The reactions of α-ylidene (vinylidene, benzylidene, styrylmethylidene) bis[carbonyls] with copper mono/bis[carbonylcarbenoids]

Article abstract of DOI:10.1002/hlca.201200004

The [Cu(acac)₂]-catalyzed reactions of various α,β,γ,δ-unsaturated bis-ketones/bis-esters/bis-keto esters with dimethyl diazomalonate and ethyl diazoacetate were studied. Total steric/electronic convenience of the present reaction paths was inv

Full text of DOI:10.1002/hlca.201200004

Helvetica Chimica Acta – Vol. 95 (2012)
1409
The Reactions of a-Ylidene (Vinylidene, Benzylidene, Styrylmethylidene)
Bis[carbonyls] with Copper Mono/Bis[carbonylcarbenoids]
by GçkÅe Merey*, Mustafa Kaya, and Olcay AnaÅ*
Istanbul Technical University, Faculty of Science and Letters, Department of Chemistry, 34460 Maslak,
TR-Istanbul (phone: þ 90-212-2853229; fax: þ 90-212-2856386; e-mail: anac@itu.edu.tr)
The [Cu(acac)2]-catalyzed reactions of various a,b,g,d-unsaturated bis-ketones/bis-esters/bis-keto
esters with dimethyl diazomalonate and ethyl diazoacetate were studied. Total steric/electronic
convenience of the present reaction paths was investigated. Methoxy/nitro substituents in m-/p-positions
on benzylidene biscarbonyls did not alter the general routes of the reactions, supporting concerted
mechanism. Dihydrobenzoxepine/oxepine formation was sterically sensitive to the related pre-ring
conformation, and dihydrofurans were effected by both charge control and steric factors.
Introduction. – The metal-catalyzed reactions of diazo compounds became
promising for a diverse array of transformations with the advent of new catalysts.
The recognition of different classes of carbenoids can open up new vistas of reactivity,
moreover, there are still several attempts to react new substrates with old-generation
metallocarbenes to investigate reaction probabilities with/without stereochemical
concern [1 – 15].
We recently reported the reactions of (dimethoxycarbonylcarbenoid)copper(II)
with anilino derivatives of tert-enaminophenones [16] and a,b-unsaturated carbox-
amides [17]. In both studies, the conjugated carbonyl compounds offered three reaction
sites (N, C(a), and O) for attack by electrophiles, beside carbenoid additions to the
present double bonds, and several novel derivatives were obtained.
We also reported the (dimethoxycarbonylcarbenoid)copper(II) reactions of 2-
vinylidene-/benzylidene mono/bis-ketones/esters [18] as pilot studies. In the reactions
with 2-benzylidene monoketones/esters [18b], we did not observe any dihydrobenzox-
epine derivative by a 1,7-electrocyclization from the related conjugated carbonyl ylides
because of the restricted rotation around the double bond which hindered the
necessary pre-ring conformation. In these reactions, we only found dihydrofurans, and
its derivatives such as furofuran and b-vinylic dimethyl malonyl compounds. However,
dihydrobenzoxepine formation by 1,7-electrocyclization was observed almost equal to
dihydrofuran formation by 1,5-electrocyclization, when we investigated the reaction of
2-benzylidene-1,3-bisketones and bisketoesters [18c] with dimethyl diazomalonate. It
should be mentioned that various researchers obtained either cyclopropanes
[4a][19][20] or different products under similar conditions.
Considering that the factors controlling the chemoselectivity were more subtle than
thought, we planned to extend this chemistry to more elaborate systems. Accordingly,
we decided to conduct a systematic study to better understand the controlling factors
ꢀ 2012 Verlag Helvetica Chimica Acta AG, Zꢁrich

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behind the selectivity of this chemistry, which would allow a broader application of this
methodology in total synthesis.
Results and Discussion. – In this study, several different substituted ene-
biscarbonyls, 11a – 11t, were reacted with two different diazo carbonyl compounds,
dimethyl diazomalonate (12) and ethyl diazoacetate (13), in the presence of
[Cu(acac)2] catalyst (Scheme 1). As the chemoselectivity problem has been a recurrent
theme on transition metal-catalyzed carbene-transfer reactions over the last three
decades, we aimed to search for the formation of dihydrofuran 14, dihydrobenzox-
epines 15, dihydrooxepines 16, and probably dihydrobenzooxonine derivatives 17 by
1,5-/1,7-, and perhaps 1,9-electrocyclic reactions beside other possible reaction path-
ways.
Scheme 1
The results are compiled in the Table, the related mechanisms are outlined in
Scheme 2.
Scheme 2
In the first series of experiments, we studied both the electronic and steric effects of
the ene-biscarbonyl structure on the chemoselectivity of the reaction. First, we used
benzylidene and m-/p-MeO/NO2 benzylidene-bis[phenyl ketones] 11a – 11d in the
reaction with dimethyl diazomalonate (12). With these bulky ene-diones, reactions
were so clean that only dihydrofuran derivatives 14a12 – 14d12 were obtained. Addi-

Helvetica Chimica Acta – Vol. 95 (2012)
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Table. Product Distrubition of CuII-Catalyzed Reactions of Conjugated Biscarbonyls with Diazo-
biscarbonyls
Entry
11
R1
R2
R3
Diazo compound
14/15 or 14/16
1
2
3
4
5
6
7
8
9
a
b
c
d
e
f
g
h
i
j
k
l
m
n
o
p
q
r
Ph
Ph
Ph
Ph
Ph
Me
Me
Me
Me
Ph
Ph
Ph
Ph
12
12
12
12
12
12
12
12
12
12
12
12
12
12
12
12
12
12
12
12
13
13
13
13
13
13
13
13
13
13
13
13
13
13
13
13
13
13
13
13
100 : 0
100 : 0
100 : 0
100 : 0
3-MeOꢀC6H4
4-MeOꢀC6H4
3-NO2ꢀC6H4
PhꢀCH¼CH
Ph
3-MeOꢀC6H4
4-MeOꢀC6H4
3-NO2ꢀC6H4
4-NO2ꢀC6H4
Ph
3-NO2ꢀC6H4
4-NO2ꢀC6H4
PhꢀCH¼CH
Ph
3-MeOꢀC6H4
3-NO2ꢀC6H4
4-NO2ꢀC6H4
PhꢀCH¼CH
Me
Me
Me
Me
Me
Me
Me
Me
Me
Me
Me
EtO
EtO
EtO
EtO
EtO
EtO
Ph
76 : 24
40 : 60 [18c]
40 : 60a)
44 : 56
29 : 71a)
38 : 62
50 : 50 [18c]
47: 53a)
43 : 57
55 : 45
100 : 0 [18b]
100 : 0
100 : 0
100 : 0
Me
Me
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
EtO
EtO
EtO
EtO
EtO
EtO
EtO
EtO
EtO
EtO
Ph
Ph
Ph
Ph
Me
Me
Me
Me
Me
s
t
100 : 0
N/Ab)
N/Ab)
N/Ab)
N/Ab)
N/Ab)
58 : 42
a
b
c
d
e
f
g
h
i
j
k
l
m
n
o
p
q
r
Ph
3-MeOꢀC6H4
4-MeOꢀC6H4
3-NO2ꢀC6H4
PhꢀCH¼CH
Ph
3-MeOꢀC6H4
4-MeOꢀC6H4
3-NO2ꢀC6H4
4-NO2ꢀC6H4
Ph
3-NO2ꢀC6H4
4-NO2ꢀC6H4
PhꢀCH¼CH
Ph
3-MeOꢀC6H4
3-NO2ꢀC6H4
4-NO2ꢀC6H4
PhꢀCH¼CH
Me
Ph
Ph
Ph
Me
Me
Me
Me
Me
Me
Me
Me
Me
Me
EtO
EtO
EtO
EtO
EtO
EtO
63 : 37
62 : 38a)
59 : 41
58 : 42
53 : 47
60 : 40
55 : 45
58 : 42
Me
EtO
EtO
EtO
EtO
EtO
EtO
EtO
EtO
EtO
EtO
74 : 26a)
N/Ab)
N/Ab)
N/Ab)
N/Ab)
N/Ab)
N/Ab)
s
t
a) Compound 15 was obtained as a 1 : 1 mixture of stereoisomers. b) N/A: Not available.
tional resonance caused by carbonyl-phenyl rings stabilized completely the pre-ring
carbonyl-ylide structure 18 for a 1,5-dipole (Scheme 3). Moreover, the configuration of
a Cu-associated carbonyl ylide intermediate 18-1 might be responsible for this excellent
chemoselectivity leading to only dihydrofuran formation 14a12 – 14d12. m-/p-MeO/NO2

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Helvetica Chimica Acta – Vol. 95 (2012)
Scheme 3
Substituents on phenyl ring did not alter these preferences. In contrast to the steric
conformity in the hypothetic model 18-1 for dihydrofuran formation, the steric
hindrance in the hypothetic model 18-2 caused by phenyl groups presumably prevented
a 1,7-electrocyclization to yield dihydrobenzoxepines.
We needed additional data to explain the excess formation of dihydrobenzoxepine
15f12 in our previous study [18c] with benzylidene acetone and dimethyl diazomalonate.
Therefore, a series of benzylidene-bisacetyls 11f – 11j and benzylidene-bis[keto esters]
11k – 11m were reacted with dimethyl diazomalonate (12). With the exception of 11k,
which gave equal amounts of 14 and 15, all reactions yielded the corresponding
dihydrofurans 14 and dihydrobenzoxepines 15 in favor of 15. This preference might be
explained rather by the orbital coefficients of the 1,7-dipole, which are smaller (less
centralized) than those of the 1,5-dipole. These results supported the reports [20][21],
which indicated the preference of 1,7-ring closures because of the larger orbital
coefficients at the termini of the conjugated system involving 8p electrons (Scheme 2).
It is also of interest to note that two different 1,7-ring closures occurred in the case
of m-methoxy- and m-nitrobenzylidene biscarbonyls 11g, 11i, and 11l due to the
presence of two possible positions. The ratio of these two 1,7-cyclization products was
almost 1:1, showing no selectivity despite the presence of electron-donating/
withdrawing groups. This result also supported a concerted mechanism [22 – 24] for a
1,7-electrocyclization reaction of the corresponding conjugated carbonyl-ylide, thus
questioning the argument of charge control in chemo-/regioselectivity to a certain
extent.
In the experiments with conjugated bis[keto esters] 11k – 11n, an additional
chemoselectivity on ketone or ester carbonyls was observed1). Our previous result
concerning the reaction of 11k [11], and the novel results with 11l – 11n showed that 1,7-
electrocyclizations took place only from ketone sides and 1,5-electrocyclizations only
from ester sides. Being analogous to the resonance stability of 18, the O-atom of the
ester alkoxy group might facilitate the centralization of 1,5-dipole as shown on the
intermediate conjugated ester ylide 19 (Scheme 4). In addition to the availability of
more centralized charge-controlled structure with respect to ester 19 (R2 ¼ Me), the
1
)
The available rotation around formal C¼C bonds allows either keto or ester function to adopt pre-
ring 1,5-/1,7-conformations in these fully conjugated, highly polarized bis[keto esters] under our
experimental conditions.

Helvetica Chimica Acta – Vol. 95 (2012)
1413
hypothetical model 19-1 also showed that 1,5-cyclization was sterically more attractive
in the case of ester carbonyl ylide than 1,7-cyclizations via 19-2 or 19-3 (Scheme 4).
Scheme 4
By the same approach, the expanded conjugation/charge control over styrylme-
thylidene/benzylidene was more feasible on the intermediate conjugated keto-ylides
20/21 (Scheme 5, R2 ¼ EtO) derived from the keto side of the related bis[keto ester].
Predictive Cu-associated carbonyl ylide intermediate models 20-1/21-1, derived from
the keto- carbonyl-ylide side, for 1,7-cyclizations were also sterically feasible. It was
also noticed that m-/p-NO2 substituents on phenyl ring did not change the preferences
apparently in the reactions with ene-bis[keto esters].
Scheme 5
On the other hand, in the reactions of styrylmethylidene-bis[carbonyls] 11e, 11n,
and 11s, the chemoselectivity was reversed in favor of the corresponding dihydrofurans
in comparison to benzylidene-bis[carbonyls] 11f – 11m [18c]. It should be remembered
that sb–g bonds of styrylmethylidene-bis[carbonyls] are mainly transoid thus causing
less dihydrooxepine formation, while sb–g bonds of benzylidene-bis[carbonyls] are
certainly cisoid giving rise to dihydrobenzoxepines. Furthermore, hypothetic model 20-
1, for the related 1,7-cyclizations from benzylidene-bis[carbonyls], was sterically more
available than 21-1 from styrylmethylidene-bis[carbonyls]. As a result, in the reaction

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Helvetica Chimica Acta – Vol. 95 (2012)
of 11e, 11n, and 11s, dihydrofuran formation was preferred over dihydrooxepine
formation.
To check if any dihydrooxepine was formed from an ester side, conjugated diesters
11p – 11s were reacted with dimethyl diazomalonate (12), similarly to our recent
reaction with diethyl benzylidenediester (11o) [18c]. All reactions yielded only the
corresponding dihydrofuran derivatives 14o12 – 14s12 because of the restricted expan-
sion of conjugation/orbital system (model 19) similar to benzylidene bis[phenyl
ketones] (model 18).
Although a vinylidene mono ester (ethyl crotonate) yielded dihydrofuran
derivatives [18b], ethylidenebis[ester] 11t did not yield any distinguishable product
in the mixture of products. This result emphasized the inadequacy of a b-alkyl group in
conjugated diesters for a 1,5-dipole generation.
As known, electrocyclization of a conjugated carbonyl ylide is a process that starts
with a carbenoid formation derived from the corresponding diazo decomposition by
catalysis. At this step, diazoacetates are known as more reactive species than
diazomalonates [25]. The next step is the generation of a metal-conjugated carbonyl
ylide from metallocarbene and substrate. In this second step, steric effects based on
conformational influences of both ene-carbonyl, and carbene and ligated catalyst may
be superior to the present electronic influences. So, in each reaction, the neat
periselectivity may be a balance between individual electronic and steric factors within
the related metal-conjugated carbonyl-ylide intermediates.
The next series of reactions were conducted to determine the effect of diazo
substituents on the course of the reaction. In other words, we tried to find out whether
sterically more crowded diazo conformers provided higher periselectivity. Therefore,
ethyl diazoacetate (13) was also used as carbenoid source to determine its chemo/
stereoselectivities on the formation of dihydrofuran and dihydrobenzoxepine.
In the reactions of 11a – 11d (conjugated bis[phenyl ketones]) with 13, no reaction
product could be determined because of the steric mismatch of the related intermediate
containing bisphenyls and ethyl ester groups all together. On the other hand, in the
reactions of 11e – 11k (benzylidene bis[ketones/keto esters]) and 11n (styrymethyli-
dene-bis[keto ester]) with 13, reactions were so rapid that formal poly-adducts were
also found in appreciable amounts close to those of dihydrofurans and small amounts of
dihydrobenzoxepines. But, in the reactions with 11l and 11m, m-/p-NO2 groups of the
phenyl part in benzylidene bis[keto esters], sterically inhibited poly-adduct formation
and gave the best results with respect to formal [1 þ 1] products.
The reactions of 11o – 11s (conjugated bis[diethyl esters]) with ethyl diazoacetate
(13) led to no product at all. These results demonstrated that the total steric consistency
of the related intermediate metallo-conjugated carbonyl ylide was dominant for the
subsequent electrocyclizations: if the global steric consistency was proper, related
metallo-conjugated carbonyl ylides from diazoacetates are more suitable species for
dihydrofuran formation, when compared with those from diazomalonates. As a result,
in the reactions of 11e – 11n, periselectivity was reversed in favor of dihydrofuran
formation in comparison to dihydrobenzoxepines.
Finally, styrylmethylidene-bis[carbonyls] having certainly cisoid sd–e bonds did not
yield any 1,9-electrocyclization products even in minor amounts. As known, rings with
nine members are notoriously difficult to construct.

Helvetica Chimica Acta – Vol. 95 (2012)
1415
Conclusions. – In conclusion, we have broadened the scope of the reactions with
conjugated bisketones/conjugated bisesters/conjugated bis[keto esters] and dimethyl
diazomalonate/ethyl diazocetate to obtain dihydrofuran and dihydrobenzoxepine/
dihydrooxepine derivatives by 1,5-/1,7-electrocyclic reactions of related conjugated
carbonyl ylides with the absence of any 1,9-electrocyclic product. The steric/electronic
structures of both ene-bis[carbonyls] and diazo compounds had significant effects on
the regioselectivities of these two pericyclic reactions in the presence of [Cu(acac)2]:
dihydrobenzoxepine/oxepine formation was sterically more sensitive to the related pre-
ring conformation. On the other hand, dihydrofurans were more effected by the 1,5-
charge control of the related ylides.
All reactions with dimethyl diazomalonate yielded products from different
periselectivity. Benzylidene-bis[phenylketones] and bis-esters gave only dihydrofurans
because of the steric/electronic effects. Additionally, chemospecificity was determined
between keto and ester sides of conjugated bis[keto esters] due to both charge control
and steric availability of hypothetic Cu-associated carbonyl-ylide intermediate.
Consequently, dihydrooxepines/dihydrobenzoxepines were derived only from ketone
reactants, and dihydrofurans only from ester reactants. While reactions with
benzylidene conjugated bis[keto ester]/conjugated bis-ketones preferably lead to
dihydrobenzoxepines, the reactions with styrylmethylidene conjugated bis[keto ester]/
conjugated bis-ketone afford dihydrofurans. The presence of m-/p-MeO/NO2 sub-
stituents on benzylidene-bis[carbonyls] did not sterically/electronically effect the
general routes of the reactions, in supporting a concerted mechanism.
The EtO group of ethyl diazoacetate was sterically less convenient together with the
crowded phenyl/ethyl ester groups of the studied ene-carbonyls, especially for the
formation of dihydrobenzoxepines. Just the contrary is true, if ene-carbonyls were
sterically proper, the more reactive diazo-acetate increased the reaction rate. So,
benzylidene-bis[phenyl ketones] and bis-esters inhibited all the reaction pathways with
ethyl diazoacetate. But, benzylidene/styrylmethylidene-bis[keto esters] underwent
rapid reactions.
These new results with several different types of substrates and two diazo
compounds support our recent reports. Our conditions are appearently different from
those of recent results of Tang and co-workers [21]. They neither identified any product
over substrateꢂs ester function nor argued the absence the related products by DFT
calculations in their study with the unique model of a-benzylidene-b-dicarbonyl and
2,6-diisopropylphenyl diazoacetate, changing benzylidene substituents, catalyst, and
ligands (Scheme 6).
Scheme 6

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Helvetica Chimica Acta – Vol. 95 (2012)
The authors thank the Istanbul Technical University Research Fund (No. 33340).
Experimental Part
General. M.p.: Gallenkamp apparatus; uncorrected. IR Spectra: Perkin-Elmer Spectrum One; ˜n in
cmꢀ1. 1H- and 13C-NMR spectra: Varian Unity INOVA 500 and Bruker AC 250; d in ppm rel. to Me4Si as
internal standard, J in Hz. GC/MS: 6890 Hewlett-Packard GC instrument, with HP-1 cap. column (24 m)
packed with cross-linked (phenylmethyl)siloxane; 5973 HP mass dedector; column temp. program:
isothermal at 1008 for 5 min, heating to 2908 with ramp of 208/min and staying isothermal for 10 min; tR in
min; in m/z (rel. %). HR-EI-MS: JEOL AccuTOF-CS (ESI pos., needle voltage 1800 – 2400 eV); in m/z.
General Procedure for the Synthesis of Starting Bis[carbonyls] 11a – 11t. All bis[carbonyl]
compounds were prepared according to literature procedure [26]. Dicarbonyl starting materials
(0.03 mol) were used in each reaction.
2-Benzylidene-1,3-diphenylpropane-1,3-dione (11a). Yield: 89% (8.3 g). Dark yellow solid. M.p. 878.
IR (neat): 3044, 2927, 1598, 1530, 1220, 748. 1H-NMR (250 MHz, CDCl3): 8.02 – 7.94 (m, 2 H); 7.92 – 7.83
(m, 2 H); 7.61 – 7.22 (m, 12 H). 13C-NMR (125 MHz, CDCl3): 192.1; 185.5; 148.0; 136.2; 135.3; 134.2;
133.5 (2 C); 132.3 (2 C); 130.0 (2 C); 129.5 (2 C); 128.8 (2 C); 128.6 (2 C); 128.5 (2 C); 126.9 (2 C). GC/
MS: tR 16.16. EI-MS: 312 (51, Mþ), 284 (43), 267 (2), 233 (1), 207 (71), 178 (20), 129 (7), 105 (100), 77
(84), 51 (14). HR-EI-MS: 312.3612 (Mþ, C22H16O2þ ; calc. 312.1150).
2-(3-Methoxybenzylidene)-1,3-diphenylpropane-1,3-dione (11b). Yield: 92% (9.4 g). Yellow oil. IR
1
(neat): 1707, 1505, 1272, 1098. H-NMR (250 MHz, CDCl3): 7.98 (d, J ¼ 7.7, 2 H); 7.87 (d, J ¼ 7.6, 2 H);
7.69 – 7.22 (m, 8 H); 7.13 (t, J ¼ 7.8, 1 H); 6.94 – 6.79 (m, 2 H); 3.59 (s, 3 H). 13C-NMR (125 MHz, CDCl3):
191.5; 190.8; 161.0; 145.7; 138.2; 137.9; 135.4; 134.6; 134.4; 132.1; 129.5 (2 C); 129.3; 129.1; 128.7; 128.6
(2 C); 128.3; 128.1; 119.5; 112.5; 111.7; 57.2. GC/MS: tR 17.55. EI-MS: 342 (86, Mþ), 311 (49), 283 (8), 237
(78), 235 (5), 212 (34), 207 (15), 165 (17), 139 (4), 107 (5), 105 (100), 77 (93), 51 (15). HR-EI-MS:
342.3872 (Mþ, C23H18Oþ3 ; calc. 342.1256).
2-(4-Methoxybenzylidene)-1,3-diphenylpropane-1,3-dione (11c). Yield: 85% (8.7 g). Dark yellow
oil. IR (neat): 1676, 1610, 1231, 1026. 1H-NMR (250 MHz, CDCl3): 7.99 (d, J ¼ 7.3, 2 H); 7.82 (d, J ¼ 7.0,
2 H); 7.55 – 7.36 (m, 7 H); 7.28 (d, J ¼ 8.6, 2 H); 6.73 (d, J ¼ 8.6, 2 H); 3.70 (s, 3 H). 13C-NMR (125 MHz,
CDCl3): 191.7; 191.2; 160.7; 143.9; 138.3; 137.9; 135.7; 134.6; 134.1; 132.0; 129.7; 129.6; 129.3; 129.1; 128.7;
128.6 (2 C); 128.3; 128.1; 125.4; 113.7; 112.7; 55.8. GC/MS: tR 18.36. EI-MS: 342 (50, Mþ), 313 (9), 283
(3), 265 (1), 237 (77), 206 (16), 165 (13), 139 (1), 105 (100), 77 (75), 51 (9). HR-EI-MS: 342.3874 (Mþ,
C23H18Oþ3 ; calc. 342.1256).
2-(4-Nitrobenzylidene)-1,3-diphenylpropane-1,3-dione (11d). Yield: 96% (10.3 g). Yellow solid. M.p.
1008. IR (neat): 3059, 1669, 1263, 733. 1H-NMR (CDCl3, 250 MHz): 8.09 (d, J ¼ 8.7, 2 H); 7.92 (t, J ¼ 8.0,
4 H); 7.64 – 7.39 (m, 9 H). 13C-NMR (125 MHz, CDCl3): 191.3; 190.8; 147.2; 138.2; 137.9; 135.4; 134.6;
134.4; 134.1; 129.5; 129.3 (2 C); 129.1; 128.7 (2 C); 128.4 (2 C); 128.3 (2 C); 128.1; 123.5; 122.9. GC/MS:
tR 17.54. EI-MS: 358 (Mþ, 21), 329 (50), 328 (12), 311 (3), 282 (3), 280 (2), 252 (10), 251 (14), 236 (33),
235 (5), 207 (12), 176 (9), 151 (3), 105 (100), 77 (97), 51 (19). HR-EI-MS: 357.3585 (Mþ, C22H15NO4þ ;
calc. 357.1001).
3-[(2E)-3-Phenylprop-2-en-1-ylidene]pentane-2,4-dione; 11e). Yield: 65% (4.2 g). Yellow solid.
M.p. 968. IR (neat): 2923, 1688, 1644, 1610, 1281, 1233, 976, 756. 1H-NMR (250 MHz, CDCl3): 7.45 – 7.48
(m, 2 H); 7.31 – 7.37 (m, 3 H), 6.98 – 7.18 (m, 3 H); 2.38 (s, 6 H). 13C-NMR (125 MHz, CDCl3): 202.9;
197.1; 144.9; 142.8; 141.3; 135.3; 129.9; 128.8; 127.8; 123.3; 31.7; 26.3. GC/MS: tR 13.43. EI-MS: 214 (99,
Mþ), 199 (73), 171 (100), 128 (86), 115 (38), 77 (19). HR-EI-MS: 214.2581 (Mþ, C14H14Oþ2 ; calc.
214.0994).
3-Benzylidenepentane-2,4-dione (11f). Yield: 89% (5.0 g). Dark yellow oil. IR (neat): 3100, 1710,
1
1680, 1350, 1240. H-NMR (250 MHz, CDCl3): 7.47 (s, 1 H); 7.38 (m, 5 H); 2.41 (s, 3 H); 2.27 (s, 3 H).
13C-NMR (125 MHz, CDCl3): 200.3; 200.2; 142.4; 139.4; 132.9; 128.7 (2 C), 128.5; 128.3; 127.9; 29.4; 29.1.
GC/MS: tR 10.22. EI-MS: 188 (92, Mþ), 173 (23), 131 (100), 103 (39), 77 (13). HR-EI-MS: 188.2223 (Mþ,
C12H12Oþ2 ; calc. 188.0837).
3-(3-Methoxybenzylidene)pentane-2,4-dione (11g). Yield: 81% (5.3 g). Orange liquid. 1H-NMR
(CDCl3, 250 MHz) 7.45 (s, 1 H); 7.29 (t, J ¼ 7.9, 1 H); 6.98 – 6.90 (m, 3 H); 3.79 (s, 3 H); 2.41 (s, 3 H); 2.28

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(s, 3 H). 13C-NMR (125 MHz, CDCl3): 200.1; 199.9; 160.4; 145.0; 139.3; 136.2; 129.5; 120.4; 114.2; 114.0;
56.2; 29.7; 28.0. GC/MS: tR 12.04. EI-MS: 218 (70, Mþ), 203 (45), 175 (30), 161 (100), 133 (25), 89 (10),
63 (7). HR-EI-MS: 218.2490 (Mþ, C13H14O3þ ; calc. 218.0943).
3-(4-Methoxybenzylidene)pentane-2,4-dione (11h). Yield: 89% (5.8 g). Yellow liquid. IR (neat):
2925, 2835, 1709, 1654, 1600, 1570, 1513, 1423, 1307, 1260, 1172, 1028, 830. 1H-NMR (250 MHz, CDCl3):
7.40 (s, 1 H); 7.34 (d, J ¼ 8.6, 2 H); 6.88 (d, J ¼ 8.6, 2 H); 3.82 (s, 3 H); 2.38 (s, 3 H); 2.30 (s, 3 H).
13C-NMR (125 MHz, CDCl3): 206.4; 196.7; 162.0; 141.0; 140.0; 132.1; 125.6 (2 C); 114.8 (2 C); 55.7; 31.9;
26.6. GC/MS: tR 12.16. EI-MS: 218 (88, Mþ), 203 (67), 187 (27), 175 (45), 161 (100), 133 (38), 118 (10),
89 (17), 63 (9). HR-EI-MS: 218.2491 (Mþ, C13H14O3þ ; calc. 218.0943).
3-(3-Nitrobenzylidene)pentane-2,4-dione (11i). Yield: 75% (5.2 g). Yellow oil. IR (neat): 1708, 1667,
1
1528, 1359. H-NMR (250 MHz, CDCl3): 8.24 (s, 2 H); 7.69 – 7.47 (m, 3 H); 2.45 (s, 3 H); 2.30 (s, 3 H).
GC/MS: tR 12.72. EI-MS: 233 (57, Mþ), 216 (91), 176 (100), 191 (19), 131 (17), 101 (23), 75 (16), 51 (7).
HR-EI-MS: 233.2204 (Mþ, C12H11NO4þ ; calc. 233.0688).
3-(4-Nitrobenzylidene)pentane-2,4-dione (11j). Yield: 89% (6.2 g). Dark yellow oil. IR (neat): 3105,
3069, 1712, 1661, 1597, 1520, 1418, 1347, 1237, 1175, 862, 752, 691. 1H-NMR (250 MHz, CDCl3): 8.24 – 8.20
(m, 2 H); 7.55 (d, J ¼ 8.0, 2 H); 7.47 (s, 1 H), 2.44 (s, 3 H); 2.27 (s, 3 H). GC/MS: tR 12.82. EI-MS: 233 (8,
Mþ), 216 (100), 190 (17), 187 (18), 176 (62), 145 (10), 130 (13), 115 (12), 101 (10), 75 (12), 51 (7). HR-
EI-MS: 233.2204 (Mþ, C12H11NO4þ ; calc. 233.0688).
Ethyl (2E/Z)-2-Benzylidene-3-oxobutanoate (11k). Yield: 72% (4.7 g). Yellow liquid. IR (neat):
2922, 2853, 1730, 1664, 1460, 1376, 1207. (E)-Isomer: 1H-NMR (CDCl3, 250 MHz): 7.66 (s, 1 H); 7.46 –
1
7.32 (m, 5 H); 4.36 – 4.27 (m, 2 H); 2.34 (s, 3 H); 1.25 (t, J ¼ 7.2, 3 H). (Z)-Isomer: H-NMR (CDCl3,
250 MHz): 7.55 (s, 1 H); 7.46 – 7.32 (m, 5 H); 4.36 – 4.27 (m, 2 H); 2.41 (s, 3 H); 1.25 (t, J ¼ 7.2, 3 H).
13C-NMR (125 MHz, CDCl3): 193.9; 167.1; 139.2; 136.3; 134.5; 130.9; 130.3 (2 C); 128.9 (2 C); 61.4; 26.2;
13.4. GC/MS: tR 11.05. EI-MS: 218 (100, Mþ), 203 (24), 197 (22), 173 (29), 147 (16), 144 (12), 136 (23),
131 (53), 126 (10), 107 (21), 103 (30), 91 (9), 77 (18), 63 (5), 51 (7). HR-EI-MS: 218.2487 (Mþ,
C13H14Oþ3 ; calc. 218.0943).
Ethyl (2E/Z)-2-(3-Nitrobenzylidene)-3-oxobutanoate (11l). Yield: 78% (6.1 g). White solid. M.p.
1028. IR (neat): 1728.4, 1660.9, 1628.1, 1529.7, 780, 735. (E)- or (Z)-Isomer: 1H-NMR (250 MHz, CDCl3):
8.25 (s, 1 H); 8.23 (s, 1 H); 7.76 – 7.49 (m, 3 H); 4.33 (q, J ¼ 7.2, 2 H); 2.43 (s, 3 H); 1.21 (t, J ¼ 7.1, 3 H ) .
GC/MS: tR 13.13. EI-MS: 263 (52, Mþ), 248 (98), 246 (100), 220 (29), 218 (48), 202 (34), 176 (60), 129
(29), 101 (35), 75 (19), 51 (10). (Z)- or (E)-Isomer: 1H-NMR (250 MHz, CDCl3): 8.32 (s, 1 H); 8.23 (s,
1 H); 7.76 – 7.49 (m, 3 H); 4.33 (q, J ¼ 7.1, 2 H); 2.38 (s, 3 H); 1.34 (t, J ¼ 7.0, 3 H). 13C-NMR (125 MHz,
CDCl3): 198.7; 165.0; 148.6; 147.1; 139.0; 132.1; 132.0; 130.7; 123.8; 123.7; 61.4; 29.6; 14.2. GC/MS: tR
13.22. EI-MS: 263 (52, Mþ), 248 (98), 246 (100), 220 (27), 218 (36), 202 (30), 176 (45), 129 (21), 101
(22), 75 (9), 51 (4). HR-EI-MS: 263.2457 (Mþ, C13H13NO5þ ; calc. 263.0794).
Ethyl (2E/Z)-2-(4-Nitrobenzylidene)-3-oxobutanoate (11m). Yield: 77% (6.1 g). Light yellow solid.
M.p. 1728. IR (neat): 1732.3, 1711.1, 1608.8, 1529.7, 1464.1, 844.9. (Z)- or (E)-Isomer: 1H-NMR
(250 MHz, CDCl3): 8.25 – 8.20 (m, 2 H); 7.67 – 7.53 (m, 3 H), 4.33 (q, J ¼ 4.0, 2 H); 2.44 (s, 3 H); 1.34 (t,
J ¼ 7.2, 3 H). GC/MS: tR 13.18. EI-MS: 263 (6, Mþ), 246 (100), 216 (23), 189 (6), 176 (24), 152 (11), 101
(9), 75 (80, 51 (4). (E)- or (Z)-Isomer: 1H-NMR (250 MHz, CDCl3): 8.25 – 8.20 (m, 2 H), 7.67 – 7.53 (m,
3 H); 4.30 (q, J ¼ 4.0, 2 H); 2.35 (s, 3 H); 1.25 (t, J ¼ 7.1, 3 H ) . 13C-NMR (125 MHz, CDCl3): 200.3; 175.0;
165.2; 145.3; 139.3; 130.0; 128.2 (2 C); 125.5 (2 C); 45; 30; 15. GC/MS: tR 13.25. EI-MS: 263 (6, Mþ), 246
(100), 216 (23), 189 (6), 176 (24), 152 (11), 101 (9), 75 (80, 51 (4). HR-EI-MS: 263.2460 (Mþ,
C13H13NOþ5 ; calc. 263.0794).
Ethyl (2E,4E)-2-Acetyl-5-phenylpenta-2,4-dienoate (11n). Yield: 67% (4.9 g). Yellow liquid. (E)- or
(Z)-isomer. GC/MS: tR 12.81. EI-MS: 244 (48, Mþ), 215 (100), 199 (12), 155 (20), 128 (25), 115 (15), 77
(5). Mixture of (E)- and (Z)-isomers: 1H-NMR (CDCl3, 250 MHz): 7.02 – 7.50 (m, 12 H); 6.88 – 6.64
(4 H); 4.39 (q, J ¼ 7.2, 2 H); 4.29 (q, J ¼ 7.1, 2 H); 2.45 (s, 3 H); 2.40 (s, 3 H); 1.40 (t, J ¼ 7.3, 3 H); 1.34 (t,
J ¼ 7.4, 3 H). GC/MS: tR 12.94. EI-MS: 244 (52, Mþ), 215 (100),199 (18), 155 (35), 128 (49), 115 (33), 77
(6).
Diethyl 2-Benzylidenepropanedioate (11o). Yield: 87% (6.5 g). Colorless liquid. IR (neat): 2923,
1
2853, 1708, 1659, 1616, 1490, 1241, 1093, 823. H-NMR (250 MHz, CDCl3): 7.68 (s, 1 H); 7.40 – 7.30 (m,

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5 H); 4.27 (q, J ¼ 7.0, 4 H); 1.26 (t, J ¼ 7.0, 3 H); 1.22 (t, J ¼ 7.0, 3 H). 13C-NMR (125 MHz, CDCl3): 166.5;
163.9; 141.9; 132.8; 130.4; 129.6; 128.6 (2 C); 126.2; 61.6; 61.5; 14.0; 13.9. GC/MS: tR 11.78. EI-MS: 248
(66, Mþ), 219 (19), 203 (87), 173 (35), 158 (76), 147 (17), 130 (71), 102 (100), 91 (17), 77 (36), 51 (16).
HR-EI-MS: 248.2737 (Mþ, C14H14O4þ ; calc. 248.1049).
Diethyl 2-(3-Methoxybenzylidene)propanedioate (11p). Yield: 89% (7.4 g). IR (neat): 2906, 2982,
1
1754, 1254, 1308. H-NMR (250 MHz, CDCl3): 7.69 (s, 1 H); 7.31 – 6.92 (m, 4 H); 4.32 (q, J ¼ 7.2, 2 H);
4.29 (q, J ¼ 7.3, 2 H); 3.78 (s, 3 H); 1.32 (t, J ¼ 7.1, 3 H); 1.28 (t, J ¼ 7.2, 3 H). 13C-NMR (125 MHz, CDCl3):
163.8; 166.3; 140.0; 132.9; 130.4; 130.3; 129.0; 125.4 (2 C); 60.1; 61.4; 14.0, 13.7. GC/MS: tR 12.90. EI-MS:
278 (100, Mþ), 233 (73), 249 (5), 188 (74), 160 (46), 132 (69), 102 (21), 89 (20), 63 (10). HR-EI-MS:
278.3006 (Mþ, C15H18Oþ5 ; calc. 278.1154).
Diethyl 2-(3-Nitrobenzylidene)propanedioate (11q). Yield: 87% (7.6 g). 1H-NMR (250 MHz,
CDCl3): 8.19 (s, 1 H); 8.12 (d, J ¼ 7.8, 1 H); 7.96 – 7.89 (m, 3 H), 4.32 (q, J ¼ 7.0, 2 H); 4.30 (q, J ¼ 7.0,
2 H); 1.34 (t, J ¼ 7.1, 3 H); 1.29 (t, J ¼ 7.1, 3 H). GC/MS: tR 13.61. EI-MS: 293 (39, Mþ), 264 (30),248
(100), 203 (81), 201 (36), 147 (48), 101 (35), 75 (15), 51 (5). HR-EI-MS: 293.2717 (Mþ, C14H15NO6þ ;
calc. 293.0899).
Diethyl 2-(4-Nitrobenzylidene)propanedioate (11r). Yield: 89% (7.8 g). 1H-NMR (250 MHz,
CDCl3): 8.22 (d, J ¼ 8.6, 2 H); 7.74 (s,1 H); 7.60 (d, J ¼ 8.5, 2 H); 4.33 (q, J ¼ 6.9, 4 H); 1.34 (t, J ¼ 7.1,
3 H); 1.26 (t, J ¼ 7.0, 3 H). GC/MS: tR 13.65. EI-MS: 293 (34, Mþ), 248 (100), 220 (43), 203 (96), 175 (48),
147 (52), 101 (22), 75 (32), 51 (9). HR-EI-MS: 293.2715 (Mþ, C14H15NO6þ ; calc. 293.0899).
Diethyl 2-[(2E/Z)-3-Phenylprop-2-en-1-ylidene]propanedioate; 11s). Yield: 42% (3.5 g). Major
1
isomer: IR (neat): 2982, 1716, 1619, 1373, 1245, 1152, 1098, 1056, 1024. H-NMR (CDCl3, 500 MHz):
7.44 – 7.30 (m, 5 H); 7.00 (d, J ¼ 11.2, 1 H); 6.65 (t, J ¼ 11.6, 1 H); 4.36 (q, J ¼ 7.2, 2 H); 4.24 (q, J ¼ 7.2,
2 H); 1.36 (t, J ¼ 7.2, 3 H); 1.28 (t, J ¼ 7.2, 3 H). 13C-NMR (CDCl3, 125 MHz): 165.4; 164.6; 141.4; 139.9;
135.7; 129.6; 128.7; 128.6; 127.5; 124.0; 61.4 (2 C); 61.3; 14.2; 14.1. HR-EI-MS: 274.3115 (Mþ, C16H18O4þ ;
calc. 274.1205).
1
Diethyl 2-Ethylidenepropanedioate (11t). Yield: 72% (12.0 g). Yellow liquid. H-NMR (250 MHz,
CDCl3): 7.19 (q, J ¼ 6.9, 1 H), 4.22 (q, J ¼ 7.2, 4 H); 1.78 (d, J ¼ 6.9, 3 H); 1.34 (t, J ¼ 7.2, 6 H). 13C-NMR
(75 MHz, CDCl3): 166.0; 147.1; 127.3; 62.1 (2 C); 16.2; 14.4; 9.3. HR-EI-MS: 186.2055 (Mþ, C9H14O4þ ;
calc. 186.0892).
General Procedure for the Catalytic Reactions of Bis[carbonyls] 11a – 11t with Dimethyl Diazo-
malonate (12). To a soln. of 11a – 11t (3 mmol) in benzene (10 ml) was added [Cu(acac)2] (0.01 mmol),
and the mixture was heated under reflux. A soln. of 12 or 13 (5 mmol) in benzene (5 ml) was added
dropwise over 3 h. When the IR spectrum indicated total consumption of 12 or 13 (absence of
characteristic diazo band at 2130 cmꢀ1), the mixture was concentrated under reduced pressure and
subjected to flash chromatography on silica gel.
Dimethyl 4-Benzoyl-3,5-diphenylfuran-2,2(3H)-dicarboxylate (14a12). Yield: 56% (0. 74 g).
1H-NMR (250 MHz, CDCl3): 7.52 (d, J ¼ 7.2, 2 H); 7.41 (d, J ¼ 7.1, 2 H); 7.30 – 7.09 (m, 11 H); 5.66 (s,
1 H); 3.91 (s, 3 H); 3.23 (s, 3 H). 13C-NMR (125 MHz, CDCl3): 190.6; 166.4; 164.7; 162.0; 137.1; 135.7
(2 C); 130.8; 129.6 (2 C); 128.6 (2 C); 128.1 (2 C); 127.8 (2 C); 127.6 (2 C); 127.3 (2 C); 126.8 (2 C); 113.5;
90.8; 56.7 (2 C); 28.7. GC/MS: tR 19.05. EI-MS: 442 (5, Mþ), 383 (90), 351 (100), 337 (40), 305 (20), 273
(20), 189 (15), 105 (92), 77 (55), 59 (5). HR-EI-MS: 442.4600 (Mþ, C27H22O6þ ; calc. 442.1416).
Dimethyl 4-Benzoyl-3-(3-methoxyphenyl)-5-phenylfuran-2,2(3H)-dicarboxylate (14b12). Yield: 47%
(0.66 g). 1H-NMR (250 MHz, CDCl3): 7.47 (dd, J ¼ 8.0, 1.8, 2 H); 7.36 (dd, J ¼ 8.0, 1.8, 2 H); 7.21 – 7.09 (m,
7 H); 6.86 (s, 1 H); 6.68 (dd, J ¼ 8.0, 1.8, 1 H); 6.63 (dd, J ¼ 8.0, 1.8, 1 H); 5.64 (s, 1 H); 3.85 (s, 3 H); 3.65
(s, 3 H); 3.25 (s, 3 H). 13C-NMR (CDCl3, 125 MHz): 196.0; 167.1; 167.0; 162.5; 160.0; 141.2; 138.0; 132.0
(2 C); 130.7 (2 C); 129.8 (2 C); 129.5; 129.3 (2 C); 128.0 (2 C); 119.9; 126.1; 114.9; 114.2; 92.5; 57.7; 54.9;
54.0; 52.6. GC/MS: tR 20.47. EI-MS: 472 (5, Mþ), 454 (10), 412 (18), 381 (100), 335 (10), 303 (8), 221 (5),
105 (80), 77 (30), 59 (2). HR-EI-MS: 472.4844 (Mþ, C28H24O7þ ; calc. 472.1522).
Dimethyl 4-Benzoyl-3-(4-methoxyphenyl)-5-phenylfuran-2,2(3H)-dicarboxylate (14c12). Yield: 62%
1
(0.88 g). Yellow oil. H-NMR (250 MHz, CDCl3): 7.53 (d, J ¼ 7.3, 1 H); 7.43 (d, J ¼ 7.2, 1 H); 7.25 – 7.08
(m, 12 H); 5.60 (s, 1 H); 3.92 (s, 3 H); 3.74 (s, 3 H); 3.32 (s, 3 H). 13C-NMR (125 MHz, CDCl3): 189.6;
168.2; 166.5; 161.6; 148.2; 136.7; 134.4 (2 C); 132.5; 129.6 (2 C); 128.3 (2 C); 127.9 (2 C); 126.8 (2 C);

Helvetica Chimica Acta – Vol. 95 (2012)
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126.2 (2 C); 125.9 (2 C); 119.7; 117.2; 110.2; 97.8; 62.8; 52.4 (2 C). GC/MS: tR 21.83. EI-MS: 472 (5, Mþ),
454 (3), 412 (48), 381 (100), 387 (30), 335 (7), 303 (10), 221 (15), 105 (70), 77 (45), 59 (10). HR-EI-MS:
472.4867 (Mþ, C28H24Oþ7 ; calc. 472.1522).
Dimethyl 4-Benzoyl-3-(4-nitrophenyl)-5-phenylfuran-2,2(3H)-dicarboxylate (14d12). The product
could not be isolated from the crude mixture. GC/MS: tR 21.75. EI-MS: 487 (3, Mþ), 441 (12), 427 (55),
410 (10), 396 (100), 382 (75), 122 (22), 105 (25), 77 (15), 59 (7).
Dimethyl 4-Acetyl-5-methyl-3-[(E)-2-phenylethenyl]furan-2,2(3H)-dicarboxylate (14e12). Yield:
54% (0.56 g). Yellow oil. 1H-NMR (250 MHz, CDCl3): 7.26 – 7.18 (m, 5 H); 6.54 (d, J ¼ 15.9, 1 H);
5.95 (dd, J ¼ 16.1, 9.3, 1 H); 4.67 (d, J ¼ 9.3, 1 H); 3.79 (s, 3 H); 3.59 (s, 3 H); 2.31 (s, 3 H); 2.11 (s, 3 H).
GC/MS: tR 14.30. EI-MS: 344 (4, Mþ), 312 (8), 301 (9), 285 (17), 253 (100), 224 (37), 153 (11), 59 (5).
HR-EI-MS: 344.3576 (Mþ, C19H20O6þ ; calc. 344.1260).
Dimethyl 4-Acetyl-3-(3-methoxyphenyl)-5-methylfuran-2,2(3H)-dicarboxylate (14g12). Yield: 28%
(0.29 g). Yellow oil. 1H-NMR (CDCl3, 250 MHz): 7.23 – 7.20 (m, 2 H); 6.82 – 6.76 (m, 2 H); 5.18 (s, 1 H);
3.86 (s, 3 H); 3.76 (s, 3 H); 3.23 (s, 3 H); 1.92 (s, 3 H); 1.90 (s, 3 H).13C-NMR (CDCl3, 125 MHz): 193.3;
166.4; 165.7; 164.1; 158.7; 137.7; 128.5 (2 C); 120.1; 113.9; 112.6; 91.5; 54.3; 53.7; 52.8; 51.5; 28.6;13.6. GC/
MS: tR 12.78. EI-MS: 348 (2, Mþ), 300 (45), 289 (40), 257 (100), 241 (10), 215 (25), 193 (30), 159 (10),
115 (10), 59 (5). HR-EI-MS: 348.3462 (Mþ, C18H20O7þ ; calc. 348.1209).
Dimethyl 4-Acetyl-3-(4-methoxyphenyl)-5-methylfuran-2,2(3H)-dicarboxylate (14h12). Yield: 27%
1
(0.28 g). Yellow oil. H-NMR (CDCl3, 250 MHz): 7.07 (d, J ¼ 7.9, 2 H); 6.79 (d, J ¼ 8.1, 2 H); 5.15 (s,
1 H); 3.84 (s, 3 H); 3.75 (s, 3 H); 3.22 (s, 3 H); 2.41 (s, 3 H);1.87 (s, 3 H). 13C-NMR (CDCl3, 125 MHz):
194.7; 167.7; 167.8; 165.5; 159.6; 130.2; 129.1 (2 C); 114.1 (2 C); 110.2; 92.6; 55.5; 54.2; 52.7 (2 C); 29.8;
14.9. GC/MS: tR 14.09. EI-MS: 348 (55, Mþ), 317 (10), 305 (15), 288 (75), 257 (100), 215 (15), 159 (10),
115 (7), 59 (3). HR-EI-MS: 348.3487 (Mþ, C18H20O7þ ; calc. 348.1209).
Dimethyl 4-Acetyl-5-methyl-3-(3-nitrophenyl)furan-2,2(3H)-dicarboxylate (14i12). Yield: 18%
(0.20 g). Yellow oil. 1H-NMR (CDCl3, 250 MHz): 8.12 (d, J ¼ 7.3, 1 H); 8.05 (s, 1 H); 7.55 – 7.48 (m,
2 H); 5.34 (s, 1 H); 3.88 (s, 3 H); 3.23 (s, 3 H); 3.22 (s, 3 H); 2.04 (s, 3 H). 13C-NMR (CDCl3, 125 MHz):
191.7; 166.3; 165.8; 163.8; 147.3; 138.7; 128.4 (2 C); 122.1 (2 C); 114.3; 90.9; 53.3; 53.1; 51.7; 28.6; 14.0.
GC/MS: tR 14.69. EI-MS: 363 (35, Mþ), 346 (45), 304 (43), 288 (50), 272 (100), 256 (10), 230 (8), 167 (6),
128 (10), 59 (6). HR-EI-MS: 363.3178 (Mþ, C17H17NO8þ ; calc. 363.0954).
Dimethyl 4-Acetyl-5-methyl-3-(4-nitrophenyl)furan-2,2(3H)-dicarboxylate (14j12). The product was
isolated together with the product 15j12 and the starting material 11j. 1H-NMR (250 MHz, CDCl3): 7.59
(d, J ¼ 8.4, 2 H); 7.23 – 7.15 (m, 2 H); 5.33 (s, 1 H); 4.00 (s, 3 H); 3.72 (s, 3 H); 2.33 (s, 3 H); 2.28 (s, 3 H).
GC/MS: tR 14.88. EI-MS: 363 (8, Mþ), 348 (3), 320 (10), 304 (100), 288 (40), 272 (42), 260 (4), 230 (5),
199 (3), 167 (3), 128 (5), 59 (5).
Dimethyl 4-Acetyl-5-ethoxy-3-(3-nitrophenyl)furan-2,2(3H)-dicarboxylate (14l12). The product
could not be isolated from the crude mixture. GC/MS: tR 14.73. EI-MS: 393 (45, Mþ), 376 (100), 348
(35), 302 (37), 288 (90), 273 (25), 230 (15), 183 (7), 128 (9), 59 (7).
Dimethyl 4-Acetyl-5-ethoxy-3-(4-nitrophenyl)furan-2,2(3H)-dicarboxylate (14m12). The product
could not be isolated from the crude mixture. GC/MS: tR 14.93. EI-MS: 393 (28, Mþ), 361 (18), 348
(32), 334 (100), 333 (97), 319 (70), 288 (90), 246 (10), 230 (12), 183 (7), 128 (10), 59 (12).
Dimethyl 4-Acetyl-5-ethoxy-3-[(E)-2-phenylethenyl]furan-2,2(3H)-dicarboxylate (14n12). The prod-
1
uct was isolated as a mixture with 16n12. H-NMR (250 MHz, CDCl3): 7.42 – 7.13 (m, 5 H), 6.58 (d, J ¼
14.9, 1 H); 5.99 (dd, J ¼ 14.9, 9.3, 1 H); 4.68 (d, J ¼ 9.3, 1 H); 4.22 (q, J ¼ 7.1, 2 H); 3.83 (s, 3 H); 3.66
(s, 3 H); 2.85 (s, 3 H); 1.17 (t, J ¼ 7.1, 3 H). GC/MS: tR 14.48. EI-MS: 374 (5, Mþ), 342 (18), 329 (18), 283
(62), 269 (100), 240 (77), 209 (26), 153 (26), 115 (18), 77 (8), 59 (10).
4-Ethyl 2,2-Dimethyl 5-Ethoxy-3-(3-methoxyphenyl)furan-2,2,4(3H)-tricarboxylate (14p12). Yield:
1
67% (0.82 g). Dark yellow oil. H-NMR (250 MHz, CDCl3): 7.39 – 7.25 (m, 1 H); 6.83 – 6.77 (m, 3 H);
5.07 (s, 1 H); 4.58 – 4.45 (m, 4 H); 3.86 (s, 3 H); 3.78 (s, 3 H); 3.24 (s, 3 H); 1.02 (t, J ¼ 7.2, 3 H); 0.87 (t, J ¼
7.2, 3 H). 13C-NMR (CDCl3, 125 MHz): 179.3; 167.9; 166.1; 164.8; 159.6; 141.3; 128.9; 119.8; 113.2; 110.5;
89.8; 69.7; 62.1; 59.7; 58.0; 51.4; 50.7; 37.2; 18.9; 14.1. GC/MS: tR 12.69. EI-MS: 408 (21, [M þ 1]þ), 348
(22), 334 (71), 274 (75), 159 (64), 59 (32), 29 (100). HR-EI-MS: 408.3984 (Mþ, C20H24O9þ ; calc.
408.1420).

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4-Ethyl 2,2-Dimethyl 5-Ethoxy-3-(3-nitrophenyl)furan-2,2,4(3H)-tricarboxylate (14q12). The product
could not be isolated from the crude mixture. GC/MS: tR 14.31. EI-MS: 423 (14, [M þ 1]þ), 391 (95), 332
(100), 300 (48), 228 (90), 214 (58), 59 (24).
4-Ethyl 2,2-Dimethyl 5-Ethoxy-3-(4-nitrophenyl)furan-2,2,4(3H)-tricarboxylate (14r12). Yield: 71%
(0.90 g). Yellow oil. 1H-NMR (250 MHz, CDCl3): 8.20 – 8.11 (m, 2 H); 7.47 – 7.34 (m, 2 H); 5.23 (s, 1 H);
4.58 – 4. 47 (m, 2 H); 4.36 – 4.22 (m, 2 H); 3.69 (s, 3 H); 3.66 (s, 3 H); 1.31 (t, J ¼ 7.0, 3 H); 1.01 (t, J ¼ 7.1,
3 H). GC/MS: tR 12.69. EI-MS: 423 (1, [M þ 1]þ), 407 (60), 364 (44), 347 (51), 300 (60),275 (40), 255
(55), 59 (33). HR-EI-MS: 423.3718 (Mþ, C19H21NO1þ0 ; calc. 423.1165).
4-Ethyl 2,2-Dimethyl 5-Ethoxy-3-[(E)-2-phenylethenyl]furan-2,2,4(3H)-tricarboxylate (14s12).
Yield: 65% (0.79 g). Yellow oil. 1H-NMR (250 MHz, CDCl3): 7.35 – 7.28 (m, 5 H); 6.80 (d, J ¼ 15.7,
1 H); 6.36 (dd, J ¼ 15.7, 9.7, 1 H); 5.02 (d, J ¼ 9.7, 1 H); 4.36 – 4.15 (m, 4 H); 3.85 (s, 3 H); 3.76 (s, 3 H),
1.31 (t, J ¼ 7.2, 3 H); 1.26 (t, J ¼ 6.8, 3 H). GC/MS: tR 14.78. EI-MS: 404 (5, Mþ), 373 (40), 358 (100), 298
(32), 280 (34), 267 (70), 253 (85), 184 (83), 156 (90),128 (84), 123 (50), 115 (48), 59 (35). HR-EI-MS:
404.4119 (Mþ, C21H24Oþ8 ; calc. 404.1471).
Dimethyl 6-Acetyl-7-methyl-3-phenyloxepine-2,2(3H)-dicarboxylate (16e12). Yield: 49% (0.51 g).
1
Yellow oil. H-NMR (250 MHz, CDCl3): 7.06 – 7.26 (m, 5 H); 6.03 (d, J ¼ 12.2, 1 H); 5.96 (dd, J ¼ 12.2,
6.3, 1 H); 4.58 (d, J ¼ 6.3, 1 H); 3.70 (s, 3 H); 3.44 (s, 3 H); 2.28 (s, 3 H); 2.18 (s, 3 H). GC/MS: tR 13.89.
EI-MS: 344 (48, Mþ), 312 (13), 301 (15), 280 (100), 253 (72), 225 (30), 210 (48), 153 (32), 59 (14). HR-
EI-MS: 344.3376 (Mþ, C19H20O6þ ; calc. 344.1260).
Dimethyl 4-Acetyl-9-methoxy-3-methyl-2-benzoxepine-1,1(3H)-dicarboxylate (15g12). The product
was isolated as a mixture with 15g12’. 1H-NMR (CDCl3, 250 MHz): 7.37 – 6.92 (m, 3 H); 7.34 (s, 1 H); 5.50
(q, J ¼ 6.5, 1 H); 3.82 (s, 3 H); 3.74 (s, 3 H); 3.76 (s, 3 H); 2.38 (s, 3 H); 1.29 (d, J ¼ 6.5, 3 H). GC/MS: tR
13.51. EI-MS: 348 (18, Mþ), 300 (50), 289 (16), 257 (48), 232 (22), 193 (42), 148 (15), 135 (10), 84 (10),
59 (8), 43 (100).
Dimethyl 4-Acetyl-7-methoxy-3-methyl-2-benzoxepine-1,1(3H)-dicarboxylate (15g’12). Yield: 12%
(0.13 g). Dark yellow oil. 1H-NMR (CDCl3, 250 MHz): 7.37 (s, 1 H); 6.95 (d, J ¼ 8.8, 1 H); 6.79 – 6.76 (m,
2 H); 5.44 (q, J ¼ 6.5, 1 H); 3.91 (s, 3 H); 3.82 (s, 3 H); 3.71 (s, 3 H); 2.40 (s, 3 H); 1.30 (d, J ¼ 6.5,
3 H).13C-NMR (CDCl3, 125 MHz): 196.9; 167.7; 167.4; 158.6; 144.6; 137.9; 133.8; 130.2; 127.1; 116.9;
113.0; 85.0; 72.0; 54.5; 52.3; 51.1; 25.6; 20.8. GC/MS: tR 13.77. EI-MS: 348 (2, Mþ), 316 (4), 305 (12), 289
(50), 275 (30), 256 (35), 242 (38), 229 (85), 217 (20), 187 (100), 159 (38), 144 (30), 115 (38), 59 (20).
HR-EI-MS: 348.3494 (Mþ, C18H20O7þ ; calc. 348.1209).
Dimethyl 4-Acetyl-8-methoxy-3-methyl-2-benzoxepine-1,1(3H)-dicarboxylate (15h12). Yield: 22%
1
(0.23 g). Yellow oil. H-NMR (CDCl3, 250 MHz): 7.37 (s, 1 H); 7.19 (d, J ¼ 6.1, 1 H); 6.89 (d, J ¼ 6.3,
1 H); 6.56 (s, 1 H); 5.47 (d, J ¼ 6.4, 1 H); 3.89 (s, 3 H); 3.77 (s, 3 H); 3.68 (s, 3 H); 2.36 (s, 3 H); 1.30 (d,
J ¼ 6.4, 3 H). 13C-NMR (CDCl3, 125 MHz): 198.1; 168.3; 160.3; 143.4; 139.4; 134.8; 129.9; 125.8; 114.2;
113.1; 86.4; 74.2; 55.7; 53.6; 53.4; 26.6; 22.1. GC/MS: tR 14.72. EI-MS: 348 (5, Mþ), 333 (10), 305 (100),
273 (40), 257 (75), 245 (73), 242 (72), 214 (70), 187 (50), 159 (12), 115 (15), 59 (7). HR-EI-MS: 348.3479
(Mþ, C18H20Oþ7 ; calc. 348.1209).
Dimethyl 4-Acetyl-3-methyl-9-nitro-2-benzoxepine-1,1(3H)-dicarboxylate (15i12). Yield: 23%
1
(0.25 g). Yellow oil. H-NMR (CDCl3, 250 MHz): 7.83 (d, J ¼ 7.2, 1 H); 7.61 (d, J ¼ 6.9, 1 H); 7.54 – 7.48
(m, 1 H); 7.32 (s, 1 H); 5.64 (q, J ¼ 6.4, 1 H); 3.81 (s, 3 H); 3.75 (s, 3 H); 2.40 (s, 3 H); 1.27 (d, J ¼ 6.4,
3 H). 13C-NMR (CDCl3, 125 MHz): 196.2; 167.5; 165.9; 148.5; 146.2; 135.7; 135.5; 135.3; 133.9; 127.9;
123.9; 82.8; 73.5; 52.9; 52.1; 25.7; 20.6. GC/MS: tR 15.41. EI-MS: 346 (3), 320 (90), 304 (15), 288 (50), 272
(100), 257 (80), 229 (30), 202 (8), 156 (6), 128 (15), 59 (6). HR-EI-MS: 363.3172 (Mþ, C17H17NO8þ ; calc.
363.0954).
Dimethyl 4-Acetyl-3-methyl-7-nitro-2-benzoxepine-1,1(3H)-dicarboxylate (15i’12). The product could
not be isolated from the crude mixture. GC/MS: tR 15.31. EI-MS: 346 (2), 320 (90), 304 (15), 288 (55),
272 (100), 257 (80), 229 (35), 202 (8), 156 (6), 128 (15), 59 (6).
Dimethyl 4-Acetyl-3-methyl-8-nitro-2-benzoxepine-1,1(3H)-dicarboxylate (15j12). The product could
be isolated together with 14j12 and the starting material 11j. 1H-NMR (250 MHz, CDCl3): 7.89 (s, 1 H);
7.23 – 7.15 (m, 2 H); 7.16 (s, 1 H); 5.56 (q, J ¼ 6.5, 1 H); 3.90 (s, 3 H); 3.74 (s, 3 H); 2.46 (s, 3 H); 1.35 (d,
J ¼ 6.4, 3 H). GC/MS: tR 15.26. EI-MS: 346 (2), 320 (90), 304 (35), 288 (50), 272 (100), 257 (55), 229
(20), 202 (10), 156 (7), 128 (12), 59 (7).

Helvetica Chimica Acta – Vol. 95 (2012)
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4-Ethyl 1,1-Dimethyl 3-Methyl-9-nitro-2-benzoxepine-1,1,4(3H)-tricarboxylate (15l12) or 4-Ethyl 1,1-
Dimethyl 3-Methyl-7-nitro-2-benzoxepine-1,1,4(3H)-tricarboxylate (15l’12). The products could not be
isolated in pure form, both isomers were observed by GC/MS analysis, and both gave the same mass
spectra. GC/MS: tR 15.61 and 15.69. EI-MS: 393 (2, Mþ), 350 (30), 319 (28), 302 (100), 288 (25), 273 (45),
260 (55), 215 (15), 202 (12), 128 (20), 59 (15).
4-Ethyl 1,1-Dimethyl 3-Methyl-8-nitro-2-benzoxepine-1,1,4(3H)-tricarboxylate (15m12). Yield: 33%
(0.39 g). Dark yellow oil. 1H-NMR (250 MHz, CDCl3): 8.23 (d, J ¼ 8.7, 1 H); 8.18 (s, 1 H); 7.70 (d, J ¼ 8.6,
1 H); 7.50 (s, 1 H); 4.47 – 4.05 (m, 3 H); 3.87 (s, 3 H); 3.76 (s, 3 H); 1.70 – 1.55 (m, 3 H); 1.24 (d, J ¼ 6.5,
3 H). 13C-NMR (CDCl3, 125 MHz): 173.9; 172.0; 165.3; 149.5; 138.6; 138.3; 134.2; 129.4; 128.7; 125.0;
123.0; 91.4; 65.0; 61.5; 52.5; 51.6; 19.1; 13.1. GC/MS: tR 15.60. EI-MS: 393 (1, Mþ), 350 (35), 304 (88), 302
(100), 273 (45), 260 (65), 215 (15), 185 (15), 128 (15), 59 (12). HR-EI-MS: 393.3434 (Mþ, C18H19NO9þ ;
calc. 393.1060).
6-Ethyl 2,2-Dimethyl 7-Methyl-3-phenyloxepine-2,2,6(3H)-tricarboxylate (16n12). The product was
isolated as a mixture with 14n12. 1H-NMR (250 MHz, CDCl3): 7.42 – 7.13 (m, 5 H); 6.29 (d, J ¼ 12.4, 1 H);
5.98 (dd, J ¼ 12.3, 6.6, 1 H); 4.64 (d, J ¼ 6.6, 1 H); 4.09 (q, J ¼ 7.1, 2 H); 3.74 (s, 3 H); 3.60 (s, 3 H); 2.28 (s,
3 H); 1.30 (t, J ¼ 7.1, 3 H). GC/MS: tR 14.30. EI-MS: 374 (48, Mþ), 342 (8), 329 (26), 310 (100), 282 (59),
269 (53), 253 (30), 153 (38), 115 (24), 77 (9), 59 (14). HR-EI-MS: 374.3831 (Mþ, C20H22O7þ ; calc.
374.1366).
Ethyl 4-Acetyl-2,3-dihydro-5-methyl-3-[(E)-2-phenylethenyl]furan-2-carboxylate (14e13). Yield:
41% (0.37 g). Yellow oil. 1H-NMR (250 MHz, CDCl3): 7.35 – 7.25 (m, 5 H); 6.51 (d, J ¼ 15.8, 1 H);
6.03 (d, J ¼ 15.9, 9.4, 1 H); 5.15 (d, J ¼ 9.9, 1 H); 4.22 – 4.09 (m, 3 H); 2.35 (s, 3 H); 2.16 (s, 3 H); 1.13 (t,
J ¼ 7.1, 3 H ) . 13C-NMR (CDCl3, 125 MHz): 193.1; 171.4; 167.1; 138.1; 129.6 (2 C); 129.4; 129.3; 128.4
(2 C); 127.8; 117.0; 73.1; 60.6; 29.6; 21.2; 15.4; 13.9. GC/MS: tR 13.93. EI-MS: 300 (30, Mþ), 257 (40), 254
(100), 227 (95), 211 (60), 185 (35), 141 (50), 115 (48), 91 (45), 77 (25). HR-EI-MS: 300.3495 (Mþ,
C18H20Oþ4 ; calc. 300.1362).
Ethyl 4-Acetyl-2,3-dihydro-5-methyl-3-phenylfuran-2-carboxylate (14f13). Yield: 7% (0.06 g). Yellow
oil. 1H-NMR (250 MHz, CDCl3): 7.35 – 7.13 (m, 5 H); 5.31 (d, J ¼ 10.4, 1 H); 4.60 (d, J ¼ 10.5, 1 H); 4.37 –
4.13 (m, 2 H); 2.44 (s, 3 H); 1.90 (s, 3 H); 0.85 (t, J ¼ 7.0, 3 H). 13C-NMR (CDCl3, 125 MHz): 205.7; 196.6;
143.1; 140.0; 133.2; 130.9; 129.9 (2 C); 129.3 (2 C); 73.2; 61.8; 31.8; 26.7; 22.9; 14.3. GC/MS: tR 12.47. EI-
MS: 274 (27, Mþ), 259 (5), 231 (25), 201 (100), 185 (35), 158 (10), 128 (15), 115 (14), 77 (7). HR-EI-MS:
274.3130 (Mþ, C16H18Oþ4 ; calc. 274.1205).
Ethyl 4-Acetyl-2,3-dihydro-3-(3-methoxyphenyl)-5-methylfuran-2-carboxylate (14g13). The product
1
was isolated together with 15g’13. H-NMR (CDCl3, 250 MHz): 7.29 – 6.66 (m, 4 H), 5.27 (d, J ¼ 10.3,
1 H), 4.56 (d, J ¼ 10.3, 1 H); 4.31 – 4.16 (m, 2 H); 3.74 (s, 3 H); 2.41 (s, 3 H); 1.90 (s, 3 H); 1.27 (t, J ¼ 7.2,
3 H). GC/MS: tR 13.40. EI-MS: 304 (55, Mþ), 289 (2), 261 (15), 215 (20), 231 (100), 188 (12) 159 (10),
145 (9), 115 (18), 77 (7).
Ethyl 4-Acetyl-2,3-dihydro-3-(4-methoxyphenyl)-5-methylfuran-2-carboxylate (14h13). Yield: 31%
(0.28 g). Yellow oil. 1H-NMR (CDCl3, 250 MHz): 7.25 – 6.66 (m, 4 H); 5.26 (d, J ¼ 10.3, 1 H); 4.55 (d, J ¼
10.3, 1 H); 4.31 – 4.20 (m, 2 H); 3.75 (s, 3 H); 2.42 (s, 3 H); 1.89 (s, 3 H); 1.35 – 1.24 (m, 3 H). 13C-NMR
(CDCl3, 125 MHz): 194.9; 168.7; 167.8; 1595; 139.8; 130.1; 129.8; 120.2; 116.1; 114.0 (2 C); 84.0; 61.4;
55.5; 51.5; 15.1; 13.9. GC/MS: tR 13.71. EI-MS: 304 (55, Mþ), 261 (60), 231 (100), 214 (35), 188 (30), 159
(10), 115 (11), 77 (4). HR-EI-MS: 304.3386 (Mþ, C17H20O5þ ; calc. 304.1311).
Ethyl 4-Acetyl-2,3-dihydro-5-methyl-3-(3-nitrophenyl)furan-2-carboxylate (14i13). Yield: 18%
1
(0.17 g). Yellow oil. H-NMR (CDCl3, 250 MHz): 8.29 – 7.42 (m, 4 H); 5.33 (d, J ¼ 10.5, 1 H); 4.74 (d,
J ¼ 10.6, 1 H); 4.30 – 4.15 (m, 2 H); 2.47 (s, 3 H); 2.06 (s, 3 H); 1.27 (t, J ¼ 7.0, 3 H). 13C-NMR (CDCl3,
125 MHz): 191.9; 168.0; 165.9; 147.2; 139.5; 133.4; 128.4; 122.4; 121.8; 115.5; 82.1; 60.5; 40.7; 28.5; 14.2;
12.7. GC/MS: tR 14.45. EI-MS: 319 (45, Mþ), 302 (90), 276 (8), 246 (100), 230 (50), 200 (10), 157 (6), 128
(12), 77 (3). HR-EI-MS: 319.3093 (Mþ, C16H17NO6þ ; calc. 319.1056).
Ethyl 4-Acetyl-2,3-dihydro-5-methyl-3-(4-nitrophenyl)furan-2-carboxylate (14j13). Yield: 15%
1
(0.14 g). Yellow oil. H-NMR (250 MHz, CDCl3): 8.19 – 7.16 (m, 4 H); 5.33 (d, J ¼ 10.6, 1 H); 4.72 (d,
J ¼ 10.6, 1 H); 4.28 – 4.23 (m, 2 H); 2.45 (s, 3 H); 2.04 (s, 3 H); 1.30 – 1.26 (m, 3 H). 13C-NMR (CDCl3,
125 MHz): 193.1; 171.2; 167.1; 147.7; 146.1; 129.6 (2 C); 123.7 (2 C); 117.0; 83.3; 62.5; 51.8; 29.6; 21.2; 14.3.

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Helvetica Chimica Acta – Vol. 95 (2012)
GC/MS: tR 15.15. EI-MS: 319 (1, Mþ), 304 (40), 276 (18), 260 (20), 246 (75), 232 (100), 204 (90), 185
(55), 158 (15), 128 (30), 115 (10), 77 (5). HR-EI-MS: 319.3101 (Mþ, C16H17NO6þ ; calc. 319.1056).
Ethyl 4-Acetyl-5-ethoxy-2,3-dihydro-3-phenylfuran-2-carboxylate (14k13). Yield: 7% (0.06 g). Yellow
oil. 1H-NMR (250 MHz, CDCl3): 7.40 – 7.24 (m, 5 H); 4.82 (d, J ¼ 5.1, 1 H); 4.39 (d, J ¼ 5.1, 1 H); 4.28 (q,
J ¼ 7.2, 2 H); 4.00 (q, J ¼ 7.3, 2 H); 2.39 (s, 3 H); 1.31 – 1.24 (m, 3 H); 1.06 (t, J ¼ 7.2, 3 H). 13C-NMR
(CDCl3, 125 MHz): 169.0; 167.4; 163.9; 141.6; 129.4; 128.7; 127.9; 127.6; 126.1; 84.8; 81.1; 60.7; 60.6; 58.6;
51.7; 13.1; 13.0. GC/MS: tR 12.68. EI-MS: 304 (30, Mþ), 258 (60), 230 (100), 202 (40), 185 (70), 158 (25),
128 (27), 115 (27), 77 (5). HR-EI-MS: 304.3385 (Mþ, C17H20O5þ ; calc. 304.1311).
Ethyl 4-Acetyl-5-ethoxy-2,3-dihydro-3-(3-nitrophenyl)furan-2-carboxylate (14l13). The product could
not be isolated from the crude mixture. GC/MS: tR 14.45. EI-MS: 349 (45, Mþ), 332 (100), 304 (25), 275
(22), 247 (26), 230 (90), 204 (10), 128 (12), 77 (3).
Ethyl 4-Acetyl-5-ethoxy-2,3-dihydro-3-(4-nitrophenyl)furan-2-carboxylate (14m13). The product
could not be isolated from the crude mixture. GC/MS: tR 15.49. EI-MS: 349 (15, Mþ), 303 (85), 275
(100), 247 (75), 230 (76), 205 (10), 128 (13), 77 (3).
Ethyl 4-Acetyl-5-ethoxy-2,3-dihydro-3-[(E/Z)-2-phenylethenyl]furan-2-carboxylate (14n13). The
1
product was isolated as a mixture of two isomers together with 15n13 and 15n’13. H-NMR (250 MHz,
CDCl3): of 14n13: 7.48 – 7.12 (m, 5 H); 6.60 – 6.43 (m, 1 H); 6.02 – 5.94 (m, 1 H); 5.14 (d, J ¼ 8.8, 1 H);
4.40 – 4.05 (m, 4 H); 3.55 – 3.45 (m, 1 H); 2.45 (s, 3 H); 1.43 – 1.10 (m, 6 H); of: 14n’13: 7.48 – 7.12 (m, 5 H);
6.60 – 6.43 (m, 1 H); 6.02 – 5.94 (m, 1 H); 5.14 (d, J ¼ 8.8, 1 H); 4.40 – 4.05 (m, 4 H); 3.55 – 3.45 (m, 1 H);
2.40 (s, 3 H); 1.43 – 1.10 (m, 6 H). GC/MS: tR 14.07 and 14.10. EI-MS (same for two isomers): 330 (70,
Mþ), 284 (65), 211 (100), 183 (45), 167 (47), 141 (44), 115 (40), 91 (30),77 (28).
Ethyl 6-Acetyl-2,3-dihydro-7-methyl-3-phenyloxepine-2-carboxylate (16e13). The product could not
be isolated from the crude mixture. GC/MS: tR 13.54. EI-MS: 300 (80, Mþ), 257 (60), 227 (40), 211 (42),
199 (100), 185 (70), 155 (65), 141 (66), 137 (90), 127 (45), 115 (75), 91 (45), 77 (44).
Ethyl 4-Acetyl-1,3-dihydro-3-methyl-2-benzoxepine-1-carboxylate (15f13). The product could not be
isolated from the crude mixture. GC/MS: tR 13.27. EI-MS: 274 (1, Mþ), 259 (70), 231 (30), 201 (60), 185
(20), 159 (70), 141 (100), 128 (25), 115 (55), 77 (10).
Ethyl 4-Acetyl-1,3-dihydro-9-methoxy-3-methyl-2-benzoxepine-1-carboxylate (15g13). The product
was isolated together with 14g13. 1H-NMR (CDCl3, 250 MHz): 7.43 (s, 1 H); 7.34 – 6.58 (m, 3 H); 5.11 (q,
J ¼ 6.4, 1 H); 5.05 (s, 1 H); 4.31 – 4.12 (m, 2 H); 3.75 (s, 3 H); 2.45 (s, 3 H); 1.29 (d, J ¼ 7.2, 3 H); 0.86 (t,
J ¼ 7.1, 3 H). GC/MS: tR 14.05. EI-MS: 289 (12), 261 (12), 231 (100), 189 (40) 171 (25), 145 (15), 115 (18),
91 (5).
Ethyl 4-Acetyl-1,3-dihydro-7-methoxy-3-methyl-2-benzoxepine-1-carboxylate (15g’13). The product
could not be isolated from the crude mixture. GC/MS: tR 14.37. EI-MS: 304 (2, Mþ), 289 (12), 261 (5), 231
(100), 189 (55) 171 (25), 161 (25), 145 (15), 115 (18), 91 (5).
Ethyl 4-Acetyl-1,3-dihydro-8-methoxy-3-methyl-2-benzoxepine-1-carboxylate (15h13). The product
could not be isolated from the crude mixture. GC/MS: tR 14.42. EI-MS: 304 (10, Mþ), 289 (90), 261 (65),
217 (50), 187 (70), 171 (100), 145 (68), 115 (13), 77 (3).
Ethyl 4-Acetyl-1,3-dihydro-3-methyl-9-nitro-2-benzoxepine-1-carboxylate (15i13). Yield 12%
1
(0.11 g). Yellow oil. H-NMR (CDCl3, 250 MHz): 7.80 (d, J ¼ 7.9, 1 H); 7.65 (d, J ¼ 7.3, 1 H); 7.51 (dd,
J ¼ 7.9, 7.3, 1 H); 7.40 (s, 1 H); 5.22 (s, 1 H); 4.23 – 4.15 (m, 3 H); 2.48 (s, 3 H); 1.40 (d, J ¼ 6.4, 3 H); 1.28
(t, J ¼ 7.1, 3 H ) . 13C-NMR (CDCl3, 125 MHz): 199.1; 167.9; 149.0; 137.7; 136.2; 135.9 (2 C); 133.6; 128.9;
124.8; 79.0; 75.4; 62.1; 27.3; 20.6; 14.1. GC/MS: tR 14.69. EI-MS: 319 (1, Mþ), 302 (3), 276 (5), 246 (100),
218 (10), 186 (40), 156 (45), 128 (20), 77 (6). HR-EI-MS: 319.3083 (Mþ, C17H16NO6þ ; calc. 319.1056).
Ethyl 4-Acetyl-1,3-dihydro-3-methyl-8-nitro-2-benzoxepine-1-carboxylate (15j13). The product could
not be isolated from the crude mixture. GC/MS: tR 15.15. EI-MS: 319 (1, Mþ), 304 (40), 276 (18), 260
(20), 246 (75), 232 (100), 204 (90), 185 (55), 158 (15), 128 (30), 115 (10), 77 (5).
Diethyl 3-Methyl-1,3-dihydro-2-benzoxepine-1,4-dicarboxylate (15k13). Yield: 10% (0.09 g). Yellow
oil. 1H-NMR (250 MHz, CDCl3): 7.65 (s, 1 H); 7.44 (d, J ¼ 7.1, 1 H); 7.37 – 7.14 (m, 2 H); 7.02 (d, J ¼ 7.3,
1 H); 5.22 (q, J ¼ 6.4, 1 H); 5.13 (s, 1 H); 4.40 – 4.38 (m, 2 H); 4.30 – 4.26 (m, 2 H); 1.40 – 1.32 (m, 6 H).
13C-NMR (CDCl3, 125 MHz): 164.3; 163.5; 138.2; 135.9; 131.8 (2 C); 128.7; 127.8; 127.5; 123.4; 77.8; 66.9;
60.4; 60.0; 28.2; 13.3; 13.1. GC/MS: tR 13.75. EI-MS: 304 (10, Mþ), 258 (24), 231 (100), 185 (25), 157 (90),
129 (75), 115 (30), 77 (8). HR-EI-MS: 304.3359 (Mþ, C17H20O5þ ; calc. 304.1311).

Helvetica Chimica Acta – Vol. 95 (2012)
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Diethyl 1,3-Dihydro-3-methyl-9-nitro-2-benzoxepine-1,4-dicarboxylate or Diethyl 1,3-Dihydro-3-
methyl-7-nitro-2-benzoxepine-1,4-dicarboxylate (15l13). The product could not be isolated from the
crude mixture. GC/MS: tR 15.88. EI-MS: 349 (3, Mþ), 301 (35), 276 (100), 262 (7), 216 (15), 158 (20), 128
(30), 77 (4).
Diethyl 1,3-Dihydro-3-methyl-8-nitro-2-benzoxepine-1,4-dicarboxylate (15m13). The product could
not be isolated from the crude mixture. GC/MS: tR 15.49. EI-MS: 349 (2, Mþ), 303 (25), 276 (100), 262
(7), 230 (50), 202 (95), 156 (25), 128 (28), 115 (8), 77 (4).
Diethyl 2,3-Dihydro-7-methyl-3-phenyloxepine-2,6-dicarboxylate (16n13). The product could not be
isolated from the crude mixture. GC/MS: tR 14.18. EI-MS: 330 (5, Mþ), 291 (35), 245 (40), 217 (65), 192
(100), 171 (30), 115 (43), 105 (50), 91 (30), 77 (28).
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Received January 4, 2012