Radical cyclization reactions via manganese(III) acetate leading to 2-thienyl-substituted dihydrofuran compounds

Article abstract of DOI:10.1002/hlca.201100397

The 2-thienyl-substituted 4,5-dihydrofuran derivatives 3-8 were obtained by the radical cyclization reaction of 1,3-dicarbonyl compounds 1a-1f with 2-thienyl-substituted conjugated alkenes 2a-2e by using [Mn(OAc)₃] (Tables 1-5). In this study, reactions of 1,3-dicarbonyl compounds 1a-1e with alkenes 2a-2c gave 4,5-dihydrofuran derivatives 3-5 in high yields (Tables 1-3). Also the cyclic alkenes 2d and 2e gave the dihydrobenzofuran compounds, i.e., 6 and 7 in good yields (Table 4). Interestingly, the reaction of benzoylacetone (=1-phenylbutane-1,3-dione; 1f) with some alkenes gave two products due to generation of two stable carbocation intermediates (Table 5). Copyright

Full text of DOI:10.1002/hlca.201100397

Helvetica Chimica Acta – Vol. 95 (2012)
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Radical Cyclization Reactions via Manganese(III) Acetate Leading to 2-
Thienyl-Substituted Dihydrofuran Compounds
by Emre BiÅer*a), Mehmet Yılmaz*b), Melih Karatas¸a), and Ahmet Tarık Pekela)
a) Department of Chemistry, Faculty of Science, Ankara University, TR-06100 Tandogan/Ankara
(phone: þ 90-312-2126720/1428; e-mail: emre.bicer@mam.gov.tr)
b) Department of Chemistry, Faculty of Arts and Sciences, Kocaeli University, TR-41380 Umuttepe,
Kocaeli (phone: þ 90-262-3032058; e-mail: mehmet.yilmaz@kocaeli.edu.tr)
The 2-thienyl-substituted 4,5-dihydrofuran derivatives 3 – 8 were obtained by the radical cyclization
reaction of 1,3-dicarbonyl compounds 1a – 1f with 2-thienyl-substituted conjugated alkenes 2a – 2e by
using [Mn(OAc)3] (Tables 1 – 5). In this study, reactions of 1,3-dicarbonyl compounds 1a – 1e with
alkenes 2a – 2c gave 4,5-dihydrofuran derivatives 3 – 5 in high yields (Tables 1 – 3). Also the cyclic alkenes
2d and 2e gave the dihydrobenzofuran compounds, i.e., 6 and 7 in good yields (Table 4). Interestingly, the
reaction of benzoylacetone (¼1-phenylbutane-1,3-dione; 1f) with some alkenes gave two products due
to generation of two stable carbocation intermediates (Table 5).
Introduction. – In the last three decades, oxidative cyclization reactions via
transition metal salts (Mn3þ, Co3þ Cu2þ, Ce4þ) have been very popular in synthetic
organic chemistry [1]. The distinctive properties of radical cyclization reactions have
always been attractive to organic chemists. Therefore, cyclization reactions of
enolizable 1,3-dicarbonyl compounds with unsaturated hydrocarbons leading to the
formations of functionalized products such as furans [2], dihydrofurans [3], lactones
[4], and lactams [5] in high yields have aroused much interest because of their potential
to open ways to natural products [6].
Recently, we have reported the formation of dihydrofuran and furan derivatives
resulting from radical cyclizations of 1,3-dicarbonyl compounds with alkenes [7] and
alkynes [8] by using [Mn(OAc)3]. The radical cyclization reactions of 3-oxopropane-
nitriles with conjugated alkenes, substituted with phenyl and 2-thienyl groups [9], and
with a,b-unsaturated amides [10] have been studied as well. And, in addition, 4,5-
dihydrofuran-3-carbonitrile compounds have shown antifungal and antibacterial
activity [11]. A study focused on the reactions of 3-oxopropanenitriles with 2-
thienyl-substituted alkenes has been published [12]. Also, the reaction of 4-
hydroxycoumarin (¼4-hydroxy-2H-1-benzopyran-2-one) and 2-hydroxy-1,4-naphtho-
quinones with electron-rich alkenes has been reported [13].
Reactions of 1,3-dicarbonyl compounds with 2-thienyl-substituted conjugated
alkenes have not been investigated so far. In this study, we describe the radical
cyclization reactions of conjugated 2-thienyl-substituted alkenes 2a – 2e with various
acyclic and cyclic 1,3-dicarbonyl compounds, mediated by [Mn(OAc)3]. As a result of
these reactions, 2-thienyl-substituted 4,5-dihydrofuran derivatives were obtained in
high yields.
ꢀ 2012 Verlag Helvetica Chimica Acta AG, Zꢁrich

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Helvetica Chimica Acta – Vol. 95 (2012)
Results and Discussion. – In this study, acetylacetone (¼ pentane-2,4-dione; 1a),
ethyl acetoacetate (¼ethyl 3-oxobutanoate; 1b), dimedone (¼ 5,5-dimethylcyclohex-
ane-1,3-dione; 1c), 5-phenylcyclohexane-1,3-dione (1d), cyclohexane-1,3-dione (1e),
and benzoylacetone (¼1-phenylbutane-1,3-dione; 1f) were used as 1,3-dicarbonyl
compounds, and 2-(1-phenylethenyl)thiophene (2a), 2-[1-(4-methylphenyl)ethenyl]-
thiophene (2b), 2-[1-(4-fluorophenyl)ethenyl]thiophene (2c), 2-(cyclohex-1-en-1-
yl)thiophene (2d), and 2-(cyclopent-1-en-1-yl)thiophene (2e) were used as 2-thienyl-
substituted alkenes (for formulas, see below, Tables 1 – 5). The thiophenes 2a – 2e were
synthesized by elimination of H2O from the corresponding alcohols, which, in turn,
were prepared by Grignard reaction of the respective carbonyl compounds [9].
The mechanism of the cyclization reactions of 1,3-dicarbonyl compounds with 2-
thienyl-substituted alkenes 2 is depicted in Scheme 1. First, [MnIII-(enolato)] complex
B is generated by the reaction of [Mn(OAc)3] and enolizable 1,3-dicarbonyl compound
A. MnIII is then reduced to MnII by the uptake of an electron within B, whereby radical
C is generated. After the addition of C to alkene 2, radical intermediate D is oxidized
by MnIII to yield the carbocation E. Dihydrofuran F is then formed by cyclization.
Scheme 1. Mechanism of the Radical Cyclization Reaction of 1,3-Dicarbonyl Compounds 1a – 1e with
Alkenes 2 Mediated by MnIII
The reaction of 1,3-dicarbonyl compounds 1a – 1e with the 2-(1-arylethenyl)thio-
phenes 2a – 2c gave 2-thienyl-substituted dihydrofuran derivatives 3 – 5 in high yields
1
(Tables 1 – 3). The characterization of these products was performed by H-NMR
2
spectroscopy. An AB system with J ¼ 14.4 – 14.8 Hz was found for CH2(4) of the 4,5-
dihydrofuran compounds 3a, 3b, 4a, 5a, and 5b; the AB system was further split into a q
5
by a J coupling of 1.2 – 1.6 Hz with MeꢀC(2). This long-range coupling constant was
confirmed by a COSYexperiment with 3b. Most of the 2-(2-thienyl)-substituted 3,5,6,7-
tetrahydrobenzofuran-4(2H)-ones 3c – 3e, 4c, 4d, and 5c – 5e, obtained with the cyclic
1
1,3-dicarbonyl compounds 1c – 1e, showed similar patterns in the H-NMR spectra.
For instance, the diastereotopic CH2(3) protons of 4c at d(H) 3.46 and 3.66 (2JAB
¼
5
14.8 Hz) showed also a J coupling of 2.0 Hz with CH2(7), and the signal of the
5
diastereotopic CH2(7) protons appeared at d(H) 2.41 as a t (5J ¼ 2 Hz). This J was
confirmed by a COSY experiment with 4b. The yields of 5a – 5e in Table 3 shows that a

Helvetica Chimica Acta – Vol. 95 (2012)
797
Table 1. Reaction of 2-(1-Phenylethenyl)thiophene (2a) with 1,3-Dicarbonyl Compounds
1,3-Dione
R
R’
Product
Yield [%]
1a
1b
1c
1d
1e
Me
Me
Me
EtO
3a
3b
3c
3d
3e
86
89
91
81
84
ꢀCH2C(Me2)CH2ꢀ
ꢀCH2CH(Ph)CH2ꢀ
ꢀ(CH2)3ꢀ
Table 2. Reaction of 2-[1-(4-Methylphenyl)ethenyl]thiophene (2b) with 1,3-Dicarbonyl Compounds
1,3-Dione
R
R’
Product
Yield [%]
1a
1b
1c
1d
Me
Me
Me
EtO
4a
4b
4c
4d
87
89
96
93
ꢀCH2C(Me2)CH2ꢀ
ꢀCH2CH(Ph)CH2ꢀ
Table 3. Reaction of 2-[1-(4-Fluorophenyl)ethenyl]thiophene (2c) with 1,3-Dicarbonyl Compounds
1,3-Dione
R
R’
Product
Yield [%]
1a
1b
1c
1d
1e
Me
Me
Me
EtO
5a
5b
5c
5d
5e
100
96
100
98
ꢀCH2C(Me2)CH2ꢀ
ꢀCH2CH(Ph)CH2ꢀ
ꢀ(CH2)3ꢀ
100

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Helvetica Chimica Acta – Vol. 95 (2012)
Table 4. Reaction of 2-(Cyclohex-1-en-1-yl)- and 2-(Cyclopent-1-en-1-yl)thiophene (2d and 2e, resp.)
with 1,3-Dicarbonyl Compounds
1,3-Dione
R
R’
Alkene
n
Product
Yield [%]
1a
1c
1e
1a
1b
1e
Me
Me
ꢀCH2C(Me2)CH2ꢀ
ꢀ(CH2)3ꢀ
Me
2d
2d
2d
2e
2e
2e
2
2
2
1
1
1
6a
6b
6c
7a
7b
7c
61
70
73
80
86
89
Me
Me
EtO
ꢀ(CH2)3ꢀ
p-fluoro substituent influences positively the MnIII-promoted cyclization reactions, i.e.,
the carbocation character of intermediate E (Scheme 1) is stabilized by the 4-fluoro
substituent at the Ar ring (R4), resulting in almost quantitative yields for the reaction of
alkene 2c with the 1,3-dicarbonyl compounds 1a – 1e.
Good yields were also realized with the cyclic alkenes 2d and 2e yielding 6a – 6c and
7a – 7c, respectively (Table 4). But the reactions with five-membered cycloalkene 2e
were more efficient than with the six-membered cycloalkene 2d, which can be
explained by the higher ring strain of 2e.
Interestingly, treatment of benzoylacetone (1f) with [Mn(OAc)3] in the presence of
an alkene 2 provided two products 8 (Table 5). A proposed mechanism for this reaction
is displayed in Scheme 2. Thus, after addition of the radical form of the enolate to
alkene 2, an adduct radical intermediate is generated and then oxidized with 1 equiv. of
Table 5. Reaction of 1-Phenylbutane-1,3-dione (1f) with Alkenes 2
Alkene
R
R’
Product
Yield [%]
Product
Yield [%]
2a
2b
2c
2d
Ph
H
H
H
8a
8c
8e
8g
30
33
38
34
8b
8d
8f
54
56
56
40
4-MeꢀC6H4
4-FꢀC6H4
ꢀ(CH2)4ꢀ
8h

Helvetica Chimica Acta – Vol. 95 (2012)
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Scheme 2. Mechanism of the Radical Cyclization Reaction of Benzoylacetone (1f) with Alkenes 2
MnIII to the corresponding carbocation (cf. Scheme 1). Due to the fact that
benzoylacetone has two enolic forms, two carbocations G and H are generated. After
the ring closure, two dihydrofuran products are obtained, i.e., a 2-phenyl-substituted
dihydrofuran by pathway i, and a 2-methyl-substituted dihydrofuran by pathway ii.
The structures of the two products 8 obtained from each alkene 2 with 1f were
1
determined by the H-NMR spectra. For instance, the difference of the coupling
pattern of the diastereotopic CH2(4) protons of 8a and 8b established their structures:
2
5
8a exhibited 2 dq with JAB ¼ 14.8 Hz and J ¼ 1.6 Hz, and 8b just an AB system with
2JAB ¼ 14.8 Hz.
In conclusion, [Mn(OAc)]3-mediated, radical cyclization reactions of acyclic and
cyclic 1,3-dicarbonyl compounds 1 with 2-thienyl-subtituted alkenes 2 gave corre-
sponding dihydrofuran compounds in good to excellent yields. Moreover, unexpected
products were obtained in the reaction of alkenes 2 with benzoylacetone 1f, i.e., two
different structures were formed due to two enolic forms of 1f.
Experimental Part
General. All 1,3-dicarbonyl compounds and other reagents were purchased from Merck. Column
chromatography (CC): silica gel (SiO2 60, 40 – 60 mm; Merck). Prep. TLC: silica gel (SiO2 PF254–366 nm;
Merck), 2 mm thickness on 20 ꢁ 20 cm plates. TLC: aluminium-packed silica gel plates (Merck). M.p.:
Gallenkamp capillary melting point apparatus. IR Spectra (KBr disc): Matson-1000 FT-IR spectrometer;
400 – 4000 cmꢀ1 range with 4 cmꢀ1 resolution; in cmꢀ1. 1H- (400 MHz) and 13C-NMR (100 MHz) Spectra:
Bruker-DPX-400 high-performance digital FT-NMR spectrometer; in CDCl3; d in ppm rel. to Me4Si as
internal standard, J in Hz; Tph ¼ 2-thienyl. MS: Waters-2695-Alliance HPLC/Waters-Micromass-2Q (ESI
method) and Micromass-UK-Platform II (EI-MS method) spectrometers; in m/z (rel. %). Elemental
analyses: Leco-932-CHNS-O instrument.
Dihydrofurans by Oxidative Cyclization Reactions. Oxidative cyclization reactions were carried out
with 1/2/[Mn(OAc)3] in a molar ratio 2 :1:3. [Mn(OAc)3] · 2 H2O (98%) was prepared electrochemically
according to [14].

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Helvetica Chimica Acta – Vol. 95 (2012)
Thus, [Mn(OAc)3] · 2 H2O (0.83 g, 3 mmol) in AcOH (20 ml) was heated under N2 at 808 until it
dissolved. Then, the soln. was cooled to 508, and a soln. of 1 (2 mmol) and 2 (1 mmol) in AcOH (3 ml)
was added. The reaction was completed when the dark brown color of the soln. had changed to red. H2O
(20 ml) was added, and the mixture extracted with CHCl3 (3 ꢁ 20 ml). The combined org. phase was
neutralized by washing with sat. NaHCO3 soln., dried (Na2SO4), and concentrated and the crude product
purified by CC or prep. TLC (SiO2, hexane/AcOEt).
1-[4,5-Dihydro-2-methyl-5-phenyl-5-(2-thienyl)furan-3-yl]ethanone (3a): Yield 244.2 mg (86%).
Yellow oil. IR: 3065, 3028 (arom. CꢀH), 2920, 2864 (aliph. CꢀH), 1674 (C¼O), 1623 (C¼C).
1H-NMR: 7.48 – 7.28 (m, Ph, HꢀC(5) of Tph); 6.96 (dd, J ¼ 5.0, 3.6, HꢀC(4) of Tph); 6.92 (dd, J ¼ 3.6, 1.2,
HꢀC(3) of Tph); 3.82 (dq, J ¼ 14.5, 1.5, HaꢀC(4)); 3.62 (dq, J ¼ 14.5, 1.5, HbꢀC(4)); 2.39 (t, J ¼ 1.5,
MeꢀC(2)); 2.27 (s, MeCOꢀC(3)). 13C-NMR: 194.0 (C¼O); 165.5 (C(2)); 149.2; 144.6; 128.4; 127.9; 126.6;
125.8; 125.8; 125.4; 112.1 (C(3)); 89.3 (C(5)); 46.4; 29.4; 15.1. MS: 285 (1.5, [M þ H]þ), 284 (6, Mþ), 266
(2, [M ꢀ H2O]þ), 241 (14, [M ꢀ C2H3O]þ), 201 (1, [M ꢀ C4H3O]þ), 184 (1, [C5H8O2]þ), 91 (1,
[C6H5CH2]þ), 83 (0.5, [C4H3S]þ). Anal. calc. for C17H16O2S: C 71.8, H 5.7, S 11.3; found: C 71.9, H
5.6, S 11.4.
Ethyl 4,5-Dihydro-2-methyl-5-phenyl-5-(2-thienyl)furan-3-carboxylate (3b): Yield 279.5 mg (89%).
Yellow oil. IR: 3063, 3029 (arom. CꢀH), 2979, 2928 (aliph. CꢀH), 1698 (C¼O), 1654 (C¼C). 1H-NMR:
7.41 – 7.20 (m, Ph, HꢀC(5) of Tph); 6.89 (dd, J ¼ 5.0, 3.6, HꢀC(4) of Tph); 6.86 (dd, J ¼ 3.6, 1.2, HꢀC(3) of
Tph); 4.12 (q, J ¼ 7.1, MeCH2O); 3.69 (dq, J ¼ 14.7, 1.5, HaꢀC(4)); 3.48 (dq, J ¼ 14.7, 1.5, HbꢀC(4)); 2.29
(t, J ¼ 1.5, MeꢀC(2)); 1.23 (t, J ¼ 7.1, MeCH2O). 13C-NMR: 166.2 (C¼O); 165.9 (C(2)); 149.8; 145.1;
128.5; 128.0; 126.8; 125.9; 125.5; 102.0 (C(3)); 89.5 (C(5)); 59.9; 46.0; 14.7; 14.5. MS: 314 (4, Mþ), 313
(14, [M ꢀ H]þ), 187 (5, [M ꢀ C4H3S ꢀ C2H3O ꢀ H]þ). Anal. calc. for C18H18O3S: C 68.8, H 5.8, S 10.2;
found: C 68.9, H 5.7, S 10.1.
3,5,6,7-Tetrahydro-6,6-dimethyl-2-phenyl-2-(2-thienyl)benzofuran-4(2H)-one (3c): Yield 294.8 mg
(91%). Yellow oil. IR: 3096, 3063 (arom. CꢀH), 2955, 2930 (aliph. CꢀH), 1641 (C¼O). 1H-NMR: 7.40 –
7.21 (m, Ph, HꢀC(5) of Tph); 6.87 (dd, J ¼ 5.0, 3.6, HꢀC(4) of Tph); 6.81 (dd, J ¼ 3.6, 1.2, HꢀC(3) of
Tph); 3.64 (dt, J ¼ 14.7, 1.8, HaꢀC(3)); 3.41 (dt, J ¼ 14.7, 1.8, HbꢀC(3)); 2.37 (s, 2 H); 2.20 (s, 2 H); 1.08 (s,
MeꢀC(6)); 1.06 (s, MeꢀC(6)). MS: 325 (100, [M þ H]þ), 306 (1, [M ꢀ H2O]þ), 241 (27, [M ꢀ C4H3S]þ),
211 (1, [M ꢀ C4H4S ꢀ C2H5]þ). Anal. calc. for C20H20O2S: C 74.0, H 6.2, S 9.9; found: C 73.8, H 6.3, S 9.8.
3,5,6,7-Tetrahydro-2,6-diphenyl-2-(2-thienyl)benzofuran-4(2H)-one (3d): Yield 301.3 mg (81%).
Light yellow oil. IR: 3061, 3029 (arom. CꢀH), 2948, 2902 (aliph. CꢀH), 1770 (C¼C), 1641 (C¼O).
1H-NMR: 7.48 – 7.27 (m, 2 Ph, HꢀC(5) of Tph); 6.99 – 6.93 (m, 2 H of Tph); 3.76 (d, J ¼ 13.7, HaꢀC(3));
3.57 – 3.51 (m, 2 H); 2.91 – 2.84 (m, 2 H); 2.75 – 2.67 (m, 2 H). 13C-NMR: 198.8 (C¼O); 167.6 (C(7a));
146.7; 144.3; 128.7; 128.4; 127.5; 127.4; 127.0; 126.9; 126.6; 126.5; 126.2; 126.0; 125.6; 113.0 (C(3a)); 93.8
(C(2)); 40.1; 31.8. MS: 372 (10, Mþ), 354 (14, [M ꢀ H2O]þ), 267 (2, [M ꢀ C8H9]þ), 226 (7, [M ꢀ
C10H10O]þ), 186 (7, [M ꢀ C12H12S]þ), 104 (18, [C8H8]þ), 84 (22, [C4H4S]þ), 69 (13, [C4H3O]þ), 43
(100, [C3H7]þ). Anal. calc. for C24H20O2S: C 77.4, H 5.4, S 8.6; found: C 77.5, H 5.4, S 8.5.
3,5,6,7-Tetrahydro-2-phenyl-2-(2-thienyl)benzofuran-4(2H)-one (3e): Yield 248.6 mg (84%). Light
yellow oil. IR: 3067 (arom. CꢀH), 2946, 2869 (aliph. CꢀH), 1673 (C¼C), 1605 (C¼O). 1H-NMR: 7.46 –
7.29 (m, Ph, HꢀC(5) of Tph); 6.96 (dd, J ¼ 5.0, 3.6, HꢀC(4) of Tph); 6.92 (dd, J ¼ 3.6, 1.2, HꢀC(3) of
Tph); 3.73 (dt, J ¼ 14.8, 1.7, HaꢀC(3)); 3.50 (dt, J ¼ 14.8, 1.7, HbꢀC(3)); 2.61 – 2.55 (m, 2 H); 2.45 – 2.39
(m, 2 H); 2.15 – 2.07 (m, 2 H). 13C-NMR: 196.0 (C¼O); 175.5 (C(7a)); 148.9; 144.4; 128.6; 128.3; 126.9;
126.4; 125.9; 125.5; 117.8; 112.9 (C(3a)); 93.2 (C(2)); 42.3; 36.7; 24.2; 21.9. MS: 297 (8, [M þ H]þ), 296
(28, Mþ), 278 (75, [M ꢀ H2O]þ), 268 (19, [M ꢀ C2H4]þ), 212 (17, [M ꢀ C4H4S]þ), 184 (16, [C12H8S]þ), 171
(40, [C7H9O2]þ), 84 (5, [C4H4S]þ), 77 (28, [C6H5]þ). Anal. calc. for C18H16O2S: C 72.9, H 5.4, S 10.8;
found: C 72.8, H 5.3, S 10.9.
4,5-Dihydro-1-[2-methyl-5-(4-methylphenyl)-5-(2-thienyl)furan-3-yl]ethanone (4a): Yield 259.3 mg
(87%). Brownish yellow oil. IR: 3090, 3015 (arom. CꢀH), 2924, 2866 (aliph. CꢀH), 1673 (C¼O), 1621
1
(C¼C). H-NMR: 7.32 (d, J ¼ 8.4, 2 arom. H); 7.25 (dd, J ¼ 5.2, 1.2, HꢀC(5) of Tph); 7.17 (d, J ¼ 8.4, 2
arom. H); 6.92 (dd, J ¼ 5.2, 3.6, HꢀC(4) of Tph); 6.88 (dd, J ¼ 3.6, 1.2, HꢀC(3) of Tph); 3.76 (dq, J ¼ 14.4,
1.6, HaꢀC(4)); 3.57 (dq, J ¼ 14.4, 1.6, HbꢀC(4)); 2.35 (s, 6 H); 2,22 (d, J ¼ 1.6, MeꢀC(2)). LC/ESI-MS: 299
(100, [M þ H]þ). Anal. calc. for C18H18O2S: C 72.5, H 6.1, S 10.7; found: C 72.4, H 6.2, S 10.8.

Helvetica Chimica Acta – Vol. 95 (2012)
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Ethyl 4,5-Dihydro-2-methyl-5-(4-methylphenyl)-5-(2-thienyl)furan-3-carboxylate (4b): Yield
291.9 mg (89%). Yellow oil. IR: 2972, 2924 (aliph. CꢀH), 1697 (C¼O), 1652 (C¼C). 1H-NMR: 7.33
(d, J ¼ 8.4, 2 arom. H); 7.25 (dd, J ¼ 5.6, 1.6, HꢀC(5) of Tph); 7.17 (d, J ¼ 8.4, 2 arom. H); 6.92 (dd, J ¼ 5.6,
3.2, HꢀC(4) of Tph); 6.90 (dd, J ¼ 3.2, 1.6, HꢀC(3) of Tph); 4.16 (q, J ¼ 7.2, MeCH2O); 3.70 (dq, J ¼ 14.4,
1.2, HaꢀC(4)); 3.51 (dq, J ¼ 14.4, 1.2, HbꢀC(4)); 2.35 (s, MeC6H4); 2.33 (t, J ¼ 1.2, MeꢀC(2)); 1.27 (t, J ¼
7.2, MeCH2O). LC/ESI-MS: 329 (100, [M þ H]þ). Anal. calc. for C19H20O3S: C 69.5, H 6.1, S 9.8; found: C
69.6, H 6.0, S 9.7.
3,5,6,7-Tetrahydro-6,6-dimethyl-2-(4-methylphenyl)-2-(2-thienyl)benzofuran-4(2H)-one (4c): Yield
1
324.5 mg (96%). Yellow oil. IR: 3029 (arom. CꢀH), 2949, 2874 (aliph. CꢀH), 1641 (C¼O). H-NMR:
7.28 – 7.30 (m, 2 arom. H); 7.26 (dd, J ¼ 4.8, 1.6, HꢀC(5) of Tph); 7.16 – 7.18 (m, 2 arom. H); 6.92 (dd, J ¼
4.8, 3.6, HꢀC(4) of Tph); 6.86 (dd, J ¼ 3.6, 1.6, HꢀC(3) of Tph); 3.66 (dt, J ¼ 14.8, 2.0, HaꢀC(3)); 3.46 (dt,
J ¼ 14.8, 2.0, HbꢀC(3)); 2.41 (t, J ¼ 2.0, 2 H); 2.35 (s, MeC6H4); 2.25 (s, 2 H); 1.13 (s, MeꢀC(6)); 1.11 (s,
MeꢀC(6)). 13C-NMR: 194.8 (C¼O); 174.4 (C(7a)); 149.2; 141.4; 138.1; 129.3; 126.8; 126.2; 125.8; 125.5;
111.5 (C(3a)); 93.5 (C(2)); 51.2; 42.2; 38.1; 34.5; 29.0; 28.9; 21.3. LC/ESI-MS: 339 (100, [M þ H]þ). Anal.
calc. for C21H22O2S: C 74.5, H 6.6, S 9.5; found: C 74.4, H 6.5, S 9.6.
3,5,6,7-Tetrahydro-2-(4-methylphenyl)-6-phenyl-2-(2-thienyl)benzofuran-4(2H)-one (4d): Yield
1
358.9 mg (93%). Yellow oil. IR: 3026 (arom. CꢀH), 2936, 2870 (aliph. CꢀH), 1629 (C¼O). H-NMR:
7.25 – 7.36 (m, 8 arom. H); 7.18 – 7.20 (m, 2 arom. H); 6.89 – 6.96 (m, 2 H of Tph); 3.67 – 3.74 (m,
HaꢀC(3)); 3.46 – 3.53 (m, 2 H); 2.77 – 2.83 (m, 2 H); 2.61 – 2.66 (m, 2 H); 2.36 (MeC6H4). LC/ESI-MS:
387 (100, [M þ H]þ). Anal. calc. for C25H22O2S: C 77.7, H 5.7, S 8.3; found: C 77.8, H 5.6, S 8.3.
1-[5-(4-Fluorophenyl)-4,5-dihydro-2-methyl-5-(2-thienyl)furan-3-yl]ethanone (5a): Yield 302 mg
(100%). Yellow oil. IR: 3071 (arom. CꢀH), 1675 (C¼O), 1614 (C¼C). 1H-NMR: 7.37 – 7.40 (m, 2
arom. H); 7.24 – 7.26 (m, HꢀC(5) of Tph); 7.00 – 7.04 (m, 2 arom. H); 6.91 (dd, J ¼ 5.2, 4.0, HꢀC(4) of
Tph); 6.86 (dd, J ¼ 4.0, 1.2, HꢀC(3) of Tph); 3.78 (dq, J ¼ 14.4, 1.2, HaꢀC(4)); 3.52 (dq, J ¼ 14.4, 1.2,
HbꢀC(4)); 2.33 (d, J ¼ 1.2, MeꢀC(2)); 2.22 (s, MeCOꢀC(3)). 13C-NMR: 194.2 (C¼O); 165.6 (C(2));
163.7; 149.2; 140.7; 140.6; 127.4; 127.3; 126.9; 126.2; 125.6; 115.6; 115.3; 112.4 (C(3)); 89.1 (C(5)); 46.6;
29.6; 15.3. LC/ESI-MS: 303 (100, [M þ H]þ). Anal. calc. for C17H15FO2S: C 67.5, H 5.0, F 6.3, S 10.6;
found: C 67.6, H 5.1, F 6.2, S 10.5.
Ethyl 5-(4-Fluorophenyl)-4,5-dihydro-2-methyl-5-(2-thienyl)furan-3-carboxylate (5b): Yield
318.7 mg (96%). Yellow oil. IR: 3098 (arom. CꢀH), 2974, 2916, 2857 (aliph. CꢀH), 1693 (C¼O), 1644
(C¼C). 1H-NMR: 7.39 – 7.42 (m, 2 arom. H); 7.25 (dd, J ¼ 4.8, 1.6, HꢀC(5) of Tph); 7.03 – 7.00 (m, 2 arom.
H); 6.92 (dd, J ¼ 4.8, 3.6, HꢀC(4) of Tph); 6.89 (dd, J ¼ 3.6, 1.6, HꢀC(3) of Tph); 4.18 (q, J ¼ 7.2,
MeCH2O); 3.74 (dq, J ¼ 14.4, 1.6, HaꢀC(4)); 3.48 (dq, J ¼ 14.8, 1.6, HbꢀC(4)); 2.33 (d, J ¼ 1.6, MeꢀC(2));
1.28 (t, J ¼ 7.2, MeCH2O). 13C-NMR: 166.1 (C¼O); 165.7 (C(2)); 163.7; 161.2; 149.5; 127.5; 126.9; 126.1;
125.5; 115.5; 102.0 (C(3)); 89.1 (C(5)); 59.9; 46.0; 29.9; 14.4. LC/ESI-MS: 333 (100, [M þ H]þ). Anal.
calc. for C18H17FO3S: C 65.0, H 5.2, F 5.7, S 9.6; found: C 65.1, H 5.1, F 5.7, S 9.5.
2-(4-Fluorophenyl)-3,5,6,7-tetrahydro-6,6-dimethyl-2-(2-thienyl)benzofuran-4(2H)-one (5c): Yield
1
342 mg (100%). Yellow oil. IR: 3111, 3071 (arom. CꢀH), 2943 (aliph. CꢀH), 1641 (C¼O). H-NMR:
7.37 – 7.41 (m, 2 arom. H); 7.30 (dd, J ¼ 5.2, 1.2, HꢀC(5) of Tph); 7.03 – 7.08 (m, 2 arom. H); 6.94 (dd, J ¼
5.2, 3.6, HꢀC(4) of Tph); 6.86 (dd, J ¼ 3.6, 1.2, HꢀC(3) of Tph); 3.69 (dt, J ¼ 14.4, 2.0, HaꢀC(3)); 3.43 (dt,
J ¼ 14.4, 2.0, HbꢀC(3)); 2.42 (t, J ¼ 2.0, 2 H); 2.27 (d, J ¼ 2.0, 2 H); 1.14 (s, MeꢀC(6)); 1.12 (s, MeꢀC(6)).
LC/ESI-MS: 343 (100, [M þ H]þ). Anal. calc. for C20H19FO2S: C 70.2, H 5.6, F 5.5, S 9.4; found: C 70.3, H
5.5, F 5.5, S 9.5.
2-(4-Fluorophenyl)-3,5,6,7-tetrahydro-6-phenyl-2-(2-thienyl)benzofuran-4(2H)-one (5d): Yield
383.2 mg (98%). Light yellow oil. IR: 3065, 3028 (arom. CꢀH), 2943 (aliph. CꢀH), 1639 (C¼O).
1H-NMR: 7.35 – 7.42 (m, 2 arom. H); 7.30 – 7.33 (m, 3 arom. H); 7.28 – 7.20 (m, 3 arom. H); 7.00 – 7.06 (m, 2
arom. H); 6.89 – 6.93 (m, 2 H of Tph); 3.71 (dt, J ¼ 14.2, 1.4, HaꢀC(3)); 3.44 – 3.49 (m, 2 H); 2.76 (m,
2 H); 2.62 (m, 2 H). 13C-NMR: 193.9 (C¼O); 174.4 (C(7a)); 163.8; 161.4; 148.5; 142.7; 140.2; 129.1; 127.6;
127.4; 127.0; 126.8; 126.0; 115.6; 112.8 (C(3a)); 93.2 (C(2)); 44.2; 42.4; 40.6; 31.7; 21.2; 14.5. LC/ESI-MS:
391 (100, [M þ H]þ). Anal. calc. for C24H20FO2S: C 73.6, H 5.1, F 4.9, S 8.2; found: C 73.5, H 5.2, F 4.8, S
8.1.
2-(4-Fluorophenyl)-3,5,6,7-tetrahydro-2-(2-thienyl)benzofuran-4(2H)-one (5e): Yield 314 mg
(100%). Yellow oil. IR: 3105, 3080 (arom. CꢀH), 2951, 2866 (aliph. CꢀH), 1637 C¼O. 1H-NMR:

802
Helvetica Chimica Acta – Vol. 95 (2012)
7.35 – 7.40 (m, 2 arom. H); 7.23 (dd, J ¼ 4.8, 1.2, HꢀC(5) of Tph); 7.00 (dd, J ¼ 8.4, 2.0, 2 arom. H); 6.88
(dd, J ¼ 4.8, 3.4, HꢀC(4) of Tph); 6.85 (dd, J ¼ 3.4, 1.2, HꢀC(3) of Tph); 3.65 (dt, J ¼ 14.8, 2.0, HaꢀC(3));
3.38 (dt, J ¼ 14.8, 2.0, HbꢀC(3)); 2.49 – 2.52 (m, 2 H), 2.30 – 2.35 (m, 2 H), 2.03 – 2.10 (m, 2 H). 13C-NMR:
195.4 (C¼O); 175.2 (C(7a)); 163.7; 161.3; 148.6; 140.3; 127.5; 127.4; 127.0; 126.6; 125.9; 115.6; 115.4; 112.8
(C(3a)); 92.7 (C(2)); 42.4; 36.7; 24.2; 21.9. LC/ESI-MS: 315 (100, [M þ H]þ). Anal. calc. for C18H15FO2S:
C 68.8, H 4.8, F 6.0, S 10.2; found: C 68.9, H 4.9, F 6.1, S 10.1.
1-[3a,4,5,6,7,7a-Hexahydro-2-methyl-7a-(2-thienyl)benzofuran-3-yl]ethanone (6a): Yield 159.8 mg
(61%). Light yellow oil. IR: 2936, 2862 (aliph. CꢀH), 1616 (C¼O). 1H-NMR: 7.13 (dd, J ¼ 4.8, 1.2,
HꢀC(5) of Tph); 6.95 (dd, J ¼ 4.6, 3.6, HꢀC(4) of Tph); 6.89 (dd, J ¼ 3.6, 1.2, HꢀC(3) of Tph); 3.33 (t, J ¼
6.4, HꢀC(3a)); 2.22 (s, MeCOꢀC(3)); 2.19 (s, MeꢀC(2)); 2.00 – 2.07 (m, 2 H); 1.88 – 1.96 (m, 2 H); 1.51 –
1.60 (m, 2 H); 1.36 – 1.46 (m, 2 H). LC/ESI-MS: 263 (100, [M þ H]þ). Anal. calc. for C15H18O2S: C 68.7, H
6.9, S 12.2; found: C 68.6, H 6.8, S 12.3.
3,4,5a,6,7,8,9,9a-Octahydro-3,3-dimethyl-5a-(2-thienyl)dibenzofuran-1(2H)-one (6b): Yield 211.4 mg
(70%). Yellow oil. IR: 2934 (aliph. CꢀH), 1637 (C¼O). 1H-NMR: 7.24 (dd, J ¼ 5.2, 1.2, HꢀC(5) of Tph);
7.04 (dd, J ¼ 3.6, 1.2, HꢀC(3) of Tph); 6.97 (dd, J ¼ 5.0, 3.2, HꢀC(4) of Tph); 3.52 (t, J ¼ 6.0, HꢀC(9a));
2.32 (d, J ¼ 1.6, 2 H); 2.23 (s, 2 H); 2.11 – 2.20 (m, 2 H); 1.88 – 1.93 (m, 2 H); 1.55 – 1.58 (m, 2 H); 1.45 –
1.49 (m, 2 H); 1.13 (s, MeꢀC(3)); 1.10 (s, MeꢀC(3)). 13C-NMR: 195.2 (C¼O); 175.3 (C(4a)); 149.5; 127.0;
124.9; 123.5; 115.4 (C(9b)); 92.4 (C(5a)); 51.5; 45.7; 38.3; 34.4; 34.0; 29.2; 28.6; 24.1; 18.7; 18.6. LC/ESI-
MS: 303 (100, [M þ H]þ). Anal. calc. for C18H22O2S: C 71.2, H 7.3, S 10.6; found: C 71.3, H 7.2, S 10.7.
3,4,5a,6,7,8,9,9a-Octahydro-5a-(2-thienyl)dibenzofuran-1(2H)-one (6c): Yield 200.0 mg (73%). Yel-
low oil. IR: 3098, 3074 (arom. CꢀH), 2940, 2864 (aliph. CꢀH), 1635 (C¼O). 1H-NMR: 7.40 (dd, J ¼ 5.2,
1.2, HꢀC(5) of Tph); 7.04 (dd, J ¼ 3.8, 1.2, HꢀC(3) of Tph); 6.97 (dd, J ¼ 5.0, 3.8, HꢀC(4) of Tph); 3.51 (tt,
J ¼ 6.0, 1.2, HꢀC(9a)); 2.45 – 2.52 (m, 2 H); 2.31 – 2.37 (m, 2 H); 2.11 – 2.15 (m, 2 H); 2.02 – 2.07 (m, 2 H);
1.85 – 1.98 (m, 2 H); 1.50 – 1.65 (m, 2 H); 1.40 – 1.48 (m, 2 H). LC/ESI-MS: 274 (100, [M þ H]þ). Anal.
calc. for: C16H18O2S: C 70.0, H 6.6, S 11.7; found: C 70.1, H 6.5, S 11.8.
1-[3a,5,6,6a-Tetrahydro-2-methyl-6a-(2-thienyl)-4H-cyclopenta[b]furan-3-yl]ethanone (7a): Yield
198.4 mg (80%). Light yellow oil. IR: 2953 (aliph. CꢀH), 1666 (C¼O), 1598 (C¼C). 1H-NMR: 7.23
(dd, J ¼ 4.8, 1.6, HꢀC(5) of Tph); 6.95 – 6.99 (m, 2 H of Tph); 3.67 (d, J ¼ 8.8, HꢀC(3a)); 2.40 (dd, J ¼
13.4, 8.6, HꢀC(4)); 2.79 (d, J ¼ 1.6, MeꢀC(2)); 2.22 (s, MeCOꢀC(3)); 2.01 – 2.17 (m, 2 H); 1.80 – 1.85 (m,
2 H); 1.67 – 1.71 (m, 1 H). LC/ESI-MS: 249 (100, [M þ H]þ). Anal. calc. for C14H16O2S: C 67.7, H 6.5, S
12.9; found: C 67.6, H 6.4, S 13.0.
Ethyl 3a,5,6,6a-Tetrahydro-2-methyl-6a-(2-thienyl)-4H-cyclopenta[b]furan-3-carboxylate (7b): Yield
239.1 mg (86%). Yellow oil. IR: 2961, 2870 (aliph. CꢀH), 1695 (C¼O), 1644 (C¼C). 1H-NMR: 7.21 (dd,
J ¼ 5.0, 1.6, HꢀC(5) of Tph); 6.98 (dd, J ¼ 5.0, 3.6, HꢀC(4) of Tph); 6.94 (dd, J ¼ 3.4, 1.6, HꢀC(3) of
Tph); 4.10 – 4.21 (m, MeCH2O); 3.63 (d, J ¼ 8.0, HꢀC(3a)); 2,40 (dd, J ¼ 13.6, 7.8, HꢀC(4)); 2.25 (d, J ¼
1.4, MeꢀC(2)); 2.05 – 2.15 (m, 1 H); 1.85 – 2.00 (m, 2 H); 1.75 – 1.81 (m, 1 H); 1.63 – 1.73 (m, 1 H); 1.30 (t,
J ¼ 6.8, MeCH2O). 13C-NMR: 167.5 (C¼O); 166.2 (C(2)); 148.4; 122.8; 124.7; 127.1; 105.5 (C(3)); 97.0
(C(6a)); 59.6; 55.5; 43.0; 34.2; 24.6; 14.7; 14.4. LC/ESI-MS: 279 (100, [M þ H]þ). Anal. calc. for
C15H18O3S: C 64.7, H 6.5, S 11.5; found: C 64.6, H 6.6, S 11.6.
1,2,3,3a,5,6,7,8b-Octahydro-3a-(2-thienyl)-8H-cyclopenta[b]benzofuran-8-one (7c): Yield 243.9 mg
(89%). Yellow oil. IR: 3101 (arom. CꢀH), 2938, 2868 (aliph. CꢀH), 1631 (C¼O). 1H-NMR: 7.26 (dd, J ¼
4.0, 1.2, HꢀC(5) of Tph); 6.96 – 7.01 (m, 2 H of Tph); 3.71 (t, J ¼ 3.2, HꢀC(8b)); 2.44 – 2.49 (m, 2 H);
2.34 – 2.40 (m, 2 H); 2.00 – 2.14 (m, 2 H); 1.92 – 1.96 (m, 2 H); 1.81 – 1.86 (m, 2 H); 1.61 – 1.69 (m, 2 H).
LC/ESI-MS: 261 (100, [M þ H]þ). Anal. calc. for C16H18O2S: C 70.0, H 6.6, S 11.7; found: C 69.9, H 6.5, S
11.8.
[4,5-Dihydro-2-methyl-5-phenyl-5-(2-thienyl)furan-3-yl]phenylmethanone (8a): Yield 103.8 mg
(30%). Yellow oil. IR: 3065 (arom. CꢀH), 2926 (aliph. CꢀH), 1610 (C¼O). 1H-NMR: 7.55 (m, 2
arom. H); 7.24 – 7.47 (m, Ph, HꢀC(5) of Tph); 6.91 (dd, J ¼ 5.2, 3.6, HꢀC(4) of Tph); 6.88 (dd, J ¼ 3.6, 1.2,
HꢀC(3) of Tph); 3.90 (dq, J ¼ 14.8, 1.6, HaꢀC(4)); 3.72 (dq, J ¼ 14.8, 1.6, HbꢀC(4)); 1.93 (t, J ¼ 1.6,
MeꢀC(2)). 13C-NMR: 193.0 (C¼O); 171.3 (C(2)); 149.3; 144.6; 140.9; 131.4; 128.6; 128.5; 128.1; 126.8;
126.0; 125.8; 125.5; 112.6 (C(3)); 89.7 (C(5)); 47.1; 15.8. LC/ESI-MS: 347 (100, [M þ H]þ). Anal. calc. for
C22H18O2S: C 76.3, H 5.2, S 9.3; found: C 76.2, H 5.3, S 9.2.

Helvetica Chimica Acta – Vol. 95 (2012)
803
1-[4,5-Dihydro-2,5-diphenyl-5-(2-thienyl)furan-3-yl]ethanone (8b): Yield 186.9 mg (54%). Yellow
oil. IR: 3100, 3073 (arom. CꢀH), 2947, 2928, 2864 (aliph. CꢀH), 1621 (C¼O). 1H-NMR: 7.63 – 7.65 (m, 2
arom. H); 7.26 – 7.54 (m, Ph, HꢀC(5) of Tph); 6.90 – 6.94 (m, 2 H of Tph); 3.97 (d, J ¼ 15.0, HaꢀC(4));
3.80 (d, J ¼ 14.8, HbꢀC(4)); 1.97 (s, MeCOꢀC(3)). 13C-NMR: 194.6 (C¼O); 171.3 (C(2)); 149.4; 144.6;
131.0; 130.9; 129.6; 128.6; 128.2; 126.8; 126.0; 125.7; 125.6; 114.9 (C(5)); 89.7 (C(3)); 47.2; 29.1. LC/ESI-
MS: 347 (100, [M þ H]þ). Anal. calc. for C22H18O2S: C 76.3, H 5.2, S 9.3; found: C 76.4, H 5.3, S 9.3.
[4,5-Dihydro-2-methyl-5-(4-methylphenyl)-5-(2-thienyl)furan-3-yl]phenylmethanone (8c): Yield
118.8 mg (33%). Light yellow oil. IR: 3057, 3024 (arom. CꢀH), 2920, 2866 (aliph. CꢀH), 1612 (C¼O).
1H-NMR: 7.56 – 7.59 (m, 2 arom. H); 7.36 – 7.48 (m, 5 arom. H); 7.27 (dd, J ¼ 5.2, 1.2, HꢀC(5) of Tph);
7.19 – 7.20 (m, 2 arom. H); 6.93 (dd, J ¼ 5.0, 4.0, HꢀC(4) of Tph); 6.91 (dd, J ¼ 4.0, 1.2, HꢀC(3) of Tph);
3.91 (dq, J ¼ 14.8, 1.6, HaꢀC(4)); 3.74 (dq, J ¼ 14.8, 1.6, HbꢀC(4)); 2.37 (s, MeC6H4); 1.95 (t, J ¼ 1.6,
MeꢀC(2)). LC/ESI-MS: 361 (100, [M þ H]þ). Anal. calc. for C23H20O2S: C 76.6, H 5.6, S 8.9; found: C
76.5, H 5.7, S 8.9.
1-[4,5-Dihydro-5-(4-methylphenyl)-2-phenyl-5-(2-thienyl)furan-3-yl]ethanone (8d): Yield 201.6 mg
(56%). Light yellow oil. IR: 3047 (arom. CꢀH), 2922 (aliph. CꢀH), 1623 (C¼O). 1H-NMR: 7.64 (dd, J ¼
8.0, 1.2, 2 arom. H); 7.45 – 7.52 (m, Ph, HꢀC(5) of Tph); 7.42 (d, J ¼ 8.0, 2 arom. H); 7.25 – 7.30 (m, 1 arom.
H); 7.19 (d, J ¼ 8.0, 2 arom. H); 6.94 (dd, J ¼ 4.0, 1.2, 2 H of Tph); 3.95 (d, J ¼ 14.8, HaꢀC(4)); 3.80 (d, J ¼
14.8, HbꢀC(4)); 2.36 (s, MeC6H4); 1.97 (s, MeꢀC(2)). LC/ESI-MS: 361 (100, [M þ H]þ). Anal. calc. for
C23H20O2S: C 76.6, H 5.6, S 8.9; found: C 76.5, H 5.5, S 9.0.
[5-(4-Fluorophenyl)-4,5-dihydro-2-methyl-5-(2-thienyl)furan-3-yl]phenylmethanone (8e): Yield
1
138.3 mg (38%). Yellow oil. IR: 3069 (arom. CꢀH), 2924 (aliph. CꢀH), 1610 (C¼C). H-NMR: 7.57 –
7.61 (m, 2 arom. H); 7.40 – 7.48 (m, 5 arom. H); 7.28 (dd, J ¼ 5.2, 1.2, HꢀC(5) of Tph); 7.07 (m, 2
arom. H); 6.95 (dd, J ¼ 5.2, 4.0, HꢀC(4) of Tph); 6.91 (dd, J ¼ 4.0, 1.2, HꢀC(3) of Tph); 3.93 (dq, J ¼ 14.4,
1.2, HaꢀC(4)); 3.72 (dd, J ¼ 14.4, 1.2, HbꢀC(4)); 1.95 (t, J ¼ 1.2, MeꢀC(2)). 13C-NMR: 193.0 (C¼O); 166.6
(C(2)); 163.7; 161.3; 149.1; 140.8; 140.5; 140.4; 131.5; 128.6; 128.2; 127.5; 127.4; 126.9; 126.2; 125.9; 115.6;
115.4; 112.6 (C(3)); 89.3 (C(5)); 47.1; 15.8. LC/ESI-MS: 365 (100, [M þ H]þ). Anal. calc. for C22H17FO2S:
C 72.5, H 4.7, F 5.2, S 8.8; found: C 72.4, H 4.8, F 5.2 S 8.7.
1-[5-(4-Fluorophenyl)-4,5-dihydro-2-phenyl-5-(2-thienyl)furan-3-yl]ethanone (8f): Yield 203.8 mg
(56%). Yellow oil. IR: 3098, 3073 (arom. CꢀH), 2947, 2926, 2862 (aliph. CꢀH), 1623 (C¼O). 1H-NMR:
7.60 – 7.65 (m, 2 arom. H); 7.47 – 7.51 (m, 5 arom. H); 7.28 – 7.30 (m, 1 arom. H); 7.06 – 7.10 (m, 2 arom. H);
6.93 – 6.96 (m, 2 H of Tph); 3.97 (d, J ¼ 15.2, HaꢀC(4)); 3.77 (d, J ¼ 15.2, HbꢀC(4)); 1.99 (s,
MeCOꢀC(3)). 13C-NMR: 194.5 (C¼O); 164.3 (C(2)); 163.8; 161.3; 149.2; 140.5; 131.1; 130.7; 129.6;
128.7; 127.6; 127.5; 127.0; 126.2; 125.7; 115.6; 115.4; 114.9 (C(3)); 89.3 (C(5)); 47.2; 29.1. LC/ESI-MS: 365
(100, [M þ H]þ). Anal. calc. for C22H17FO2S: C 72.5, H 4.7, F 5.2, S 8.8; found: C 72.5, H 4.8, F 5.1, S 8.7.
[3a,4,5,6,7,7a-Hexahydro-2-methyl-7a-(2-thienyl)benzofuran-3-yl]phenylmethanone (8g): Yield
110.2 mg (34%). Yellow oil. IR: 3067, 3028 (arom. CꢀH), 2938, 2864 (aliph. CꢀH), 1635 (C¼O).
1H-NMR: 7.55 – 7.59 (m, 2 arom. H); 7.47 – 7.50 (m, 1 arom. H); 7.40 – 7.42 (m, 2 arom. H); 7.26 (dd, J ¼
5.0, 1.2, HꢀC(5) of Tph); 7.11 (dd, J ¼ 3.6, 1.2, HꢀC(3) of Tph); 6.90 (dd, J ¼ 5.0, 3.6, HꢀC(4) of Tph);
3.71 (tq, J ¼ 6.0, 1.2, HꢀC(3a)); 2.11 – 2.25 (m, 2 H); 1.79 – 1.93 (m, 2 H); 1.74 (d, J ¼ 1.2, MeꢀC(2));
1.56 – 1.69 (m, 2 H); 1.44 – 1.54 (m, 2 H). LC/ESI-MS: 325 (100, [M þ H]þ). Anal calc. for C20H20O2S: C
74.0, H 6.2, S 9.9; found: C 74.0, H 6.3, S 9.8.
1-[3a,4,5,6,7,7a-Hexahydro-2-phenyl-7a-(2-thienyl)benzofuran-3-yl]ethanone (8h): Yield 129.6 mg
1
(40%). Yellow oil. IR: 3076 (arom. CꢀH), 2934, 2861 (aliph. CꢀH), 1617 (C¼O). H-NMR: 7.54 – 7.56
(m, 2 arom. H); 7.41 – 7.47 (m, 3 arom. H); 7.22 (dd, J ¼ 5.2, 1.2, HꢀC(5) of Tph); 7.07 (dd, J ¼ 3.6, 1.2,
HꢀC(3) of Tph); 6.97 (dd, J ¼ 5.2, 3.6, HꢀC(4) of Tph); 3.57 (t, J ¼ 6,8, HꢀC(3a)); 2.38 (dt, J ¼ 14.8, 4.4,
HaꢀC(4)); 2.18 – 2.22 (m, 1 H); 1.94 – 2.04 (m, 1 H); 1.89 (s, MeCOꢀC(3)); 1.59 – 1.67 (m, 4 H); 1.38 –
1.44 (m, 1 H). LC/ESI-MS: 325 (100, [M þ H]þ). Anal. calc. for C20H20O2S: C 74.0, H 6.2, S 9.9; found:
C 74.1, H 6.4, S 9.7.

804
Helvetica Chimica Acta – Vol. 95 (2012)
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Received October 14, 2011