JOURNAL OF CHEMICAL RESEARCH 2015 557
1
Experimental
3-(4-(t-Butyl)phenyl)-2-methylpropanal (1e): Oil; H NMR δ 9.65
1H NMR (400 MHz) and 13C NMR (100 MHz) spectra were obtained
using a Varian Mercury plus 400 spectrometer (Varian, CA, USA)
equipped with a 5 mm ID probe or a 5 mm ASW probe using CDCl3
as the solvent with tetramethylsilane (TMS) as an internal standard.
GC spectra were obtained on a SHIMADZU GC-SPL-2010 Plus
instrument with rtx-1 as the GC column. Mass spectra were measured
with a Thermo Finnigan LC Advantage (Agilent 1100). GC-MS
spectra were measured with a GCT Premier GC/MS using ESI or EI
(electrospray ionization) techniques.
(1H, s, CHO), 7.27 (2H, d, J = 8.0 Hz, ArH), 7.06 (2H, d, J = 8.0 Hz,
ArH), 3.04–2.99 (1H, dd, J = 5.6, 13.2 Hz, CH2a), 2.66–2.51 (2H, m,
CH2b, CH), 1.29 (9H, s, CH3), 1.05 (3H, d, J = 8.0 Hz, CH3); 13C NMR
δ 204.3, 148.5, 137.4, 128.8, 125.1, 39.3, 37.1, 37.0, 34.4, 31.5, 13.9; MS
(ESI): m/z =227 [M+Na]+.
3-(4-(sec-Butyl)phenyl)-2-methylpropanal (1f): Oil; 1H NMR δ 9.69
(1H, s, CHO), 7.13 (2H, d, J = 8.0 Hz, ArH), 7.06 (2H, d, J = 8.0 Hz,
ArH), 3.07–3.02 (1H, dd, J = 8.0, 12.0 Hz, CH2a), 2.68–2.54 (2H, m,
CH2b, CH), 2.43 (H, d, J = 8.0 Hz, CH2), 1.88–1.78 (1H, m, CH), 1.08
(3H, d, J = 8.0 Hz, CH3), 0.89 (6H, d, J = 8.0 Hz, CH3); 13C NMR δ
204.1, 129.1, 128.8, 128.5, 48.1, 45.1, 36.4, 30.3, 22.5, 13.3; MS (ESI):
m/z =227 [M+Na]+.
Synthesis of methacrolein diacetyl acetal 4; general procedure
A dry 100-mL flask was charged with Ac2O (51.0 g, 0.5 mol)
and BF3·Et2O (0.07 g, 0.5 mmol), cooled to –10oC, and then
methacrolein (35.0 g, 0.5 mol) was added over 20 min. The
mixture was the stirred at –10oC for 3 h. Methacrolein diacetyl
acetal 4 was then easily obtained by vacuum distillation (20
mmHg, 72.5g, 85%).
1
3-4-Amyl-2-methyl-3-phenyl propanal (1g): Oil; H NMR δ 9.70
(1H, s, CHO), 7.27 (2H, d, J = 8.0 Hz, ArH), 7.06 (2H, d, J = 8.0 Hz,
ArH), 3.06–3.02 (1H, dd, J = 4.0, 12.0 Hz, CH2a), 2.70–2.54 (2H, m,
CH2b, CH), 2.45–2.35 (2H, m, CH2), 1.28 (6H, s, CH3), 1.08 (3H, d,
J = 8.0 Hz, CH3), 0.66 (3H, t, J = 8.0 Hz, CH3). 13C NMR δ 204.1, 147.3,
135.3, 128.4, 125.9, 48.0, 37.6, 36.9, 36.2, 28.5, 13.4, 9.2; MS (ESI):
m/z =217 [M-H]-.
3-(4-Methoxyphenyl)-2-methylpropanal (1h): Oil; 1H NMR δ 9.67
(1H, s, CHO), 7.05 (2H, d, J = 8.0 Hz, ArH), 6.81 (2H, d, J = 8.0 Hz, ArH),
3.76 (3H, s, CH3), 3.02–2.98 (1H, dd, J = 4.0, 12.0 Hz, CH2a), 2.64–2.52
(2H, m, CH2b, CH), 1.06 (3H, d, J = 8.0 Hz, CH3);13C NMR δ 204.1, 157.5,
130.0, 113.5, 55.1, 39.5, 36.5, 13.7; MS (ESI): m/z = 201 [M+Na]+.
2-Methacrolein diacetyl acetal (4): Oil; 1H NMR δ 7.05 (1H, s, CH),
5.23 (1H, qua, CH2a), 5.06 (1H, qui, CH2b), 2.08 (6H, s, CH3), 1.78 (3H,
t, CH3). 13C NMR δ 168.3, 138.5, 116.1, 90.6, 20.8, 16.6; MS (ESI): m/z
= 195[M+Na]+.
Synthesis of para-substituted aromatic aldehydes 1a–k; general
procedure
A dry 50-mL flask was charged with methacrolein diacetyl acetal 4
(3.4 g, 20 mmol) and a substituted benzene 3 (160 mmol). Then, TiCl4
(5.7 g, 30 mmol) was added into the mixture dropwise at–10 oC over
30 min. The mixture was stirred at –10 oC for further 1–4 h. After the
reaction had finished, the mixture was poured with agitation onto
dilute hydrochloric acid (1M). The brownish-red solution became
decolourised, and was washed with water. The organic layer was added
into solution MeOH/KOH/H2O (4 mL, mass ratio: 4:2:2) and stirred
for 1 h at room temperature. Then the organic layer was washed three
times with water and after drying over anhydrous sodium sulfate was
distilled under a vacuum of 20 mmHg. Yellowish liquids 1a–k were
obtained.
2-Methyl-3-phenylpropanal (1a): Oil; 1H NMR δ 9.65 (1H, s, CHO),
7.31–7.05 (5H, m, ArH), 3.08–3.03 (1H, dd, J = 5.6, 13.2 Hz, CH2a),
2.66–2.54 (2H, m, CH2b, CH), 1.05 (3H, d, J = 8.0 Hz, CH3); 13C NMR
δ 203.9, 138.6, 128.8, 128.3, 126.2, 48.0, 36.7, 13.3; MS (ESI): m/z =
147[M-H]-.
2-Methyl-3-(p-tolyl)propanal (1b): Oil; 1H NMR δ 9.65 (1H, s,
CHO), 7.12–7.00 (4H, m, ArH), 3.03–2.98 (1H, dd, J = 4.0, 12.0 Hz,
CH2a), 2.65–2.50 (2H, m, CH2b, CH), 2.29 (3H, s, CH3), 1.05 (3H, d,
J = 8.0 Hz, CH3); 13C NMR δ 204.3, 141.8, 137.8, 129.4, 127.8, 39.7,
28.9, 16.0, 14.1; MS (EI): m/z =162 [M].
3-(4-Ethylphenyl)-2-methylpropanal (1c): Oil; 1H NMR δ 9.66 (1H,
s, CHO), 7.16–7.04 (4H, m, ArH), 3.04–3.00 (1H, dd, J = 8.0, 16.0
Hz, CH2a), 2.66–2.52 (4H, m, CH2b, CH2, CH), 1.21 (3H, t, J = 8.0 Hz,
CH3), 1.06 (3H, d, J = 8.0 Hz, CH3); 13C NMR δ 204.1, 137.5, 135.3,
129.3, 129.0, 39.7, 37.3, 21.4, 14.0; MS (EI): m/z =175 [M-H]-.
3-(4-Isopropylphenyl)-2-methylpropanal (1d): Oil; 1H NMR δ 9.67
(1H, s, CHO), 7.13 (2H, d, J = 8.0 Hz, ArH), 7.06 (2H, d, J = 8.0 Hz,
ArH), 3.06–3.01 (1H, dd, J = 8.0, 16 Hz, CH2a), 2.91–2.81 (H, m, CH),
2.65–2.53 (2H, m, CH2b, CH), 1.23 (6H, d, J = 4.0 Hz, CH3), 1.07 (3H,
d, J = 8.0 Hz, CH3); 13C NMR δ 204.0, 129.1, 128.8, 128.5, 45.1, 36.4,
30.3, 22.5, 13.3; MS (EI): m/z = 190 [M].
We thank Zhejiang University of Technology (ZJUT) for
financial support.
Received 29 July 2015; accepted 21 August 2015
Published online: 2 October 2015
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