2812 J . Org. Chem., Vol. 61, No. 8, 1996
Matsumura et al.
solution was quenched with saturated aqueous NH4Cl solution
and extracted with CH2Cl2. The extract was dried on MgSO4,
and the solvent was evaporated in vacuo to give a residue.
The residue was subjected to column chromatography (Merck
silica gel 60, 70-230 mesh) with hexane/AcOEt (5/1) to give
dl-6a , meso-6a , and 7.
d l-6b: mp 49-54 °C; IR (KBr) 3060, 3040, 2945, 1725, 1600,
1495, 1455, 1370, 1300, 1240, 1160, 985, 940, 735, 700, 570
cm-1; 1H NMR (CDCl3) δ 4.29 (s, 1H), 4.55-4.65 (m, 2H), 5.10-
5.28 (m, 2H), 5.73-5.95 (m, 1H), 6.95-7.20 (m, 5H); MS 352,
336, 292, 280, 264, 251, 223, 207, 193, 180, 165, 149, 147, 129,
119, 105, 91, 83, 69, 57.
d l-6a : 13.5%.
Anal. Calcd for C22H22O4: C, 75.41; H, 6.33. Found: C,
75.29; H, 6.41.
m eso-6a : 4.5%; sublimation temperature 174-179 °C (lit.14
mp 218-219 °C); IR (KBr) 2960, 1730, 1500, 1455, 1435, 1300,
1150, 995, 880, 733, 700 cm-1; 1H NMR (CDCl3) δ 3.40 (s, 3H),
4.40 (s, 1H), 7.25-7.42 (m, 3H), 7.43-7.53 (m, 2H); MS 298,
266, 238, 179, 165, 149 (P), 135, 121 102, 96, 91, 85, 77, 57.
Anal. Calcd for C18H18O4: C, 72.46; H, 6.08. Found: C,
72.05; H, 6.13.
P r ep a r a tion of d l- a n d m eso-2,3-Dim eth yl-2,3-d ip h en -
ylsu ccin ic Acid Dim eth yl Ester (6c). To a solution of
methyl R-methylphenylacetate (5c) (2 mmol, 0.33 g) in CH2-
Cl2 (10 mL) was added TiCl4 (10.0 mmol, 1.10 mL) with a
syringe at -45 °C, and the solution was stirred for 30 min.
Triethylamine (10.0 mmol, 1.40 mL) was then added, and the
solution was stirred at -45 °C for 1.5 h. The solution was
quenched with a saturated aqueous NH4Cl solution and
extracted with CH2Cl2. The extract was dried on MgSO4, and
the solvent was evaporated in vacuo to give a white solid. The
solid was subjected to column chromatography with CH2Cl2
to give a mixture of dl- and meso-2,3-dimethyl-2,3-diphenyl-
succinic acid dimethyl ester (6c) in 87% yield. dl- and meso-
6c are known compounds,11 and the dl/meso ratio was deter-
mined by NMR. R,p-Coupling product 8 was not observed in
this reaction. The authentic sample of 8 was prepared as
previously reported.2 The spectroscopic (IR and 1H NMR
spectra) data of 8 were as follows.
7: 50%; mp 58-60 °C; IR (KBr) 3480, 3140, 2950, 1745,
1720, 1500, 1460, 1435, 1220, 1165, 1060, 715, 700, 550 cm-1
;
1H NMR (CDCl3) δ 3.43 (s, 0.66H), 3.67 (s, 0.99H), 3.69 (d, J
) 16 Hz, 0.67H), 3.71 (s, 2.01H), 3.78 (d, J ) 16 Hz, 0.67H),
4.81 (s, 0.67H), 7.05-7.43 (m, 10H), 13.05 (s, 0.33H); MS 268,
236, 209, 191, 177, 165, 150, 145, 136, 116, 105, 91(P), 77, 65.
Anal. Calcd for C17H16O3: C, 76.10; H, 6.01. Found: C,
76.01; H, 6.08.
P r ep a r a tion of d l-2,3-Dip h en ylsu ccin ic Acid Dia llyl
Ester (d l-6b). To a solution of allyl phenylacetate (5b) (2
mmol, 0.35 g) in CH2Cl2 (10 mL) was added TiCl4 (4.4 mmol,
0.48 mL) with a syringe at -45 °C, and the solution was stirred
for 30 min. Triethylamine (4.4 mmol, 0.61 mL) was then
added, and the solution was stirred at -45 °C for 1.5 h. The
solution was quenched with a saturated aqueous NH4Cl
solution and extracted with CH2Cl2. The extract was dried
on MgSO4, and the solvent was evaporated in vacuo to give a
white solid. The solid was subjected to column chromatogra-
phy with hexane/AcOEt (10/1) to give pure dl-6b in 80% yield.
Under these reaction conditions, the meso-isomer and the
Claisen condensation product were not observed. The stereo-
chemistry of dl-6b was determined by its conversion to dl-6a :
i.e., heating of dl-6b in methanol containing NaOMe at reflux
temperature for 7 h followed by acidifying the resulting
solution to give the corresponding diacid, which was trans-
formed to dl-6a by heating in methanol containing hydrogen
chloride.
8: IR (KBr) 2988, 2951, 1728, 1599, 1495, 1433, 1240, 1167,
1080, 700 cm-1 1H NMR (CDCl3) δ 1.48 (d, J ) 7.1 Hz, 3H),
.
1.90 (s, 3H), 3.63 (s, 3H), 3.67 (m, 1H), 3.69 (s, 3H), 6.81-7.32
(m, 9H).
Oxid a tive Cou p lin g of 5a a n d 5c by Meth od s i a n d ii.
Oxidative coupling by methods i and ii was carried out by the
procedures described in the literature.2,3a
Ack n ow led gm en t. This work was supported in part
by a Grant-in-Aid for Scientific Research on Priority
Areas (No. 236) and for Scientific Research (No.
07672272) from the Ministry of Education, Science and
Culture, J apan.
J O952204H