Reaction of singlet oxygen with enolic tautomers of 1-aryl-2-methyl 1,3-diketones

Article abstract of DOI:10.1039/a705448c

The 1-(2′,4′,6′-trialkylphenyl)-2-methyl 1,3-diketones 6 exist in the enol form in solution, and on reaction with singlet oxygen in acetonitrile give products arising from hydrogen abstraction from both the enolic hydroxy and the 2-methyl groups by the singlet oxygen; namely, the 2-hydroperoxy 1,3-diketones 7, the 2-methylene 1,3-diketones 8 and the epoxy ketones 9. The 2-hydroperoxy 1,3-diketones 7 readily undergo deoxygenation by triphenylphosphine to give the 2-hydroxy 1,3-diketones 12. In the reaction of 6 in methanol or ethanol, the initially formed enedione 8 reacts with the solvent to give the corresponding Michael adducts 10 and 11.

Full text of DOI:10.1039/a705448c

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Reaction of singlet oxygen with enolic tautomers of 1-aryl-2-methyl
1,3-diketones
Michikazu Yoshioka,*,a Kyoko Hashimoto,a Tetsuo Fukuharaa and Tadashi
Hasegawab
a Department of Chemistry, Saitama University, Shimo-okubo, Urawa, Saitama 338, Japan
b Department of Chemistry, Tokyo Gakugei University, Nukuikitamachi, Koganei, Tokyo 184,
Japan
The 1-(2Ј,4Ј,6Ј-trialkylphenyl)-2-methyl 1,3-diketones 6 exist in the enol form in solution, and on reaction
with singlet oxygen in acetonitrile give products arising from hydrogen abstraction from both the enolic
hydroxy and the 2-methyl groups by the singlet oxygen; namely, the 2-hydroperoxy 1,3-diketones 7, the
2-methylene 1,3-diketones 8 and the epoxy ketones 9. The 2-hydroperoxy 1,3-diketones 7 readily undergo
deoxygenation by triphenylphosphine to give the 2-hydroxy 1,3-diketones 12. In the reaction of 6 in
methanol or ethanol, the initially formed enedione 8 reacts with the solvent to give the corresponding
Michael adducts 10 and 11.
Singlet oxygen shows a diversity of reactions with substrates.1
Since it is electrophilic, the reactions with α,β-unsaturated car-
O
O
O
O
OOH
H
O
O
O
–H2O
bonyl compounds are often slow, but show marked regioselec-
tivity; singlet oxygen abstracts hydrogen from an alkyl group
geminal to the carbonyl group so that the entering oxygen
bonds to the carbon away from the carbonyl group. Much work
has been carried out in recent years on such regioselective
singlet oxygenation of α,β-unsaturated ketones,2 aldehydes,3
acids,3b,4 and esters.3b,4b,5 However, the reactions of singlet
oxygen with enolic tautomers of 1,3-dicarbonyl compounds,
β-hydroxy-α,β-unsaturated carbonyls, have received little atten-
tion. Wasserman and Pickett reported that enolic tautomers of
1,3-dicarbonyl compounds reacted with singlet oxygen to pro-
duce 1,2,3-triketones6 in the presence of fluoride ion which
enhances the nucleophilicity of enols.7 They postulated a 2-
hydroperoxy 1,3-diketone as an intermediate in this reaction.
Ensley et al. reported the regioselective photooxygenation of
the β-alkoxy cyclic enones 1 to give the unsaturated hemi-
perketals 2 which decomposed to the epoxide 3.8 We have
recently reported that the enolic tautomers 4 of acyl- and
alkoxycarbonyl-benzocycloalkenones reacted with singlet
oxygen to give 2-hydroperoxy 1,3-dicarbonyl compounds 59
(Scheme 1). We report here that the reaction of the enolic
tautomers 6 of 1-aryl-2-methyl 1,3-diketones in acetonitrile
with singlet oxygen gives the 2-hydroperoxy 1,3-diketones 7, the
2-methylene 1,3-diketones 8 and the epoxy ketones 9. In the
reaction of 6 in methanol or ethanol, the enedione 8 reacted
with the solvent to give the corresponding Michael adducts 10
and 11.
O
R
H
F–
O
OOH
O
O
O
O
OMe
O
MeO
1O2
R
R
1
2
3
OH
O
O
OOH
O
1O2
R
R
(CH2)n
(CH2)n
4
5
Scheme 1
corresponding hydroperoxy ketones 7b–f, the enediones 8b–f
and the epoxy ketones 9d–f. The epoxy ketones 9b and 9c could
not be detected. The reaction of 6 with singlet oxygen in alco-
holic solvents gave different products from those in acetonitrile.
Irradiation of a methanolic or ethanolic solution of 6a–c,e,f
under the same conditions gave 10a–c,e,f or 11a as the major
product, along with the hydroperoxy ketones 7a–c,e,f and the
epoxy ketones 9a,b,e,f (Scheme 2). The enedione 8 could not be
detected. The structures of the products were assigned on the
basis of their analytical and spectral data. The 1H NMR spec-
Results and discussion
The 1-aryl-2-methyl 1,3-diketones were prepared by the reac-
tion of 2Ј,4Ј,6Ј-trialkylpropiophenones with aldehydes, fol-
lowed by oxidation of the resulting ketols.10 The products were
obtained as the enol form 6 after passage through a silica gel
column followed by distillation or recrystallization.11
Irradiation at room temperature with a tungsten–halogen
lamp (K2CrO4 solution filter) of 1-(2Ј,4Ј,6Ј-triisopropylphenyl)-
2-methylbutane-1,3-dione 6a in acetonitrile through which air
was bubbled in the presence of Methylene Blue as a sensitizer
gave the hydroperoxy ketone 7a, the enedione 8a and the epoxy
ketone 9a, in 35, 42 and 6% yield, respectively. Photooxidation
of the compounds 6b–f under the same conditions also gave the
trum of 7 showed a singlet at δH 8.9–9.9 due to OOH. The 13
C
NMR spectrum of 7 showed two carbonyl carbons in the range
δC 200–211 and a quaternary carbon due to C-2 at δC 96–99.
Deoxygenation of 7a,c–e with triphenylphosphine gave the cor-
responding alcohols 12a,c–e which showed a hydroxy 1H NMR
peak at δH 4.4–4.8. The 1H NMR spectrum of 8 showed an AB
pair at δH 5.8–5.9 and 6.4–6.6 due to two olefinic protons. The
13C NMR spectrum of 8 showed two peaks due to carbonyl
carbons in the range δC 198–207 and eight aromatic and olefinic
sp2 carbons in the range δC 121–151. The compounds 8d–f were
isolated as oils of high purity as determined on the basis of
their NMR spectra. However, distillation for microanalysis
J. Chem. Soc., Perkin Trans. 1, 1998
283

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R1
OH
R1
O
R1
O
O
R1
O
O
R1
O
O
O
R1
OH
O
R2
R2
R2
R2
R2
OR3
i
+
+
+
Me OOH
R1
Me
R1
R1
R1
R1
R1
R1
R1
R1
(R3 = Me)
6
7
8
9
10
11 (R3 = Et)
ii
R1
O
O
R2
R1 = Pri, R2 = Me
1 = R2 = Me
b
e
c
f
R
1 = Pri, R2 = Et
R1 = Me, R2 = Et
a
R
R
1 = R2 = Pri
1 = Me, R2 = Pri
Me OH
R1
R
d
R1
12
Scheme 2 Reagents: i, 1O2/MeCN, MeOH or EtOH; ii, PPh3
could not be achieved because they underwent thermal decom-
position. The compounds 8a–c were obtained as crystals. The
compounds 10a–c,e and 11a were obtained as oils, but distill-
ation for microanalysis could not be achieved because they were
orients towards the methyl and aryl side would be also expected
to be transformed into the hydroperoxide 13 by a hydrogen shift
from the methyl group to the negative oxygen. Fukui has sug-
gested by MO calculation that the terminal oxygen atom in the
perepoxide from vinyl alcohol and singlet oxygen orients
towards the hydroxy side.13 He has also suggested that the per-
epoxide from aryl alkene and singlet oxygen has its terminal
oxygen atom orientated towards the aromatic side. The regio-
selective 1O2 ene reaction of alkoxy alkenes14 and aryl alkenes5,14
matches the expected geometry of the perepoxide intermediate.
Since the enols 6 have hydroxy and aryl groups on C-1, both A
and B must intervene. Recently, Adam et al.15 have reported
that the singlet oxygenation of chiral allylic alcohols proceeded
with a high degree of regio- and diastereo-selectivity, and
explained this selectivity in terms of coordination of the
transformed into 8a–c,e by loss of alcohols (Scheme 3). The 13
C
NMR spectra of 10a–c,e,f and 11a showed eight aromatic and
olefinic sp2 carbons, indicating that they existed in the enol
form.
Pri
O
O
Pri
OH
Pri
O
Pri
Pri
OMe
i
ii
Pri
Pri
Pri
8c
10c
1
hydroxy functionality with the incoming O2. They suggested
Scheme 3 Reagents: i, MeOH; ii, heat
that the reaction of allylic alcohols with singlet oxygen proceeds
by an initial interaction of the nucleophilic oxygen atom of
these substrates with the electrophilic singlet oxygen, and that
the negatively charged terminal oxygen atom of the sub-
sequently formed perepoxide interacts with the hydroxy group
through hydrogen bonding. In the perepoxide A, the hydroxy
group can interact with the terminal oxygen through hydrogen
bonding by way of a five-membered ring. The reaction of sing-
let oxygen with α,β-unsaturated carbonyl compounds generally
shows geminal selectivity.2–5 The products expected by the gem-
inal selectivity in the reaction of the enols 6 and singlet oxygen
are 8, 9, 10 and 11. The formation of 7 may be attributed to the
hydrogen bonding in the perepoxide intermediate A.
As seen from Table 1, the yield of the epoxide 9 was higher
with R1 = Me than with R1 = Pri and decreased with bulky R2.
This result may be ascribed to steric factors. As already
stated, the epoxide 9 is probably formed by the reaction of
the enedione 8 with hydrogen peroxide. The more crowded
enediones 8a–c would be less reactive to hydrogen peroxide
than the less crowded 8d–f. In 8d–f, 8f is most crowded and
therefore least reactive. In the reaction of 6d–f in acetonitrile,
the yield of the hydroperoxy ketone 7 was dependent on R2.
The yield decreased in the order of 7f, 7e and 7d, while the
total yield of 8 and 9 was the same regardless of R2. Of the
compounds 7d–f, 7d is the least crowded and probably most
unstable because of its relative freedom from steric protection.
The lower yield of 7d compared with those of 7e and 7f is
probably ascribed to partial decomposition during the isol-
ation procedure.
Photooxidation of the enols 6 probably takes place through
the ene reaction with 1O2, where oxygen abstracts hydrogen
from either the enolic hydroxy group or the 2-methyl group. The
hydroperoxy ketone 7 would arise as a result of hydrogen
abstraction from the enolic hydroxy group. The compounds 8,
9, 10 and 11 would be produced via the hydroperoxide 13
formed through hydrogen abstraction from the 2-methyl group.
The hydroperoxide 13 would decompose to afford the enedione
8 with loss of hydrogen peroxide. The hydrogen peroxide thus
generated would react with 8 to yield the epoxide 9. The com-
pound 8c reacted readily with methanol at room temperature to
give 10c. Therefore, the enedione 8 probably reacts in an alco-
holic solvent to give 10 or 11. The hydroperoxy ketones 7 and 13
probably arise from different perepoxide intermediates.12 Since
hydroxy and carbonyl groups in the starting enol 6 should be cis
owing to hydrogen bonding, two possible perepoxide inter-
mediates may intervene, namely the form A and the form B
(Scheme 4). Both perepoxides A and B would be expected to
open to a stabilized benzilic cation C, which after proton shift
gives 7. The perepoxide B in which the terminal oxygen atom
Ar
Me
Ar
Me
+
O
+
O
COR2
HO
COR2
O
O
7
H
O
-
A
-
C
i
+
6
The hydroperoxy ketone 7 with the same substituents was
formed in slightly higher yield in acetonitrile than in methanol,
while the total yield of the products arising from the perepoxide
B (8 and 9 in acetonitrile; 9 and 10 in methanol) was lower in
acetonitrile than in methanol. The solvent effect on the singlet
oxygenation of allylic alcohols has been reported.12i,15b The
hydrogen bonding between the solvent and the hydroxy group
-
O
H
OOH
O
10,11
9
HO
Ar
iii
iv
+
Ar
HO
ii
O
8
R2
COR2
B
13
Scheme 4 Conditions: i, 1O2; ii, loss of H2O2; iii, RЈOH; iv, H2O2
284
J. Chem. Soc., Perkin Trans. 1, 1998

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Table 1 Product distribution of the Methylene Blue-sensitized photooxidation of 6a
Yield(%)c
Compound 6
Solvent
Conversion (%)b
7
8
9
10
11
a
b
c
d
e
f
a
a
b
c
e
f
MeCN
MeCN
MeCN
MeCN
MeCN
MeCN
MeOH
EtOH
MeOH
MeOH
MeOH
MeOH
97
91
100
100
95
100
91
93
35
37
36
18
28
32
23
15
33
37
25
27
42
51
55
27
31
37
—
—
—
—
—
—
6
—
—
—
—
—
—
61
—
59
52
40
47
—
—
—
—
—
—
—
72
—
—
—
—
—
—
16
10
7
6
10
3
94
100
94
—
6
7
100
a A solution of 6 (500 mg) in a solvent (100 cm3) in the presence of Methylene Blue (ca. 10 mg) was irradiated with a 100 W tungsten–halogen lamp
through a K2CrO4 filter solution. b Based on the amount of unchanged starting material recovered after chromatography. c Based on converted
starting material.
in a perepoxide intermediate affects product distribution. The
internal hydrogen bond in the perepoxide A would be lessened
in polar solvents. Hence, structure A should become less
decisive relative to B and the yield of 7 should decrease. Metha-
nol is slightly more effective than acetonitrile.12i
(6 H, d, J 7, 4Ј-CHMe2), 1.81 (3 H, s, 2-Me), 2.29 (1 H, sept,
J 7), 2.52 (1 H, sept, J 7) and 2.86 (1 H, sept, J 7) (3 × CHMe2),
2.71 (1 H, dq, J 19 and 7) and 2.92 (1 H, dq, J 19 and 7) (4-H2),
6.98 (1 H, s) and 7.00 (1 H, s) (ArH) and 8.94 (1 H, s, OOH);
δC(100 MHz) 7.7 (q), 20.9 (q), 23.0 (q), 23.1 (q), 23.8 (2q), 25.2
(2q) (C-5, 2-Me and 3 × CHMe2), 30.8 (t, C-4), 31.5 (d), 32.3
(d) and 34.2 (d) (3 × CHMe2), 98.9 (s, C-2), 121.1 (d), 121.2 (d),
134.1 (s), 144.7 (s), 144.8 (s) and 150.3 (s) (ArC), 206.0 (s) and
Experimental
Mps are uncorrected and bps are oven temperatures in Kugel-
rohr distillation. IR spectra were recorded on a Hitachi 270-50
spectrometer for solutions in CCl4. 1H NMR spectra were
obtained with a Bruker AC 200 or a Bruker AM 400 spec-
trometer with CDCl3 as a solvent. Tetramethylsilane was used
as an internal standard and J values are given in Hz. 13C NMR
spectra were measured on a Bruker AC 200 or a Bruker AM
400 spectrometer with CDCl3 as a solvent. Column chroma-
tography was performed with Merck Kieselgel 60. A 100 W
tungsten–halogen lamp was used as an irradiation source. Start-
ing compounds 6a–f were prepared by previously reported
methods.10
206.9 (s) (2 × C᎐O).
᎐
2-Hydroperoxy-1-(2Ј,4Ј,6Ј-triisopropylphenyl)-2,4-dimethyl-
pentane-1,3-dione 7c. Mp 100–102 ЊC (from pentane) (Found:
C, 72.8; H, 9.5. C22H34O4 requires C, 72.9; H, 9.5%); νmax/cmϪ1
3460br (OOH), 1740 (C᎐O) and 1700 (C᎐O); δ (400 MHz) 1.08
᎐
᎐
H
(3 H, d, J 7), 1.13 (3 H, d, J 7), 1.15 (3 H, d, J 7), 1.17 (3 H, d,
J 7), 1.19 (3 H, d, J 7), 1.24 (6 H, d, J 7) and 1.31 (3 H, d, J 7)
(5-H3, 4-Me and 3 × CHMe2), 1.81 (3 H, s, 2-Me), 2.41 (1 H,
sept, J 7), 2.57 (1 H, sept, J 7), 2.88 (1 H, sept, J 7) and 3.52
(1 H, sept, J 7) (3 × ArCHMe2 and 4-H), 6.98 (1 H, s) and 7.01
(1 H, s) (ArH) and 8.89 (1 H, s, OOH); δC(100 MHz) 20.1 (2q),
20.8 (q), 22.9 (q), 23.2 (q), 23.8 (2q), 25.1 (2q) (C-5, 4-Me, 2-Me
and 3 × CHMe2), 31.4 (d), 32.1 (d), 34.2 (d) and 35.4 (d)
(4 × CHMe2), 98.6 (s, C-2), 121.1 (d) and 121.3 (d), 134.5 (s),
144.8 (s), 145.0 (s) and 150.4 (s) (ArC), 206.4 (s) and 211.4 (s)
General procedure for the photooxidation of 6
A solution of 6 (500 mg) in acetonitrile, methanol or ethanol
(100 cm3) through which air was bubbled in the presence of
Methylene Blue (10–15 mg) was irradiated with a 100 W
tungsten–halogen lamp through an aqueous solution of
K2CrO4 (0.27 g dmϪ3) and Na2CO3 (2 g dmϪ3) for 3–15 h. The
mixture was then evaporated under reduced pressure, and
the residue was chromatographed on silica gel [hexane–ethyl
acetate (8:1 to 12:1)] to give compounds 7–11.
(2 × C᎐O).
᎐
2-Hydroperoxy-2-methyl-1-(2Ј,4Ј,6Ј-trimethylphenyl)butane-
1,3-dione 7d.† νmax/cmϪ1 3480br (OOH), 1740 (C᎐O) and 1700
᎐
(C᎐O); δ (200 MHz) 1.78 (3 H, s, 2-Me), 2.13 (6 H, s), 2.27 (3
᎐
H
H, s) and 2.40 (3 H, s) (3 × ArMe and 4-H3), 6.82 (2 H, s, ArH)
and 8.95 (1 H, s, OOH); δC(50 MHz) 19.7 (2q), 20.2 (q), 20.9 (q)
and 25.6 (q) (5 × Me), 98.2 (s, C-2), 128.4 (2d), 133.5 (2s), 136.5
2-Hydroperoxy-1-(2Ј,4Ј,6Ј-triisopropylphenyl)-2-methyl-
butane-1,3-dione 7a. Mp 87–88 ЊC (from pentane) (Found: C,
71.9; H, 9.1. C20H30O4 requires C, 71.8; H, 9.0%); νmax/cmϪ1
3450br (OOH), 1740 (C᎐O) and 1700 (C᎐O); δ (400 MHz) 1.10
(s) and 139.0 (s) (ArC), 204.1 (s) and 205.6 (s) (2 × C᎐O).
᎐
2-Hydroperoxy-2-methyl-1-(2Ј,4Ј,6Ј-trimethylphenyl)pentane-
1,3-dione 7e. Mp 74–75 ЊC (from pentane) (Found: C, 68.1; H,
7.7. C15H20O4 requires C, 68.2; H, 7.6%); νmax/cmϪ1 3460br
᎐
᎐
H
(3 H, d, J 7), 1.14 (3 H, d, J 7), 1.19 (3 H, d, J 7) and 1.32 (3 H,
d, J 7) (2Ј-CHMe2 and 6Ј-CHMe2), 1.24 (6 H, d, J 7, 4Ј-
CHMe2), 1.80 (3 H, s, 2-Me), 2.36 (1 H, sept. J 7), 2.54 (1 H,
sept, J 7) and 2.88 (1 H, sept, J 7) (3 × CHMe2), 2.41 (3 H, s,
4-H3), 6.99 (1 H, s) and 7.00 (1 H, s) (ArH) and 8.90 (1 H, s,
OOH); δC(100 MHz) 20.8 (q), 23.0 (q), 23.1 (q), 23.8 (2q), 25.2
(2q) and 25.7 (q) (C-4, 2-Me and 3 × CHMe2), 31.5 (d), 32.2 (d)
and 34.2 (d) (3 × CHMe2), 98.7 (s, C-2), 121.1 (d), 121.3 (d),
134.1 (s), 144.8 (s), 144.9 (s) and 150.4 (s) (ArC), 204.2 (s) and
(OOH), 1740 (C᎐O) and 1700 (C᎐O); δ (200 MHz) 1.08 (3 H, t,
᎐ ᎐
H
J 7, 5-H3), 1.76 (3 H, s, 2-Me), 2.10 (6 H, s) and 2.26 (3 H, s)
(3 × ArMe), 2.6–3.0 (2 H, m, 4-H2), 6.80 (2 H, s, ArH) and 9.13
(1 H, s, OOH); δC(50 MHz) 7.4 (q, C-5), 19.7 (2q), 20.4 (q) and
20.9 (q) (3 × ArMe and 2-Me), 30.9 (t, C-4), 98.3 (s, C-2), 128.4
(2d), 133.4 (2s), 136.4 (s) and 138.9 (s) (ArC), 205.8 (s) and
206.8 (s) (2 × C᎐O).
᎐
2-Hydroperoxy-2,4-dimethyl-1-(2Ј,4Ј,6Ј-trimethylphenyl)-
pentane-1,3-dione 7f. Mp 64–65 ЊC (from pentane) (Found: C,
68.8; H, 8.0. C16H22O4 requires C, 69.0; H, 8.0%); νmax/cmϪ1
205.9 (s) (2 × C᎐O).
᎐
2-Hydroperoxy-1-(2Ј,4Ј,6Ј-triisopropylphenyl)-2-methyl-
pentane-1,3-dione 7b. Mp 74–75 ЊC (from pentane) (Found: C,
72.5; H, 9.1. C21H32O4 requires C, 72.4; H, 9.3%); νmax/cmϪ1
3460br (OOH), 1740 (C᎐O) and 1700 (C᎐O); δ (200 MHz) 1.14
᎐ ᎐
H
(3 H, d, J 7) and 1.17 (3 H, d, J 7) (5-H3 and 4-Me), 1.81 (3 H, s,
2-Me), 2.15 (6 H, s) and 2.27 (3 H, s) (3 × ArMe), 3.48 (1 H,
3460br (OOH), 1730 (C᎐O) and 1700 (C᎐O); δ (400 MHz) 1.09
᎐
᎐
H
(3 H, d, J 7), 1.13 (3 H, d, J 7), 1.18 (3 H, d, J 7) and 1.32 (3 H,
d, J 7) (2Ј-CHMe2 and 6Ј-CHMe2), 1.10 (3 H, t, J 7, 5-H3), 1.24
† Compounds 7d, 8d–f and 12d were obtained as oils which
decomposed on distillation.
J. Chem. Soc., Perkin Trans. 1, 1998
285

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sept, J 7, 4-H), 6.83 (2 H, s, ArH) and 8.89 (1 H, s, OOH); δC(50
MHz) 20.0 (2q), 20.2 (2q), 20.7 (q) and 21.0 (q) (6 × Me), 35.5
(d, C-4), 98.2 (s, C-2), 128.6 (2d), 133.7 (2s), 136.8 (s) and 139.1
6) and 3.11 (1 H, d, J 6) (4-H2) and 6.99 (2 H, s) (ArH); δC(50
MHz) 23.8 (2q), 24.0 (2q), 24.4 (2q) and 27.8 (q) (3 × CHMe2
and C-1), 31.5 (2d) and 34.3 (d) (3 × CHMe2), 51.5 (t, C-4), 64.2
(s, C-3), 120.9 (2d), 131.1 (s), 145.7 (2s), 150.8 (s) (ArC), 200.7
(s) (ArC), 206.2 (s) and 211.0 (s) (2 × C᎐O).
᎐
1-(2Ј,4Ј,6Ј-Triisopropylphenyl)-2-methylenebutane-1,3-dione
(s) and 204.0 (s) (2 × C᎐O).
1,2-Epoxy-2-(2Ј,4Ј,6Ј-triisopropylbenzoyl)pentan-3-one
᎐
8a. Mp 71–73 ЊC (from pentane) (Found: C, 79.9; H, 9.5.
9b.
C20H28O2 requires C, 80.0; H, 9.4%); νmax/cmϪ1 1720 (C᎐O) and
Mp 75–76 ЊC (from pentane) (Found: C, 76.4; H, 9.1. C21H30O3
᎐
1690 (C᎐O); δ (400 MHz) 1.19 (12 H, d, J 7) and 1.26 (6 H, d,
requires C, 76.3; H, 9.2%); νmax/cmϪ1 1730 (C᎐O) and 1690
᎐
᎐
H
J 7) (3 × CHMe2), 2.55 (3 H, s, 4-H3), 2.68 (2 H, sept, J 7) and
2.70 (1 H, sept, J 7) (3 × CHMe2), 5.92 (1 H, s) and 6.60 (1 H, s)
(C᎐O); δ (200 MHz) 1.13 (3 H, t, J 7, 5-H ), 1.20 (6 H, d, J 7),
᎐
H 3
1.24 (6 H, d, J 7) and 1.25 (6 H, d, J 7) (3 × CHMe2), 2.71 (2 H,
sept, J 7) and 2.88 (1 H, sept, J 7) (3 × CHMe2), 2.74 (2 H, q, J
7, 4-H2), 2.98 (1 H, d, J 6) and 3.08 (1 H, d, J 6) (1-H2) and 6.99
(2 H, s, ArH); δC(50 MHz) 7.0 (q, C-5), 23.8 (2q), 24.0 (2q) and
24.4 (2q) (3 × CHMe2), 31.5 (2d) and 34.3 (d) (3 × CHMe2),
33.5 (t, C-4), 51.4 (t, C-1), 64.1 (s, C-2), 120.8 (2d), 131.1 (s),
145.7 (2s) and 150.7 (s) (ArC), 203.6 (s) and 204.3 (s)
(AB-pair, ᎐CH ) and 7.02 (2 H, s) (ArH); δ (100 MHz) 23.9
᎐
2
C
(2q), 24.1 (4q) and 30.2 (q) (3 × CHMe2 and C-4), 31.0 (2d) and
34.3 (d) (3 × CHMe2), 121.1 (2d), 134.0 (s), 145.0 (2s), 150.3 (s)
and 150.5 (s) (ArC and C-2), 135.6 (t, ᎐CH ), 199.0 (s) and
᎐
2
200.4 (s) (2 × C᎐O).
᎐
1-(2Ј,4Ј,6Ј-Triisopropylphenyl)-2-methylenepentane-1,3-dione
8b. Mp 70–71 ЊC (from pentane) (Found: C, 80.0; H, 9.7.
(2 × C᎐O).
᎐
C21H30O2 requires C, 80.2; H, 9.6%); νmax/cmϪ1 1700 (C᎐O)
3,4-Epoxy-3-(2Ј,4Ј,6Ј-trimethylbenzoyl)butan-2-one 9d. Bp
95 ЊC at 0.5 mmHg (Found: C, 72.3; H, 7.0. C14H16O3 requires
C, 72.4; H, 6.9%); νmax/cmϪ1 1730 (C᎐O) and 1700 (C᎐O);
δH(200 MHz) 2.23 (6 H, s), 2.27 (3 H, s) and 2.39 (3 H, s)
(3 × ArMe and 1-H3), 2.97 (1 H, d, J 6) and 3.15 (1 H, d, J 6)
(4-H2) and 6.83 (2 H, s, ArH); δC(50 MHz) 19.1 (2q), 21.0 (q)
and 27.3 (q) (3 × ArMe and C-1), 51.7 (t, C-4), 63.7 (s, C-3),
128.4 (2d), 133.1 (s), 134.8 (2s) and 139.7 (s) (ArC), 200.4 (s)
᎐
and 1670 (C᎐O); δ (400 MHz) 1.17 (3 H, t, J 7, 5-H ), 1.18
᎐
H
3
(12 H, d, J 7) and 1.26 (6 H, d, J 7) (3 × CHMe2), 2.69 (2 H,
sept, J 7) and 2.90 (1 H, d, J 7) (3 × CHMe2), 2.92 (2 H, q,
᎐
᎐
J 7, 4-H ), 5.89 (1 H, s) and 6.52 (1 H, s) (AB-pair, ᎐CH )
᎐
2
2
and 7.01 ( 2 H, s, ArH); δC(100 MHz) 7.7 (q), 23.9 (2q) and
24.1 (4q) (C-5 and 3 × CHMe2), 31.5 (2d) and 34.3 (d)
(3 × CHMe2), 36.0 (t, C-4), 121.0 (2d), 134.0 (s), 145.0 (2s),
150.2 (s) and 150.9 (s) (ArC and C-2), 134.8 (t, ᎐CH ), 200.5
and 202.8 (s) (2 × C᎐O).
᎐
᎐
2
(s) and 202.5 (s) (2 × C᎐O).
1-(2Ј,4Ј,6Ј-Triisopropylphenyl)-2-methylene-4-methylpentane-
1,2-Epoxy-2-(2Ј,4Ј,6Ј-trimethylbenzoyl)pentan-3-one 9e. Bp
84 ЊC at 0.3 mmHg (Found: C, 73.3; H, 7.2. C15H18O3 requires
C, 73.2; H, 7.4%); νmax/cmϪ1 1730 (C᎐O) and 1700 (C᎐O);
δH(200 MHz) 1.11 (3 H, t, J 7, 5-H3), 2.22 (6 H, s) and 2.26 (3 H,
s) (3 × ArMe), 2.72 (2 H, q, J 7, 4-H2), 2.94 (1 H, d, J 6) and
3.12 (1 H, d, J 6) (1-H2) and 6.82 (2 H, s, ArH); δC(50 MHz) 6.9
(q, C-5), 19.1 (2q) and 21.0 (q) (3 × ArMe), 33.1 (t, C-4), 51.6
(t, C-1), 63.7 (s, C-2), 128.3 (2d), 133.1 (s), 134.7 (2s) and 139.6
᎐
1,3-dione 8c. Mp 71–72 ЊC (from pentane) (Found: C, 80.7; H,
᎐
᎐
9.8. C22H32O2 requires C, 80.4; H, 9.8%); νmax/cmϪ1 1700 (C᎐O)
᎐
and 1670 (C᎐O); δ (400 MHz) 1.18 (18 H, d, J 7) and 1.26 (6 H,
᎐
H
d, J 7) (5-H3, 4-Me and 3 × CHMe2), 2.72 (2 H, sept, J 7), 2.90
(1 H, sept, J 7) and 3.27 (1 H, sept, J 7) (3 × CHMe2 and 4-H),
5.87 (1 H, s) and 6.37 (1 H, s) (AB-pair, ᎐CH ) and 7.02 (2 H, s,
᎐
2
ArH); δC(100 MHz) 18.0 (2q), 23.9 (2q) and 24.1 (4q) (C-5,
4-Me and 3 × CHMe2), 31.0 (2d), 34.3 (d) and 39.7 (d)
(4 × CHMe2), 121.0 (2d), 133.8 (s ϩ t), 145.1 (2s), 150.2 (s) and
151.3 (s) (ArC, C-2 and ᎐CH ), 200.4 (s) and 207.0 (s)
(s) (ArC) and 203.2 (2s) (2 × C᎐O).
1,2-Epoxy-4-methyl-2-(2Ј,4Ј,6Ј-trimethylbenzoyl)pentan-3-
᎐
one 9f. Bp 118 ЊC at 0.5 mmHg (Found: C, 73.9; H, 7.7.
C16H20O3 requires C, 73.8; H, 7.7%); νmax/cmϪ1 1735 (C᎐O) and
᎐
᎐
2
(2 × C᎐O).
1705 (C᎐O); δ (200 MHz) 1.12 (3 H, d, J 7) and 1.20 (3 H, d, J
᎐
᎐
H
2-Methylene-1-(2Ј,4Ј,6Ј-trimethylphenyl)butane-1,3-dione
7) (5-H3 and 4-Me), 2.23 (6 H, s) and 2.27 (3 H, s) (3 × ArMe),
2.96 (1 H, d, J 6) and 3.05 (1 H, d, J 6) (1-H2), 3.02 (1 H, sept, J
7, 4-H) and 6.82 (2 H, s, ArH); δC(50 MHz) 17.4 (q), 18.3 (q),
19.2 (2q) and 21.0 (q) (C-5, 4-Me and 3 × ArMe), 37.5 (d, C-4),
51.7 (t, C-1), 63.4 (s, C-2), 128.3 (2d), 133.2 (s), 134.8 (2s) and
8d.† νmax/cmϪ1 1705 (C᎐O) and 1680 (C᎐O); δ (200 MHz)
᎐
᎐
H
2.17 (6 H, s), 2.25 (3 H, s) and 2.30 (3 H, s) (3 × ArMe and
4-H ), 5.90 (1 H, s) and 6.56 (1 H, s) (AB-pair, ᎐CH ) and 6.86
᎐
3
2
(2 H, s, ArH); δC(50 MHz) 19.2 (2q), 21.0 (q) and 29.9 (q)
(4 × Me), 128.5 (2d), 134.8 (2s), 136.0 (s), 139.1 (s) and 149.5 (s)
139.6 (s) (ArC), 203.1 (s) and 206.9 (s) (2 × C᎐O).
᎐
(ArC and C-2), 134.1 (t, ᎐CH ), 198.5 (s) and 199.8 (s)
1-(2Ј,4Ј,6Ј-Triisopropylphenyl)-2-methoxymethylbutane-1,3-
᎐
2
(2 × C᎐O).
dione 10a.‡ νmax/cmϪ1 1610 (C᎐O) and 1590 (C᎐C); δ (200 MHz)
᎐
᎐
᎐
H
2-Methylene-1-(2Ј,4Ј,6Ј-trimethylphenyl)pentane-1,3-dione
1.18 (12 H, d, J 7) and 1.26 (6 H, d, J 7) (3 × CHMe2), 2.32
(3 H, s, 4-H3), 2.89 (3 H, sept, J 7, 3 × CHMe2), 3.11 (3 H, s,
OMe), 3.77 (2 H, s, CH2OMe), 7.03 (2 H, s, ArH) and 16.61
(1 H, s, enolic OH); δC(50 MHz) 23.1 (2q), 23.8 (2q) and 25.1
(2q) (3 × CHMe2), 24.5 (q, C-4), 30.7 (2d) and 34.2 (d)
(3 × CHMe2), 57.6 (q, OMe), 68.9 (t, CH2OMe), 110.8 (s, C-2),
120.5 (2d), 130.2 (s), 145.0 (2s) and 149.7 (s) (ArC), 186.8 (s, C-
1) and 199.2 (s, C-3).
8e.† νmax/cmϪ1 1710 (C᎐O) and 1680 (C᎐O); δ (200 MHz) 1.16
᎐
᎐
H
(3 H, t, J 7, 5-H3), 2.17 (6 H, s) and 2.29 (3 H, s) (3 × ArMe),
2.87 (2 H, q, J 7, 4-H2), 5.88 (1 H, s) and 6.49 (1 H, s) (AB-pair,
᎐CH ) and 6.85 (2 H, s, ArH); δ (50 MHz) 7.6 (q, C-5), 19.1
᎐
2
C
(2q) and 20.9 (q) (3 × ArMe), 35.5 (t, C-4), 128.4 (2d), 134.0
(2s ϩ t), 136.0 (s), 138.9 (s) and 149.7 (s) (ArC, C-2 and ᎐CH ),
᎐
2
199.8 (s) and 201.9 (s) (2 × C᎐O).
᎐
4-Methyl-2-methylene-1-(2Ј,4Ј,6Ј-trimethylphenyl)pentane-
2-Ethoxymethyl-1-(2Ј,4Ј,6Ј-triisopropylphenyl)butane-1,3-
1,3-dione 8f.† νmax/cmϪ1 1720 (C᎐O) and 1680 (C᎐O); δ (200
dione 11a.‡ νmax/cmϪ1 1610 (C᎐O) and 1590 (C᎐C); δ (400
᎐
᎐
᎐
᎐
H
H
MHz) 1.18 (6 H, d, J 7, 5-H3 and 4-Me), 2.18 (6 H, s) and 2.29
(3 H, s) (3 × ArMe), 3.26 (1 H, sept, J 7, 4-H), 5.89 (1 H, s) and
MHz) 1.09 (3 H, t, J 7, OCH2Me), 1.17 (6 H, d, J 7), 1.18 (6 H,
d, J 7) and 1.26 (6 H, d, J 7) (3 × CHMe2), 2.36 (3 H, s, 4-H3),
2.90 (3 H, sept, J 7, 3 × CHMe2), 3.27 (2 H, q, J 7, OCH2Me),
3.82 (2 H, s, CH2OEt), 7.01 (2 H, s, ArH) and 16.75 (1 H, s,
enolic OH); δC(100 MHz) 14.9 (q), 23.3 (2q), 23.9 (2q), 24.9 (q)
and 25.2 (2q) (C-4, OCH2Me and 3 × CHMe2), 30.8 (2d) and
34.3 (d) (3 × CHMe2), 65.6 (t) and 67.1 (t) (CH2OCH2Me),
111.0 (s, C-2), 120.7 (2d), 130.3 (s), 145.2 (2s) and 149.8 (s)
(ArC), 186.3 (s, C-1) and 199.9 (s, C-3).
6.36 (1 H, s) (AB-pair, ᎐CH ) and 6.86 (2 H, s, ArH); δ (50
᎐
2
C
MHz) 18.0 (2q), 19.2 (2q) and 21.0 (q) (C-5, 4-Me and
3 × ArMe), 39.5 (d, C-4), 128.4 (2d), 134.2 (2s), 135.8 (s), 139.0
(s) and 149.5 (s) (ArC and C-2), 133.5 (t, ᎐CH ), 199.8 (s) and
᎐
2
206.6 (s) (2 × C᎐O).
᎐
3,4-Epoxy-3-(2Ј,4Ј,6Ј-triisopropylbenzoyl)butan-2-one 9a. Mp
78–79 ЊC (from pentane) (Found: C, 75.8; H, 9.0. C20H28O3
requires C, 75.9; H, 8.9%); νmax/cmϪ1 1730 (C᎐O) and 1700
᎐
(C᎐O); δ (200 MHz) 1.20 (6 H, d, J 7), 1.24 (6 H, d, J 7) and
1.25 (6 H, d, J 7) (3 × CHMe2), 2.40 (3 H, s, 1-H3), 2.70 (2 H,
sept, J 7) and 2.88 (1 H, sept, J 7) (3 × CHMe2), 2.99 (1 H, d, J
᎐
H
‡ Compounds 10a–c,e and 11a were obtained as oils. These compounds
underwent quantitative elimination of methanol (for 10) or ethanol (for
11) on distillation to give 8.
286
J. Chem. Soc., Perkin Trans. 1, 1998

View Article Online
1-(2Ј,4Ј,6Ј-Triisopropylphenyl)-2-methoxymethylpentane-1,3-
dione 10b.‡ νmax/cmϪ1 1610 (C᎐O) and 1590 (C᎐C); δ (400
(4 × CHMe2), 1.78 (3 H, s, 2-Me), 1.98 (1 H, sept, J 7), 2.65
(1 H, sept, J 7), 2.87 (1 H, sept, J 7) and 3.73 (1 H, d, J 7)
(3 × ArCHMe2 and 4-H), 4.52 (1 H, s, OH), 6.94 (1 H, s) and
7.01 (1 H, s) (ArH); δC(50 MHz) 19.5 (q), 21.1 (q), 23.0 (q), 23.5
(q), 23.9 (2q), 24.9 (q), 25.1 (q) and 25.3 (q) (4 × CHMe2 and
2-Me), 31.7 (d), 32.2 (d), 34.2 (d) and 34.5 (d) (4 × CHMe2),
88.8 (s, C-2), 120.7 (d), 121.1 (d), 135.0 (s), 143.6 (s), 145.0 (s)
᎐
᎐
H
MHz) 1.67 (6 H, d, J 7), 1.18 (6 H, d, J 7) and 1.26 (6 H, d, J 7)
(3 × CHMe2), 1.20 (3 H, t, J 7, 5-H3), 2.72 (2 H, q, J 7, 4-H2),
2.85–2.95 (3 H, m, 3 × CHMe2), 3.13 (3 H, s, OMe), 3.78 (2 H,
s, CH2OMe), 7.01 (2 H, s, ArH) and 16.68 (1 H, s, enolic OH);
δC(50 MHz) 8.4 (q, C-5), 23.2 (2q), 23.9 (2q) and 25.2 (2q)
(3 × CHMe2), 30.3 (t, C-4), 30.8 (2d) and 34.3 (d) (3 × CHMe2),
57.7 (q, OMe), 68.7 (t, CH2OMe), 110.4 (s, C-2), 120.7 (2d),
130.1 (s), 145.3 (2s) and 149.8 (s) (ArC), 184.8 (s, C-1) and 203.5
(s, C-3).
and 149.6 (s) (ArC), 212.5 (s) and 212.9 (s) (2 × C᎐O).
᎐
2-Hydroxy-2-methyl-1-(2Ј,4Ј,6Ј-trimethylphenyl)butane-1,3-
dione 12d.† νmax/cmϪ1 3450br (OH), 1720 (C᎐O) and 1700
᎐
(C᎐O); δ (200 MHz) 1.75 (3 H, s, 2-Me), 2.07 (6 H, br s),
᎐
H
1-(2Ј,4Ј,6Ј-Triisopropylphenyl)-2-methoxymethyl-4-methyl-
2.26 (3 H, s) and 2.47 (3 H, s) (3 × ArMe and 4-H3), 4.48 (1 H, s,
OH) and 6.80 (2 H, s, ArH); δC(50 MHz) 19.5 (q), 20.9 (q), 23.6
(q) and 24.7 (2q) (5 × Me), 89.1 (s, C-2), 128.1 (2d), 133.0 (2s),
pentane-1,3-dione 10c.‡ νmax/cmϪ1 1620 (C᎐O) and 1580 (C᎐C);
᎐
᎐
δH(400 MHz) 1.17 (6 H, d, J 7), 1.18 (6 H, d, J 7), 1.21 (6 H,
d, J 7) and 1.26 (6 H, d, J 7) (4 × CHMe2), 2.88 (2 H, sept, J 7)
and 3.05 (2 H, sept, J 7) (4 × CHMe2), 3.08 (3 H, s, OMe), 3.78
(2 H, s, CH2OMe), 7.01 (2 H, s, ArH) and 16.87 (1 H, s, enolic
OH); δC(50 MHz) 19.5 (2q), 23.2 (2q), 23.9 (2q) and 25.3 (2q)
(4 × CHMe2), 30.9 (2d), 33.8 (d) and 34.3 (d) (3 × CHMe2 and
C-4), 57.7 (q, OMe), 68.6 (t, CH2OMe), 109.6 (s, C-2), 120.7
(2d), 130.7 (s), 145.1 (2s) and 149.8 (s) (ArC), 188.1 (s, C-1) and
205.8 (s, C-3).
136.9 (s) and 138.4 (s) (ArC), 205.7 (s) and 211.6 (s) (2 × C᎐O).
᎐
2-Hydroxy-2-methyl-1-(2Ј,4Ј,6Ј-trimethylphenyl)pentane-1,3-
dione 12e. Mp 45–46 ЊC (from pentane) (Found: C, 72.7; H, 8.2.
C15H20O3 requires C, 72.6; H, 8.1%); νmax/cmϪ1 3470br (OH),
1720 (C᎐O) and 1700 (C᎐O); δ (200 MHz) 1.12 (3 H, t, J 7,
᎐
᎐
H
5-H3), 1.73 (3 H, s, 2-Me), 2.04 (6 H, br s) and 2.25 (3 H, s)
(3 × ArMe), 2.73 (1 H, dq, J 18 and 7) and 3.03 (1 H, dq, J 18
and 7) (4-H2), 4.55 (1 H, s, OH) and 6.79 (2 H, s, ArH); δC(50
MHz) 7.5 (q, C-5), 19.5 (q), 20.9 (q) and 24.7 (2q) (2-Me and
3 × ArMe), 29.1 (t, C-4), 88.9 (s, C-2), 128.1 (2d), 133.2 (2s),
2-Methoxymethyl-1-(2Ј,4Ј,6Ј-trimethylphenyl)pentane-1,3-
dione 10e.‡ νmax/cmϪ1 1610 (C᎐O) and 1590 (C᎐C); δ (200
᎐
᎐
H
MHz) 1.19 (3 H, t, J 7, 5-H3), 2.19 (6 H, s) and 2.28 (3 H, s)
(3 × ArMe), 2.71 (2 H, q, J 7, 4-H2), 3.10 (3 H, s, OMe), 3.79 (2
H, s, CH2OMe), 6.85 (2 H, s, ArH) and 16.57 (1 H, s, enolic
OH); δC(50 MHz) 8.3 (q, C-5), 19.0 (2q) and 21.0 (q)
(3 × ArMe), 30.4 (t, C-4), 57.6 (q, OMe), 68.5 (t, CH2OMe),
109.4 (s, C-2), 127.9 (2d), 131.9 (s), 134.5 (2s) and 138.4 (s)
(ArC), 183.9 (s, C-1) and 204.2 (s, C-3).
2-Methoxymethyl-4-methyl-1-(2Ј,4Ј,6Ј-trimethylphenyl)-
pentane-1,3-dione 10f. Mp 58–59 ЊC (from pentane) (Found: C,
74.1; H, 8.8. C17H24O3 requires C, 73.9; H, 8.8%); νmax/cmϪ1
136.9 (s) and 138.4 (s) (ArC), 208.6 (s) and 211.9 (s) (2 × C᎐O).
᎐
Reaction of compound 8c with methanol
Compound 8c (4 mg) dissolved in methanol (3 cm3) was
allowed to stand at room temperature for 1 h after which the
solvent was removed under reduced pressure. 1H NMR analysis
of the residue showed the quantitative formation of the adduct
10c.
References
1620 (C᎐O) and 1580 (C᎐C); δ (200 MHz) 1.20 (6 H, d, J 7,
᎐
᎐
H
1 For general reviews of the reaction of singlet oxygen, see: (a)
A. A. Frimer, Chem. Rev., 1979, 79, 359; (b) H. H. Wasserman and
R. W. Murray, Singlet Oxygen, Academic Press, New York, 1979; (c)
L. M. Stephenson, M. Jo Grdina and M. Orfanopoulos, Acc. Chem.
Res., 1980, 13, 419; (d) A. A. Frimer, Singlet Oxygen, CRC press,
Florida, 1985; (e) A. A. Gorman, The Bimolecular Reactivity of
Singlet Molecular Oxygen, in Advances in Photochemistry, vol. 17,
eds. D. H. Volman, G. S. Hammond and D. C. Neckers, Wiley, 1992,
pp. 217–274.
5-H3 and 4-Me), 2.19 (6 H, s) and 2.26 (3 H, s) (3 × ArMe), 3.06
(3 H, s, OMe), 3.07 (1 H, sept, J 7, 4-H), 3.80 (2 H, s, CH2OMe),
6.84 (2 H, s, ArH) and 17.04 (1 H, s, enolic OH); δC(50 MHz)
18.9 (2q), 19.3 (2q) and 20.9 (q) (C-5, 4-Me and 3 × ArMe),
33.7 (d, C-4), 57.4 (q, OMe), 68.2 (t, CH2OMe), 108.6 (s, C-2),
127.8 (2d), 132.5 (s), 134.2 (2s) and 138.2 (s) (ArC), 187.4 (s,
C-1) and 206.3 (s, C-3).
2 (a) H. E. Ensley, R. V. Carr, R. S. Martin and T. E. Pierce, J. Am.
Chem. Soc., 1980, 102, 2836; (b) B.-M. Kwon, R. C. Kanner and
C. S. Foote, Tetrahedron Lett., 1989, 30, 903.
3 (a) W. Adam, L. H. Catalani and A. Griesbeck, J. Org. Chem., 1986,
51, 5496; (b) W. Adam and M. J. Richter, Tetrahedron Lett., 1993,
34, 8423.
4 (a) W. Adam and A. Griesbeck, Angew. Chem., Int. Ed. Engl., 1985,
24, 1070; (b) W. Adam and A. Griesbeck, Synthesis, 1986, 1050.
5 M. Orfanopoulos and C. S. Foote, Tetrahedron Lett., 1985, 26, 5991.
6 H. H. Wasserman and J. E. Pickett, J. Am. Chem. Soc., 1982, 104,
4695.
7 J. H. Clark, Chem. Rev., 1980, 80, 429.
8 H. E. Ensley, P. Balakrishnan and B. Ugarkar, Tetrahedron Lett.,
1983, 24, 5189.
9 M. Yoshioka, T. Nishioka and T. Hasegawa, J. Org. Chem., 1993, 58,
278.
10 M. Yoshioka, K. Funayama and T. Hasegawa, J. Chem. Soc., Perkin
Trans. 1, 1989, 1411.
General procedure for the deoxygenation of the hydroperoxides
7a,c–e
A mixture of the hydroperoxy compound 7a,c–e (100–200 mg)
and triphenylphosphine (1.1 equiv.) in benzene (15–30 cm3) was
stirred overnight at room temperature. Concentration under
reduced pressure and subsequent chromatography on silica gel
[hexane–ethyl acetate (15:1)] gave the hydroxy compounds
12a,c–e.
2-Hydroxy-1-(2Ј,4Ј,6Ј-triisopropylphenyl)-2-methylbutane-
1,3-dione 12a. Mp 72–73 ЊC (from pentane) (Found: C, 75.5; H,
9.5. C20H30O3 requires C, 75.4; H, 9.5%); νmax/cmϪ1 3460br
(OH), 1720 (C᎐O) and 1700 (C᎐O); δ (200 MHz) 1.09 (3 H, d, J
᎐
᎐
H
7), 1.12 (3 H, d, J 7), 1.16 (3 H, d, J 7) and 1.33 (3 H, d, J 7) (2Ј-
CHMe2 and 6Ј-CHMe2), 1.24 (6 H, d, J 7, 4Ј-CHMe2), 1.74 (3
H, s, 2-Me), 1.95 (1 H, sept, J 7), 2.61 (1 H, sept, J 7) and 2.87 (1
H, sept, J 7) (3 × CHMe2), 2.47 (3 H, s, 4-H3), 4.43 (1 H, s, OH),
6.94 (1 H, s) and 7.00 (1 H, s) (ArH); δC(50 MHz) 23.2 (2q), 23.6
(q), 23.8 (2q), 25.0 (q) and 25.1 (2q) (C-4, 2-Me and
3 × CHMe2), 31.7 (d), 32.5 (d) and 34.2 (d) (3 × CHMe2), 89.3
(s, C-2), 120.7 (d), 120.9 (d), 134.4 (s), 143.6 (s), 145.4 (s) and
11 M. Yoshioka, H. Sawada, M. Saitoh and T. Hasegawa, J. Chem.
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12 (a) L. M. Stephenson, D. E. McClure and D. K. Sysak, J. Am.
Chem. Soc., 1973, 95, 7888; (b) M. B. Grdina, M. Orfanopoulos
and L. M. Stephenson, J. Am. Chem. Soc., 1979, 101, 3111; (c)
B.-M. Kwon and C. S. Foote, J. Org. Chem., 1989, 54, 3878; (d)
M. Orfanopoulos, I. Smonou and C. S. Foote, J. Am. Chem. Soc.,
1990, 112, 3607; (e) M. Orfanopoulos, M. Stratakis and Y. Elemes,
J. Am. Chem. Soc., 1990, 112, 6417; (f ) H.-S. Dang and A. G.
Davies, Tetrahedron Lett., 1991, 32, 1745; (g) M. Orfanopoulos and
M. Stratakis, Tetrahedron Lett., 1991, 32, 7321; (h) M. Stratakis
and M. Orfanopoulos, Tetrahedron Lett., 1995, 36, 4291; (i)
M. Stratakis, M. Orfanopoulos and C. S. Foote, Tetrahedron Lett.,
1996, 37, 7159.
149.7 (s) (ArC), 205.5 (s) and 212.3 (s) (2 × C᎐O).
᎐
2-Hydroxy-1-(2Ј,4Ј,6Ј-triisopropylphenyl)-2,4-dimethyl-
pentane-1,3-dione 12c. Mp 73–74 ЊC (from hexane) (Found: C,
76.3; H, 10.0. C24H34O3 requires C, 76.3; H, 9.9%); νmax/cmϪ1
3460br (OH), 1710 (C᎐O) and 1695 (C᎐O); δ (200 MHz) 1.05
᎐
᎐
H
(3 H, d, J 7), 1.12 (3 H, d, J 7), 1.15 (3 H, d, J 7), 1.19 (3 H, d,
J 7), 1.12 (3 H, d, J 7), 1.24 (6 H, d, J 7) and 1.32 (3 H, d, J 7)
J. Chem. Soc., Perkin Trans. 1, 1998
287

View Article Online
13 S. Inagaki, H. Fujimoto and K. Fukui, Chem. Lett., 1976, 749.
14 M. Orfanopoulos, M. B. Grdina and L. M. Stephenson, J. Am.
Chem. Soc., 1979, 101, 275.
15 (a) W. Adam and B. Nestler, J. Am. Chem. Soc., 1992, 114, 6549;
(b) W. Adam and B. Nestler, J. Am. Chem. Soc., 1993, 115, 5041;
(c) W. Adam, H.-G. Brünker, A. S. Kumar, E.-M. Peters, K. Peters,
U. Schneider and H. G. von Schnering, J. Am. Chem. Soc., 1996,
118, 1899.
Paper 7/05448C
Received 28th July 1997
Accepted 21st October 1997
288
J. Chem. Soc., Perkin Trans. 1, 1998