Chemistry of anti-o,o′-Dibenzene
J. Am. Chem. Soc., Vol. 119, No. 32, 1997 7479
26.02, 24.74; IR (KBr) 2983, 2926, 2908, 1372, 1257, 1223, 1206,
1159, 1068, 1042, 1006, 931, 886, 870 cm-1; MS (CI+, isobutane) m/e
305 (M + 1), 289, 247, 189, 171 (100), 143. Anal. Calcd for C18H24O4;
C, 71.03; H,7.95. Found: C, 70.99; H, 7.81. 20: mp 147-149 °C;
1H NMR (CDCl3) δ 5.97 (2H, m, olefinic H), 5.57 (1H, ddd, J ) 10.4,
4.0, 1.2 Hz, olefinic H), 5.49 (1H, dd, J ) 10.2, 1.3 Hz, olefinic H),
4.30 (1H, dd, J ) 7.3, 3.1 Hz, -CH(OR)-), 4.26 (1H, dd, J ) 7.2,
3.0 Hz, -CH(OR)-), 4.18 (1H, d, J ) 1.6 Hz, -CH(OR)-), 4.17
(1H, d, J ) 1.4 Hz, -CH(OR)-), 2.86 (2H, m, HCC3), 2.34 (1H, m,
HCC3) 2.22 (1H, d, J ) 9.1 Hz, HCC3), 1.35 (3H, s, -CH3), 1.33 (3H,
s, -CH3), 1.31 (3H, s, -CH3), 1.28 (3H, s, -CH3); 13C NMR (CDCl3)
δ 132.36, 129.30, 128.79, 126.65, 108.57, 107.61, 78.58, 78.34, 77.60,
70.86, 40.97, 40.70, 34.30, 33.13, 28.30, 26.81, 25.38, 24.97; IR (KBr)
2988, 2932, 1377, 1365, 1237, 1229, 1061, 1046, 887 cm-1; MS (CI+,
isobutane) m/e 305 (M + 1), 247 (100), 189, 171, 129, 95. Anal. Calcd
for C18H24O4; C, 71.03; H,7.95. Found: C, 71.13; H, 8.04. 18: mp
Experimental Section
General Information. Chemicals obtained commercially were used
without further purification unless otherwise noted. CAN, DBA, DCA,
DPA, perylene, rubrene, thioxanthen-9-one, and xanthone were recrys-
tallized before use. DMA was purified by following a procedure in
the literature.85 1,8-Diazabicyclo[5.4.0.]undec-7-ene (DBU) and DMF
dimethyl acetal (94%) were distilled at reduced pressures prior to use.
N,N-Diisopropylethylamine, pyridine, 2,2,6,6-tetramethylpiperidine, and
triethyl amine were dried by refluxing over and then distilling from
drying agents. Potassium tert-butoxide (95%) was purified by sublima-
tion. Solvents used for photocycloadditions and other anhydrous
reactions were purified by procedures in the literature.85
Melting points are reported uncorrected. 1H NMR spectra were
obtained at 500 MHz on a Chicago DS-1000 spectrometer. The proton
NMR peaks of some compounds were assigned on the basis of double
irradiation experiments. 13C NMR was obtained either at 100 MHz
on a Varian XL-400 FT-NMR spectrometer or at 75 MHz on a General
Electric NMR QE-300 spectrometer. Chemical shifts (δ) are reported
as parts per million (ppm) downfield from TMS. Infrared (IR) spectra
were recorded on a Nicolet Instrument Corporation 20 SXB FT-IR
spectrometer. Ultraviolet and visible spectra were recorded on a Varian
Cary 219 UV/vis spectrophotometer or a Perkin-Elmer Lambda 5 UV/
vis spectrophotometer. Fluorescence spectra were recorded on a Perkin-
Elmer MPF-66 fluorescence spectrophotometer. Mass spectra (MS)
were obtained on a VG 70-250 double focusing magnetic sector mass
spectrometer. Chemical ionization (CI) mass spectra were obtained
with isobutane as the reagent gas. Elemental analyses were performed
by Micro-Tech Laboratories, Inc., Skokie, IL or by Midwest Microlab,
Indianapolis, IN.
1
(hexane) 211-212 °C; H NMR (CDCl3) δ 5.81 (2H, dd, J ) 10.2,
1.8 Hz, olefinic H), 5.62 (2H, d, J ) 10.4 Hz, olefinic H), 4.42 (2H,
m, -CH(OR)-), 4.41 (2H, m, -CH(OR)-), 2.83 (2H, m, J ) 6.0
Hz, cyclobutyl H), 2.64 (2H, d, J ) 6.3 Hz, cyclobutyl H), 1.45 (6H,
s, -CH3), 1.37 (6H, s, -CH3); 13C NMR (CDCl3) δ 129.48, 125.82,
108.22, 72.73, 71.23, 37.33, 30.83, 28.18, 26.56; IR (KBr) 3029, 2983,
2941, 2870, 1375, 1371, 1230, 1160, 1098, 1069, 1033, 1024, 925,
873 cm-1; MS (CI+, isobutane) m/e 305 (M + 1), 247, 189 (100), 171,
143, 95. Anal. Calcd for C18H24O4; C, 71.03; H, 7.95. Found: C,
71.12; H, 8.04.
Thermal dimerization of 16. Diene 16 (2.51 g, 1.65 × 10-2 mol)
in a 10-mL round bottom flask under nitrogen was immersed into a
120 °C oil bath. After 12 h, the reaction mixture was cooled to room
temperature to form a yellow powder. The proton NMR spectrum of
this reaction mixture showed mainly 20. No peaks representing 17,
18, or 19 were observed. Silica gel column chromatography eluting
with CH2Cl2-EtOAc yielded 2.22 g of 20 (88%).
General Preparative Irradiation Procedure. Most preparative
irradiations were performed with a 450 W Hanovia medium pressure
mercury lamp irradiating through a cylindrical Vycor, Pyrex, or Uranyl
filter which was placed between the light source and a quartz immersion
well cooled with water. The immersion well was inserted in a Pyrex
jacket equipped with a condenser and an argon gas dispersion inlet
tube. The reaction solutions were placed into the outer jacket and
purged with argon for more than 20 min before irradiation. During
the irradiation a gentle stream of argon was maintained. The reactions
were followed with either TLC or proton NMR spectrum analysis.
Hydrolysis of 17 (Preparation of 23). In a 1-L round bottom flask,
17 (2.00 g, 6.57 × 10-3 mol) was dissolved in 600 mL of 60% acetic
acid in water. After standing overnight, the acetic acid and water were
removed under vacuum to give a yellowish solid. After washing with
chloroform, the crude tetraol 17 was recrystallized from 90% ethanol
1
in water to afford white crystals (1.30 g, 88%): mp 275-277 °C; H
NMR (DMSO-d6) δ 5.76 (2H, dd, J ) 9.9, 1.6 Hz, olefinic H), 5.60
(2H, dd, J ) 10.0, 2.2 Hz, olefinic H), 4.51 (2H, d, HCO), 4.06 (2H,
s, -OH), 4.05 (2H, s, -OH), 3.67 (2H, br d, J ) 3.7 Hz, HCO), 2.38
(2H, br d, cyclobutyl H), 2.21 (2H, br s, cyclobutyl H); 13C NMR
(DMSO-d6) δ 138.00, 128.98, 68.10, 65.02, 38.34, 36.13; IR (KBr)
3370-3270 (strong, br), 3026, 2913, 2884, 1390, 1346, 1342, 1229,
Photosensitized Dimerization of 16. Diene 16 (3.22 g, 2.12 ×
10-2 mol) and thioxanthen-9-one (0.120 g, 5.65 × 10-4 mol) were
dissolved in 100 mL of dry benzene. After deaeration by bubbling
with argon gas, the solution was cooled in an ice-water bath and
irradiated for 40 min through a Uranyl glass filter. Silica gel
chromatography of the mixture eluting with hexane-EtOAc, followed
by recrystallization from hexane gave four products: 17 (1.462 g, 45%),
19 (0.32 g, 10%), 20 (0.122 g, 4%), and 18 (35 mg, 1%). 17: mp
1148, 1099, 1055, 1025, 846 cm-1
. Anal. Calcd for C12H16O4; C,
64.27; H, 7.19. Found: C, 64.21; H, 6.97.
Synthesis of 1. Tetraol 23 (1.00 g, 4.46 × 10-3 mol) was added to
5 mL of DMF dimethyl acetal (3.76 × 10-2 mol). This mixture was
stirred at 55 °C under nitrogen for 15 h or until a clear solution was
obtained. The excess DMF acetal was removed under vacuum to yield
acetal 24 as a yellow viscous liquid. To the crude cyclic DMF acetal
24 in 200 mL of dry CH2Cl2 was added N,N-diisopropylethylamine
(3.5 mL, 2.01 × 10-2 mol, 4.51 equiv) under nitrogen, and the solution
was cooled with an ice-water bath. A solution of trifluoromethane-
sulfonic anhydride (1.7 mL, 1.01 × 10-2 mol, 2.26 equiv) in 100 mL
of dry CH2Cl2 was added dropwise over 40 min. After 30 min of
additional stirring, 3 mL of DBU was added to the reaction mixture.
The volume of the reaction mixture was reduced to approximately 100
mL under reduced pressure and then passed through a silica gel column
with CH2Cl2. Evaporation of the eluent yielded a yellowish oil which
was further chromatographed over a silica gel column with pentane as
eluent to yield 0.45 g (65%) of 1 and 38 mg of biphenyl (6%).
Sublimation of 1 gave white crystals: mp 27-29 °C; 1H NMR (CDCl3)
δ 5.70 (4H, dd, J ) 8.0, 2.6 Hz, olefinic H), 5.64 (4H, d, J ) 8.3 Hz,
olefinic H), 3.26 (4H, br s, cyclobutyl H); 13C NMR (CDCl3) δ 127.50,
121.72, 43.75; IR (CHCl3) 3057, 3032, 3012, 2931, 2879, 1734, 1579,
1377, 1038 cm-1; UV (cyclohexane) λmaxnm (ꢀ): 266 (6000); MS (CI+,
isobutane) m/e 157 (M + 1 - 2H, very weak), 155 (100), 128, 115;
MS (EI+) m/e 156 (M - 2H, very weak), 154 (100), 152, 141, 128,
115.
1
158-159 °C; H NMR (CDCl3) δ 5.82 (2H, dd, J ) 10.4, 3.4 Hz,
olefinic H), 5.66 (2H, dd, J ) 10.4, 1.1 Hz, olefinic H), 4.54 (2H, m,
-CH(OR)-), 4.32 (2H, d, J ) 5.7 Hz, -CH(OR)-), 2.65 (2H, d, J )
5.6 Hz, cyclobutyl H), 2.39 (2H, br s, cyclobutyl H), 1.36 (6H, s,
-CH3), 1.34 (6H, s, -CH3); 13C NMR (CDCl3) δ 128.65, 125.54,
109.32, 72.37, 70.41, 35.01, 32.52, 28.13, 26.69; IR (CCl4) 3026, 2986,
2936, 2915, 2866, 1379, 1369, 1236, 1166, 1155, 1067, 1053, 1020,
869 cm-1; MS (CI+, isobutane) m/e 305 (M + 1), 247, 189 (100), 171,
143. Anal. Calcd for C18H24O4; C, 71.03; H,7.95. Found: C, 70.90;
H, 7.99. 19: mp 141-143 °C; 1H NMR (CDCl3) δ 5.98 (2H, s, olefinic
H), 5.82 (1H, dd, J ) 10.3, 3.8 Hz, olefinic H), 5.67 (1H, d, J ) 10.2
Hz, olefinic H), 4.56 (1H, dd, J ) 6.8, 2.7 Hz, -CH(OR)-), 4.51
(1H, d, J ) 4.2 Hz, -CH(OR)-), 4.42 (1H, dd, J ) 5.8, 2.2 Hz,
-CH(OR)-), 4.17 (1H, dd, J ) 6.8, 5.8 Hz, -CH(OR)-), 3.03 (1H,
m, HCC3), 2.50-2.43 (2H, m, HCC3) 2.28 (1H, m, HCC3), 1.51 (3H,
s, -CH3), 1.41 (3H, s, -CH3), 1.35 (3H, s, -CH3), 1.32 (3H, s, -CH3);
13C NMR (CDCl3) δ 132.85, 128.75, 126.30, 122.35, 108.95, 108.00,
73.51, 71.75, 70.40, 69.64, 38.50, 34.53, 33.19, 32.73, 28.12, 26.54,
(85) Perrin, D. D.; Armarego, W. L. F.; Perrin, D. R. Purification of
Laboratory Chemicals; Pergamon Press: Oxford, 1980.
(86) Hatchard, C. G.; Parker, C. A. Proc. Roy. Soc. 1956, A235, 518-
536.
(87) Schaap, A. P.; Thayer, A. L.; Blossey, E. C.; Neckers, D. C. J. Am.
Chem. Soc. 1975, 97, 3741-3745.