Iron(III) tosylate in the preparation of dimethyl and diethyl acetals from ketones and β-keto enol ethers from cyclic β-diketones

Article abstract of DOI:10.1080/00397910802219361

An efficient method for conversion of ketones to their corresponding dimethyl and diethyl acetals and of cyclic β-diketones into β-keto enol ethers using Fe(OTs)3 as a catalyst is described. Copyright Taylor & Francis Group, LLC.

Full text of DOI:10.1080/00397910802219361

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Iron(III) Tosylate in the
Preparation of Dimethyl and
Diethyl Acetals from Ketones
and β -Keto Enol Ethers from
Cyclic β -Diketones
Horacio Mansilla a & María M. Afonso b
a Instituto de Productos Naturales y Agrobiología del
C.S.I.C., La Laguna, Tenerife, Spain
b Instituto Universitario de Bioorgánica “Antonio
González,” Departamento de Química Orgánica,
Universidad de la Laguna, La Laguna, Tenerife, Spain
Version of record first published: 09 Sep 2008
To cite this article: Horacio Mansilla & María M. Afonso (2008): Iron(III) Tosylate in
the Preparation of Dimethyl and Diethyl Acetals from Ketones and β -Keto Enol Ethers
from Cyclic β -Diketones, Synthetic Communications: An International Journal for
Rapid Communication of Synthetic Organic Chemistry, 38:15, 2607-2618
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Synthetic Communications1, 38: 2607–2618, 2008
Copyright # Taylor & Francis Group, LLC
ISSN: 0039-7911 print/1532-2432 online
DOI: 10.1080/00397910802219361
Iron(III) Tosylate in the Preparation of Dimethyl
and Diethyl Acetals from Ketones and b-Keto
Enol Ethers from Cyclic b-Diketones
1
Horacio Mansilla and Marıa M. Afonso
2
´
1
´
Instituto de Productos Naturales y Agrobiologıa del C.S.I.C.,
La Laguna, Tenerife, Spain
2
ꢀ
Instituto Universitario de Bioorganica ‘‘Antonio Gonzalez,’’ Departamento de
Quımica Organica, Universidad de la Laguna, La Laguna, Tenerife, Spain
ꢀ
´
ꢀ
Abstract: An efficient method for conversion of ketones to their corresponding
dimethyl and diethyl acetals and of cyclic b-diketones into b-keto enol ethers
using Fe(OTs)3 as a catalyst is described.
Keywords: Diethyl acetals, dimethyl acetals, iron(III) tosylate, b-keto enol ethers,
ketones
INTRODUCTION
Dialkyl acetals are one of the most frequently used protective groups for
aldehydes and ketones.[1] The acetalization reaction is widely used in
organic synthesis and is typically achieved by treatment of the carbonyl
compound with the alcohol and=or the corresponding orthoformate
in the presence of protic acids, Lewis acids, or acidic catalysts. Some
methods for the preparation of dimethyl and diethyl acetals include
homogeneous catalysts such as PTSA,[2] PhSO2NHOH,[3] triflic acid,[4]
HCl,[5] DCC-SnCl4,[6] TMSOTf,[7] LaCl3,[8] Sc(OTf)3,[9] Bi(OTf)3,[10]
Bi(NO3)3,[11] RuCl3,[12] TiCl4,[13] In(OTf)3,[14] B10H14,[15] [Hmin]BF4,[16]
LiBF4,[17] Cu(BF4)2,[18] iodine,[19] FeCl3,[20] DDQ,[21] ZrCl4,[22] NBS,[23] and
tetrabutylammonium tribromide (TBATB).[24] On the other hand, some solid
Received in the U.K. October 24, 2007
Address correspondence to Horacio Mansilla, Instituto de Productos Naturales
ꢀ
´
y Agrobiologıa del C.S.I.C., Avda. Fco. Sanchez 3, 38206 La Laguna, Tenerife,
Spain. E-mail: hmansill@ull.es
2607

2608
H. Mansilla and M. M. Afonso
Scheme 1.
catalysts[25] such as sulphonic resins,[26] acidic montmorillonite clay,[27] mont-
morillonite clay K 10–PTSA,[28] and zeolites,[29] in the presence of trimethyl
orthoformate and montmorillonite clay K 10,[30] Ce-exchanged clay,[31]
siliceous mesoporous silica,[32] and amorphous SO3H-SiO2 with methanol
[33]
have also been employed for the preparation of dimethyl acetals. Acetalization
is more easily achieved from aldehydes than from ketones, and a literature
survey shows that a few methods are available for the preparation of diethyl
acetals in comparison with those employed to obtain dimethyl acetals.
Ketone reactivity generally follows the order acyclic ꢀ cyclohexanones >
Scheme 2.

Iron(III) Tosylate
2609
cyclopentanones > a,b-unsaturated ketones ꢀ a,a-disubstituted ketones
>> aromatic ketones. The preparation of dialkyl acetals from diaryl ketones
is more difficult, and standard methods for acetalization generally fail.
Acetalization rate in diaryl ketones is strongly influenced by both the presence
of two favorable aryl groups by way of the stabilization of the intermediate
cation and by the unfavourable steric crowding during the initial formation
of a hemiacetal.
Here we report on an alternative and efficient method for the
preparation of dimethyl and diethyl acetals from aldehydes and
especially from ketones, including diaryl ketones, with the use of
[34]
Fe(OTs)3
as a catalyst (Scheme 1). Likewise, iron(III) tosylate acts
as a good catalyst in the formation of b-keto enol ethers from cyclic
b-diketones (Scheme 2).
RESULTS AND DISCUSSION
Initially we explored the preparation of dimethyl and diethyl acetals
from aldehydes by treatment with the alcohol and the corresponding
orthoformate in the presence of variable amounts of iron(III) tosylate.
This reagent is relatively inexpensive to prepare in high yield, easy to han-
dle in relation with other iron(III) salts, and can be stored indefinitely at
room temperature under an inert atmosphere.
After several assays, we found that aldehydes could be readily con-
verted to their corresponding dialkyl acetals in excellent yields by using
3 mol% Fe(OTs)3 as a catalyst at room temperature (Table 1).
Table 1. Protection of aldehydes as dimethyl and diethyl acetals with ROH=
a
HC(OR)3 catalyzed by Fe(OTs)3
Entry
Substrate
ROH
Temp
Time
Yield (%)
1
2
3
4
5
6
7
8
9
10
4-Bromobutanal
Heptaldehyde
Benzaldehyde
Benzaldehyde
Anisaldehyde
Anisaldehyde
3-Bromobenzaldehyde
4-Chlorobenzaldehyde
trans-Cinnamaldehyde
Furfural
MeOH
MeOH
MeOH
EtOH
MeOH
EtOH
EtOH
EtOH
EtOH
EtOH
rt
rt
rt
rt
rt
rt
rt
rt
rt
rt
30 min
30 min
30 min
30 min
60 min
90 min
30 min
60 min
120 min
30 min
>99
97
>99
>99
96
98
>99
95
86
92
aThe structures of the products were established from their spectral (1H NMR,
13C NMR, and MS) data.

2610
H. Mansilla and M. M. Afonso
Likewise, we examined the possibility of extending this method-
ology to the preparation of the corresponding acetals from ketones
under identical conditions. Most of the ketones tested were efficiently
converted into their dimethyl and diethyl acetals at room temperature
or under reflux conditions with the alcohol as solvent (Table 2). Only
in the case of dicyclohexyl ketone (entries 25 and 26) was the forma-
tion of the acetal not observed, and only minimal amounts of the cor-
responding vinyl ethers were detected, probably due to the large steric
impediment induced by the two cyclohexyl groups contiguous to the
carbonyl group. A b-keto ester such as ethyl acetoacetate under these
conditions afforded mixtures 3 : 1 (acetal–enol ether) with high overall
yield. With diaryl ketones, the best results were obtained with the use
of 5 mol% Fe(OTs)3 at reflux. Dimethyl acetals were formed in excel-
lent yields including 9-fluorenone dimethyl acetal (entry 35), which is
difficult to prepare using other known acetalization methods.[4,10]
The yields of diethyl acetals from diaryl ketones decrease in relation
to those of the corresponding dimethyl acetals and in the case of
4,40-dichlorobenzophenone (entry 32) and 4-nitrobenzophenone (entry
34) the conversions are significantly low, even after long reaction
times, with the greater part of the starting ketones being recovered
unreacted.
Finally, we explored the use of Fe(OTs)3 in the preparation of b-keto
enol ethers from cyclic b-diketones (Scheme 2). b-Keto enol ethers are
very valuable synthetic intermediates,[35] and they have been widely used
in the construction of various biologically active compounds.[36] Several
methods have been reported to prepare b-keto enol ethers from cyclic
b-diketones such as methylation with diazomethane,[35a] reaction with
alcohols and PTSA,[37] and reaction with alcohols catalyzed by TiCl4,[13]
iodine,[38] B(C6F5)3,[39] Yb(OTf)3,[40] CAN,[41] or HClO4–SiO2.[42] b-Keto
enol ethers also have been prepared from 3-chloro-cycloalk-2-enones by
treatment with methoxide.[43]
Reaction of cyclic b-diketones with various alcohols in the pres-
ence of Fe(OTs)3(5 mol%) as a catalyst afforded the corresponding
b-keto enol ethers in good to high yields (Table 3). Generally reac-
tions were carried out at reflux with the alcohols acting as solvents
or with the use of toluene or 1,2-dichloroethane. In the reactions with
methanol (entries 1, 11, and 14), b-keto enol ethers were cleanly
obtained in high yields at room temperature. When a b-diketone such
as dimedone (3c) reacts with primary diols(entries 23–26), under the
described conditions, the distribution of the obtained compounds
clearly depends on their chain length. Thus, in the reaction with
1,2-ethanediol (entry 23), together with the corresponding b-keto enol
ether 6, significant amounts (25% overall yield) were isolated of the

Iron(III) Tosylate
2611
Table 2. Protection of ketones as dimethyl and diethyl acetals with ROH=
a
HC(OR)3 catalyzed by Fe(OTs)3
Entry
Substrate
Acetophenone
Acetophenone
ROH
Temp
Time
Yield (%)
1
2
MeOH
EtOH
MeOH
EtOH
MeOH
EtOH
MeOH
EtOH
MeOH
EtOH
MeOH
EtOH
MeOH
EtOH
MeOH
EtOH
MeOH
EtOH
MeOH
EtOH
EtOH
MeOH
MeOH
EtOH
MeOH
EtOH
MeOH
EtOH
MeOH
EtOH
MeOH
EtOH
MeOH
EtOH
MeOH
EtOH
MeOH
EtOH
rt
4 h
4 h
99
98
rt
3
Benzylideneacetophenone
Benzylideneacetophenone
1,5-Diphenylpentan-3-one
1,5-Diphenylpentan-3-one
1,3-Diphenylacetone
1,3-Diphenylacetone
Cyclohexanone
reflux
reflux
rt
2 h
2 h
95
84
4
5
4 h
5 h
99
94
6
rt
7
rt
2 h
4 h
97
95
8
rt
9
rt
30 min
1 h
2 h
98
96
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
Cyclohexanone
rt
2-Methylcycloxanone
2-Methylcyclohexanone
1,4-Cyclohexanedione
1,4-Cyclohexanedione
Cycloheptanone
rt
96
rt
3 h
94
rt
30 min
30 min
1 h
98b
96b
92
rt
rt
Cycloheptanone
Cyclooctanone
rt
5 h
4 h
69
92
rt
Cyclooctanone
Cyclododecanone
rt
4 h
1 h
87
99
rt
Cyclododecanone
Chloroacetone
rt
3 h
2 h
98
91
rt
3-Octanone
d,l-Camphor
d,l-Camphor
rt
2 h
84
77
rt
24 h
24 h
—
rt
51
Dicyclohexyl ketone
Dicyclohexyl ketone
Benzophenoned
Benzophenoned
NRc
NRc
reflux
reflux
reflux
reflux
reflux
reflux
reflux
reflux
reflux
reflux
rt
—
—
—
6 h
99
96
10 h
8 h
4,40-Dimethoxybenzophenoned
4,40-Dimethoxybenzophenoned
4,40-Dichlorobenzophenoned
4,40-Dichlorobenzophenoned
4-Nitrobenzophenoned
4-Nitrobenzophenoned
9-Fluorenoned
98
78
48 h
24 h
24 h
36 h
48 h
24 h
24 h
3 h
97
60 (98)e
96
28 (99)e
99
80
9-Fluorenoned
Ethyl acetoacetate
Ethyl acetoacetate
70=28f
67=27f
rt
3 h
aThe structures of the products were established from their spectral (1H NMR,
13C NMR, and MS) data.
bYield of bis-acetal at C1 and C4.
cOnly miniscule amounts of the corresponding enol ether were detected.
d5 mol% of Fe(OTs)3 was used.
eYield based on conversion in parentheses.
fAcetal=Ethyl(2E)-3-ethoxy-2-butenoate.

2612
H. Mansilla and M. M. Afonso
Table 3. Fe(OTs)3-catalyzed etherification of cyclic b-diketonesa
Entry
Substrate
R00OHb
Temp
Time
Yield (%)
1
2
3a
3a
3a
3a
3a
3a
3a
3a
3a
3a
3b
3b
3b
3c
3c
3c
3c
3c
3c
3c
3c
3c
3c
3c
3c
3c
3c
Methanol
Ethanol
Propanol
rt
4 h
3 h
4 h
6 h
4 h
6 h
6 h
6 h
6 h
6 h
2 h
3 h
6 h
2 h
3 h
4 h
6 h
4 h
6 h
6 h
6 h
6 h
4 h
6 h
12 h
12 h
12 h
99
95
reflux
reflux
reflux
reflux
reflux
reflux
reflux
reflux
reflux
rt
3
94
81
4
Isopropanol
Butanol
Isobutanol
5
92
82
6
7
Propargyl alcohol
Allyl alcohol
Benzyl alcoholc
Cyclohexanolc
Methanol
87
77
8
9
83
69
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
98
87
Ethanol
reflux
reflux
rt
Isopropanol
Methanol
Ethanol
85
98
reflux
reflux
reflux
reflux
reflux
reflux
reflux
reflux
reflux
reflux
reflux
reflux
reflux
96
93
Propanol
Isopropanol
Butanol
81
91
Isobutanol
85
82
Cyclohexanolc
Propargyl alcohol
Benzyl alcoholc
1,2-Ethanediold
1,3-Propanediold
1,4-Butanediold
1,6-Hexanediold
4-Hydroxybutyl acetated
82
79
25=66e
87f
37=35g
70h
64
aThe structures of the products were established from their spectral (1H NMR,
13C NMR, and MS) data.
bUnless otherwise stated, alcohol acts as solvent.
cIn toluene.
dIn 1,2-dichloroethane.
eb-Ketodioxolane 5=b-keto enol ether 6.
fb-Keto enol ether 7.
gb-Keto enol ether 8=bis-b-keto enol ether 9.
hBis-b-keto enol ether 10. Only minimal amounts of the corresponding b-keto
enol ether was isolated (0.9%).
b-keto acetal 5, whereas the use of 1,3-propanediol (entry 24) gave
exclusively the formation of the b-keto enol ether 7. The reaction
with 1,4-butanediol (entry 25) led to a mixture of the b-keto enol
ether 8 and the corresponding bis-b-enol ether 9, the latter resulting
from the reaction of both hydroxyl groups of the diol with the

Iron(III) Tosylate
2613
b-diketone. Acetylation of 6 led to a compound identical with that
obtained by reaction of dimedone with 4-hydroxybutyl acetate (entry
27). Lastly, the reaction of dimedone with 1,6-hexanediol (entry 26)
under the described conditions led exclusively to the formation of
bis-b-enol ether 10.
In conclusion, a simple and efficient method has been developed
for the protection of carbonyl groups that is especially applicable to
protect a wide variety of ketones, as dimethyl and diethyl acetals,
in high yields, using easy-to-handle Fe(OTs)3 as a Lewis acid catalyst
in the presence of the corresponding alkyl orthoformate as water
scavenger. In the same way, Fe(OTs)3 also acts as a good catalyst
in the preparation of b-keto enol ethers from cyclic b-diketones and
alcohols.
EXPERIMENTAL
Iron(III) tosylate was prepared as described in Ref. 34. Methanol and
ethanol were dried by passage through Linde-type 4 A molecular sieves.
Other alcohols and solvents were dried by conventional methods, and
orthoesters were used as received. Cyclic b-diketones were recrystallized
1
prior to use. Melting points are uncorrected. H NMR and 13C NMR
spectra were recorded on a Bruker Avance 300 spectrometer at 300 and
75 MHz respectively in C6D6 as a solvent, and d values are expressed in
parts per million. The mass spectra were recorded on a VG Autoscope
(Fisons Instruments) spectrometer.
General Procedure for Preparation of Dialkyl Acetals
To a stirred solution of Fe(OTs)3 (17 mg, 0.03 mmol) and trialkyl ortho-
formate (0.32 ml, 3 mmol) in the corresponding dry alcohol (5 ml) the car-
bonyl compound (1 mmol) neat or dissolved in the minimal amount of
dry alcohol was added. The mixture was stirred at room temperature
or under reflux under an inert atmosphere for the specified time, and
the reaction was monitored by TLC or GC. The reaction was quenched
by addition of a saturated aqueous NaHCO3 (10 ml) solution and stirring
for 10 min at room temperature. The resulting mixture was extracted with
dichloromethane or ether, the organic phase was dried over anhydrous
MgSO4, and the solvent was removed under reduced pressure. The pure
acetals were obtained from the crude by crystallization or chromato-
graphy over silica gel or neutral alumina with mixtures of hexane–EtOAc
as eluents.

2614
H. Mansilla and M. M. Afonso
General Procedure for Preparation of Cyclic b-Keto Enol Ethers
Method A
To a stirred solution of the b-diketone (1 mmol) in the appropriate alco-
hol, which acts as solvent, 5 ml of Fe(OTs)3 (38 mg, 0.05 mmol) were
added. The resulting mixture was heated at reflux under an inert atmo-
sphere, and the reaction was monitored by TLC. The mixture was cooled
to room temperature, poured into a saturated aqueous NaHCO3 solution
(10 ml), and stirred at room temperature for 10 min. After extraction with
dichloromethane or ethyl acetate, the combined organic phases were
dried over anhydrous MgSO4 and concentrated at reduced pressure.
The b-keto enol ethers obtained were purified by chromatography on sil-
ica gel or neutral alumina with mixtures of hexane–EtOAc as eluents.
Method B
To a stirred solution of the b-diketone (1 mmol) in toluene or 1,2-dichloro-
ethane (10 ml), the alcohol (3 mmol) and Fe(OTs)3 (38 mg, 0.05 mmol)
were added, and the resulting mixture was heated at reflux under an inert
atmosphere. The reaction was monitored by TLC. Workup was done as
in method A.
1
All the products were characterized by H NMR, 13C NMR, and
mass spectral analysis.
Selected Spectral Data
1
Benzylideneacetophenone diethyl acetal: A colorless oil; H NMR d: 7.79
(d, J ¼ 7.9 Hz, 2 H), 7.28–6.96 (m, 9 H), 6.22 (d, J ¼ 16.0 Hz, 1 H), 3.58–
3.35 (m, 4 H), 1.16 (dd, J ¼ 6.9, 7.0 Hz, 6 H); 13C NMR d: 142.0, 136.5,
131.7, 130.4, 128.3, 127.8, 127.5, 127.4, 127.0, 126.6, 100.9, 56.9, 14.9;
MS m=z (%): 282 (Mþ, 29), 237 (Mþ -OEt, 55), 77 (100).
1
1,5-Diphenylpentan-3-one dimethyl acetal: A colorless oil; H NMR d:
7.28–7.16 (m, 10H), 3.14 (s, 6 H), 2.75–2. 70 (m, 4 H), 2.14–2.08 (m,
4 H); 13C NMRd: 141.9, 128.3, 128.2, 125.7, 102.4, 47.1, 34.2, 30.5; MS
m=z (%): 253 (Mþ -OMe, 9), 179 (100), 91 (96).
1
1,5-Diphenylpentan-3-one diethyl acetal: A light yellow oil; H NMR d:
7.29–7.15 (m, 10 H), 3.49 (ddd, J ¼ 7.0, 7.0, 7.0 Hz, 4 H), 2.79–2.73 (m,
4 H), 2.18–2.12 (m, 4 H), 1.22 (dd, J ¼ 7.0, 7.0 Hz, 6 H); 13C NMR, d:
142.1, 128.2, 128.1, 125.7, 102.2, 54.9, 35.4, 30.3, 15.2; MS m=z (%):
267 (Mþ - OEt, 8), 207 (85), 91 (100).

Iron(III) Tosylate
2615
1
1,3-Diphenylacetone diethyl acetal: A colorless oil; H NMR d: 7.37–7.16
(m, 10 H), 3.59–3.51 (m, 4 H), 3.02 (s, 4 H), 1.23 (dd, J ¼ 6.9, 7.0 Hz,
3 H), 1.22 (dd, J ¼ 7.0 Hz, 3 H); 13C NMR d: 137.2, 130.4, 127.7, 126.0,
103.0, 55.3, 40.1, 15.0; MS m=z (%): 239 (Mþ -OEt, 12), 193 (80), 91
(100).
1
2-Methylcyclohexanone diethyl acetal: A colorless oil; H NMR d: 3.45–
3.25 (m, 4 H), 2.17–2.03 (m, 1 H), 1.94–1.82 (m, 1 H), 1.77–1.68 (m,
1 H), 1.55–1.31 (m, 6 H), 1.11–1.03 (m, 6 H), 0.96 (d, J ¼ 7.2 Hz, 3 H);
13C NMR d: 101.5, 54.3, 53.8, 34.3, 29.2, 28.2, 22.8, 20.0, 15.2, 15.1,
13.9; MS m=z (%): 186 (Mþ, 39), 141 (Mþ -OEt, 80), 129 (100).
1
Cycloheptanone diethyl acetal: A colorless oil; H NMR d: 3.49 (ddd,
J ¼ 7.0, 7.0, 7.0 Hz, 4 H), 1.89–1.80 (m, 4 H), 1.59–1.43 (m, 8 H), 1.13
(dd, J ¼ 7.0, 7.0 Hz, 6 H); 13C NMR d: 103.8, 54.8, 37.0, 29.0, 21.8,
15.3; MS m=z (%): 186 (Mþ, 8), 141 (Mþ -OEt, 97), 129 (100).
Cyclooctanone diethyl acetal: A colorless oil; 1H NMR d: 3.39 (ddd,
J ¼ 7.0, 7.0, 7.0 Hz, 2 H), 3.38 (ddd, J ¼ 7.0, 7.0, 7.0 Hz, 2 H), 1.88–
1.80 (m, 4 H), 1.62–1.42 (m, 10 H), 1.13 (dd, J ¼ 7.0, 7.0 Hz, 3 H), 1.12
(dd, J ¼ 7.0, 7.0 Hz, 3 H); 13C NMR d: 103.3, 54.73, 31.3, 28.1, 24.4,
21.4, 15.3; MS m=z (%): 200 (Mþ , 20), 155 (Mþ -OEt, 83), 129 (100).
1
Cyclododecanone diethyl acetal: A colorless oil; H NMR d: 3.41 (ddd,
J ¼ 7.0, 7.0, 7.0 Hz, 4 H), 1.77–1.68 (m, 4 H), 1.40–1.30 (m, 18 H), 1.15
(dd, J ¼ 7.0, 7.0 Hz, 6 H); 13C NMR d: 103.4, 54.8, 30.3, 26.2, 26.0,
22.3, 21.9, 19.4, 15.2; MS m=z (%): 256 (Mþ , 7), 211, Mþ - OEt, 76),
129 (100).
1
Chloroacetone diethyl acetal: A colorless oil; H NMR d: 3.34 (s, 2H),
3.35–3.22 (m, 4 H), 1.33 (s, 3 H), 1.02 (dd, J ¼ 7.0, 7.0 Hz, 6 H); 13C
NMR d: 99.7, 55.8, 46.4, 20.7, 14.9; MS m=z (%): 316 (Mþ , 5), 271
(Mþ - OMe, 100).
1
d,l-Camphor diethyl acetal: A colorless oil; H NMR d: 3.63–3.50 (m,
1 H), 3.44–3.25 (m, 3 H), 2.23–2.11 (m, 1 H), 1.94–1.82 (m, 1 H), 1.82–
1.74 (m, 1 H), 1.59 (dd, J ¼ 4.7, 4.7 Hz, 1 H), 1.40–1.32 (m, 3 H), 1.08
(dd, J ¼ 7.0, 7.1 Hz, 3 H), 1,07 (dd, J ¼ 7.0, 7.0 Hz, 3 H), 1.07 (s, 3 H),
1.04 (s, 3 H), 0.82 (s, 3 H); 13C NMR d: 108.7, 57.4, 55.1, 53.3, 50.1,
44.8, 42.0, 29.7, 27.7, 21.1, 20.8, 15.7, 15.5, 12.6; MS m=z (%): 226
(Mþ, 22), 211 (8), 181(Mþ -OEt, 25), 95 (100).
1
Ethyl acetoacetate diethyl acetal: A colorless oil; H NMR d: 3.94 (ddd,
J ¼ 7.1, 7.1, 7.1 Hz, 2 H), 3.52–3.30 (m, 4 H), 2.70 (s, 2 H), 1.60 (s,
3 H), 1.08 (dd, J ¼ 7.0, 7.1 Hz, 6 H), 0.94 (dd, J ¼ 7.1, 7.1 Hz, 3 H); 13C
NMR dv: 169.2, 99.8, 60.0, 56.0, 43.4, 23.1, 15.4, 14.1; MS m=z (%):
159 (Mþ -OEt, 100).
Ethyl (2E)-3-ethoxy-2-butenoate:
A
light yellow oil; 1H NMRd:
5.05 (s,1 H), 4.13 (ddd, J ¼ 7.1, 7.1, 7.1 Hz, 2 H), 3.21 (ddd, J ¼ 7.0,
7.0, 7.0 Hz, 2 H), 2.43 (s, 3 H), 1.08 (dd, J ¼ 7.1, 7.1 Hz, 3 H),

2616
H. Mansilla and M. M. Afonso
0.86 (dd, J ¼ 7.0, 7.0 Hz, 3 H); 13C NMR d: 172.0, 167.6, 91.7, 63.4,
59.2, 19.1, 14.6, 14.0; MS m=z (%): 158 (Mþ, 18), 113 (Mþ -OEt, 84),
85 (100).
3-Cyclohexyloxy-5,5-dimethyl-2-cyclohexen-1-one (Table 3, entry 20): A
1
light yellow oil; H NMR d: 5.46 (s, 1 H), 3.83–3.78 (m, 1 H), 2.10 (s,
2 H), 1.94 (s, 2 H), 1.64–1.59 (m, 2 H), 1.47–1.41 (m, 2 H), 1.33–1.24
(m, 3 H), 1.07–0.93 (m, 3 H), 0.77 (s, 6 H); 13C NMR d: 196.6, 172.7,
102.0, 75.0, 50.5, 42.9, 31.6, 30.7, 27.6, 25.1, 23.1; MS m=z (%): 222
(Mþ , 11), 141 (100).
9,9-Dimethyl-1,4-dioxaspiro[4.5]decan-7-one (5): A colorless oil; 1H NMR
d: 3.36 (s, 4 H), 2.44 (s, 2 H), 1.91 (s, 2 H), 1.62 (s, 2 H), 0.87 (s, 6 H); 13C
NMR d: 204.9, 109.8, 63.8, 53.5, 50.3, 46.6, 31.9, 29.1; MS m=z (%): 184
(Mþ, 5), 127 (100).
3-(2-Hydroxyethoxy)-5,5-dimethyl-2-cyclohexen-1-one (6): A colorless
1
oil; H NMR d: 5.33 (s, 1 H), 3.37–3.34 (m, 2 H), 3.29–3.26 (m, 2 H),
2.05 (s, 2 H), 1.87 (s, 2 H), 0.73 (s, 6 H); 13C NMR d: 198.2, 175.4,
101.5, 69.7, 59.9, 50.3, 42.2, 31.6, 27.5; MS m=z (%): 184 (Mþ , 25),
1
169 (8), 141 (65), 85 (100). Acetate: H NMR d: 5.25 (s, 1 H), 3.92–3.85
(m, 2 H), 3.26–3.23 (m, 2 H), 2.01 (s, 2 H), 1.86 (s, 2 H), 1.60 (s, 3 H),
0.70 (s, 6 H).
3-(3-Hydroxypropoxy)-5,5-dimethyl-2-cyclohexen-1-one (7): A colorless
1
oil; H NMR d: 5.46 (s, 1H), 3.61–3.58 (m, 2 H), 3.51–3.46 (m, 2 H),
2.06 (s, 2 H), 1.87 (s, 2 H), 1.66–1.60 (m, 2 H), 0.73 (s, 6 H); 13C NMR
d: 198.3, 175.5, 101.5, 65.5, 58.3, 50.3, 42.3, 31.6, 31.5, 27.5; MS m=z
1
(%): 198 (Mþ, 9), 183 (11), 141 (95), 85 (100). Acetate: H NMR d:
5.33 (s, 1 H), 3.95–3.91 (m, 2 H), 3.27–3.23 (m, 2 H), 2.06 (s, 2 H), 1.84
(s, 2 H), 1.66 (s, 3 H), 1.62–1.53 (m, 2 H), 0.73 (s, 6 H).
3-(4-Hydroxybutoxy)-5,5-dimethyl-2-cyclohexen-1-one (8): White crystals
ꢁ
1
(CH2Cl2–hexane); mp 62–64 C; H NMR d: 5.43 (s, 1 H), 3.50–3.38
(m, 4 H), 2.08 (s, 2 H), 1.90 (s, 2 H), 1.62–1.53 (m, 2 H), 1.49–1.40 (m,
2 H), 0.75 (s, 6 H); 13C NMR d: 197.6, 174.8, 101.5, 67.9, 61.4, 50.4,
42.3, 31.6, 28.8, 27.6, 25.0; MS m=z (%): 212 (Mþ, 18), 141 (42), 85
1
(51), 84 (100). Acetate: H NMR d: 5.35 (s, 1 H), 3.88–3.84 (m, 2 H),
3.22–3.18 (m, 2 H), 2.08 (s, 2 H), 1.89 (s, 2 H), 1.67 (s, 3 H), 1.38–1.28
(m, 4 H), 0.76 (s, 6 H); 13C NMR d: 196.5, 173.8, 169.5, 101.5, 67.1,
63.2, 50.4, 42.2, 31.5, 27.5, 24.9, 24.7, 19.9; MS m=z (%): 254 (Mþ,
24), 239 (18), 179 (43), 55 (100). This compound is identical to the pro-
duct obtained in the reaction of dimedone with 4-hydroxybutyl acetate
(Table 3, entry 27).
Compound 9: White crystals (CH2Cl2–hexane); mp 140–142 ꢁC; 1H NMR
d: 5.37 (s, 2 H), 3.24–3.18 (m, 4 H), 2.10 (s, 4 H), 1.93 (s, 4 H), 1.34–1.28
(m, 4 H), 0.76 (s, 12 H); 13C NMR d: 196.6, 173.8, 101.8, 67.1, 50.5, 43.4,
31.6, 27.6, 24.8; MS m=z (%): 334 (Mþ , 15), 179 (100).

Iron(III) Tosylate
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2617
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