Radical cyclization of fluorinated 1,3-dicarbonyl compounds with dienes using manganese(III) acetate and synthesis of fluoroacylated 4,5-dihydrofurans

Article abstract of DOI:10.1002/hlca.201100105

Radical cyclizations of fluorinated 1,3-dicarbonyl compounds with dienes mediated by Mn(OAc)₃ afforded 4,5-dihydrofurans containing difluoroacetyl, trifluoroacetyl, or heptafluorobutanoyl groups in good-to-excellent yields. Additionally, 2-(dif

Full text of DOI:10.1002/hlca.201100105

Helvetica Chimica Acta – Vol. 94 (2011)
2027
Radical Cyclization of Fluorinated 1,3-Dicarbonyl Compounds with Dienes
Using Manganese(III) Acetate and Synthesis of Fluoroacylated
4,5-Dihydrofurans
by Mehmet Yılmaz*a), E. Vildan Burgaz Yılmazb), and A. Tarık Pekelb)
a) Department of Chemistry, Faculty of Arts and Sciences, Kocaeli University, TR-41380 Umuttepe,
Kocaeli (fax: þ 90 – 2623032003; e-mail: mehmet.yilmaz@kocaeli.edu.tr)
b) Ankara University, Science Faculty, Department of Chemistry, TR-06100 Tandogan, Ankara
Radical cyclizations of fluorinated 1,3-dicarbonyl compounds with dienes mediated by Mn(OAc)3
afforded 4,5-dihydrofurans containing difluoroacetyl, trifluoroacetyl, or heptafluorobutanoyl groups in
good-to-excellent yields. Additionally, 2-(difluoromethyl)-4,5-dihydrofurans and a 4,7-dihydrooxepin
derivative were obtained as unexpected products in the reaction of 4,4-difluoro-1-phenylbutane-1,3-
dione with 1,3-diphenylbuta-1,3-diene. The radical cyclization of symmetrical dienes such as 2,3-
dimethylbuta-1,3-diene and 1,4-diphenylbuta-1,3-diene with 1,3-diketones furnished the corresponding
products in low yields. However, treatment of 1-phenylbuta-1,3-diene with 1,3-dicarbonyl compounds
afforded 4,5-dihydrofurans containing fluoroacyl groups. The radical cyclizations with 3-methyl-1-
phenylbuta-1,3-diene and 1,3-diphenylbuta-1,3-diene led to 4,5-dihydrofurans in good yields, since Me
and Ph groups at C(3) of these dienes increase the stability of the radical intermediate.
Introduction. – The use of F-atom and fluoroalkyl groups in the synthesis of organic
compounds is developing due to their unique electronic effects and biological
properties. Thus, fluorinated organic compounds containing the difluoromethyl and
trifluoromethyl groups have received considerable attention in the medicinal and
agricultural chemistry [1]. Several difluoromethyl and trifluoromethyl ketones have
been found to exhibit enzyme-inhibition properties [2] and antimicrobial activities [3].
Moreover, some trifluoromethyl ketones have been found to act as cytotoxic agents
against human tumor cell [4].
Traditionally, methods for the synthesis of F-containing organic compounds are
direct fluorination and fluoroalkylation [5]. One possible approach for the synthesis of
trifluoromethyl ketones containing dihydrofurans would be the cyclization of suitable
fluorinated 1,3-dicarbonyl compounds with an unsaturated system mediated by
transition metal salts (Mn3þ, Ce4þ, Agþ, etc.). Among these metal salts, Mn(OAc)3
[6] and (NH4)2Ce(NO3)6 [6h][7] are very important radical oxidants in the organic
synthesis for the construction of CꢀC bonds.
Dihydrofurans are a significant class of compounds, since they show a wide range of
biological activities and form the basic structure of many natural compounds [8]. Our
research group has been studying the synthesis of dihydrofuran derivatives by the
radical cyclization of various 1,3-dicarbonyl compounds and 3-oxopropanenitriles with
alkenes, alkynes, unsaturated amides, and dienes [9].
ꢀ 2011 Verlag Helvetica Chimica Acta AG, Zꢁrich

2028
Helvetica Chimica Acta – Vol. 94 (2011)
Previously, we described the synthesis of 4,5-dihydro-3-(trifluoroacetyl)furans and
3-[4,5-dihydrofuran-2(3H)-ylidene]-1,1,1-trifluoroacetones by the treatments of tri-
fluoromethyl 1,3-diketones with alkenes [9e]. In this study, we investigated the radical
cyclization of various di-, tri-, and heptafluorinated 1,3-diketones 1a – 1g with
conjugated dienes 2a – 2e using Mn(OAc)3. As a result of these reactions, we obtained
4,5-dihydro-5-(2-phenylethenyl)furans containing difluoroacetyl, trifluoroacetyl, and
heptafluorobutanoyl residues.
Results and Discussions. – Mn(OAc)3 · 2 H2O was prepared in a bipolar packed-bed
reactor by an electrochemical method (see Exper. Part). All fluorinated 1,3-diketones
1a – 1g, 2,3-dimethylbuta-1,3-diene (2a), and 1,4-diphenylbuta-1,3-diene (2b) are
commercial products. The other conjugated dienes, 1-phenylbuta-1,3-diene (2c) [10],
3-methyl-1-phenylbuta-1,3-diene (2d) [11], and 1,3-diphenylbuta-1,3-diene (2e) [12]
were synthesized as described in literature. All radical cyclizations were performed at a
1.2 :1:2.5 molar ratio (1/2/Mn(OAc)3) under a N2 atmosphere in AcOH. All
compounds were purified by column chromatography or preparative TLC and
1
characterized by IR, H-, 13C-, and 19F-NMR spectroscopy, mass spectrometry, and
microanalysis.
The mechanism proposed for the radical cyclization of conjugated dienes with
fluorinated 1,3-diketones is presented in Scheme 1. According to this mechanism, the
reaction of enol forms of the 1,3-diketones 1 with Mn(OAc)3 produce an MnIII-enolate
complex A. While Mn3þ is reduced to Mn2þ, a C-radical B is formed. Then, addition of
diene 2c to the radical forms an allylic radical intermediate C by pathway i. Radical C is
oxidized to the carbocation D by 1 equiv. of Mn(OAc)3, followed by cyclization of D to
give 4,5-dihydro-5-(2-phenylvinyl)furan E. Similarly, the allylic and benzylic radical
intermediates F and G may be formed via pathways ii and iii, respectively. These
intermediates can form 4,5-dihydrofurans I and J as a result of the same two steps as
mentioned above.
The 1H-NMR spectra of the isolated compounds showed signals of two olefinic H-
atoms in (E)-position (J ¼ 16) and of two diastereotopic HꢀC(4) as a doublet of
doublet (J ¼ 14.4 and 8.4), complying with structure E. Thus, we concluded that
products I and J were not formed, and 4,5-dihydro-5-(2-phenylvinyl)furans E are the
only products. Although both intermediate products C and F are allylic radicals, only
the cyclization of C was observed. The explanation is that the radical B added to the
diene to form the more stable allylic radical, which is conjugated with the Ph group.
Radical cyclization of 4,4,4-trifluoro-1-(thiophen-2-yl)butane-1,3-dione (1a) with
the symmetric 2,3-dimethylbuta-1,3-diene (2a) gave 3a in 22% yield (Scheme 2).
Similarly, treatment of 1,4-diphenylbuta-1,3-diene (2b) with 1a and 1d produced 4,5-
dihydro-5-(2-phenylvinyl)furans 3b (30%) and 3c (28%), respectively. Since the
coupling constants between HꢀC(4) and HꢀC(5) of 3b and 3c, Jtrans, are in the range of
3.5 – 4.0, the 2-phenylethenyl and Ph groups are in trans-position. Coupling constants of
cis H-atoms in similar structures are reported as Jcis ¼ 8 – 9 [13] and Jcis ¼ 9.6 – 10 [9g].
Radical cyclizations of thiophen-2-yl-substituted 1,3-dicarbonyl compounds con-
taining a CF3 group (i.e., 1a) and heptafluoropropyl group (i.e., 1b) with 1-phenylbuta-
1,3-diene (2c) as a terminal diene gave 3d and 3e in moderate yields, respectively
(Table, Entries 1 and 2). The reactions of 1c – 1e with 2c gave similar results. 3-(2,2-

Helvetica Chimica Acta – Vol. 94 (2011)
2029
Scheme 1. Mechanism of the Radical Cyclization of 1a – 1g with Dienes
Scheme 2. Radical Cyclization of 1a and 1c with Symmetric Dienes 2a and 2b

2030
Helvetica Chimica Acta – Vol. 94 (2011)
difluoroacetyl)-4,5-dihydrofurans 3i and 3j were obtained via the radical cyclization of
4,4-difluoro-1-(furan-2-yl)buta-1,3-dione (1f) and 4,4-difluoro-1-phenylbutane-1,3-di-
one (1g), respectively, with 2c. The 1H-NMR spectra of 4,5-dihydrofurans 3d and 3f –
3h containing a CF3 group exhibit signals of one of the two HꢀC(4) as dd (J ¼ 14.4 and
8.8 Hz) and of the other one as ddq (J ¼ 14.4, 9.6, and 5J(H,F) ¼ 0.8 Hz). The 13C-NMR
spectra of these compounds show signals for CF3 as quadruplet (1J(C,F) ¼ 287), for
C¼O as quadruplet (2J(C,F) ¼ 53), and for C(4) as quadruplet (4J(C,F) ¼ 2.4 – 3.1 Hz).
The 1H-NMR spectra of 3i and 3j exhibit a triplet (1J(H,F) ¼ 54) for the CF2H groups,
and the 19F-NMR spectra of these compounds show a doublet (1J(F,H) ¼ 54.5) for each
F-atom.
Table. Reactions of 1a – 1g and Buta-1,3-diene Derivatives 2c – 2e
Entry
Ar
RF
1
R
2
3
Yield [%]a)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
Thiophen-2-yl
Thiophen-2-yl
Furan-2-yl
Ph
Naphthalen-2-yl
Furan-2-yl
Ph
Thiophen-2-yl
Thiophen-2-yl
Furan-2-yl
Ph
Naphthalen-2-yl
Furan-2-yl
Ph
CF3
CF3CF2CF2
CF3
CF3
CF3
CF2H
CF2H
CF3
CF3CF2CF2
CF3
1a
1b
1c
1d
1e
1f
1g
1a
1b
1c
1d
1e
1f
1g
1a
1b
1c
1d
H
H
H
H
H
H
H
Me
Me
Me
Me
Me
Me
Me
Ph
Ph
Ph
Ph
2c
2c
2c
2c
2c
2c
2c
2d
2d
2d
2d
2d
2d
2d
2e
2e
2e
2e
3d
3e
3f
3g
3h
3i
3j
3k
3l
3m
3n
3o
3p
3q
3r
54
57
51
52
41
46
48
72
74
67
70
53
58
60
84
88
77
75
CF3
CF3
CF2H
CF2H
CF3
CF3CF2CF2
CF3
Thiophen-2-yl
Thiophen-2-yl
Furan-2-yl
Ph
3s
3t
3u
CF3
a) Yield of isolated product based on the amount of diene.
The radical cyclizations of 3-methyl-1-phenylbuta-1,3-diene (2d) with 1,3-diketones
1a – 1g formed 4,5-dihydrofurans in 53 – 74% yields. However, reactions of diene 2e
containing a Ph group at C(2) with 1a – 1d afforded fluoroacylated 4,5-dihydrofurans in
higher yields (Entries 15 – 18). The best result was obtained in the reaction of 1b with
2e forming 3-(heptafluorobutanoyl)-4,5-dihydrofuran 3s in 88% yield. On the other
hand, the reactions of 2e with 1f and 1g produced 2-(difluoromethyl)-4,5-dihydrofur-
ans 4a and 4b along with 3-(2,2-difluoroacetyl-4,5-dihydrofurans 3v and 3w, respec-
tively. Additionally, the reaction of 2e with 1g also afforded 2,2-difluoro-1-(4,7-

Helvetica Chimica Acta – Vol. 94 (2011)
2031
dihydro-2,5,7-triphenyloxepin-3-yl)ethanone (5) as an unexpected product. The
proposed mechanism for the formation of these products is shown in Scheme 3.
Scheme 3. Reaction Mechanism of the Radical Cyclization of 1f and 1g with 2e
Reaction of 2e with the radical K, obtained from treatment of 1,3-dicarbonyl
compounds with Mn(OAc)3, forms intermediate radical L. This product is oxidized to
carbocation M with Mn(OAc)3, and 2-(difluoromethyl)-4,5-dihydrofurans N (i.e., 4a
and 4b) are formed by subsequent intramolecular cyclization. 3-(Difluoroacetyl)-4,5-
dihydrofurans P (i.e., 3v and 3w) are obtained by intramolecular cyclization of
carbocation O, which is the tautomeric enol form of M. The unexpected product 5 is
obtained by the cyclization of the other mesomeric structure of O. The structures of
compounds of type N and P were deduced on the basis of the chemical shifts and
coupling constants of the C¼O and C(2) atoms in the 13C-NMR spectra. While the
spectrum of N shows a singlet for C¼O, it appears in P at 181 – 183 ppm as triplet (J ¼
24). Similarly, whereas the 13C-NMR spectrum of N exhibits a triplet for C(2) at 156 –
159 ppm (J ¼ 22), that of P shows it as a singlet. On the other hand, the 13C-NMR
spectrum of 5 shows a dd for C¼O at 198.6 (2J(C,F) ¼ 29.7, 20.6), confirming that the
CF2H group is adjacent to C¼O. In addition, the 1H-NMR spectrum of this compound
exhibits only one olefinic H-atom singlet at 6.12 ppm, revealing that the structure of 5

2032
Helvetica Chimica Acta – Vol. 94 (2011)
is not consistent with any of the dihydrofurans shown in Scheme 1. Moreover, the
signals of diastereotopic H-atom at C(4) appear as an AB system with J ¼ 16.8.
According to these results, we concluded that compound 5 is a 4,7-dihydro-2,5,7-
triphenyloxepin derivative.
Conclusions. – In conclusion, radical cyclizations of available fluorinated 1,3-
diketones with conjugated dienes were performed, leading to di-, tri-, and heptafluoro-
acylated 4,5-dihydrofurans. Radical cyclizations of symmetric dienes with 1,3-diketones
afforded dihydrofurans in low yields, whereas the dienes conjugated with a Ph group
gave 4,5-dihydrofurans in higher yields. With dienes 2d and 2e having Me and Ph
groups at C(3), respectively, remarkable increases in yields were observed. This can be
explained by increased stability of intermediate radicals or cations by Me and Ph
groups.
Experimental Part
General. All solvents were dried by standard methods. Column chromatography (CC): silica gel
(SiO2, 230 – 400 mesh; Merck). TLC: anal. aluminium plates coated with SiO2 60 F254–366nm (0.2 mm,
Merck). M.p.: Electrothermal; uncorrected. IR Spectra: Mattson 1000 FT-IR instrument; KBr pellets, in
the 400 – 4000-cmꢀ1 range with 4-cmꢀ1 resolution; n˜ in cmꢀ1. 1H-, 19F- and 13C-NMR spectra: Mercury-400
high performance digital FT-NMR insrument; in CDCl3; d in ppm rel. to Me4Si as internal standard, J in
Hz. LC/ESI-MS: Waters 2695 Alliance Micromass ZQ instrument; in m/z.
Electrochemical Preparation of Mn(OAc)3. Mn(OAc)3 · 2 H2O was obtained in an optimized bipolar
packed-bed reactor by the electrochemical method described in [14]. However, to obtain Mn(OAc)3, this
reactor was modified to a semi-pilot scale. Therefore, a reactor consisting of a glass tube (inner diameter,
52 mm) having 40 rows of graphite rings inside was designed. Each horizontal row in the reactor had
seven graphite rings which were 14 mm long, 16 mm in outer diameter, and 10 mm in inner diameter.
Each horizontal row was insulated from each other by placing a Teflon net with 1-mm thickness beetween
the rows. Applying a potential to the reactor through two graphite rods, 10 cm in lenght and 6 mm in
diameter, placed top and bottom of the reactor, Mn(OAc)2 was oxidized to Mn(OAc)3 by electrolysis. For
this, a soln. containing 100 mm Mn(OAc)2 and 400 mm AcONa was prepared from 95% AcOH. During
applying 180 V cell potential supplied by 500 V/1A dc power unit to the reactor, this colorless soln. was
added to the reactor continuously with a dosage pump with 2.5 l/h flow rate. The red-brown soln.
collected from the bottom of the reactor was recycled through the reactor under the same condition. The
obtained soln. was kept in a closed glass container for 3 – 4 d, until Mn(OAc)3 completely precipitated,
and the color of the soln. disappeared. The red-brown precipitate was filtered through a sintered funnel
(diameter, 120 mm) with porosity 4 and washed with glacial AcOH (2 ꢁ 100 ml) and than Et2O (2 ꢁ
100 ml). The obtained solid was dried under vacuum in a desiccator containing P2O5 for one week.
Yield: 120 g (90%).
General Procedure for Synthesis of 4,5-Dihydrofurans. A soln. of Mn(OAc)3 (0.67 g, 2.5 mmol) in
10 ml of glacial AcOH was heated under N2 at 808, until it dissolved. After the soln. was cooled to 608, a
soln. of 1,3-ketone (1.2 mmol) and diene (1 mmol) in AcOH was added. Then, the temp. was raised to
908. The reaction was completed when the dark brown color of the soln. converted to yellow (30 –
60 min), and disappearance of the diene was monitored by TLC. Then, H2O was added, and the
mixture was extracted with CHCl3 (3 ꢁ 20 ml). The combined org. phases were neutralized with sat.
NaHCO3, dried (anh. Na2SO4), and evaporated. Crude products were purified by CC on SiO2 or prep.
TLC (20 ꢁ 20 cm plates, 2 mm thickness) with hexane/AcOEt 6 :1 as eluant.
1-[4,5-Dihydro-5-methyl-5-(1-methylethenyl)-2-(thiophen-2-yl)furan-3-yl]-2,2,2-trifluoroethanone
(3a). Yield: 0.066 g (22%). Pale yellow oil. IR: 1674 (C¼O), 1600 (C¼C), 1185, 845. 1H-NMR: 1.64 (s,
Me); 1.87 (t, J ¼ 0.56, Me); 3.14 (dd, J ¼ 14.6, 0.9, 1 H, CH2(4)); 3.35 (dd, J ¼ 14.6, 0.5, 1 H, CH2(4)); 4.94

Helvetica Chimica Acta – Vol. 94 (2011)
2033
(t, J ¼ 1.3, 1 H, CH2¼; 5.11 (s, 1 H, CH2¼); 7.20 (dd, J ¼ 5.0, 4.0, 1 H); 7.68 (dd, J ¼ 5.0, 1.2, 1 H); 8.56 (dd,
J ¼ 4.0, 1.2, 1 H). 19F-NMR: ꢀ 77.3 (s, CF3). 13C-NMR: 18.5 (Me); 25.8 (Me); 40.4 (q, 4J(C,F) ¼ 3.3,
1
C(4)); 91.25 (C(5)); 102.9 (C(3)); 110.8 (C¼); 117.2 (q, J(C,F) ¼ 289.5, CF3); 127.7 (C¼); 131.2, 133.4,
134.9, 146.1 (4 C(thiophene)); 165.6 (C(2)); 174.4 (q, 2J(C,F) ¼ 33.9, C¼O). LC/ESI-MS: 303 (100, [M þ
H]þ). Anal. calc. for C14H13F3O2S (302.31): C 55.62, H 4.33, S 10.61; found: C 55.59, H 4.56, S 10.37.
1-{4,5-Dihydro-4-phenyl-5-[(E)-2-phenylethenyl]-2-(thiophen-2-yl)furan-3-yl}-2,2,2-trifluoroetha-
none (3b). Yield: 0.142 g (30%). Yellow oil. IR: 3061, 1686 (C¼O), 1650 (C¼C), 1550, 1135, 874, 750,
694. 1H-NMR: 4.87 (d, J ¼ 3.5, HꢀC(4)); 5.46 (dd, J ¼ 7.4, 3.5, HꢀC(5)); 6.66 (dd, J ¼ 15.7, 7.5, 1 H); 6.96
(d, J ¼ 15.7, 1 H); 7.49 – 7.72 (m, 11 H); 8.35 (dd, J ¼ 5.0, 1.1, 1 H); 8.87 (dd, J ¼ 3.9, 1.1, 1 H). 19F-NMR:
ꢀ 74.4 (s, CF3). 13C-NMR: 54.7 (d, 4J(C,F) ¼ 2.4, C(4)); 90.3 (C(5)); 93.3 (C(olefin)); 108.5 (C(3)); 119.5
(q, 1J(C,F) ¼ 291.4, CF3); 124.3; 126.6; 128.1; 128.2; 128.8; 129.2; 129.8; 129.9; 130.0; 130.3; 131.8; 135.0;
135.4; 136.7; 137.0; 143.6; 168.2 (C(2)); 177.2 (q, 2J(C,F) ¼ 34.8, C¼O). LC/ESI-MS: 427 (100, [M þ H]þ).
Anal. calc. for C24H17F3O2S (426.45): C 67.59, H 4.02, S 7.52; found: C 67.74, H 3.86, S 7.71.
1-{4,5-Dihydro-2,4-diphenyl-5-[(E)-2-phenylethenyl]furan-3-yl}-2,2,2-trifluoroethanone (3c). Yield:
0.118 g (28%). Yellow oil. IR: 3128, 1677 (C¼O), 1655 (C¼C), 1566, 1526, 1246, 1113, 693, 736.
1H-NMR: 4.55 (d, J ¼ 4.0, HꢀC(4)); 5.22 (dd, J ¼ 7.2, 3.6, HꢀC(5)); 6.45 (dd, J ¼ 16.0, 7.6, 1 H); 6.96 (d,
J ¼ 15.6, 1 H); 7.30 – 7.60 (m, 13 H); 7.89 (m, 2 H). 19F-NMR: ꢀ 73.7 (s, CF3). 13C-NMR: 55.0, 92.9 C(5);
1
110.1 (C(olefin)); 118.1 (q, J(C,F) ¼ 290.0, CF3); 125.5; 127.2; 127.3; 127.9; 128.4; 128.9; 129.0; 129.3;
2
130.0; 132.4; 134.3; 135.7; 142.2; 173.3 (C(2)); 177.2 (q, J(C,F) ¼ 35.9, C¼O). LC/ESI-MS: 421 (100,
[M þ H]þ). Anal. calc. for C26H19F3O2 (420.42): C 74.28, H 4.56; found: C 73.93, H 4.28.
1-{4,5-Dihydro-5-[(E)-2-phenylethenyl]-2-(thiophen-2-yl)furan-3-yl}-2,2,2-trifluoroethanone (3d).
Yield: 0.189 g (54%). Yellow oil. IR: 3122, 1670 (C¼O), 1662 (C¼C), 1567, 1528, 1243, 1032, 750, 693.
1H-NMR: 3.20 (dd, J ¼ 14.8, 8.4, 1 H, CH2(4)); 3.55 (ddd, J ¼ 14.4, 9.6, 0.8, 1 H, CH2(4)); 5.46 (ddd, J ¼
16.4, 8.0, 1.6, HꢀC(5)); 6.34 (dd, J ¼ 16.0, 8.0, 1 H); 6.76 (d, J ¼ 16.0, 1 H); 7.20 (dd, J ¼ 5.2, 4.0, 1 H);
7.32 – 7.46 (m, 5 H); 7.68 (dd, J ¼ 4.8, 1.2, 1 H); 8.57 (dd, J ¼ 4.4, 1.2, 1 H). 19F-NMR: ꢀ 84.0 (s, CF3).
13C-NMR: 35.8 (d, 4J(C,F) ¼ 3.1, C(4)); 84.6 (C(5)); 103.4 (C(3)); 117.5 (q, 1J(C,F) ¼ 289.6, CF3); 126.4;
127.1; 128.1; 128.8; 129.0; 131.1; 133.9; 134.2; 135.4; 135.8; 166.8 (C(2)); 174.8 (q, 2J(C,F) ¼ 34.3, C¼O).
LC/ESI-MS: 351 (100, [M þ H]þ). Anal. calc. for C18H13F3O2S (350.36): C 61.71, H 3.74, S 9.15; found: C
61.87, H 3.44, S 8,92.
1-{4,5-Dihydro-5-[(E)-2-phenylethenyl]-2-(thiophen-2-yl)furan-3-yl}-2,2,3,3,4,4,4-heptafluorobutan-
1-one (3e). Yield: 0.256 g (57%). Yellow oil. IR: 1675 (C¼O), 1661, 1596 (C¼C), 1221, 1051, 749, 690.
1H-NMR: 3.22 (dd, J ¼ 15.2, 8.8, 1 H, CH2(4)); 3.56 (dd, J ¼ 14.8, 9.6, 1 H, CH2(4)); 5.44 (dd, J ¼ 17.2, 8.4,
HꢀC(5)); 6.33 (dd, J ¼ 16.4, 8.0, 1 H); 6.73 (d, J ¼ 16.0, 1 H); 7.18 (td, J ¼ 4.8, 0.8, 1 H); 7.30 (dd, J ¼ 8.0,
1.2, 1 H); 7.34 (t, J ¼ 7.2, 2 H); 7.42 (d, J ¼ 8.0, 2 H); 7.66 (d, J ¼ 5.2, 1 H); 8.5 (d, J ¼ 4.4, 1 H). 19F-NMR:
ꢀ 80.66 (t, J ¼ 9.4, CF3); ꢀ 118.06 (m, CCF3, CFꢂ2); ꢀ 126.5 (t, J ¼ not determined, CF3CF2CF2).
4
1
2
13C-NMR: 35.6 (t, J(C,F) ¼ 2.4, C(4)); 84.4 (C(5)); 104.9 (C(3)); 109.1 (tqt, J(C,F) ¼ 265.2, J(C,F) ¼
3
1
2
38.1, J(C,F) ¼ not determined, CF3CF2); 110.4 (tt, J(C,F) ¼ 265.9, J(C,F) ¼ 31.3, CF3CF2CF2); 117.7
(qt, 1J(C,F) ¼ 285.7, 2J(C,F) ¼ 33.5, CF3); 126.0; 126.9; 127.8; 128.6; 128.7; 130.9; 133.9; 134.2; 135.4;
135.6; 167.2 (C(2)); 176.8 (t, J(C,F) ¼ 24.4, C¼O). LC/ESI-MS: 451 (100, [M þ H]þ). Anal. calc. for
2
C20H13F7O2S (450.37): C 53.34, H 2.91, S 7.12; found: C 53.56, H 2.68, S 7.25.
1-{4,5-Dihydro-5-[(E)-2-phenylethenyl][2,2’-bifuran]-3-yl}-2,2,2-trifluoroethanone (3f). Yield:
0.171 g (51%). Light yellow solid. M.p. 101 – 1038. IR: 3028, 1665 (C¼O), 1566 (C¼C), 1532, 1263,
1063, 749, 693. 1H-NMR: 3.20 (dd, J ¼ 14.4, 8.8, 1 H, CH2(4)); 3.55 (dd, J ¼ 14.4, 9.6, 1 H, CH2(4)); 5.50
(ddd, J ¼ 16.4, 8.8, 0.8, HꢀC(5)); 6.36 (dd, J ¼ 15.6, 8.0, 1 H); 6.61 (dd, J ¼ 4.0, 1.6, 1 H); 6.75 (d, J ¼ 15.6,
1 H); 7.30 – 7.43 (m, 5 H); 7.65 (t, J ¼ 0.8, 1 H); 7.68 (d, J ¼ 3.6, 1 H). 19F-NMR: ꢀ 74.3 (s, CF3).
13C-NMR: 35.2 (d, 4J(C,F) ¼ 3.1, C(4)); 85.3 (C(5)); 103.8 (C(3)); 112.9; 117.3 (q, 1J(C,F) ¼ 289.6, CF3);
122.5; 126.0; 127.1; 128.8; 129.0; 131.1; 134.8; 135.8; 144.4; 146.8; 161.9; 170.1 (C(2)); 174.2 (q, 2J(C,F) ¼
34.3, C¼O). LC/ESI-MS: 335 (100, [M þ H]þ). Anal. calc. for C18H13F3O3 (334.29): C 64.67, H 3.92;
found: C 64.40, H 4.18.
1-{4,5-Dihydro-2-phenyl-5-[(E)-2-phenylethenyl]furan-3-yl}-2,2,2-trifluoroethanone (3g). Yield:
0.179 g (52%). Light-yellow solid. M.p. 64 – 668. IR: 3029, 1697 (C¼O), 1670 (C¼C), 1534, 1200, 1133,
751, 692. 1H-NMR: 3.23 (dd, J ¼ 14.4, 8.4, 1 H, CH2(4)); 3.56 (ddq, J ¼ 14.8, 10.0, 0.8, 1 H, CH2(4)); 5.52
(ddd, J ¼ 18.0, 8.8, 0.8, HꢀC(5)); 6.40 (dd, J ¼ 16.0, 8.0, 1 H); 6.76 (d, J ¼ 15.6, 1 H); 7.32 – 7.53 (m, 8 H);

2034
Helvetica Chimica Acta – Vol. 94 (2011)
7.87 (m, 2 H). 19F-NMR: ꢀ 76.4 (s, CF3). 13C-NMR: 36.0 (d, 4J(C,F) ¼ 3.0, C(4)); 84.9 (C(5)); 105.1
(C(3)); 117.2 (q, 1J(C,F) ¼ 289.5, CF3); 126.4; 127.1; 128.2; 128.8; 129.0; 129.2; 129.8; 123.3; 134.4; 135.8;
173.7 (C(2)); 175.4 (q, 2J(C,F) ¼ 34.3, C¼O). LC/ESI-MS: 345 (100, [M þ H]þ). Anal. calc. for
C20H15F3O2 (344.33): C 69.76, H 4.39; found: C 69.47, H 4.54.
1-{4,5-Dihydro-2-(naphthalen-2-yl)-5-[(E)-2-phenylethenyl]furan-3-yl}-2,2,2-trifluoroethanone
(3h). Yield: 0.162 g (41%). Pale yellow oil. IR: 3060, 1683 (C¼O), 1663 (C¼C), 1554, 1492, 1178, 1096,
746, 691. 1H-NMR: 3.27 (dd, J ¼ 14.4, 8.4, 1 H, CH2(4)); 3.60 (ddq, J ¼ 14.4, 9.6, 0.8, 1 H, CH2(4)); 5.55
(ddd, J ¼ 17.2, 9.2, 1.2, HꢀC(5)); 6.43 (dd, J ¼ 16.0, 8.0, 1 H); 6.77 (d, J ¼ 16.0, 1 H); 7.33 (tt, J ¼ 7.2, 1.6,
1 H); 7.39 (t, J ¼ 7.6, 2 H); 7.47 (dt, J ¼ 6.8, 1.6, 2 H); 7.52 – 7.61 (m, 2 H); 7.87 (dd, J ¼ 4.8, 1.6, 2 H); 7.95
(d, J ¼ 8.0, 1 H); 8.51 (s, 1 H). 19F-NMR: ꢀ 76.35 (s, CF3). 13C-NMR: 35.8 (q, 4J(C,F) ¼ 3.0, C(4)); 84.7
(C(5)); 105.0 (C(3)); 120.0 (q, 1J(C,F) ¼ 289.6, CF3); 125.6; 126.1; 126.6; 126.8; 127.5; 127.7; 128.1; 128.6;
128.7; 129.2; 131.1; 132.3; 134.2; 135.0; 135.6; 173.5 (C(2)); 175.4 (q, 2J(C,F) ¼ 34.3, C¼O). LC/ESI-MS:
395 (100, [M þ H]þ). Anal. calc. for C24H17F3O2 (394.39): C 73.09, H 4.34; found: C 73.36, H 4.58.
1-{4,5-Dihydro-5-[(E)-2-phenylethenyl][2,2’-bifuran]-3-yl}-2,2-difluoroethanone (3i). Yield:
1
0.145 g (46%). Pale yellow oil. IR: 3029, 1661, 1524, 1209, 749, 719, 692. H-NMR: 3.19 (dd, J ¼ 14.8,
8.4, 1 H, CH2(4)); 3.53 (dd, J ¼ 14.8, 10.0, 1 H, CH2(4)); 5.46 (ddd, J ¼ 17.6, 8.4, 1.2, HꢀC(5)); 6.0 (t,
2J(H,F) ¼ 54.0, 1 H); 6.34 (dd, J ¼ 15.6, 7.2, 1 H); 6.59 (dd, J ¼ 4.0, 2.0, 1 H); 6.74 (d, J ¼ 16.0, 1 H); 7.28
(tt, J ¼ 7.6, 1.2, 1 H); 7.33 (td, J ¼ 7.2, 1.6, 2 H); 7.41 (dt, J ¼ 7.2, 1.2, 2 H); 7.62 (d, J ¼ 1.2, 1 H); 8.15 (d, J ¼
4.0, 1 H). 19F-NMR: ꢀ 125.6 (d, 2J(F,H) ¼ 53.0, 1 F); ꢀ 125.7 (d, 2J(F,H) ¼ 53.0, 1 F). 13C-NMR: 35.2 (t,
4J(C,F) ¼ 3.8, C(4)); 84.6 (C(5)); 105.6 (C(3)); 111.4 (t, 1J(C,F) ¼ 250.7, CHF2); 112.5; 120.5; 126.2;
126.8; 128.5; 128.7; 134.2; 133.7; 144.3; 146.0; 159.0 (C(2)); 181.7 (t, 2J(C,F) ¼ 24.4, C¼O). LC/ESI-MS:
317 (100, [M þ H]þ). Anal. calc. for C18H14F2O3 (316.30): C 68.35, H 4.46; found: C 68.67, H 4.23.
1-{4,5-Dihydro-2-phenyl-5-[(E)-2-phenylethenyl]furan-3-yl}-2,2-difluoroethanone (3j). Yield:
1
0.157 g (48%). Pale-yellow oil. IR: 3058, 1736 (C¼O), 1673 (C¼C), 1595, 747, 695. H-NMR: 3.17 (dd,
J ¼ 14.8, 8.8, 1 H, CH2(4)); 3.50 (dd, J ¼ 14.8, 10.4, 1 H, CH2(4)); 5.47 (dd, J ¼ 18.0, 8.0, HꢀC(5)); 5.74 (t,
2J(H,F) ¼ 54.0, 1 H); 6.36 (dd, J ¼ 16.0, 7.6, 1 H); 6.73 (d, J ¼ 16.0, 1 H); 7.30 (t, J ¼ 7.2, 1 H); 7.35 (t, J ¼
6.8, 2 H); 7.42 – 7.48 (m, 4 H); 7.52 (t, J ¼ 7.2, 1 H); 7.71 (dd, J ¼ 7.2, 1.2, 2 H). 19F-NMR: ꢀ 125.1 (d,
2J(F,H) ¼ 54.5, 1 F); ꢀ 125.25 (d, 2J(F,H) ¼ 54.5, 1 F). 13C-NMR: 36.0 (C(4)); 84.4 (C(5)); 103.4 (C(3));
109.2 (t, 1J(C,F) ¼ 249.9, CHF2); 109.0; 126.5; 126.8; 128.3; 128.5; 128.7; 129.3; 129.5; 131.8; 133.8; 135.7;
170.7 (C(2)); 183.1 (t, 2J(C,F) ¼ 24.4, C¼O). LC/ESI-MS: 327 (100, [M þ H]þ). Anal. calc. for
C20H16F2O2 (326.34): C 73.61, H 4.94; found: C 73.50, H 4.84.
1-{4,5-Dihydro-5-methyl-5-[(E)-2-phenylethenyl]-2-(thiophen-2-yl)furan-3-yl}-2,2,2-trifluoroetha-
none (3k). Yield: 0.262 g (72%). Pale yellow solid. M.p. 79 – 818. IR: 3028, 1683 (C¼O), 1653 (C¼C),
1
1637, 1243, 748, 694. H-NMR: 1.75 (s, Me); 3.28 (dd, J ¼ 14.4, 1 H, CH2(4)); 3.44 (dd, J ¼ 14.4, 1 H,
CH2(4)); 6.40 (d, J ¼ 16.0, 1 H); 6.70 (d, J ¼ 16.4, 1 H); 7.22 (td, J ¼ 4.8, 0.8, 1 H); 7.28 (d, J ¼ 7.2, 1 H);
7.35 (t, J ¼ 7.6, 2 H); 7.42 (d, J ¼ 7.2, 2 H); 7.70 (dd, J ¼ 5.2, 0.8, 1 H); 8.60 (dd, J ¼ 3.2, 0.8, 1 H). 19F-NMR:
ꢀ 76.4 (s, CF3). 13C-NMR: 26.6; 41.79; 89.3 (C(5)); 103.1 (C(3)); 117.5 (q, 1J(C,F) ¼ 289.6, CF3); 127.0;
128.0; 128.4; 128.6; 128.9; 129.5; 131.3; 133.8; 135.4; 136.1; 165.8 (C(2)); 174.5 (q, 2J(C,F) ¼ 33.5, C¼O).
LC/ESI-MS: 365 (100, [M þ H]þ). Anal. calc. for C19H15F3O2S (364.38): C 62.63, H 4.15, S 8.80; found: C
62.71, H 4.46, S 8.63.
1-{4,5-Dihydro-5-methyl-5-[(E)-2-phenylethenyl]-2-(thiophen-2-yl)furan-3-yl}-2,2,3,3,4,4,4-hepta-
fluorobutan-1-one (3l). Yield: 0.343 g (74%). Yellow oil. IR: 1650 (C¼O), 1615 (C¼C), 1586, 1062, 747,
692. 1H-NMR: 1.77 (s, Me); 3.26 (d, J ¼ 14.8, 1 H, CH2(4)); 3.42 (d, J ¼ 14.8, 1 H, CH2(4)); 6.36 (d, J ¼
16.0, 1 H); 6.66 (d, J ¼ 16.0, 1 H); 7.18 (t, J ¼ 4.8, 1 H); 7.25 (t, J ¼ 7.6, 1 H); 7.32 (t, J ¼ 7.2, 2 H); 7.38 (dd,
J ¼ 7.2, 1.6, 2 H); 7.66 (d, J ¼ 5.2, 1 H); 8.52 (d, J ¼ 3.6, 1 H). 19F-NMR: ꢀ 80,6 (t, J ¼ 9.0, CF3); ꢀ 118.06
(q, J ¼ 9.4, CF3CF2); ꢀ 126.5 (t, J ¼ not determined, CF3CF2CF2). 13C-NMR: 26.2; 41.6 (t, 4J(C,F) ¼ 6.1,
C(4)); 89.1 (t, 5J(C,F) ¼ 2.3, C(5)); 104.7 (C(3)); 109.1 (tqt, 1J(C,F) ¼ 265.1, 2J(C,F) ¼ 38.1, 3J(C,F) ¼ not
1
2
1
determined, CF3CF2); 110.4 (tt, J(C,F) ¼ 266.7, J(C,F) ¼ 31.3, CF3CF2CF2); 117.7 (qt, J(C,F) ¼ 285.8,
2J(C,F) ¼ 33.5, CF3); 126.7; 127.8; 128.2; 128.7; 129.4; 131.1; 131.2; 133.7; 135.3; 135.9; 166.5 (C(2)); 177.0
(q, 2J(C,F) ¼ 24.4, C¼O). LC/ESI-MS: 465 (100, [M þ H]þ). Anal. calc. for C21H15F7O2S (464.40): C
54.31, H 3.26, S 6.90; found: C 54.60, H 3.42, S 7.17.
1-{4,5-Dihydro-5-methyl-5-[(E)-2-phenylethenyl][2,2’-bifuran]-3-yl}-2,2,2-trifluoroethanone (3m).
Yield: 0.233 g (67%). Pale yellow solid. M.p. 92 – 948. IR: 3030, 1673 (C¼O), 1666, 1569 (C¼C), 1536,

Helvetica Chimica Acta – Vol. 94 (2011)
2035
1126, 743, 731, 688. 1H-NMR: 1.77 (s, Me); 3.25 (d, J ¼ 14.4, 1 H, CH2(4)); 4.20 (d, J ¼ 14.8, 1 H, CH2(4));
6,41 (d, J ¼ 16.0, 1 H); 6.62 (dd, J ¼ 3.6, 1.6, 1 H); 6.70 (d, J ¼ 16.0, 1 H); 7.27 (t, J ¼ 7.6, 1 H); 7.33 (t, J ¼
8.0, 2 H); 7.42 (d, J ¼ 7.2, 2 H); 7.67 (d, J ¼ 1.6, 1 H); 8.43 (d, J ¼ 3.6, 1 H). 19F-NMR: ꢀ 74.0 (s, 3 F).
4
13C-NMR: 26.6; 41.2 (d, J(C,F) ¼ 3.1, C(4)); 90.1 (C(5)); 103.5 (C(3)); 112.9; 117.4 (q, 1J(C,F) ¼ 289.5,
2
CF3); 122.5; 127.0; 128.5; 128.9; 129.8; 131.0; 136.1; 144.6; 146.7; 161.0 (C(2)); 174.0 (q, J(C,F) ¼ 33.6,
C¼O). LC/ESI-MS: 349 (100, [M þ H]þ). Anal. calc. for C19H15F3O3 (348.32): C 65.52, H 4.34; found: C
65.21, H 4.56.
1-{4,5-Dihydro-5-methyl-2-phenyl-5-[(E)-2-phenylethenyl]furan-3-yl}-2,2,2-trifluoroethanone (3n).
Yield: 0.251 g (70%). Colorless solid. M.p. 87 – 898. IR: 3027, 1656 (C¼O), 1605 (C¼C), 1536, 1049, 747,
694. 1H-NMR: 1.77 (s, Me); 3.25 (d, J ¼ 14.4, 1 H, CH2(4)); 3.43 (d, J ¼ 14.8, 1 H, CH2(4)); 6.42 (d, J ¼
16.4, 1 H); 6.72 (d, J ¼ 16.0, 1 H); 7.30 (t, J ¼ 7.2, 1 H); 7.37 (t, J ¼ 7.2, 2 H); 7.45 – 7.49 (m, 4 H); 7.52 (tt,
J ¼ 7.2, 1.2, 1 H); 7.87 (dd, J ¼ 6.8, 1.2, 2 H). 19F-NMR: ꢀ 76.2 (s, CF3). 13C-NMR: 26.7; 42.0; 89.6 (C(5));
104.7 (C(3)); 117.1 (q, 1J(C,F) ¼ 290.3, CF3); 127.0; 128.2; 128.5; 129.0; 129.6; 129.8; 131.4; 132.2; 136.1;
172.7 (C(2)); 175.4 (q, 2J(C,F) ¼ 34.3, C¼O). LC/ESI-MS: 359 (100, [M þ H]þ). Anal. calc. for
C21H17F3O2 (358.35): C 70.38, H 4.78; found: C 70.45, H 4.54.
1-{4,5-Dihydro-5-methyl-2-(naphthalen-2-yl)-5-[(E)-2-phenylethenyl]furan-3-yl}-2,2,2-trifluoroetha-
none (3o). Yield: 0.216 g (53%). Pale-yellow oil. IR: 3029, 2954, 1623 (C¼O), 1600 (C¼C), 1203, 748,
688. 1H-NMR: 1.76 (s, Me); 3.25 (d, J ¼ 14.8, 1 H, CH2(4)); 3.43 (d, J ¼ 14.4, 1 H, CH2(4)); 6.42 (d, J ¼
16.0, 1 H); 6.70 (d, J ¼ 16.0, 1 H); 7.25 (t, J ¼ 7.6, 1 H); 7.33 (t, J ¼ 7.2, 2 H); 7.40 (d, J ¼ 7.2, 2 H); 7.52 (m,
2 H); 7.83 (d, J ¼ 8.0, 2 H); 7.85, (s, 1 H); 7.91 (d, J ¼ 8.0, 1 H); 8.48 (s, 1 H). 19F-NMR: ꢀ 76.2 (s, CF3).
1
13C-NMR: 26.4; 41.8 (d, 4J(C,F) ¼ 3.0, C(4)); 89.4 (C(5)); 104.6 (C(3)); 117.0 (q, J(C,F) ¼ 290.4, CF3);
125.6; 126.5; 126.6; 126.7; 127.5; 127.7; 128.0; 128.2; 128.7; 129.2; 129.4; 130.9; 131.1; 132.3; 134.9; 135.9;
2
172.5 (C(2)); 175.8 – 175.8 (q, J(C,F) ¼ 33.6, C¼O). LC/ESI-MS: 409 (100, [M þ H]þ). Anal. calc. for
C25H19F3O2 (408.41): C 73.52, H 4.69; found: C 73.58, H 4.83.
1-{4,5-Dihydro-5-methyl-5-[(E)-2-phenylethenyl][2,2’-bifuran]-3-yl}-2,2-difluoroethanone (3p).
Yield: 0.192 g (58%). Pale-yellow solid. M.p. 67 – 698. IR: 2948, 1623 (C¼O), 1600 (C¼C), 1227, 968,
1
756, 691. H-NMR: 1.73 (s, Me); 3.23 (d, J ¼ 14.4, 1 H, CH2(4)); 3.40 (d, J ¼ 14.8, 1 H, CH2(4)); 6.0 (t,
2J(H,F) ¼ 54.4, CHF2); 6.40 (d, J ¼ 16.4, 1 H); 6.60 (t, J ¼ 1.6, 1 H); 6.67 (d, J ¼ 16.0, 1 H); 7.25 (t, J ¼ 8.0,
1 H); 7.32 (t, J ¼ 7.2, 1 H); 7.64 (s, 1 H); 8.12 (d, J ¼ 3.6, 1 H). 19F-NMR: ꢀ 125.6 (d, 2J(F,H) ¼ 54.1, 2 F).
13C-NMR: 26.5; 41.1 (d, 4J(C,F) ¼ 3.1, C(4)); 89.3 (C(5)); 105.3 (C(3)); 111.4 (t, 1J(C,F) ¼ 251.5, CHF2);
2
112.5; 120.4; 126.7; 128.1; 128.6; 129.3; 131.2; 136.0; 144.5; 146.0; 158.2 (C(2)); 181.8 (t, J(C,F) ¼ 24.4,
C¼O). LC/ESI-MS: 331 (100, [M þ H]þ). Anal. calc. for C19H16F2O3 (330.32): C 69.08, H 4.88; found: C
70.15, H 4.59.
1-{4,5-Dihydro-5-methyl-2-phenyl-5-[(E)-2-phenylethenyl]furan-3-yl}-2,2-difluoroethanone (3q).
Yield: 0.204 g (60%). Pale-yellow oil. IR: 3027, 2978, 1691 (C¼O), 1643 (C¼C), 1235, 966, 748, 693.
1H-NMR: 1.71 (s, Me); 3.18 (d, J ¼ 14.8, 1 H, CH2(4)); 3.36 (d, J ¼ 14.8, 1 H, CH2(4)); 5.7 (t, 2J(H,F) ¼
54.0, 1 H, CHF2); 6.40 (d, J ¼ 16.0, 1 H); 6.67 (d, J ¼ 16.0, 1 H); 7.25 (tt, J ¼ 7.6, 1.2, 1 H); 7.32 (t, J ¼ 7.2,
1 H); 7.40 (dd, J ¼ 6.8, 1.6, 2 H); 7.45 (t, J ¼ 8.0, 2 H); 7.50 (tt, J ¼ 7.2, 1.2, 1 H); 7.71 (dd, J ¼ 7.2, 1.6, 2 H).
19F-NMR: ꢀ 125.1 (d, 2J(F,H) ¼ 54.0, 1 F); ꢀ 125.12 (d, 2J(F,H) ¼ 54.0, 1 F). 13C-NMR: 26.6; 42.0; 89.2
(C(5)); 109.1 (t, 1J(C,F) ¼ 249.1, CHF2); 108.8; 126.7; 128.1; 128.3; 128.7; 129.1; 129.2; 129.8; 131.4; 131.7;
2
136.0; 169.7 (C(2)); 183.2 (t, J(C,F) ¼ 24.4, C¼O). LC/ESI-MS: 341 (100, [M þ H]þ). Anal. calc. for
C21H18F2O2 (340.36): C 74.10, H 5.33; found: C 74.21, H 5.47.
1-{4,5-Dihydro-5-phenyl-5-[(E)-2-phenylethenyl]-2-(thiophen-2-yl)furan-3-yl}-2,2,2-trifluoroetha-
none (3r). Yield: 0.358 g (84%). Yellow oil. IR: 1649 (C¼O), 1623 (C¼C), 1218, 1028, 750, 690.
1H-NMR: 3.72 (d, J ¼ 14.8, 1 H, CH2(4)); 3.81 (d, J ¼ 14.8, 1 H, CH2(4)); 6.52 (d, J ¼ 16.0, 1 H); 6.58 (d,
J ¼ 16.0, 1 H); 7.23 – 7.26 (m, 2 H); 7.30 (tt, J ¼ 7.6, 1.6, 2 H); 7.35 – 7.37 (m, 3 H); 7.42 (t, J ¼ 7.2, 2 H); 7.51
(dt, J ¼ 7.6, 1.6, 2 H); 7.71 (dd, J ¼ 5.2, 1.2, 1 H); 8.65 (dd, J ¼ 4.0, 1.2, 1 H). 19F-NMR: ꢀ 76.0 (s, CF3).
13C-NMR: 41.79 (q, 4J(C,F) ¼ 3.1, C(4)); 91.9 (C(5)); 103.0 (C(3)); 117.2 (q, 1J(C,F) ¼ 289.6, CF3); 125.2;
126.9; 128.0; 128.2; 128.3; 128.6; 128.7; 130.5; 130.7; 131.0; 133.7; 135.2; 135.7; 142.4; 165.2 (C(2)); 174.4
(q, 2J(C,F) ¼ 34.3, C¼O). LC/ESI-MS: 427 (100, [M þ H]þ). Anal. calc. for C24H17F3O2S (426.45): C
67.59, H 4.02, S 7.52; found: C 67.71, H 3.80, S 7.48.
1-{4,5-Dihydro-5-phenyl-5-[(E)-2-phenylethenyl]-2-(thiophen-2-yl)furan-3-yl}-2,2,3,3,4,4,4-hepta-
fluorobutan-1-one (3s). Yield: 0.463 g (88%). Yellow oil. IR: 3025, 1650 (C¼O), 1631 (C¼C), 741, 690.

2036
Helvetica Chimica Acta – Vol. 94 (2011)
1H-NMR: 3.74 (dt, J ¼ 15.2, 1.6, 1 H, CH2(4)); 3.83 (dt, J ¼ 14.8, 1.6, 1 H, CH2(4)); 6.53 (d, J ¼ 16.0, 1 H);
6.58 (d, J ¼ 16.0, 1 H); 7.21 – 7.25 (m, 2 H); 7.29 (tt, J ¼ 7.2, 1.6, 2 H); 7.34 – 7.37 (m, 3 H); 7.41 (tt, J ¼ 7.2,
1.6, 2 H); 7.51 (dt, J ¼ 7.2, 1.6, 2 H); 7.70 (dd, J ¼ 5.2, 1.2, 1 H); 8.61 (dd, J ¼ 4.0, 1.2, 1 H). 19F-NMR:
ꢀ 80.6 (t, J ¼ 9.4, CF3); ꢀ 118.0 (q, J ¼ 9.3, CF3CF2); ꢀ 126.7 (t, J ¼ not determined, CF3CF2CF2).
4
1
2
13C-NMR: 42.0 (q, J(C,F) ¼ 6.1, C(4)); 91.9 (C(5); 104.8 (C(3); 108.8 (tqt, J(C,F) ¼ 265.2, J(C,F) ¼
3
1
2
38.9, J(C,F) ¼ not determined, CF3CF2); 110.4 (tt, J(C,F) ¼ 266.7, J(C,F) ¼ 31.2, CF3CF2CF2); 117.6
(qt, 1J(C,F) ¼ 286.5, 2J(C,F) ¼ 34.2, CF3); 125.2; 126.9; 128.0; 128.2; 128.4; 128.7; 128.8; 130.7; 131.0;
134.0; 135.4; 135.7; 142.3; 165.9 (C(2)); 176.7 (t, 2J(C,F) ¼ 25.1, C¼O). LC/ESI-MS: 527 (100, [M þ H]þ).
Anal. calc. for C26H17F7O2S (526.47): C 59.32, H 3.25, S 6.09; found: C 59.54, H 3.51, S 7.12.
1-{4,5-Dihydro-5-phenyl-5-[(E)-2-phenylethenyl][2,2’-bifuran]-3-yl}-2,2,2-trifluoroethanone (3t).
Yield: 0.316 g (77%). Pale yellow solid. M.p. 97 – 998. IR: 3026, 1648 (C¼O), 1623 (C¼C), 1221, 740,
695. 1H-NMR: 3.68 (d, J ¼ 14.4, 1 H, CH2(4)); 3.79 (d, J ¼ 14.4, 1 H, CH2(4)); 6.54 (d, J ¼ 16.0, 1 H); 6.60
(d, J ¼ 16.0, 1 H); 6.63 (dd, J ¼ 4.0, 1.6, 1 H); 7.23 (t, J ¼ 7.2, 2 H); 7.29 (tt, J ¼ 6.8, 2.0, 2 H); 7.35 (t, J ¼ 8.0,
2 H); 7.41 (t, J ¼ 7.6, 2 H); 7.51 (dt, J ¼ 7.2, 1.6, 2 H); 7.00 (d, J ¼ 1.2, 1 H); 8.41 (d, J ¼ 3.6, 1 H). 19F-NMR:
ꢀ 76.4 (s, CF3). 13C-NMR: 41.8 (q, 4J(C,F) ¼ 3.1, C(4)); 92.8 (d, 5J(C,F) ¼ 1.5, C(5)); 103.5 (C(3)); 113.0;
117.4 (q, 1J(C,F) ¼ 289.5, CF3); 122.6; 125.5; 127.2; 128.4; 128.6; 128.9; 129.0; 130.8; 131.0; 135.9; 142.5;
144.5; 146.9; 160.8 (C(2)); 174.1 (q, 2J(C,F) ¼ 34.3, C¼O). LC/ESI-MS: 411 (100, [M þ H]þ). Anal. calc.
for C24H17F3O3 (410.38): C 70.24, H 4.18; found: C 69.95, H 4.29.
1-{4,5-Dihydro-2,5-diphenyl-5-[(E)-2-phenylethenyl]furan-3-yl}-2,2,2-trifluoroethanone (3u).
1
Yield: 0.315 g (75%). Pale yellow oil. IR: 1667 (C¼O), 1620 (C¼C), 1592, 731, 697. H-NMR: 3.69 (d,
J ¼ 14.8, 1 H, CH2(4)); 3.76 (d, J ¼ 14.8, 1 H, CH2(4)); 6.54 (s, 2 H); 7.22 – 7.50 (m, 13 H); 7.90 (d, J ¼ 6.8,
2 H). 19F-NMR: ꢀ 76.2 (s, CF3). 13C-NMR: 42.1 (q, 4J(C,F) ¼ 3.1, C(4)); 92.2 (C(5)); 104.7 (C(3)); 117.0
(q, 1J(C,F) ¼ 290.4, CF3); 125.2; 126.7; 128.0; 128.2; 128.4; 128.6; 128.7; 129.0; 129.7; 130.5; 130.9; 132.1;
135.7; 142.5; 172.0 (C(2)); 175.0 (q, 2J(C,F) ¼ 34.3, C¼O). LC/ESI-MS: 421 (100, [M þ H]þ). Anal. calc.
for C26H19F3O2 (420.42): C 74.28, H 4.56; found: C 74.13, H 4.30.
1-{4,5-Dihydro-5-phenyl-5-[(E)-2-phenylethenyl][2,2’-bifuran]-3-yl}-2,2-difluoroethanone (3v).
Yield: 0.200 g (51%). Pale-yellow oil. IR: 3082, 1667 (C¼O), 1600 (C¼C), 1597, 1030, 742, 693.
1H-NMR: 3.68 (d, J ¼ 15.2, 1 H, CH2(4)); 3.80 (d, J ¼ 15.2, 1 H, CH2(4)); 6.0 (t, J ¼ 54.4, CF2H); 6.54 (d,
J ¼ 16.0, 1 H); 6.60 (d, J ¼ 16.0, 1 H); 6.61 (dd, J ¼ 3.2, 2.0, 1 H); 7.23 (t, J ¼ 6.4, 2 H); 7.29 (t, J ¼ 7.2, 2 H);
7.35 (tt, J ¼ 7.2, 3.6, 2 H); 7.42 (t, J ¼ 3.6, 1 H); 7.51 (d, J ¼ 7.6, 2 H); 7.67 (d, J ¼ 0.8, 1 H); 8.15 (d, J ¼ 3.6,
2
4
1 H). 19F-NMR: ꢀ 125.5 (d, J(F,H) ¼ 54.5, 2 F). 13C-NMR: 41.8 (t, J(C,F) ¼ 3.0, C(4)); 92.0 (C(5));
105.4 (C(3)); 111.3 (t, 1J(C,F) ¼ 251.5, CF2H); 112.5; 120.5; 125.3; 126.9; 128.0; 128.2; 128.6; 128.7; 130.9;
135.8; 142.6; 144.4; 146.1; 157.8 (C(2)); 181.7 (t, 2J(C,F) ¼ 24.4, C¼O). LC/ESI-MS: 393 (100, [M þ H]þ).
Anal. calc. for C24H18F2O3 (392.40): C 73.46, H 4.62; found: C 73.30, H 4.84.
1-{4,5-Dihydro-2,5-diphenyl-5-[(E)-2-phenylethenyl]furan-3-yl}-2,2-difluoroethanone (3w). Yield:
0.161 g (40%). Pale-yellow oil. IR: 3026, 2943, 1620, 1244, 998, 749, 692. 1H-NMR: 3.72 (d, J ¼ 14.8, 1 H,
CH2(4)); 3.82 (d, J ¼ 14.8, 1 H, CH2(4)); 5.8 (t, J ¼ 53.6, CF2H); 6.60 (d, J ¼ 16.0, 1 H); 6.61 (d, J ¼ 16.0,
1 H); 7.28 (t, J ¼ 7.2, 1 H); 7.34 (d, J ¼ 8.0, 2 H); 7.38 – 7.43 (m, 4 H); 7.45 (t, J ¼ 7.2, 2 H); 7.52 – 7.57 (m,
4 H); 7.83 (dd, J ¼ 6.8, 1.6, 2 H). 19F-NMR: ꢀ 125.03 (d, 2J(F,H) ¼ 54.5, 1 F); ꢀ 125.09 (d, 2J(F,H) ¼ 54.5,
1
1 F). 13C-NMR: 42.6 (C(4)); 92.2 (C(5)); 109.1 (C(3)); 109.4 (t, J(C,F) ¼ 249.9, CHF2); 125.5; 127.1;
128.3; 128.5; 128.6; 128.9; 129.0; 129.6; 130.5; 130.9; 131.5; 132.0; 136.0; 143.0; 169.6 (C(2)); 183.3 (t,
2J(C,F) ¼ 24.3, C¼O). LC/ESI-MS: 403 (100, [M þ H]þ). Anal. calc. for C26H20F2O2 (402.43): C 77.60, H
5.01; found: C 77.77, H 5.32.
{2-(Difluoromethyl)-4,5-dihydro-5-phenyl-5-[(E)-2-phenylethenyl]furan-3-yl}(furan-2-yl)metha-
none (4a). Yield: 0.102 g (26%). Pale-yellow oil. IR: 3027, 2974, 2927, 1650 (C¼O), 1593 (C¼C), 1239,
1
5
5
746, 693. H-NMR: 3.82 (dt, J ¼ 15.2, J(H,F) ¼ 4.4, 1 H, CH2(4)); 3.92 (dt, J ¼ 15.2, J(H,F) ¼ 4.8, 1 H,
CH2(4)); 6.51 (d, J ¼ 16.0, 1 H); 6.62 (d, J ¼ 16.0, 1 H); 6.56, (dd, J ¼ 3.6, 1.6, 1 H); 7.19 (t, J ¼ 52.8,
CF2H); 7.24 – 7.26 (m, 3 H); 7.30 (tt, J ¼ 8.0, 1.6, 2 H); 7.35 – 7.40 (m, 2 H); 7.42 (t, J ¼ 8.0, 2 H); 7.51 (dt,
J ¼ 7.2, 1.2, 2 H); 7.59 (dd, J ¼ 2.0, 0.8, 1 H). 19F-NMR: ꢀ 125.07 (dt, 2J(F,H) ¼ 53.0, 5J(F,H) ¼ 4.4, 1 F);
2
1
ꢀ 125.17 (dt, J(F,H) ¼ 53.0, 5J(F,H) ¼ 4.4, 1 F). 13C-NMR: 44.2 (C(4)); 93.0 (C(5)); 107.7 (t, J(C,F) ¼
3
237.7, CHF2); 112.9, 114.6 (t, J(C,F) ¼ 6.1, C(3)); 118.6; 125.4; 127.1; 128.2; 128.5; 128.8; 128.9; 130.3;
131.1; 136.0; 143.0; 146.4; 153.7; 159.0 (t, 2J(C,F) ¼ 22.1, C(2)); 176.4 (C¼O). LC/ESI-MS: 393 (100, [M þ
H]þ). Anal. calc. for C24H18F2O3 (392.40): C 73.46, H 4.62; found: C 73.54, H 4.43.

Helvetica Chimica Acta – Vol. 94 (2011)
2037
{2-(Difluoromethyl)-4,5-dihydro-5-phenyl-5-[(E)-2-phenylethenyl]furan-3-yl}(phenyl)methanone
(4b). Yield: 0.137 g (34%). Pale-yellow oil. IR: 3026, 2958, 1627 (C¼O), 1605 (C¼C), 1234, 748, 692.
5
1H-NMR: 3.60 (dt, J ¼ 15.2, 5J(H,F) ¼ 4.8, 1 H, CH2(4)); 3.67 (dt, J ¼ 15.2, J(H,F) ¼ 3.6, 1 H, CH2(4));
6.40 (t, J ¼ 52.4, CF2H); 6.45 (d, J ¼ 16.0, 1 H); 6.13 (d, J ¼ 16.0, 1 H); 7.25 (t, J ¼ 7.2, 1 H); 7.31 – 7.51 (m,
11 H); 7.56 (tt, J ¼ 6.8, 1.6, 1 H); 7.64 (dt, J ¼ 6.8, 1.6, 2 H). 19F-NMR: ꢀ 124.1 (dt, 2J(F,H) ¼ 47.0,
2
5
5J(F,H) ¼ 3.4, 1 F); ꢀ 124.1 (dt, J(F,H) ¼ 47.0, J(F,H) ¼ 3.4, 1 F). 13C-NMR: 45.0 (C(4)); 92.5 (C(5));
107.2 (t, 1J(C,F) ¼ 237.7, CHF2); 117.1 (t, 3J(C,F) ¼ 5.4, C(3)); 125.3; 125.5; 127.1; 128.3; 128.3; 128.5;
128.6; 128.8; 128.9; 128.97; 129.0; 129.6; 130.2; 131.0; 131.5; 132.9; 136.0; 139.5; 142.8; 156.1 (t, 2J(C,F) ¼
22.1, C(2)); 191.1 (C¼O). LC/ESI-MS: 403 (100, [M þ H]þ). Anal. calc. for C26H20F2O2 (402.43): C 77.60,
H 5.01; found: C 77.81, H 4.82.
1-(4,7-Dihydro-2,5,7-triphenyloxepin-3-yl)-2,2-difluoroethanone (5). Yield: 0.072 g (18%). Pale-
1
yellow oil. IR: 3058, 2916, 1690 (C¼O), 1686 (C¼C), 1073, 742, 693. H-NMR: 3.12 (d, J ¼ 16.8, 1 H,
CH2(4)); 4.46 (dt, J ¼ 16.8, 5J(H,F) ¼ 2.4, 1 H, CH2(4)); 4.48 (t, J ¼ 53.6, CF2H); 5.52 (s, HꢀC(7)); 6.12 (s,
HꢀC(6)); 7.20 – 7.36 (m, 7 H); 7.43 – 7.50 (m, 4 H); 7.56 (td, J ¼ 7.6, 0.8, 2 H); 7.82 (d, J ¼ 7.6, 2 H). 19F-
NMR: ꢀ 125.0 (d, 2J(F,H) ¼ 54.5, 1 F); ꢀ 125.1 (d, 2J(F,H) ¼ 54.5, 1 F). 13C-NMR: 40.5 (C(4)); 57.4
(C(7)); 73.4; 109.5 (t, 1J(C,F) ¼ 252.3, CHF2); 126.1; 127.5; 128.2; 128.4; 128.7; 129.1; 129.13; 129.5; 130.5;
4
2
2
133.6; 134.8; 135.4; 138.2; 138.8; 193.3 (d, J(C,F) ¼ 2.3, C(2)); 198.6 (dd, J(C,F) ¼ 29.7, J(C,F) ¼ 20.6,
C¼O). LC/ESI-MS: 403 (100, [M þ H]þ). Anal. calc. for C26H20F2O2 (402.43): C 77.60, H 5.01; found: C
77.46, H 5.23.
Authors are grateful to the TꢀBITAK (106T235) for financial support, and M. Y. thanks the
TꢀBITAK for post doctoral fellowship.
REFERENCES
[1] K. Uneyama, ꢃOrganofluorine Chemistryꢂ, Blackwell, Oxford, 2006; P. Kirsch, ꢃModern Fluoroor-
ganic Chemistryꢂ, Wiley-VCD, Weinheim, Germany, 2004; R. Filler, Y. Kobayashi, L. M.
Yagupolskii, ꢃOrganofluorine Compounds in Medical Chemistry and Biochemistry Applicationsꢂ,
Elsevier, Amsterdam, 1993; T. Hiyama, ꢃOrganofluorine Compounds Chemistry and Applicationꢂ,
Springer-Verlag, Berlin, 2000; R. D. Chambers, ꢃFluorine in Organic Chemistryꢂ, Blackwell: Oxford,
2004; C. Isanbor, D. Oꢂ Hagan, J. Fluorine Chem. 2006, 127, 303; F. M. D. Ismail, J. Fluorine Chem.
2002, 118, 27.
[2] M. J. Tozer, T. F. Herpin, Tetrahedron 1996, 52, 8619; J. M. Altenburger, D. Schirlin, Tetrahedron
Lett. 1991, 32, 7255; K. Brady, A. Wei, D. Ringe, R. H. Abeles, Biochemistry 1990, 29, 7600; T.
Tanaka, M. Kawase, S. Tani, Life Sci. 2003, 73, 2985; G. Spengler, A. Molnar, G. Klausz, Y. Mandi,
M. Kawase, N. Motohashi, J. Molnar, Int. J. Antimicrob. Agents 2004, 23, 631; R. R. Frey, C. K. Wada,
R. B. Garland, M. L. Curtin, M. R. Michaelides, J. Li, L. J. Pease, K. B. Glaser, P. A. Marcotte, J. J.
Bouska, S. S. Murphy, S. K. Davidsen, Bioorg. Med. Chem. Lett. 2002, 12, 3443.
[3] M. Kawase, H. Harada, S. Saito, J. Cui, S. Tani, Bioorg. Med. Chem. Lett. 1999, 9, 193; M. Kawase, N.
Motohashi, H. Sakagami, T. Kanamoto, H. Nakashima, L. Ferenczy, K. Wolfard, C. Miskolci, J.
´
´
Molnar, Int. J. Antimicrob. Agents 2001, 18, 161; A. Molnar, K. Wolfart, M. Kawase, N. Motohashi, J.
´
Molnar, In Vivo 2004, 18, 505.
[4] M. Kawase, H. Sakagami, K. Kusama, N. Motohashi, S. Saito, Bioorg. Med. Chem. Lett. 1999, 9, 3113.
[5] T. Kitazume, T. Yamazahi, ꢃExperimental Methods in Organic Fluorine Chemistryꢂ, Gordon and
´
Breach Science Publisher, Amsterdam, 1998; M. Hudlicky, A. E. Pavlath, ꢃChemistry of Organic
Fluorine Compounds IIꢂ, Am. Chem. Soc. Washington, DC, 1995; G. Shi, Y. Xu, M. Xu, Tetrahedron
1991, 47, 1629.
[6] a) A. Citterio, R. Santi, T. Fiorani, S. Strologo, J. Org. Chem. 1989, 54, 2703; b) A. Citterio, D.
Fancelli, C. Finzi, L. Pesce, R. Santi, J. Org. Chem. 1989, 54, 2713; c) J. M. Mellor, S. Mohammed,
Tetrahedron Lett. 1991, 32, 7111; d) J. M. Mellor, S. Mohammed, Tetrahedron 1993, 49, 7547; e) H.
Nishino, V.-H. Hguyen, S. Yoshinaga, K. Kurosawa, J. Org. Chem. 1996, 61, 8264; f) F. Garzino, A.
´
Meou, P. Brun, Tetrahedron Lett. 2000, 41, 9803; g) G. Bar, A. F. Parsons, C. B. Thomas, Tetrahedron
Lett. 2000, 41, 7751; h) S. Kajikawa, H. Nishino, K. Kurosawa, Heterocycles 2001, 54, 171; i) G. Bar,

2038
Helvetica Chimica Acta – Vol. 94 (2011)
A. F. Parsons, C. B. Thomas, Tetrahedron 2001, 57, 4719; j) G. G. Melikyan, Synthesis 1993, 833; k) J.
Iqbal, B. Bhatia, N. K. Nayyar, Chem. Rev. 1994, 94, 519; l) B. B. Snider, Chem. Rev. 1996, 96, 339;
m) G.-W. Wang, Y.-W. Dong, P. Wu, T.-T. Yuan, Y.-B. Shen, J. Org. Chem. 2008, 73, 7088; n) X.-Q.
Pan, J.-P. Zou, W. Zhang, Mol. Diversity 2009, 13, 421; o) R. ꢄalıs¸kan, T. Pekel, W. H. Watson, M.
Balci, Tetrahedron Lett. 2005, 46, 6227; p) A. S. Demir, M. Emrullahoglu, Curr. Org. Synth. 2007, 4,
321.
[7] E. Baciocchi, R. Ruzziconi, Synth. Commun. 1988, 18, 1841; V. Nair, J. Mathew, K. V.
Radhakrishnan, J. Chem. Soc., Perkin Trans. 1 1996, 1487; K. Kobayashi, K. Sakashita, H.
Akamatsu, K. Tanaka, M. Uchida, T. Uneda, T. Kitamura, O. Morikawa, H. Konishi, Heterocycles
1999, 51, 2881; Y. R. Lee, B. S. Kim, D. H. Kim, Tetrahedron 2000, 56, 8845; V. Nair, P. M. Treesa, D.
Maliakal, N. P. Rath, Tetrahedron 2001, 57, 7705; C.-C. Tseng, Y.-L. Wu, C.-P. Chuang, Tetrahedron
2002, 58, 7625; Y.-J. Liao, Y.-L. Wu, C.-P. Chuang, Tetrahedron 2003, 59, 3511; K. Kobayashi, K.
Nagase, O. Morikawa, H. Konishi, Heterocycles 2003, 60, 939; C.-P. Chuang, Y.-L. Wu, Tetrahedron
2004, 60, 1841; V. Nair, A. Deepthi, Chem. Rev. C 2007, 107, 1862; V. Nair, K. Mohanan, T. D. Suja, E.
Suresh, Tetrahedron Lett. 2006, 47, 2803; K. Bahrami, M. M. Khodaei, F. Naali, J. Org. Chem. 2008,
73, 6835.
[8] F. M. Dean, ꢃAdvances in Heterocyclic Chemistryꢂ, Academic, New York, 1982, 30, 167; F. M. Dean,
M. V. Sargent, ꢃComprehensive Heterocyclic Chemistryꢂ, Pergamon, New York, 1984, 4, Part. 3, 531;
H.-L. Elbe, F. Kunisch, D. Bielefeldt, R. Tiemann, K. Stenzel, S. Dutzmann, M. Kugler, H. Schrage,
˘
˘
˘
US Patent 6,107,336, August 22, 2000; E. Logoglu, M. Yılmaz, H. Katircioglu, M. Yakut, S. Mercan,
Med. Chem. Res. 2010, 19, 490; M. Miski, J. Jakupovic, Phytochemistry 1990, 29, 1995; C. Zdero, F.
Bohlman, R. M. King, H. Robinson, Phytochemistry 1986, 25, 509; C. E. Heltzel, A. A. L.
Gunatilaka, T. E. Glass, D. G. I. Kingston, G. Hoffmann, R. K. Johnson, J. Nat. Prod. 1993, 56, 1500.
[9] a) O. Alagoz, M. Yilmaz, A. T. Pekel, Synth. Commun. 2006, 36, 1005; b) M. Yilmaz, A. T. Pekel,
Synth. Commun. 2001, 31, 3871; c) M. Yilmaz, A. T. Pekel, Synth. Commun. 2001, 31, 2189; d) M.
Yilmaz, E. Bicer, A. T. Pekel, Turk. J. Chem. 2005, 29, 579; e) M. Yilmaz, A. T. Pekel, J. Fluorine
Chem. 2005, 126, 401; f) M. Yilmaz, N. Uzunalioglu, A. T. Pekel, Tetrahedron 2005, 61, 8860; g) E. V.
Burgaz, M. Yilmaz, A. T. Pekel, A. ꢅktemer, Tetrahedron 2007, 63, 7229; h) M. Yilmaz, N.
Uzunalioglu, M. Yakut, A. T. Pekel, Turk. J. Chem. 2008, 32, 411; i) M. Yilmaz, M. Yakut, A. T.
Pekel, Synth. Commun. 2008, 38, 914; j) E. V. B. Yilmaz, M. Yilmaz, A. Oktemer, Arkivoc 2011, (ii),
363.
[10] D. Sellanes, L. Scarone, E. Manta, P. Wipf, G. Sera, Lett. Org. Chem. 2006, 3, 309.
[11] H. Lebel, D. Guay, V. Paquet, K. Huard, Org. Lett. 2004, 6, 3047.
[12] J. B. Lambert, C. Liu, T. Kouliev, J. Phys. Org. Chem. 2002, 15, 667.
[13] H. M. C. Ferraz, M. K. Sano, M. R. S. Nunes, G. G. Bianco, J. Org. Chem. 2002, 67, 4122; R.
Antonioletti, S. Malancona, P. Bovicelli, Tetrahedron 2002, 58, 8825; A. Wu, D. Cremer, Int. J. Mol.
Sci. 2003, 4, 158.
[14] A. GꢁvenÅ, A. T. Pekel, ꢅ. M. KoÅkar, Chem. Eng. J. 2004, 99, 257.
Received March 10, 2011