2,2′-(2,2-Diarylethenyl)binaphthyl-Type Electron Donors
UV-vis (CH3CN) λmax 347 sh (log ꢀ 4.57), 321 (4.65), 262 (4.61)
nm. Anal. Calcd for C48H50N4: C, 84.42; H, 7.38; N, 8.20.
Found: C, 84.67; H, 7.53; N, 8.18.
To a solution of (S)-2,2′-dimethylbinaphthyl (430 mg, 1.5
mmol) in dry TMEDA (500 µL) was added dropwise n-BuLi
(1.57 mol dm-3 in n-hexane, 2.10 mL, 3.4 mol) at 23 °C under
Ar, and the mixture was stirred for 20 h at this temperature.
Then, to the resultant suspension of (S)-2,2′-bis(lithiomethyl)-
binaphthyl was added a suspension of 4,4′-bis(dimethylamino)-
benzophenone (1.02 g, 3.8 mmol) in dry THF (15 mL) at -15
°C, and the suspension was kept at this temperature for 1 h.
The whole mixture was allowed to warm and then stirred for
1 h at 23 °C. After addition of 2.0 mL of water and evaporation
of solvent, the remaining solid was suspended in water and
extracted with 1,2-dichloroethane. The organic layer was
washed with brine and dried over Na2SO4. A yellowish brown
solid containing (S)-2,2′-bis[2,2-bis(4-dimethylaminophenyl)-
2-hydroxyethyl]binaphthyl (2.79 g) was obtained by evapora-
tion of solvent, which was directly used for the further
transformation. Dehydration was carried out by passing a
solution of crude diol in benzene through a SiO2 column.
Reprecipitaion from benzene solution by adding methanol at
23 °C gave (P)-3 (285 mg) as a yellow solid in 24% yield over
two steps from (P)-2,2′-dimethylbinaphthyl. Similarly, (R)-2,2′-
dimethylbinaphthyl was transformed into (M)-3 in 31% yield.
Data for (P)-3: mp 178-190 °C dec; 1H NMR (300 MHz,
Oxid a tion of Diolefin 1 to Dica tion Sa lt 22+(I3-)2. To a
solution of diolefin 1 (50 mg, 73 µmol) in dry CH2Cl2 (10 mL)
was added iodine (56 mg, 0.22 mmol) under Ar, and the
mixture was stirred overnight at 23 °C. Addition of dry ether
(5 mL) and removal by filtration of dark brown powder gave
dication salt 22+(I3-)2 in 98% yield. Data for 22+(I3-)2: mp 128-
1
139 °C dec; H NMR (300 MHz, CD3CN) δ/ppm 8.09 (2H, dd,
J ) 7.8, 1.2 Hz), 7.50 (2H, ddd, J ) 7.8, 7.8, 1.2 Hz), 7.34-
7.16 (8H, br AA′XX′), 7.25 (2H, ddd, J ) 7.8, 7.8, 1.2 Hz), 6.90
(2H, dd, J ) 7.8, 1.2 Hz), 6.72 (8H, br AA′XX′), 3.27 (12H, br
s), 3.17 (12H, br s); IR (KBr) 1584, 1408, 1376, 1166 cm-1; FD-
MS m/z 682 (M+, BP), 341 (M2+); UV-vis (CH3CN) λmax 588
(log ꢀ 4.98), 418 sh (4.34), 365 (4.66), 292 (4.96) nm. Anal. Calcd
for C48H50N4I6‚CH2Cl2: C, 38.48; H, 3.43; N, 3.66. Found: C,
38.20; H, 3.40; N, 3.30.
Red u ction of Dica tion Sa lt 22+(I3-)2 to Diolefin 1. To a
-
suspension of 22+(I3
) (30 mg, 21 µmol) in CH3CN (20 mL)
2
was added Zn powder (14 mg, 0.21 mmol), and the mixture
was stirred overnight at 23 °C. The mixture was diluted with
water and extracted with benzene. The organic layer was
washed with brine and dried over Na2SO4. Evaporation of
solvent gave a yellow solid of diolefin 1 (14 mg) in quantitative
yield.
CDCl3) is identical with that for rac-3; [R]25 -1048 (c 0.92 in
D
CH3CN); CD (CH3CN) λ 404 (∆ꢀ +44), 357 (-83), 307 (-44),
293 (-41), 262 (+27), 231 (-70), 213 (-78) nm. Data for (M)-
3: mp 177-185 °C dec; 1H NMR (300 MHz, CDCl3) is identical
P r ep a r a t ion of R a cem ic 2,2′-Bis[2,2-b is(4-d im et h yl-
a m in op h en yl)eth en yl]bin a p h th yl (r a c-3). To a solution of
rac-2,2′-dimethylbinaphthyl (600 mg, 2.1 mmol) in dry TMEDA
(660 µL) was added dropwise n-BuLi (1.57 mol dm-3 in
n-hexane, 2.80 mL, 4.4 mol) at 23 °C under Ar, and the mixture
was stirred for 1 h at 80 °C. Then, to the resultant suspension
of 2,2′-bis(lithiomethyl)binaphthyl was added a suspension of
4,4′-bis(dimethylamino)benzophenone (1.14 g, 4.6 mmol) in dry
THF (15 mL) at -15 °C, and the suspension was kept at this
temperature for 1 h. The whole mixture was allowed to warm
and then stirred for 1 h at 23 °C. After addition of 1.0 mL of
water and evaporation of solvent, the remaining solid was
suspended in water and extracted with 1,2-dichloroethane. The
organic layer was washed with brine and dried over Na2SO4.
A yellow solid containing rac-2,2′-bis[2,2-bis(4-dimethylami-
nophenyl)-2-hydroxyethyl]binaphthyl (1.89 g) was obtained by
evaporation of solvent, which was directly used for the further
transformation.
with that for rac-3; [R]25 -1024 (c 0.81 in CH3CN); CD (CH3-
D
CN) λ 404 (∆ꢀ -41), 355 (+81), 309 (+42), 294 (+40), 262 (-26),
231 (+71), 212 (+75) nm.
Oxid a tion of Diolefin 3 to Dica tion Sa lt 42+(I3-)2. To a
solution of diolefin rac-3 (50 mg, 64 µmol) in dry CH2Cl2 (20
mL) was added iodine (54 mg, 0.21 mmol) under Ar, and the
mixture was stirred overnight at 23 °C. Addition of dry ether
(10 mL) and removal by filtration of dark brown powder gave
dication salt rac-42+(I3-)2 in 95% yield. Similarly, (P)- and (M)-3
were transformed into (P)- and (M)-42+(I3-)2, respectively, in
95% and 95% yield. Data for rac-42+(I3-)2: mp 218 °C dec; 1H
NMR (300 MHz, CD3CN) δ/ppm 8.03 (2H, d, J ) 8.1 Hz), 7.92
(2H, d, J ) 8.6 Hz), 7.56 (2H, ddd, J ) 8.1, 6.7, 1.2 Hz), 7.52
(2H, d, J ) 8.6 Hz), 7.45 (4H, AA′XX′), 7.37 (2H, ddd, J ) 8.1,
6.7, 1.2 Hz), 7.18 (2H, d, J ) 8.1 Hz), 7.03 (4H, AA′XX′), 6.79
(4H, AA′XX′), 6.63 (4H, AA′XX′), 5.73 (2H, s), 3.31 (12H, s),
3.01 (12H, s); IR (KBr) 1580, 1406, 1378, 1194, 1168 cm-1; FD-
MS m/z 782 (M+, BP), 783 (M+ + 1), 342 (M2+); UV-vis (CH3-
CN) λmax 588 (log ꢀ 5.04), 411 sh (4.52), 358 (4.85), 293 (5.11),
241 (4.77), 221 (5.10) nm. Anal. Calcd for C48H50N4I6‚0.5CH2-
Cl2: C, 42.76; H, 3.49; N, 3.57. Found: C, 42.84; H, 3.56; N,
3.49. Data for (P)-42+(I3-)2: mp 152-161 °C dec; 1H NMR (300
MHz, CD3CN) is identical with that of rac-42+(I3-)2; CD (CH3-
CN) λ 658 (∆ꢀ +19), 584 (+35), 422 (+20), 389 (-14), 337 (-22),
256 (+207), 236 (-20), 227 (+57), 220 (-216) nm. Data for
To a solution of crude diol in benzene (50 mL) was added a
catalytic amount of TsOH (10 mg). After the mixture was
refluxed for 4 h under dehydrating conditions (Dean-Stark),
evaporation of solvent and chromatographic separation on
Al2O3 (benzene) gave rac-3 (1.05 g) as a yellow solid in 63%
yield over two steps from rac-2,2′-dimethylbinaphthyl. An
analytical sample was obtained by recrystallization from
1
benzene. Data for rac-3: mp 275-280 °C dec; H NMR (300
1
(M)-42+(I3-)2: mp 152-160 °C dec; H NMR (300 MHz, CD3-
MHz, CDCl3) δ/ppm 7.74 (2H, d, J ) 7.8 Hz), 7.47 (2H, d, J )
8.7 Hz), 7.35 (2H, ddd, J ) 7.8, 7.8, 1.5 Hz), 7.19 (2H, ddd, J
) 7.8, 7.8, 1.5 Hz), 7.15 (2H, d, J ) 8.7 Hz), 7.12 (2H, d, J )
7.8 Hz), 7.03 (4H, AA′XX′), 7.01 (4H, AA′XX′), 6.53 (4H,
AA′XX′), 6.28 (2H, s), 6.22 (4H, AA′XX′), 2.89 (12H, s), 2.83
(12H, s); IR (KBr) 1610, 1520, 1352, 824 cm-1; FD-MS m/z 782
(M+, BP), 783 (M+ + 1); UV-vis (CH3CN) λmax 352 sh (log ꢀ
4.55), 330 (4.56), 260 (4.82), 207 (5.04) nm. Anal. Calcd for
CN) is identical with that of rac-42+(I3-)2; CD (CH3CN) λ 656
(∆ꢀ -18), 585 (-32), 424 (-20), 388 (+15), 338 (+24), 256
(-206), 236 (+22), 227 (-51), 220 (+218) nm.
Red u ction of Dica tion Sa lt 42+(I3-)2 to Diolefin 3. To a
suspension of rac-42+(I3-)2 (50 mg, 32 µmol) in CH3CN (20 mL)
was added Zn powder (21 mg, 0.32 mmol), and the mixture
was stirred overnight at 23 °C. The mixture was diluted with
water and extracted with benzene. The organic layer was
washed with brine and dried over Na2SO4. Evaporation of
solvent gave a yellow solid of diolefin 3 (25 mg) in quantitative
yield. Similarly, (P)- and (M)-42+(I3-)2 were transformed into
(P)- and (M)-3, respectively, in 98% and 95% yield.
C
56H54N4: C, 85.90; H, 6.95; N, 7.16. Found: C, 86.16; H, 7.20;
N, 6.86.
P r ep a r a tion of Ch ir a l 2,2′-Bis[2,2-bis(4-d im eth yla m i-
n op h en yl)eth en yl]bin a p h th yl ((P )- a n d (M)-3). Chiral (P)-
and (M)-3 were obtained from (S)- and (R)-2,2′-dimethylbi-
naphthyl by the similar procedure to rac-3 in 72% and 87%
yield, respectively. To confirm that the heat treatment in the
above procedure induces no racemization of the products and
synthetic intermediates, lithiation and dehydration processes
were conducted below room temperature in other experiments
as follows. The resulting products exhibit the identical optical
activities to those obtained through the heated processes.
Red ox P oten tia l Mea su r em en ts. Redox potentials (Eox
and Ered) were measured by cyclic voltammetry in dry MeCN
containing 0.1 mol dm-3 Et4NClO4 as a supporting electrolyte.
Ferrocene undergoes 1e-oxidation at +0.38 V under the same
conditions. All of the values shown in the text are in E/V vs
SCE. All the voltammograms are irreversible because of the
redox switching of single bonds, and the half-wave potentials
J . Org. Chem, Vol. 68, No. 17, 2003 6609