Efficient photochemical synthesis of 2-vinylcyclopropanecarbaldehydes, precursors of cyclopropane components present in pyrethroids, by using the oxa-di-π-methane rearrangement

Article abstract of DOI:10.1016/j.tet.2010.09.012

A comparative study on the triplet photoreactivity of a series of β,γ,δ,ε-unsaturated aldehydes 14a-f and 15, using 3-methoxyacetophenone and 4-phenylbenzophenone as sensitizers, has been carried out. When 3-methoxyacetophenone is used as the triplet sensitizer, the aldehydes undergo oxa-di-π-methane rearrangement (ODPM) to afford the corresponding cyclopropanecarbaldehydes 16a-f and 17 in yields ranging from 14% to 62% in addition in most cases to products resulting from decarbonylation. However, when 4-phenylbenzophenone is used as the photosensitizer ODPM products are obtained exclusively in almost quantitative yield. These are additional examples of the recently described, unexpected influence of the nature of the triplet sensitizer on the photoreactivity of organic compounds.

Full text of DOI:10.1016/j.tet.2010.09.012

Tetrahedron 66 (2010) 8690e8697
Contents lists available at ScienceDirect
Tetrahedron
journal homepage: www.elsevier.com/locate/tet
Efficient photochemical synthesis of 2-vinylcyclopropanecarbaldehydes,
precursors of cyclopropane components present in pyrethroids, by using
the oxa-di-
p
-methane rearrangement
*
*
Diego Armesto , Maria J. Ortiz , Antonia R. Agarrabeitia, Noureddin El-Boulifi
Departamento de Química Orgánica I, Facultad de Ciencias Químicas, Universidad Complutense, 28040 Madrid, Spain
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 19 July 2010
Received in revised form 31 August 2010
Accepted 3 September 2010
Available online 15 September 2010
A comparative study on the triplet photoreactivity of a series of b,g,d,3-unsaturated aldehydes 14aef and
15, using 3-methoxyacetophenone and 4-phenylbenzophenone as sensitizers, has been carried out.
When 3-methoxyacetophenone is used as the triplet sensitizer, the aldehydes undergo oxa-di-
p
-methane rearrangement (ODPM) to afford the corresponding cyclopropanecarbaldehydes 16aef and
17 in yields ranging from 14% to 62% in addition in most cases to products resulting from decarbon-
ylation. However, when 4-phenylbenzophenone is used as the photosensitizer ODPM products are ob-
tained exclusively in almost quantitative yield. These are additional examples of the recently described,
unexpected influence of the nature of the triplet sensitizer on the photoreactivity of organic compounds.
Ó 2010 Elsevier Ltd. All rights reserved.
Keywords:
Photochemistry
Oxa-di-p-methane
Pyrethroids
Cyclopropanecarbaldehydes
Triplet sensitization
1. Introduction
stabilities. Pyrethrins and pyrethroids are lipophilic insecticides
that act on the nervous system of insects with high efficiency, but
Pyrethrins are natural insecticides produced by the flowers of
Chrysanthemum cinerafolis and Chrysanthemum coccineum.1 The
major components of these insecticides are esters of chrysanthemic
acid 1 and pyrethric acid 2 with substituted optically active cyclo-
pentenolones 3aec (Fig. 1). The pyrethroids, compounds structur-
ally related to the natural pyrethrins, are usually more active than
the natural products, and have higher thermal and photochemical
they have low toxicity to mammals in general, and humans in
particular, and they are biodegradable.1,2 These properties make
these substances an important family of ecological insecticides,
which is the reason that they are widely used for domestic
applications.
The keystep in the synthetic routes topyrethrins and pyrethroids
is the construction of the substituted cyclopropanecarboxylic acid
moiety that is then esterified with the appropriate alcohol. Many
methods exist for the preparation of these acids, most of which are
patented.1 However, none of these synthetic approaches can be
considered to be general. Among them, the addition of ethyl
diazoacetate to differently substituted 1,3-butadienes and the
addition of sulfur or phosphorus ylides to methyl penta-2,4-dieno-
ates3 have been widely used to obtain most of the common vinyl-
cyclopropanecarboxylic acids, but all of these procedures have
limitations and can be used for the synthesis of only a few
pyrethroids.
H
COOH
H
H
COOH
H
EtO2C
2
1
R
O
3a: R = CH2CH=CHCH=CH2
3b: R = CH2CH=CHCH3
3c: R = CH2CH=CHCH2CH3
HO
H
In the early 90s, our group investigated a novel and potentially
general methodology for the preparation of cyclopropanecarboxylic
acids present in pyrethrins and pyrethroids. The key step in
3
Fig. 1. Components of natural pyrethrins.
this synthetic approach is the 1-aza-di-
rearrangement of
-unsaturated oxime acetates.4 For example, al-
dehydes 4, previously considered to be unreactive in the oxa-di-
-methane (ODPM) rearrangement, were transformed into the
p-methane (1-ADPM)
b,g
* Corresponding authors. Tel.: þ34 913 944 316; fax: þ34 913 944 103; e-mail
p
addresses: darmesto@quim.ucm.es (D. Armesto), mjortiz@quim.ucm.es (M.J. Ortiz).
0040-4020/$ e see front matter Ó 2010 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2010.09.012

D. Armesto et al. / Tetrahedron 66 (2010) 8690e8697
8691
corresponding cyclopropanecarbaldehydes 5 by a route involving
their conversion to oxime acetates 6, followed by acetophenone
triplet sensitized irradiation that yields the corresponding cyclo-
propane oxime acetates 7, as shown in Scheme 1 (path a). Thermal
elimination of acetic acid in 7 affords the corresponding nitriles,
which are reduced to form aldehydes 5. Finally, oxidation of 5 by
conventional methods gives the cyclopropanecarboxylic acids 8
(Scheme 1, path a). This method proved to have general applicability
and was patented.5
not undergo the DPM reaction in the triplet excited state, as has
been stated in books and monographs on this topic. However, our
recent observations show that 1,4-dienes 12 do rearrange to the
corresponding vinylcyclopropanes 13 in high yield when suitable
triplet sensitizers are used (Fig. 2).8
Based on the observations described above, we have carried out
a study on the comparative photoreactivity of a series of b,g,d,3-
unsaturated aldehydes 14aef and 15 using3-methoxyacetophenone
and 4-phenylbenzophenone as triplet sensitizers. The effort was
aimed atdeterminingif thecorrespondingODPMproducts16 and17,
structurally related to cyclopropane components present in pyre-
thrins and pyrethroids, could be obtained in high yields and if al-
ternative reaction modes, previously unreported for these
compounds, could be observed (Fig. 3).
CHO
hν
N
OAc
N
path a
R1
R1
R1
R2
OAc
R2
R2
6
7
4
CHO
hν
CHO
CHO
COOH
path b
R1
R1
R2
16
R2
R1
R2
R1
R2
14
5
8
14a; 16a = R1 = R2 = CH3
Scheme 1. Synthesis of cyclopropanecarboxilic acids via 1-ADPM and ODPM
14b; 16b = R1; R2 = -(CH2)4-
14c; 16c = R1 = CO2Et; R2 = H
14d; 16d = R1 = CO2Et; R2 = CH3
14e; 16e = R1 = CO2Et; R2 = CN
14f; 16f = R1 = R2 = CN
rearrangements.
Some years later, studies carried out in our laboratory demon-
strated that, contrary to the common belief, suitable substituted
b,g-unsaturated aldehydes do undergo ODPM rearrangement, with
high chemical efficiencies and in some cases high degrees of dia-
stereoselectivity (Scheme 1, path b).6 These results open a new and
easier route to compounds 8. The results of recent investigations in
our group demonstrate that the nature of the sensitizer plays an
CHO
important role on the photochemical reactivity of
b,g-unsaturated
CHO
ketones. Thus, -unsaturated acyclic ketones 9, previously de-
b,g
17
15
scribed as being unreactive in the ODPM mode, afford the corre-
sponding cyclopropyl ketones 10 in high yields when they are
irradiated using sensitizers with triplet energies that are slightly
Fig. 3. Starting aldehydes (14 and 15) and ODPM photoproducts (16 and 17).
higher than those of the b,g-alkene moiety. In some cases, rear-
The sensitizers used in the study were selected based on the
following considerations. 3-Methoxyacetophenone has been used
as triplet sensitizer previously to study the photoreactivity of
compounds 14a and 14b, This selection was based on the fact that
ranged enones 11, resulting from photoinduced 1,3-acyl migration
in 9, were also obtained depending on the sensitizer used to pro-
mote the reaction (Fig. 2).7
the triplet energy (ET¼71.0 kcal molꢀ1 9
) of this sensitizer is ap-
proximately 11e13 kcal molꢀ1 higher than those of the diene
moieties present in 14a,b. This energy difference ensures that ef-
ficient energy transfer would take between the triplet excited state
of the sensitizer and the diene. In addition, the absorption spec-
trum of 3-methoxyacetophenone does not overlap to a large extend
with those of aldehydes 14 and 15. 4-Phenylbenzophenone was
selected as sensitizer used in this effort since excellent yields of
products were obtained using this sensitizer in our previous studies
R2 R1
R3
R4
R2 R1
R3 R4
O
O
R3
R2
R4
R1
O
9
10
11
R3
R2
R1
R1
on the photoreactivity of
b,g-unsaturated ketones and acyclic
R1
R1
R2
1,4-dienes.7,8 However, it should be noted that the triplet energy
(ET¼61.0 kcal molꢀ1)9 of this sensitizer is slightly higher than those
of the diene moieties present in 14 and 15. Again, the absorption
spectrum of phenylbenzophenone overlaps only minimally with
those 14 and 15.
R3
13
12
Fig. 2. Triplet photoreactivity of
b,g-unsaturated acyclic ketones and 1,4-dienes.
This surprising influence of the nature of the sensitizer on the
triplet reactivity of organic compounds was further demonstrated
2. Results and discussion
in a recent study of the di-p-methane rearrangement (DPM) of
a series of acyclic 1,4-dienes 12. Some compounds in the series
probed were previously reported to undergo the DPM rearrange-
ment only very inefficiently when common triplet sensitizers, such
as acetophenone or benzophenone, were used. Based on these
earlier findings, it was concluded that most acyclic 1,4-dienes do
The synthesis of 14a,b,4 14c,5 and 154 has been reported pre-
viously. Aldehydes 14def, described here for the first time, were
prepared from aldehyde 184 by using conventional methods
(Scheme 2). Compounds 14 and 15 were obtained with the ste-
reochemistry shown in Scheme 2 in ca. 50% isolated yields.

8692
D. Armesto et al. / Tetrahedron 66 (2010) 8690e8697
i. LDA, CO Et(CH )CHPO(OEt)
2
CHO
2
3
THF, -78 ºC, 1h, rt, 24 h
R1
R2
ii. CaCO , CH I
3
3
EtO2C
R1
CH CN/H O, 60 ºC, 17 h
R2
3
2
14d
19
20
19a = R1 = R2 = CH3
i. CNCH CO Et, CH CO NH
4
CHO
2
2
3
2
benzene/AcOH, reflux, 12 h
20a = R1 = CO2Et; R2= H
S
19b = R1; R2= -(CH2)4-
19c = R1 = CO2Et; R2 = H
19d = R1 = CO2Et; R2= CH3
20b = R1 = CO2Et; R2= CH3
ii. CaCO , CH I
S
3
3
EtO2C
OHC
CN
CN
CH CN/H O, 60 ºC, 17 h
3
2
18
14e
R
i. CNCH CN, β-alanine
2
CHO
toluene/AcOH, reflux, 24 h
R
NC
ii. BF Et O, HgO
3
2
CN
NC
THF/H O, rt, 24 h
2
21
14f
21a = R = CO2Et
21b = R = CN
Scheme 2. Synthetic route for aldehydes (14def).
Fig. 4. Decarbonylation products (19e21).
Irradiation of 14a,b in the presence of 3-methoxyacetophenone
has been described previously by us. Under these conditions, al-
dehydes 14a,b afford the corresponding ODPM products 16a,b in
moderate yields (52% and 47%, respectively).6
showed that compounds 19a (6%) and 19b (6%), formed by re-
spective decarbonylation of 14a and 14b, are present (Fig. 4 and
Table 1). The fact that these alkenes were not detected in the
earlier effort was probably a consequence of their low boiling
points that led to their evaporation during conventional workup
procedures. It is worth noting at this point that the decarbon-
ylation process observed for compounds 14 is formally a Norrish
type I reaction, which is commonly observed in the direct irradi-
ation promoted reactions of carbonyl compounds. However, in the
cases described above, the processes are not taking place by direct
irradiation of the carbonyl group but rather by triplet sensitization
of the diene unit. This is a situation that has been seldom
observed.7,10
When aldehydes 14aef and 15 are irradiated for the same time
periods using 4-phenybenzophenone as the sensitizer, the decar-
bonylation pathway is suppressed and the corresponding ODPM
products 16 and 17 are obtained in almost quantitative isolated
yields (Fig. 3 and Table 1). The results confirm that the nature of the
triplet sensitizer has an important influence on the outcome of
these photochemical reactions.
3-Methoxyacetophenone-sensitized irradiation of aldehydes
14cef and 15 affords the corresponding cyclopropanes 16cef and
17, resulting from ODPM rearrangements, in isolated yields ranging
from 14% to 65% (Fig. 3 and Table 1). In addition to the ODPM
process, another reaction mode is followed under these conditions.
Thus, photosensitized reaction of 14c also gives an inseparable
mixture of dienes 19c and 20a, resulting from decarbonylation, in
4% overall yield (Fig. 4). This reaction mode was also observed to
take place in the reaction 14d that yields 19d and 20b, in 18% overall
yield (Fig. 4). However, for unknown reasons, the photoinduced
decarbonylation of 14e and 14f affords the respective tetraenes 21a
and 21b, resulting from dimerization of the radicals formed by
decarbonylation (Fig. 4 and Table 1). Finally, aldehyde 15 does not
undergo competitive decarbonylation and, as a result, it reacts to
produce the ODPM product 17 (65%) exclusively. In each case, in-
creasing the irradiation time brings about complete consumption
of the starting material without improving the yield of ODPM
product.
The results described above demonstrate that by using a sensi-
tizer with a triplet energy that is close to the acceptor diene the
yield of the rearrangement products increase and those of
the decarbonylation products decrease. It can be argued that the
lower yield observed in the photoreactions promoted by using
3-methoxyacetophenone as sensitizer are a result of the fact that
the alkenes formed by decarbonylation can act as quenchers of
the sensitizer, which leads to diminished efficiencies of the reaction.
However, an increased yield of product is also observed in the
reactions of 15, substances that do not decarbonylate when
3-methoxyacetophenone is used as sensitizer. Another factor to take
into account is that the triplet energy of 4-phenybenzophenone
(ET¼61.0 kcal molꢀ1)9 is lower than that of the alkene unit present in
cyclopropanes 16 and 17. This factor prevents intermolecular energy
transfer and, therefore, destruction of the photoproducts. The pos-
sibility that the decarbonylation products observed in the photore-
actions sensitized by 3-methoxyacetophenone could arise by direct
absorption of light was also considered, but this option was dis-
carded based on the fact that the concentrations used in these
processes insures that more than 99% of the light is being absorbed
by the sensitizer. Furthermore, aldehydes 15 do not undergo
decarbonylation under the same irradiation conditions that are used
for 14, even though decarbonylation is the only reaction observed
upon direct irradiation of 15.
Table 1
Reaction conditions and yields of products in the irradiation of
aldehydes 14 and 15
b
,
g
,
d,
3
-unsaturated
Compd
Sens.a
Irrad. time
(min)
ODPM
(yield, %)
Dienes
(yield, %)
S.M.
(yield, %)
14a
14a
14b
14b
14c
14c
14d
14d
14e
14e
14f
14f
15
3-MAP
4-PBP
3-MAP
4-PBP
3-MAP
4-PBP
3-MAP
4-PBP
3-MAP
4-PBP
3-MAP
4-PBP
3-MAP
4-PBP
15
15
20
20
45
45
60
60
45
45
60
60
180
180
16a (52)
16a (94)
16b (47)
16b (94)
16c (22)
16c (96)
16d (14)
16d (92)
16e (47)
16e (95)
16f (34)
16f (93)
17 (65)
19a (6)
14a (30)
14b (30)
14c (52)
14d (55)
14e (39)
14f(34)
15 (19)
19b (6)
19c, 20a (4)
19d, 20b (18)
21a (4)
21b (4)
15
17 (95)
a
3-MAP¼3-methoxyacetophenone; 4-PBP¼4-phenylbenzophenone.
In our previous study, the decarbonylation process was not
observed to participate in photoreactions of 14a and 14b. There-
fore, the photochemical behavior of these two aldehydes was
reinvestigated. A careful analysis of the photoreaction mixture

D. Armesto et al. / Tetrahedron 66 (2010) 8690e8697
8693
3. Conclusions
at ꢀ78 ꢁC for 2 h, allowed to warm at room temperature, and stirred
for 24 h before being quenched with saturated NH4Cl solution and
extracted with Et2O. The combined organic phases were dried, fil-
tered, and concentrated to dryness. Flash chromatography (hexane/
Et2O 97:3) afforded ethyl (2E,4E)-6-(1,3-dithian-2-yl)-6-methyl-
hepta-2,4-dienoate5 (1.94 g, 81%) as a yellow solid. Mp 96e98 ꢁC
(hexane). Found: C, 58.8; H, 7.7; S, 22.4. C14H22O2S2 requires C,
58.70; H, 7.74; S, 22.39%. IR (KBr): 1730, 1650, 1630 cmꢀ1; 1H NMR
For many years a general consensus has been that the main
requirement in photochemical reactions promoted by triplet sen-
sitization is that efficient energy transfer from the triplet sensitizer
to the acceptor molecule be insured. It was generally believed that
once this energetic requirement is achieved the triplet excited
substrate would follow a particular reaction pathway, independent
of the nature of the sensitizer used. However, recent studies carried
out by us show that organic molecules can react by different triplet
pathways depending on the nature of the triplet sensitizer used.7,8
The photoreactivity described above for compounds 14 and 15 is
yet another example of this interesting behavior. Specifically, irra-
diation of aldehydes 14 and 15 using 4-phenybenzophenone as
sensitizer, which has a triplet energy that is slightly above the ac-
ceptor alkene, affords the corresponding cyclopropanes 16 and 17
in almost quantitative yields without competition from decarbon-
ylation processes. In contrast, decarbonylation becomes a highly
competitive reaction pathway in reactions of these substances
when sensitized by 3-methoxyacetophenone, with an energy ap-
proximately 11e13 kcal molꢀ1 higher than the triplet energy of the
acceptor moieties present in 14 and 15. The high yields of products
obtained in all reactions studied suggest that the ODPM rear-
(200 MHz, CDCl3):
d
¼1.20 (s, 6H, 2CH3), 1.21 (t, J¼7.1 Hz, 3H, CH3),
1.66e1.84 (m, 1H, 1/2CH2), 1.96e2.06 (m, 1H, 1/2CH2), 2.78e2.83
(m, 4H, 2CH2S), 3.99 (s,1H, CH), 4.12 (q, J¼7.1 Hz, 2H, CH2O), 5.78 (d,
J¼15.4 Hz, 1H, CH]CHCO2Et), 6.03e6.20 (m, 2H, CH]CH),
7.17e7.29 (m, 1H, CH]CHCO2Et); 13C NMR (50 MHz, CDCl3):
d
¼14.3, 25.1, 25.9, 31.3, 41.7, 60.1, 60.2, 120.7, 126.2, 144.7, 149.8,
167.0; MS: m/z (%)¼119 (Mþꢀ167,100). HRMS-ESIþ: found 287.1137.
C14H22O2S2þHþ requires 287.1140.
The removal of the thioacetal group was carried out by the
method of Procter and co-workers.11 A solution of the protected
aldehyde (1.93 g, 6.75 mmol), CaCO3 (2.02 g, 20.2 mmol), CH3I
(4.2 mL, 67.5 mmol) in a 4:1 mixture of CH3CN/H2O (40 mL) was
stirred at 60 ꢁC for 17 h. The solution was filtered on silica gel,
washed with Et2O, and evaporated to dryness. Flash chromatog-
raphy (hexane/Et2O 95:5) afforded (3E,5E)-14c5 (1.22 g, 86%) as
a colorless oil. Found: C, 67.4; H, 8.1. C11H16O3 requires C, 67.32; H,
rangement of b,g,d,3-unsaturated aldehydes using 4-phenybenzo-
phenone as triplet sensitizer is a general, highly efficient synthetic
route for the preparation of cyclopropanecarboxylic acids present
in pyrethrins and pyrethroids.
8.22%. IR (neat): 2840, 2730, 1740, 1710 cmꢀ1
CDCl3):
;
1H NMR (200 MHz,
¼1.18 (s, 6H, 2CH3), 1.22 (t, J¼7.1 Hz, 3H, CH3), 4.13 (q,
d
J¼7.1 Hz, 2H, CH2O), 5.82 (d, J¼15.4 Hz, 1H, CH]CHCO2Et), 5.99 (d,
J¼15.6, 1H, CH]CH), 6.17 (dd, J¼15.6, 10.3 Hz, 1H, CH]CH), 7.19
(dd, J¼15.4, 10.3 Hz, 1H, CH]CHCO2Et), 9.34 (s, 1H, CHO); 13C NMR
4. Experimental section
4.1. General
(50 MHz, CDCl3):
d
¼14.2, 21.3, 49.2, 60.3, 121.9, 128.7, 143.3, 143.6,
166.7, 201.1; MS: m/z (%)¼43 (15), 79 (32), 93 (100), 167 (Mþꢀ29,
91); HRMS-ESIþ: found 197.1175. C11H16O3þHþ requires 197.1178;
Starting materials and reagents are commercially available un-
less synthesis is described. The solvents were dried and distilled,
before use. Spectral data of the known compounds were in accor-
dance with the literature data. Flash chromatography was per-
formed using silica gel 60 (40e63 mm). 1H and 13C NMR spectra
were measured on a BRUKER AC-200 spectrometer at 200 and
UV (CH2Cl2): lmax
(
3)¼255 nm (39,127), 313 nm (1765).
4.3. (3E,5E)-6-Ethoxycarbonyl-2,2-dimethylhepta-3,5-dienal
(14d)
This compound was synthesized following the same procedure as
in 14c, from diisopropylamine (0.9 mL, 6.2 mmol), BuLi (3.9 mL,
6.3 mmol of 1.6 M solution in hexane), ethyl 2-(diethoxyphosphoryl)
propanoate (1.4 g, 6.2 mmol), and 18 (1.22 g, 5.7 mmol) in dry THF
(50 mL). Flash chromatography (hexane/Et2O 97:3) afforded ethyl
(2E,4E)-6-(1,3-dithian-2-yl)-2,6-dimethylhepta-2,4-dienoate (1.5 g,
87%)as a yellowoil. Found: C, 60.0; H, 8.0; S, 21.3. C15H24O2S2 requires
50 MHz, respectively, in CDCl3 solution. Chemical shifts (d) were
expressed in parts per million (ppm) relative to tetramethylsilane
(TMS), and coupling constants J were given in hertz (Hz). Infrared
spectra were recorded as a thin film using NaCl plate on a PER-
KINeELMER 781 spectrophotometer. UV/visible spectra were
measured on PERKINeELMER LAMBDA 3B in CH2Cl2 solution. Mass
spectra were registered by electron impact at 70 eV in a VGI2-250
spectrometer. High resolution mass spectra were determined by
electro spray ionization in the positive mode (ESIþ) in a Accurate-
Mass Q-TOF LC/MS 6520 (Agilent Technologies). Combustion
analyses (C, H, N) were obtained on a LECO CHNS-932 apparatus at
the Universidad Complutense de Madrid analysis services and were
within 0.4% of the theoretical values.
C, 59.96; H, 8.05; S, 21.34%. IR (neat): 1697, 1635 cmꢀ1
;
1H NMR
(200 MHz, CDCl3):
d
¼1.21 (s, 6H, 2CH3), 1.22 (t, J¼7.1 Hz, 3H, CH3),
1.63e1.82 (m,1H,1/2CH2),1.87 (d, J¼1.3 Hz, 3H, CH3C]C),1.93e2.09
(m, 1H, 1/2CH2), 2.77e2.83 (m, 4H, 2CH2S), 4.00 (s, 1H, CH), 4.11 (q,
J¼7.1 Hz, 2H, CH2O), 6.09 (d, J¼15.3 Hz, 1H, CH]CH), 6.28 (dd, J¼15.3,
10.7 Hz, 1H, CH]CH), 7.13 (dd, J¼10.7, 1.3 Hz, 1H, CH]C); 13C NMR
(50 MHz, CDCl3):
d
¼12.8, 14.4, 25.3, 26.0, 31.3, 41.8, 60.3, 60.5, 123.7,
Aldehydes 14a,b4 and 154 were synthesized by the methods
previously described. Aldehyde 14c was synthesized by a modifi-
cation of the procedure previously described.5
126.5, 138.3, 148.4, 168.4; MS: m/z (%)¼43 (11), 91 (7), 119 (100), 194
(Mþꢀ106, 9). HRMS-ESIþ: found 301.1296. C15H24O2S2þHþ requires
301.1297.
The removal of the thioacetal group was carried out by the
method of Procter and co-workers.11 A solution of the protected
aldehyde (1.5 g, 5 mmol), CaCO3 (1.5 g, 15 mmol), CH3I (3.1 mL,
50 mmol) in a 4:1 mixture of CH3CN/H2O (40 mL) was stirred at
60 ꢁC for 17 h. The solution was filtered on silica gel, washed with
Et2O, and evaporated to dryness. Flash chromatography (hexane/
Et2O 95:5) afforded (3E,5E)-14d (1.22 g, 67%) as a colorless oil.
Found: C, 68.5; H, 8.6. C12H18O3 requires C, 68.54; H, 8.63%. IR
4.2. (3E,5E)-6-Ethoxycarbonyl-2,2-dimethylhexa-3,5-dienal (14c)
This compound was synthesized in two steps from (E)-4-
(1,3-dithian-2-yl)-4-methylpent-2-enal (18).4 To a solution of lith-
ium diisopropylamide (9.2 mmol) in dry THF (30 mL), prepared
from diisopropylamine (1.3 mL, 9.2 mmol) and BuLi (5.7 mL,
9.2 mmol of 1.6 M solution in hexane), at ꢀ78 ꢁC under an atmo-
sphere of argon, was added slowly dropwise ethyl 2-(diethoxy-
phosphoryl)acetate (2.05 g, 9.2 mmol). The mixture was stirred for
45 min and then a solution of 18 (1.8 g, 8.3 mmol) in dry THF
(50 mL) was added dropwise. The reaction mixture was kept
(neat): 2810, 2707, 1705, 1637 cmꢀ1 1H NMR (200 MHz, CDCl3):
;
d¼1.19 (s, 6H, 2CH3), 1.23 (t, J¼7.1 Hz, 3H, CH3), 1.88 (d, J¼1.3 Hz, 3H,
CH3C]C), 4.13 (q, J¼7.1 Hz, 2H, CH2O), 5.95 (d, J¼15.5 Hz, 1H, CH]
CH), 6.32 (dd, J¼15.5, 11.7 Hz, 1H, CH]CH), 7.10 (dd, J¼11.7, 0.6 Hz,

8694
D. Armesto et al. / Tetrahedron 66 (2010) 8690e8697
1H, CH]C), 9.35 (s, 1H, CHO); 13C NMR (50 MHz, CDCl3):
d
¼13.1,
(m, 1H, 1/2CH2), 2.80e2.85 (m, 4H, 2CH2O), 4.03 (s, 1H, CH), 6.53
(dd, J¼15.3, 10.7 Hz, 1H, CH]CH), 6.71 (d, J¼15.3 Hz, 1H, CH]CH),
14.7, 21.8, 49.8, 60.9, 126.7, 128.3, 137.7, 142.3, 168.7, 201.9; MS: m/z
(%)¼43 (100), 71 (30), 113 (15), 141 (Mþꢀ69, 14); HRMS-ESIþ: found
7.42 (d, J¼10.7 Hz, 1H, CH]C); 13C NMR (50 MHz, CDCl3):
¼24.9,
d
211.1333. C12H18O3þHþ requires 211.1335; UV (CH2Cl2): lmax
(3)¼
25.7, 31.3, 43.1, 59.2, 85.3, 111.1, 112.9, 123.6, 160.7, 162.1; MS: m/z
(%)¼75 (6), 106 (9), 119 (100), 264 (Mþ, 1); HRMS-ESIþ: found
265.0832. C13H16N2S2þHþ requires 265.0834.
261 nm (6989), 313 nm (1).
4.4. (3E,5E)-6-Cyano-6-ethoxycarbonyl-2,2-dimethylhexa-3,5-
dienal (14e)
The removal of the thioacetal group was brought about fol-
lowing the same procedure as in 14e using red mercuric oxide
(671 mg, 3.1 mmol) in THF (100 mL of 15% aqueous), BF3$Et2O
(440 mg 3.1 mmol), and the protected aldehyde (500 mg,
2.06 mmol) in THF (20 mL). Flash chromatography (hexane/EtAcO
8:2) afforded the aldehyde (E)-14f (207 mg, 58%) as a yellow oil.
Found: C, 68.9; H, 5.8; N, 16.1. C10H10N2O requires C, 68.95; H, 5.79;
A solution of 18 (2 g, 9.3 mmol), ethyl cyanoacetate (4.7 g,
41.6 mmol), acetic acid (2.4 mL), and ammonium acetate (855 mg,
11.1 mmol) in benzene (40 mL) was refluxed for 12 h. The water
generated during the condensation was azeotropically removed by
using a DeaneStark trap. The mixture was then cooled, diluted with
Et2O, and washed with water. The organic layers were dried
(MgSO4), filtered, and concentrated to dryness. Flash chromatog-
raphy (hexane/Et2O 95:5) afforded ethyl (2E,4E)-2-cyano-6-
(1,3-dithian-2-yl)-6-methylhepta-2,4-dienoate (2,7 g, 94%) as
a yellow oil. Found: C, 57.8; H, 6.8; N, 4.5; S, 20.6. C15H21NO2S2
requires C, 57.84; H, 6.80; N, 4.50; S, 20.59%. IR (neat): 2227, 1724,
N, 16.08%. IR (neat): 2870, 2740, 2100, 1700, 1630 cmꢀ1 1H NMR
;
(200 MHz, CDCl3):
d
¼1.28 (s, 6H, 2CH3), 6.51e6.69 (m, 2H, CH]CH),
7.42 (dd, J¼8.3, 2.2 Hz, 1H, CH]C), 9.24 (s, 1H, CHO); 13C NMR
(50 MHz, CDCl3):
d
¼21.4, 50.4, 85.3, 111.0, 112.9, 125.2, 155.5, 159.8,
199.9; MS: m/z (%)¼39 (48), 43 (28), 79 (41), 104 (37), 118 (77), 131
(41), 145 (100), 174 (Mþ, 2); HRMS-ESIþ: found 175.0871.
C10H10N2OþHþ requires 175.0872; UV (CH2Cl2): lmax
(
3)¼283 nm
1624 cmꢀ1
;
1H NMR (200 MHz, CDCl3):
d
¼1.27 (s, 6H, 2CH3), 1.29
(23,663), 313 nm (7285).
(t, J¼7.1 Hz, 3H, CH3),1.66e1.85 (m,1H,1/2CH2),1.98e2.11 (m,1H,1/
2CH2), 2.80e2.86 (m, 4H, 2CH2S), 4.04 (s, 1H, CH), 4.25 (q, J¼7.1 Hz,
2H, CH2O), 6.48e6.71 (m, 2H, CH]CH), 7.81 (d, J¼10.2 Hz, 1H, CH]
4.6. Preparative photolyses; general procedure
C); 13C NMR (50 MHz, CDCl3):
d
¼14.1, 24.8, 25.6, 31.1, 42.6,
The photolyses were carried out in a quartz immersion well
apparatus with a Pyrex filter and a 400 W medium pressure Hg arc
lamp. Solutions of the compounds and the sensitizer (3-methox-
yacetophenone or 4-phenylbenzophenone) in dry CH2Cl2 were
purged for 1 h with argon and irradiated under a positive pressure
of argon. After completion of the irradiation, the solvent was
evaporated under reduced pressure, and the sensitizers and the
products were separated by flash chromatography on silica gel.
59.4, 62.2, 104.7, 114.2, 123.9, 155.7, 159.8, 162.0; MS: m/z (%)¼45
(15), 106 (7), 119 (Mþꢀ192, 100); HRMS-ESIþ: found 312.1090.
C15H21NO2S2þHþ requires 321.1093.
The removal of the thioacetal group was carried out by the
method of Vedejs and Fuchs.12 To a stirred suspension of red
mercuric oxide (2.8 g, 13 mmol) in THF (100 mL of 15% aqueous)
under an argon atmosphere, BF3$Et2O (1.7 mL, 13 mmol) was
added. Then, a solution of the protected aldehyde (2.7 g, 8.7 mmol)
in THF (20 mL) was added through a dropping funnel. The stirred
mixture was maintained at room temperature for 20 min and then
gently refluxed for 2 h to complete the reaction. The mixture was
allowed to cool to room temperature and the mercuric salts were
precipitated by addition of 30 mL of Et2O and then filtered. The
filtrate was washed with saturated NaHCO3 solution, then with
brine and finally dried. The organic extracts were filtered and
concentrated to dryness. Flash chromatography (hexane/EtAcO
95:5) afforded the aldehyde (3E,5E)-14e (1.1 g, 54%) as a yellow oil.
Found: C, 65.1; H, 6.8; N, 6.3. C12H15NO3 requires C, 65.14; H, 6.83;
4.6.1. 3-Methoxyacetophenone-sensitized irradiation of 14a.
Compound (E)-14a (200 mg, 1.34 mmol) and 3-methoxyaceto-
phenone (890 mg, 5.9 mmol) in CH2Cl2 (160 mL) was irradiated for
15 min. Chromatography (hexane/Et2O 8:2) gave alkene (E)-19a
(10 mg, 6%) as a colorless oil, starting aldehyde 14a (60 mg, 30%) as
a 4:1 mixture of E/Z isomers and cyclopropylaldehyde (E)-16a4
(104 mg, 52%). Further elution with Et2O afforded 5 mg of highly
polar material.
Compound (E)-14a (200 mg, 1.34 mmol) and 3-methoxyaceto-
phenone (890 mg, 5.9 mmol) in CH2Cl2 (160 mL) was irradiated for
45 min. Chromatography (hexane/Et2O 98:2) gave alkene (E)-19a
(12 mg, 7%), starting aldehyde (E)-14a (2 mg, 1%), and cyclo-
propylaldehyde 16a4 (74 mg, 37%) as a 5:1 mixture of E/Z isomers.
Further elution with Et2O afforded 65 mg of highly polar material.
N, 6.33%. IR (neat): 2814, 2754, 2230, 1728, 1626, 1589 cmꢀ1
;
1H
NMR (200 MHz, CDCl3):
d
¼1.13 (s, 6H, 2CH3), 1.15 (t, J¼7.1 Hz, 3H,
CH3), 4.12 (q, J¼7.1 Hz, 2H, CH2O), 6.37e6.55 (m, 2H, CH]CH), 7.64
(dd, J¼8.9, 1.7 Hz, 1H, CH]C), 9.35 (s, 1H, CHO); 13C NMR (50 MHz,
CDCl3):
d
¼14.2, 21.4, 50.3, 62.2, 106.2, 114.0, 125.9, 153.2, 154.7,
161.9, 200.3; MS: m/z (%)¼77 (66), 91 (67), 147 (100), 192 (71), 221
4.6.1.1. Compound (E)-19a. Found: C, 87.0; H, 13.0. C9H14 re-
(Mþ, 2); HRMS-ESIþ: found 222.1130. C12H15NO3þHþ requires
quires C, 87.02; H, 12.98%. IR (neat): 1630 cmꢀ1; 1H NMR (200 MHz,
222.1131; UV (CH2Cl2): lmax
(3)¼276 nm (29,355), 313 nm (8889).
CDCl3):
d
¼0.94 (d, J¼6.7 Hz, 6H, CH(CH3)2), 1.68 (br s, 6H, 2CH3C]
C), 2.18e2.35 (m, 1H, CH(CH3)2), 5.46 (dd, J¼15.1, 6.9 Hz, 1H, CH]
CH), 5.71 (d, J¼10.7 Hz, 1H, CH]C), 6.15 (ddd, J¼15.1, 10.7, 1.1 Hz,
4.5. (E)-6,6-Dicyano-2,2-dimethylhexa-3,5-dienal (14f)
1H, CH]CH); 13C NMR (50 MHz, CDCl3):
d¼18.0, 22.5, 25.5, 27.0,
A
solution of 18 (1.5 g, 13.2 mmol), malononitrile (2 g,
31.2, 123.5, 125.0, 132.7, 139.0; HRMS-ESIþ: found 125.1329.
9.3 mmol), -alanine (280 mg, 3.1 mmol), and acetic acid (4 mL) in
b
C9H16þHþ requires 125.1331.
toluene (40 mL) was refluxed for 24 h. The water generated during
the condensation was azeotropically removed by using a Dean-
eStark trap. The mixture was then cooled, diluted with Et2O, and
washed with water. The organic layers were dried (MgSO4), filtered,
and concentrated to dryness. Flash chromatography (hexane/EtAcO
8:2) afforded [(2E)-4-(1,3-dithian-2-yl)-4-methylpent-2-enyli-
dene]malononitrile (2,25 g, 92%) as a yellow oil. Found: C, 59.0; H,
6.1; N,10.6; S, 24.2. C13H16N2S2 requires C, 59.05; H, 6.10; N,10.59; S,
4.6.2. 4-Phenylbenzophenone-sensitizedirradiationof14a. Compound
(E)-14a (160 mg, 1.05 mmol) and 4-phenylbenzophenone (880 mg,
3.4 mmol) in CH2Cl2 (160 mL) was irradiated for 15 min. Chroma-
tography (hexane/Et2O 98:2) gave cyclopropylaldehyde 16a4
(150 mg, 94%) as a 6:1 mixture of E/Z isomers. Further elution with
Et2O afforded 5 mg of highly polar material.
24.25%. IR (neat): 2255, 2231, 1620 cmꢀ1
;
1H NMR (200 MHz,
4.6.3. 3-Methoxyacetophenone-sensitizedirradiationof14b. Compound
(E)-14b (200 mg, 1.13 mmol) and 3-methoxyacetophenone (800 mg,
CDCl3):
d
¼1.26 (s, 6H, 2CH3), 1.66e1.85 (m, 1H, 1/2CH2), 1.98e2.08

D. Armesto et al. / Tetrahedron 66 (2010) 8690e8697
8695
5.3 mmol) in CH2Cl2 (160 mL) was irradiated for 20 min. Chroma-
tography (hexane/Et2O 95:5) gave alkene (E)-19b (10 mg, 6%) as
a colorless oil, starting aldehyde 14b (60 mg, 30%) as a 3:2 mixture of
E/Z isomers, and cyclopropylaldehyde 16b4 (94 mg, 47%) as a 8:1
mixture of E/Z isomers. Further elution with Et2O afforded 7 mg of
highly polar material.
Compound (E)-14b (200 mg, 1.13 mmol) and 3-methoxy-
acetophenone (800 mg, 5.3 mmol) in CH2Cl2 (160 mL) was irradi-
ated for 45 min. Chromatography (hexane/Et2O 95:5) gave alkene
(E)-19b (10 mg, 6%), starting aldehyde (E)-14b (8 mg, 4%), and
cyclopropylaldehyde 16b4 (72 mg, 36%) as a 6:1 mixture of E/Z
isomers. Further elution with Et2O afforded 37 mg of highly polar
material.
CHCO2Et, Zcyclo,ECeC), 5.94 (d, J¼15.4 Hz, 0.66H, CH]CHCO2Et,
Ecyclo,ECeC), 6.59 (dd, J¼15.4, 9.9 Hz, 0.33H, CH]CHCO2Et, Zcyclo,ECeC),
7.14 (dd, J¼15.4, 10.2 Hz, 0.66H, CH]CHCO2Et, Ecyclo,ECeC), 9.45
(d, J¼4.4 Hz, 0.33H, CHO, Zcyclo,ECeC), 9.57 (d, J¼5.0 Hz, 0.66H, CHO,
Ecyclo,ECeC); 13C NMR (50 MHz, CDCl3):
d¼14.2 (Ecyclo,ECeC), 15.2
(Zcyclo,ECeC), 15.6 (Zcyclo,ECeC), 21.1 (Ecyclo,ECeC), 22.2 (Ecyclo,ECeC),
28.5 (Zcyclo,ECeC), 29.7 (Zcyclo,ECeC), 33.1 (Ecyclo,ECeC), 36.7 (Ecyclo,ECeC),
38.5 (Zcyclo,ECeC), 43.0 (Zcyclo,ECeC), 44.6 (Ecyclo,ECeC), 60.3
(Ecyclo,ECeC), 65.8 (Zcyclo,ECeC), 122.9 (Ecyclo,ECeC), 123.7 (Zcyclo,ECeC),
142.7 (Zcyclo,ECeC), 145.0 (Ecyclo,ECeC), 166.2 (Zcyclo,ECeC and Ecyclo,ECeC),
198.7 (Ecyclo,ECeC), 199.2 (Zcyclo,ECeC).
4.6.5.3. Compounds (2E,4E)-19c and (E)-20a. 1H NMR
(200 MHz, CDCl3):
d¼0.97 (d, J¼6.7 Hz, 5.4H, CH(CH3)2, 19c), 1.21 (t,
4.6.3.1. Compound (E)-19b. Found: C, 87.7; H, 12.3. C11H18 re-
J¼7.1 Hz, 3H, CH3), 1.54 (s, 0.3H, CH3C]C, 20a),1.66 (s, 0.3H, CH3C]
C, 20a), 2.26e2.43 (m, 0.9H, CH(CH3)2, 19c), 2.80 (texp, J¼6.4 Hz,
0.2H, CH2, 20a), 4.10 (q, J¼7.1 Hz, 0.2H, CH2O, 20a), 4.12 (q, J¼7.1 Hz,
1.8H, CH2O, 19c), 5.07 (t, J¼6.4 Hz, 0.1H, CH]C(CH3)2, 20a), 5.72 (d,
J¼15.3 Hz, 0.9H, CH]CHCO2Et, 19c), 5.74 (d, J¼15.6 Hz, 0.1H, CH]
CHCO2Et, 20a), 5.95e6.14 (m, 1.8H, CH]CH, 19c), 6.86 (dt, J¼15.6,
6.2 Hz, 0.1H, CH]CHCO2Et, 20a), 7.12e7.25 (m, 0.9H, CH]CHCO2Et,
quires C, 87.92; H, 12.08%. IR (neat): 1630 cmꢀ1; 1H NMR (200 MHz,
CDCl3):
d
¼1.02 (d, J¼6.6, 6H, CH(CH3)2), 1.62e1.73 (m, 4H, 2CH2),
2.27e2.36 (m, 5H, CH(CH3)2 and 2CH2), 5.50 (dd, J¼14.9, 7.1 Hz, 1H,
CH]CH), 5.91 (dt, J¼10.7, 2.2 Hz, 1H, CH]C), 6.08 (ddd, J¼14.9,
10.7, 1.0 Hz, 1H, CH]CH); 13C NMR (50 MHz, CDCl3):
d
¼22.4, 26.1,
26.2, 29.0, 30.1, 33.7, 120.2, 124.9, 125.3, 138.3; HRMS-ESIþ: found
151.1485. C11H18þHþ requires 151.1488.
19c); 13C NMR (50 MHz, CDCl3):
d¼14.2 (19c and 20a), 17.5
(20a), 21.7 (19c), 25.5 (20a), 30.7 (20a), 31.4 (19c), 60.0 (19c and
20a), 119.0 (20a), 119.3 (19c), 121.0 (20a), 125.4 (19c), 145.1 (19c),
147.6 (20a), 151.0 (19c and 20a), 167.1 (19c and 20a).
4.6.4. 4-Phenylbenzophenone-sensitized irradiation of 14b. Compound
(E)-14b (170 mg, 0.95 mmol) and 4-phenylbenzophenone (255 mg,
0.98 mmol) in CH2Cl2 (160 mL) was irradiated for 20 min. Chroma-
tography (hexane/Et2O 98:2) gave cyclopropylaldehyde (E)-16b4
(160 mg, 94%). Further elution with Et2O afforded 5 mg of highly
polar material.
4.6.6. 4-Phenylbenzophenone-sensitizedirradiationof14c. Compound
(3E,5E)-14c (200 mg, 1.02 mmol) and 4-phenylbenzophenone (1.1 g,
4.25 mmol) in CH2Cl2 (160 mL) was irradiated for 45 min. Chroma-
tography (hexane/Et2O 97:3) gave cyclopropylaldehyde (Ecyclo,ZCeC)-
16c (6 mg, 3%) as a yellow oil and cyclopropylaldehyde 16c (186 mg,
93%) as a 1:4 mixture of (Zcyclo,ECeC/Ecyclo,ECeC) isomers. Further
elution with Et2O afforded 4 mg of highly polar material.
4.6.5. 3-Methoxyacetophenone-sensitized
irradiation
of
14c.
Compound (3E,5E)-14c (200 mg, 1.02 mmol) and 3-methoxy-
acetophenone (1.6 g, 10.6 mmol) in CH2Cl2 (160 mL) was irradiated
for 45 min. Chromatography (hexane/Et2O 97:3) gave a 9:1 mixture
of alkenes (2E,4E)-19c and (E)-20a (7 mg, 4%) as a colorless oil, al-
dehyde (3Z,5E)-14c (21 mg, 10%) as a yellow oil, aldehyde (3E,5E)-
14c (84 mg, 42%), and cyclopropylaldehyde 16c (44 mg, 22%) as
a yellow oil and as a 1:2 mixture of (Zcyclo,ECeC/Ecyclo,ECeC) isomers.
Further elution with Et2O afforded 10 mg of highly polar material.
Compound (3E,5E)-14c (200 mg, 1.02 mmol) and 3-methoxy-
acetophenone (1.6 g, 10.6 mmol) in CH2Cl2 (160 mL) was irradiated
for 120 min. Chromatography (hexane/Et2O 97:3) gave a 6:1 mix-
ture of alkenes (2E,4E)-19c and (E)-20a (21 mg, 12%), aldehyde
(3Z,5E)-14c (4 mg, 2%), aldehyde (3E,5E)-14c (8 mg, 4%), and
4.6.6.1. Compound (Ecyclo,ZCeC)-16c. Found: C, 67.3; H, 8.2.
C11H16O3 requires C, 67.32; H, 8.22%. IR (neat): 2840, 2730, 1740,
1720 cmꢀ1; IR (CHCl3): 2860, 2740, 1710, 1630 cmꢀ1 1H NMR
;
(200 MHz, CDCl3):
d
¼1.18 (s, 3H, CH3), 1.24 (t, J¼7.1 Hz, 3H, CH3),
1.34 (s, 3H, CH3), 1.76 (texp, J¼5.4 Hz, 1H, CH), 3.57e3.64 (m, 1H,
CH), 4.12 (q, J¼7.1 Hz, 2H, CH2O), 5.71e5.85 (m, 2H, CH]CH), 9.28
(d, J¼5.8 Hz,1H, CHO); 13C NMR (50 MHz, CDCl3):
¼14.4, 21.9, 22.2,
d
31.0, 34.1, 46.3, 60.2, 121.5, 145.6, 166.0, 199.5; MS: m/z (%)¼71 (43),
93 (60), 125 (19), 149 (100), 167 (Mþꢀ29, 71); HRMS-ESIþ: found
197.1175. C11H16O3þHþ requires 197.1178.
cyclopropylaldehyde 16c (68 mg, 34%) as
a 1:5 mixture of
(Zcyclo,ECeC/Ecyclo,ECeC) isomers. Further elution with Et2O afforded
4.6.7. 3-Methoxyacetophenone-sensitized
irradiation
of
14d.
50 mg of highly polar material.
Compound (3E,5E)-14d (250 mg, 1.19 mmol) and 3-methoxy-
acetophenone (2 g, 13.3 mmol) in CH2Cl2 (160 mL) was irradiated
for 60 min. Chromatography (hexane/Et2O 97:3) gave a 6:1 mixture
of alkenes (2E,4E)-19d and (E)-20b (21 mg, 10%) as a colorless oil,
alkene (2Z,4E)-19d (18 mg, 8%) as a colorless oil, aldehyde (3E,5E)-
14d (92 mg, 37%), aldehyde (3E,5Z)-14d (46 mg, 28%) as a yellow oil,
and cyclopropylaldehyde 16d (35 mg, 14%) as a yellow oil and as
a 1:5 mixture of (Zcyclo,ECeC/Ecyclo,ECeC) isomers. Further elution
with Et2O afforded 2 mg of highly polar material.
Compound (3E,5E)-14d (250 mg, 1.19 mmol) and 3-methoxy-
acetophenone (2 g, 13.3 mmol) in CH2Cl2 (160 mL) was irradiated
for 120 min. Chromatography (hexane/Et2O 97:3) gave a 5:1 mix-
ture of alkenes (2E,4E)-19d and (E)-20b (18 mg, 8%), alkene (2Z,4E)-
19d (9 mg, 4%), aldehyde (3E,5E)-14d (25 mg, 10%), aldehyde
(3E,5Z)-14d (12 mg, 5%), and cyclopropylaldehyde 16d (12 mg, 5%)
as a 1:2 mixture of (Zcyclo,ECeC/Ecyclo,ECeC) isomers. Further elution
with Et2O afforded 95 mg of highly polar material.
4.6.5.1. Compound (3Z,5E)-14c. Found: C, 67.3; H, 8.2. C11H16O3
requires C, 67.32; H, 8.22%. IR (neat): 2840, 2730, 1740, 1720 cmꢀ1
;
1H NMR (200 MHz, CDCl3):
d
¼1.20 (s, 6H, 2CH3), 1.24 (t, J¼7.2 Hz,
3H, CH3), 4.13 (q, J¼7.2 Hz, 2H, CH2O), 5.62 (d, J¼11.1 Hz, 1H, CH]
CH), 5.93 (d, J¼15.7 Hz, 1H, CH]CHCO2Et), 6.50 (texp, J¼11.1 Hz, 1H,
CH]CH), 7.51e7.37 (ddd, J¼15.7, 11.1, 1.0 Hz, 1H, CH]CHCO2Et),
9.35 (s, 1H, CHO); 13C NMR (50 MHz, CDCl3):
d
¼14.3, 21.4, 49.4, 60.1,
118.2, 127.3, 143.9, 144.2, 166.3, 201.5; MS: m/z (%)¼43 (21), 79 (40),
93 (100), 167 (Mþꢀ29, 93); HRMS-ESIþ: found 197.1176.
C11H16O3þHþ requires 197.1178.
4.6.5.2. Compound(Zcyclo,ECeC/Ecyclo,ECeC)-16c. 1H NMR (200 MHz,
CDCl3):
d
¼1.21 (s, 1H, CH3, Zcyclo,ECeC), 1.22 (t, J¼7.1 Hz, 3H, CH3,
Zcyclo,ECeC and Ecyclo,ECeC), 1.22 (s, 2H, CH3, Ecyclo,ECeC), 1.25 (s,
1H, CH3, Zcyclo,ECeC), 1.36 (s, 2H, CH3, Ecyclo,ECeC), 1.95e2.15 (m,
1.33H, CH, Zcyclo,ECeC and Ecyclo,ECeC), 2.36 (dd, J¼9.9, 5.0 Hz, 0.66H,
CH, Ecyclo,ECeC), 4.11 (q, J¼7.1 Hz, 0.66H, CH2O, Zcyclo,ECeC), 4.12
(q, J¼7.1 Hz, 1.33H, CH2O, Ecyclo,ECeC), 5.91 (d, J¼15.4 Hz, 0.33H, CH]
4.6.7.1. Compound (3E,5Z)-14d. Found: C, 68.5; H, 8.6. C12H18O3
requires C, 68.54; H, 8.63%. IR (neat): 2810, 2707, 1705, 1637 cmꢀ1
;

8696
D. Armesto et al. / Tetrahedron 66 (2010) 8690e8697
1H NMR (200 MHz, CDCl3):
d
¼1.17 (s, 6H, 2 CH3), 1.26 (t, J¼7.1 Hz,
for 45 min. Chromatography (hexane/EtAcO 98:2) gave aldehyde
(3E,5Z)-14e (78 mg, 39%) as a yellow oil, cyclopropylaldehyde
(Ecyclo,ZCeC)-16e (94 mg, 47%) as a yellow oil, and tetraene 21a
(14 mg, 4%) as a yellow oil. Further elution with Et2O afforded 4 mg
of highly polar material.
Compound (3E,5E)-14e (200 mg, 0.9 mmol) and 3-methoxy-
acetophenone (7.1 g, 47.3 mmol) in CH2Cl2 (280 mL) was irradiated
for 90 min. Chromatography (hexane/EtAcO 98:2) gave aldehyde
3H, CH3), 1.90 (br s, 3H, CH3C]C), 4.16 (q, J¼7.1 Hz, 2H, CH2O), 5.74
(d, J¼15.6 Hz, 1H, CH]CH), 6.35 (d, J¼11.0 Hz, 1H, CH]C), 7.17 (dd,
J¼15.6, 11.0 Hz, 1H, CH]CH), 9.32 (s, 1H, CHO); 13C NMR
(50 MHz, CDCl3):
d
¼14.7, 21.1, 21.8, 37.0, 60.8, 126.7, 128.7, 139.6,
140.9, 154.0, 202.1; MS: m/z (%)¼43 (100), 71 (30), 113 (15), 141
(Mþꢀ69, 14); HRMS-ESIþ: found 211.1333. C12H18O3þHþ requires
211.1335.
(3E,5E)-14e
(16 mg,
8%),
cyclopropylaldehyde
(Ecyclo,
4.6.7.2. Compound (Zcyclo,ECeC/Ecyclo,ECeC)-16d. 1H NMR (200 MHz,
ZCeC)-16e (64 mg, 32%), and tetraene 21a (21 mg, 6%). Further
CDCl3):
d¼1.21 (s, 0.5H, CH3, Zcyclo,ECeC), 1.22 (t, J¼7.1 Hz, 2.5H, CH3,
elution with Et2O afforded 75 mg of highly polar material.
Ecyclo,ECeC), 1.22 (s, 2.5H, CH3, Ecyclo,ECeC), 1.23 (t, J¼7.1 Hz, 0.5H, CH3,
Zcyclo,ECeC), 1.28 (s, 2.5H, CH3, Ecyclo,ECeC), 1.37 (s, 0.5H, CH3, Zcyclo,ECeC),
1.86 (d, J¼1.4 Hz, 2.5H, CH3C]C, Ecyclo,ECeC), 1.85e2.00 (m, 1.5H, CH
and CH3C]C, Ecyclo,ECeC and Zcyclo,ECeC), 2.10 (texp, J¼5.1 Hz, 0.166H,
CH, Zcyclo,ECeC), 2.38 (dd, J¼9.6, 5.0 Hz, 0.834H, CH, Ecyclo,ECeC), 4.12
(q, J¼7.1 Hz, 1.66H, CH2O, Ecyclo,ECeC), 4.13 (q, J¼7.1 Hz, 0.33H, CH2O,
Zcyclo,ECeC), 6.39 (dd, J¼9.6, 1.4 Hz, 0.83H, CH]C, Ecyclo,ECeC), 6.93
(dd, J¼9.4,1.5 Hz, 0.166H, CH]C, Zcyclo,ECeC), 9.43 (d, J¼5.8 Hz, 0.166H,
CHO, Zcyclo,ECeC), 9.47 (d, J¼4.5 Hz, 0.83H, CHO, Ecyclo,ECeC); 13C NMR
4.6.9.1. Compound (3E,5Z)-14e. Found: C, 65.1; H, 6.8; N, 6.3.
C12H15NO3 requires C, 65.14; H, 6.83; N, 6.33%. IR (neat): 2814, 2754,
2230, 1728, 1626, 1589 cmꢀ1
;
1H NMR (200 MHz, CDCl3):
d¼1.26
(s, 6H, 2CH3), 1.29 (t, J¼7.1 Hz, 3H, CH3), 4.26 (q, J¼7.1 Hz, 2H, CH2O),
6.40 (d, J¼15.6 Hz, 1H, CH]CH), 7.20 (d, J¼11.3 Hz, 1H, CH]C), 7.54
(dd, J¼15.6,11.3 Hz,1H, CH]CH), 9.38(s,1H, CHO);13C NMR (50 MHz,
CDCl3):
d
¼14.2, 21.4, 50.3, 62.3, 104.5, 116.8, 126.0, 153.4, 156.2, 161.5,
200.5; MS: m/z (%)¼77 (65), 91 (63), 147 (100), 192 (68), 221 (Mþ, 2);
(50 MHz, CDCl3):
d¼13.2 (Zcyclo,ECeC), 13.3 (Ecyclo,ECeC), 14.5
HRMS-ESIþ: found 222.1130. C12H15NO3þHþ requires 222.1131.
(Zcyclo,ECeC), 14.7 (Ecyclo,ECeC), 21.7 (Ecyclo,ECeC), 22.8 (Ecyclo,ECeC), 23.1
(Zcyclo,ECeC), 32.3 (Zcyclo,ECeC), 33.3 (Ecyclo,ECeC), 34.6 (Ecyclo,ECeC), 35.6
(Zcyclo,ECeC), 42.9 (Zcyclo,ECeC), 45.6 (Ecyclo,ECeC), 61.0 (Zcyclo,ECeC and
Ecyclo,ECeC), 130.5 (Ecyclo,ECeC), 131.4 (Zcyclo,ECeC), 135.3 (Zcyclo,ECeC),
144.2 (Ecyclo,ECeC), 167.9 (Zcyclo,ECeC), 168.0 (Ecyclo,ECeC), 199.7
(Ecyclo,ECeC), 200.4 (Zcyclo,ECeC).
4.6.9.2. Compound (Ecyclo,ZCeC)-16e. Found: C, 65.1; H, 6.8; N, 6.3.
C12H15NO3 requires C, 65.14; H, 6.83; N, 6.33%. IR (neat): 2820, 2750,
2230, 1728, 1625 cmꢀ1
;
1H
NMR
(200 MHz,
CDCl3):
d
¼1.28 (t, J¼7.1 Hz, 3H, CH3), 1.30 (s, 3H, CH3), 1.33 (s, 3H, CH3), 2.21
(texp, J¼4.6 Hz, 1H, CH), 2.78 (dd, J¼11.2, 4.7 Hz, 1H, CH), 4.25 (q,
J¼7.1 Hz, 2H, CH2O), 7.22 (d, J¼11.2 Hz, 1H, CH]C), 9.45 (d, J¼4.5 Hz,
1H, CHO); 13C NMR (50 MHz, CDCl3):
d
¼14.1, 21.2, 22.7, 34.9,
4.6.7.3. Compound (2Z,4E)-19d. Found: C, 72.5; H, 9.9. C11H18O2
36.0, 46.6, 62.6, 109.4, 113.6, 159.9, 160.9, 196.7; MS:
m/z (%)¼41 (100), 39 (98), 53 (40), 77 (76), 148 (15), 192 (57), 193
(22); HRMS-ESIþ: found 222.1129. C12H15NO3þHþ requires 222.1131.
requires C, 72.49; H, 9.95%. IR (neat): 1708, 1635 cmꢀ1 1H NMR
;
(200 MHz, CDCl3):
d
¼0.97 (d, J¼6.7 Hz, 6H, CH(CH3)2), 1.25 (t,
J¼7.1 Hz, 3H, CH3), 1.87 (br s, 3H, CH3C]C), 2.30e2.43 (m, 1H, CH
(CH3)2), 4.15 (q, J¼7.1 Hz, 2H, CH2O), 5.80 (dd, J¼15.3, 6.7 Hz,
1H, CH]CH), 6.33 (d, J¼11.2 Hz, 1H, CH]C), 7.01 (dd, J¼15.3,
4.6.9.3. Compound 21a. Found: C, 68.7; H, 7.4; N, 7.1. C22H28N2O4
requires C, 68.73; H, 7.34; N, 7.29%. IR (neat): 2235, 1625, 1589 cmꢀ1
;
11.8 Hz, 1H, CH]CH); 13C NMR (50 MHz, CDCl3):
d¼14.4, 20.7,
1H NMR (200 MHz, CDCl3):
d
¼1.26 (s, 12H, 4CH3), 1.29 (t, J¼7.1 Hz,
22.1, 31.5, 60.2, 124.8, 141.0, 142.0, 148.7, 189.2; MS: m/z(%)¼43
(100), 57 (20), 71 (27), 140 (2), 154 (1), 181 (Mþꢀ7), 182 (Mþ, 2);
HRMS-ESIþ: found 183.1384. C11H18O2þHþ requires 183.1386.
6H, 2CH3), 4.26 (q, J¼7.1 Hz, 4H, 2CH2O), 6.48e6.73 (m, 4H, CH]CH),
7.81 (d, J¼10.2 Hz, 2H, CH]C); 13C NMR (50 MHz, CDCl3):
¼14.2,
d
20.6, 50.3, 62.2, 106.2, 114.0, 125.9, 153.2, 154.7, 161.9; HRMS-ESIþ:
found 385.2125. C22H28N2O4þHþ requires 385.2049.
4.6.7.4. Compounds (2E,4E)-19d and (E)-20b. 1H NMR
(200 MHz, CDCl3):
d
¼0.98 (d, J¼6.7 Hz, 5H, (CH3)2CH, 19d), 1.21
4.6.10. 4-Phenylbenzophenone-sensitizedirradiationof14e. Compound
(3E,5E)-14e (200 mg, 0.9 mmol) and 4-phenylbenzophenone (4.9 g,
18.9 mmol) in CH2Cl2 (160 mL) was irradiated for 45 min. Chroma-
tography (hexane/EtAcO 98:2) gave cyclopropylaldehyde (Ecyclo,ECeC)-
16e (174 mg, 87%) and cyclopropylaldehyde (Zcyclo,ECeC)-16e (16 mg,
8%). Further elution with EtAcO afforded 5 mg of highly polar material.
(t, J¼6.9 Hz, 0.5H, CH3, 20b), 1.22 (t, J¼7.1 Hz, 2.5H, CH3, 19d), 1.57
(br s, 0.5H, CH3C]C, 20b), 1.63 (br s, 0.5H, CH3C]C, 20b), 1.78 (br s,
0.5H, CH3C]C, 20b), 1.86 (d, J¼1.0 Hz, 2.5H, CH3C]C,
19d), 2.28e2.45 (m, 0.83H, CH(CH3)2, 19d), 2.78 (texp, J¼7.3 Hz,
0.33H, CH2, 20b), 4.10 (q, J¼6.9 Hz, 0.33H, CH2O, 20b), 4.12
(q, J¼7.1 Hz, 1.66H, CH2O, 19d), 5.05 (t, J¼7.3 Hz, 0.166H, CH]C
(CH3)2, 20b), 5.97 (dd, J¼15.1, 6.8 Hz, 0.83H, CH]CHCH(CH3)2, 19d),
6.23 (ddd, J¼15.1, 11.0, 0.9 Hz, 0.83H, CH]CHCH(CH3)2, 19d), 6.63
(td, J¼7.5, 1.4 Hz, 0.166H, CH]CCO2Et, 20b), 7.09 (d, J¼11.0 Hz,
4.6.11. 3-Methoxyacetophenone-sensitized irradiation of 14f.
Compound (E)-14f (200 mg, 1.15 mmol) and 3-methoxy-
acetophenone (7.4 g, 49.3 mmol) in CH2Cl2 (160 mL) was irradiated
for 60 min. Chromatography (hexane/Et2O 8:2) gave aldehyde (E)-
14f (68 mg, 34%), cyclopropylaldehyde (Z)-16f (26 mg, 13%) as
a yellow oil, cyclopropylaldehyde (E)-16f (42 mg, 21%) as a yellow
oil, and tetraene (4E,8E)-21b (15 mg, 4%) as a yellow oil. Further
elution with Et2O afforded 21 mg of highly polar material.
Compound (E)-14f (200 mg, 1.15 mmol) and 3-methoxy-
acetophenone (7.4 g, 49.3 mmol) in CH2Cl2 (160 mL) was irradiated
for 120 min. Chromatography (hexane/Et2O 8:2) gave aldehyde (E)-
14f (18 mg, 9%), cyclopropylaldehyde (Z)-16f (20 mg, 10%), cyclo-
propylaldehyde (E)-16f (40 mg, 20%), and tetraene (4E,8E)-21b
(26 mg, 7%). Further elution with Et2O afforded 60 mg of highly
polar material.
0.83H, CH]C, 19d); 13C NMR (50 MHz, CDCl3):
d
¼12.4 (20b), 12.6
(19d), 14.4 (19d and 20b), 17.9 (20b), 22.1 (19d), 25.7 (20b), 27.9
(20b), 31.9 (19d), 60.5 (19d), 64.2 (20b), 120.4 (19d and 20b), 123.1,
125.4, 138.8, 140.6, 140.8, 149.8, 168.7 (19d and 20b).
4.6.8. 4-Phenylbenzophenone-sensitizedirradiationof14d. Compound
(3E,5E)-14d (83 mg, 1.02 mmol) and 4-phenylbenzophenone (80 mg,
0.31 mmol) in CH2Cl2 (160 mL) was irradiated for 60 min. Chroma-
tography (hexane/Et2O 97:3) gave cyclopropylaldehyde 16d (76 mg,
92%) as a 1:5 mixture of (Zcyclo,ECeC/Ecyclo,ECeC) isomers. Further elu-
tion with Et2O afforded 5 mg of highly polar material.
4.6.9. 3-Methoxyacetophenone-sensitized
irradiation
of
14e.
Compound (3E,5E)-14e (200 mg, 0.9 mmol) and 3-methoxy-
4.6.11.1. Compound (Z)-16f. Found: C, 68.9; H, 5.8; N, 16.1.
acetophenone (7.1 g, 47.3 mmol) in CH2Cl2 (280 mL) was irradiated
C10H10N2O requires C, 68.95; H, 5.79; N,16.08%. IR (neat): 2854, 2744,

D. Armesto et al. / Tetrahedron 66 (2010) 8690e8697
8697
2235, 1709, 1595 cmꢀ1
;
1H NMR (200 MHz, CDCl3):
d
¼1.27 (s, 3H,
Chromatography (hexane/Et2O 97:3) gave (E)-1-(2-methyl-
propylidene)-1H-indene (105 mg, 62%) as a colorless oil. Further
elution with Et2O afforded 15 mg of highly polar material. Found: C,
91.7; H, 8.3. C13H14 requires C, 91.71; H, 8.29%. IR (neat): 1640,
CH3), 1.36 (s, 3H, CH3), 2.47 (dd, J¼11.0, 7.8 Hz, 1H, CH), 2.71 (dd,
J¼7.8, 1.8 Hz, 1H, CH), 7.77 (d, J¼11.0 Hz,1H, CH]C), 9.82 (d, J¼1.8 Hz,
1H, CHO); 13C NMR (50 MHz, CDCl3):
d¼14.9, 28.3, 36.8, 38.4, 45.9,
87.9, 111.2, 112.3, 165.0, 197.3; MS: m/z (%)¼39 (100), 43 (40), 77 (48),
119 (72), 145 (33), 146 (14), 156 (11), 173 (Mþꢀ1, 3); HRMS-ESIþ:
found 175.0870. C10H10N2OþHþ requires 175.0872.
1610 cmꢀ1; 1H NMR (200 MHz, CDCl3):
d¼0.94 (d, J¼6.8 Hz, 6H, CH
(CH3)2), 2.18e2.35 (m, 1H, CH(CH3)2), 6.44 (d, J¼5.7 Hz, 1H, indene),
6.57 (d, J¼10.7 Hz, CH]C), 6.80 (m, 1H, indene), 7.06e7.21 (m, 3H,
indene), 7.43e7.49 (m, 1H, indene); 13C NMR (50 MHz, CDCl3):
4.6.11.2. Compound (E)-16f. Found: C, 68.9; H, 5.8; N, 16.1.
C10H10N2O requires C, 68.95; H, 5.79; N, 16.08%. IR (neat): 2854,
d
¼22.5, 31.2, 119.1, 121.1, 125.0, 125.6, 128.0, 132.1, 135.2, 137.0, 141.7,
142.0; HRMS-ESIþ: found 171.1083. C13H14þHþ requires 171.1085.
2744, 2235, 1709, 1595 cmꢀ1
;
1H NMR (200 MHz, CDCl3):
d
¼1.32
(s, 3H, CH3), 1.34 (s, 3H, CH3), 2.33 (dd, J¼4.8, 3.7 Hz, 1H, CH), 2.97
(dd, J¼11.2, 4.8 Hz, 1H, CH), 6.86 (d, J¼11.2 Hz, 1H, CH]C), 9.52 (d,
Acknowledgements
J¼3.7 Hz, 1H, CHO); 13C NMR (50 MHz, CDCl3):
¼20.7, 22.6, 35.9,
d
38.4, 46.9, 88.6, 111.2, 112.5, 165.6, 195.6; MS: m/z (%)¼39 (100), 43
We thank the Spanish Ministerio de Ciencia e Innovación
(MICINN, CTQ2008-02820) and the Universidad Complutense de
Madrid (Grant No. GR58/08) for financial support. We acknowledge
the support provided by the Centro de Resonancia Magnetica Nu-
clear and the Centro de Microanálisis of the Universidad Complu-
tense de Madrid.
(36), 77 (40), 119 (76), 145 (35), 173 (Mþꢀ1, 5).
4.6.11.3. Compound 21b. Found: C, 74.4; H, 6.4; N,19.2. C18H18N4
requires C, 74.46; H, 6.25; N, 19.29%. IR (neat): 2110, 1630 cmꢀ1; 1H
NMR (200 MHz, CDCl3):
d
¼1.34 (s, 12H, 4CH3), 6.61 (d, J¼15.0 Hz,
2H, 2CH]CH), 6.76 (dd, J¼15.0, 11.1 Hz, 2H, 2CH]CH), 7.42 (d,
J¼11.1 Hz, 2H, 2CH]C); 13C NMR (50 MHz, CDCl3):
¼29.4, 42.9,
d
84.9, 111.2, 113.5, 122.2, 160.8, 161.8; HRMS-ESIþ: found 291.1607.
C18H18N4þHþ requires 291.1610.
Supplementary data
These data include copies of 1H NMR spectra for all new com-
pounds. Supplementary data associated with this article can be
found in the online version, at doi:10.1016/j.tet.2010.09.012. These
data include MOL files and InChIKeys of the most important com-
pounds described in this article.
4.6.12. 4-Phenylbenzophenone-sensitized irradiation of 14f. Compound
(E)-14f (200 mg, 1.15 mmol) and 4-phenylbenzophenone (5.2 g,
20.1 mmol) in CH2Cl2 (160 mL) was irradiated for 60 min. Chroma-
tography (hexane/Et2O 8:2) gave cyclopropylaldehyde (Z)-16f (49 mg,
27%) and cyclopropylaldehyde (E)-16f (112 mg, 66%). Further elution
with Et2O afforded 5 mg of highly polar material.
4.6.13. 3-Methoxyacetophenone-sensitized irradiation of 15.
Compound (E)-15 (200 mg, 1.1 mmol) and 3-methoxyaceto-
phenone (4.8 g, 32.0 mmol) in CH2Cl2 (270 mL) was irradiated for
180 min. Chromatography (hexane/Et2O 97:3) gave aldehyde 15
References and notes
1. (a) Naumann, K. In Chemistry of Plant Protection 4, Synthetic Pyrethroid In-
secticides: Structures and Properties; Haug, G., Hoffmann, H., Eds.; Springer:
Berlin, 1990; (b) Naumann, K. In Chemistry of Plant Protection 5, Synthetic Py-
rethroid Insecticides: Chemistry and Patents; Haug, G., Hoffmann, H., Eds.;
Springer: Berlin, 1990; (c) Bloomquist, J. R. Rev. Pestic. Toxicol. 1993, 2, 185e226;
(d) Ware, G. W.; Whitacre, D. M. The Pesticide Book, 6th ed.; Meister Media
Worldwide: Willoughby, OH, 2004.
(38 mg, 19%) as
a 1:1 mixture of E/Z isomers and cyclo-
propylaldehyde 174 (124 mg, 62%) as a 6:1 mixture of E/Z isomers.
Further elution with Et2O afforded 30 mg of highly polar material.
Compound (E)-15 (220 mg, 1.1 mmol) and 3-methoxy-
acetophenone (4,8 g, 32.0 mmol) in CH2Cl2 (270 mL) was irradiated
for 300 min. Chromatography (hexane/Et2O 97:3) gave aldehyde
(E)-15 (7 mg, 3%) and cyclopropylaldehyde 17 (84 mg, 40%) as a 9:1
mixture of E/Z isomers. Further elution with Et2O afforded 67 mg of
highly polar material.
2. Storck, W. J. Chem. Eng. News 1987, 65, 11e16.
3. Arlt, D.; Jautelat, M.; Lantzsch, R. Angew. Chem., Int. Ed. Engl. 1981, 20, 703e722.
4. Armesto, D.; Gallego, M. G.; Horspool, W. M.; Agarrabeitia, A. R. Tetrahedron
1995, 51, 9223e9240.
5. Armesto, D.; Gallego, M. G.; Horspool, W. M.; Bermejo, F. Patent ES 9100648,
1991. Armesto, D.; Gallego, M. G.; Horspool, W. M.; Bermejo, F. WO 92/16499
Patent PCT/ES92/00017, 1992.
6. Armesto, D.; Ortiz, M. J.; Romano, S.; Agarrabeitia, A. R.; Gallego, M. G.; Ramos,
A. J. Org. Chem. 1996, 61, 1459e1466.
7. Armesto, D.; Ortiz, M. J.; Agarrabeitia, A. R.; El-Boulifi, N. Angew. Chem., Int. Ed.
2005, 44, 7739e7741.
8. Armesto, D.; Ortiz, M. J.; Agarrabeitia, A. R.; Martin-Fontecha, M.; El-Boulifi, N.;
Duran-Sampedro, G.; Enma, D. Org. Lett. 2009, 11, 4148e4151.
9. Murov, S. L.; Carmichael, I.; Hug, G. L. Handbook of Photochemistry, 2nd ed.;
Marcel Dekker: New York, NY, 1993.
10. Armesto, D.; Ortiz, M. J.; Agarrabeitia, A. R.; Aparicio-Lara, S. Synthesis 2001,
1149e1158.
4.6.14. 4-Phenylbenzophenone-sensitized irradiation of 15. Compound
(E)-15 (200 mg, 1.0 mmol) and 4-phenylbenzophenone (2.9 g,
11.2 mmol) in CH2Cl2 (160 mL) was irradiated for 180 min. Chroma-
tography (hexane/Et2O 97:3) gave cyclopropylaldehyde 17 (190 mg,
95%) as a 6:1 mixture of E/Z isomers. Further elution with Et2O
afforded 5 mg of highly polar material.
11. Johnston, D.; Mc Cusker, C. F.; Muir, K.; Procter, D. J. J. Chem. Soc., Perkin Trans. 1
4.6.15. Direct irradiation of 15. Compound (E)-15 (200 mg,
2000, 681e695.
1.0 mmol) in CH2Cl2 (160 mL) was irradiated for 180 min.
12. Vedejs, E.; Fuchs, P. L. J. Org. Chem. 1971, 36, 366e367.