mmol) was dissolved in
150 mL of THF in a 250 mL single-necked RB flask, which
had the joint replaced with a threaded high-vacuum Teflon
stopcock. Phenylacetylene (0.85 mL, 7.72 mmol) was added
and the solution was deoxygenated by the freeze-pump-thaw
method (3 cycles, –196 °C and 20 °C). The flask was
charged with Ar at RT and then sealed and warmed at 60 °C
for 21 h. After cooling to RT, triethylamine (1.79 mL,
12.87 mmol) and 1.19 mL acetic anhydride (12.6 mmol)
were added. The flask was resealed and warmed to 60 °C for
8 h and then stirred at RT overnight. The crude mixture was
concentrated down to a few mL of volume by rotorary evap-
orator, applied to the top of a SiO2 column, and eluted with
hexane–EtOAc 9:1). The product fraction was collected
(Rf = 0.22, hexane–EtOAc (9:1)) as well as a more polar yel-
low band, which was the arene chromium tricarbonyl com-
plex of the product. This yellow compound was dissolved in
CHCl3 and stirred overnight in open air to remove the chro-
mium. This was then passed through a short SiO2 pad to fil-
ter off the green flocculent chromium byproduct. The
resulting product was combined with the earlier collected
product to afford 2.3 g of a white crystalline solid (74%
yield); mp 228–229.5 °C. IR (neat film, NaCl, cm–1): 3067
(w), 3048 (w), 2933 (w), 1761 (ms), 1460 (m), 1428 (m),
1367 (m), 1211 (s), 1186 (s), 1108 (ms), 1059 (m), 701 (vs).
1H NMR (500 MHz, CDCl3) δ: 2.07 (s, 3H), 2.78 (t, 2H, J =
6.4 Hz), 2.50–2.85 (m, 2H), 3.56 (s, 3H), 6.76 (s, 1H), 7.21–
7.29 (m, 2H), 7.31–7.39 (m, 14H), 7.58 (d, 6H, J = 7.0 Hz),
8.51 (s, 1H). 13C NMR (75MHz, CDCl3) δ: 20.5, 23.1, 28.9,
55.4, 111.6, 123.8, 127.0, 127.5, 127.8, 128.8, 129.4, 131.1,
131.5, 133.1, 134.1, 134.6, 135.1, 136.5, 136.9, 138.0,
138.5, 139.6, 154.7, 169.4. EI-MS m/z (%): 604 [M+ + 2]
(10), 603 [M+ + 1] (27), 602 [M+] (51), 562 (15), 561 (48),
560 [M+ – ketene] (100), 483 (14), 259 Ph3Si+ (73), 230
(19), 181 (14). Anal. calcd. for C41H34O3Si: C 81.70, H
5.64; found: C 81.53, H 5.62.
Bromo-desilylation of phenanthrene (19)
AcO
Ph
AcO
Ph
SiPh3
Br
Br2
OMe
OMe
20 83%
19
A 100 mL RB flask with a stir bar was charged with
phenanthrene 19 (342 mg, 0.57 mmol), CH2Cl2 (20 mL),
and 5.1 mL of a 0.3 mol/L solution of Br2 in CH2Cl2
(1.54 mmol). The mixture was brought to reflux for 3.5 h
and then stirred at RT for 20 h. A small amount of SiO2 was
poured into the reaction mixture. Solvent was removed in
vacuo to adsorb the crude reaction material on the silica.
This SiO2 adsorbate was applied to the top of a silica gel
column and eluted with hexane–EtOAc (4:1) to afford
199 mg of 20 as a white solid (83% yield). The desired
product elutes from the column after an orange impurity
elutes. On scaling up the reaction, it was more efficacious to
use slightly less Br2 (~2 equiv.) to avoid this separation.
Melting point 203.5–205 °C. Rf = 0.36 (hexane–EtOAc, 4:1).
IR (neat film, NaCl, cm–1): 2922 (w), 1761 (ms), 1589
(mw), 1440 (m), 1368 (m), 1212 (m), 1196 (vs), 1048 (m).
1H NMR (300 MHz, CDCl3) δ: 2.17 (s, 3H), 4.11 (s, 3H),
7.13 (s, 1H), 7.32–7.44 (m, 4 H), 7.56 (d, 1H, J = 7.9 Hz),
7.61 (dd, 1H, J = 7.6, 1.4 Hz), 7.64–7.68 (m, 1H), 7.70 (d,
2H, J = 9.5 Hz), 9.84 (s, 1H). 13C NMR (75 MHz, CDCl3) δ:
20.7, 55.9, 109.6, 120.5, 121.1, 127.7, 127.8, 127.9, 128.4,
128.6, 129.0, 129.4, 129.6, 130.0, 131.1, 132.7, 134.9,
136.5, 137.7, 156.4, 169.6. EI-MS m/z (%): 423 [M+ + 1] (5,
© 2006 NRC Canada