Synthesis of substituted hexa-3,5-dienoic acid methyl esters from conjugated dienones

Article abstract of DOI:10.1039/b101242h

Substituted hexa-3,5-dienoic acid methyl esters (2) were conveniently prepared in one step by 1,2-carbonyl transposition of the corresponding dienones (1) using lead(IV) acetate and boron trifluoride-diethyl ether in benzene at room temperature.

Full text of DOI:10.1039/b101242h

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Synthesis of substituted hexa-3,5-dienoic acid methyl esters from
conjugated dienones
Rishan Lang Nongkhlaw, Ridaphun Nongrum and Bekington Myrboh*
1
Department of Chemistry, North Eastern Hill University, Shillong-793022, Meghalaya, India
Received (in Cambridge, UK) 7th February 2001, Accepted 4th April 2001
First published as an Advance Article on the web 4th May 2001
Substituted hexa-3,5-dienoic acid methyl esters (2) were conveniently prepared in one step by 1,2-carbonyl
transposition of the corresponding dienones (1) using lead() acetate and boron trifluoride–diethyl ether in benzene
at room temperature.
Introduction
Hexa-3,5-dienoic acid methyl esters are important synthons in
organic synthesis. The unsubstituted diene is one of the key
intermediates used for the synthesis of the “southern” half of
vitamin B12.1 It has also been used as an intermediate in the
synthesis of the alkaloid lycorine.2 Although there is a vast
amount of literature on the synthesis of its conjugated analogs,
our literature survey showed that there are only few reports that
describe the synthesis of this class of compounds. Some of the
reported methods include the following: (i) the Rh-catalysed
C–C coupling of allene with but-3-enoic acid to give a mixture
of esters of hexa-3,5-dienoic acid in a 9 : 1 ratio;3 (ii) the
transition-metal-catalysed reaction of styrene with but-3-enoic
acid;4 and (iii) the reaction of allylic alcohols with acetylene,
CO and MeOH (as described in an Italian patent) in the pres-
Scheme 1
ence of an NiBr2–phosphine complex to yield two products,
1H NMR analysis of two reaction mixtures in which
one of which is the title compound.5 Other methods include the
use of Li–diisopropylamide–HMPA in THF to deconjugate
methyl sorbate to the corresponding diene.6
R1 = OMe and R2 = Me, CH2Me showed the presence of
methylene protons as multiplets at ca. δ 1.87 and 1.71, while 13
C
NMR showed a resonance at ca. δ 12.3, suggesting the presence
of the cyclopropyl intermediate 6, which evidently rearranges
to the more stable product 2 during work-up.
Previously we have illustrated the successful use of lead()
acetate in combination with Lewis acids to effect a 1,2-carbonyl
transposition in acetophenones7 and acyclic α,β-unsaturated
ketones8 and a ring contraction in cyclic α,β-unsaturated
ketones and related systems.9a–c As part of our continuing work
to test the effectiveness of this reagent combination, we inserted
one more double bond between the carbonyl and the benzyl-
idene system to see whether the presence of the doubly
conjugated moiety in the ketone (1) would also facilitate a 1,2-
carbonyl shift.
Results and discussion
For this investigation we have chosen ketones 1 (Table 1),
which were prepared in two steps by successive condensation of
an aromatic aldehyde with an aliphatic aldehyde and then with
an aliphatic ketone. At each step the products were purified by
column chromatography before proceeding to the next reaction.
Thus, the starting material (1), which possesses an E geometry
at the 3-position, reacts with lead() acetate in the presence
of boron trifluoride–diethyl ether and methanol in benzene at
Ϫ30 ЊC to give the product 2 in which the stereochemistry is
retained or changed depending on the nature of the substituent
R2. As R2 becomes increasingly bulky the concentration of the
E isomer (3E) becomes greater and only a trace amount of the
Z (3Z) isomer is obtained. The stereochemistry of the double
bond at the 3-position was assigned on the basis of the coupling
constant and also on the basis of the CH2COOR signal, which
is generally at lower field for Z than for the corresponding E
compounds.10
We wish to report here a simple method for the synthesis of
5-alkyl-6-arylhexa-3,5-dienoic acid methyl ester (2) by trans-
formation of 5-alkyl-6-arylhexa-3,5-dien-2-one (1) assisted by
lead() acetate and boron trifluoride–diethyl ether (Scheme 1).
The reactions proceeded smoothly at low temperature (Ϫ30 ЊC)
to give the products in yields varying between 35 and 50%.
The mechanism for this transformation (Scheme 2) appears to
involve an initial Lewis acid-catalysed enolisation of ketone 1
to give enolate 3, which then undergoes an oxyplumbation reac-
tion in the presence of lead() acetate and MeOH to give the
organometallic intermediate 4 (not isolated). The elimination
of lead() acetate, evidently assisted by neighboring group
participation of the adjacent π electrons, resulted in the gener-
ation of a carbocation stabilized by the conjugated π system,
which, in the presence of MeOH, rearranges to the more stable
product 2.
1300
J. Chem. Soc., Perkin Trans. 1, 2001, 1300–1303
This journal is © The Royal Society of Chemistry 2001
DOI: 10.1039/b101242h

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Scheme 2
Table 1 Preparation of substituted hexa-3,5-dienoic acid methyl esters
mmol), obtained as above, dry acetone (30 mmol) was added
followed by dropwise addition of 10% sodium hydroxide solu-
tion (1.5 ml). The mixture was further stirred at room temper-
ature for another 4 hours, rendered acidic to litmus by the add-
ition of dilute hydrochloric acid and extracted with diethyl
ether. The organic layer was separated, dried and evaporated
under reduced pressure to give a brown oil. Chromatography on
silica gel using hexane as the eluent yielded the dienone
(43–58%).
Yield (%)b
Entry Productsa R1
R2
Time/h Zc
Ec
1
2
3
4
5
6
7
8
9
10
11
12
13
2a
2bd
2c
2d
2e
2f
H
H
H
H
CH3
CH2CH3 24
H
24
17
10
7
0
10
7
0
0
0
8
0
40
40
35
38
40
47
45
40
35
42
38
35
0
p-CH3
p-CH3
p-CH3
p-Cl
24
12
CH3
CH2CH3 24
CH3 24
CH2CH3 24
CH3 20
CH2CH3 24
24
3,4-di-OCH3 CH2CH3 24
p-NO2 CH3 24
2g
2h
2i
General procedure for the preparation of methyl 5-alkyl-6-
arylhexa-3,5-dienoate 2
p-Cl
p-OCH3
p-OCH3
In a typical procedure, a stirred suspension of lead() acetate
(10.5 mmol) in benzene (30 ml) was purged with nitrogen and
cooled to Ϫ30 ЊC. A solution of the dienone (1) (10 mmol) was
then added in one lot followed by MeOH (5 ml) and BF3ؒEt2O
(3 ml). The reaction mixture was allowed to warm to room
temperature and stirring was continued under nitrogen for
17–24 hours. The precipitated lead() acetate was filtered off
and the filtrate successively washed with saturated NaHCO3
solution, water and brine, dried over Na2SO4 and the solvent
removed in vacuo. The crude product was purified by column
chromatography using silica gel as the solid phase and hexane
as eluent to give the pure products (2) in varying yields
(Table 1).
2j
2k
2l
3,4-di-OCH3 CH3
0
0
0
2m
a Products are characterized by IR, 1H NMR and 13C NMR.b Refer to
isolated yields.c Based on H–H coupling constants.d The data match
those reported in the literature.3
Experimental
1H and 13C NMR spectra were recorded on a Bruker DPX 300
instrument using CDCl3 as the solvent. Chemical shifts are
reported in ppm from internal tetramethylsilane and are given
on the δ scale. J values are given in Hz. IR spectra were
recorded on a Perkin-Elmer 297 spectrophotometer. CHN
analyses were recorded in a Vario EL analyzer. Mass spectra
were recorded on a JEOL D-300 (EI) mass spectrometer.
Freshly prepared lead tetraacetate11 was used in all reactions.
Column chromatography was performed by using silica gel
(60–120 mesh, Merck).
Spectroscopic data
1
6-Phenylhexa-3,5-dien-2-one 1a.12 IR (neat): 1674 cmϪ1; H
NMR: δ 2.24 (s, 3H, COCH3), 5.96 (d, 1H, J 15.2, H-3), 6.28
(dd, 1H, J 15.2, 10.1, H-5), 6.31 (d, 1H, J 15.2, H-6), 6.42 (dd,
1H, J 15.2, 10.1, H-4), 7.25–7.48 (m, 4H, Ar-H); 13C NMR:
δ 31.2, 130.1, 132.4, 134.3, 137.4, 137.8, 139.5, 139.7, 143.2,
193.3; MS (EI) m/z (%): 172 (M+, 23), 129 (74), 77 (65), 43
(100). Anal. Calcd. for C12H12O (172): C, 83.72; H, 6.97. Found:
C, 83.80; H, 6.95%.
General procedure for the preparation of 5-alkyl-6-arylhexa-3,5-
dien-2-one 1
Step 1: preparation of 3-arylpropenaldehyde. To a cooled
(0 ЊC), stirred solution of freshly distilled aromatic aldehyde (50
mmol) and aliphatic aldehyde (50 mmol), 2 ml of 10% sodium
hydroxide solution were added dropwise. The mixture was
brought to room temperature and further stirred for another 4
hours. The solution was then rendered acidic to litmus by the
addition of dilute hydrochloric acid and extracted with diethyl
ether. The organic layer was separated, dried and evaporated
under reduced pressure to give a brown oil that was purified by
column chromatography on silica gel, using hexane as the
eluent, to give the 3-arylpropenaldehyde in yields ranging from
50 to 67%. The product obtained was then used in the next
step.
Methyl (E,E)-6-phenylhexa-3,5-dienoate 2a. IR (neat): 1738
1
cmϪ1; H NMR: δ 3.20 (d, 2H, J 7.2, CH2CO), 3.68 (s, 3H,
OCH3), 5.88 (m, 1H, H-3), 6.29 (dd, 1H, J 15.2, 10.1, H-4), 6.36
(dd, 1H, J 15.2, 10.1, H-5), 6.42 (d, 1H, J 15.2, H-6), 7.21–7.53
(m, 5H, Ar-H); 13C NMR: δ 42.1, 51.3, 129.4, 131.0, 133.6,
136.0, 137.1, 138.1, 144.2, 172.7; MS (EI) m/z (%): 202 (M+, 56),
171 (46), 143 (100), 77 (70), 59 (80). Anal. Calcd. for C13H14O2
(202): C, 77.22; H, 6.93. Found: C, 77.30; H, 6.98%.
Methyl (Z,E)-6-phenylhexa-3,5-dienoate 2a. IR (neat): 1741
1
cmϪ1; H NMR: δ 3.19 (d, 2H, J 7.2, CH2CO), 3.69 (s, 3H,
OCH3), 5.90 (m, 1H, H-3), 6.31 (dd, 1H, J 11.5, 10.1, H-4), 6.35
(dd, 1H, J 15.2, 10.1, H-5), 6.40 (d, 1H, J 15.2, H-6), 7.21–7.51
(m, 5H, Ar-H); 13C NMR: δ 40.2, 51.9, 131.2, 131.8, 134.0,
134.8, 136.1, 138.9, 143.4; MS (EI) m/z (%): 202 (M+, 31), 171
Step 2: preparation of 5-alkyl-6-arylhexa-3,5-dien-2-one 1. To
a cooled (0 ЊC), stirred solution of 3-arylpropenaldehyde (30
J. Chem. Soc., Perkin Trans. 1, 2001, 1300–1303
1301

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(26), 143 (100), 77 (68), 59 (74). Anal. Calcd. for C13H14O2
(202): C, 77.22; H, 6.93. Found: C, 77.32; H, 6.95%.
(dd, 1H, J 15.2, 10.1, H-5), 6.35 (dd, 1H, J 11.5, 10.1, H-4), 6.46
(d, 1H, J 15.2, H-6), 7.15–7.43 (m, 4H, Ar-H); 13C NMR δ 25.8,
43.2, 52.1, 128.9, 129.3, 131.6, 135.9, 136.1, 136.9, 137.4, 147.8,
173.4; MS (EI) m/z (%): 216 (M+, 31), 157 (57), 91 (100), 59
(69). Anal. Calcd. for C14H16O2 (216): C, 77.77; H, 7.40. Found:
C, 77.80; H, 7.45%.
5-Methyl-6-phenylhexa-3,5-dien-2-one 1b. IR (neat): 1675
cmϪ1; 1H NMR: δ 1.94 (s, 3H, CH3), 2.22 (s, 3H, COCH3), 5.92
(d, 1H, J 15.2, H-3), 6.30 (s, 1H, H-6), 6.39 (d, 1H, J 15.2, H-4),
7.28–7.40 (m, 5H, Ar-H); 13C NMR: δ 20.8, 29.8, 129.8, 130.1,
133.6, 136.8, 138.4, 138.7, 140.3, 142.8, 193.1; MS (EI) m/z (%):
186 (M+, 62), 143 (36), 77 (68), 43 (100). Anal. Calcd. for
C13H14O (186): C, 83.87; H, 7.52. Found: C, 83.91; H, 7.56%.
5-Methyl-6-(4-methylphenyl)hexa-3,5-dien-2-one
1e.
IR
(neat): 1673 cmϪ1; H NMR: δ 1.93 (s, 3H, CH3), 2.00 (s, 3H,
Ar-CH3), 2.23 (s, 3H, COCH3), 5.93 (d, 1H, J 15.2, H-3), 6.34
(s, 1H, H-6), 6.46 (d, 1H, J 15.2, H-4), 7.20–7.45 (m, 4H, Ar-H);
13C NMR: δ 22.0, 24.8, 30.7, 128.4, 131.8, 133.4, 135.6, 136.3,
138.3, 143.2, 147.4, 192.8; MS (EI) m/z (%): 200 (M+, 58), 157
(47), 91 (100), 43 (74). Anal. Calcd. for C14H16O (200): C, 84.0;
H, 8.0. Found: C, 84.07; H, 8.06%.
1
Methyl (E,E)-5-methyl-6-phenylhexa-3,5-dienoate 2b. IR
1
(neat): 1736 cmϪ1; H NMR: δ 1.95 (s, 3H, CH3), 3.19 (d, 2H,
J 7.2, CH2CO), 3.70 (s, 3H,OCH3), 5.86 (m, 1H, H-3), 6.30 (d,
1H, J 15.2, H-4), 6.45 (s, 1H, H-6), 7.18–7.42 (m, 5H, Ar-H);
13C NMR: δ 21.6, 37.4, 51.8, 129.4, 130.2, 134.3, 135.6, 138.7,
139.6, 142.1, 172.5; MS (EI) m/z (%): 216 (M+, 47), 157 (100),
77 (71), 59 (67). Anal Calcd. for C14H16O2 (216): C, 77.77; H,
7.40. Found: C, 77.85; H, 7.51%.
Methyl (E,E)-5-methyl-6-(4-methylphenyl)hexa-3,5-dienoate
2e. IR (neat): 1738 cmϪ1; 1H NMR: δ 1.92 (s, 3H, CH3), 1.98 (s,
3H, Ar-CH3), 3.23 (d, 2H, J 7.2, CH2CO), 3.68 (s, 3H, OCH3),
5.84 (m, 1H, H-3), 6.25 (d, 1H, J 15.2, H-4), 6.48 (s, 1H, H-6),
7.21–7.50 (m, 4H, Ar-H); 13C NMR: δ 20.8, 25.0, 45.2, 51.1,
129.1, 131.4, 135.2, 136.3, 138.2, 138.5, 148.4, 170.8; MS (EI)
m/z (%): 230 (M+, 61), 171 (71), 91 (100), 59 (60). Anal. Calcd
for C15H18O2 (230): C, 78.26; H, 7.82. Found: C, 78.31; H,
7.86%.
Methyl (Z,E)-5-methyl-6-phenylhexa-3,5-dienoate 2b. IR
1
(neat): 1738 cmϪ1; H NMR: δ 1.95 (s, 3H, CH3), 3.18 (d, 2H,
J 7.2, CH2CO), 3.68 (s, 3H, OCH3), 5.82 (m, 1H, H-3), 6.30 (d,
1H, J 11.5, H-4), 6.42 (s, 1H, H-6), 7.14–7.41 (m, 5H, Ar-H);
13C NMR: δ 21.3, 40.8, 51.6, 126.8, 129.9, 130.1, 133.0, 134.5,
136.9, 138.5, 140.1, 171.7; MS (EI) m/z (%): 216 (M+, 32), 157
(100), 77 (74), 59 (81). Anal. Calcd. for C14H16O2 (216): C,
77.77; H, 7.40. Found: C, 77.81; H, 7.46%.
Methyl (Z,E)-5-methyl-6-(4-methylphenyl)hexa-3,5-dienoate
2e. IR (neat): 1739 cmϪ1; 1H NMR: δ 1.95 (s, 3H, CH3), 2.00 (s,
3H, ArCH3), 3.21 (m, 2H, J 7.2, CH2CO), 3.71 (s, 3H, OCH3),
5.87 (m, 1H, H-3), 6.28 (d, 1H, J 11.5, H-4), 6.48 (s, 1H, H-6),
7.10–7.44 (m, 4H, Ar-H); 13C NMR: δ 21.7, 26.3, 44.3, 52.6,
128.7, 132.6, 135.4, 136.4, 137.3, 137.7, 138.1, 148.1, 171.0; MS
(EI) m/z (%): 230 (M+, 55), 171 (39), 91 (100), 59 (75). Anal.
Calcd for C15H18O2 (230): C, 78.26; H, 7.82. Found: C, 78.36; H,
7.90%.
5-Ethyl-6-phenylhexa-3,5-dien-2-one 1c. IR (neat): 16.74
1
cmϪ1; H NMR: δ 1.03 (t, 3H, J 7.3, CH2CH3), 2.20 (q, 2H,
J 7.3, CH2CH3), 2.24 (s, 3H, COCH3), 5.90 (d, 1H, J 15.2, H-3),
6.33 (s, 1H, H-6), 6.44 (d, 1H, J 15.2, H-4), 7.21–7.43 (m, 5H,
Ar-H); 13C NMR: δ 16.7, 29.0, 31.5, 129.4, 131.7, 133.8, 136.2,
136.8, 137.4, 139.7, 145.3, 193.7; MS (EI) m/z (%): 200 (M+, 61),
157 (41), 77 (56), 43 (100). Anal. Calcd. for C14H16O (200): C,
84.00; H, 8.0. Found: C, 84.10; H, 8.02%.
5-Ethyl-6-(4-methylphenyl)hexa-3,5-dien-2-one 1f. IR (neat):
1674 cmϪ1; 1H NMR: δ 1.05 (s, 3H, J 7.3, CH2CH3), 1.94 (s, 3H,
ArCH3), 2.20 (q, 2H, J 7.3, CH2CH3), 2.22 (s, 3H, COCH3),
5.91 (d, 1H, J 15.2, H-3), 6.35 (s, 1H, H-6), 6.45 (d, 1H, J 15.2,
H-4), 7.23–7.43 (m, 4H, Ar-H); 13C NMR: δ 18.3, 22.8, 28.7,
29.3, 130.0, 134.7, 135.6, 136.2, 137.8, 138.8, 144.2, 146.7,
191.9; MS (EI) m/z (%): 214 (M+, 42), 171 (51), 91 (100), 43
(70). Anal. Calcd. for C15H18O (214): C, 84.11; H, 8.41. Found:
C, 84.07; H, 8.07%.
Methyl (E,E)-5-ethyl-6-phenylhexa-3,5-dienoate 2c. IR (neat):
1737 cmϪ1; 1H NMR: δ 1.02 (t, 3H, J 7.3, CH3CH2), 2.21 (q, 2H,
J 7.3, CH2CH3), 3.10 (d, 2H, J 7.2, CH2CO), 3.68 (s, 3H,
OCH3), 5.62 (m, 1H, H-3), 5.98 (d, 1H, J 15.2, H-4), 6.23 (s, 1H,
H-6), 7.09–7.38 (m, 4H, Ar-H); 13C NMR: δ 15.8, 29.9, 34.1,
51.7, 126.5, 129.1, 131.2, 134.6, 136.6, 139.6, 144.1, 173.1; MS
(EI) m/z (%): 230 (M+, 67), 171 (100), 77 (71), 59 (72). Anal.
Calcd. for C15H18O2 (230): C, 78.26; H, 7.82. Found: C, 78.31;
H, 7.91%.
Methyl (E,E)-5-ethyl-6-(4-methylphenyl)hexa-3,5-dienoate 2f.
IR (neat): 1735 cmϪ1; 1H NMR: δ 1.05 (t, 3H, J 7.3, CH2CH3),
1.90 (s, 3H, ArCH3), 2.22 (s, 2H, J 7.3, CH2CH3), 2.24 (d, 2H,
J 7.2, CH2CO), 3.70 (s, 3H, OCH3), 5.85 (m, 1H, H-3), 6.28 (d,
1H, J 15.2, H-4), 6.46 (s, 1H, H-6), 7.18–7.48 (m, 4H, Ar-H).
13C NMR: δ 16.7, 21.1, 30.4, 46.3, 51.9, 128.3, 130.3, 134.1,
136.5, 138.1, 144.1, 148.6; MS (EI) m/z (%): 244 (M+, 51), 213
(27), 185 (88), 91 (100), 59 (65). Anal. Calcd. for C16H20O2
(244): C, 78.68; H, 7.82. Found: C, 78.74; H, 7.95%.
6-(4-Methylphenyl)hexa-3,5-dien-2-one 1d. IR (neat): 1677
1
cmϪ1; H NMR: δ 2.05 (s, 3H, Ar-CH3), 2.28 (s, 3H, COCH3),
5.96 (d, 1H, J 15.2, H-3), 6.30 (dd, 1H, J 15.2, 10.1, H-5), 6.36
(d, 1H, J 15.2, H-6), 6.49 (dd, 1H, J 15.2, 10.1, H-4), 7.18–7.51
(m, 4H, Ar-H); 13C NMR: δ 25.4, 33.5, 127.8, 130.8, 134.6,
135.3, 136.9, 137.4, 144.5, 149.3, 194.1; MS (EI) m/z (%): 186
(M+, 55), 123 (45), 91 (100), 43 (70). Anal. Calcd. for C13H14O
(186): C, 83.87; H, 7.52. Found: C, 83.84; H, 7.54%.
5-Methyl-6-(4-chlorophenyl)hexa-3,5-dien-2-one
1g.
IR
1
Methyl (E,E)-6-(4-methylphenyl)hexa-3,5-dienoate 2d. IR
(neat): 1676 cmϪ1; H NMR: δ 1.95 (s, 3H, CH3), 2.28 (s, 3H,
COCH3), 5.95 (d, 1H, J 15.2, H-3), 6.38 (s, 1H, H-6), 6.52 (d,
1H, J 15.2, H-4), 7.25–7.58 (m, 4H, Ar-H); 13C NMR: δ 24.6,
34.0, 129.3, 132.7, 133.7, 135.4, 136.8, 141.3, 144.3, 146.7,
193.4; MS (EI) m/z (%): 220.5 (M+, 48), 177.5 (39), 111.5 (91),
43 (100). Anal. Calcd. for C13H13ClO (220.5): C, 70.74; H, 5.89.
Found: C, 70.85; H, 5.94%.
1
(neat): 1739 cmϪ1; H NMR: δ 2.08 (s, 3H, Ar-CH3), 3.20 (d,
2H, J 7.2, CH2CO), 3.69 (s, 3H, OCH3), 5.88 (m, 1H, H-3), 6.30
(dd, 1H, J 15.2, 10.1, H-5), 6.35 (dd, 1H, J 15.2, 10.1, H-4), 6.45
(d, 1H, J 15.2, H-6), 7.11–7.45 (m, 4H, Ar-H); 13C NMR:
δ 26.8, 44.2, 51.4, 126.4, 129.3, 130.6, 136.4, 136.6, 137.4, 138.2,
147.2, 173.9; MS (EI) m/z (%): 216 (M+, 47), 157 (81), 91 (100),
59 (67). Anal. Calcd. for C14H16O2 (216): C, 77.77; H, 7.40.
Found: C, 77.85; H, 7.50%.
Methyl (E,E)-5-methyl-6-(4-chlorophenyl)hexa-3,5-dienoate
2g. IR (neat): 1739 cmϪ1; 1H NMR: δ 1.93 (s, 3H, CH3), 3.21 (d,
2H, J 7.2, CH2CO), 3.71 (s, 3H, OCH3), 5.94 (m, 1H, H-3), 6.30
(d, 1H, J 15.2, H-4), 6.48 (s, 1H, H-6), 7.18–7.56 (m, 4H, Ar-H);
13C NMR: δ 22.7, 40.2, 52.1, 128.4, 132.1, 134.9, 136.3, 137.0,
Methyl (Z,E)-6-(4-methylphenyl)hexa-3,5-dienoate 2d. IR
1
(neat): 1740 cmϪ1; H NMR: δ 2.05 (s, 3H, Ar-CH3), 3.18 (d,
2H, J 7.2, CH2CO), 3.70 (s, 3H, OCH3), 5.90 (m, 1H, H-3), 6.30
1302
J. Chem. Soc., Perkin Trans. 1, 2001, 1300–1303

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138.5, 146.3; MS (EI) m/z (%): 250.5 (M+, 70), 219.5 (21), 191.5
(100), 111.5 (84), 59 (67). Anal. Calcd. for C14H15O2Cl (250.5):
C, 67.06; H, 5.98. Found: C, 67.11; H, 6.03%.
Calcd. for C16H20O3 (260): C, 73.84; H, 7.69. Found: C, 73.94;
H, 7.81%.
5-Methyl-6-(3,4-dimethoxyphenyl)hexa-3,5-dien-2-one 1k. IR
1
(neat): 1675 cmϪ1; H NMR: δ 1.97 (s, 3H, CH3), 2.26 (s, 3H,
5-Ethyl-6-(4-chlorophenyl)hexa-3,5-dien-2-one 1h. IR (neat):
1675 cmϪ1; 1H NMR: δ 1.06 (t, 3H, J 7.3, CH2CH3), 2.25 (q, 2H,
J 7.3, CH2CH3), 2.27 (s, 3H, COCH3), 5.94 (d, 1H, J 15.2, H-3),
6.33 (s, 1H, H-6), 6.48 (d, 1H, J 15.2, H-4), 7.24–7.55 (m, 4H,
Ar-H); 13C NMR: δ 18.8, 31.4, 33.1, 130.3, 132.6, 133.7, 135.8,
136.4, 138.4, 139.8, 148.3, 193.8; MS (EI) m/z (%): 234.5 (M+,
61), 191.5 (41), 111.5 (81), 43 (100). Anal. Calcd. for C14H15ClO
(234.5): C, 71.64; H, 6.39. Found: C, 71.69; H, 6.48%.
COCH3), 3.74 (s, 3H, ArOCH3), 3.75 (s, 3H, ArOCH3), 5.93 (d,
1H, J 15.2, H-3), 6.38 (s, 1H, H-6), 6.48 (d, 1H, J 15.2, C-4),
7.24–7.53 (m, 3H, Ar-H); 13C NMR: δ 26.3, 33.4, 54.8, 55.4,
131.5, 132.5, 136.4, 138.4, 139.8, 142.7, 149.1, 158.6, 159.4,
194.0; MS (EI) m/z (%): 246 (M+, 41), 203 (45), 137 (72), 43
(100). Anal. Calcd. for C15H18O3 (246): C, 73.17; H, 7.31.
Found: C, 73.24; H, 7.38%.
Methyl (E,E)-5-ethyl-6-(4-chlorophenyl)hexa-3,5-dienoate 2h.
IR (neat): 1738 cmϪ1; 1H NMR: δ 1.08 (t, 3H, J 7.3, CH2CH3),
2.25 (q, 2H, J 7.3, CH2CH3), 3.24 (d, 2H, J 7.2, CH2CO), 3.70
(s, 3H, OCH3), 5.91 (m, 1H, H-3), 6.32 (d, 1H, H-4), 6.48 (s, 1H,
H-6), 7.20–7.54 (m, 4H, Ar-H); 13C NMR: δ 17.0, 31.8, 44.3,
52.0, 130.2, 133.4, 134.0, 134.7, 136.8, 138.7, 139.4, 149.2,
174.3; MS (EI) m/z (%): 248.5 (M+, 55), 217.5 (23), 189.5 (100),
111.5 (79), 59 (61). Anal. Calcd. for C15H17O2Cl (248.5): C,
68.05; H, 6.42. Found: C, 68.13; H, 6.51%.
Methyl
(E,E)-5-methyl-6-(3,4-dimethoxyphenyl)hexa-3,5-
dienoate 2k. IR (neat): 1740 cmϪ1; 1H NMR δ 1.96 (s, 3H, CH3),
3.18 (d, 2H, J 7.2, CH2CO), 3.70 (s, 3H, COOCH3), 3.76 (s, 3H,
ArOCH3), 3.77 (s, 3H, ArOCH3), 5.91 (m, 1H, H-3), 6.30 (d,
1H, J 15.2, H-6), 6.48 (s, 1H, H-4), 7.22–7.58 (m, 3H, Ar-H);
13C NMR: δ 23.7, 34.7, 52.4, 54.3, 55.1, 132.7, 134.3, 136.4,
138.6, 139.7, 142.3, 144.1, 149.0, 158.4, 159.6, 173.8; MS (EI)
m/z (%): 276 (M+, 47), 245 (35), 217 (100), 59 (64). Anal. Calcd.
for C16H20O4 (276): C, 69.56; H, 7.24. Found: C, 69.63; H,
7.36%.
5-Methyl-6-(4-methoxyphenyl)hexa-3,5-dien-2-one 1i. IR
1
(neat): 1675 cmϪ1; H NMR: δ 1.98 (s, 3H, CH3), 2.24 (s, 3H,
5-Ethyl-6-(3,4-dimethoxyphenyl)hexa-3,5-dien-2-one 1l. IR
(neat): 1676 cmϪ1; 1H NMR: δ 1.06 (t, 3H, J 7.3, CH2CH3), 2.20
(q, 2H, J 7.3, CH2CH3), 2.25 (s, 3H, COCH3), 3.75 (s, 3H,
ArOCH3), 3.76 (s, 3H, ArOCH3), 5.91 (d, 1H, J 15.2, H-3), 6.30
(s, 1H, H-6), 6.50 (d, 1H, J 15.2, H-4), 7.23–7.51 (m, 3H, Ar-H);
13C NMR: δ 17.8, 29.4, 32.1, 55.3, 55.9, 133.3, 134.4, 135.8,
136.8, 139.8, 142.3, 143.2, 151.0, 157.8, 159.0, 194.8; MS (EI)
m/z (%): 260 (M+, 41), 217 (20), 137 (72), 43 (100). Anal. Calcd.
for C16H20O3 (260): C, 73.84; H, 7.69. Found: C, 73.90; H,
7.74%.
COCH3), 3.75 (s, 3H, OCH3), 5.92 (d, 1H, J 15.2, H-3), 6.33 (s,
1H, H-6), 6.49 (d, 1H, J 15.2, H-4), 7.23–7.49 (m, 4H, Ar-H);
13C NMR: δ 24.6, 31.5, 55.2, 129.1, 131.4, 133.3, 137.4, 140.0,
146.7, 150.2, 158.3, 192.8; MS (EI) m/z (%): 216 (M+, 48), 173
(32), 107 (100), 43 (92). Anal. Calcd. for C14H16O2 (216): C,
77.77; H, 7.40. Found: C, 77.82; H, 7.47%.
Methyl
(E,E)-5-methyl-6-(4-methoxyphenyl)hexa-3,5-
dienoate 2i. IR (neat): 1739 cmϪ1; 1H NMR: δ 1.95 (s, 3H, CH3),
3.20 (d, 2H, J 7.2, CH2CO), 3.68 (s, 3H, COOCH3), 3.74 (s, 3H,
ArOCH3), 5.90 (m, 1H, H-3), 6.25 (d, 1H, J 15.2, H-4), 6.47 (s,
1H, H-6), 7.15–7.49 (m, 4H, Ar-H); 13C NMR: δ 22.3, 35.9,
51.6, 54.3, 129.7, 132.0, 135.4, 136.4, 138.9, 143.2, 146.5, 159.1,
173.5; MS (EI) m/z (%): 246 (M+, 50), 187 (100), 107 (94), 59
(78). Anal. Calcd. for C15H18O3 (246): C, 73.17; H, 7.31. Found:
C, 73.26; H, 7.45%.
Methyl
(E,E)-5-ethyl-6-(3,4-dimethoxyphenyl)hexa-3,5-
dienoate 2l. IR (neat): 1739 cmϪ1; 1H NMR: δ 1.05 (t, 3H, J 7.3,
CH2CH3), 2.21 (q, 2H, J 7.3, CH2CH3), 3.21 (d, 2H, J 7.2,
CH2CO), 3.70 (s, 3H, COOCH3), 3.75 (s, 3H, ArOCH3), 3.76 (s,
3H, ArOCH3), 5.91 (m, 1H, H-3), 6.31 (d, 1H, J 15.2, H-4), 6.51
(s, 1H, H-6), 7.15–7.54 (m, 3H, Ar-H); 13C NMR: δ 21.6, 29.3,
38.6, 51.8, 54.7, 55.6, 132.6, 136.7, 136.9, 137.4, 139.1, 139.3,
143.5, 147.7, 158.9, 159.4, 174.6; MS (EI) m/z (%): 290 (M+, 31),
259 (31), 231 (100), 137 (72), 59 (61). Anal. Calcd. for C17H22O4
(290): C, 70.34; H, 7.58. Found: C, 70.50; H, 7.69%.
Methyl
(Z,E)-5-methyl-6-(4-methoxyphenyl)hexa-3,5-
dienoate 2i. IR (neat): 1741 cmϪ1; 1H NMR: δ 1.98 (s, 3H, CH3),
3.18 (d, 2H, J 7.2, CH2CO), 3.75 (s, 3H, ArOCH3), 5.95 (m, 1H,
H-3), 6.27 (d, 1H, J 11.5, H-4), 6.48 (s, 1H, H-6), 7.15–7.51 (m,
4H, Ar-H); 13C NMR: δ 23.4, 34.2, 51.9, 54.5, 129.2, 133.2,
134.2, 138.4, 140.2, 144.1, 144.6, 158.4, 173.8; MS (EI) m/z (%):
246 (M+, 46), 215 (17), 187 (100), 107 (94), 59 (78). Anal. Calcd.
for C15H18O2 (246): C, 73.17; H, 7.31. Found: C, 73.22; H,
7.39%.
References
1 R. V. Stevens, R. E. Cherpeck, B. L. Harrison and R. Lapalme,
J. Am. Chem. Soc., 1976, 98, 6317.
2 K. Tossell, Tetrahedron Lett., 1974, 8, 623.
3 G. P. Chiusoli, M. Costa, C. Gallo and G. Salerno, J. Organomet.
Chem., 1986, 317, 373.
4 G. P. Chiusoli, G. Salerno and L. Pallini, J. Organomet. Chem., 1981,
219, C16.
5 G. P. Chiusoli and S. Merzoni, Chem. Abstr., 1964, 61, 14535a.
6 J. L. Herrmann and R. H. Schlessinger, Tetrahedron Lett., 1973,
2433.
7 B. Myrboh, H. Ila and H. Junjappa, Synthesis, 1981, 126.
8 F. Mathew and B. Myrboh, Tetrahedron Lett., 1990, 31, 3757.
9 (a) F. M. Nongrum and B. Myrboh, Synthesis, 1987, 845;
(b) F. Mathew and B. Myrboh, Synth. Commun., 1996, 26, 1097;
(c) F. Mathew and B. Myrboh, Molecules, 1996, 1, 79.
10 G. P. Chiusoli, F. Gigliotti and G. Salerno, J. Organomet. Chem.,
1986, 314, 231.
5-Ethyl-6-(4-methoxyphenyl)hexa-3,5-dien-2-one
1j.
IR
(neat): 1674 cmϪ1; 1H NMR: δ 1.07 (t, 3H, J 7.3, CH2CH3), 2.22
(q, 2H, J 7.3, CH2CH3), 2.25 (s, 3H, COCH3), 3.74 (s, 3H,
ArOCH3), 5.93 (d, 1H, J 15.2, H-3), 6.35 (s, 1H, H-6), 6.45 (d,
1H, J 15.2, H-4), 7.20–7.48 (m, 4H, Ar-H); 13C NMR: δ 18.9,
30.6, 32.0, 54.6, 132.3, 133.6, 135.4, 136.4, 141.7, 142.7, 146.8,
156.7, 192.6; MS (EI) m/z (%): 230 (M+, 61), 187 (34), 107 (100),
43 (76). Anal. Calcd. for C15H18O2 (230): C, 78.26; H, 7.82.
Found: C, 78.31; H, 7.89%.
Methyl (E,E)-5-ethyl-6-(4-methoxyphenyl)hexa-3,5-dienoate
2j. IR (neat): 1738 cmϪ1 1H NMR: δ 1.09 (t, 3H, J 7.3,
;
11 Vogel’s Textbook of Practical Organic Chemistry, ELBS, Longman
Group Ltd.,England, 1978.
CH2CH3), 2.21 (q, 3H, J 7.2, CH2CH3), 3.23 (d, 2H, J 7.3,
CH2CO), 3.69 (s, 3H, COOCH3), 3.75 (s, 3H, ArOCH3), 5.93
(m, 1H, H-3), 6.33 (d, 1H, J 15.2, H-4), 6.46 (s, 1H, H-6), 7.13–
7.50 (m, 4H, Ar-H); 13C NMR: δ 18.0, 28.8, 40.8, 51.6, 55.6,
132.2, 133.3, 136.4, 138.4, 139.6, 143.5, 148.4, 155.3, 173.0; MS
(EI) m/z (%): 260 (M+, 64), 201 (100), 107 (83), 59 (87). Anal.
12 (a) J. Font and P. March, Tetrahedron Lett., 1978, 38, 3601;
(b) H. Zak and U. Schmidt, Chem Ber., 1973, 106, 3652; (c) A. F.
Kluge and C. P. Lillya, J. Org. Chem., 1971, 36, 1977; (d) M. Fujii,
K. Nakamura, S. Yasui and A. Ohno, Bull. Chem. Soc. Jpn., 1987,
60, 2423; (e) Y. Z. Huang, L. Shi and J. Yang, Tetrahedron Lett.,
1987, 28, 2155.
J. Chem. Soc., Perkin Trans. 1, 2001, 1300–1303
1303