Mg-Promoted Regioselective Cross-Coupling of Stilbene Derivatives with Carbonyl Compounds

Article abstract of DOI:10.1055/s-2003-44970

Treatment of stilbene derivatives with aliphatic carbonyl compounds in the presence of trimethylsilyl chloride (TMSCl) and Mg metal in N,N- dimethylformamide (DMF) at room temperature brought about regioselective cross-coupling to give the corresponding phenethyl alcohols in moderate to good yields. These reactions may be initiated through one-electron transfer from Mg metal to the carbon-carbon double bond of stilbene derivatives to give the corresponding anion radical species, which were subjected to electrophilic attack of aliphatic carbonyl compounds followed by fast second electron transfer generating the corresponding α-benzyl anions.

Full text of DOI:10.1055/s-2003-44970

30
LETTER
Mg-Promoted Regioselective Cross-Coupling of Stilbene Derivatives with
Carbonyl Compounds
M
g-Promote
d
Re
g
o
ioselective
C
s
ross-Cou
h
pling imasa Yamamoto, Seiji Kawano, Hirofumi Maekawa, Ikuzo Nishiguchi*
Department of Chemistry, Nagaoka University of Technology, 1603-1, Kamitomioka-cho, Nagaoka, Niigata 940-2188, Japan
Fax +81(2)589300; E-mail: nishiiku@vos.nagaokaut.ac.jp
Received 22 October 2003
vent such as HMPA, a metal on treatment with special
Abstract: Treatment of stilbene derivatives with aliphatic carbonyl
cautions or an expensive reagent.
compounds in the presence of trimethylsilyl chloride (TMSCl) and
Mg metal in N,N-dimethylformamide (DMF) at room temperature
brought about regioselective cross-coupling to give the correspond-
ing phenethyl alcohols in moderate to good yields. These reactions
may be initiated through one-electron transfer from Mg metal to the
carbon–carbon double bond of stilbene derivatives to give the cor-
responding anion radical species, which were subjected to electro-
philic attack of aliphatic carbonyl compounds followed by fast
second electron transfer generating the corresponding a-benzyl
anions.
In this study, we wish to report Mg-promoted regioselec-
tive cross-coupling of stilbenes with aliphatic carbonyl
compounds in the presence of TMSCl to give the corre-
sponding phenethyl alcohols at room temperature
(Scheme 1). Mg metal10 is usually safe, harmless, conve-
nient to treat, easily available, and environmentally
friendly since it can be seen in many natural compounds.
OH
Key words: electron transfer, reductions, magnesium,, cross-cou-
pling, regioselectivity
R2
H3O+
R1
Mg / TMSCl
DMF
R1=R2=H, Alkyl
R3=Alkyl
R3
Ar
R2COR3
+
Ar
Ar
R1
Ar
Cross-coupling of olefins with carbonyl compounds such
as ketones or aldehydes may be one of the most attractive,
important and useful techniques for carbon–carbon bond
formation to prepare the corresponding coupled alcohols.
Thus, it have been reported that Lewis acid-catalyzed car-
bonyl-ene reaction of olefins with carbonyl compounds
brought about carbon–carbon bond formation to afford
the corresponding b-hydroxy olefins. However, the usual
olefins only react with active carbonyl compounds such as
formaldehyde,1 glyoxylates,2 a-aminoaldehydes3 and a-
alkoxyaldehydes.4
Scheme 1 Mg-promoted cross-coupling of stilbenes with aliphatic
carbonyl compounds
Mg-promoted reductive cross-coupling took place quite
smoothly by treatment of stilbene derivatives 1 with Mg
turnings in the presence of a large excess of aliphatic car-
bonyl compounds 211 and TMSCl in DMF at 15–20 °C,
followed by acid-catalyzed hydrolysis with 1% HCl
aqueous–EtOH solution, giving the corresponding phen-
ethyl alcohols 3 in moderate to good yields, as shown in
Table 1.12 Besides the cross-coupling products, small
amounts of the C-silylated product 5 and the simply re-
duced product 6 were obtained as the by-products. In-
crease in the carbon number of aliphatic carbonyl
compounds 2 led to decrease in the yield of the product 3,
possibly because of steric hindrance.
On the other hand, electron transfer reaction may provide
other useful methods for this cross-coupling of olefins
with carbonyl compounds. For example, we have already
reported facile and selective Mg-promoted cross-coupling
of a,b-unsaturated carbonyl or phosphorus compounds
with aliphatic aldehydes, acid anhydrides or acid chlo-
rides in the presence of TMSCl to form the regioselective
carbon–carbon bond.5
It may be quite interesting that in the coupling of a-meth-
ylstilbene (1b)13 with acetone (2a) and isobutyraldehyde
(2k), the carbon–carbon bond was regioselectively
formed between the carbonyl carbon of 2 and the sterical-
ly hindered a-carbon of 1b to give exclusively the coupled
alcohols 3l and 3m, respectively, although the consump-
tion of 1b was considerably low (entries 12 and 13).
Furthermore, electroreductive carbon–carbon bond for-
mation between carbonyl groups and olefinic groups has
been also shown to bring about highly selective intra- and
intermolecular cross-coupling by us6 and other groups.7
Although cross-coupling of carbonyl compounds with
8
olefins in the presence of SmI2 or alkali metal9 has been
Furthermore, the present reductive cross-coupling of
acenaphthylene (7a) with aliphatic aldehydes 2 also pro-
ceeded smoothly under the similar conditions to give the
corresponding cross-coupling alcohols 8 as the main
products, as shown in Table 2. The use of 1-methyl-
acenaphthylene (7b)14 in this coupling also led to regio-
selective carbo–carbon bond formation at the more
sterically hindered carbon atom of 7b (entry 4).
reported as another example of the electron transfer reac-
tions, these reactions generally require a carcinogenic sol-
SYNLETT 2004, No. 1, pp 0030–0036
0
5.
0
1.
2
0
0
4
Advanced online publication: 4.12.2003
DOI: 10.1055/s-2003-44970; Art ID: U21903ST
© Georg Thieme Verlag Stuttgart · New York

LETTER
Mg-Promoted Regioselective Cross-Coupling
31
Table 1 Mg-Promoted Cross-Coupling of Stilbenes with Aliphatic Carbonyl Compoundsa
R2 OH
R3
R2 OTMS
R2 OH
R3
R1
Mg / TMSCl
DMF
R3
Ph
1% HCl aq.
EtOH
R2COR3
+
+
+
Ph
Ph
Ph
Ph
Ph
R1
Ph
Ph
R1
R1
3
2
1
3
4
R1
TMS
Ph
+
Ph
R1
Ph
Ph
5
6
Entry
R1 (1)
R2 (2)
R3 (2)
Conv. (%)
Yield (%)b
3
5
6
1
2
H (1a)
H (1a)
H (1a)
H (1a)
H (1a)
H (1a)
H (1a)
H (1a)
H (1a)
H (1a)
H (1a)
Me (1b)
Me (1b)
Me
Et
Me (2a)
Et (2b)
100
100
100
100
100
100
94
3a (70)
3b (50)
3c (56)
3d (68)
3e (62)
3f (62)
trace
5
7
14
11
3
3
–(CH2)4– (2c)
–(CH2)5– (2d)
2
4
3
5
Et
Me (2e)
Trace
2
7
6
n-Pr
i-Pr
i-Bu
n-Pr
n-Bu
i-Pr
Me
Me (2f)
Me (2g)
Me (2h)
H (2i)
10
11
19
2
7
3g (47)
3h (58)
3i (66)
4
8
94
trace
trace
trace
trace
–
9c
10c
11c
12c
13c
100
100
100
39
H (2j)
3j (57)
trace
2
H (2k)
Me (2a)
H (2k)
3k (52)
3l (22) (56)d
3m (13) (50)d
–
i-Pr
26
–
–
a Reaction conditions: Substrate (10 mmol), carbonyl compounds (10 equiv mol), TMSCl (2 equiv mol), Mg (4 equiv mol), DMF (60 mL),
temp. 15–20 °C, reaction time 15 h, under N2 atmosphere.
b GC Yield.
c TMSCl (5 equiv mol).
d Yield based on the consumed starting compound.
Interestingly, the cross-coupling of acenaphthylene (7a) stilbene 1a with acetophenone (2m) brought about quan-
with acetophenone (2m) gave the corresponding product titative recovery of 1a and the pinacol dimer of 2m was
8e in a 47% yield accompanying some formation of the obtained as the by-product. This fact may indicate that the
pinacol dimer as the by-product (entry 5). However, the present cross-coupling requires the activation of stilbenes
reaction of stilbene 1a with 2m under the similar condi- 1 or acenaphthylenes 7 to generate the corresponding
tions resulted in quantitative recovery of 1a. This sharp anionic species prior to that of carbonyl compounds.
contrast may indicate that 7a is more active than 1a for
electron transfer by Mg metal.
From these experimental results, the following reaction
scheme may be proposed as one of the most plausible
The reduction potentials of stilbenes 1, acenaphthylenes mechanisms although the detailed mechanistic studies
7, carbonyl compounds 2 and TMSCl were measured by have not been conducted as yet. The reaction may be
cyclic voltammetry, and the results were shown in initiated through the first one-electron transfer from Mg
Table 3. These results indicate that TMSCl (no reduction metal, activated by TMSCl, to stilbenes 1 to give the
peak up to –3.00 V vs Ag/AgCl) and aliphatic carbonyl corresponding anion radical species 9 which may be sub-
compounds (2e: no peak up to –3.00 V, 2i: –2.93 V) are jected to the electrophilic attack of carbonyl compounds 2
quite difficult to reduce by Mg metal while stilbenes (1a: in a regioselective manner, followed by the fast second
–2.35 V, 1b: –2.49 V) and acenaphthylenes (7a: –1.73 V, one-electron transfer.15 Thus, the benzylic anions 10
7b: –2.12 V) are adequately accessible to reduce. Because generated may be preferentially subjected to protonation
stilbene 1a has a more negative reduction potential than to afford the corresponding final products 3 rather than
that of acetophenone (2m: –2.05 V), the cross-coupling of second electrophilic attack of 2, possibly because of steric
Synlett 2004, No. 1, 30–36 © Thieme Stuttgart · New York

32
Y. Yamamoto et al.
LETTER
Table 2 Mg-Promoted Cross-Coupling of Acenaphthylenes with
from the a-methylstilbene (1b) and 1-methylacenaphthyl-
ene (7b) were controlled by preferential stability of the
carbanions 10 to the carbanions 11, which were generated
from the very fast or almost concerted second one-elec-
tron transfer, rather than by distribution of electron densi-
ty in the anion radical species 9 (Scheme 2).16
Consequently, 3l, 3m and 8d were obtained as the only
products.
Carbonyl Compoundsa
OH
R2
R1
R3
R1
Mg / TMSCl
DMF
1% HCl aq.
EtOH
R2COR3
+
2
7
8
Entry
R1 (7)
R2 (2)
Et
R3 (2)
Yield (%)b
8a (49)
8b (69)
8c (69)
8d (52)
8e (47)
OH
R2
H3O+
R1
Mg / TMSCl
DMF
1
H (7a)
H (7a)
H (7a)
Me (7b)
H (7a)
H (2l)
R3
R2COR3
+
Ar
Ar
Ar
R1
Ar
2
n-Pr
i-Pr
n-Pr
Ph
H (2i)
2
1
3
3
H (2k)
H (2i)
H3O+
4
TMSCl (or H+)
H+
Mg (+e)
5c
Me (2m)
a Reaction conditions: Substrate (10 mmol), carbonyl compounds (10
equiv mol), TMSCl (5 equiv mol), Mg (4 equiv mol), DMF (60 mL),
–5 °C to –10 °C, 3 h., under N2 atmosphere.
b GC Yield.
R3
R2
O
R1
Mg2+
Ar
R2COR3, Mg (+e)
Ar
c TMSCl (0.5 equiv mol), Mg (7 equiv mol).
Ar
Ar
R1
9
10
R2COR3, Mg (+e)
Table 3 Reduction Potentials of Activated Olefins and Carbonyl
Compoundsa
R1
R1
TMSCl
(or H+)
Ar
Ar
H3O+
Substrate
Reduction Potentials (V vs. Ag/
AgCl)
Ar
Mg2+
H+
Ar
R2
HO
R2
R3
3
O
R
–2.35
Ph
12
11
Ph
(1a)
–2.49
Scheme 2 Proposed reaction mechanism of regioselective cross-
coupling
Ph
Ph
(1b)
–1.73
–2.12
In addition to a little formation of the aldol type of dimers,
such as mesityl oxide, from aliphatic carbonyl compounds
as the by-products, the corresponding deuterated product
3a¢ was obtained on the use of acetone-d6 (2a¢) instead of
acetone in this cross-coupling as shown in Scheme 3.
These facts distinctly indicate that a-protons of those car-
bonyl compounds acted as proton source on the present
reactions.
(7a)
(7b)
CH3CH2COCH3 (2e)
CH3CH2CH2CHO (2i)
PhCOMe (2m)
TMSCl
no wave (0–ca. 3.00)
–2.93
HO
CD3
H
CD3
CD3
Mg / TMSCl
DMF
CD3
Ph
Ph
+
O
Ph
Ph
1
H
D
2a'
–2.05
3a'
Deuterated ratio 79%
no wave (0–ca. 3.00)
a Working electrode: Pt, counter electrode: Pt, reference electrode:
Ag/AgCl, solvent: DMF, supporting electrolyte: (n-Bu)4NClO4, scan
rate: 200 mV/s.
Scheme 3 Mg-promoted cross-coupling of stilbene with acetone-d6
As one of the applications of these reactions, it was shown
that the cross-coupling of stilbene (1a) with levulinic acid
esters brought about a new carbon–carbon bond formation
followed by cyclization to give the corresponding g-lac-
tone derivatives 14. In this reaction, the anion radical spe-
cies generated from stilbene (1a) may be subjected to the
electrophilic attack of the keto group in the levulinic acid
esters, followed by the second one-electron transfer, to
hindrance and/or decrease in nucleophilicity of 10 where
the benzylic anion center may coordinate with Mg2+.
It may be proposed that the regioselective attack of carbo-
nyl compounds 2 on the anion radical species 9 generated
Synlett 2004, No. 1, 30–36 © Thieme Stuttgart · New York

LETTER
Mg-Promoted Regioselective Cross-Coupling
33
(5) (a) Ohno, T.; Ishino, Y.; Tsumagari, Y.; Nishiguchi, I. J.
generate the oxygen anionic species 13. Subsequent
intramolecular nucleophilic attack of the O-anion on the
ester group may give the corresponding g-lactones 14
(Scheme 4).
Org. Chem. 1995, 60, 458. (b) Nishiguchi, I.; Yamamoto,
Y.; Sakai, M.; Ohno, T.; Ishino, Y.; Maekawa, H. Synlett
2002, 759. (c) Ohno, T.; Sakai, M.; Ishino, Y.; Shibata, T.;
Maekawa, H.; Nishiguchi, I. Org. Lett. 2001, 3, 3439.
(d) Kyoda, M.; Yokoyama, T.; Maekawa, H.; Ohno, T.;
Nishiguchi, I. Synlett 2001, 1535.
O
H3O+
Ph
Ph
Mg / TMSCl
DMF
O
Ph
OR
+
(6) (a) Shono, T.; Nishiguchi, I.; Ohmizu, H.; Mitani, M. J. Am.
Chem. Soc. 1978, 100, 545. (b) Shono, T.; Nishiguchi, I.;
Omizu, H. Chem. Lett. 1976, 1233. (c) Nishiguchi, I.; Goda,
S.; Yamada, K.; Yamamoto, Y.; Maekawa, H. Chem. Lett.
2002, 1254. (d) Goda, S.; Yamada, K.; Yamamoto, Y.;
Maekawa, H.; Nishiguchi, I. J. Electroanal. Chem. 2003,
545, 129–140.
(7) (a) Kashimura, S.; Ishifume, M.; Murai, Y.; Shono, T.
Tetrahedron Lett. 1996, 37, 6737. (b) Kashimura, S.;
Ishifume, M.; Murai, Y.; Shono, T. Chem. Lett. 1996, 309.
(c) Shono, T.; Morishima, Y.; Moriyoshi, N.; Ishifune, M. J.
Org. Chem. 1994, 59, 273. (d) Kashimura, S.; Ishifune, M.;
Murai, Y.; Moriyoshi, N.; Shono, T. Tetrahedron Lett. 1995,
36, 5041. (e) Shono, T.; Kashimura, S.; Mori, Y.; Hayashi,
T.; Soejima, T.; Yamaguchi, Y. J. Org. Chem. 1989, 54,
6001. (f) Swartz, J. E.; Mahachi, T. J.; Kariv, M. E. J. Am.
Chem. Soc. 1988, 110, 3622. (g) Shono, T.; Mitani, M. J.
Am. Chem. Soc. 1971, 93, 5284. (h) Koizumi, T.;
Ph
O
O
1a
14
Ph
O
R=Me, Yield=50%
R=Et, Yield=54%
RO
Ph
O
13
Scheme 4 Mg-promoted cross-coupling of stilbene with levulinic
acid esters. Reaction Conditions: substrate (10 mmol), levulinic acid
esters (10 equiv mol), TMSCl (2 equiv mol), Mg (4 equiv mol), DMF
(60 mL), temp. 15–20 °C, reaction time 15 h, under N2 atmosphere
As a conclusion, the present Mg-promoted regioselective
cross-coupling of stilbene derivatives with aliphatic car-
bonyl compounds brought about new carbon–carbon
bond formation to give the corresponding b-benzyl phen-
ethyl alcohols in moderate to good yields. The present
method may be characterized by high regioselectivity,
simple procedure, unique reaction pattern, easy availabil-
ity of reagents (commercial Mg turning for Grignard reac-
tion can be used without any pretreatment) and mild
conditions (room temperature and ordinary pressure), and
may provide usefulness and significance in organic syn-
thesis.
Fuchigami, T.; Kandeel, Z. El. S.; Sato, N.; Nonaka, T. Bull.
Chem. Soc. Jpn. 1986, 59, 757.
(8) (a) Ujikawa, O.; Inanaga, J.; Yamaguchi, M. Tetrahedron
Lett. 1989, 30, 2837. (b) Fukuzawa, S.; Nakanishi, A.;
Fujinami, T.; Sakai, S. J. Chem. Soc., Chem. Commun. 1986,
624. (c) Molander, G. A.; McKie, J. A. J. Org. Chem. 1992,
57, 3132. (d) Molander, G. A. Chem. Rev. 1992, 92, 29.
(9) Kochi, J. K. J. Org. Chem. 1963, 28, 1960.
(10) Mg turnings for a Grignard reaction can be used without any
pre-treatment.
(11) The use of less than 10 equiv mol of acetone(2a) resulted in
decrease in the yield of phenethyl alcohols 3a accompanying
increase in formation of tarry material. Thus, the use of 3
equiv mol and 5 equiv mol of 2a provided 3a in 58% and
63% yields, respectively.
Acknowledgment
This work was financially supported by the 21st Century COE pro-
gram and a Grant-in-Aid for Scientific Research (No. 13029038)
from The Ministry of Education, Culture, Sports, Science and Tech-
nology, Japan.
(12) General Methods: Stilbene 1a, acenaphthylene (7a),
aliphatic carbonyl compounds 2, TMSCl, Mg and levulinic
acid esters were purchased from Aldrich Chemical Co. Ltd,
Tokyo Kasei Kogyo Co. Ltd or Nacalai Tesque Ltd, and
were used without further purification. The compound,
a-methylstilbene (1b) was prepared by the reaction of
benzylmagnesium chloride with benzaldehyde followed by
dehydration.13 The compound, 1-methylacenaphthylene
(7b) was prepared by the reported method.14 DMF was dried
on CaH2 and then was distilled under reduced pressure.
1H NMR and 13C NMR spectra were measured by a JEOL
JNM-EX-400 (400 MHz and 100 MHz) spectrometer or a
JEOL JNM-GX-270 (270 MHz and 67.8 MHz)
References
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Wolinsky, J. J. Am. Chem. Soc. 1957, 79, 4972.
(2) (a) Mikami, K.; Terada, M.; Nakai, T. J. Am. Chem. Soc.
1989, 111, 1940. (b) Mikami, K.; Loh, T.-P.; Nakai, T.
Tetrahedron Lett. 1988, 29, 6305. (c) Mikami, K.; Shimizu,
M.; Nakai, T. J. Org. Chem. 1991, 56, 2952. (d) Mikami,
K.; Loh, T.-P.; Nakai, T. J. Am. Chem. Soc. 1990, 112,
6737. (e) Whitesell, J. K. Acc. Chem. Res. 1985, 18, 280.
(f) Whitesell, J. K.; Bhattacharya, A.; Aguilar, D. A.; Henke,
K. J. Chem. Soc., Chem. Commun. 1982, 989.
(g) Achmatowicz, O.; Szechner, B. J. Org. Chem. 1972, 37,
964.
spectrometer, with TMS as an internal standard. IR spectra
were measured by a JASCO IR-810 spectrometer or JASCO
FT/IR-400 Plus spectrometer. Mass spectra were obtained
using a Shimadzu GC-MS QP-2000A or a JEOL JMS-600H.
GC analysis was conducted through a Shimadzu GC-14B
with FID using a capillary column packed with DB-17. The
apparatus of cyclic voltammetry was ALS MODEL 600. The
apparatus of elemental analysis was Yanaco CHN CORDER
MT-6. Melting point was measured by a Yanaco MP-J3.
Typical Procedure for Mg-Promoted Cross-Coupling of
Stilbene Derivatives with Carbonyl Compounds is as
Follows: Into a DMF (20 mL) solution containing
commercially available Mg turnings (40 mmol) for Grignard
reaction was added dropwise a DMF solution (40 mL) of
(3) Mikami, K.; Kaneko, M.; Loh, T.-P.; Terada, M.; Nakai, T.
Tetrahedron Lett. 1990, 31, 3909.
(4) Mikami, K.; Loh, T.-P.; Nakai, T. Tetrahedron: Asymmetry
1990, 1, 13.
Synlett 2004, No. 1, 30–36 © Thieme Stuttgart · New York

34
Y. Yamamoto et al.
LETTER
stilbene derivatives (1 or 7, 10 mmol), TMSCl (20 mmol or
50 mmol) and carbonyl compounds (2, 100 mmol) at 5–10
°C with magnetic stirring under N2 atmosphere during a
period of 45 min. After the addition, the mixture was stirred
at r.t. for additional ca 15 h. After the reaction, the reaction
mixture was poured into water (300 mL) and was extracted
with EtOAc (3 × 100 mL). The combined extracts are
washed with sat. aq NaHCO3 solution (3 × 50 mL), and sat.
aq NaCl solution (3 × 50 mL), and then dried over anhyd
MgSO4. The solution was filtered and concentrated under
reduced pressure. To the residue an EtOH solution (40 mL)
containing 1% HCl (10 mL) was added, and stirred for 20
min at r.t. Then, the reaction mixture was poured into water
(200 mL) and was extracted with EtOAc (3 × 100 mL). The
combined extracts are washed with sat. aq NaHCO3 (3 × 50
mL) solution, and sat. aq NaCl solution, and then dried over
anhyd MgSO4. Usual work-up and subsequent column
chromatography gave the corresponding cross-coupled
products 3 and 8.
3-Methyl-1,2-diphenyl-3-pentanol (3e)
Diastereomer ratio, 62:38. IR (neat): 3460, 3030, 2960,
1600, 1500, 1460, 1380, 1130 cm–1. 1H NMR (270 MHz,
CDCl3): d (mixture of isomers) = 0.95 (t, J = 7.4 Hz, 3 H),
1.12 (s, 1.86 H, major isomer), 1.25 (s, 1.14 H, minor
isomer), 1.37 (s, 1 H), 1.50–1.62 (m, 2 H), 2.87–3.31 (m, 3
H), 6.93–7.22 (m, 10 H). EI–MS (22 eV): m/z = 236 [M –
H2O]+. Anal. Calcd for C18H22O: C, 84.99; H, 8.72. Found:
C, 84.86; H, 8.88.
3-Methyl-1,2-diphenyl-3-hexanol (3f)
Diastereomer ratio, 61:39. IR (neat): 3460, 3040, 2950,
1600, 1500, 1450, 1380, 1130 cm–1. 1H NMR (270 MHz,
CDCl3): d (mixture of isomers) = 0.92 (m, 3 H), 1.14 (s, 1.83
H, major isomer), 1.26 (s, 1.17 H, minor isomer), 1.31–1.60
(m, 5 H), 2.87–3.06 (m, 2 H), 3.19–3.31 (m, 1 H), 6.93–7.24
(m, 10 H). EI–MS (22 eV): m/z = 268 [M+]. Anal. Calcd for
C19H24O: C, 85.03; H, 9.01. Found: C, 84.95; H, 8.87.
3,4-Dimethyl-1,2-diphenyl-3-pentanol (3g)
Diastereomer ratio, 58:42; mp 68–70 °C (major isomer).
IR (neat): 3450, 3030, 2960, 1590, 1510, 1460, 1370, 1140
cm–1. 1H NMR (270 MHz, CDCl3): d (major isomer) = 0.92
(s, 3 H), 1.00 (d, J = 7.1 Hz, 3 H), 1.03 (d, J = 7.1 Hz, 3 H),
1.35 (s, 1 H), 2.09 (sept, J = 7.1 Hz, 1 H), 2.93–3.04 (m, 2
H), 3.23–3.31 (m, 1 H), 6.89–7.24 (m, 10 H). 1H NMR (270
MHz, CDCl3): d (mixture of isomers) = 0.89(d, J = 6.8 Hz,
1.26 H, minor isomer), 0.92 (s, 1.74 H, major isomer), 0.95
(d, J = 6.8 Hz, 1.26 H, minor isomer), 1.00 (d, J = 7.1 Hz,
1.74 H, major isomer), 1.03 (d, J = 7.1 Hz, 1.74 H, major
isomer), 1.27 (s, 1.26 H, minor isomer), 1.40 (s, 1 H), 1.60
(sept, J = 6.8 Hz, 0.42 H, minor isomer), 2.09 (sept, J = 7.1
Hz, 0.58 H, major isomer), 2.93–3.07 (m, 2 H), 3.21–3.31
(m, 1 H), 6.89–7.31 (m, 10 H). 13C NMR (67.8 MHz,
CDCl3): d (major isomer) = 17.18, 17.98, 20.95, 34.13,
35.43, 55.05, 76.69, 125.29, 126.19, 127.76, 127.78, 128.85,
129.79, 141.20, 141.32. EI–MS (22 eV): m/z = 250 [M –
H2O]+. Anal. Calcd for C19H24O: C, 85.03; H, 9.01. Found:
C, 85.02; H, 8.92.
All the new compounds among the products were identified
by spectroscopic and elemental analysis, and others were
characterized by comparison of their chromatographic and
spectroscopic behaviors with those of the authentic samples,
as shown below.
2-Methyl-3,4-diphenyl-2-butanol (3a)17
Mp 63–66 °C. IR (neat): 3420, 3020, 2970, 1600, 1490,
1450, 1370, 1150 cm–1. 1H NMR (270 MHz, CDCl3): d =
1.24 (s, 3 H), 1.26 (s, 3 H), 1.55 (s, 1 H), 2.90 (dd, J = 3.0
Hz, J = 11.6 Hz, 1 H), 3.02 (dd, J = 11.6 Hz, J = 13.4 Hz, 1
H), 3.28 (dd, J = 3.0 Hz, J = 13.4 Hz, 1 H), 6.95–7.24 (m, 10
H). 13C NMR (67.8 MHz, CDCl3): d = 27.91, 28.39, 36.16,
59.21, 72.92, 125.39, 126.43, 127.83 (2 ×), 128.69, 129.54,
140.49, 140.95. EI–MS (22 eV): m/z = 240 [M+]. Anal.
Calcd for C17H20O: C, 84.96; H, 8.39. Found: C, 84.67; H,
8.62.
3-Ethyl-1,2-diphenyl-3-pentanol (3b)
IR (neat): 3460, 3030, 2960, 1600, 1500, 1460, 1380, 1130
cm–1. 1H NMR (270 MHz, CDCl3): d = 0.84 (t, J = 7.6 Hz, 3
H), 0.95(t, J = 7.6 Hz, 3 H), 1.23–1.45 (m, 3 H), 1.40 (q, J =
7.6 Hz, 2 H), 2.92–3.05 (m, 2 H), 3.18–3.22 (m, 1 H), 6.90–
7.19 (m, 10 H). 13C NMR (67.8 MHz, CDCl3): d = 7.74, 8.18,
28.20, 29.38, 35.85, 54.42, 76.43, 125.28, 126.19, 127.74 (2
×), 128.79, 129.87, 140.58, 141.08. EI–MS (20 eV): m/z =
268 [M+]. Anal. Calcd for C19H24O: C, 85.03; H, 9.01.
Found: C, 85.06; H, 8.92.
3,5-Dimethyl-1,2-diphenyl-3-hexanol (3h)
Diastereomer ratio, 64:36. IR (neat): 3470, 3020, 2950,
1610, 1490, 1460, 1380, 1160 cm–1. 1H NMR (270 MHz,
CDCl3): d (mixture of isomers) = 0.93–1.00 (m, 6 H), 1.18
(s, 1.92 H, major isomer), 1.25 (s, 1.08 H, minor isomer),
1.31 (s, 1 H), 1.39–1.55 (m, 2 H), 1.85–1.92 (m, 1 H),
2.85–3.05 (m, 2 H), 3.18–3.32 (m, 1 H), 6.92–7.22 (m, 10
H). EI–MS (22 eV): m/z = 264 [M – H2O]+. Anal. Calcd for
C20H26O: C, 85.06; H, 9.28. Found: C, 85.31; H, 9.02.
1,2-Diphenyl-3-hexanol (3i)
Diastereomer ratio, 61:39; mp 99–102 °C (major isomer).
IR (neat): 3380, 3040, 2910, 1590, 1500, 1450, 1360, 1140
cm–1. 1H NMR (270 MHz, CDCl3): d (major isomer) =
0.85(t, J = 6.8 Hz, 3 H), 1.23–1.57 (m, 5 H), 2.90–2.97 (m,
2 H), 3.25–3.32 (m, 1 H), 3.79–3.84 (m, 1 H), 6.97–7.26 (m,
10 H). 1H NMR (270 MHz, CDCl3): d (minor isomer) =
0.85(t, J = 7.2 Hz, 3 H), 1.19–1.47 (m, 5 H), 2.86–2.99 (m,
2 H), 3.19 (dd, J = 7.2 Hz, J = 13.6 Hz, 1 H), 3.75–3.77 (m,
1 H), 7.08–7.30 (m, 10 H). 13C NMR (67.8 MHz, CDCl3): d
(major isomer) = 14.05, 19.09, 37.00, 37.77, 54.51, 74.90,
125.54, 126.30, 127.88, 128.13, 128.52, 128.94, 140.44,
141.73. 13C NMR (67.8 MHz, CDCl3): d (minor isomer) =
14.02, 19.12, 37.79, 38.72, 53.32, 72.90, 125.81, 126.65,
128.13, 128.26, 129.07, 129.16, 140.48, 140.71. EI–MS (20
eV): m/z = 252 [M – 2]+. Anal. Calcd for C18H22O: C, 84.99;
H, 8.72. Found: C, 84.99; H, 8.95.
1-(1,2-Diphenylethyl)cyclopentanol (3c)
Mp 40–42 °C. IR (neat): 3450, 3020, 2940, 1600, 1490,
1450, 1370, 1140 cm–1. 1H NMR (270 MHz, CDCl3): d =
1.19–1.29 (m, 2 H), 1.60–1.85 (m, 7 H), 2.92 (dd, J = 5.0 Hz,
J = 9.6 Hz, 1 H), 3.11–3.21 (m, 2 H), 6.96–7.23 (m, 10 H).
13C NMR (67.8 MHz, CDCl3): d = 23.44, 23.87, 37.14,
38.84, 40.03, 57.48, 84.84, 125.40, 126.35, 127.84, 127.92,
128.74, 129.08, 140.95, 141.46. EI–MS (22 eV): m/z = 266
[M+]. Anal. Calcd for C19H22O: C, 85.67; H, 8.32. Found: C,
85.40; H, 8.22.
1-(1,2-Diphenylethyl)cyclohexanol (3d)
Mp 42–44 °C. IR (neat): 3490, 3020, 2930, 1600, 1490,
1450, 1370, 1150 cm–1. 1H NMR (270 MHz, CDCl3): d =
1.14–1.85 (m, 11 H), 2.85 (dd, J = 11.2 Hz, J = 3.0 Hz, 1 H),
3.00 (dd, J = 13.5 Hz, J = 11.2 Hz, 1 H), 3.29 (dd, J = 13.5
Hz, J = 3.0 Hz, 1 H), 6.93–7.23 (m, 10 H). 13C NMR (67.8
MHz, CDCl3): d = 21.97, 22.09, 25.76, 35.48, 35.89, 35.97,
58.56, 73.25, 125.29, 126.26, 127.75 (2 ×), 128.79, 129.73,
140.54, 141.25. EI–MS (22 eV): m/z = 280 [M+]. Anal.
Calcd for C20H24O: C, 85.67; H, 8.63. Found: C, 85.64; H,
8.64.
1,2-Diphenyl-3-heptanol (3j)
Diastereomer ratio, 60:40; mp 75–77 °C (major isomer).
IR (neat): 3390, 3030, 2910, 1600, 1500, 1450, 1350, 1140
Synlett 2004, No. 1, 30–36 © Thieme Stuttgart · New York

LETTER
cm–1. 1H NMR (270 MHz, CDCl3): d (major isomer) = 0.84
Mg-Promoted Regioselective Cross-Coupling
35
(m, 2 H), 3.36 (dd, J = 17.2 Hz, J = 7.7 Hz, 1 H), 3.42 (dd,
J = 17.2 Hz, J = 4.4 Hz, 1 H), 3.82 (ddd, J = 7.7 Hz, J = 4.4
Hz, J = 2.4 Hz, 1 H), 4.07–4.11 (m, 1 H), 7.28 (d, J = 7.6 Hz,
1 H), 7.31 (d, J = 7.6 Hz, 1 H), 7.44(t, J = 7.6 Hz, 1 H), 7.46
(t, J = 7.6 Hz, 1 H), 7.59 (d, J = 7.6 Hz, 1 H), 7.63 (d, J = 7.6
Hz, 1 H). 1H NMR (400 MHz, CDCl3): d (mixture of
isomers) = 0.99 (t, J = 7.3 Hz, 1.08 H, minor isomer), 1.03
(t, J = 7.3 Hz, 1.92 H, major isomer), 1.38 (s, 0.64 H, major
isomer), 1.51–1.66 (m, 2 H), 1.71 (s, 0.36 H, minor isomer),
3.19 (dd, J = 17.6 Hz, J = 3.0 Hz, 0.36 H, minor isomer),
3.32 (dd, J = 17.6 Hz, J = 7.1 Hz, 0.64 H, major isomer), 3.39
(dd, J = 17.6 Hz, J = 4.4 Hz, 0.64 H, major isomer), 3.46(dd,
J = 17.6 Hz, J = 8.3 Hz, 0.36 H, minor isomer), 3.60–3.67
(m, 0.36 H, minor isomer), 3.73–3.79 (m, 1 H), 4.03–4.07
(m, 0.64 H, major isomer), 7.20–7.62 (m, 6 H). 13C NMR
(100 MHz, CDCl3): d = (major isomer) = 10.58, 27.39,
31.30, 49.00, 75.37, 119.04, 119.35, 122.21, 123.30, 127.66,
128.00, 131.44, 139.54, 144.76, 145.95. EI–MS: m/z = 212
[M+]. Anal. Calcd for C15H16O: C, 84.87; H, 7.60. Found: C,
84.72; H, 7.55.
(t, J = 6.9 Hz, 3 H), 1.19–1.58 (m, 7 H), 2.87–2.98 (m, 2 H),
3.25–3.36 (m, 1 H), 3.80 (m, 1 H), 6.96–7.26 (m, 10 H). [1H
NMR (270 MHz, CDCl3): d (mixture of isomers) = 0.81–
0.88 (m, 3 H), 1.19–1.58 (m, 7 H), 2.85–3.00 (m, 2 H), 3.15–
3.39 (m, 1 H), 3.80 (m, 1 H), 6.96–7.31 (m, 10 H). 13C NMR
(67.8 MHz, CDCl3): d (major isomer) = 14.13, 22.65, 28.09,
34.55, 37.74, 54.47, 75.18, 125.55, 126.31, 127.90, 128.14,
128.52, 128.95, 140.45, 141.76. EI–MS (20 eV): m/z = 266
[M – 2]+. Anal. Calcd for C19H24O: C, 85.03; H, 9.01. Found:
C, 84.75; H, 8.86.
4-Methyl-1,2-diphenyl-3-pentanol (3k)
Diastereomer ratio, 60:40.; mp 74–75 °C (major isomer).
IR (neat): 3380, 3010, 2900, 1610, 1500, 1450, 1380, 1140
cm–1. 1H NMR (270 MHz, CDCl3): d (major isomer) = 0.84
(d, J = 6.8 Hz, 3 H), 0.95 (d, J = 6.8 Hz, 3 H), 1.54–1.61 (m,
2 H), 2.82–2.98 (m, 2 H), 3.36–3.41 (m, 1 H), 3.64–3.70 (m,
1 H), 6.91–7.25 (m, 10 H). 1H NMR (270 MHz, CDCl3): d
(minor isomer) = 0.93 (d, J = 6.8 Hz, 3 H), 0.93(d, J = 6.8
Hz, 3 H), 1.28 (m, 1 H), 1.53–1.63 (m, 1 H), 2.89–3.18 (m,
3 H), 3.42 (m, 1 H), 7.05–7.30 (m, 10 H). 13C NMR (67.8
MHz, CDCl3): d (major isomer) = 15.19, 20.42, 29.95,
38.40, 52.09, 79.95, 125.47, 126.19, 127.80, 128.18, 128.38,
129.05, 140.52, 142.11. 13C NMR (67.8 MHz, CDCl3): d
(minor isomer) = 7.63, 19.89, 31.12, 39.52, 50.54, 78.43,
125.72, 126.53, 128.03, 128.19, 128.97, 129.11, 140.32,
140.96. EI–MS (20 eV): m/z = 252 [M – 2]+. Anal. Calcd for
C18H22O: C, 84.99; H, 8.72. Found: C, 85.20; H, 9.02.
2,3-Dimethyl-3,4-diphenyl-2-butanol (3l)
IR (neat): 3490, 3030, 2980, 1600, 1500, 1460, 1380, 1160
cm–1. 1H NMR(270 MHz, CDCl3): d = 1.09 (s, 3 H), 1.23 (s,
3 H), 1.31 (s, 3 H), 1.41 (s, 1 H), 2.90 (d, J = 13.8 Hz, 1 H),
3.72(d, J = 13.8 Hz, 1 H), 6.84–7.53 (m, 10 H). 13C NMR
(67.8 MHz, CDCl3): d = 21.16, 26.31, 26.48, 40.65, 49.43,
75.62, 125.59, 126.05, 127.39, 127.48, 128.88, 130.32,
139.18, 143.41. EI–MS (22 eV): m/z = 236 [M – H2O]+.
Anal. Calcd for C18H22O: C, 84.99; H, 8.72. Found: C, 84.85;
H, 8.69.
1-(1-Hydroxybutyl)acenaphthene (8b)
Diastereomer ratio, 62:38; mp 67–69 °C (major isomer), 96–
99 °C (minor isomer). IR (neat): 3560, 3460, 3040, 2960,
2930, 2870, 1620, 1600, 1500 cm–1. 1H NMR (400 MHz,
CDCl3): d (major isomer) = 0.97 (t, J = 7.0 Hz, 3 H), 1.32 (s,
1 H), 1.37–1.62 (m, 4 H), 3.33 (dd, J = 17.4 Hz, J = 7.7 Hz,
1 H), 3.40 (dd, J = 17.4 Hz, J = 4.6Hz, 1 H), 3.77 (ddd, J =
7.7 Hz, J = 4.6 Hz, J = 2.4 Hz, 1 H), 4.16–4.17 (m, 1 H), 7.27
(d, J = 7.6 Hz, 1 H), 7.29 (d, J = 7.6 Hz, 1 H), 7.44 (t, J = 7.6
Hz, 1 H), 7.45 (t, J = 7.6 Hz, 1 H), 7.58 (d, J = 7.6 Hz, 1 H),
7.62 (d, J = 7.6 Hz, 1 H). 1H NMR (400 MHz, CDCl3): d
(minor isomer) = 0.94(t, J = 7.1 Hz, 3 H), 1.37–1.61 (m, 4
H), 1.70 (s, 1 H), 3.22 (d, J = 17.4 Hz, 1 H), 3.49 (dd, J =
17.4 Hz, J = 7.6 Hz, 1 H), 3.76–3.78 (m, 2 H), 7.27 (d, J =
7.6 Hz, 1 H), 7.39–7.46 (m, 3 H), 7.59 (d, J = 7.6 Hz, 1 H),
7.63 (d, J = 7.6 Hz, 1 H). 13C NMR (100 MHz, CDCl3): d =
(major isomer) = 14.11, 19.36, 31.34, 36.60, 49.39, 73.56,
119.06, 119.35, 122.21, 123.29, 127.66, 127.99, 131.42,
139.54, 144.77, 145.95. 13C NMR (100 MHz, CDCl3): d
(minor isomer) = 14.04, 19.23, 34.30, 36.69, 49.68, 74.90,
119.25, 120.53, 122.35, 123.32, 127.64, 127.86, 131.55,
139.31, 144.39, 145.51. EI–MS: m/z = 226 [M+]. Anal.
Calcd. for C16H18O: C, 84.91; H, 8.02. Found: C, 85.15; H,
7.96.
1-(1-Hydroxy-2-methylpropyl)acenaphthene (8c)
Diastereomer ratio, 75:25. IR (neat): 3450, 3040, 2960,
2870, 1620, 1600, 1590, 1500 cm–1. 1H NMR (400 MHz,
CDCl3): d (mixture of isomers) = 1.07 (d, J = 6.8 Hz, 0.75 H,
minor isomer), 1.08 (d, J = 6.8 Hz, 2.25 H, major isomer),
1.11 (d, J = 6.8 Hz, 0.75 H, minor isomer), 1.14 (d, J = 6.8
Hz, 2.25 H, major isomer), 1.22(d, J = 3.2 Hz, 0.75 H, major
isomer), 1.45(d, J = 6.4 Hz, 0.25 Hz, minor isomer), 1.93–
2.11 (m, 1 H), 3.22 (dd, J = 16.8 Hz, J = 3.6 Hz, 0.25 H,
minor isomer), 3.36 (dd, J = 17.4 Hz, J = 8.2 Hz, 0.75 H,
major isomer), 3.43–3.97 (m, 3 H), 7.28–7.65 (m, 6 H).
EI–MS: m/z = 226 [M+]. Anal. Calcd for C16H18O: C, 84.91;
H, 8.02. Found: C, 84.85; H, 8.19.
2,4-Dimethyl-1,2-diphenyl-3-pentanol (3m)
Diastereomer ratio, 55:45; mp 56–58 °C (minor isomer). 1H
NMR (270 MHz, CDCl3): d (minor isomer) = 0.42 (d, J = 7.0
Hz, 3 H), 0.99(d, J = 7.0 Hz, 3 H), 1.22 (s, 3 H), 1.43 (d, J =
6.8 Hz, 1 H), 1.96 (dsept, J = 2.1 Hz, J = 7.0 Hz, 1 H), 3.08(d,
J = 13.2 Hz, 1 H), 3.18 (d, J = 13.2 Hz, 1 H), 3.57 (dd, J =
2.1 Hz, J = 6.8 Hz, 1 H), 6.89–7.49 (m, 10 H). 1H NMR (270
MHz, CDCl3): d (mixture of isomers) = 0.42 (d, J = 7.0 Hz,
1.35 H, minor isomer), 0.74 (d, J = 6.9 Hz, 1.65 H, major
isomer), 0.82 (d, J = 6.9 Hz, 1.65 H, major isomer), 0.98 (d,
J = 7.0 Hz, 1.35 H, minor isomer), 1.22 (s, 1.35 H, minor
isomer), 1.24 (s, 1.65 H, major isomer), 1.50 (d, J = 6.8 Hz,
0.45 H, minor isomer), 1.60 (dsept, J = 2.7 Hz, J = 6.9 Hz,
0.55 H, major isomer), 1.70 (d, J = 6.8 Hz, 0.55 H, major
isomer), 1.96 (dsept, J = 2.1 Hz, J = 7.0 Hz, 0.45 H, minor
isomer), 3.06–3.20 (m, 2 H), 3.57 (dd, J = 2.1 Hz, J = 6.8 Hz,
0.45 H, minor isomer), 3.89 (dd, J = 2.7 Hz, J = 6.8 Hz, 0.55
H, major isomer), 6.64–7.49 (m, 10 H). 13C NMR (67.8
MHz, CDCl3): d (minor isomer) = 16.17, 20.16, 23.97,
28.63, 45.79, 47.14, 82.33, 125.74, 126.17, 127.39, 127.70,
127.95, 130.49, 138.37, 144.15. EI–MS (22 eV): m/z = 266
[M – 2]+. Anal. Calcd for C19H24O: C, 85.03; H, 9.01. Found:
C, 85.09; H, 9.11.
1-(1-Hydroxybutyl)-1-methylacenaphthene (8d)
Diastereomer ratio, 65:35. IR (neat): 3450, 3040, 2960,
2870, 1620, 1600, 1500 cm–1. 1H NMR (400 MHz, CDCl3):
d (major isomers) = 0.90 (t, J = 7.3 Hz, 3 H), 1.20–1.60 (m,
8 H), 2.96 (d, J = 17.1 Hz, 1 H), 3.54 (d, J = 17.1 Hz, 1 H),
3.66–3.69 (m, 1 H), 7.20–7.62 (m, 6 H). 1H NMR (400 MHz,
CDCl3): d (minor isomer) = 0.84 (t, J = 7.2 Hz, 3 H), 1.17–
1.63 (m, 7 H), 1.72 (s, 1 H), 3.04 (d, J = 17.2 Hz, 1 H), 3.52
(d, J = 17.2 Hz, 1 H), 3.81–3.84 (m, 1 H), 7.22–7.64 (m, 6
1-(1-Hydroxypropyl)acenaphthene (8a)
Diastereomer ratio, 64:36; mp: 59–60 °C (major isomer).
IR (neat): 3560, 3420, 3040, 2960, 2930, 2880, 1620, 1600,
1590, 1500 cm–1. 1H NMR (400 MHz, CDCl3): d (major
isomer) = 1.06 (t, J = 7.4 Hz, 3 H), 1.32 (s, 1 H), 1.61–1.68
Synlett 2004, No. 1, 30–36 © Thieme Stuttgart · New York

36
Y. Yamamoto et al.
LETTER
H). 13C NMR (100 MHz, CDCl3): d (major isomer) = 14.02,
19.78, 25.63, 33.68, 40.88, 52.86, 77.75, 118.09, 119.39,
122.30, 123.34, 127.73, 127.99, 131.33, 138.30, 143.57,
150.55. 13C NMR (100 MHz, CDCl3): d (minor isomer) =
13.93, 19.92, 24.41, 34.23, 41.87, 52.60, 78.13, 118.75,
119.30, 122.37, 123.27, 127.73, 127.97, 131.46, 138.04,
143.48, 150.90. EI–MS: m/z = 240 [M+]. Anal. Calcd for
C17H20O: C, 84.96; H, 8.39. Found: C, 84.79; H, 8.61.
1-(1-Hydroxy-1-phenylethyl) acenaphthene (8e)
Diastereomer ratio, 63:37; mp 147–150 °C (minor isomer).
IR (neat): 3540, 3450, 3090, 3050, 3030, 2970, 2930, 1600,
1590, 1490 cm–1. 1H NMR (400 MHz, CDCl3): d (minor
isomer)= 1.56 (s, 3 H), 1.72 (s, 1 H), 3.41 (dd, J = 17.6 Hz,
J = 7.6 Hz, 1 H), 3.47 (dd, J = 17.6 Hz, J = 4.8 Hz, 1 H), 4.30
(dd, J = 7.6 Hz, J = 4.8 Hz, 1 H), 6.48 (d, J = 6.8 Hz, 1 H),
7.20–7.58 (m, 10 H). 1H NMR (400 MHz, CDCl3): (mixture
of isomers) = 1.53 (s, 1.11 H, minor), 1.59 (s, 1.89 H,
major), 1.73 (s, 0.63 H, major), 1.78 (s, 0.37, minor), 3.23–
3.46 (m, 2 H), 4.20 (dd, J = 8.0 Hz, J = 3.2 Hz, 0.63 H,
major), 4.26 (dd, J = 7.2 Hz, J = 4.8 Hz, 0.37 H, minor), 6.45
(d, J = 6.8 Hz, 0.37 H, minor), 7.00 (d, J = 6.8 Hz, 0.63 H,
major), 7.20–7.61 (m, 10 H). 13C NMR (100 MHz, CDCl3):
d (minor isomer) = 27.32, 33.84, 54.42, 76.85, 119.06,
121.37, 122.27, 123.47, 125.41, 126.90, 127.40, 127.68,
128.27, 131.29, 139.78, 143.88, 144.06, 147.71. EI–MS:
m/z = 274 [M+]. Anal. Calcd for C20H18O: C, 87.56; H, 6.61.
Found: C, 87.73; H, 6.82.
127.95, 128.14, 128.72, 129.48, 138.50, 139.69, 176.40. EI–
MS: m/z = 280 [M+]. Anal. Calcd for C19H20O2: C, 81.40; H,
7.19. Found: C, 81.45; H, 7.28.
(13) a-Methylstilbene (1b) was prepared by the reaction of
benzylmagnesium chloride with benzaldehyde followed by
dehydration.
a-Methylstilbene (1b)
Mp: 79–81 °C. IR (neat): 3080, 3050, 3030, 2990, 2960,
1960, 1990, 1620, 1600 cm–1. 1H NMR (270 MHz, CDCl3):
d = 2.27 (s, 3 H), 6.83(s, 1 H), 7.23–7.53 (m, 10 H). 13
C
NMR (CDCl3): d = 17.56, 125.89, 126.35, 127.07, 127.67,
128.05, 128.21, 129.02, 137.29, 138.23, 143.83. EI–MS:
m/z = 194 [M+].
(14) 1-Methylacenaphthylene (7b) was prepared by the reported
method. See: Bosch A., Brown R. K.; Can. J. Chem.; 1968,
46: 715
1-Methylacenaphthylene (7b)
IR (neat): 3060, 3040, 2970, 2910, 1620, 1550 cm–1. 1H
NMR (400 MHz, CDCl3): d = 2.38 (d, J = 1.4 Hz, 3 H),
6.65(d, J = 1.4 Hz, 1 H), 7.39–7.49 (m, 3 H), 7.56 (d, J = 7.6
Hz, 1 H), 7.63 (d, J = 7.6 Hz, 1 H), 7.72 (d, J = 7.6 Hz, 1 H).
13C NMR (CDCl3): d = 13.10, 121.64, 122.28, 125.24,
125.79, 127.07, 127.31, 127.69, 127.82, 128.92, 139.76,
140.24, 140.99. EI–MS: m/z = 166 [M+].
(15) The possibility of protonation prior to the electrophilic
attack of carbonyl compounds 2 on the anion radical species
9 may be excluded in the present cross-coupling because the
first protonation to 9 generated from a-methylstilbene(1a)
lead to generation of more unstable tertiary carbanion, which
may be difficult to form, in order to confirm the observed
regioselectivity.
(16) As another possible explanation for unusual regioselectivity
of this reaction, it may seem operative that the tertiary
carbanion of the a-position of the anion radical species 9
may be more unstable, but more reactive than the secondary
carbanion of 9 to be preferentially subjected to electrophilic
attack of carbonyl compounds 2.
g-(1,2-Diphenylethyl)-g-methyl-g-lactone (14)
Diastereomer ratio, 63:37; mp 134–136 °C (major isomer).
IR (neat): 3020, 2970, 1750, 1600, 1500, 1460, 1380, 1140
cm–1. 1H NMR (270 MHz, CDCl3): d (major isomer) = 1.40
(s, 3 H), 1.71–1.82 (m, 1 H), 2.26–2.61 (m, 3 H), 3.04–3.11
(m, 2 H), 3.27–3.31 (m, 1 H), 6.72–7.27 (m, 10 H). 1H NMR
(270 MHz, CDCl3): d (mixture of isomers) = 1.40 (s, 1.89 H,
major isomer), 1.48 (s, 1.11 H, minor isomer), 1.71–2.63 (m,
4 H), 3.00–3.11 (m, 2 H), 3.24–3.31 (m, 1 H), 6.72–7.27 (m,
10 H). 13C NMR (67.8 MHz, CDCl3): d (major isomer) =
24.05, 28.96, 32.46, 36.18, 57.54, 88.50, 125.74, 127.02,
(17) Takahashi, T.; Swanson, D. R.; Negishi, E. Chem. Lett.
1987, 623.
Synlett 2004, No. 1, 30–36 © Thieme Stuttgart · New York