Manganese(III) acetate catalyzed oxidative radical additions of α-dicarbonyl compounds to 1- and 2-phenylcyclohepta-1,3,5-triene

Article abstract of DOI:10.1002/hlca.201000463

Manganese(III) acetate catalyzed oxidative radical-addition reactions of α-dicarbonyl compounds such as methyl acetoacetate (6), acetylacetone (7), and dimedone (8) to the mixture of 1- and 2-phenylcyclohepta-1,3,5-triene (4 and 5) were investigated (Scheme1). The 1-phenylcyclohepta-1,3,5-triene (4) formed mainly [2+3] and [4+3] dihydrofuran addition products derived from cycloheptatriene and [2+3] dihydrofuran addition products derived from the norcaradiene structure. The 2-phenylcyclohepta-1,3,5-triene (5) formed mainly [6+3] dihydrofuran addition products derived from cycloheptatriene and [4+3] dihydrofuran addition products derived from the norcaradiene structure. The structures of isolated products were established by their spectroscopic data (IR, ¹H- and ¹³C-NMR, MS, and elemental analysis) and comparison with literature data. The formation mechanism of the products is discussed. Copyright

Full text of DOI:10.1002/hlca.201000463

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Manganese(III) Acetate Catalyzed Oxidative Radical Additions of
a-Dicarbonyl Compounds to 1- and 2-Phenylcyclohepta-1,3,5-triene
by Esra Findik* and Mustafa Ceylan
Department of Chemistry, Faculty of Arts and Sciences, Gaziosmanpasa University, TR-60250 Tokat
(phone: þ 90-356-2521616; fax: þ 90-356-2521585; e-mail: esrafndk@gmail.com)
Manganese(III) acetate catalyzed oxidative radical-addition reactions of a-dicarbonyl compounds
such as methyl acetoacetate (6), acetylacetone (7), and dimedone (8) to the mixture of 1- and 2-
phenylcyclohepta-1,3,5-triene (4 and 5) were investigated (Scheme 1). The 1-phenylcyclohepta-1,3,5-
triene (4) formed mainly [2 þ 3] and [4 þ 3] dihydrofuran addition products derived from cyclo-
heptatriene and [2 þ 3] dihydrofuran addition products derived from the norcaradiene structure. The 2-
phenylcyclohepta-1,3,5-triene (5) formed mainly [6 þ 3] dihydrofuran addition products derived from
cycloheptatriene and [4 þ 3] dihydrofuran addition products derived from the norcaradiene structure.
The structures of isolated products were established by their spectroscopic data (IR, 1H- and 13C-NMR,
MS, and elemental analysis) and comparison with literature data. The formation mechanism of the
products is discussed.
Introduction. – Mn(OAc)3-Promoted additions of 1,3-dicarbonyl compounds to
alkenes [1], sterically hindered alkenes [2], bicyclic alkenes [3], alkynes [4], imines [5],
a,b-unsaturated amides [6], and a,b-unsaturated ketones [7] such as chalcones have
been reported. But, there are only a few studies on the addition of 1,3-dicarbonyl
compounds to conjugated diene and triene systems particularly cycloheptatriene
(CHT) [8]. Moreover, CHT is known to undergo the DielsꢀAlder reaction with various
dienophiles [9]. In most cases, the formed adduct possesses a tricyclo[3.2.2.02,4]nonane
skeleton 1 instead of that of a simple [2 þ 4] cycloadduct 2. The skeleton of type 3 is
formed by [2 þ 6] cycloaddition reactions [9].
In this work, we investigated the reactions of 1- and 2-phenylcyclohepta-1,3,5-triene
(4 and 5) with 1,3-dicarbonyl compounds and found cycloadducts of types 2 and 3
besides products of type 1.
Results and Discussion. – The starting materials 4 and 5 were synthesized as
described in our recently published report [10]. The reaction of the mixture 4/5 with
Mn(OAc)3 and methyl acetoacetate (¼ methyl 3-oxobutanoate; 6) in AcOH at 608
ꢀ 2011 Verlag Helvetica Chimica Acta AG, Zꢁrich

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gave eight products: three rearrangement products 9a – 9c, three 1:1 adducts, namely
the [4 þ 3]p adduct 10, the [6 þ 3]p adduct 11, and the [2 þ 3]p adduct 12 (via the
norcaradiene structure of 5), and two 1:2 adducts 13 and 14 (Scheme 1). The products
9 – 14 were isolated by repeated silica-gel column chromatography.
Scheme 1
The structures of the [1,1’-biphenyl]carboxaldehydes 9a – 9c were determined by
spectroscopic data and comparison with authentic samples [10]. In the addition
reaction of 1,3-dicarbonyl compounds to cycloheptatriene derivatves, similar rear-
rangements have been reported by Tsuruta et al. [8] from the reaction of cyclo-
heptatriene-7-carboxaldehyde and of its dimethyl acetal. Moreover, the rearrangement
products [1,1’-biphenyl]carboxaldehydes 9a – 9c have been obtained by oxidation of 4
and 5 with air O2 and/or CrO3 [10].
The [4 þ 3]p adduct 10 of 4 exhibited the signals of four olefinic H-atoms and nine
aliphatic H-atoms in the 1H-NMR spectrum and only one signal for a C¼O group in the

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13C-NMR spectrum. The molecular-ion peak in the MS at m/z 282 (Mþ) indicated a 1:1
adduct. The CH2 group resonated as an AB part of an ABXY system (two ddd) at d(H)
2
2.47 and 2.32 with coupling constants J ¼ 20.0, 9.6, and 2.0 Hz. The J coupling of the
CH2 moiety (J ¼ 20.0 Hz) is in agreement with literature data. Asao and co-workers
[11] have obtained a type-2 cycloadduct from the reaction of CHT and singlet oxygen;
2
and they reported a J value of 19.0 Hz. Consequently, 10 must be the [4 þ 3]p
cycloadduct of 4.
The [6 þ 3]p adduct 11 of 5 showed the signals of three olefinic H-atoms and ten
1
aliphatic H-atoms in the H-NMR spectrum and again one signal for a C¼O group in
the 13C-NMR spectrum. The molecular-ion peak at m/z 282 (Mþ) indicated a 1:1
adduct. The three olefinic H-atoms resonated at d(H) 6.26 – 6.21 as a m. While the
bridgehead HꢀC(6) gave rise to a d at d(H) 5.15 (J ¼ 9.2 Hz), its counterpart HꢀC(1)
resonated as a t at d(H) 3.43 (J ¼ 10.2 Hz). The H-atoms of the CH2 bridge appeared as
a d at d(H) 2.91 (J ¼ 12.8 Hz) and a dd at d(H) 2.52 (J ¼ 12.8, 10.2 Hz). A similar
structure and spectral results were obtained by Mori and Takeshita [12] for the addition
product of 1,4-benzoquinone to cycloheptatriene.
The [2 þ 3]p adduct 12 of methyl acetoacetate (6) and the norcaradiene
(¼ bicyclo[4.1.0]heptadiene) valence isomer of 5 showed the olefinic H-atom as d at
d(H) 5.74 (J ¼ 4.0 Hz) and the neighboring H-atom as dd at d(H) 4.97 (J ¼ 10.8 and
4.0 Hz). The coupling constant (J ¼ 4.0 Hz) clearly indicated a vicinal position of the
two H-atoms. Moreover, the signal at d(H) 0.22 established the presence of a
cyclopropane ring in the structure. Moreover, the molecular-ion peak at m/z 282 (Mþ)
was in accordance with the structure.
The adducts 13 and 14 turned out to be formed from 6 and 11. Their NMR spectrum
showed that they were isomers of each other. Furthermore, the signal of one olefinic H-
1
atom in the H-NMR spectrum and two signals for 2 C¼O groups in the 13C-NMR
spectrum as well as the molecular-ion peak at m/z 396 (Mþ) in the MS clearly indicated
the presence of two methyl acetoacetate units.
The reaction of the mixture 4/5 with Mn(OAc)3 and acetylacetone (¼ pentane-2,4-
dione; 7) in AcOH at 608 gave six products, the [1,1’-biphenyl]carboxaldehydes 9a – 9c
and 15 – 17, which were isolated by silica-gel column chromatography. On the basis of
NMR spectroscopy, the first product, 15, was established to be a [4 þ 3]p adduct of the
norcaradiene valence isomer of 4. Two olefinic H-atoms resonated as an AB system at
d(H) 5.90 (dd, J ¼ 4.8, 2.2 Hz) and 5.64 (dd, J ¼ 4.8, 2.0 Hz). The CH2 group of the
cyclopropane moiety gave rise to a md at d(H) 1.80 (J ¼ 12.5 Hz). Furthermore, the
13C-NMR spectrum showed 16 C-signals (two overlapped, i.e., 18 signals), and the
molecular-ion peak appeared at m/z 266 (Mþ) confirming the structure of 15.
The [6 þ 3]p adduct 16 of 7 and 5 had an 1H-NMR spectrum very similar to that of
[6 þ 3]p adduct 11 derived from the reaction of methyl acetoacetate. All spectral data
and the molecular-ion peak at m/z 266 (Mþ) are in agreement with the proposed
structure. A similar product and spectral results were obtained by Balci and co-workers
[13] from the Mn(OAc)3-catalyzed addition of acetylacetone to cyloheptatriene.
The structure of the condensation product 17 of acetylacetone (7) with 4-
phenylbenzaldehyde (9c) was confirmed by the following spectroscopic data: Signals of
1
one olefinic and nine aromatic H-atoms in the H-NMR spectrum and of fourteen C-
atoms in the 13C-NMR spectrum (eight aromatic C, two olefinic C, two C¼O, and two

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aliphatic C-atoms). The molecular-ion peak at m/z 264 (Mþ) was consistent with a
symmetrical structure and condensation product.
The reaction of the mixture 4/5 with dimedone (¼ 5,5-dimethylcyclohexane-1,3-
dione; 8) gave products 18, 19, and 20 which were isolated by silica-gel column
chromatography. The [2 þ 3]p adduct 18 of 4 and 8 had a molecular-ion peak at m/z 306
1
(Mþ), consistent with a 1:1 adduct. Its H-NMR spectrum showed the signals in
agreement with the structure: d(H) 6.19 (A of AB (dd), J ¼ 11.7, 7.4 Hz, HꢀC(9)), 6.05
(d, J ¼ 7.4 Hz, HꢀC(8)), 5.86 (B of AB (dd, J ¼ 11.7, 5.8 Hz, HꢀC(10)), 5.00 – 4.98 (m,
HꢀC(5a)), and 4.00 (d, J ¼ 5.8 Hz, HꢀC(10a)). The coupling patterns of the olefinic H-
atoms and the allylic HꢀC(10a) (J(8,9) ¼ 7.4 Hz, J(9,10) ¼ 11.7 Hz, and J(10,10a) ¼
5.8 Hz) confirmed the structure. The CH2 group of the cycloheptadiene moiety
resonated as dm at d(H) 2.53 – 2.48 (Jgem ¼ 12.4 Hz). A similar structure and coupling
pattern have been observed by Takeshita et al. [14] for the addition product of
acenaphthenequinone (¼acenaphthylene-1,2-dione) and CHT. Moreover, a similar
product and spectral results were obtained by Sꢀdemen et al. [13] for the Mn(OAc)3-
catalyzed addition product of dimedone and CHT.
The structure of the [6 þ 3]p adduct 19 of 5 and dimedone was derived from the
following spectroscopic data: appearance of the signals of three olefinic H-atoms in the
1H-NMR spectrum and only one signal for a C¼O group in the 13C-NMR spectrum as
well as the molecular-ion peak at m/z 306 (Mþ), indicating the presence of a 1:1 adduct
([6 þ 3]p adduct). The olefinic H-atoms resonated as a m at d(H) 6.26 – 6.22. The
spectrum was very similar to that of compound 11. Additionally, a similar product and
spectral results were obtained by Balci and co-workers [13] for the Mn(OAc)3-
catalyzed addition of dimedone to CHT.
The norcaradiene-type adduct 20, in analogy to the [4 þ 3]p adduct 15 from 4/5 with
7, showed olefinic H-atoms resonating as AB system at d(H) 5.94 (dd, J ¼ 5.2, 2.0 Hz)
and 5.56 (dd, J ¼ 5.2, 2.4 Hz). The cyclopropane moiety gave rise to a broad d at d(H)
3.37 (J ¼ 5.5 Hz, 2 H), a dt at d(H) 1.78 (J ¼ 13.6, 2.0 Hz, 1 H), and a broad d at d(H)
1.10 (J ¼ 5.2 Hz, 1 H). This data and the molecular-ion peak at m/z 306 (Mþ) were in
1
accordance with the structure. In addition, the H-NMR spectrum of 20 was very
similar to that of compound 15.
The rearrangement products 9a – 9c were not detected in the reaction with
dimedone (8) since the reaction rate of dimedone (conversion after 5 min) was faster
than that of methyl acetoacetate (6; conversion after 30 min) and acetylacetone (7;
conversion after 3 h).
The mechanism of the formation of [4 þ 3]p adduct 10 and [2 þ 3]p adduct 18 from
4 can be explained as shown in Scheme 2. After formation of [MnIII(enolato)] complex
A from Mn(OAc)3 and the 1,3-dicarbonyl compound [12], Mn3þ is reduced to Mn2þ
resulting in the resonance-stabilized radical intermediate B. Radical B is then added to
C(4) of 1-phenylcyclohepta-1,3,5-triene (4) resulting in 21 which is mesomeric with the
more stable benzylic radical 22. This radical is oxidized to the carbocation 23 with
Mn(OAc)3. Then, the intramolecular cyclization can lead to product 10, which
represents the [4 þ 3]p adduct. Addition of intermediate B to C(5) of 4 gives the
radical 24, which is oxidized to carbocation 25. The latter affords the [2 þ 3]p adduct 18
by cyclization.

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Scheme 2
Addition of intermediate B to C(5) of the norcaradiene valence isomer 26 of 2-
phenylcyclohepta-1,3,5-triene (5) results in the formation of radical 27, which is
oxidized to carbocation 28. The cyclization of carbocation 28 leads to the [2 þ 3]p
adduct 12 (Scheme 3). Addition of radical intermediate B to C(6) of 5 gives the
mesomeric radicals 29 and 30. Oxidation of the latter to carbocation 31 followed by
cyclization gives rise to [6 þ 3]p adducts 11, 16, and 19 (Scheme 3).
Finally, addition of intermediate B to C(5) of norcaradiene valence isomer 32 of 1-
phenylcyclohepta-1,3,5-triene (4) gives the allyl radicals 33/34. Oxidation leads to
carbocation 35, which cyclizes to the [4 þ 3]p adducts 15 and 20 (Scheme 4).
Conclusions. – We examined the manganese(III) acetate catalyzed oxidative
radical-addition reactions of methyl acetoacetate (6), acetylacetone (7), and dimedone
(8) to 1- and 2-phenylcyclohepta-1,3,5-triene (4 and 5). It was found that the reactions
of 1-phenylcycloheptatriene 4 were slower than those of 2-phenylcycloheptatriene 5.
The [2 þ 3] and [4 þ 3] dihydrofuran addition products of type 2 such as 18 and 10,
respectively, derived from the cycloheptatriene structure, and the [4 þ 3] dihydrofuran
addition products of type 1 such as 15 and 20, derived from the norcaradiene structure,
were obtained from 4. The [6 þ 3] dihydrofuran addition products of type 3 such as 11,
16, and 19, derived from the cycloheptatriene structure, and the [4 þ 3] dihydrofuran
addition product 12, derived from the norcaradiene structure, were obtained from 5.
The 1:2 adducts 13 and 14 were obtained from the reaction of methyl acetoacetate (6).

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Helvetica Chimica Acta – Vol. 94 (2011)
Scheme 3
Scheme 4
In case of the methyl acetoacetate and acetylacetone (7), the rearrangement products
9a – 9c and condensation product 17 were isolated.
The authors are indebted to the Department of Chemistry (Gaziosmanpasa University), to Prof. Dr.
Hasan SeÅen (Atatꢁrk University) for fruitful discussions, and to Dr. Ebru Mete, Hatice SeÅinti, for
recording mass spectra.
Experimental Part
1. General. Thin layer chromatography (TLC): silica gel 60 GF254 (Merck). Column chromatography
(CC): silica gel 60 (0.063 – 0.200 mm; Merck). M.p.: Electrothermal 9100 apparatus. IR Spectra (KBr or
.
liq.): Jasco-430 FT/IR spectrometer; ˜n in cmꢀ1 1H- and 13C-NMR Spectrum: Bruker-Avance-III
instrument; in CDCl3; d in ppm rel. to Me4Si as internal standard, J in Hz. MS: Thermofinnigan Trace
GC/Trace DSQ/A1300 (quadrupol, EI (70 eV)) equipped with a SGE-BPX5 MS cap. column (30 m ꢁ
0.25 mm i.d.; 0.25 mm); in m/z (rel. %). Elemental analyses: LECO-CHNS-932 elemental analyzer.

Helvetica Chimica Acta – Vol. 94 (2011)
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2. Reaction of 4/5 with 1,3-Dicarbonyl Compounds: General Procedure. A mixture of Mn(OAc)3
(6.4 g, 23.6 mmol) in AcOH (15 ml) was heated under N2 at 808 until it dissolved and then cooled to 608.
A soln. of 4/5 (1.0 g, 5.9 mmol) and 1,3-dicarbonyl derivative (23.6 mmol) in AcOH (5 ml) was added to
this mixture. The reaction was finished when the dark brown color of the soln. disappeared. Then AcOH
was evaporated, H2O (10 ml) added to the residue, and the mixture extracted with AcOEt (3 ꢁ 20 ml).
The combined org. phase was neutralized with sat. NaHCO3 soln., dried (anh. Na2SO4), and
concentrated. The crude products were separated and purified by CC (SiO2, hexane/AcOEt) or prep.
TLC (SiO2 (20 ꢁ 20 cm plates, 2 mm thickness), using hexane/AcOEt 9 :1).
3. Reaction of Methyl Acetoacetate (6) with 4/5. After completion of the reaction (30 min), the crude
products were separated by CC (silica gel hexane/AcOEt 9 :1): [1,1’-biphenyl]carboxaldehydes 9a – 9c
(45 mg, 4%; colorless liquid) and 10 – 14, in this order.
Methyl 3-Methyl-1-phenyl-2-oxabicyclo[3.3.2]deca-3,6,9-triene-4-carboxylate (10): Yield 165 mg
(10%). Yellowish liquid. IR (KBr): 3060, 3021, 2950, 2850, 1697, 1649, 1490, 1436, 1226, 1099, 989,
1
752, 698. H-NMR (400 MHz, CDCl3): 7.32 – 7.29 (m, 5 H); 6.31 (ddd, J ¼ 12.0, 8.4, 5.6, HꢀC(9)); 6.12
(dd, J ¼ 12.0, 2.0, HꢀC(10)); 6.09 (d, J ¼ 12.0, HꢀC(7)); 5.89 (dd, J ¼ 12.0, 5.6, HꢀC(6)); 3.68 (s, MeO);
3.41 (d, J ¼ 2.4, HꢀC(5)); 2.47 (ddd, J ¼ 20.0, 9.6, 2.0, HꢀC(8)); 2.38 (s, MeꢀC(3)); 2.32 (ddd, J ¼ 20.0,
9.6, 2.0, HꢀC(8)). 13C-NMR (100 MHz, CDCl3): 166.3; 165.9; 144.6; 135.8; 134.0; 128.2; 127.4; 127.3;
124.3; 124.2; 106.7; 93.6; 61.7 50.7; 30.4; 14.2. MS: 282 (20, Mþ), 250 (45), 235 (25), 207 (100), 179 (90),
165 (85), 152 (38). Anal. calc. for C18H18O3 (282.13): C 76.57, H 6.43; found: C 76.77, H 6.24.
Methyl (1RS,6RS)-8-Methyl-5-phenyl-7-oxabicyclo[4.3.1]deca-2,4,8-triene-9-carboxylate (11): Yield
245 mg (14%). Yellowish liquid. IR (KBr): 3060, 3021, 2950, 2850, 1704, 1639, 1436, 1253, 1211, 1087, 755,
698. 1H-NMR (400 MHz, CDCl3): 7.55 (br. d, J ¼ 7.6, 2 H); 7.37 – 7.24 (m, 3 H); 6.26 – 6.21 (m, 3 olef. H);
5.15 (d, J ¼ 9.2, HꢀC(6)); 3.78 (s, MeO); 3.43 (t, J ¼ 10.2, HꢀC(1)); 2.91 (d, J ¼ 13.6, HꢀC(10a)); 2.52 (t,
J ¼ 12.0, HꢀC(10b)); 2.26 (s, MeꢀC(8)); data in good agreement with those given in [13]. 13C-NMR
(100 MHz, CDCl3): 167.9; 166.2; 145.4; 142.2; 130.1; 128.5 (2 C); 128.1; 126.3; 125.8 (2 C); 122.7; 106.7;
71.13; 50.84; 34.7; 33.52; 14.23. MS: 282 (14, Mþ), 250 (32), 207 (100), 179 (58), 165 (36), 152 (18), 142
(28), 115 (28), 103 (10). Anal. calc. for C18H18O3 (282.13): C 76.57, H 6.43; found: C 76.34, H 6.56.
Methyl (3aRS,5aSR,6aRS,6bRS)-3a,5a,6a,6b-Tetrahydro-2-methyl-5-phenyl-6aH-cyclopropa[e]ben-
zofuran-1-carboxylate (12): Yield 275 mg (16%). Yellowish liquid. IR (KBr): 3060, 3021, 2950, 2927,
1685, 1635, 1440, 1249, 1222, 1083, 752, 698. 1H-NMR (400 MHz, CDCl3): 7.57 (br. d, J ¼ 7.2, 2 H); 7.40 –
7.29 (m, 3 H); 5.74 (d, J ¼ 4.0, HꢀC(4)); 4.97 (dd, J ¼ 10.8, 4.0, HꢀC(3a)); 3.83 (d, J ¼ 10.8, HꢀC(6b));
3.78 (s, MeO); 2.26 (s, MeꢀC(2)); 1.77 (dd, J ¼ 13.2, 8.4, HꢀC(5a)); 1.66 (ddd, J ¼ 12.5, 8.4, 4.8, HꢀC(6));
1.27 (ddd, J ¼ 12.5, 8.4, 4.8, HꢀC(6)); 0.22 (dd, J ¼ 10.4, 4.4, HꢀC(6a)). 13C-NMR (100 MHz, CDCl3):
167.96; 166.7; 144.4; 140.6; 128.4 (2 C); 127.9; 125.8 (2 C); 115,1; 105.9; 76.7; 50.8; 38.4; 18.5; 14.8; 13.4;
11.8. MS: 282 (13, Mþ), 250 (98), 232 (35), 222 (55), 207 (100) 179 (98), 167 (90), 152 (40). Anal. calc. for
C18H18O3 (282.13): C 76.57, H 6.43; found: C 76.83, H 6.52.
Dimethyl (6RS,10RS)-3a,6,10,10a-Tetrahydro-2,8-dimethyl-5-phenyl-6,10-methanofuro[2,3-e]ox-
onin-3,9-dicarboxylate (13): Yield 205 mg (12%). Yellowish liquid. IR (KBr): 3060, 3021, 2950, 2854,
1
1727, 1623, 1436, 1245, 1083, 977, 755, 701. H-NMR (400 MHz, CDCl3): 7.48 – 7.44 (m, 2 H); 7.27 – 7.21
(m, 3 H); 5.45 (d, J ¼ 5.0, HꢀC(4)); 5.19 (dd, J ¼ 12.6, 6.0, 1 H); 4.91 (d, J ¼ 7.6, 1 H); 3.78 (s, MeO); 3.75
(s, MeO); 2.42 (d, J ¼ 13.6, 1 H); 2.26 (s, MeꢀC(8)); 2.24 (s, MeꢀC(2)); 2.16 (d, J ¼ 5.6, 1 H); 2.12 (m,
2 H). 13C-NMR (100 MHz, CDCl3): 169.9; 167.6; 165.8; 164.7; 143.6; 129.8; 127.6; 127.0; 123.1; 104.4;
103.5; 82.1; 74.1; 51.1; 50.1 34.8; 27.3; 26.5; 20.3; 14.9. MS: 396 (5, Mþ), 364 (8), 280 (20), 247 (15), 219
(8), 200 (25) 179 (98), 165 (23), 153 (100), 141 (15), 115 (13). Anal. calc. for C23H24O6 (396.16): C 69.68,
H 6.10; found: C 69.54, H 6.32.
Dimethyl (4RS,8SR)-3a,4,8,10a-Tetrahydro-2,6-dimethyl-9-phenyl-4,8-methanofuro[2,3-e]oxonin-
3,5-dicarboxylate (14): Yield 138 mg (8%). Yellowish liquid. IR (KBr): 3064, 3023, 2952, 2851, 1730,
1628, 1439, 1247, 1086, 979, 758, 704. 1H-NMR (400 MHz, CDCl3): 7.35 – 7.19 (m, 5 H); 6.20 (dd, J ¼ 11.6,
HꢀC(10)); 5.55 (dd, J ¼ 11.6, 1.6, HꢀC(10a)); 5.29 (br. d, J ¼ 10.0, 1 H); 3.82 (s, MeO); 3.75 (s, MeO);
2.92 (dd, J ¼ 11.2, 5.6, 1 H); 2.51 – 2.38 (m, 1 H); 2.35 – 2.26 (m, 1 H); 2.18 (s, MeꢀC(6)); 2.12 – 2.10 (m,
1 H); 2.04 (s, MeꢀC(2)). 13C-NMR (100 MHz, CDCl3): 168.3; 168.06; 166.218; 165.8; 138.4; 128.8; 128.4;
128.1; 127.7; 127.5; 105.8 ; 83.3; 52.5; 51.6; 43.7; 43.3; 32.2; 26.0; 14.3. MS: 396 (2, Mþ), 279 (8), 167 (75),
149 (100), 113 (23). Anal. calc. for C23H24O6 (396.16): C 69.68, H 6.10; found: C 70.17, H 6.23.

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4. Reaction of Acetylacetone (7) with 4/5. After completion of the reaction (3 h) the crude products
was were separated by CC (silica gel, hexane/AcOEt 9 :1): [1,1’-biphenyl]carboxaldehydes 9a – 9c
(150 mg, 14%; colorless liquid) and 15 – 17, in this order.
1-[(1RS,2SR,4SR,5SR)-7-Methyl-4-phenyl-6-oxatricyclo[3.3.2.02,4]deca-7,9-dien-8-yl]ethanone (15):
Yield 230 mg (18%). Yellowish liquid. IR (KBr): 3060, 3014, 2927, 2854, 1714, 1679, 1596, 1361, 1236, 939,
752, 700. 1H-NMR (400 MHz, CDCl3): 7.37 – 7.34 (m, 5 arom. H); 5.90 (dd, J ¼ 4.8, 2.2, HꢀC(9 or 10));
5.64 (dd, J ¼ 4.8, 2.0, HꢀC(9 or 10)); 3.87 – 3.85 (m, HꢀC(5)); 3.38 – 3.35 (m, 2 H); 2.39 – 2.34 (m, 1 H);
2.32 (s, MeCOꢀC(8)); 2.24 (m, MeꢀC(7)); 1.80 (dm, J ¼ 12.5, HꢀC(2)). 13C-NMR (100 MHz, CDCl3):
194.54; 168.68; 138.02; 132.53; 131.44; 127.94; 127.79; 126.12; 116.54; 95.28; 53.15; 52.42; 49.28; 35.41;
29.50; 15.47. MS: 266 (8, Mþ), 221 (30), 203 (100), 165 (95), 152 (20). Anal. calc. for C18H18O2 (266.13): C
81.17, H 6.81; found: C 81.36, H 6.73.
1-[(1RS,6SR)-8-Methyl-5-phenyl-7-oxabicyclo[4.3.1]deca-2,4,8-trien-9-yl]ethanone (16): Yield
200 mg (16%). Yellowish liquid. IR (KBr): 3056, 3021, 2921, 2854, 1714, 1671, 1357, 1232, 1072, 950,
752, 700.1H-NMR (400 MHz, CDCl3): 7.60 (d, J ¼ 7.6, 2 H); 7.37 (t, J ¼ 8.0, 2 H); 7.25 (t, J ¼ 7.2, 1 H);
6.25 – 6.20 (m, 3 olef. H); 5.06 (d, J ¼ 8.8, HꢀC(6)); 3.46 (t, J ¼ 10.4, HꢀC(1)); 2.82 (br. d, J ¼ 12.8,
HꢀC(10)); 2.45 (br. d, J ¼ 10.4, HꢀC(10)); 2.31 (s, MeCO); 2.26 (m, MeꢀC(8)); data in good agreement
with those given in [13]. 13C-NMR (100 MHz, CDCl3): 193.63; 167.18; 145.78; 141.97; 129.43; 128.58;
128.54; 127.40; 126.04; 125.96; 122.53; 85.58; 52.02; 33.42; 29.16; 15.49. MS: 266 (8, Mþ), 221 (33), 203
(100), 178 (45), 165 (98), 152 (15). Anal. calc. for C18H18O2 (266.13): C 81.17, H 6.81; found: C 81.69, H
6.98.
3-([1,1’-Biphenyl]-4-ylmethylene)pentane-2,4-dione (17): Yield 250 mg (20%). Yellowish crystals.
M.p. 87 – 898. IR (KBr): 3060, 3020, 2923, 2850, 1708, 1654, 1602, 1382, 1245, 1172, 1001, 835, 759, 694.
1H-NMR (400 MHz, CDCl3): 7.63 (t, J ¼ 8.6, 4 arom. H); 7.53 (s, 1 olef. H); 7.48 (t, J ¼ 8.4, 4 arom. H); 7.41
(t, J ¼ 7.4, 1 arom. H); 2.46 (s, Me); 2.36 (s, Me). 13C-NMR (100 MHz, CDCl3): 205.76; 196.44; 143.46;
142.54; 139.68; 139.38; 131.72; 130.35; 128.98; 128.14; 127.63; 127.07; 31.74; 26.52. MS: 264 (100, Mþ), 249
(38), 221 (65), 207 (98), 178 (96), 165 (88), 152 (43), 115 (10). Anal. calc. for C18H16O2 (264.12): C 81.79,
H 6.10; found: C 81.49, H 6.38.
5. Reaction of Dimedone (8) with 4/5. After completion of the reaction (5 min) the crude product was
filtered through a short silica-gel column with hexane/AcOEt 9 :1 which separated unreacted 1-
phenylcyclohepta-1,3,5-triene (4; 0.15 g). Then, filtration was continued with hexane/AcOEt 1:1 which
separated the addition products (0.8 g, total yield 51% rel. to 0.85 g of starting CHT 4/5. The addition
products (0.8 g) were subjected to CC (silica gel, hexane/AcOEt 7:3): 18 – 20, in this order.
(5aRS,10aRS)-2,3,4,5a,6,10a-Hexahydro-3,3-dimethyl-7-phenyl-1H-benzo[b]cyclohepta[d]furan-1-
one (18): Yield 200 mg (13% and 59% rel. to CHT 4). Colorless liquid. IR (KBr): 3060, 3018, 2958, 2927,
2869, 1648, 1612, 1382, 1076, 1029, 755, 696. 1H-NMR (400 MHz, CDCl3): 7.56 (d, J ¼ 7.7, 2 arom. H); 7.37
(t, J ¼ 7.4, 2 arom. H); 7.28 (t, J ¼ 7.4, 1 arom. H); 6.19 (dd (A of AB), J ¼ 11.7, 7.4, HꢀC(9)); 6.05 (d, J ¼
7.4, HꢀC(8)); 5.86 (dd (B of AB), J ¼ 11.7, 5.9, HꢀC(10); 5.00 – 4.98 (m, 1 H); 4.00 (br. d, J ¼ 5.9,
HꢀC(10a)); 2.53 – 2.48 (dm, J ¼ 12.4, 2 HꢀC(6)); 2.28 – 2.02 (m, 4 H); 1.07 (s, MeꢀC(3)); 1.03 (m,
MeꢀC(3)); data in good agreement with those given in [13]. 13C-NMR (100 MHz, CDCl3): 197.6; 168.5;
149.9; 144.3; 129.4; 128.1 (2 C); 127.8; 126.9; 126.7 (2 C); 121.8; 112.7; 72.1; 50.8; 42.5; 32.1; 31.9; 29.37;
28.8; 27.1. MS: 306 (5, Mþ), 293 (10), 252 (100), 194 (50), 154 (85), 115 (70). Anal. calc. for C21H22O2
(306.16): C 82.32, H 7.24; found: C 82.12, H 7.43.
(2RS,7SR)-7,9,10,11-Tetrahydro-10,10-dimethyl-3-phenyl-2,7-methano-1-benzoxonin-8(2H)-one
(19): Yield 150 mg (10% and 12% rel. to CHT 4). Yellowish liquid. IR (KBr): 3018, 2958, 2935, 2873,
1714, 1623, 1394, 1373, 1216, 1037, 752, 700, 665. 1H-NMR (400 MHz, CDCl3): 7.54 (d, J ¼ 7.2, 2 arom. H);
7.34 (t, J ¼ 7.4, 2 arom. H); 7.26 (t, J ¼ 7.2, 1 arom. H); 6.26 – 6.22 (m, 3 olef. H); 5.28 (d, J ¼ 9.3, HꢀC(2));
3.56 (t, J ¼ 10.2, HꢀC(7)); 3.03 (d, J ¼ 12.8, HꢀC(12)); 2.42 (t, J ¼ 12.8, HꢀC(12)); 2.31 – 2.14 (m, 4 H);
1.13 (s, MeꢀC(10)); 1.10 (m, MeꢀC(10)); data in good agreement with those given in [13]. 13C-NMR
(100 MHz, CDCl3): 194.57; 175.10; 145.62; 143.27; 129.79; 128.54; 128.36; 127.47; 125.93; 122.73; 115.71;
87.58; 51.08; 50.06; 37.64; 34.17; 32.66; 29.19; 28.10. MS: 306 (15, Mþ), 293 (100), 222 (10), 191 (48), 179
(16), 165 (55), 114 (20), 105 (43). Anal. calc. for C21H22O2 (306.16): C 82.32, H 7.24; found: C 82.54, H
7.52.

Helvetica Chimica Acta – Vol. 94 (2011)
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(1aRS,2RS,8SR,8aRS)-1,1a,2,4,5,6,8,8a-Octahydro-5,5-dimethyl-1a-phenyl-2,8-etheno-7H-cyclopro-
pa[c][1]benzoxepin-7-one (20): Yield 450 mg (28% and 35% rel. to CHT 4). Yellowish iquid. IR (KBr):
1
3060, 3010, 2958, 2927, 2869, 1714, 1619, 1401, 1232, 1135, 790, 759, 696. H-NMR (400 MHz, CDCl3):
7.36 – 7.27 (m, 5 arom. H); 5.94 (dd, J ¼ 5.2, 2.0, 1 olef. H); 5.56 (dd, J ¼ 5.2, 2.4, 1 olef. H); 3.89 (m, 1 H);
3.37 (br. d, J ¼ 5.5, 2 H); 2.46 – 2.21 (m, 4 H); 1.78 (dt, J ¼ 13.6, 2.0, 1 H); 1.10 (br. d, J ¼ 5.2, 1 H); 1.18 (s,
MeꢀC(5)); 1.07 (s, MeꢀC(5)). 13C-NMR (100 MHz, CDCl3): 194.82; 176.69; 137.47; 132.01; 131.98;
128.39; 127.96; 126.37; 116.28; 99.92; 51.60; 51.08; 49.51; 48.73; 38.17; 35.42; 34.20; 28.83; 28.61. MS: 306
(6, Mþ), 292 (4), 240 (100), 184 (98), 156 (95). Anal. calc. for C21H22O2 (306.16): C 82.32, H 7.24; found:
C 82.48, H 7.05.
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Received December 22, 2010