A convenient route to (E)-α,β-unsaturated methyl ketones

Article abstract of DOI:10.1080/10426500903348039

Aldehydes are converted into (E)-α,β-unsaturated methyl ketones in good yield and with a high E stereoselectivity using α,α- bis(trimethylsilyl) N-tert-butyl acetimine 3. The reaction was mediated by a catalytic amount of tetrabutylammonium fluoride (TBAF) under mild conditions. The disilylated reagent 3 is easily generated from N-tert-butylacetimine, lithium diisopropylamide (LDA), and chlorotrimethylsilane. The mechanism of the reaction is discussed. Copyright

Full text of DOI:10.1080/10426500903348039

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Phosphorus, Sulfur, and Silicon and the
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A Convenient Route to (E)-α,β-
Unsaturated Methyl Ketones
a
a
a
a
M. Bellassoued , J. Aatar , M. Bouzid & M. Damak
a
Laboratoire de Synthèse Organométallique , Université de Cergy-
Pontoise , Cergy-Pontoise Cedex, France
Published online: 25 Aug 2010.
To cite this article: M. Bellassoued , J. Aatar , M. Bouzid & M. Damak (2010) A Convenient Route to
(E)-α,β-Unsaturated Methyl Ketones, Phosphorus, Sulfur, and Silicon and the Related Elements, 185:9,
1886-1895, DOI: 10.1080/10426500903348039
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Phosphorus, Sulfur, and Silicon, 185:1886–1895, 2010
Copyright ꢀ
Taylor & Francis Group, LLC
C
ISSN: 1042-6507 print / 1563-5325 online
DOI: 10.1080/10426500903348039
A CONVENIENT ROUTE TO (E)-α,β-UNSATURATED
METHYL KETONES
M. Bellassoued, J. Aatar, M. Bouzid, and M. Damak
Laboratoire de Synth e` se Organom e´ tallique, Universit e´ de Cergy-Pontoise,
Cergy-Pontoise Cedex, France
Aldehydes are converted into (E)-α,β-unsaturated methyl ketones in good yield and with
a high E stereoselectivity using α,α-bis(trimethylsilyl) N-tert-butyl acetimine 3. The reac-
tion was mediated by a catalytic amount of tetrabutylammonium fluoride (TBAF) under
mild conditions. The disilylated reagent 3 is easily generated from N-tert-butylacetimine,
lithium diisopropylamide (LDA), and chlorotrimethylsilane. The mechanism of the reaction
is discussed.
Keywords LDA; α-silylated acetimines; TBAF; N-tert-butylacetimine; α,β-unsaturated
methyl ketones
INTRODUCTION
For many years, we have been interested in our laboratory in developing new ap-
proaches to retinoid synthesis using organosilicon reagents. For this purpose, we described
in a previous work a new route for the (E)-α,β-unsaturated aldehydes synthesis using
1
,2
α,α-bis(trimethylsilyl) N-tert-butylaldimines. We have just examined in the end of our
1
article the behavior of the α,α-bis(trimethylsilyl) N-tert-butylacetimine 3 with benzalde-
hyde leading to the benzylidene acetone 4a. In this article, we report an account of our
investigations concerning the extension of our methodology to various aldehydes and show
that synthon 3 is a versatile organosilicon reagent for the direct homologation of aldehydes
into (E)-α,β-unsaturated methyl ketones. This reagent 3 is now commercially available.
RESULTS AND DISCUSSION
Preparation of N-tert-Butylacetimine 1
Reagent 1 was prepared from acetone and N-tert-butylamine in the presence of 4Å
3
molecular sieves at room temperature (Scheme 1). Molecular sieves serve simultaneously
as a dehydrating agent and as a catalyst that can be removed at the end of the reaction by
Received 11 June 2009; accepted 18 September 2009.
Address correspondence to M. Bellassoued, Laboratoire de Synth e` se Organom e´ tallique, Universit e´
de Cergy-Pontoise, 5 Mail Gay Lussac, Neuville-sur-Oise, 95031 Cergy-Pontoise Cedex, France. E-mail:
moncef.bellassoued@chim.u-cergy.fr
1
886

(
E)-α,β-UNSATURATED METHYL KETONES
1887
simple filtration. Since the method is so mild and so simple, it may prove preferable to the
4
use of more vigorous catalysts such as titanium tetrachloride.
O
NtBu
N-tert-butylamine, pentane
4
Å molecular sieves, rt
yield = 50%
1
Scheme 1
Preparation of α-Trimethylsilyl N-tert-Butylacetimine 2
The monosilylated ketimine 2 was prepared from acetone N-tert-butylamine 1,
lithium diisopropylamide (LDA), and chlorotrimethylsilane (Scheme 2) according to a
5
modified procedure described by Croteau and Termini.
NtBu
NtBu
1°- LDA, -50°C, THF
SiMe3
2
°- Me SiCl, -50°C
20°C
3
1
2
yield = 80%
Scheme 2
Preparation of α,α-Bis(trimethylsilyl) N-tert-Butylacetimine 3
Deprotonation of α-trimethylsilyl N-tert-butyl ketimine 2 by one equivalent of LDA
◦
at −50 C followed by trimethylsilyl chloride trapping affords the disilylated ketimine 3
in 62% yield (procedure A), whereas a one-pot preparation of 3 can be achieved directly
(procedure B) from N-tert-butylacetimine 1 (Scheme 3).
NtBu
NtBu
2
LDA - THF, -50°C; 2 ClSiMe , -50°C
20°C
Me Si
3
3
Procedure B, yield = 65%
1
SiMe3
3
NtBu
1
°- 1 ClSiMe3
yield = 80%
°- 1 LDA
Me Si
1°- 1 LDA
3
2
2
2°- 1 ClSiMe3
yield = 62%
Procedure A, yield = 50%
Scheme 3

1
888
M. BELLASSOUED ET AL.
Reaction of the Disilylated Acetimine 3 with Benzaldehyde
The choice of the catalyst and the solvent is important in stereochemical outcomes and
yields. Thus, our first investigations were focused on the reaction of 3 with benzaldehyde
in the presence of several catalysts in different solvents in order to obtain the best yield
associated with the highest E stereoselectivity. Results are reported in Table I.
The attempts carried out with Lewis acids (entries 1–6) show that zinc bromide (20%)
in THF at room temperature for 24 h affords the expected enone 4a in good yield and with
very high E stereoselectivity (entry 3).
For the fluoride-catalyzed reaction of 3 with benzaldehyde, several sources of fluoride
ion have been tested (entries 7–16). From the reported examples, CsF and TBAF in THF
(entries 7–11) can be considered as the most active catalysts. However, TBAF is less
hygroscopic and commercially available in THF.
On the basis of these results, TBAF in THF (entry 8) is selected as the representative
catalyst and employed throughout this work.
Stereoselective Synthesis of (E)-α,β-Unsaturated Methyl Ketones 4
From the results reported in Table II, the reaction of the bis(trimethylsilyl) N-tert-
butyl ketimine 3 was exceptionally effective for a large class of aldehydes. Aromatic
Table I Results of reaction of 3 with benzaldehyde in the presence of several catalysts in different solvents
NtBu
O
Me Si
3
1°- catalyst, solvent
°- H O-ZnCl2
PhCHO
+
Ph
2
2
3
a
SiMe3
4a
a
E/Zb
Entry
Catalyst
Solvent
Reaction conditions
5 h, rt
Yield (%) 4a
1
2
3
4
5
6
7
8
9
1eq. ZnBr2
20% ZnBr2
20% ZnBr2
10% ZnBr2
10% ZnBr2
10% BF3
10% TBAF
20% TBAF
20% TBAF
20% TBAF
20% CsF
20% CsF
20% CsF
20% NaF
20% KF
20% LiF
THF
THF
THF
THF
Toluene
Ether
THF
THF
THF
THF
THF
DMSO
DMF
THF
THF
THF
90
83
95
83
80
47
84
97
76
95
90
76
88
82
80
10
100/0
100/0
100/0
100/0
70/30
70/30
87/13
100/0
80/20
100/0
100/0
70/30
77/23
70/30
67/33
100/0
5 h, rt
24 h, rt
24 h, rt
24 h, rt
24 h, rt
5 h, rt
5 h, rt
◦
◦
72 h, −5 C
1
1
1
1
1
1
1
0
1
2
3
4
5
6
72 h, −5 C then 3 h, rt
24 h, rt
24 h, rt
24 h, rt
24 h, rt
72 h, rt
72 h, rt
a
1
Estimated by H NMR on the crude reaction mixture with respect to nonreacted benzaldehyde (molar per-
centage).
b
1
The stereoselectivity of the compound 4a is determined by the H NMR spectrum of the crude product.

(
E)-α,β-UNSATURATED METHYL KETONES
1889
Table II Synthesis of α,β-unsaturated methyl ketones 4 using reagent 3
Entry
1
Starting aldehydes
Time (h)
5
Unsaturated methyl ketones
4
Yield (%)a E/Zb Ref.
C6H5 − CHO
O
4a
97
85
100/0 [6]
90/10 [7]
6 5
C H
2
3
4
4-CNC6H4 CHO
4-CIC6H4 CHO
5
6
6
O
4b
4c
4d
4
6 4
-CN-C H
O
90
80
87/13 [8]
100/0 [9]
4
6 4
-Cl-C H
4-Me2NC6H4 CHO
O
4
2 6 4
-Me N-C H
5
6
4-PhOC6H4 CHO
4-MeOC6H4 CHO
5.5
5.5
O
4e
4f
87
80
94/6 [10]
93/7 [11]
4
-Ph-O-C H
6
4
O
4
-Me-O-C
6
H
4
7
CHO
1
O
O
4g
86
87/13 [12]
N
N
8
9
O
5
5
4h
4i
97
82
92/8 [13]
94/6 [14]
CHO
O
O
S
CHO
S
1
1
0
1
CHO
Ph
3
2
O
4j
92
70/30 [15]
100/0 [16]
Ph
O
4k
100
CHO
1
1
2
3
CHO
CHO
1
O
4l
90
85
100/0 [16]
100/0 [16]
1.5
O
4m
1
4
2.5
O
4n
100
100/0 [17]
CHO
aIsolated yield.
b
1
The stereoselectivity of each compound is determined by the H NMR spectrum of the crude product.
(entries 1–6) and heteroaromatic aldehydes (entries 7–9) were tested and gave the corre-
sponding α,β-ethylenic methyl ketone in good yield and with a high E-stereoselectivity.
Saturated aldehydes (entries 11–14) undergo rapid condensation with 3 and afford only
the E isomer. The reaction has also been performed on one α,β-ethylenic aldehyde (entry
10), and conjugated enones, resulting from 1,2 addition, are exclusively formed in good
yield.

1
890
M. BELLASSOUED ET AL.
As can be seen from the reported examples, the reaction of the disilylated reagent 3
with aldehydes exhibits high E-selectivity. This is not the case of the lithium derivative of
5
the monosilylated N-tert-butylacetimine 2.
Reaction Mechanism
A tentative reaction mechanism with a fluoride ion is shown in Scheme 4. It is
very reasonable to assume that the reaction is initiated by a fluoride ion to generate the
ꢁ
ꢁ
carbanion 3 , which then reacts with benzaldehyde to give the alkoxide 5 a. The reaction
ꢁ
of the latter with 3 affords the intermediate 5a and the regenerated carbanion 3 in the
reaction media. Further elimination of trimethylsilyl alkoxide gives the corresponding α,β-
unsaturated imine 6a. Alternatively, the reaction could also be catalyzed by the in situ
−
formed Me3SiO . Mild acidic hydrolysis of 6a affords the expected E-benzylideneacetone
4a.
NtBu
NtBu
Me Si
Me Si
3
3
FSiMe3
+
Ph-CH = O
SiMe3
F
3'
OSiMe3
3
a
O
NtBu
NtBu
3
3
'
+
Ph
Ph
F
SiMe3
SiMe3
5'a
5a
NtBu
O
H O
FSiMe3
+
Me SiO
3
+
2
Ph
Ph
ZnCl2
6
a
4a
Scheme 4
Concerning the stereoselection of the reaction, in all cases, E isomers are formed
exclusively or in majority. This result is very likely due to a thermodynamical control of
the reaction (Table I, entries 8–10). Our attempts to isolate the intermediate 5a (Scheme 4),
in order to study the correlation between the elimination mechanism and the product
stereochemistry, have failed. Indeed, condensation and elimination reactions must be fast,
even at low temperature (Table I, entry 9). However, the unsaturated imine 6a (Scheme 4)
has been isolated and characterized.

(
E)-α,β-UNSATURATED METHYL KETONES
1891
CONCLUSION
In conclusion and from the results obtained in this study, the disilylated acetimine 3
has proved to be a versatile organosilicon reagent for the direct homologation of aldehydes
into α,β-ethylenic methyl ketones. Indeed, α,α-bis(trimethylsilyl) N-tert-butyl ketimine
3
reacts with various aldehydes in the presence of a catalytic amount of TBAF at room
temperature to give the desired α,β-enones 4 with an excellent E stereoselectivity. This is
not the case of the unsaturated methyl ketones prepared using the monosilylated acetimine
5
2.
EXPERIMENTAL
All reactions involving water-sensitive compounds are carried out in oven-dried
glassware and under nitrogen atmosphere. Unless otherwise noted, starting materials were
purchased from commercial sources and used as received. All the solvents were dried and
distilled prior to use. LDA was prepared in situ from diisopropylamine and n-butyl lithium
(2.5 M solution in hexane).
1H and 13C NMR spectra were recorded at 250 MHz using CDCl3 or acetone-d6 as
solvent. Chemical shifts are given in ppm (J in Hz) relative to chloroform or acetone. Flash
chromatography was done on Merck grade 60 silica gel (230–400 mesh) using mixtures of
cyclohexane and ethyl acetate as eluent. Melting points were uncorrected.
Preparation of Zinc Bromide
Zinc bromide was prepared by heating ground zinc (3.6 g, 55 mmol) and 1,2-
dibromoethane (9.4 g, 50 mmol) in THF (100 mL) for 16 h at reflux. The resulting solution
was allowed to cool slowly at room temperature. The remaining excess zinc was removed
by filtration. Complete evaporation of the solvent under high vacuum gave pure ZnBr2 as
a white powder.1
Preparation of N-tert-Butylacetimine 1
The acetimine 1 is prepared according to the procedure described by Taguchi and
3
Westheimer with a minor modification: To a solution of acetone (0.5 mol, 29 g), tert-
butylamine (0.55 mol, 40 g), pyridine (2 mL), and pentane (150 mL), 40 g of molecular
sieves (4Å) were added. The mixture was left at room temperature for 24 h, then the
molecular sieves were filtered from the solution and washed with pentane (20 mL). The
solvent and the nonreacted reagents were removed by simple distillation and the product
◦
was purified by fractionally distillation. Bp: 94 C/760 mmHg; yield = 56%.
Preparation of α-(Trimethylsilyl) N-tert-Butylacetimine 2
◦
To a cooled (−50 C) solution of LDA (50 mmol) in anhydrous THF (50 mL), a
solution of N-tert-butylacetimine 1 (5.05 g, 50 mmol) in THF (5 mL) was added. The
◦
resulting mixture was stirred at −50 C for 18 h. Trimethylchlorosilane (6.5 mL, 50 mmol)
◦
was added at −50 C, and the solution was stirred for 1 h at this temperature. Then, the
solution was gradually warmed to room temperature and filtered through a pad of Celite.

1
892
M. BELLASSOUED ET AL.
The solvent was removed under reduced pressure, and distillation of the remaining oil gave
the monosilylated acetimine 2.
◦
1
Bp: 65 C/15 mmHg; yield = 80%. H NMR (250 MHz, CDCl3) δ = 0.06 (s, 9H,
SiMe3), 1.26 (s, 9H, tBu), 1.78 (s, 2H, CH2), 1.88 (s, 3H, CH3). Anal. Calc for C10H23NSi:
C, 64.86; H, 12.43. Found: C, 64.26; H, 12.13.
Preparation of α,α-Bis(trimethylsilyl) N-tert-Butylacetimine 3
◦
Procedure A. To a cooled (−50 C) solution of LDA (50 mmol) in anhydrous THF
(
(
(
50 mL), a solution of α-(trimethylsilyl)N-tert-butylacetimine 2 (8.65 g, 50 mmol) in THF
◦
5 mL) was added. The resulting mixture was stirred at −50 C for 4 h. Trimethylchlorosilane
◦
6.5 mL, 50 mmol) was added at −50 C, and the solution was stirred for 1 h at this
temperature. The solution was then gradually warmed to room temperature and filtered
through a pad of Celite. The solvent was removed under reduced pressure, and distillation
of the remaining oil gave the disilylated acetimine 3.
◦
1
Bp: 106 C/12 mmHg; yield = 62%. H NMR (250 MHz, CDCl3) δ = 0.07 (s, 18H,
2
SiMe3), 1.25 (s, 10H, tBu, CH), 1.89 (s, 3H, CH3). Anal. Calc for C13H31NSi2: C, 60.70;
H, 12.06. Found: C, 60.52; H, 12.15.
Procedure B. The compound 3 can also be prepared directly from 1. To a cooled
◦
(
−50 C) solution of LDA (100 mmol) in anhydrous THF (50 mL), 1 (5.05 g, 50 mmol)
◦
was added dropwise at −50 C. The mixture was stirred at this temperature for 18 h.
Trimethylchlorosilane was added in two portions: the first portion of TMSCl (6.5 mL,
◦
5
0 mmol) was added at −50 C, and the solution was stirred for 5 h at this temperature,
then the second portion (6.5 mL, 50 mmol) was added, and the solution was stirred for 45
◦
min at −50 C. Slow warming to room temperature of the resulting mixture was followed
by filtration through a pad of Celite and evaporation of solvents at reduced pressure. The
distillation of the remaining oil gave 3; yield = 65%.
Preparation of α,β-Unsaturated Methylketones 4a–n
A detailed procedure for the reaction of 3 with aldehydes in THF using TBAF (20%)
as catalyst is given below. All reactions are carried out in similar manner under nitrogen
atmosphere.
Reaction times, yields, and the E/Z ratios are reported in Table II. Physical, spectral,
and analytical data for the obtained unsaturated methylketones follow.
To a stirred solution of aldehyde (10 mmol) and reagent 3 (2.45 g, 10 mmol) in
THF (10 mL), TBAF (2 mmol) was added dropwise at room temperature; the reaction was
◦
exothermic. The temperature was maintained at 20–25 C with a water bath. The reaction
was checked using TLC until disappearance of the starting aldehyde. Then, the resulting
mixture was hydrolyzed by addition of an aqueous solution of ZnCl2 (2 g in 20 mL of
water) and ether (25 mL), and the solution was stirred for 1 h at room temperature. The
precipitate was filtered through a pad of celite. The aqueous layer was extracted with ether
(
2 × 25 mL), and the combined organic extracts were washed with water (10 mL) and dried
over MgSO4. The solvent was removed in vacuo. The reaction crude was purified by flash
chromatography to give the corresponding products 4a–n.
1
(
E)-4-Phenylbut-3-en-2-one (4a). H NMR (250 MHz, CDCl3) δ = 2.38 (s, 3H,
13
CH3), 6.71 (d, 1H, J = 16 Hz), 7.50 (d, 1H, J = 16 Hz), 7.3–7.62 (m, 5H, Ar). C NMR

(
E)-α,β-UNSATURATED METHYL KETONES
1893
−
1
(
1
250 MHz, CDCl3) δ = 28.4, 126.5, 129.4, 142.8, 196.0. IR (neat): 1701 cm (C O),
−1
597 cm (C C). Anal. Calc for C10H10O: C, 82.19; H, 6.85. Found: C, 82.37; H, 6.45.
1
(
Z)-4-Phenylbut-3-en-2-one (4a). H NMR (250 MHz, CDCl3) δ = 2.17 (s, 3H,
13
CH3), 6.30 (d, 1H, J = 12 Hz), 7.09 (d, 1H, J = 12 Hz), 7.38–7.90 (m, 5H, Ar). C NMR
−1
(
1
250 MHz, CDCl3) δ = 31.2, 124.3, 128.1, 141.7, 192.9. IR (neat): 1670 cm (C O),
−1
618 cm (C C). Anal. Calc for C10H10O: C, 82.19; H, 6.85. Found: C, 82.52; H, 6.75.
1
(
E)-4-(3-Oxobut-1-enyl)benzonitrile (4b). H NMR (250 MHz, CDCl3) δ =
2
.39 (s, 3H, CH3), 6.69 (d, 1H, J = 16.4 Hz), 7.43 (d, 1H, J = 16.4 Hz), 7.30–7.60 (m, 4H,
13
Ar). C NMR (250 MHz, CDCl3) δ = 29.4, 126.4, 130.1, 138.4, 142.9, 197.3. IR (neat):
−1
−1
1
681 cm (C O), 1616 cm (C C). Anal. Calc for C11H9NO: C, 77.19; H, 5.26. Found:
C, 77.34; H, 5.32.
Z)-4-(3-Oxobut-1-enyl)benzonitrile (4b). H NMR (250 MHz, CDCl3) δ =
.19 (s, 3H, CH3), 6.03 (d, 1H, J = 12.5 Hz), 6.88 (d, 1H, J = 12.5 Hz), 7.29–7.68 (m, 4H,
1
(
2
13
Ar). C NMR (250 MHz, CDCl3) δ = 31.2, 125.9, 131.6, 139.2, 142.7, 198.5. IR (neat):
−1
−1
1
673 cm (C O), 1620 cm (C C). Anal. Calc for C11H9NO: C, 77.19; H, 5.26. Found:
C, 77.32; H, 5.15.
1
(
E)-4-(4-Chlorophenyl) but-3-en-2-one (4c). H NMR (250 MHz, CDCl3) δ =
2
4
.40 (s, 3H, CH3), 6.68 (d, 1H, J = 16.3 Hz), 7.41 (d, 1H, J = 16.3 Hz), 7.05–7.55 (m,
13
H, Ar). C NMR (250 MHz, CDCl3) δ = 28.4, 126.7, 129.9, 135.4, 141.9, 198.3. IR
−1
−1
(
neat): 1675 cm (C O), 1621 cm (C C). Anal. Calc for C10H9ClO: C, 66.48; H, 4.99.
Found: C, 66.12; H, 4.79.
1
(
Z)-4-(4-Chlorophenyl) but-3-en-2-one (4c). H NMR (250 MHz, CDCl3) δ =
2
4
(
.21 (s, 3H, CH3), 5.95 (d, 1H, J = 12.3 Hz), 6.68 (d, 1H, J = 12.3 Hz), 7.10–7.70 (m,
13
H, Ar). C NMR (250 MHz, CDCl3) δ = 31.2, 125.9, 128.7, 136.5, 142.3, 197.7. IR
−1
−1
neat): 1665 cm (C O), 1630 cm (C C). Anal. Calc for C10H9ClO: C, 66.48; H, 4.99.
Found: C, 66.22; H, 4.59.
E)-4-(4-(Dimethylamino) phenyl) but-3-en-2-one (4d). H NMR (250 MHz,
1
(
CDCl3) δ = 2.37 (s, 3H, CH3), 2.82 (s, 6H, 2CH3), 6.64 (d, 1H, J = 16.2 Hz), 6.45–7.26
1
3
(
1
m, 4H, Ar), 7.48 (d, 1H, J = 16.2 Hz). C NMR (250 MHz, CDCl3) δ = 29.2, 41.1, 114.1,
− −1
1
26.7, 127.8, 139.8, 144.1, 198.3. IR (neat): 1671 cm (C O), 1627 cm (C C). Anal.
Calc for C12H15NO: C, 76.19; H, 7.94. Found: C, 76.29; H, 7.78.
1
(
E)-4-(4-Phenoxyphenyl) but-3-en-2-one (4e). H NMR (250 MHz, CDCl3)
δ = 2.25 (s, 3H, CH3), 6.55 (d, 1H, J = 16.27 Hz), 7.33 (d, 1H, J = 16.27 Hz), 6.6–7.4
1
3
(
m, 9H, Ar). C NMR (250 MHz, CDCl3) δ = 27.9, 128.0, 143.2, 198.8. IR (neat): 1675
−1
−1
cm (C O), 1616 cm (C C).Anal. Calc for C16H14O2: C, 80.67; H, 5.88. Found: C,
0.17; H, 5.80.
Z)-4-(4-Phenoxyphenyl) but-3-en-2-one (4e). H NMR (250 MHz, CDCl3)
δ = 2.17 (s, 3H, CH3), 6.05 (d, 1H, J = 12.66 Hz), 6.79 (d, 1H, J = 12.66 Hz), 6.6–7.4
8
1
(
13
(
m, 9H, Ar). C NMR (250 MHz, CDCl3) δ = 25.9, 130.0, 139.6, 192.1. IR (neat): 1664
1
−
−1
cm (C O), 1621 cm (C C). Anal. Calc for C16H14O2: C, 80.67; H, 5.88. Found: C,
0.47; H, 5.57.
E)-4-(4-Methoxyphenyl) but-3-en-2-one (4f). H NMR (250 MHz, CDCl3)
8
1
(
δ = 2.33 (s, 3H, CH3), 3.78 (s, 3H, CH3O), 6.54 (d, 1H, J = 16.2 Hz), 7.41 (d, 1H, J =
1
3
1
1
6.2 Hz), 6.9–7.5 (m, 4H, Ar). C NMR (250 MHz, CDCl3) δ = 27.8, 55.7, 114.71, 125.4,
1
−
−1
30.3, 132.2, 143.6, 162.0, 198.8. IR (neat): 1678 cm (C O), 1610 cm (C C). Anal.
Calc for C11H12O2: C, 75.00; H, 6.81. Found: C, 75.12; H, 6.62.
1
(
Z)-4-(4-Methoxyphenyl) but-3-en-2-one (4f). H NMR (250 MHz, CDCl3)
δ = 2.16 (s, 3H, CH3), 3.85 (s, 3H, CH3O), 6.07 (d, 1H, J = 12.6 Hz), 6.91 (d, 1H, J = 12.6

1
894
M. BELLASSOUED ET AL.
Hz), 6.71–7.55 (m, 4H, Ar). 13C NMR (250 MHz, CDCl3) δ = 25.3, 56.0, 114.0, 127.2,
− −1
1
1
29.1, 132.3, 142.3, 160.3, 193.2. IR (neat): 1679 cm (C O), 1618 cm (C C). Anal.
Calc for C11H12O2: C, 75.00; H, 6.81. Found: C, 75.18; H, 6.48.
1
(
E)-4-(Pyridin-3-yl) but-3-en-2-one (4g). H NMR (250 MHz, CDCl3) δ = 2.39
(
s, 3H, CH3), 5.58 (d, 1H, J = 16.24 Hz), 6.01 (d, 1H, J = 16.24 Hz), 6.8–7.75 (m, 4H, Ar).
1
3
−1
C NMR (250 MHz, CDCl3) δ = 29.4, 127.5, 129.9, 143.8, 196.8. IR (neat): 1668 cm
−1
(
C O), 1614 cm (C C). Anal. Calc for C9H9NO: C, 73.47; H, 6.12. Found: C, 73.97;
H, 6.22.
1
(
Z)-4-(Pyridin-3-yl) but-3-en-2-one (4g). H NMR (250 MHz, CDCl3) δ = 2.24
(
s, 3H, CH3), 5.47 (d, 1H, J = 12.3 Hz), 6.02 (d, 1H, J = 12.3 Hz), 7.07–8.10 (m, 4H, Ar).
1
3
−1
C NMR (250 MHz, CDCl3) δ = 31.2, 126.9, 130.1, 144.2, 198.1. IR (neat): 1674 cm
−1
(
C O), 1621 cm (C C). Anal. Calc for C9H9NO: C, 73.47; H, 6.12. Found: C, 73.26;
H, 6.15.
1
(
E)-4-(Furan-2-yl) but-3-en-2-one (4h). H NMR (250 MHz, CDCl3) δ = 2.26
(
s, 3H, CH3), 6.42 (d, 1H, J = 15.9 Hz), 7.33 (d, 1H, J = 15.9 Hz), 6.2–7.4 (m, 3H, Ar).
1
3
C NMR (250 MHz, CDCl3) δ = 28.2, 112.9, 113.0, 124.6, 129.8, 143.2, 145.4, 198.2. IR
− −1
1
(
neat): 1690 cm (C O), 1610 cm (C C). Anal. Calc for C8H8O2: C, 70.59; H, 5.88.
Found: C, 70.18; H, 5.68.
1
(
Z)-4-(Furan-2-yl) but-3-en-2-one (4h). H NMR (250 MHz, CDCl3) δ = 2.15
(
s, 3H, CH3), 6.01 (d, 1H, J = 12.7 Hz), 6.85 (d, 1H, J = 12.7 Hz), 7.05–7.40 (m, 3H, Ar).
1
3
C NMR (250 MHz, CDCl3) δ = 31.6, 110.6, 114.1, 123.5, 129.6, 144.9, 151.2, 198.2. IR
−1 −1
(
neat): 1681 cm (C O), 1619 cm (C C). Anal. Calc for C8H8O2: C, 70.59; H, 5.88.
Found: C, 70.71; H, 5.67.
E)-4-(Thiophen-2-yl) but-3-en-2-one (4i). H NMR (250 MHz, CDCl3) δ =
.29 (s, 3H, CH3), 6.47 (d, 1H, J = 15.9 Hz), 6.5–7.5 (m, 3H, Ar), 7.61 (d, 1H, J = 15.9
1
(
2
13
Hz). C NMR (250 MHz, CDCl3) δ = 29.1, 127.0, 129.9, 130.1, 132.8, 134.8, 137.7,
−1
−1
1
95.8. IR (neat): 1664 cm (C O), 1595 cm (C C). Anal. Calc for C8H8SO: C, 63.16;
H, 5.26. Found: C, 63.25; H, 5.15.
1
(
Z)-4-(Thiophen-2-yl) but-3-en-2-one (4i). H NMR (250 MHz, CDCl3) δ =
2
3
1
.16 (s, 3H, CH3), 6.07 (d, 1H, J = 12.2 Hz), 6.60 (d, 1H, J = 12.2 Hz), 6.90–7.45 (m,
13
H, Ar). C NMR (250 MHz, CDCl3) δ = 23.6, 126.9, 129.6, 129.9, 130.1, 133.8, 138.2,
−1
−1
85.7. IR (neat): 1670 cm (C O), 1610 cm (C C). Anal. Calc for C8H8SO: C, 63.16;
H, 5.26. Found: C, 63.55; H, 5.33.
1
(
3E, 5E)-6-Phenylhexa-3, 5-dien-2-one (4j). H NMR (250 MHz, CDCl3) δ =
2
1
.26 (s, 3H, CH3), 6.01 (d, 1H, J = 15.3 Hz), 6.28 (dd, 1H, J = 15.3, 10.2 Hz), 6.31 (d,
13
H, J = 15.3 Hz), 6.42 (dd, 1H, J = 15.3, 10.2 Hz), 7.25–7.48 (m, 5H, Ar). C NMR (250
MHz, CDCl3) δ = 31.2, 130.1, 132.4, 134.3, 137.8, 139.5, 139.7, 143.2, 194.3. IR (neat):
−1
−1
1
674 cm (C O), 1612 cm (C C). Anal. Calc for C12H12O: C, 83.72; H, 6.97. Found:
C, 83.31; H, 6.78.
1
(
3Z, 5E)-6-Phenylhexa-3,5-dien-2-one (4j). H NMR (250 MHz, CDCl3) δ =
2
1
.21 (s, 3H, CH3), 6.11 (d, 1H, J = 11.6 Hz), 6.15 (dd, 1H, J = 11.6, 7.2 Hz), 6.40 (d,
13
H, J = 15.8 Hz), 6.42 (dd, 1H J = 15.8, 7.2 Hz), 7.01–7.41 (m, 5H, Ar). C NMR (250
MHz, CDCl3) δ = 28.1, 128.9, 130.8, 132.5, 136.1, 138.7, 139.1, 144.9, 190.1. IR (neat):
−1
−1
1
670 cm (C O), 1619 cm (C C). Anal. Calc for C12H12O: C, 83.72; H, 6.97. Found:
C, 83.47; H, 6.67.
E)-Hex-3-en-2-one (4k). H NMR (250 MHz, CDCl3) δ = 0.89 (t, 3H, CH3),
.97 (m, 2H, CH2), 2.35 (s, 3H, COCH3), 5.97 (d, 1H, J = 16.16 Hz), 6.63 (dt, 1H,
1
(
1

(
E)-α,β-UNSATURATED METHYL KETONES
1895
13
J = 16.16 Hz). C NMR (250 MHz, CDCl3) δ = 10.9, 23.5, 31.3, 130.5, 145.3, 197.9. IR
−1
−1
(
neat): 1687 cm (C O), 1624 cm (C C). Anal. Calc for C6H10O: C, 73.47; H, 10.20.
Found: C, 73.89; H, 10.32.
1
(
E)-Hept-3-en-2-one (4l). H NMR (250 MHz, CDCl3) δ = 0.95 (t, 3H, CH3),
1
1
3
.75 (m, 2H, CH2), 2.05 (m, 2H, CH2 = CH), 2.37 (s, 3H, COCH3), 6.01 (d, 1H, J =
13
6.28 Hz), 6.59 (dt, 1H, J = 16.28 Hz). C NMR (250 MHz, CDCl3) δ = 10.9, 23.6, 32.5,
−1
−1
4.5, 129.5, 146.4, 197.7. IR (neat): 1697 cm (C O), 1629 cm (C C). Anal. Calc for
C7H12O: C, 75.00; H, 10.71. Found: C, 75.12; H, 10.51.
1
(
E)-Oct-3-en-2-one (4m). H NMR (250 MHz, CDCl3) δ = 0.92 (t, 3H, CH3),
1
.15–1.84 (m, 4H, 2 CH2), 2.25 (m, 2H, CH2CH = ), 2.34 (s, 3H, COCH3), 6.03 (d, 1H,
13
J = 16.26 Hz), 6.63 (dt, 1H, J = 16.26 Hz). C NMR (250 MHz, CDCl3) δ = 11.5, 24.6,
−1
−1
2
8.9, 31.8, 32.3, 124.4, 156.3, 197. IR (neat): 1695 cm (C O), 1625 cm (C C). Anal.
Calc for C8H14O: C, 76.19; H, 11.11. Found: C, 76.79; H, 11.41.
1
(
E)-5,5-Dimethylhex-3-en-2-one (4n). H NMR (250 MHz, CDCl3) δ = 1.04
13
(
s, 9H, tBu), 2.22 (s, 3H, COCH3), 5.93 (d, 1H, J = 16.2 Hz), 6.73 (d, 1H, J = 16.2 Hz). C
−1
NMR (250 MHz, CDCl3) δ = 28.9, 31.8, 32.3, 124.4, 156.3, 197.6. IR (neat): 1678 cm
−1
(
C O), 1622 cm (C C). Anal. Calc for C8H14O: C, 76.19; H, 11.11. Found: C, 76.68;
H, 11.52.
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