7.22 (m, 1H), 7.27–7.34 ppm (m, 2H); 13C NMR (125 MHz, CDCl3):
d=14.1, 19.9, 20.5, 22.7, 27.8, 31.9, 34.3, 125.7, 127.9 (2C), 128.4
(2C), 130.2, 131.6, 145.6 ppm; IR (neat): nmax =2924, 1599, 1491,
(E)-2-(2-Methyl-3-phenylbut-2-en-1-ylidene)malononitrile
[(E)-13] (Scheme 4)
1441, 1373, 1072, 1024, 764, 700 cmÀ1
.
Ti(OiPr)4 (0.073 mL, 0.25 mmol) was added to a stirred solution of
(E)-9 (80 mg, 0.5 mmol) and malononitrile (33 mg, 0.5 mmol) in
iPrOH (0.5 mL) at 20–258C under an Ar atmosphere, followed by
being stirred at the same temperature for 24 h. Aqueous HCl (1m)
was added to the mixture, which was extracted twice with AcOEt.
The combined organic phase was washed with water, brine, dried
(Na2SO4) and concentrated. The obtained crude solid was purified
by SiO2 gel column chromatography (hexane/AcOEt 20:1) to give
(4E)-13 as yellow crystals (84 mg, 81%, E/Z=97:3). M.p. 83–868C;
1H NMR (500 MHz, CDCl3): d=2.07 (s, 3H), 2.33 (s, 3H), 7.12–7.17
(m, 2H), 7.34–7.39 (m, 1H), 7.39–7.44 (m, 2H) 7.97 ppm (s, 1H);
13C NMR (125 MHz, CDCl3): d=17.6, 22.7, 81.8, 113.2, 115.1, 127.2
(2C), 128.3, 128.6, 128.7 (2C), 142.0, 157.4, 158.1 ppm; IR (neat):
(E)-2-Methyl-3-phenylbut-2-enal [(E)-9] (Scheme 4)
A mixture of (E)-8 (316 mg, 2.0 mmol) and MnO2 (6.96 g, 80 mmol)
in CH2Cl2 (40 mL) was stirred at 20–258C under an Ar atomosphere
for 12 h. The mixture was filtered through Celite, and the filtrate
was concentrated to give (E)-9 as a colorless oil (316 mg, 99%, E/
Z= >98:2), which did not need further purification. 1H NMR
(500 MHz, CDCl3): d=1.67 (s, 3H), 2.47 (s, 3H), 7.15–7.23 (m, 2H),
7.30–7.37 (m, 1H), 7.37–7.45 (m, 2H), 10.35 ppm (s, 1H); 13C NMR
(125 MHz, CDCl3): d=13.1, 19.5, 126.9 (2C), 128.0, 128.5 (2C), 133.3,
142.9, 155.7, 192.0 ppm; IR (neat): nmax =2864, 1620, 1597, 1493,
1373, 1308, 1277, 1217, 972 cmÀ1; HRMS (ESI): m/z: calcd for
C11H12O: 183.0786 [M+Na]+; found: 183.0781.
nmax =2962, 2924, 2218, 1580, 1443, 1377, 1323, 1234, 1063 cmÀ1
.
(Z)-2-Methyl-3-phenylbut-2-enoic acid [(Z)-7] (Scheme 4)
In a procedure similar to the preparation of (E)-7, the reaction of
(Z)-5b-1 (204 mg, 1.00 mmol) in CF3CO2H (1.0 mL) and H2O
(0.5 mL) gave (Z)-7; as pale yellow crystals (105 mg, 60%, E/Z=2:>
98). M.p. 105–1078C; 1H NMR (500 MHz, CDCl3): d=2.01 (s, 3H),
2.09 (s, 3H), 7.02–7.17 (m, 2H), 7.18–7.37 (m, 3H), 9.32 ppm (brs,
1H); 13C NMR (125 MHz, CDCl3): d=16.2, 22.6, 124.6, 126.7 (2C),
127.1, 128.0 (2C), 143.6, 146.4, 175.3 ppm; IR (neat): nmax =2999,
2669, 1657, 1506, 1435, 1308, 1279, 1206, 1153 cmÀ1; HRMS (DART):
m/z: calcd for C11H12O2: 177.0916 [M+H]+; found: 177.0927.
(E)-(3-Methylpenta-2,4-dien-2-yl)benzene [(E)-11] (Scheme 4)
A mixture of MeP+Ph3IÀ (808 mg, 2.0 mmol) and tBuOK (224 mg,
2.0 mmol) in THF (1.0 mL) was stirred for 0.5 h at 0–58C under an
Ar atmosphere. (E)-9 (80 mg, 0.5 mmol) in THF (1.0 mL) was added
to the mixture at the same temperature, and the reaction mixture
was stirred for 1 h. The mixture was poured into water, and the ob-
tained mixture was extracted twice with Et2O. The combined or-
ganic phase was washed with water and brine, then dried (Na2SO4)
and concentrated. The obtained crude product was purified by
SiO2 gel column chromatography (hexane) to give (E)-11 (52 mg,
(Z)-2-Methyl-3-phenylbut-2-en-1-yl acetate [(Z)-8’, Scheme 4]
1
66%, E/Z= >98:2). Colorless oil; H NMR (500 MHz, CDCl3): d=1.69
In a procedure similar to the preparation of (E)-8, the reaction of
(Z)-5b-1 (1.43 g, 7.0 mmol) with DIBAL (20.6 mL, 21.0 mmol; 1.02m
in toluene) gave (Z)-8 as a colorless oil (1.11 g, 98%, E/Z=2:>98).
1H NMR (500 MHz, CDCl3): d=1.19 (s, 1H), 1.91 (s, 3H), 2.00 (s, 3H),
3.95 (s, 2H), 7.09–7.16 (m, 2H), 7.20–7.25 (m, 1H), 7.28–7.35 ppm
(m, 2H); 13C NMR (125 MHz, CDCl3): d=16.2, 21.1, 64.7, 126.4,
(s, 3H), 2.12 (s, 3H), 5.16 (d, J=10.9 Hz, 1H), 5.28 (d, J=17.2 Hz,
1H), 6.99 (dd, J=10.9, 17.2 Hz, 1H), 7.10–7.17 (m, 2H), 7.19–7.26
(m, 1H), 7.29–7.40 ppm (m, 2H); 13C NMR (125 MHz, CDCl3): d=
15.6, 20.7, 113.5, 126.4, 128.2 (2C), 128.3 (2C), 128.9, 135.8, 136.3,
145.2 ppm; IR (neat): nmax =3022, 2920, 1603, 1491, 1441, 1373,
1109, 986 cmÀ1
.
127.96 (2C), 128.03 (2C), 130.4, 134.7, 143.7 ppm; IR (neat): nmax
=
3335, 2918, 1599, 1491, 1441, 1242, 997, 763, 700 cmÀ1; HRMS
(DART): m/z: calcd for C11H13: 145.1017 [MÀOAc]+; found: 145.1003.
Methyl (2E,4Z)-4-Methyl-5-phenylhexa-2,4-dienoate [(E)-12]
(Scheme 4)
In a procedure similar to the preparation of (E)-8’, the reaction of
(Z)-8 (744 mg, 4.59 mmol) using Ac2O (562 mg, 5.51 mmol), DMAP
(28 mg, 5 mol%), and Et3N (557 mg, 5.51 mmol) gave (Z)-8’ as a col-
orless oil (849 mg, 91%, E/Z=2:>98). 1H NMR (500 MHz, CDCl3):
d=1.85 (s, 3H), 2.03 (s, 3H), 2.04 (s, 3H), 4.42 (s, 2H), 7.07–7.15 (m,
2H), 7.20–7.25 (m, 1H), 7.27–7.34 ppm (m, 2H); 13C NMR (125 MHz,
CDCl3): d=16.3, 20.9, 21.2, 66.7, 125.8, 126.6, 127.9 (2C), 128.1 (2C),
137.3, 143.1, 171.0 ppm; IR (neat): nmax =2918, 1738, 1491, 1441,
1375, 1229, 1022, 766, 702 cmÀ1; HRMS (DART): m/z: calcd for
C11H13 145.1017 [MÀOAc]+; found: 145.1003.
(MeO)2P(O)CH2CO2Me (137 mg, 0.75 mmol) and 1,8-diazabicy-
clo[5.4.0]undec-7-ene (DBU, 91 mg, 0.6 mmol) were successively
added to a stirred solution of LiCl (25 mg, 0.6 mmol) in MeCN
(0.5 mL) at 20–258C under an Ar atmosphere. (E)-9 (80 mg,
0.5 mmol) in THF (0.5 mL) was added to the mixture, which was
stirred at the same temperature for 1 h. Saturated aq. NH4Cl was
added to the mixture, which was extracted twice with Et2O. The
combined organic phase was washed with water and brine, then
dried (Na2SO4) and concentrated. The obtained crude product was
purified by SiO2 gel column chromatography (hexane/AcOEt 20:1)
to give (4E)-12 as yellow crystals (98 mg, 91%, E/Z= >98:2)
M.p. 88–898C; 1H NMR (500 MHz, CDCl3): d=1.71 (s, 3H), 2.24 (s,
(Z)-(3-Methylpent-2-en-2-yl)benzene [(Z)-14a, Scheme 4]
3H), 3.78 (s, 3H), 5.94 (d, J=15.5 Hz, 1H), 7.09–7.17 (m, 2H), 7.22– In a procedure similar to the preparation of (E)-14a, the reaction of
7.30 (m, 1H), 7.31–7.38 (m, 2H), 8.00 ppm (d, J=15.5 Hz, 1H);
13C NMR (125 MHz, CDCl3): d=16.1, 21.4, 51.6, 117.6, 127.1, 127.7,
127.8 (2C), 128.3 (2C), 143.5, 144.1, 145.0, 168.3 ppm; IR (neat):
(Z)-8’ (102 mg, 0.5 mmol) using MeLi (3.37 mL, 3.00 mmol; 0.89m
in Et2O) and CuI (333 mg, 1.75 mmol) gave (E)-14a as a colorless
oil (72 mg, 90%, E/Z=2:>98). 1H NMR (500 MHz, CDCl3): d=0.92
(t, J=7.5 Hz, 3H), 1.78 (s, 3H), 1.90 (q, J=7.5 Hz, 2H), 1.93 (s, 3H),
7.06–7.15 (m, 2H), 7.16–7.22 (m, 1H), 7.26–7.33 ppm (m, 2H);
13C NMR (125 MHz, CDCl3): d=13.3, 17.3, 21.1, 28.3, 125.7, 128.0
nmax =2947, 1713, 1614, 1491, 1433, 1377, 1298, 1269, 1167 cmÀ1
;
HRMS (ESI): m/z: calcd for C14H16O2: 239.1048 [M+Na]+; found:
236.1047.
ChemistryOpen 2017, 6, 73 –89
85
ꢀ 2017 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim