MnO2/TBHP: A Combination of Reagents for Allylic Oxidation
1.77 (m, 4 H), 1.75–1.43 (m, 6 H), 1.40–1.07 (m, 3 H), 1.03 (s, 3
including benzaldehyde, cinnamaldehyde, and benzoic acid. The 1H
H), 0.88 (s, 3 H) ppm. 13C NMR (100 MHz, CDCl3): δ = 220.7, and 13C NMR spectra of isolated 24 were fully consistent with
170.3, 145.2, 124.5, 73.1, 64.0, 47.0, 44.9, 42.5, 37.9, 37.5, 37.2,
36.6, 35.7, 31.0, 27.4, 21.8, 21.2, 20.0, 18.1, 13.2 ppm. MS (ESI):
m/z = 369.1 [M + Na]+.
those reported previously.[26]
(E)-1-Phenylhex-1-en-3-one (24): Colourless oil. 1H NMR
(400 MHz, CDCl3): δ = 7.62–7.20 (m, 5 H), 7.54 (d, J = 16.2 Hz,
1 H), 6.73 (d, J = 16.2 Hz, 1 H), 2.63 (t, J = 7.4 Hz, 2 H), 1.71
(quin, J = 7.4 Hz, 2 H), 0.98 (t, J = 7.4 Hz, 3 H) ppm. 13C NMR
(100 MHz, CDCl3): δ = 200.2, 142.1, 134.7, 130.2, 128.8, 128.1,
126.4, 42.8, 17.8, 13.7 ppm. GC–MS (EI): m/z (%) = 174 (23)
[M]+, 146 (7), 131 (100), 115 (3), 103 (41), 77 (19), 51 (4).
α-Ionone Oxidation: The oxidation of racemic α-ionone (13; 20 g,
104 mmol) according to the general procedure gave unreacted α-
ionone (4.9 g, 25%), 3-keto-α-ionone (14; 11.2 g, 52%), and cis-α-
epoxy-ionone (15; 0.85 g, 4%). The 1H and 13C NMR spectra of
3-keto-α-ionone (14) were fully consistent with those reported pre-
viously,[22a] whereas cis-α-epoxy-ionone (15) was identified by GC
analysis using synthetic 15[23] as a reference standard.
Oxidation of Hept-1-ynylbenzene: The oxidation of hept-1-ynyl-
benzene (25; 8 g, 46.5 mmol) according to the general procedure
gave unreacted 25 (3.1 g, 39%), and 1-phenylhept-1-yn-3-one (26;
3-Keto-α-ionone (14): White crystals, m.p. 74–75 °C; ref.[22b] m.p.
1
4.9 g, 56%), whose H and 13C NMR spectra were fully consistent
1
75–76.5 °C. H NMR (400 MHz, CDCl3): δ = 6.67 (dd, J = 15.8,
with those reported previously.[27]
9.5 Hz, 1 H), 6.19 (d, J = 15.8 Hz, 1 H), 5.98 (s, 1 H), 2.72 (d, J =
9.5 Hz, 1 H), 2.36 (d, J = 16.9 Hz, 1 H), 2.28 (s, 3 H), 2.15 (d, J =
16.9 Hz, 1 H), 1.90 (d, J = 1.1 Hz, 3 H), 1.08 (s, 3 H), 1.01 (s, 3
H) ppm. 13C NMR (100 MHz, CDCl3): δ = 198.0, 197.3, 158.9,
143.4, 133.7, 126.9, 55.4, 47.3, 36.6, 27.9, 27.5, 27.2, 23.4 ppm.
GC–MS (EI): m/z (%) = 206 (1) [M]+, 191 (2), 164 (1), 150 (22),
135 (5), 121 (2), 108 (100), 91 (5), 77 (11).
1
1-Phenylhept-1-yn-3-one (26): Colourless oil. H NMR (400 MHz,
CDCl3): δ = 7.59–7.52 (m, 2 H), 7.47–7.32 (m, 3 H), 2.65 (t, J =
7.4 Hz, 2 H), 1.78–1.68 (m, 2 H), 1.46–1.35 (m, 2 H), 0.95 (t, J =
7.4 Hz, 3 H) ppm. 13C NMR (100 MHz, CDCl3): δ = 187.9, 132.9,
130.5, 128.5, 120.1, 90.4, 87.9, 45.2, 26.2, 22.1, 13.7 ppm. GC–MS
(EI): m/z (%) = 186 (1) [M]+, 185 (4), 171 (2), 158 (5), 144 (23),
129 (100), 115 (4), 102 (16), 75 (10).
β-Ionone Oxidation: The oxidation of β-ionone (16; 20 g,
104 mmol) according to the general procedure gave unreacted β-
ionone (0.55 g, 3%), 3-keto-α-ionone (17; 8.5 g, 40%), and β-ep-
Oxidation of (E)-(3-Ethoxyprop-1-enyl)benzene: The oxidation of
(E)-(3-ethoxyprop-1-enyl)benzene (27; 5 g, 30.8 mmol) according
to the general procedure gave ethyl cinnamate (28; 2.2 g, 40%). The
latter compound was identified by GC analysis using commercially
available 28 as a reference standard.
1
oxy-ionone (18; 4.1 g, 19%). The H and 13C NMR spectra of 4-
keto-α-ionone (17) were fully consistent with those reported pre-
viously,[8a] whereas β-epoxy-ionone (18) was identified by GC
analysis using synthetic 18[23] as a reference standard.
Oxidation of Isochroman: The oxidation of isochroman (29; 10 g,
74.6 mmol) according to the general procedure gave 1-oxo-iso-
chroman (30; 5.0 g, 45%) and 1-(tert-butylperoxy)isochroman (31;
4-Keto-β-ionone (17): White crystals, m.p. 52–53 °C; ref.[24] m.p. 53–
54 °C. 1H NMR (400 MHz, CDCl3): δ = 7.23 (dq, J = 16.5, 1.1 Hz,
1 H), 6.19 (d, J = 16.5 Hz, 1 H), 2.53 (t, J = 6.9 Hz, 2 H), 2.34 (s,
3 H), 1.89 (t, J = 6.9 Hz, 2 H), 1.80 (d, J = 1.1 Hz, 3 H), 1.19 (s,
6 H) ppm. 13C NMR (100 MHz, CDCl3): δ = 198.4, 197.2, 157.6,
140.2, 133.5, 131.5, 37.3, 35.5, 34.1, 27.9, 27.3, 13.3 ppm. GC–MS
(EI): m/z (%) = 206 (56) [M]+, 191 (13), 177 (4), 163 (100), 149
(24), 135 (28), 121 (44), 107 (14), 91 (20), 77 (11).
1
8.1 g, 49%), whose H and 13C NMR spectra were fully consistent
with those reported previously.[8a,18]
1-Oxo-isochroman (30): Colourless oil. 1H NMR (400 MHz,
CDCl3): δ = 8.08 (d, J = 7.8 Hz, 1 H), 7.53 (td, J = 7.5, 1.3 Hz, 1
H), 7.38 (t, J = 7.8 Hz, 1 H), 7.26 (d, J = 7.5 Hz, 1 H), 4.53 (t, J
= 6.0 Hz, 2 H), 3.06 (t, J = 6.0 Hz, 2 H) ppm. 13C NMR (100 MHz,
CDCl3): δ = 164.9, 139.5, 133.5, 130.2, 127.5, 127.1, 125.3, 67.2,
27.7 ppm. GC–MS (EI): m/z (%) = 148 (64) [M]+, 118 (100), 90
(68), 77 (4), 63 (11), 51 (7).
1-(tert-Butylperoxy)isochroman (31): Colourless oil. 1H NMR
(400 MHz, CDCl3): δ = 7.34 (d, J = 7.4 Hz, 1 H), 7.30–7.18 (m, 2
H), 7.13 (d, J = 7.4 Hz, 1 H), 6.04 (s, 1 H), 4.22 (td, J = 11.6,
3.3 Hz, 1 H), 3.99 (ddd, J = 11.4, 6.0, 1.4 Hz, 1 H), 3.02 (ddd, J =
16.6, 12.3, 6.0 Hz, 1 H), 2.59 (dd, J = 16.6, 2.6 Hz, 1 H), 1.35 (s, 9
H) ppm. 13C NMR (100 MHz, CDCl3): δ = 135.6, 130.4, 128.7,
128.6, 128.3, 126.1, 99.2, 80.8, 58.1, 27.8, 26.6 ppm. MS (ESI): m/z
= 245.0 [M + Na]+.
Theaspirane Oxidation: The oxidation of racemic theaspirane (19;
10 g, 1:1 diastereoisomeric mixture, 51.5 mmol) according to the
general procedure gave unreacted theaspirane (3.5 g, 35%), and
theaspirone (20; 5.3 g, 49%), whose 1H and 13C NMR spectra were
fully consistent with those reported previously.[25]
Theaspirone (20): Pale yellow oil, 1:1 mixture of diastereoisomers
(by GC and NMR analysis). 1H NMR (400 MHz, CDCl3): δ =
5.75 and 5.71 (2 m, 1 H), 4.27–4.15 (m, 1 H), 2.48–1.42 (m, 6 H),
1.98 (d, J = 1.3 Hz) and 1.96 (d, J = 1.1 Hz) (3 H), 1.31 and 1.30
(2 d, J = 6.0 Hz, 3 H), 1.07, 1.02, 1.01, and 0.98 (4 s, 6 H) ppm.
13C NMR (100 MHz, CDCl3): δ = 197.7, 197.3, 167.3, 167.3, 124.4,
124.1, 87.8, 87.7, 77.1, 76.8, 49.4, 49.1, 40.8, 39.9, 34.2, 33.5, 31.9,
23.7, 23.6, 22.9, 22.2, 20.5, 19.6, 19.5, 18.1 ppm. GC–MS (EI): m/z
(%) = 208 (Ͻ1) [M]+, 193 (2), 165 (3), 152 (100), 123 (5), 110 (83),
96 (13), 82 (12), 69 (11), 55 (9).
Oxidation of Dibenzyl Ether: The oxidation of dibenzyl ether (32;
10 g, 50.4 mmol) according to the general procedure gave unreacted
32 (0.5 g, 5%), benzyl benzoate (33; 7.3 g, 68%), and a number of
other overoxidation products, including benzaldehyde and benzoic
acid. Compound 33 was identified by GC analysis using commer-
cially available benzyl benzoate as a reference standard.
Oxidation of Isophorone: The oxidation of isophorone (21; 20 g,
144.7 mmol) according to the general procedure gave unreacted iso-
phorone (13.2 g, 66%), and 4-oxoisophorone (22; 6.1 g, 28%). The
latter compound was identified by GC analysis using commercially
available 22 as a reference standard.
Oxidation of Bibenzyl: The oxidation of bibenzyl (34; 10 g,
54.9 mmol) according to the general procedure gave unreacted 34
(7.5 g, 75%), and phenylbenzyl ketone (35; 1.65 g, 15%). The latter
compound was identified by GC analysis using commercially avail-
able 35 as a reference standard.
Oxidation of (E)-Hex-1-enylbenzene: The oxidation of (E)-hex-1-
enylbenzene (23; 6 g, 37.4 mmol) according to the general pro-
cedure gave unreacted 23 (50 mg, 1%), (E)-1-phenylhex-1-en-3-one
(24; 2.1 g, 32%), and a number of other overoxidation products,
Oxidation of Fluorene: The oxidation of fluorene (36; 10 g,
60.2 mmol) according to the general procedure gave unreacted 36
Eur. J. Org. Chem. 2015, 6472–6478
© 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
6477