4
508 J . Org. Chem., Vol. 63, No. 13, 1998
Notes
Ch a r t 1
flask, methanol (70 mL) was added, and the mixture was stirred
at 20 °C until a brown solution was obtained. Powdery calcium
carbonate (10.5 g, 105 mmol) and ethyl vinyl ether (7 mL, 5.33
g, 73 mmol) were added, and to the resulting suspension was
added dropwise in 2 min under vigorous stirring a solution of
3
-aryl-1-[(trimethylsilyl)oxy]cyclohexene (5.0 g, 19 mmol) in ethyl
vinyl ether (7 mL, 5.3 g, 73 mmol). The mixture was made to
react at 20 °C until complete decolorization (30 min) and then
filtered on Celite, and the solvent was evaporated at reduced
pressure (15 mmHg) by a rotatory evaporator. The residue was
taken up by diethyl ether (100 mL), the ethereal solution was
washed with water, and the solvent was evaporated at reduced
1
pressure. The H NMR spectrum of the residual oil showed in
all cases two triplets and two doublets in the range δ 5.35-4.98,
which were assigned to the acetalic proton (CH(OR) ) of four
2
diastereoisomeric cyclic acetals (3) and a double-doublet and two
partially superimposed triplets in the range δ 4.4-4.2, which
were assigned to the acetalic protons of diastereoisomeric acyclic
acetals (2). Almost identical IR spectra were registered in all
cases, characterized by strong absorption at 3100-2740, 1708,
presence of chlorotrimethylsilane (Chart 1). The CAN-
promoted oxidative addition of 14 or 16 to ethyl vinyl
ether followed by the acid-catalyzed cyclization in 8:2
-
1
and 1112 cm . The spectral characteristics of the mixture 2 +
CHCl
3
3
-CF COOH mixture, in the presence of 1 equiv of
1
3
, Y ) 4-CH
3
(2/3 ) 1.3) are reported as representative: H NMR
CH ), 5.32 (t, J ) 6.0 Hz), 5.21 (t, J ) 6.0
DDQ, led to the unknown dihydronaphthothiophenones
δ 7.1-7.2 (m, C
6
H
4
3
1
5 and 17 in 40 and 38% yields, respectively, after 3 h.
Hz) 5.10 (d, J ) 6.5 Hz) 4.49 (d, 6.5 Hz), 4.43 (dd, J ) 7.4 and
Despite its simplicity, the very high regioselectivity,
3.1), 4.32 (t J ) 5.5 Hz), 4.31 (t, J ) 7.5 Hz), 3.95-3.30 (m,
and the satisfactory overall yields, this procedure un-
doubtedly suffers from severe limitations deriving mostly
from the failure of the cyclization step in the presence of
electron-withdrawing substituents on the aromatic ring
of the acetals 2 and 3. The method of Reetz used to
prepare the starting aryl-substituted [(trimethylsilyl)-
oxy]cyclohexenes also limits the number of substituents
on the phenanthrenones 4, due to the incompatibility of
the Grignard reagents with several functional groups.
However, in this respect, the scope of this procedure could
be significantly extended by considering the possibility
of obtaining aryl-substituted [(trimethylsilyl)oxy]cyclo-
hexenes by Diels-Alder cycloaddition of a variety of
homo- or heterodienophiles to 1-aryl-3-[(trimethylsilyl)-
oxy]-1,3-dienes, which could provide a valuable access to
a variety of important polysubstituted homo- or het-
erophenanthrenyl derivatives.
OCH
HCAr), 2.60-1.35 (m), 2.32 (s, C
partially seperimposed triplets, OCH
980-2840, 1708, 1512, 1446, 1247-1214, 814 cm
Cycliza tion in 80% Aqu eou s Su lfu r ic Acid . The above
2
CH
3
), 3.45-3.15 (eight singlets, OCH
CH ), 1.30-1.05 (four
CH ); IR (film) 3100-3020,
3
), 2.82-2.60 (m,
6
H
4
3
2
3
-
1
2
.
crude mixture was dissolved in methanol (20 mL) together with
DDQ (20 mmol), and the resulting solution was slowly added
dropwise (in 30 min) to 500 mL of aqueous 80% sulfuric acid at
0
°C. After the addition was complete, the ice bath was removed
and stirring continued for the time reported in the table. The
mixture was carefully diluted with ice water (200 mL) and
extracted with diethyl ether (3 × 50 mL), and the collected
organic extracts were washed with 100 mL of water and dried
over sodium sulfate. After solvent evaporation, the resulting
oil was chromatographed on silica gel (eluent, 9:1 petroleum
ether-diethyl ether) to obtain the pure Y-substituted 3,4-
dihydro-(2H)-phenanthren-1-ones which were identified as fol-
lows.
13
3
,4-Dih yd r o-(2H)-p h en a n th r en -1-on e: m.p 94-96 °C (lit.
1 13
mp 95-96 °C); H and C NMR data were identical to those
reported in the literature; IR (Nujol) 3057, 2995, 2949, 1720,
1
4
-
1
+
1
1
697, cm ; MS m/z (fel int) 196 (M , 85), 168 (79), 140 (100),
39 (61), 115 (9), 82 (8), 63 (15). Anal. Calcd for C14
Exp er im en ta l Section
12
H O
Unless otherwise specified, 1H and 13C NMR spectra were
(196.25): C, 85.68; H, 6.16. Found: C, 85.36; H, 6.21.
1
recorded at 200 and 50 MHz, respectively, in CDCl
3
in the
6-Meth yl-3,4-d ih yd r o-(2H)-p h en a n th r en -1-on e: H NMR
δ 8.05 (d, J ) 8.5 Hz, 1 H), 7.92 (d, J ) 1 Hz, 1 H), 7.77 (d, J )
8.5 Hz, 1 H), 7.72 (d, J ) 8.5 Hz, 1 H), 7.44 (dd, J ) 8.5 and 1
Hz, 1 H), 3.37 (t, J ) 6 Hz, 2 H), 2.7 (m, 2 H), 2.57 (s, 3 H), 2.3
(m, 2 H); 13C NMR δ 198.7, 142.3, 136.4, 133.9, 131.5, 130.4,
presence of TMS as internal standard. IR spectra were regis-
-1
tered in CHCl in the range 625-4000 cm . GLC analyses were
3
performed on a 30 m SPB-20 capillary column. Mass spectra
were registered at 70 eV.
Rea gen ts a n d Solven ts. All organic reagents (Aldrich), of
the highest grade of purity, were used as received, except ethyl
vinyl ether which was distilled before use. Ceric ammonium
nitrate (Baker 99%) was dried by heating at 80 °C for 1 h before
use. Methanol (Carlo Erba, ACS grade) was used without
further purification. Tetrahydrofuran was distilled from KOH
in the presence of CuCl and redistilled from sodium wire in the
presence of benzophenone. 3-Aryl-1-[(trimethylsilyl)oxy]cyclo-
hexenes 1 were prepared in 85-95% yield by CuI‚LiCl-catalyzed
conjugate addition of the corresponding arylmagnesium bro-
mides to 2-cyclohexenone in the presence of chlorotrimethylsi-
130.0, 128.5, 126.6, 124.0, 121.9, 38.4, 25.6, 22.8, 22.0; IR (CDCl
3
)
3060, 2995-2869, 1672, 1601, 1448, 1352, 1329, 1185, 1108, 843
-1
+
cm ; MS m/z (rel int) 210 (M , 100), 195 (20), 182 (43), 165 (18),
154 (47), 139 (8), 76 (5). Anal. Calcd for C15 14O (210.28): C,
H
85.68; H, 6.71. Found: C, 85.47; H, 6.82. GLC analysis showed
the presence of a second unseparable product (12%) to which
the structure of the regioisomer 8-m eth yl-3,4-d ih yd r o-(2H)-
p h en a n th r en -1-on e was tentatively assigned on the basis of
its mass spectrum which was almost identical to that of 6-methyl
+
regioisomer: MS m/z (rel int) 210 (M , 100), 195 (15), 182 (35),
165 (12) 154 (30), 139 (5), 76 (3).
5
lane according to the procedure of Reetz. GLC analysis showed
7-Meth yl-3,4-d ih yd r o-(2H)-p h en a n th r en -1-on e: mp 102-
1
a purity grade of up to 95% in all cases, the only impurity being
103 °C; H NMR δ 8.08 (d, 8.5 Hz, 1H) 8.03 (d, J ) 8.5 Hz, 1 H),
by the corresponding regioisomer 3-aryl-3-[(trimethylsilyl)oxy-
7.67 (d, J ) 8.5 Hz, 1 H), 7.64 (d, J ) 1 Hz, 1 H), 7.42 (dd, J )
8.5 and 1 Hz, 1 H), 3.37 (t, J ) 6 Hz, 2 H), 2.73 (dd, J ) 7.1 and
5.8 Hz, 2H), 2.54 (s, 3 H), 2.3 (m, 2 H); 13C NMR δ 198.5, 142.8,
138.4, 135.9, 135.8, 129.2, 128.8, 127.8, 126.2, 124.6, 122.8, 38.3,
5
]
cyclohexene. With the exception of the specific absorption of
the substituents on the aromatic ring, all of the 3-aryl-
substituted 1-[(trimethylsilyl)oxy]cyclohexenes exhibited very
1
similar H NMR spectra; that of 3-(m -tolyl)-1-[(tr im eth ylsi-
3
25.5, 22.7, 22.6; IR (CDCl ) 2994, 2945, 2869, 1703, 1670, 1453,
-
1
+
lyl)oxy]cycloh exen e is reported as representative: δ 7.2-7.0
1351, 1109, 909, 892 cm ; MS m/z (%) 210 (M , 100), 195 (18),
(
6
m, 4 H), 4.93 (m, 1 H), 3.44 (m, 1 H), 2.35 (s, 3 H), 2.4-1.3 (m,
H), 0.23 (s, 9 H).
(
13) Drake, N. L.; McVey, W. C. J . Org. Chem. 1939, 4, 464.
Gen er a l Oxid a tive Ad d ition P r oced u r e. Ceric ammo-
(14) Buchanan, G. W.; Tong, P. T.; Wightman, R. H.; Dawson, B. A.
nium nitrate (25 g, 46 mmol) was placed in a 0.25 L Erlenmeyer
Magn. Reson. Chem. 1989, 606.