9252 J . Org. Chem., Vol. 64, No. 25, 1999
Notes
Sch em e 2. P r ep a r a tion of cis- a n d tr a n s-1,2-Dip h en oxyeth en e a n d Th eir p,p′-Dim eth yl Der iva tives
7.52 (dd, 4H, J ) 8.95, 1.25); 13C NMR (250 MHz, CDCl3) δ 84.80,
117.57, 119.16, 132.91, 154.76; HRMS calcd for C14H10O2Br4
525.741 424, found 525.740 938.
Sch em e 3. P a r tia lly An ti Ster eosp ecific Ad d ition
of Br om in e to 1,2-Dia r yloxyeth en es
cis-1,2-Bis(4-b r om op h en oxy)et h en e (cis-3). The dl dia-
stereoisomer of 2 (0.54 g, 1.02 mmol) was dissolved in 20 mL of
acetone. Sodium iodide (0.45 g, 3 mmol) was then added to this
solution. The reaction mixture was stirred for 2 h at room
temperature, during which time a deep red color developed. After
the acetone solvent had been removed by rotary evaporation,
water (25 mL) and dichloromethane (100 mL) were added, and
a saturated aqueous solution of sodium thiosulfate was added
until the solution was colorless. The organic layer was then
separated, evaporated, dried, filtered to get a small amount of
a solid, and recrystallized ethanol to obtain cis-3 (0.35 g, 95%).
Similarly, 0.537 g (1 mmol) of meso-2 was dissolved in ethanol-
water (40 mL, 30:10), and 0.072 g (1.1 mmol) of zinc powder
was added. The resulting reaction mixture was stirred and
refluxed for 3 h. After rotary evaporation of the solvents, cis-3
(0.18 g, 49%) was obtained by silica gel chromatography (hex-
anes/dichloromethane 10:1): mp 102-104 °C; 1H NMR (500
MHz, CDCl3) δ 6.11 (s, 2H, J (HCdCH) ) 3.42 Hz), 6.96 (d, 4H,
J ) 9.04 Hz), 7.42 (d, 4H, J ) 9.04 Hz); 13C NMR (250 MHz,
CDCl3) δ 115.40, 117.94, 128.46, 132.54, 156.30; LRMS m/e 368
(M+), 370, 372, 198, 196, 155, 153, 118, 76; HRMS calcd for
C14H10O2Br2 367.904 752, found 367.905 142.
tr a n s-1,2-Bis(4-br om op h en oxy)eth a n e (tr a n s-3). In the
same manner as described for cis-3, trans-3 could be obtained
by zinc debromination of meso-2 (60% yield) or by the iodide ion
induced debromination of dl-2 (98%): mp 113-114 °C; 1H NMR
(500 MHz, CDCl3) δ 6.81 (s, 2H), 6.90 (d, 4H, J ) 8.95 Hz), 7.42
(d, 4H, J ) 8.95 Hz, J (HCdCH) ) 13.44 Hz); 13C NMR C 250
MHz, CDCl3 δ 115.22, 117.53, 132.59, 134.79, 156.59; LRMS m/e
368 (M+) 0.370, 372, 157, 155, 118, 97, 76; HRMS calcd for
C14H10O2Br2 367.904 57, found 367.905 698.
Exp er im en ta l Section
An a lysis. Routine 1H and 13C NMR spectra were recorded
as solutions in CDCl3.
Rea gen ts. Organic chemicals used as starting materials in
these syntheses were used as received from the Aldrich Co.
These included 4-bromophenol, 1,2-dibromoethane, and N-
bromosuccinimide.
1,2-Bis(4-br om op h en oxy)eth a n e (1). To a solution of so-
dium hydroxide (12.4 g, 0.31 mol) in water (50 mL) was added
4-bromophenol (51.7 g, 0.3 mol). The mixture was stirred at 60-
70 °C for 0.5 h prior to the addition of 1,2-dibromoethane (26.3
g, 0.14 mol). The resulting mixture was then heated at reflux
for 6 h. After being cooled to room temperature, the reaction
mixture was filtered to obtain a white solid, which was recrys-
tallized from ethanol and dried in vacuo. The yield of pure 1
was 32.7 g (56.7%): mp 130-132 °C; 1H NMR (250 MHz, CDCl3)
δ 4.25 (s, 4H), 6.81 (d, 4H, J ) 6.85 Hz), 7.37 (d, 4H, J ) 6.85
Hz); 13C NMR (250 MHz, CDCl3) δ 66.68, 113.41, 116.48, 132.33,
157.45; LRMS m/e 370 (M+), 372, 374, 199, 197, 157, 155; HRMS
calcd for C14H13O2Br2 370.928 227, found 370.927 493.
m eso- a n d d l-1,2-Dib r om o-1,2-b is(4-b r om op h en oxy)-
eth a n e (m eso-2 a n d d l-2). In 50 mL of carbon tetrachloride
was dissolved 3.37 g (9.06 mmol) 1, 3.95 g (22.19 mmol) of
N-bromosuccinimide, and 0.54 g (2.23 mmol) of benzoyl peroxide.
The resulting solution was heated at reflux for 6 h. After being
cooled to room temperature, the mixture was filtered and the
crude products obtained from the filtrate by evaporating the
solvent. Silica gel chromatography (230-400 mesh; 6:1 hexane/
dichloromethane) yielded pure meso- and dl-2. The isolated yield
of pure meso-2 was 0.82 g (17.1%). meso-2b: mp 140-142 °C;
1H NMR (CDCl3, 500 MHz) δ 6.51 (s, 2H, J ) 6.2 Hz), 7.08 (dd,
4H, J ) 8.95, 1.25 Hz); 7.51 (dd, 4H, J ) 8.95, 1.25 Hz); 13C
NMR (250 MHz, CDCl3) δ 85.31, 116.97, 118.87, 132.89, 153.72;
HRMS calcd for C14H10O2Br4 525.741424, found 525.741353.The
tr a n s-1,2-Dip h en oxyeth en e (tr a n s-4). A solution of trans-3
(1.22 g, 3.31 mmol) in anhydrous diethyl ether (20 mL) in an
atmosphere of nitrogen was cooled to ca. -15 °C. A solution of
butyllithium in hexanes (6.62 mL of 1.6 M solution, 10.6 mmol)
was then added to the cold solution, and the mixture was stirred
for 20 min at that temperature. Water (5 mL) was added, and
the organic products were then extracted with dichloromethane.
The crude product was chromatographed on silica gel to yield
0.63 g (90%) of pure trans-4: mp 78-79 °C; 1H NMR (250 MHz,
CDCl3) δ 6.82 (s, 2H, vinyl protons), 7.00-7.05 (m, 6H), 7.24-
7.36 (m, 4H); 13C NMR (250 MHz, CDCl3) δ 115.75, 122.64,
129.67, 134.80, 157.58; LRMS m/e 212 (M+), 155, 153, 118, 91,
77, 65 (w), 51; HRMS calcd for C14H12O2 212.083 730; found
212.084 289.
cis-1,2-Dip h en oxyeth en e (cis-4). This cis isomer was ob-
tained from cis-3 by the same procedure as described above (95%
yield): mp 64-66 °C; 1H NMR (250 MHz, CDCl3) δ 6.15 (s, 2H,
vinyl protons), 7.05-7.11 (m, 6H), 7.29-7.35 (m, 4H); 13C NMR
(250 MHz, CDCl3) δ 116.26, 122.85, 128.38, 129.61, 157.01;
LRMS m/ e 212 (M+), 182, 155, 135, 118, 91, 77, 65 (s), 51; HRMS
calcd for C14H12O2 212.083 730, found 212.084 289.
tr a n s-1,2-Bis(4-m eth ylp h en oxy)eth en e (tr a n s-5). This
derivative was obtained in the same manner as trans-4 from
trans-3 by quenching the lithio derivatives with excess methyl
iodide instead of water (>90% yield): mp 66-68 °C; 1H NMR
(250 MHz, CDCl3) δ 2.30 (s, 6 H), 6.81 (s, 2H, vinyl protons),
6.91 (m, 2H), 6.93 (m,2H), 7.10 (m, 2H), 7.13 (m, 2H); 13C NMR
(250 MHz, CDCl3) δ 20.54, 115.61, 130.07, 131.98, 134.71,
1
yield of dl-2 was 0.62 g (13%): mp 118-120 °C; H NMR (500
MHz, CDCl3) δ 6.48 (s, 2H, J ) 1.8), 7.14 (dd, 4H, J ) 8.95,1.25),