2590 J . Org. Chem., Vol. 63, No. 8, 1998
Aplin and Bauld
found to be 99% pure by GC: mp 98.5-99.8 °C; 1H NMR δ 1.2
(t, 6H), 3.0 (q, 4H), 7.1 (d, 4H), 8.0 (d, 4H); 13C NMR δ 8.2,
31.7, 66.3, 118.8, 130.4, 160.2, 199.5; IR (CdO) 1684; LRMS
m/e 282 (M+), 271, 197, 196, 139, 120, 92 (base).
of dimer and low oligomers, and 0.090 g (18.0%) of high
oligomers/polymer were isolated: 1H NMR for polymer methyl
groups δ 0.8 (acid catalysis), 1.1 (cation radical catalysis); the
integrated signals gave an acid:CB linkage ration of 1:1; 13C
NMR for polymer methyl groups δ 13 (acid), 15.5 (tst), and
18.09 (tat); CIMS m/e 1250 (pentamer), 1002 (tetramer + 2
mass units), 751 (trimer + 1), 501 (dimer + 1), 250 (monomer).
P olym er iza t ion of 3 w it h 2,6-Di-ter t-b u t ylp yr id in e
(DTBP ). To 0.382 g (153 mmol) of 3 in 8 mL of dry DCM was
added 0.177 g (0.93 mmol) of DTBP followed by the addition
of 0.595 g (0.73 mmol) of 2•+ dissolved in 5 mL of dry DCM
over 1 min. The reaction was stirred for 15 min and quenched.
After workup and PTLC, 0.208 g (52.4%) of 3, 0.77 g (33.2%)
of dimer and trimer, and 0.080 g (20.9%) of high oligomers/
polymer were isolated. 1H and 13C NMR of the fraction
assigned by TLC to be dimer/trimer gave no resonances for
acid lingages: CIMS m/e 2000 octamer, 1750, 1500, 1250, 751,
501, 250.
P olym er iza tion of 3 a t Low Con cen tr a tion . The po-
lymerization of 3 was performed exactly as above with the
exception that the concentration was 0.02 M lower. This
resulted in the formation of the acid-catalyzed polymer as
before, but the isolated material was soluble.
Acid -Ca ta lyzed P olym er iza tion of 5. To a solution of
triflic acid (0.066 g, 8.7%) in 4 mL of dry DCM at 0 °C was
added 1.057 g (5.03 mmol) of 5 in 8 mL of dry DCM. After 5
min, 10 mL of saturated aqueous NaHCO3 was added along
with 10 mL of additional DCM. The organic layer was isolated,
washed with 20 mL of water, and dried to give 0.976 g (92%
recovery) of solid. Hexane was used to wash the solid, and
0.140 g (13% yield) of insoluble material was isolated by
vacuum filtration. Only the aliphatic resonances are re-
ported: 1H NMR δ 0.8 (methyl), 1.7 (methine), 2.1 (benzyl);
13C NMR δ 13 (methyl), 34 (methine), 48 (benzyl).
P ET Syn th esis of th e tr a n s,syn ,tr a n s-Cyclobu ta n e
Dim er (7) of 3. To a dry Pyrex test tube was added 0.500 g
(2.0 mmol) of 3, 0.025 g (0.19 mmol) of dicyanobenzene, and
10 mL of dry DCM. The test tube was capped with a septum
and the reaction irradiated with a medium-pressure mercury
lamp for 24 h. The solvent was removed, and column chro-
matography was performed (9:1 hexane and DCM). The
trans,syn,trans-cyclobutane dimer (0.200 g, 40% yield) and 2
(0.050 g, 10% recovery) were isolated with no higher oligomers
observed. The assignment of the structure of the dimer is
based on its similarity to the dimer of trans-anethole:6 1H
NMR δ 1.2 (d, 6H), 1.9 (d, 6H), 2.8 (d, 2H), 3.5 (d, 2H), 6.1 (m,
2H), 6.4 (d, 2H), 6.8 (m, 8H), 7.1 (m, 8H); 13C NMR δ 15.1,
18.4, 34.2, 49.6, 117.7, 118.2, 118.8, 125.0, 126.2, 129.3, 130.1,
136.0, 156.5; LRMS m/e 498 (M - 2H), 444, 334, 250 (base),
117.
P r ep a r a tion of 6 by th e Dim er iza tion of 5 Usin g
Tr is(4-b r om op h en yl)a m in iu m H exa ch lor oa n t im on a t e
(2•+). To 1.047 g (4.99 mmol) of 5 in 20 mL of dry DCM at 0
°C was added 0.204 g (0.25 mmol) of 2•+ as a solid. After 5
min of stirring, the reaction was quenched with saturated
K2CO3 in methanol. Excess water and DCM were added, and
the organic layer was isolated. The organic solution was
washed three times with water and dried. TLC analysis of
the crude product mixture showed three spots identified as 5,
the cyclobutane dimer of 5 (6), and polymer. Column chro-
matography (9:1 hexane and DCM) allowed for the isolation
of 5 and 6 as a mixture followed by PTLC (hexane) to separate
5 and 6. After PTLC, 0.67 g (64% recovery) of 5, 0.18 g (36%
yield) of 6, and 0.15 g (15% of recovered material) of polymer
were isolated (95.5% mass balance). The assignment of the
structure of the dimer is based on its similarity to the dimer
of trans-anethole 5. Only the aliphatic resonances are re-
ported: 1H NMR δ 1.2 (6H, d, trans,syn,trans (tst) and
trans,anti,trans (tat) methyl), 1.88 (2H, m, tst benzyl); 13C
NMR of tst δ 15.2, 34, 49, tat δ 18.90, 43.3, 52.4.
Bis[4-(1-h yd r oxyp r op yl)p h en yl] Eth er . The diketone
obtained in the preceding reaction (20 g, 0.071 mole) was
dissolved in 200 mL of a 3:1 ethanol:tetrahydrofuran mixed
solvent, and solid NaBH4 (5.0 g, 0.13 mol) was added. After
1.5 h at room temperature, the reaction was quenched with
excess 10% acetic acid at 0 °C. The aqueous solution was
extracted with dichloromethane (3 × 100 mL), and the
combined organic extracts were washed with saturated aque-
ous NaHCO3 (2 × 100 mL) and water (2 × 100 mL). The
solution was then dried and the solvent removed on a rotary
evaporator, giving 20.5 g of the diol product (99.7%) as an oil
which was used without further purification: 1H NMR δ 0.9
(t, 6H), 1.6-1.9 (m, 4H), 2.6 (br s, 2H), 4.5 (t, 2H). 6.9 (d, 4H),
7.2 (d, 4H); 13C NMR δ 10.2, 31.9, 75.4, 118.6, 127.4, 139.5,
156.5; IR (OdH) 3360.
Bis[4-(1-p r op en yl)p h en yl] Eth er . The diol obtained in
the preceding reduction (6.31 g, 0.02 mol) was dissolved in
pyridine (25 mL) at room temperature, followed by the addition
of POCl3 (7 g, 0.045 mol). The solution was then refluxed for
2 h, cooled in an ice bath, and quenched by adding water
slowly. The quenched reaction mixture was then transferred
to a separatory funnel containing 100 mL of ethyl acetate,
washed with water, and dried, and the solvent was removed
by rotary evaporator. The crude product was chromato-
graphed on alumina, yielding 3.96 g (71.8%) of 3, upon elution
with 1:1 hexane:dichloromethane. The product was found to
be pure (GC), but consisted of a mixture of E,E (87%), Z,E
(11%), and Z,Z (2%) isomers: mp 117-119 °C; λmax 270 nm,
1
log ꢀ 2.4; H NMR δ 1.9 (dd, 6H), 6.1 (dq, 2H, J trans 15.8), 6.4
(d, 2H, J trans 15.8), 6.9 (d, 4H), 7.4 (d, 4H); 13C NMR δ 18.4,
66.8, 118.8, 124.7, 126.9, 130.2, 131.2, 156.1; IR (CdC) 1590.
LRMS m/e 250 (M+), 207, 179, 165, 133, 115 (base), 91; HRMS
m/e calcd for C20H22O2 250.1358, found 250.1369; Eopx 1.36 V
(vs SCE).
Gen er a l P r oced u r e for th e P olym er iza tion of 3 Usin g
2•+. The polymerizations were run at a monomer concentra-
tion of 0.2 M at 0 °C in dry dichloromethane under dry
nitrogen. A catalytic amount of 2•+ (usually 5 mol %) was
added to the reaction mixture as a solid in one portion or as a
solution in 1-5 mL of dry dichloromethane at 0 °C. The
catalyst solution was added slowly over a period of 1-15 min,
and the reaction was stirred for an additional 4-10 min. The
polymerizations were quenched with a saturated solution of
K2CO3 in MeOH, and an aqueous workup was performed by
adding excess DCM and water and then filtering off any solid
that remained. The organic solution was washed three times
with water and dried over magnesium sulfate. The solvent
was removed, and purification was accomplished using PTLC
or column chromatograhy (9:1 hexane and dichloromethane).
TLC was performed to verify the separation, and in some
instances the oligomers, especially the higher ones, were not
cleanly separated. Insoluble material was characterized by
solid-state 13C NMR. Soluble material was characterized by
one or more of the following methods: room- and high-
temperature 1H and 13C NMR, CIMS, TLC, and GPC.
P olym er iza tion of 3 w ith No Ad d ed Ba se. To 0.990 g
(3.96 mmol) of 3 in 8 mL of dry DCM was added 0.170 g (0.21
mmol) of 2•+ dissolved in 5 mL of dry DCM over 15 min. After
10 min of additional reaction time, no further agitation was
observed and the reaction was quenched (the blue-black color
of the reaction mixture was slow to dissipate). After workup,
0.805 g (81.3%) of a tan solid was isolated and found to be
insoluble in common solvents under any conditions, including
diphenyl ether at 250 °C: solid state 13C NMR δ 12, 20, 35,
43, 120, 130, 155.
P olym er iza tion of 3 w ith Sod iu m Ca r bon a te. To 0.501
g (2.00 mmol) of 3 in 8 mL of dry DCM was added 3.05 g (28.8
mmol) of Na2CO3 followed by the addition of 0.166 g (0.020
mmol) of 2•+ for 2 min and quenched. After workup and
column chromatography, 0.198 g (39.5%) of 3, 0.078 g (15.6%)
Ack n ow led gm en t. The authors thank the Robert
A. Welch Foundation (F-149) for supporting this research.
J O972072N