296 J. Am. Chem. Soc., Vol. 120, No. 2, 1998
Freccero et al.
reported in the literature.43 The nitrate 4i was identified by comparison
with an authentic sample synthesized via an alternative pathway, as
reported below.
Due to its instability, the nitrate 4h was not characterized as such
but was hydrolyzed to the alcohol 6h44 by shaking a solution of the
crude photolyzate in ether for a few minutes (at room temperature)
with a 5% solution of NaHCO3 in water. 2-Hydroxyethyl formate and
2-hydroxyethyl acetate were identified in the crude photolyzate by
comparison of their 1H NMR and 13C NMR spectral data with literature
values.45
(CdO); IR 2956, 2839, 1754, 1611, 1513, 1304, 1255, 1163. Anal.
Calcd for C10H11ClO3: C, 55.96; H, 5.17. Found: C, 55.85; H, 5.15.
Following the procedure described above for 2, methyl 2-(4-
methoxyphenyl)-2-chloroacetate was converted quantitatively to R-car-
bomethoxy-(4-methoxybenzyl)nitrate (4i) by reaction with AgNO3 in
acetonitrile: 1H NMR 3.76 (s, 3H, OCH3), 3.79 (s, 3H, OCH3), 5.99 (s,
1H, CH), 6.90 and 7.33 (AA′BB′ system, J ) 8.9 Hz, 4H, aromatic);
13C NMR 52.9 (OCH3), 55.3 (OCH3), 81.3 (CH), 114.5 and 130.0
(aromatic, CH), 121.2 and 161.2 (aromatic, ipso), 167.8 (CdO); IR
2960, 2843, 2560, 1755, 1642, 1611, 1516, 1293, 1257, 1178. Anal.
Calcd for C10H11NO6: C, 49.80; H, 4.59; N, 5.81. Found: C, 49.70;
H, 4.50; N, 5.82.
4-Methoxybenzaldehyde (3) was identified by comparison with an
authentic sample (Aldrich).
The acetamide 7h was purified by chromatography of the crude
photolyzate on silica gel (ethyl acetate:MeOH ) 20:1), after eluting
the unreacted starting material and the alcohol 6h (cyclohexane:ethyl
acetate ) 1:1).
Photochemical Reactions in the Presence of Tetrabutylammo-
nium Nitrate. General Procedure. An acetonitrile solution (300 mL)
of CAN (329 mg, 2 mM), 1b (60 mg, 1 mM), and n-Bu4NNO3 (460
mg, 5 mM) was deaerated by flushing with nitrogen and then irradiated
for 30 min at room temperature in a water-cooled immersion well using
a 125 W medium-pressure mercury vapor lamp fitted with a Pyrex
filter. After the irradiation, water (50 mL) was added and the solution
was stirred for 1 h. Removal of the solvent under vacuum at room
temperature yielded a solid. Diethyl ether (50 mL) was added, the
mixture was shaken thoroughly, and the organic layer was washed twice
with water and dried over MgSO4. Nitrate 4b contained in the mixture
was hydrolyzed by shaking a solution in ether with a 5% solution of
NaHCO3 in water. The product 6b was purified by silica gel column
chromatography using cyclohexane-ethyl acetate (4:1) as eluent.
The other reactions were similarly carried out, and the products 6c,
6e,50 6h,44 and 1-(4-methoxyphenyl)-1,2-diphenylethanone51 were
similarly isolated.
N-[2-Methoxy-1-(4-methoxyphenyl)ethyl]acetamide (7h): yellow
1
solid (mp 110-112 °C, from MeOH); H NMR 1.95 (s, 3H, CH3),
3.25 (s, 3H, OCH3), 3.57 (d, 2H, J ) 4 Hz, OCH2), 3.69 (s, 3H, OCH3),
5.0 (dt, 1H, J ) 4 Hz, J ) 3 Hz), 6.12 (d, 1H, J ) 3 Hz, NH), 6.85
and 7.12 (AA′BB′ system, J ) 9.0 Hz, 4H, aromatic);13C NMR 23.3
(CH3), 51.8 (NCH), 55.1 (OCH3), 58.9 (OCH3), 74.8 (OCH2), 113.8,
127.8 (aromatic, CH), 131.9, 158.8 (aromatic, ipso), 169.4 (CO); IR
3339 (sharp), 3050, 1642, 1515, 1251, 1181, 1125, 1085, 1027, 825.
Anal. Calcd for C12H17NO3: C, 64.55; H, 7.67; N, 6.27. Found: C,
64.44; H, 7.60; N, 6.32.
4-Methoxybenzyl Nitrate (2). This material was obtained in
quantitative yield following a published procedure.46 A stoichiometric
amount of 4-methoxybenzyl chloride was added to a solution of AgNO3
in acetonitrile. The mixture was stirred for 10 min, AgCl was filtered
off, and the solvent was removed. The residue was a colorless oil which
decomposed at T > 90 °C: 1H NMR 3.80 (s, 3H, OCH3), 5.35 (s, 2H,
CH2ONO2), 6.89 and 7.31 (AA′BB′ system, J ) 9.0 Hz, 4H, aromatic);
13C NMR 55.3 (OCH3), 74.9 (CH2), 114.2 and 131.1 (aromatic, CH),
124.0 and 160.6 (aromatic, ipso); IR 2962, 2840, 2553, 1628, 1516,
1280, 1253, 860. Anal. Calcd for C8H9NO4: C, 52.46; H, 4.95; N,
7.65. Found: C, 52.35; H, 4.91; N, 7.59.
Reaction in the case of 1j was slow, and only part conversion was
achieved. Nitrate 4j was identified in the crude reaction mixture, after
1
workup as described above, by H NMR: 1.05 (s, 9H, tBu), 3.84 (s,
3H, OCH3), 5.40 (s, 1H), 6.90 and 7.26 (AA′BB′ system, J ) 9.0 Hz,
4H, aromatic).
2-Methoxy-1-(4-methoxyphenyl)-2-methylpropan-1-ol (6b): col-
1
orless oil; H NMR 1.03 (s, 3H, CH3), 1.10 (s, 3H, CH3), 3.05 (br s,
1H, OH), 3.3 (s, 3H, OCH3), 3.80 (s, 3H, OCH3), 4.55 (s, 1H, CH
benzylic), 6.85 and 7.30 (AA′BB′ system, J ) 9.0 Hz, 4H, aromatic);
13C NMR 18.1 (CH3), 20.9 (CH3), 49.4 (OCH3), 55.1 (OCH3), 78.1
(C-OMe), 78.7 (benzylic CH), 112.9 and 128.7 (aromatic, CH), 132.0
and 158.9 (aromatic, ipso); IR 3500, 2977, 2837, 1612, 1585, 1248,
1069, 817. Anal. Calcd for C12H18O3: C, 68.54; H, 8.63. Found: C,
68.42; H, 8.51.
r-Carbomethoxy-4-methoxybenzyl Nitrate (4i). Methyl 4-meth-
oxymandelate,47 prepared from 4-methoxymandelic acid following a
standard esterification procedure,48 was obtained in quantitative yield
as a colorless liquid: bp 100-102 °C, 0.05 mmHg [lit.47 mp 32-34
1
°C, lit.48 bp(8 mmHg) 162 °C]; H NMR 3.39 (s, 1H, OH), 3.74 (s,
3H, OCH3), 3.79 (s, 3H, OCH3), 5.11 (s, 1H, CH), 6.87 and 7.30
(AA′BB′ system, J ) 8.9 Hz, 4H, aromatic); 13C NMR 52.9 (OCH3),
55.2 (OCH3), 72.4 (CH), 114.0 and 127.8 (aromatic, CH), 130.4 and
159.7 (aromatic, ipso), 174.3 (CdO); IR 3443 (br), 2967, 2841, 1728,
1611, 1512, 1215, 1180.
2-Methoxy-1-(4-methoxyphenyl)-2,2-diphenylethanol (6c): color-
1
less oil; H NMR 2.65 (br s, 1H, OH), 3.05 (s, 3H, OCH3), 3.75 (s,
3H, OCH3), 5.60 (s,1H, benzylic H), 6.60 and 6.70 (AA′BB′ system,
J ) 9.0 Hz, 4H, aromatic), 7.15-7.35 (m, 10H, aromatic); 13C NMR
50.5 (OCH3), 54.8 (OCH3), 76.9 (benzylic CH), 83.2 (C quaternary),
113.0, 126.6, 127.3, 127.6 and 130.3 (aromatic, CH), 130.7, 144.8 and
158.7 (aromatic, ipso). Anal. Calcd for C22H22O3: C, 79.02; H, 6.63.
Found: C, 78.89; H, 6.60.
On the basis of a published synthesis of ethyl 2-(chlorophenyl)-
acetate,49 methyl 2-(4-methoxyphenyl)-2-chloroacetate was synthesized
from methyl 4-methoxymandelate. To a stirred CH2Cl2 solution (25
mL) of methyl 4-methoxymandelate (1.7 g, 8.67 mmol) was added
dropwise a CH2Cl2 solution (25 mL) of SOCl2 (0.7 mL, 9 mmol) over
10 min. The solution was heated under reflux for 2 h and then cooled
to room temperature, and water (10 mL) was added. After the solution
was stirred for 20 min, the organic layer was washed three times with
water and dried. Removal of the solvent under vacuum gave methyl
2-(4-methoxyphenyl)-2-chloroacetate (1.45 g, 78%) as a colorless
liquid: bp 85-89 °C, 0.05 mmHg; 1H NMR 3.75 (s, 3H, OCH3), 3.79
(s, 3H, OCH3), 5.32 (s, 1H, CH), 6.87 and 7.39 (AA′BB′ system, J )
8.9 Hz, 4H, aromatic); 13C NMR 53.2 (OCH3), 55.3 (OCH3), 58.7 (CH),
114.2 and 129.3 (aromatic, CH), 127.7 and 160.3 (aromatic, ipso), 169.0
2-Methoxy-1-(4-methoxyphenyl)ethanol (6h):44 colorless liquid; 1H
NMR 2.70 (br s, 1H, OH), 3.40 (dd, J ) 3 Hz, J ) 8 Hz, 1H), 3.45 (s,
3H, OCH3), 3.52 (dd, J ) 3 Hz, J ) 8 Hz, 1H), 3.79 (s, 3H, OCH3),
4.82 (dd, J ) 8 Hz, 1H), 6.85 and 7.27 (AA′BB′ system, J ) 9.0 Hz,
1
4H, aromatic) (in agreement with the H NMR spectrum reported in
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