6812 J . Org. Chem., Vol. 63, No. 20, 1998
Gonza´lez et al.
F igu r e 2. Detail of the PM3-optimized molecular structure of 17b. (a) Cyclohexene aleatory numbering used in the text. (b)
Geometry of the organic addend for 17b. (c) Minimum energy conformation of 17b. Bond lengths are in angstroms and bond
angles in degrees.
vacuum, and the crude product was column chromatographed
over silica gel 60 (Merck) using hexane/ethyl acetate as the
eluent, allowing the isolation of pure 5,6-dihydrocyclobuta[d]-
pyrimidines 4a -d and N-[1-(2′-oxocyclobutyl)]cyclobutyla-
mides 16a -c as byproducts.
2,4-Dim eth yl-5,6-d ih yd r ocyclobu ta [d ]p yr im id in e (4a ):
20% yield; bp 25 °C/2 mbar (bulb to bulb); 1H NMR (300 MHz,
CDCl3) δ 2.33 (s, 3H), 2.66 (s, 3H), 3.13 (dist. t, 2H), 3.36 (t, J
) 4.6 Hz, 2H); 13C NMR (75 MHz, CDCl3) δ 20.1, 26.5, 26.6,
35.0, 133.7, 157.9, 167.4, 173.0; MS m/z 174 (M+, 49), 93 (29),
66 (44), 52 (100), 42 (94).
(82), 123 (8), 119 (100), 95 (16), 81 (9). Anal. Calcd for C16H19-
NO2: C, 74.68; H, 7.44; N, 5.44. Found: C, 74.13; H, 7.19; N,
5.41.
2,4-Bis(4-ch lor op h en yl)-5,6-d ih yd r ocyclobu ta [d ]p yr i-
m id in e (4d ): 25% yield; mp 157-158 (MeOH); 1H NMR (300
MHz, CDCl3) δ 3.50, 3.62 (4H, dist. AA’BB’), 7.50, 7.63 (4H,
AA′BB′), 8.10, 8.50 (4H, AA′XX′); 13C NMR (75 MHz, CDCl3)
δ 29.0, 36.2, 128.6, 129.0, 129.2, 132.0, 134.0, 136.5, 136.9,
137.2, 153.5, 163.4, 174.5; IR (KBr) 1600, 1580, 1500, 1100,
800 cm-1; MS m/z 326 (M+, 100), 291 (82), 154 (38), 52 (92).
Syn th esis of Or ga n ofu ller en es 17a -d . Gen er a l P r o-
ced u r e. A solution of the corresponding dihydrocyclobutapy-
rimidine 4a -d and [60]fullerene in 10-20 mL of o-dichlo-
robenzene was heated under reflux for a variable period of
time. The solvent was removed under reduced pressure, and
the residue was purified by column chromatography on silica
gel. Further purification of the solid was accomplished by
washing and centrifuging three times with methanol.
1′,2′,3′,4′-Tet r a h yd r o-6′,8′-d im et h ylq u in a zolin o[2′,3′:
1,2][60]fu ller en e (17a ). According to the general procedure,
a solution of 2,4-dimethyl-5,6-dihydrocyclobuta[d]pyrimidine
(4a ) (30 mg, 0.22 mmol) and [60]fullerene (161 mg, 0.22 mmol)
in 10 mL of o-dichlorobenzene was refluxed for 24 h. The
product was purified by using toluene as the eluent, yielding
27 mg (14%, 96% based on consumed C60) of 17a : 1H NMR
(CDCl3/CS2) δ 2.79 (s, 3H), 2.87 (s, 3H), 4.66 (s, 2H), 4.73 (bs,
2H); 13C NMR (CDCl3) δ 26.9, 29.9, 39.6, 46.4, 67.7, 68.1, 110.6,
114.2, 125.5, 136.0, 140.1, 141.4, 141.8, 142.4, 142.9, 144.34,
144.5, 144.8, 145.2, 145.4, 146.0, 146.3, 155.0, 155.3, 163.0,
165.5, 166.4; FTIR (KBr): 2919, 1570, 1426, 1412, 1181, 766,
697, 577, 525 cm-1; MS m/z: 854 (M+, 33), 720 (C60, 100). UV-
vis (CHCl3), λmax (nm): 254, 294, 334, 434, 700.
N-[1-(2′-Oxocyclobu tyl)cyclobu tyl]acetam ide (16a): 20%
1
yield; mp: 107-108 °C (hexane); H NMR (300 MHz, CDCl3)
δ 2.10 (m, 11H), 2.90 (m, 2H), 4.15 (m, 1H), 5.56 (s, 1H); 13C
NMR (75 MHz, CDCl3) δ 13.2, 15.2, 27.8, 30.3, 31.0, 44.5, 56.5,
65.4, 169.3, 210.0; IR (KBr) 3250, 3050, 2990, 2950, 1775, 1630
cm-1; MS (CI, CH4) m/z (%): 182 (M + H, 30), 123 (81), 95
(100), 87 (71). Anal. Calcd for C10H15NO2: C, 66.27; H, 8.34;
N, 7.73. Found: C, 66.08; H, 7.77; N, 8.15
2,4-Dip h en yl-5,6-d ih yd r ocyclobu ta [d ]p yr im id in e (4b):
27% yield; mp: 118-119 °C (hexane); 1H NMR (300 MHz,
CDCl3) δ 3.53-3.61 (4H, AA’BB’), 7.51 (m, 5H), 8.25 (m, 3H),
8.54 (m, 2H); 13C NMR (75 MHz, CDCl3) δ 28.2, 36.3, 127.9,
128.2, 128.6, 129.0, 130.4, 131.1, 132.2, 135.9, 138.8, 155.0,
164.4, 174.4; IR (KBr) 3050, 1600, 1580, 1560, 1500, 760, 700
cm-1; MS m/z 258 (M+, 62), 155 (13), 104 (19), 77 (19), 52 (100).
N-[1-(2′-Oxocyclobu tyl)cyclobu tyl]ben zam ide (16b): 23%
yield; mp: 129-130 °C (hexane); IR (KBr) 3310, 1775, 1640,
730, 700 cm-1; 1H NMR (300 MHz, CDCl3) δ 2.05 (m, 8H), 2.95
(m, 2H), 4.25 (m, 1H), 6.40 (bs, 1H), 7.60 (m, 5H); 13C NMR
(75 MHz, CDCl3) δ 13.6, 15.5, 30.7, 31.5, 44.9, 57.0, 65.8, 127.0,
128.7, 131.6, 134.9, 166.9, 210.2; MS (CI, CH4) m/z (%): 244
(M + H, 22), 122 (65), 105 (100), 95 (23), 81 (16). Anal. Calcd
for C15H17NO2: C, 74.05; H, 7.04; N, 5.76. Found: C, 73.83;
H, 6.74; N, 5.75
2,4-Bis(4-m eth ylp h en yl)-5,6-d ih yd r ocyclobu ta [d ]p yr i-
m id in e (4c): 30% yield; mp: 162-163 °C (hexane); 1H NMR
(300 MHz, CDCl3) δ 2.40 (s, 6H), 3.40, 3.50 (4H, AA′BB′), 7.30
(m, 4H), 8.10, 8.45 (4H, AA′XX′); 13C NMR (75 MHz, CDCl3) δ
21.6, 21.7, 29.1, 36.2, 127.9, 128.1, 129.3, 129.7, 131.5, 133.2,
136.2, 140.4, 141.4, 154.7, 164.4, 174.0; IR (KBr) 1610, 1580,
1520, 795 cm-1; MS m/z 286 (M+, 66), 154 (23), 118 (33), 91
(16), 52 (100).
1′,2′,3′,4′-Tet r a h yd r o-6′,8′-d ip h en ylq u in a zolin o[2′,3′:
1,2][60]fu ller en e (17b). According to the general procedure,
a solution of 2,4-diphenyl-5,6-dihydrocyclobuta[d]pyrimidine
(4b) (40 mg, 0.16 mmol) and C60 (112 mg, 0.16 mmol) in
o-dichlorobenzene (20 mL) was refluxed during 69 h. The
product was purified by using CHCl3 as the eluent, yielding
70 mg (46%, 74% based on consumed C60) of 17b: 1H NMR
(300 MHz, CDCl3/CS2) δ 4.90 (bs, 2H), 4.98 (bs, 2H), 7.56-
7.58 (m, 6H), 7.89-7.91 (m, 2H), 8.73-8.76 (m, 2H); 13C NMR
(CDCl3/CS2) δ 40.7, 47.3, 64.8, 65.3, 128.6, 128.7, 128.8, 129.6,
129.8, 130.9, 137.4, 137.7, 140.3, 140.5, 141.8, 141.9, 142.0,
142.1, 142.2, 142.3, 142.7, 142.7, 143.2, 144.7, 144.8, 145.6,
145.6, 145.8, 145.8, 146.3, 146.4, 146.6, 147.7, 147.8, 155.8,
163.3, 163.7, 167.7; FTIR (KBr): 2919, 1550, 1425, 1392, 1180,
766, 748, 696, 525 cm-1; MS m/z: 978 (M+, 13), 720 (C60, 27);
UV-vis (CHCl3), λmax (nm): 256, 294, 318, 434, 702.
N -[1-(2′-Oxocyclob u t yl)cyclob u t yl]-4-m e t h ylb e n za -
1
m id e (16c): 26% yield; mp: 121-122 °C (hexane); H NMR
(300 MHz, CDCl3) δ 1.95 (m, 2H), 2.30 (m, 6H), 2.40 (s, 3H),
2.95 (m, 2H), 4.25 (m, 1H), 6.40 (br s, 1H), 7.40 (m, 4H); 13C
NMR (75 MHz, CDCl3) δ 13.5, 15.5, 21.5, 30.8, 31.4, 44.8, 57.0,
67.8, 127.0, 129.3, 132.1, 142.0, 166.8, 210.3; IR (KBr) 3300,
1785, 1640 cm-1; MS (CI, CH4) m/z (%): 258 (M + H, 36), 136
1′,2′,3′,4′-Tetr ah ydr o-6′,8′-bis(p-m eth ylph en yl)qu in azoli-
n o[2′,3′:1,2][60]fu ller en e (17c). According to the general