A new route to 2-alkenyl-1,3-dicarbonyl compounds, intermediates in the synthesis of dihydrofurans

Article abstract of DOI:10.1016/S0040-4020(01)01173-5

A two step synthetic strategy for obtaining 2-alkenyl-1,3-dicarbonyl compounds from the corresponding 1,3-dicarbonyl compounds is reported. The method is based on a Knoevenagel condensation and a Michael addition using a high order organocuprate procedure, and proves to be of general value. Obtained compounds are useful starting materials for the synthesis of furan derivatives.

Full text of DOI:10.1016/S0040-4020(01)01173-5

TETRAHEDRON
Pergamon
Tetrahedron 58 (2002) 589±596
A new route to 2-alkenyl-1,3-dicarbonyl compounds,
intermediates in the synthesis of dihydrofurans
Roberto Antonioletti,p Paolo Bovicelli and Savina Malancona
Á
Dipartimento di Chimica, Centro CNR di Studio per la Chimica delle Sostanze Organiche Naturali, Universita `La Sapienza', P.le A.Moro,
Box 34, Roma 62, 5-00185 Rome, Italy
Received 22 June 2001; revised 25 October 2001; accepted 22 November 2001
AbstractÐA two step synthetic strategy for obtaining 2-alkenyl-1,3-dicarbonyl compounds from the corresponding 1,3-dicarbonyl
compounds is reported. The method is based on a Knoevenagel condensation and a Michael addition using a high order organocuprate
procedure, and proves to be of general value. Obtained compounds are useful starting materials for the synthesis of furan derivatives. q 2002
Elsevier Science Ltd. All rights reserved.
In recent years we have been studying the iodoenolcyclisa-
tion of 2-alkenyl-1,3-dicarbonyl compounds. Reaction
products are dihydrofuran derivatives, units common in a
wide variety of naturally occurring substances and a simple
method for their synthesis is of particular interest.1
diversely substituted 2-alkenyl-1,3-dicarbonyl compounds
in good to excellent yield. The method is of general value
since we were able to prepare a large number of compounds.
The synthesis was performed in two steps, the ®rst being an
aldol condensation to give a,b-unsaturated-1,3-diketones of
type 3, and the second Michael addition using high-order
organocuprates (Scheme 2).
To render our methodology viable, we needed a general
route to 2-alkenyl-1,3-dicarbonyl compounds, but methods
reported in the literature presented several limitations.
In the ®rst step, method A4 (see Section 1) was used for
aromatic aldehydes, while for volatile and unstable alde-
hydes, more controlled reaction conditions were necessary,
and method B5 was preferred. The highly hindered pivalic
aldehyde did not react under any condition, except method
C,6 a variant of the classic Knoevenagel reaction which
permitted us to obtain the condensation product, although
in low yield.
For example, the allylation of dicarbonyl compounds by
using lithium hydroxide and allyl bromide is not applicable
to secondary allyl bromides,2 since in this case a mixture of
regioisomers which are dif®cult to separate is always
obtained. Another way is the Claisen rearrangement of
allyl±vinyl ethers, but this only works in a few selected
cases (Scheme 1).3
In this work we report the strategy employed to obtain
For the second step we initially performed Grignard
Scheme 1.
Keywords: 2-alkenyl-1,3-dicarbonyl compounds; Knoevenagel condensation; Michael addition.
Corresponding author; e-mail: roberto.antonioletti@uniromal.it
p
0040±4020/02/$ - see front matter q 2002 Elsevier Science Ltd. All rights reserved.
PII: S0040-4020(01)01173-5

590
R.Antonioletti et al./ Tetrahedron 58 (2002) 589±596
Scheme 2.
Scheme 3.
reactions catalysed by Cu(I), but results were not encourag-
ing due to the high reactivity of the substrates giving a
mixture of products derived from 1,4 and 1,2 additions.
Instead, good results were obtained by using the high-
order cuprate vinyl(1-thienyl)Cu(CN)Li2 4.7
other cuprates.8 The commercially available compound did
not give satisfactory results, so we prepared the organo-
cuprate in situ and performed the condensation in a one-
pot procedure, as reported in Scheme 3.
The reported methodology appears to be applicable to
The choice of this reagent is due to its high stability and
capability to perform conjugated additions with respect to
prepare
a
compounds, as reported in Table 1.
wide range of 2-alkenyl-1,3-dicarbonyl
Table 1.
3, 5
X
Y
R
Synthesis of 3
Synthesis of 5
Yield (%)
Method
Time (h)
Yield (%)
Time
5 h
3 h
14 h
3 h
5 h
3 h
1 h
a
b
c
d
e
f
g
h
i
j
k
l
m
n
o
p
q
Me
Ph
Et
Me
Me
Ph
Et
OMe
OEt
OEt
OEt
Me
Ph
Ph
Ph
Ph
Ph
Ph
Ph
A
A
A
A
A
A
A
B
B
B
B
B
B
B
B
A
C
18
2
5
3
3
3
3
48
6
1
5
4
6
5
12
8
12
60
93
95
98
90
93
94
64
70
80
98
90
95
60
68
74
14
45
50
50
64
87
97
75
87
77
63
61
41
53
62
62
53
60
Ph
i-Prop
n-Prop
Me
Et
Me
Me
Me
Me
Me
Me
Me
n-Prop
i-Prop
2-Furyl
t-Butyl
30 min
5 min
30 min
30 min
5 min
5 min
5 min
5 min
5 min
5 min
Et
OMe
OEt
OEt
OEt
OMe
OMe
OMe
OMe
Ph
i-Prop
n-Prop
Me
Me
Me
Me
All yields refer to isolated compounds.

R.Antonioletti et al./ Tetrahedron 58 (2002) 589±596
591
Scheme 4.
Scheme 5.
In a previous paper we reported a synthesis in which
compounds such as 5 were used to prepare tetrasubstituted
furans (Scheme 4).1b
was cooled, diluted with diethyl ether (50 ml) and water
(25 ml). The organic layer was separated, washed with
water (25 ml), HCl 1 M solution (2£25 ml) and sodium
hydrogen carbonate solution until neutrality. The organic
layer was dried (Na2SO4) and the solvent evaporated in
vacuo. The crude product was puri®ed by ¯ash chromato-
graphy (hexane/diethyl ether).
The method was limited to products with R1ˆR2ˆMe or
R1ˆMe, Ph; R2ˆH, since at that time only compounds 3
with such substituents could be prepared by known
methods.
Method B. To a mixture of 1,3-dicarbonyl compound
(10 mmol) in ethanol (10 ml) at 258C, was added piperidine
(catalytic amount) and the aldehyde (10 mmol). The reac-
tion was monitored by GC until the substrate disappeared.
The mixture was diluted with diethyl ether (50 ml) and
water (25 ml). The organic layer was separated and washed
with water (2£25 ml) dried (Na2SO4) and the solvent evapo-
rated in vacuo. The crude product was puri®ed by ¯ash
chromatography (hexane/diethyl ether).
With the method reported in this paper that limitation is now
overcome since compounds 5 with various R1 and R2 groups
can be prepared in a convenient way. Moreover, several
compounds 5 being easily available, it is now also possible
to better study the stereochemistry of the iodocyclisation
reaction (Scheme 5), which is our major interest in this ®eld.
1. Experimental
Method C. To a cold solution (08C) of TiCl4 (10 mmol) in
CCl4 (2.5 ml), under an argon atmosphere, of anhydrous
THF (20 ml) was added under stirring. After a yellow pre-
cipitate was formed, pivalic aldehyde (5 mmol, 0.54 ml) and
methyl acetoacetate (5 mmol, 0.54 ml) were added, then a
solution of pyridine (20 mmol) in anhydrous THF (3 ml)
was added dropwise in 2 h. After 24 h the mixture was
quenched with water (10 ml) and diethyl ether (10 ml).
The water solution was separated and extracted with diethyl
ether (2£10 ml). The organic layer was washed with brine
(2£10 ml), dried (Na2SO4) and the solvent evaporated in
vacuo. The crude product was puri®ed by ¯ash chromato-
graphy (hexane/diethyl ether).
1.1. General methods
1H and 13C NMR spectra were recorded on a Varian XL 300
and Varian Gemini 200 spectrometers in CDCl3 as the
solvent, if not speci®ed. All chemical shifts are reported
in parts per million against internal tetramethylsilane.
Coupling constants J were measured in Hz. All reactions
were monitored by GC. GC analyses were performed on a
HP 5880A chromatograph equipped with a OV 101
capillary column and a ¯ame ionisation detector. GC±MS
analyses were performed on a HP 5890 chromatograph and
HP 5971 as mass detector. IR spectra were recorded in 1%
CHCl3 solution, on a Shimadzu IR 470 apparatus. Silica gel
Merck (200±400 mesh) was used for ¯ash chromatography.
All starting compounds are commercially available from the
Aldrich company.
All compounds were prepared as oils. E and Z geometric
isomers were separated, when possible, by ¯ash chromato-
graphy (hexane/ethyl acetate) for the complete characterisa-
tion, otherwise they were characterised as a mixture.9 In
each case they were used as mixture of isomers for the
further reactions.
1.2. Synthesis of a,b-unsaturated-1,3-dicarbonyl
compounds: general procedures
Method A. In a round ¯ask equipped with a Dean±Stark
apparatus, 1,3-dicarbonyl compound (10 mmol) was
dissolved in benzene (50 ml). The aldehyde (10 mmol),
glacial acetic acid and piperidine (catalytic amounts) were
added. The mixture was re¯uxed until the substrate dis-
appeared. After the required time (Table 1) the mixture
1.2.1. 3-Benzylidene-pentane-2,4-dione (3a). nmax: 1740,
1720, 1680, 1380, 1260, 1240, 700 cm21; 1H NMR d (ppm):
2.26 (3H, s, Me-CO), 2.40 (3H, s, Me-CO), 7.36±7.38 (5H,
m, Ph), 7.47 (1H, s, CHvC); 13C NMR d (ppm): 26.1, 31.3,
129.0, 129.7, 130.6, 132.9, 139.8, 142.8, 196.7, 205.7; m/z
188 (85, M1), 173 (20), 145 (38), 131 (100), 109 (30), 77

592
R.Antonioletti et al./ Tetrahedron 58 (2002) 589±596
(11). Calcd for C12H12O2 C 76.57, H 6.43; found C 76.4, H
6.2.
MeCH2O), 1.52±1.58 (2H, m, CH2CH2Me), 2.50 (2H, t,
Jˆ8 Hz, CH2CO), 4.28 (2H, q, Jˆ6.6 Hz, MeCH2O),
7.30±7.48 (5H, m, Ph), 7.78 (1H, s, CHvC); isomer Z:
0.95 (3H, t, Jˆ7.2 Hz, CH2CH2Me), 1.25 (3H, t,
Jˆ6.8 Hz, MeCH2O), 1.52±1.58 (2H, m, CH2CH2Me),
2.68 (2H, t, Jˆ8 Hz, CH2CO), 4.29 (2H, q, Jˆ6.8 Hz,
MeCH2O), 7.30±7.48 (5H, m, Ph), 7.58 (1H, s, CHvC);
13C NMR d (ppm) isomer E: 13.7, 14.3, 17.0, 45.7, 61.8,
128.8, 129.3, 130.1, 131.1, 134.9, 141.0, 165.3, 206.4;
isomer Z: 13.9, 14.0, 17.6, 40.9, 62.0, 128.8, 129.4, 130.2,
131.1, 134.7, 140.9, 168.6, 197.5; m/z (E) 246 (26, M1),
203 (100), 175 (11), 135 (33), 107 (30), 77 (13); m/z (Z)
246 (37, M1), 203 (100), 175 (16), 135 (40), 107 (38), 77
(7). Calcd for C15H18O3 C 73.15, H 7.37; found C 73.0, H
7.5.
1.2.2. 2-Benzylidene-1,3-diphenyl-propane-1,3-dione (3b).
n
max: 1650, 1600, 1460, 1220, 1240, 1260, 950, 680 cm21; 1H
NMR d (ppm): 7.15±7.67 (12H, m,, Ph), 7.80±8.50 (4H, m,
Ph and CHvC); 13C NMR d (ppm): 128.6, 128.7, 128.8,
129.5, 129.6, 130.2, 130.5, 132.7, 133.1, 134.0, 136.4,
137.5, 139.6, 144.0, 195.2, 197.2; m/z 312 (8, M1), 207
(23), 131 (12), 105 (100), 77 (50). Calcd for C22H16O2 C
84.59, H 5.16; found C 84.4, H 5.1.
1.2.3. 4-Benzylidene-heptane-3,5-dione (3c). nmax: 1710,
1
1610, 1180, 910 cm21; H NMR d (ppm): 1.05 (3H, t,
Jˆ7.2 Hz, Me), 1.13 (3H, t, Jˆ7.2 Hz, Me), 2.47 (2H, q,
Jˆ7.2 Hz, CH2CO), 2.7 (2H, q, Jˆ7.2 Hz, CH2CO), 7.24±
7.39 (5H, m, Ph), 7.52 (1H, s, CHvC); 13C NMR d (ppm):
7.2, 7.7, 31.6, 37.1, 128.9, 129.5, 130.6, 133.3, 138.6, 142.4,
199.2, 208.6; m/z 216 (19, M1), 187 (35), 159 (8), 131
(100), 103 (11), 77 (8), 57 (58). Calcd for C14H16O2 C
77.75, H 7.46; found C 77.9, H 7.7.
1.2.8. 3-Ethylidene-pentane-2,4-dione (3h). nmax: 1702,
1666, 1633, 1433, 1395, 1277, 761 cm21 1H NMR d
;
(ppm): 1.88 (3H, d, Jˆ7.2 Hz, MeCHvC), 2.28 (3H, s,
MeCO), 2.29 (3H, s, MeCO), 6.78 (1H, q, Jˆ7.2 Hz,
CHvC); 13C NMR d (ppm): 15.1, 25.6, 31.2, 142.1,
146.1, 197.2, 203.8; m/z 126 (9, M), 111 (43), 69 (100).
Calcd for C7H10O2 C 66.65, H 7.99; found C 66.6, H 8.0.
1.2.4. 3-Phenyl-2-propionyl-acrylic acid methyl ester
(3d). Two isomers. nmax: 1720, 1620, 1260, 1180,
1
900 cm21; H NMR d (ppm): 2.35 (1.5H, s, MeCO), 2.43
1.2.9. 4-Ethylidene-heptane-3,5-dione (3i). nmax: 2985,
1
(1.5H, s, MeCO), 3.80 (3H, s, MeO), 7.3±7.4 (5H, m, Ph),
7.58 (0.5H, s, CHvC), 7.68 (0.5H, s, CHvC); 13C NMR d
(ppm): 26.7, 31.4, 47.6, 52.8, 127.0, 127.1, 127.9, 128.7,
128.8, 129.5, 133.3, 134.2, 134.8, 134.9, 141.4, 142.2,
165.5, 168.9, 195.4, 204.1; m/z (in mixture) 204 (84, M1),
203 (100), 173 (15), 121 (69), 102 (23). Calcd for C12H12O3
C 70.57, H 5.92; found C 70.3, H 5.9.
1700, 1668, 1663, 1465, 1392, 1214, 1100, 909 cm21; H
NMR d (ppm): 1.06 (3H, t, Jˆ7.3 Hz, MeCH2), 1.07 (3H, t,
Jˆ7.3 Hz, MeCH2), 1.83 (3H, d, Jˆ7.2 Hz, MeCH), 2.55
(2H, q, Jˆ7.3 Hz, CH2CO), 2.62 (2H, q, Jˆ7.3 Hz,
CH2CO), 6.75 (1H, q, Jˆ7.2 Hz, CH2vC); 13C NMR d
(ppm): 7.1, 7.6, 15.1, 30.8, 37.0, 139.8, 145.7, 199.9,
207.3; m/z 154 (16, M), 125 (52), 69 (100), 57 (90). Calcd
for C9H14O2 C 70.10, H 9.15; found C 69.8, H 8.9.
1.2.5. (Z)-2-Benzoyl-3-phenyl-acrylic acid ethyl ester
(3e). nmax: 1720, 1680, 1620, 1460, 1260, 1240, 1220,
1.2.10. 2-Acetyl-but-2-enoic acid methyl ester (3j). Two
1180, 910 cm21
;
1H NMR d (ppm): 1.15 (3H, t,
isomers. nmax: 1723, 1589, 1400, 1322, 1222 cm21 1H
;
Jˆ7.12 Hz, Me), 4.20 (2H, q, Jˆ7.12 Hz, CH2CO), 7.20±
7.95 (8H, m, Ph), 7.90±7.95 (3H, m, CHvC, Ph); 13C NMR
d (ppm): 13.7, 61.4, 128.8, 128.9, 129.2, 130.2, 130.4,
131.4, 132.9, 133.9, 136.2, 142.7, 165.2, 195.9; m/z 280
(73, M1), 206 (19), 176 (15), 105 (100), 77 (58). Calcd
for C18H16O3 C 77.12, H 5.75; found C 77.1, H 5.6.
NMR d (ppm): 1.86 (1.5H, d, Jˆ7.8 Hz) and 1.91 (1.5H,
d, Jˆ7 Hz, MeCH), 2.22 (1.5H, s) and 2.28 (1.5H, s,
MeCO), 3.76 (1.5H, s) and 3.80 (1.5H, s, MeO), 6.93
(0.5H, q, Jˆ7.8 Hz), 6.87 (0.5H, q, Jˆ7 Hz, CHvC); 13C
NMR d (ppm): 15.0, 15.5, 26.4, 26.5, 51.6, 52.0, 137.8,
138.0, 144.3, 144.4, 165.1, 166.9, 195.3, 200.1; m/z
(1st isomer) 142 (24, M1), 127 (28), 110 (100), 95
(44), 82 (44), 69 (56), 59 (41); m/z (2nd isomer) 142
(28, M1), 127 (87), 110 (100), 95 (60), 82 (30), 69 (95),
59 (61). Calcd for C7H10O3 C 59.14, H 7.09; found C 58.9, H
7.2.
1.2.6. 2-Isobutyryl-3-phenyl-acrylic acid ethyl ester (3f).
Two isomers. E/Z ratio 2.2:1.9 nmax: 1720, 1620, 1260, 1115,
1
1100, 680 cm21; H NMR d (ppm) isomer E: 1.04 (6H, d,
Jˆ6.9 Hz, Me-CH), 1.29 (3H, t, Jˆ7.1 Hz, Me-CH2O), 2.65
(1H, ept, Jˆ6.9 Hz, CHMe2), 4.28 (2H, q, Jˆ7.1 Hz,
CH2O), 7.30±7.48 (5H, m, Ph), 7.76 (1H, s, CHvC);
isomer Z: 1.15 (6H, d, Jˆ6.8 Hz, Me-CH), 1.26 (3H, t,
Jˆ7.1 Hz, Me-CH2O), 3.18 (1H, ept, Jˆ6.8 Hz, CHMe2),
4.25 (2H, q, Jˆ7.1 Hz, CH2O), 7.30±7.48 (5H, m, Ph), 7.58
(1H, s, CHvC); 13C NMR n (ppm) isomer E: 13.9, 17.7,
41.6, 61.4, 128.9, 129.6, 129.8, 130.6, 133.5, 141.4, 165.4,
200.7; isomer Z: 13.6, 18.8, 36.0, 61.6, 128.9, 129.8, 129.9,
130.4, 133.7, 140.9, 165.6, 200.4; m/z (in mixture) 246 (13,
M1), 203 (100), 175 (15), 135 (31), 107 (15), 77 (8). Calcd
for C15H18O3 C 73.15, H 7.37; found C 73.1, H 7.5.
1.2.11. 2-Benzoyl-but-2-enoic acid ethyl ester (3k). Two
isomers. Ratio 3.2:1. nmax: 1716, 1674, 1601, 1455, 1370,
1
1270 cm21; H NMR d (ppm) major isomer: 1.08 (3H, t,
Jˆ7.1 Hz, MeCH2O), 1.85 (3H, d, Jˆ7.2 Hz, MeCHvC),
4.12 (2H, q, Jˆ7.1 Hz, MeCH2O), 7.21 (1H, q, Jˆ7.2 Hz,
CHvC), 7.3±7.6 (3H, m, Ph), 7.7±8.1 (2H, m, Ph); minor
isomer: 1.1 (3H, t, Jˆ7.1 Hz, MeCH2O), 2.12 (3H, d,
Jˆ7.3 Hz, MeCHvC), 4.12 (2H, q, Jˆ7.1 Hz, MeCH2O),
6.76 (1H, q, Jˆ7.3 Hz, CHvC), 7.3±7.6 (3H, m, Ph), 7.7±
8.1 (2H, m, Ph); 13C NMR d (ppm): 10.1, 13.5, 13.6, 15.1,
60.7, 60.9, 128.5, 128.6, 128.8, 128.9, 129.0, 132.8, 133.8,
134.8, 136.8, 143.5, 146.9, 164.6, 165.1, 194.7, 198.2; m/z
(in mixture) 218 (3, M1), 172 (7), 144 (20), 105 (100), 77
(34), 51 (6). Calcd for C13H14O3 C 71.54, H 6.47; found C
71.6, H 6.4.
1.2.7. 2-Butyryl-3-phenyl-acrylic acid ethyl ester (3g).
Two isomers. E/Z ratio 2.4:1.9 nmax: 2980, 1705, 1600,
1
1480, 1380, 1220 cm21; H NMR d (ppm) isomer E: 0.87
(3H, t, Jˆ7.1 Hz, CH2CH2Me), 1.29 (3H, t, Jˆ6.6 Hz,

R.Antonioletti et al./ Tetrahedron 58 (2002) 589±596
593
1.2.12. 2-Isobutyryl-but-2-enoic acid ethyl ester (3l). Two
isomers. nmax: 2985, 1710, 1708, 1699, 1261, 1195,
123 (56), 120 (32), 96 (60), 95 (48), 81 (30), 67 (34), 55
(20), 53 (33); (isomer Z) 170 (0.4, M1), 139 (34), 138 (100),
123 (62), 120 (27), 96 (50), 95 (42), 81 (33), 67 (34), 55
(36), 53 (23). Calcd for C9H14O3 C 63.51, H 8.29; found C
63.3, H 8.4.
1
754 cm21; H NMR d (ppm): 1.07 (3H, d, Jˆ6.9 Hz) and
1.1 (3H, d, Jˆ7.0 Hz, Me2CH), 1.26 (1.5H, t, Jˆ7.1 Hz) and
1.30 (1.5H, t, Jˆ7.1 Hz, MeCH2O), 1.81 (1.5H, d,
Jˆ7.3 Hz) and 1.96 (1.5H, d, Jˆ7.2 Hz, MeCHvC), 2.92
(0.5H, ept, Jˆ6.9 Hz) and 3.05 (0.5H, ept, Jˆ7.0 Hz,
CHMe2), 4.18 (1H, q, Jˆ7.1 Hz) and 4.25 (1H, q,
Jˆ7.1 Hz, MeCH2O), 6.88 (0.5H, q, Jˆ7.2 Hz) and 7.01
(0.5H, q, Jˆ7.3 Hz, CHvC); 13C NMR d (ppm): 13.8,
15.1, 15.4, 17.5, 17.6, 18.4, 36.3, 40.4, 41.0, 46.9, 60.9,
61.0, 136.3, 137.2, 143.0, 143.4, 164.6, 167.2, 202.2,
208.0. m/z (in mixture) 184 (8, M1), 141 (100), 138 (12),
113 (69), 95 (24), 71 (10), 69 (18). Calcd for C10H16O3 C
65.19, H 8.75; found C 65.0, H 8.4.
1.2.16. 2-Acetyl-3-furan-2-yl-acrylic acid methyl ester
(3p). Two isomers in 3:7 ratio. nmax: 1717, 1628, 1250,
1241, 1186, 1171, 910 cm21 1H NMR d (ppm): 2.32
;
(2.1H, s) and 2.48 (0.9H, s, Me), 3.78 (0.9H, s) and 3.90
(2.1H, s, MeO), 6.42 (0.3H, dd, Jˆ1.8, 3.3 Hz) and 6.51
(0.7H, dd, Jˆ1.8, 3.3 Hz, C4-H furyl), 6.65 (0.3H, d,
Jˆ3.3 Hz) and 6.86 (0.7H, d, Jˆ3.3 Hz, C3-H furyl), 7.27
(0.7H, s) and 7.35 (0.3H, s, CHvC), 7.50 (0.3H, d,
Jˆ1.8 Hz) and 7.56 (0.7H, d, Jˆ1.8 Hz, C5-H furyl); 13C
NMR d (ppm): 26.3, 31.2, 52.4 (2C), 112.7, 113.0, 118.0,
119.1, 126.2, 126.9, 129.3, 129.8, 146.5, 146.8, 149.0,
150.2, 164.0, 168.3, 194.3, 201.0; m/z (major isomer) 194
(49, M1), 179 (24), 163 (20), 162 (15), 152 (11), 134 (12),
121 (61), 120 (100), 111 (71), 92 (13), 77 (15), 65 (14), 64
(11), 63 (21), 59 (13); (minor isomer) 194 (70, M1), 179
(32), 163 (20), 162 (16), 152 (12), 134 (12), 121 (55), 120
(100), 111 (68), 92 (12), 77 (14), 65 (11), 64 (9), 63 (16), 59
(8). Calcd for C10H10O4 C 61.85, H 5.19; found C 61.8, H
5.0.
1.2.13. 2-Butyryl-but-2-enoic acid ethyl ester (3m). Two
isomers. nmax: 2980, 1714, 1392, 1265, 1243, 1106,
1
749 cm21; H NMR d (ppm): 0.92 (1.5H, t, Jˆ7.2 Hz)
and 0.96 (1.5H, t, Jˆ7.2 Hz, MeCH2O), 1.23 (1.5H, t,
Jˆ7.1 Hz) and 1.31 (1.5H, t, Jˆ7.1 Hz, MeCH2CH2), 1.5±
1.7 (2H, m, MeCH2CH2), 1.83 (1.5H, d, Jˆ7.4 Hz) and 1.93
(1.5H, d, Jˆ7.2 Hz, MeCHvC), 2.5±2.7 (2H, m,
MeCH2CH2), 4.20 (1H, q, Jˆ7.2 Hz) and 4.28 (1H, q,
Jˆ7.0 Hz, MeCH2O), 6.90 (0.5H, q, Jˆ7.2 Hz) and 6.96
(0.5H, q, Jˆ7.4 Hz, CHvC); 13C NMR d (ppm): 13.2,
13.3, 13.7, 13.9, 16.7, 17.1, 40.7, 44.6, 45.1, 49.0, 60.8,
60.9, 136.8, 138.0, 142.7, 143.2, 164.8, 166.7, 197.7,
204.1; m/z (1st isomer) 184 (6, M1), 169 (19), 141 (100),
139 (18), 138 (14), 113 (69), 95 (19), 82 (8), 71 (14), 69
(15); (2nd isomer) 184 (1, M1), 169 (24), 141 (100), 139
(21), 138 (6), 113 (84), 95 (27), 82 (7), 71 (22), 69 (28).
Calcd for C10H16O3 C 65.19, H 8.75; found C 64.9, H 8.5.
1.2.17. (Z)-2-Acetyl-4,4-dimethyl-pent-2-enoic acid
methyl ester (3q). nmax: 2009, 1720, 1646, 1363, 1212,
1
830 cm21; H NMR d (ppm): 1.11 (9H, s, Me3C), 2.25
(3H, s, MeCO), 3.72 (3H, s, MeO), 6.66 (1H, s, CHvC);
13C NMR d (ppm): 25.6, 28.6 (3C), 33.9, 51.9, 134.1, 154.5,
168.4, 195.8; m/z 169 (100), 153 (34), 152 (62), 137 (65),
135 (15), 134 (18), 124 (17), 111 (18), 110 (31), 109 (65), 95
(36), 81 (55), 69 (33), 67 (25). Calcd for C10H16O3 C 65.19,
H 8.75; found C 65.3, H 8.6.
1.2.14. 2-Acetyl-hex-2-enoic acid methyl ester (3n). Two
isomers. nmax: 2965, 1718, 1663, 1261, 1241, 730 cm21; 1H
NMR d (ppm): 0.8 (1.5H, t, Jˆ7.1 Hz) and 1.0 (1.5H, t,
Jˆ7.1 Hz, MeCH2CH2), 1.4±1.6 (2H, m, MeCH2CH2),
2.1±2.3 (2H, m, CH2CHvC), 2.29 (1.5H, s) and 2.34
(1.5H, s, MeCO), 3.76 (1.5H, s) and 3.80 (1.5H, s, MeO),
6.83 (0.5H, t, Jˆ7.7 Hz) and 6.91 (0.5H, t, Jˆ7.9 Hz,
CHvC); 13C NMR d (ppm): 12.7, 13.4, 21.3, 21.5, 25.2,
26.4, 30.8, 30.9, 51.6, 51.8, 137.1, 139.0, 148.8, 149.0,
165.0, 167.0, 195.3, 201.7; m/z (1st isomer) 170 (4, M1),
139 (31), 138 (100), 123 (61), 113 (77), 110 (21), 97 (24), 96
(91), 95 (70), 81 (38), 69 (13), 68 (19), 67 (25), 59 (23), 57
(17), 55 (25), 53 (15); (2nd isomer) 170 (2, M1), 139 (32),
138 (73), 123 (52), 113 (100), 110 (16), 100 (12), 97 (34), 96
(72), 95 (49), 81 (30), 69 (17), 68 (25), 67 (27), 59 (28), 57
(16), 55 (43), 53 (22). Calcd for C9H14O3 C 63.51, H 8.29;
found C 63.4, H 8.3.
1.3. Synthesis of b-alkyl-g,d-unsaturated-1,3-dicarbonyl
compounds: general procedure
In a rigorously dried Claisen ¯ask, a solution of thiophene
(1.1 mmol) in anhydrous THF (0.5 ml) was injected. The
solution was cooled to 2788C and n-butyllithium
(1.1 mmol) was added via cannula. After 5 min the mixture
was warmed to 08C and stirred for an additional 30 min. The
mixture was added, via cannula, to a cold (2788C) solution
of CuCN (1.1 mmol) in freshly dried diethyl ether (1 ml).
The mixture was warmed to 08C to favour the formation of
(2-thienyl)Cu(CN)Li, then cooled to 2788C. Vinylmagne-
sium bromide (1.1 mmol) was added and the mixture was
warmed again to 08C. Finally, a solution of the a,b-unsatu-
rated 1,3-dicarbonyl compound (1 mmol) in anhydrous THF
(1 ml) was added at 2788C via cannula. The reaction was
monitored by GC. When the substrate was completely
consumed, the reaction was quenched with an aqueous
10% concentrated NH4OH±90% saturated NH4Cl solution
(20 ml). The mixture was diluted with diethyl ether (25 ml)
and the organic layer separated. The aqueous layer was
extracted with diethyl ether (3£20 ml). Combined extracts
were washed with brine (10 ml), dried (Na2SO4) and the
solvent evaporated in vacuo. The crude product was puri®ed
by ¯ash chromatography (hexane/diethyl ether). All
compounds were prepared as oils.
1.2.15. 2-Acetyl-4-methyl-pent-2-enoic acid methyl ester
(3o). Two isomers. E/Z ratio 1:2. nmax: 2970, 1723, 1638,
1263, 1250, 767 cm21; 1H NMR d (ppm) isomer E: 1.0 (6H,
d, Jˆ8.0 Hz, Me2CH), 2.33 (3H, s, MeCO), 2.61 (1H, m,
CHMe2), 3.75 (3H, s, MeO), 6.68 (1H, d, Jˆ10.7 Hz,
CHvC); isomer Z: 1.05 (6H, d, Jˆ6.7 Hz, Me2CH), 2.28
(3H, s, MeCO), 2.65 (1H, m, CHMe2), 3.80 (3H, s, MeO),
6.58 (1H, d, Jˆ10.6 Hz, CHvC); 13C NMR d (ppm) isomer
E: 21.7 (2C), 28.5, 31.0, 51.9, 133.3, 154.7, 165.2, 201.3;
isomer Z: 21.6 (2C), 26.4, 29.4, 51.9, 134.8, 154.4, 167.2,
195.6; m/z (isomer E) 170 (0.5, M1), 139 (26), 138 (100),

594
R.Antonioletti et al./ Tetrahedron 58 (2002) 589±596
1.3.1. 3-(1-Phenyl-allyl)-pentane-2,4-dione (5a). nmax
;
:
235 (35), 203 (15), 157 (13), 105 (100), 91 (8), 77
(33). Calcd for C20H20O3 C 77.90, H 6.54; found C 77.7,
H 6.4.
2987, 1707, 1590, 1370, 1189, 900 cm21 1H NMR n
(ppm): 1.86 (3H, s, MeCO), 2.22 (3H, s, MeCO), 4.13
(1H, dd, Jˆ7.7, 11.7 Hz, CHCHvCH2), 4.25 (1H, d,
Jˆ11.7 Hz, COCHCO), 5.0±5.1 (2H, m, CHvCH2), 5.84
(1H, ddd, Jˆ10.9, 11.7, 17.0 Hz, CHvCH2), 7.1±7.3 (5H,
m, Ph); 13C NMR d (ppm): 22.7, 22.8, 31.3, 74.5, 116.3,
126.7, 128.9, 129.5, 140.1, 142.3, 208.3, 210.6; m/z 216 (19,
M1), 188 (61), 187 (35), 173 (16), 131 (100), 103 (33), 77
(15). Calcd for C14H16O2 C 77.75, H 7.46; found C 77.5, H
7.3.
1.3.6. 2-Isobutyryl-3-phenyl-pent-4-enoic acid ethyl ester
(5f). Two isomers. nmax: 3005, 1720, 1706, 1310, 1270,
1
1350 cm21; H NMR d (ppm): 0.60 (1.5H, d, Jˆ8 Hz)
and 0.90 (1.5H, d, Jˆ8 Hz, MeCH), 0.93 (1.5H, t,
Jˆ6.7 Hz) and 1.22 (1.5H, t, Jˆ6.7 Hz, MeCH2), 1.08
(1.5H, d, Jˆ8 Hz) and 1.10 (1.5H, d, Jˆ8 Hz, MeCH),
2.30 (0.5H, ept, Jˆ8 Hz) and 2.75 (0.5H, ept, Jˆ8 Hz,
Me2CH), 3.75 (1H, q, Jˆ8 Hz) and 4.15 (1H, q, Jˆ8 Hz,
CH2O), 4.15±4.25 (2H, m, COCHCO and CHCHvCH2),
4.9±5.2 (2H, m, CHvCH2), 5.8±6.1 (1H, m, CHvCH2),
7.1±7.3 (5H, m, Ph); 13C NMR d (ppm): 13.5, 13.9, 16.9,
17.3, 17.5, 17.6, 41.9, 42.0, 49.4 (2C), 61.1, 61.3, 62.3, 62.5,
116.2, 116.8, 127.0, 127.1, 128.2 (2C), 128.4 (2C), 128.6
(2C), 128.7 (2C), 138.2, 138.3, 140.3, 140.4, 167.6, 167.9,
207.3, 207.4; m/z 274 (3, M1), 256 (7), 203 (29), 175 (12),
157 (24), 117 (100), 115 (29), 91 (35). Calcd for C17H22O3 C
74.42, H 8.08; found C 74.4, H 8.2.
1.3.2. 1,3-Diphenyl-2-(1-phenyl-allyl)-propane-1,3-dione
1
(5b). nmax: 1698, 1665, 1290, 1272, 729, 490 cm21; H
NMR
d
(ppm): 4.63 (1H, dd, Jˆ7.9, 10.2 Hz,
CHCHvCH2), 4.98 (1H, dd, Jˆ1.5, 18 Hz) and 5.01 (1H,
dd, Jˆ1.5, 10.2 Hz, CHvCH2), 5.87 (1H, d, Jˆ10.2 Hz,
COCHCO), 6.00 (1H, ddd, Jˆ7.9, 10.2, 18 Hz,
CHvCH2), 7±8 (15H, m, Ph); 13C NMR d (ppm): 50.7,
62.0, 116.9, 126.9, 128.5, 128.6, 128.7 (2C), 128.9, 129.0,
133.4, 133.7, 136.9, 137.2, 138.3, 140.7, 194.5, 194.6; m/z
235 (48), 152 (11), 105 (100), 91 (11), 77 (46). Calcd for
C24H20O2 C 84.68, H 5.92; found C 84.5, H 5.7.
1.3.7. 2-Butyryl-3-phenyl-pent-4-enoic acid ethyl ester
1
(5g). Two isomers. nmax: 1720, 1700, 1130, 680 cm21; H
1.3.3. 4-(1-Phenyl-allyl)-heptane-3,5-dione (5c). nmax
;
:
NMR d (ppm): 0.61 (1.5H, t, Jˆ7.3 Hz) and 0.87 (1.5H, t,
Jˆ7.3 Hz, MeCH2CH2), 0.92 (1.5H, t, Jˆ7.2 Hz) and 1.19
(1.5H, t, Jˆ7.2 Hz, MeCH2O), 1.2 (1H, m) and 1.58 (1H, m,
MeCH2CH2), 2±2.5 (2H, m, CH2CO), 3.82 (1H, q,
Jˆ7.5 Hz) and 4.20 (1H, q, Jˆ7.5 Hz, CH2O), 3.9±4.2
(2H, m, COCHCO, CHCHvCH2), 4.9±5.1 (2H, m,
CHvCH2), 5.8±6.1 (1H, m, CHvCH2), 7.1±7.4 (5H, m,
Ph); 13C NMR d (ppm): 13.3, 13.6, 13.7, 13.9, 16.6, 16.9,
45.2, 45.5, 49.5, 49.6, 61.5, 61.8, 64.5, 64.7, 116.6, 117.0,
127.4, 127.5, 128.5 (2C), 128.6 (2C), 129.0 (2C), 129.2
(2C), 138.6, 138.8, 140.6, 140.8, 168.1, 168.5, 204.2,
204.3; m/z (in mixture) 274 (2, M1), 256 (19), 203
(44), 175 (25), 157 (42), 117 (100), 115 (35), 91 (36), 71
(50). Calcd for C17H22O3 C 74.42, H 8.08; found C 74.6, H
8.2.
3010, 1710, 1480, 1370, 1120, 910 cm21 1H NMR d
(ppm): 0.69 (3H, t, Jˆ7.3 Hz, Me), 0.99 (3H, t, Jˆ7.2 Hz,
Me), 2.05 (1H, dq, Jˆ7.2, 18 Hz) and 2.23 (1H, dq, Jˆ7.2,
18 Hz, CH2CH3), 2.56 (2H, q, Jˆ7 Hz, CH2CH3), 4.19 (1H,
d, Jˆ8.7 Hz, COCHCO), 4.21 (1H, dd, Jˆ6.0, 8.7 Hz,
CHCHvCH2), 5.00 (1H, dd, Jˆ1.4, 11.2 Hz) and 5.02
(1H, dd, Jˆ1.4, 17 Hz, CHvCH2), 5.7±5.9 (1H, m,
CHvCH2), 7.1±7.3 (5H, m, Ph); 13C NMR d (ppm): 6.9,
7.1, 35.4, 36.1, 49.7, 72.8, 116.4, 127.1, 128, 128.9, 138.3,
140.2, 205.5 (2C); m/z 244 (2, M1), 187 (88), 159 (15), 117
(71), 91 (21), 77 (11), 57 (100). Calcd for C16H20O2 C 78.65,
H 8.25; found C 78.6, H 8.2.
1.3.4. 2-Acetyl-3-phenyl-pent-4-enoic acid methyl ester
(5d). Two isomers. nmax: 1724, 1710, 1522, 1130,
980 cm21
;
1H NMR d (ppm) 1.95 (1.5H, s) and 2.27
1.3.8. 3-(1-Methyl-allyl)-pentane-2,4-dione (5h). 1H NMR
d (ppm): 1.01 (3H, d, Jˆ6.7 Hz, MeCH), 2.14 (3H, s,
MeCO), 2.22 (3H, s, MeCO), 3.0±3.2 (1H, m,
CHCHvCH2), 3.62 (1H, d, Jˆ10.5 Hz, COCHCO), 5.04
(1H, dd, Jˆ1.5, 10.2 Hz) and 5.07 (1H, dd, Jˆ1.5, 17 Hz,
CHvCH2), 5.66 (ddd, 1H, Jˆ8, 10.2, 17.0 Hz, CHvCH2);
13C NMR d (ppm): 18.0, 29.3, 29.6, 38.2, 75.3, 115.7, 139.8,
203.8, 203.9. IR (cm21): 1716, 1695, 1368, 1167, 1145, 757;
m/z 154 (2, M1), 110 (12), 111 (25), 97 (15), 43 (100). Calcd
for C9H14O2 C 70.0, H 9.15; found C 70.2, H 9.3.
(1.5H, s, MeCO), 3.45 (1.5H, s) and 3.71 (1.5H, s, MeO),
3.9±4.2 (2H, m, COCHCO and CHCHvCH2), 5.0±5.2 (2H,
m, CHvCH2), 5.8±6.1 (1H, m, CHvCH2), 7.1±7.3 (5H, m,
Ph); 13C NMR d (ppm): 29.6, 29.9, 49.2, 49.3, 51.2, 51.4,
64.6, 65.0, 116.3, 116.8, 127.1, 127.2, 127.9, 128.0, 128.7,
128.9, 137.9, 138.2, 139.8, 140.0, 168.5, 168.9, 201.8,
202.0; m/z (in mixture) 232 (3, M1), 217 (46), 189
(54), 157 (46), 129 (49), 117 (100), 116 (54), 91 (38), 77
(13). Calcd for C14H16O3 C 72.39, H 6.94; found C 72.1, H
6.7.
1.3.9. 4-(1-Methyl-allyl)-heptane-3,5-dione (5i). nmax
;
:
1.3.5. 2-Benzoyl-3-phenyl-pent-4-enoic acid ethyl ester
(5e). Two isomers. nmax: 1719, 1680, 1220, 1210,
1705, 1645, 1236, 1027, 1001, 701 cm21 1H NMR d
(ppm): 0.92 (3H, d, Jˆ7.0 Hz, MeCH), 0.94 (3H, t,
Jˆ7.2 Hz, MeCH2), 1.00 (3H, t, Jˆ7.2 Hz, MeCH2), 2.3±
2.6 (4H, m, MeCH2), 2.9±3.1 (1H, m, CHCHvCH2), 3.60
(1H, d, Jˆ10.6 Hz, COCHCO), 4.95 (1H, dd, Jˆ2, 13.2 Hz)
and 5.02 (1H, dd, Jˆ2, 17.1 Hz, CHvCH2), 5.59 (1H, ddd,
Jˆ7.9, 13.2, 17.1 Hz, CHvCH2); 13C NMR d (ppm): 7.5,
8.2, 15.4, 37.2, 37.6, 38.3, 74.3, 116.8, 140.1, 203.5, 203.9;
m/z 182 (1, M1), 126 (14), 125 (21), 111 (18), 97 (22), 57
(100). Calcd for C11H18O2 C 72.49, H 9.95; found C 72.4, H
9.8.
1
800 cm21; H NMR d (ppm): 0.87 (1.5H, t, Jˆ7.0 Hz)
and 1.19 (1.5H, t, Jˆ6.9 Hz, OCH2CH3), 3.83 (1H, q,
Jˆ7.0 Hz) and 4.12 (1H, q, Jˆ6.9 Hz, OCH2CH3), 4.3±
4.5 (1H, m, CHCHvCH2), 4.8±5.2 (3H, m, COCHCO
and CHvCH2), 5.8±6.2 (1H, m, CHvCH2), 7.2±8.1
(10H, m; Ph); 13C NMR d (ppm): 13.4, 13.8, 49.1, 49.4,
59.0, 59.3, 61.2, 61.5, 116.4, 116.5, 126.8, 127.1, 128.0,
128.3, 128.5 (8C), 128.6 (4C), 128.8 (4C), 133.5, 133.7,
136.8, 136.9, 140.2, 140.7, 167.7, 167.9, 193.0, 193.2; m/z

R.Antonioletti et al./ Tetrahedron 58 (2002) 589±596
595
1.3.10. 2-Acetyl-3-methyl-pent-4-enoic acid methyl
ester (5j). Two isomers. nmax: 2965, 1737, 1710, 1367,
1.3.14. 2-Acetyl-3-propyl-pent-4-enoic acid methyl ester
(5n). Two isomers. nmax: 3140, 1780, 1740, 1478, 1412,
1290, 1224, 1144, 910 cm21
;
1H NMR d (ppm): 0.99
1156 cm21 1H NMR d (ppm): 0.75±0.95 (3H, m,
;
(1.5H, d, Jˆ7.0 Hz) and 1.03 (1.5H, d, Jˆ6.9 Hz, MeCH),
2.16 (1.5H, s) and 2.20 (1.5H, s, MeCO), 2.9±3.0 (1H,
m, CHCHvCH2), 3.35 (1H, d, Jˆ9.6 Hz, COCHCO),
3.66 (1.5H, s) and 3.69 (1.5H, s, MeO), 4.9±5.1 (2H,
m, CHvCH2), 5.5±5.8 (1H, m, CHvCH2); 13C NMR d
(ppm): 17.7, 17.9, 29.2, 29.3, 37.6, 37.8, 51.9, 52.1,
65.5, 65.6, 115.4, 115.6, 139.7, 139.8, 169.2, 169.3,
202.6, 202.7; m/z (in mixture) 170 (1, M1), 142 (29), 141
(11), 127 (23), 97 (10), 96 (11), 95 (15), 71 (100), 55
(13). Calcd for C9H14O3 C 63.51, H 8.29; found C 63.5, H
8.1.
MeCH2CH2), 1.2±1.4 (4H, m, MeCH2CH2), 2.15 (1.5H, s)
and 2.20 (1.5H, s, MeCO), 2.7±2.9 (1H, m, CHCHvCH2),
3.41 (0.5H, d, Jˆ10 Hz) and 3.43 (0.5H, d, Jˆ9.8 Hz,
COCHCO), 3.64 (1.5H, s) and 3.70 (1.5H, s, MeCO),
5.0±5.1 (2H, m, CHvCH2), 5.4±5.7 (1H, m, CHvCH2);
13C NMR d (ppm): 13.5 (2C), 19.7, 19.9, 29.3 (2C), 34.3,
34.4, 43.7, 43.8, 52.0, 52.2, 65.0, 65.1, 117.4, 117.7, 138.1,
138.2, 169.2, 169.4, 202.8 (2C); m/z 198 (2, M1), 156 (12),
113 (25), 43 (100). Calcd for C11H18O3 C 66.64, H 9.15;
found C 66.5, H 9.0.
1.3.15. 2-Acetyl-3-isopropyl-pent-4-enoic acid methyl
ester (5o). Two isomers. nmax: 3097, 1762, 1731, 1408,
1.3.11. 2-Benzoyl-3-methyl-pent-4-enoic acid ethyl
ester (5k). Two isomers. nmax: 1720, 1685, 1293, 1289,
1345, 1109 cm21
;
1H NMR d (ppm): 0.79 (3H, d,
1177, 910 cm21
;
1H NMR d (ppm): 1.02 (1.5H, d,
Jˆ6.6 Hz, MeCH), 0.86 (3H, d, Jˆ6.6 Hz, MeCH), 1.5±
1.8 (1H, m, Me2CH), 2.14 (1.5H, s) and 2.20 (1.5H, s,
MeCO), 2.5±2.8 (1H, m, CHCHvCH2), 3.64 (1.5H, s)
and 3.70 (1.5H, s, MeO), 3.6±3.7 (1H, m, COCHCO),
5.0±5.2 (2H, m, CHvCH2), 4.9±5.3 (1H, m, CHvCH2);
13C NMR d (ppm): 16.3 (2C), 17.1 (2C), 21.0, 21.1, 28.5,
28.8, 49.7, 50.0, 51.9, 52.2, 62.8, 63.0, 118.6, 119.1, 134.2,
134.7, 169.3, 169.5, 202.8, 202.9; m/z 198 (1, M1), 156 (10),
113 (37), 43 (100). Calcd for C11H18O3 C 66.64, H 9.15;
found C 66.8, H 9.3.
Jˆ6.9 Hz) and 1.09 (1.5H, d, Jˆ7 Hz, MeCH), 1.12
(1.5H, t, Jˆ7.5 Hz) and 1.16 (1.5H, t, Jˆ7.7 Hz, MeCH2),
3.1±3.3 (1H, m, CHCHvCH2), 4.0±4.3 (3H, m, COCHCO
and MeCH2O), 4.8±5.1 (2H, m, CHvCH2), 5.6±5.9
(1H, m, CHvCH2), 7.4±7.6 (3H, m) and 7.9±8.1 (2H, m,
Ph); 13C NMR d (ppm): 13.7, 13.8, 17.4, 18.2, 37.5, 38.0,
59.5, 60.0, 61.1, 61.2, 115.3, 115.4, 128.5 (2C), 128.6 (2C),
128.7 (2C), 128.8 (2C), 133.5, 133.6, 136.7, 136.9, 140.1,
140.3, 168.6, 168.8, 194.0, 194.2; m/z (in mixture) 246
(2, M1), 192 (7), 173 (8), 141 (5), 113 (5), 105 (100), 77
(45). Calcd for C15H18O3 C 73.15, H 7.37; found C 73.3, H
7.2.
1.3.16. 2-Acetyl-3-furan-2-yl-pent-4-enoic acid methyl
ester (5p). Two isomers. nmax: 1741, 1726, 1523, 1480,
1
1230 cm21; H NMR d (ppm): 2.09 (1.5H, s) and 2.22
(1.5H, s, MeCO), 3.60 (1.5H, s) and 3.69 (1.5H, s, MeO),
4.01 (0.5H, d, Jˆ9.5 Hz) and 4.03 (0.5H, d, Jˆ9 Hz,
COCHCO), 4.1±4.3 (1H, m, CHCHvCH2), 5.05±5.10
(2H, m, CHvCH2), 5.7±6.0 (1H, m, CHvCH2), 6.06
(1H, bs, 3-H furan), 6.25 (1H, dd, Jˆ1.9, 3.3 Hz, 2-H
furan), 7.28 (bs, 1H, 5-H furan); 13C NMR d (ppm): 29.3,
29.9, 42.6, 42.7, 52.3 (2C), 62.6, 62.7, 106.4, 106.9, 110.3,
110.5, 117.8, 118.3, 134.8, 135.1, 141.9 (2C), 152.9, 153.4,
168.2, 168.3, 201.3, 201.5; m/z 222 (1, M1), 204 (25), 179
(100), 163 (54), 148 (30), 147 (77), 121 (21), 120 (19), 119
(15), 107 (83), 91 (28), 79 (34), 77 (36). Calcd for C12H14O4
C 64.85, H 6.35; found C 64.6, H 6.3.
1.3.12. 2-Isobutyryl-3-methyl-pent-4-enoic acid ethyl
ester (5l). Two isomers. nmax: 3175, 1775, 1747, 1348,
1
1245, 1199, 1042 cm21; H NMR d (ppm): 0.8±1.3 (12H,
m, Me2CH, MeCH2O and MeCH), 2.5±2.8 (1H, m, Me2CH),
2.8±3.0 (1H, m, CHCHvCH2), 3.49 (0.5H, d, Jˆ6.9 Hz)
and 3.51 (0.5H, d, Jˆ7.0 Hz, COCHCO), 4.0±4.2 (2H, m,
CH2O), 4.9±5.1 (2H, m, CHvCH2), 5.5±5.8 (1H, m,
CHvCH2); 13C NMR d (ppm): 13.8, 14.1, 17.5 (2C), 17.6
(2C), 17.7, 17.9, 37.6, 37.8, 41.3, 41.5, 60.9, 61.1, 62.8,
62.9, 115.2, 115.5, 140.1, 140.2, 168.4, 168.6, 208.1,
208.3; m/z (in mixture) 212 (1, M1), 142 (13), 141 (10),
123 (24), 115 (25), 97 (10), 96 (10), 95 (15), 87 (19), 71
(100), 55 (28). Calcd for C12H20O3 C 67.89, H 9.50; found C
67.7, H 9.2.
1.3.17. 2-Acetyl-3-tert-butyl-pent-4-enoic acid methyl
ester (5q). Two isomers. nmax: 3008, 1745, 1718, 1143,
1
1247 cm21; H NMR d (ppm): 0.84 (9H, s, Me3C), 2.08
1.3.13. 2-Butyryl-3-methyl-pent-4-enoic acid ethyl ester
(5m). Two isomers. nmax: 2975, 1736, 1708, 1234,
(1.5H, s) and 2.20 (1.5H, s, MeCO), 2.6±2.8 (1H, m,
CHCHvCH2), 3.50 (1H, d, Jˆ8.7 Hz, COCHCO), 3.64
(1.5H, s) and 3.70 (1.5H, s, MeO), 5.0±5.1 (2H, m,
CHvCH2), 5.5±6.0 (1H, m, CHvCH2); 13C NMR d
(ppm): 27.3 (3C), 27.7 (3C), 28.7, 29.1, 33.2, 33.5, 52.0,
52.4, 53.1, 53.5, 60.8, 62.0, 118.5, 119.1, 135.6, 135.7,
170.0, 170.1, 202.7, 203.5; m/z 212 (1, M1), 156 (15), 113
(100), 97 (13), 81 (32), 57 (63). Calcd for C12H20O3 C 67.89,
H 9.50; found C 67.9, H 9.5.
1
1180 cm21; H NMR d (ppm): 0.84 (1.5H, t, Jˆ7.1 Hz)
and 0.87 (1.5H, t, Jˆ7.0 Hz, MeCH2CH2), 0.97 (1.5H, d,
Jˆ6.8 Hz) and 1.03 (1.5H, d, Jˆ6.7 Hz, MeCH), 1.20
(1.5H, t, Jˆ7.0 Hz) and 1.23 (1.5H, t, Jˆ6.8 Hz,
MeCH2O), 1.5±1.7 (2H, m, MeCH2CH2), 2.3±2.6 (2H, m,
CH2CO), 2.9±3.1 (1H, m, CHCHvCH2), 3.34 (1H, d,
Jˆ9.8 Hz, COCHCO), 4.10 (1H, q, Jˆ7.2 Hz) and 4.18
(1H, q, Jˆ7.0 Hz, MeCH2O), 4.9±5.1 (2H, m, CHvCH2),
5.5±5.8 (1H, m, CHvCH2); 13C NMR d (ppm): 13.1 (2C),
13.7 (2C), 16.2, 16.4, 17.6, 17.7, 37.4, 37.5, 44.3 (2C), 60.8,
61.0, 64.8 (2C), 115.1, 115.4, 139.9, 140.0, 168.5, 168.6,
204.4 (2C); m/z 212 (1, M1), 142 (23), 141 (10), 127 (22),
113 (10), 97 (11), 96 (12), 95 (16), 71 (100), 69 (21), 55
(19). Calcd for C12H20O3 C 67.89, H 9.50; found C 67.7, H
9.2.
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