Stereoconvergent generation of a contrasteric syn-bicyclopropylidene (=syn-Cyclopropylidenecyclopropane) by stille-like coupling

Article abstract of DOI:10.1002/hlca.201200291

Stereoisomerically pure endo- and exo-7-halo-7-(trimethylstannyl) benzonorcar-3-enes (=endo- and exo-(1-halo-1a,2,7,7a-tetrahydro-1H-cyclopropa[b] naphthalen-1-yl)trimethylstannane) 4 and 6 were selectively obtained by lithium-tin or magnesium-tin transmetalation in good yields (Scheme 2 and 3). The reaction of these compounds with copper(I) thiophene-2-carboxylate (CuTC) produced in both cases the corresponding C_S-symmetric bicyclopropylidene (=cyclopropylidenecyclopropane) syn-1, a single diastereoisomer (Schemes 5 and 6). The structure of syn-1 was undoubtedly elucidated by X-ray single crystal diffraction. The coupling mechanism of the carbenoid cyclopropane is discussed (Scheme 7). Copyright

Full text of DOI:10.1002/hlca.201200291

Helvetica Chimica Acta – Vol. 96 (2013)
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Stereoconvergent Generation of a Contrasteric syn-Bicyclopropylidene
(¼syn-Cyclopropylidenecyclopropane) by Stille-Like Coupling
by Murat Gꢀneya)b), SelÅuk Es¸sizb)c), Arif Das¸tan*b), Metin Balcid), Ottorino De Lucchie),
Ertan S¸ahinb), and Fabrizio Fabrise)
a
˙
˘
) Agrı Ibrahim ꢀeÅen University, Faculty of Art and Science, Department of Chemistry, TR-04100,
˘
Agrı, Turkey
b) Atatꢁrk University, Faculty of Science, Department of Chemistry, TR-25240 Erzurum, Turkey
(phone.: þ 90-442-2314405; fax: þ 90-442-2360948; email: adastan@atauni.edu.tr)
c) Hakkari University, Faculty of Engineering, Department of Chemical Engineering,
TR-30000 Hakkari, Turkey
d) Middle East Technical University, Faculty of Science, Department of Chemistry, TR-06800 Ankara,
Turkey
e
`
) Dipartimento di Chimica, Universita Caꢂ Foscari di Venezia, Dorsoduro 2137, I-30123 Venezia
Stereoisomerically pure endo- and exo-7-halo-7-(trimethylstannyl)benzonorcar-3-enes (¼endo- and
exo-(1-halo-1a,2,7,7a-tetrahydro-1H-cyclopropa[b]naphthalen-1-yl)trimethylstannane) 4 and 6 were
selectively obtained by lithiumꢀtin or magnesiumꢀtin transmetalation in good yields (Scheme 2 and
3). The reaction of these compounds with copper(I) thiophene-2-carboxylate (CuTC) produced in both
cases the corresponding CS-symmetric bicyclopropylidene (¼cyclopropylidenecyclopropane) syn-1, a
single diastereoisomer (Schemes 5 and 6). The structure of syn-1 was undoubtedly elucidated by X-ray
single crystal diffraction. The coupling mechanism of the carbenoid cyclopropane is discussed
(Scheme 7).
Introduction. – Bicyclopropylidenes (¼cyclopropylidenecyclopropanes) display a
wide reactivity, ranging from the expected reactions of a tetrasubstituted olefin with
electrophiles to the intriguing cascade-reaction recently reported by de Meijere and co-
workers. [1]. Many procedures for the preparation and derivatization of bicyclopro-
pylidenes are reported [1][2], including coupling of carbenes generated in situ from
gemminally dihalo-substituted cyclopropanes [3], which, in turn, can be obtained by
dihalocarbene insertion in C¼C bonds. The research groups have, for a long time, been
involved in the study of coupling reactions promoted by copper salts [4], and recently
our attention focused on the masked carbene functionality of gemminally-bromo(-
trimethylstannyl)-substituted cyclopropanes. In this article, we describe an efficient and
highly stereoselective synthetic methodology for the preparation of the contrasteric
syn-1a,1’a,2, 2’,7, 7’,7a,7’a-octahydro-1,1’-bi[cyclopropa[b]naphthalenylidene] (syn-1)1)
(Fig. 1). This compound has been previously synthesized by Banwell and co-workers, as
a mixture of syn- and anti-1 in 7 and 11% yield, respectively [5].
1
)
The terms syn/anti in names and key numbers mean that a compound has a cage-like/stair-like
overall gross structure, cf. Fig. 1.
ꢃ 2013 Verlag Helvetica Chimica Acta AG, Zꢁrich

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Helvetica Chimica Acta – Vol. 96 (2013)
Fig. 1. The two possible isomers of bicyclopropylidene 1
Results and Discussion. – The starting material 3 was readily obtained in two steps
from naphthalene, which was selectively reduced at the 1,4 positions [6] followed by
dibromocyclopropanation with tribromomethane and potassium tert-butoxide
(Scheme 1) [7].
Scheme 1. Synthesis of the Dibromo Adduct 3
Although the formation of bicyclopropylidenes can be accomplished by the use of
simple metalating agents [8], the yields and diastereoselectivities of these reactions are
not very good [3b][3i][5][9]. The use of bromostannanes with copper(I) as promoter
of the coupling reaction can provide milder conditions with an efficiency improvement.
When 7,7-dibromobenzonorcar-3-ene (¼1,1-dibromo-1a,2,7,7a-tetrahydro-1H-cyclo-
propa[b]naphthalene; 3) was treated with BuLi at ꢀ 788, and the resulting anion was
quenched with chlorotrimethyltstannane, the endo-trimethylstanyl derivative endo-42)
was isolated as the sole product in 90% yield (Scheme 2). The configuration was
confirmed by a NOESY experiment: the scalar correlation between the Me groups and
the endo benzylic H-atoms was in good agreement with distances observed in
minimized models (MacSpartan Plus, semi-empirical, PM3 basis set), which resulted in
2.32 and 4.29 ꢄ for the endo- and exo-(trimethylstannyl) derivatives, respectively. The
remarkable diastereoselectivity observed with substrate 3 matched the previously
reported results obtained with 2-oxa-7,7-dibromonorcarane [10], 7,7-dibromonorcar-
ane [9d][11], and 7,7-dibromonorcar-2-ene [12].
Scheme 2. Reaction of Dibromonorcarane Derivative 3 with BuLi/Me3SnCl
2
)
The terms endo/exo in names and key numbers mean that the senior of the geminal substitutents is
on the concave/convex side of the molecule, cf. Schemes 2 – 4 and 7.

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However, the use of Mg as the metalating agent in the reaction of dibromonorcar-3-
ene derivative 3 with Me3SnCl produced a complex mixture consisting of exo-stannyl
isomer exo-4 as the major product along with products similar to those obtained by
treatment of 7,7-dibromonorcarane with an organomagnesium reagent (Scheme 3)
[13]. The endo-product endo-4 was formed in 22% yield, the reduction products endo-
and exo-5 in 3 and 2% yield, respectively, and the coupling product, syn- and anti-1 in 1
and 3% yield. Compound exo-4 was isolated as a mixture with exo-6; all attempts
(chromatography, crystallization) to separate this mixture failed. However, the
protodestannylation reaction of all stannylated products, i.e., of endo-4, exo-4, and
exo-6, with CF3COOH resulted in the formation of the corresponding reduced
products exo-5 [14], endo-5 [14], and endo-7 [15] which allowed us to characterize the
isolated products (Scheme 4). The attribution of the configuration of the monohalo-
substituted structures was also confirmed by the coupling constants between the H-
atoms of the cyclopropane moieties (Jcis was typically 8 Hz, while Jtrans was typically
4 Hz) [16].
Scheme 3. Reaction of Dibromonorcarane Derivative 3 with Mg/Me3SnCl
Copper(I) thiophene-2-carboxylate (CuTC) is a reagent successfully employed
either for couplings between unsaturated halides and stannanes [17], or between two
unsaturated halides [18] or stannanes [19]. Furthermore, it is one of the most efficient
reagents for the preparation of benzocyclotrimers from vicinally-bromo(stannyl)-
substituted olefins [4][20]. Treatment of endo-4 with a slight excess of CuTC in dry N-
methylpyrrolidin-2-one (NMP) at ꢀ 208 afforded the syn-coupling product syn-1 as the
sole isomer in 67% yield (Scheme 5). Careful analysis of the crude reaction mixture
(1H-NMR, GC/MS) did not reveal the formation of any trace of other products such as
a trimer, which may be formed by further addition of the carbene to syn-1.

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Scheme 4. Protodestannylation of the Halo(trimethylstannyl) Compounds exo-4, endo-4, and exo-6 to
Confirm the Exact Configurations
Scheme 5. Reaction of endo-4 with Copper(I) Thiophene-2-carboxylate (CuTC) in N-Methylpyrrolidin-
2-one (NMP)
The configuration of syn-1 was established by X-ray crystallography that revealed
also peculiar and interesting structural features. The compound crystallized in a
monoclinic centrosymmetric space group P21/n with four molecules in the unit cell. The
structure contains two 1a,2,7,7a-tetrahydro-1H-cyclopropa[b]naphthalene fragments
connected by a C¼C (C(11)ꢀC(12) ¼ 1.302 ꢄ) bond. The tetrahydronaphthalene
moieties are folded onto each other, as shown in the structure reported in Fig. 2. The
interplanar and centroid-to-centroid distances between the cofacial pair of benzene
moieties are 4.157(3) ꢄ and 4.247(3) ꢄ, respectively, and the dihedral angle between
the planes is 17.7(2)8. The cyclohexene fragments are also partially folded along the
C(15) ··· C(18) and C(7) ··· C(10) axis. The hinge angles between the cyclopropane
C(15)ꢀC(14)ꢀC(13)ꢀC(18) and C(7)ꢀC(8)ꢀC(9)ꢀC(10) planes are 112.0(2)8 and
112.3(1)8, respectively. The molecular packing of syn-1 as viewed along the a-axis is
shown in Fig. 2. Translation symmetry in the crystal structure may be easily seen in the
unit cell along the diagonal axis.
Surprisingly, treatment of the mixture exo-4/exo-6 (ratio 4.2 :1) with CuTC under
the same reaction conditions afforded also formation of syn-1 as a major product (64%)
beside the isomeric anti-1 (2%) (Scheme 6).
After having observed a strong selectivity in the coupling reaction of both
substrates exo- and endo-4, we propose the following mechanism for the formation of
the products. Copperꢀtin transmetalation is the most likely step to start the coupling
process, as previously observed in the case of vicinally-bromo(stannyl)-substituted
olefins [19]. In principle, the geminally subtituted-bromocuprates exo- and endo-8 can
eliminate CuBr to afford a carbene, which may undergo the dimerization reaction.

Helvetica Chimica Acta – Vol. 96 (2013)
945
Fig. 2. Molecular structure of syn-1 and molecular packing in syn-1 crystals viewed along the a-axis.
Thermal ellipsoids are drawn at the 40% probability level. Arbitrary atom numbering.
However, in this case, a diastereoselectivity would not be expected. The fact that syn-1
(which is the more sterically congested isomer) is formed in the coupling reaction of
endo-4 as the sole product indicates that a stepwise process is involved. We assume that
a hetero-coupling between two molecules of endo-8 takes place to form endo-9 with a
defined configuration by eliminating only one molecule of CuBr. Removal of a second
molecule of CuBr then gives syn-1 with the expected configuration (Scheme 7).
In conclusion, the results show that endo-4 and exo-4/exo-6 undergo stereoselective
reactions in which the Cu/Sn exchange is the preferred process. anti-Periplanar

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Helvetica Chimica Acta – Vol. 96 (2013)
Scheme 6. Reaction of exo-4/exo-6 with Copper(I) Thiophene-2-carboxylate (CuTC) in N-methylpyrro-
lidin-2-one (NMP)
Scheme 7. Formation Mechanism of the Major Product syn-1
elimination of CuBr or CuCl furnishes the corresponding coupling product syn-1 nearly
as single diastereoisomer, where the configuration of the stannylated halo compounds
determine the configuration of the coupling products. The present study represents a
viable synthesis of the contrasteric bicyclopropylidene syn-1 and confirms the ability of
CuTC to promote SnꢀSn (preferentially) coupling process.
The authors are indebted to the Scientific and Technical Research Council of Turkey (TUBITAK
project No. TBAG-106T082) for financial supports. This work has also been supported by Atatꢁrk

Helvetica Chimica Acta – Vol. 96 (2013)
947
University and TUBA (Turkish Academy of Sciences), and was co-funded by MIUR (Rome) within the
national PRIN framework.
Experimental Part
General. All reactions were carried out under Ar and monitored by TLC and/or 1H-NMR. All
solvents were dried and distilled before use. Flash column chromatography (FC): silica gel (SiO2,
60 mesh; Merck). TLC: Merck 0.2 mm silica gel 60 F254 on anal. aluminium plates. M.p.: uncorrected. 1H-
and 13C-NMR Spectra 3): Varian-400 or Bruker-400 spectrometer; d in ppm rel. to Me4Si as internal
standard, J in Hz. All new compounds gave satisfactory elemental analyses.
endo-(1-Bromo-1a,2,7,7a-tetrahydro-1H-cyclopropa[b]naphthalen-1-yl)trimethylstannane (endo-4).
To a soln. of dibromide 3 [7] (1.0 g, 3.31 mmol) in dry THF (10 ml) at ꢀ 788, 2.5m BuLi in hexanes
(1.32 ml, 3.31 mmol) was added dropwise, and the resulting mixture was stirred for 1 h at ꢀ788.
Chlorotrimethylstannane (660 mg, 3.31 mmol) was added portionwise within 60 min. The mixture was
stirred for 2 h at ꢀ 788. Then, the temp. was allowed to rise to r.t. overnight. The reaction was quenched
with H2O (50 ml), the mixture extracted with Et2O (3 ꢁ 30 ml), the combined extract dried (MgSO4) and
concentrated, and the residue purified by FC (hexane): endo-4 (1.15 g, 90%). Colorless oil. IR (KBr):
3062, 3020, 2906, 2883, 1496, 1454, 1430, 1187, 1056, 1040, 773, 745. 1H-NMR (400 MHz, CDCl3): 7.16 –
7.01 (AA’BB’, 4 arom. H); 3.18 (br. d, A of AB, J(2syn,2anti) ¼ J(7syn,7anti) ¼ 17.3, 1 HꢀC(2),
1 HꢀC(7)); 3.03 (br. d, B of AB, J(2syn,2anti) ¼ J(7syn,7anti) ¼ 17.3, 1 HꢀC(2), 1 HꢀC(7)); 2.05 (br. d,
J(1a,2anti) ¼ J(7a,7anti) ¼ 3.5, HꢀC(1a), HꢀC(7a)); ꢀ 0.04 (s, Me3Sn). 13C-NMR (100 MHz, CDCl3):
134.4; 130.6; 127.3; 32.4; 29.4; 28.3; ꢀ 5.3.
Mixture of exo- and endo-4/exo- and endo-5/exo-6/syn- and anti-1. Mg (1.09 g, 44.90 mmol) was
added to a soln. of dibromide 3 (11.3 g, 37.42 mmol) in dry THF (100 ml) at r.t. in an ultrasonic bath.
Chlorotrimethylstannane (7.53 g, 37.79 mmol) was added portionwise. The mixture was stirred for 1 h at
r.t. The reaction was quenched with sat. NH4Cl soln. (95 ml) and the mixture extracted with Et2O (3 ꢁ
80 ml). The combined extract was dried (MgSO4) and concentrated and the crude residue subjected to
column chromatography (neutral Al2O3 (450 g) hexane): endo-4 (3.2 g, 22%; see above, exo-5 (167 mg,
2%), exo-4/exo-6 4.2 :1 (7.35 g; by 1HNMR: exo-4 (6.07 g, 42%) and exo-6 (1.28 g, 10%), endo-5 (250 mg,
3%), syn-1 (53 mg, 1%; see below), and anti-1 (160 mg, 3%), in this order.
exo-1-Bromo-1a,2,7,7a-tetrahydro-1H-cyclopropa[b]naphthalene (exo-5): Colorless liquid. IR
1
(KBr): 3021, 2888, 2833, 1455, 1323, 1282, 1217, 1024, 749, 675. H-NMR (400 MHz, CDCl3): 7.14 (AA’
of AA’BB’, 2 arom. H); 7.02 (BB’ of AA’BB’, 2 arom. H); 3.15 (br. d, A of AB, J(2syn,2anti) ¼
J(7syn,7anti) ¼ 15.8, 1 HꢀC(2), 1 HꢀC(7)); 3.06 (br. d, B of AB, J(2syn,2anti) ¼ J(7syn,7anti) ¼ 15.8,
1 HꢀC(2), 1 HꢀC(7)); 2.63 (t, J(1,1a) ¼ J(1,7a) ¼ 3.0, HꢀC(1)); 1.77 (m, HꢀC(1a), HꢀC(7a)). 13C-NMR
(100 MHz, CDCl3): 134.0; 129.3; 126.8; 28.6; 22.0; 19.3. Anal. calc. for C11H11Br (223.11): C 59.22, H 4.97;
found: C 59.77, H 4.96.
exo-(1-Bromo-1a,2,7,7a-tetrahydro-1H-cyclopropa[b]naphthalen-1-yl)trimethylstannane (exo-4):
From the mixture exo-4/exo-6 4.2 :1: 1H-NMR (400 MHz, CDCl3): 7.14 – 7.08 (AA’BB’, 4 arom. H);
3.21 (ddd, A of AB, J(2syn,2anti) ¼ J(7syn,7anti) ¼ 16.5, J(syn,1a) ¼ J(7syn,7a) ¼ 5.5, J(2syn,7a) ¼
J(7syn,1a) ¼ 2.6, 1 HꢀC(2), 1 HꢀC(7)); 2.70 (br. d, B of AB, J(2syn, 2anti) ¼ J(7syn,7anti) ¼ 16.5,
1 HꢀC(2), 1 HꢀC(7)); 1.38 (m, HꢀC(1a), HꢀC(7a)); 0.19 (s, Me3Sn). 13C-NMR (100 MHz, CDCl3):
136.4; 128.2; 125.6; 27.6; 24.9; 18.1; ꢀ 9.7.
exo-(1-Chloro-1a,2,7,7a-tetrahydro-1H-cyclopropa[b]naphthalen-1-yl)trimethylstannane (exo-6):
1
From the mixture exo-4/exo-6 4.2 :1 (only non-overlapped signals): H-NMR (400 MHz, CDCl3): 3.12
(ddd, A of AB, J(2syn, 2anti) ¼ J(7syn,7anti) ¼ 16.5, J(2syn,1a) ¼ J(7syn,7a) ¼ 5.5, J(2syn,7a) ¼
J(7syn,1a) ¼ 2.7, 1 HꢀC(2); 1 HꢀC(7)); 2.68 (br. d, B of AB, J(2syn,2anti) ¼ J(7syn,7anti) ¼ 16.5,
1 HꢀC(2), 1 HꢀC(7)). 13C-NMR (100 MHz, CDCl3): 125.5; 37.2; 18.6; ꢀ 10.1.
endo-1-Bromo-1a,2,7,7a-tetrahydro-1H-cyclopropa[b]naphthalene (endo-5): Colorless oil. IR
(KBr): 3061, 3019, 2939, 2894, 2840, 1495, 1455, 1429, 1257, 743, 646. 1H-NMR (400 MHz, CDCl3):
3
)
The lable syn or anti refers to the position of a H-atom on the concave or convex side of a molecule.

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Helvetica Chimica Acta – Vol. 96 (2013)
7.16 – 7.11 (AA’BB’, 4 arom. H); 3.53 (t, J(1,1a) ¼ J(1,7a) ¼ 7.5, HꢀC(1); 3.21 (ddd, A of AB,
J(2syn,2anti) ¼ J(7syn,7anti) ¼ 16.5, J(2syn,1a) ¼ J(7syn,7a) ¼ 5.3, J(2syn,7a) ¼ J(7syn,1a) ¼ 2.8,
1 HꢀC(2), 1 HꢀC(7)); 2.68 (br. d, B of AB, J(2syn,2anti) ¼ J(7syn,7anti) ¼ 16.5, 1 HꢀC(2), 1 HꢀC(7));
1.55 (m, HꢀC(1a), HꢀC(7a)). 13C-NMR (100 MHz, CDCl3): 136.0; 128.5; 126.0; 33.6; 26.3; 14.5. Anal.
calc. for C11H11Br: C 59.22, H 4.97; found: C 59.56, H 4.80.
anti-1a,1’a,2,2’,7,7’,7a,7’a-Octahydro-1,1’-bi[1H-cyclopropa[b]naphthalenylidene] (¼anti-1a,2,7,7a-
Tetrahydro-1-(1a,2,7,7a-tetrahydro-1H-cyclopenta[b]naphtalen-1-ylidene)-1H-cyclopropa[b]naphtha-
lene; anti-1)1): Colorless crystals from CH2Cl2/hexane 1:3. M.p. 239 – 2408 ([5]: M.p. 228 – 2328). IR
(KBr): 2964, 2924, 2844, 1260, 1094, 1021, 864, 799, 748. 1H-NMR (400 MHz, CDCl3): 7.06 – 6.95
(AA’BB’, 8 arom. H); 2.99 (m, 2 HꢀC(2), 2 HꢀC(2’), 2 HꢀC(7), 2 HꢀC(7’)); 1.63 (m, HꢀC(1a),
HꢀC(7a), HꢀC(1’a), HꢀC(7’a)). 13C-NMR (100 MHz, CDCl3): 135.8; 128.7; 125.8; 118.0; 29.6; 14.4.
Anal. calc. for C22H20: C 92.91, H 7.09; found: C 92.89, H, 6.27.
syn-1a,1’a,2,2’,7,7’,7a,7’a-Octahydro-1,1’-bi[1H-cyclopropa[b]naphthalenylidene] (¼syn-1a,2,7,7a-
Tetrahydro-1-(1a,2,7,7a-tetrahydro-1H-cyclopropa[b]naphthalen-1-ylidene)-1H-cyclopropa[b]naphtha-
lene; syn-1)1). To copper(I) thiophene-2-carboxylate (CuTC; 1.73 g, 9.07 mmol) in a flask purged with Ar
and capped with a septum, dry NMP (25 ml) and bromo(stannyl) derivative endo-4 (1.0 g, 2.59 mmol)
were added consecutively via syringe at ꢀ 208. The mixture was stirred for 1 h at ꢀ 208 and for 3 h at r.t.
(TLC monitoring). After completion of the reaction, 10% aq. NH3 soln. (20 ml) was added, and the
slurry was stirred until the brown solid disappeared. The mixture was extracted with Et2O (3 ꢁ 20 ml),
the combined org. extract dried (MgSO4) and concentrated, and the residue purified by FC (hexane):
syn-1 (248 mg, 67%). Colorless crystals from CH2Cl2/hexane 1:3. M.p. 155 – 1568 ([5]: M.p. 144 – 1578).
IR (KBr) 3058, 3019, 2991, 2966, 2911, 2889, 2829, 1493, 1454, 1435, 1300, 1113, 1041, 1004, 753, 739.
1H-NMR (400 MHz, CDCl3): 6.82 – 6.73 (AA’BB’, 8 arom. H), 2.97 (br. d, A of AB, J(2syn,2anti) ¼
J(7syn,7anti) ¼ J(2’syn,2’anti) ¼ J(7’syn,7’anti) ¼ 15.0, 1 HꢀC(2), 1 HꢀC(2’), 1 HꢀC(7), 1 HꢀC(7’)); 2.50
(br. d, B of AB, J(2syn,2anti) ¼ J(7syn,7anti) ¼ J(2’syn,2’anti) ¼ J(7’syn,7’anti) ¼ 15.0, 1 HꢀC(2),
1 HꢀC(2’), 1 HꢀC(7), 1 HꢀC(7’)); 1.90 (m, HꢀC(1a), HꢀC(7a), HꢀC(1’a), HꢀC(7’a)). 13C-NMR
(100 MHz, CDCl3) 135.5; 128.3; 126.0; 118.8; 29.5; 14.7. EI-MS (70 eV): 285 (Mþ, 5), 267 (7), 240 (9),
180 (37), 153 (29), 142 (65), 129 (82), 116 (100), 105 (21), 91 (43), 66 (10).
X-Ray Crystal-Structure Determination of syn-14). For the crystal structure determination, the single
crystal of syn-1 was used for data collection on a four-circle Rigaku-R-AXIS-RAPID-S diffractometer
equipped with a two-dimensional area IP detector. The graphite-monochromatized MoKa radiation (l ¼
0.71073 ꢄ) and oscillation-scans technique with Dw ¼ 58 for one image were used for data collection.
Images for syn-1 were taken successfully by varying w with three sets of different c and f values. The 108
images for six different runs covering ca. 99.7% of the Ewald spheres were performed. The lattice
parameters were determined by the least-squares methods on the basis of all reflections with F2 > 2s(F2).
Integration of the intensities, correction for Lorentz and polarization effects, and cell refinement was
performed with CrystalClear (Rigaku/MSC Inc., 2005) software [21]. The structure was solved by direct
methods SHELXS-97 [22], and non-H-atoms were refined by the full-matrix least-squares method with
anisotropic temperature factors SHELXL-97 [22]. Crystal data: C22H20; crystal system monoclinic; space
group P21/n (no.14); unit cell dimensions: a ¼ 8.8709(2), b ¼ 8.5274(2), c ¼ 21.1090(3) ꢄ, b ¼ 95.92(2)8;
volume 1588.3(1) ꢄ3; Z ¼ 4; Dx ¼ 1.19 Mg/m3; absorption coefficient 0.067 mmꢀ1; F(000) 608; q range for
data collection 2.4 – 30.78; refinement method: full-matrix least-square on F2; data and parameters, 4877
and 212; goodness-of-fit on F2 1.025; final R indices (I > 2s(I)): R1 ¼ 0.070, wR2 ¼ 0.183; R indices (all
data): R1 ¼ 0.130, wR2 ¼ 0.218; largest diff. peak and hole 0.160 and ꢀ 0.182 e ꢄꢀ3
.
Reaction of exo-4/exo-6 4.2 :1 with CuTC. As described for syn-1, with CuTC (1.74 g, 9.10 mmol),
NMP (25 ml), and halo(stannyl) derivatives exo-4/exo-6 4.2 :1 (790 mg of exo-4 þ 188 mg of exo-6, total
2.60 mmol). FC (hexane) yielded syn-1 (236 mg, 64%) and anti-1 (7 mg, 2%) in this order.
4
)
CCDC-643590 contains the supplementary crystallographic data for this article. These data can be
obtained free of charge via http://www.ccdc.cam.ac.uk/data_request/cif.

Helvetica Chimica Acta – Vol. 96 (2013)
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REFERENCES
[1] S. Kozhushkov, T. Spꢅth, T. Fiebig, B. Galland, M.-F. Ruasse, P. Xavier, Y. Apeloig, A. de Meijere, J.
Org. Chem. 2002, 67, 4100; H. Nꢁske, S. Brꢅse, S. I. Kozhushkov, M. Noltemeyer, M. Es-Sayed, A.
de Meijere, Chem. ꢀ Eur. J. 2002, 8, 2350; A. de Meijere, M. von Seebach, S. Zçllner, S. I.
Kozhushkov, V. N. Belov, R. Boese, T. Haumann, J. Benet-Buchholz, D. S. Yufit, J. A. K. Howard,
Chem. ꢀ Eur. J. 2001, 7, 4021; A. de Meijere, S. I. Kozhushkov, Eur. J. Org. Chem. 2000, 3809.
[2] A. de Meijere, V. Bagutski, F. Zeuner, U. K. Fischer, V. Rheinberger, N. Moszner, Eur. J. Org. Chem.
2004, 3669; H. Maeda, T. Hirai, A. Sugimoto, K. Mizuno, J. Org. Chem. 2003, 68, 7700; S. Tero-
Kubota, T. Miyashi, J. Am. Chem. Soc. 2003, 125, 9147; A. de Meijere, S. I. Kozhushkov, D. Faber, V.
Bagutskii, R. Boese, T. Haumann, R. Walsh, Eur. J. Org. Chem. 2001, 3607; A. de Meijere, S. I.
Kozhushkov, T. Spꢅth, N. S. Zefrov, J. Org. Chem. 1993, 58, 502; K. Jochims, Tetrahedron Lett. 1974,
4215; D. Kohler, J. Am. Chem. Soc. 1930, 52, 424.
[3] a) M. von Seebach, S. I. Kozhushkov, H. Schill, D. I. Frank, R. Boese, J. Benet-Buchholz, D. S. Yufit,
A. de Meijere, Chem. ꢀ Eur. J. 2007, 13, 167; b) J.-L. Mieusset, U. H. Brinker, J. Org. Chem. 2005, 70,
10572; c) X. Li, M. Neuenschwander, Helv. Chim. Acta 2000, 83, 562; d) R. Huwyer, A. Al-
Dulayymi, M. Neuenschwander, Helv. Chim. Acta 1999, 82, 2336; e) M. Borer, M. Neuenschwander,
Helv. Chim. Acta 1997, 80, 2486; f) C. Laeng, M. Muehlebach, M. Neuenschwander, Helv. Chim.
Acta 1997, 80, 2124; g) V. V. Tverezovsky, M. S. Baird, I. G. Bolesov, Tetrahedron 1997, 53, 14773;
h) M. Borer, T. Loosli, A. Minger, M. Neuenschwander, P. Engel, Helv. Chim. Acta 1995, 78, 1311;
i) T. Loosli, M. Borer, I. Kulakowska, A. Minger, M. Neuenschwander, P. Engel, Helv. Chim. Acta
1995, 78, 1144; j) L. Skatteboel, Y. Stenstroem, M.-B. Stjerna, Acta Chem. Scand., Ser. B 1988, 42,
475; k) R. Brun, D. S. B. Grace, K. H. Holm, L. Skatteboel, Acta Chem. Scand., Ser. B 1986, 40, 21;
l) J. Arct, L. Skattebol, Acta Chem. Scand., Ser. B 1982, 36, 593.
[4] G. Borsato, O. De Lucchi, F. Fabris, L. Groppo, V. Lucchini, A. Zambon, J. Org. Chem. 2002, 67,
7894.
[5] M. G. Banwell, R. W. Gable, R. J. Greenwood, J. N. Lambert, M. F. Mackay, J. M. Walter, Synlett
1997, 953.
[6] A. Menzek, A. Altundas, D. Gultekin, J. Chem. Res. Synop. 2003, 11, 752.
[7] L. A. Paquette, E. Chamot, A. R. Browne, J. Am. Chem. Soc. 1980, 102, 637; M. Robert, J. R.
Snoonian, M. S. Platz, G. Wu, H. Hong, J. Phys. Chem. A 1998, 102, 587.
[8] H. Siegel, Top. Curr. Chem. 1982, 106, 55.
[9] a) M. G. Banwell, D. C. R. Hockless, R. W. Longmore, J. M. Walter, Aust. J. Chem. 1997, 50, 457;
b) A. P. Molchanov, S. A. Kalyamin, R. R. Kostikov, J. Org. Chem. USSR Engl. 1992, 28, 102; c) B.
Bogdanovic, K. Schlichte, U. Westeppe, Chem. Ber. 1988, 121, 27; d) T. Ando, T. Muranaka, T.
Ishihara, Bull. Chem. Soc. Jpn. 1981, 54, 3227; e) W. R. Moore, H. R. Ward, J. Org. Chem. 1960, 25,
2073.
[10] D. Seyferth, R. L. Lambert, J. Organomet. Chem. 1973, 55, C53; K. G. Taylor, W. E. Hobbs, M.
Saquet, J. Org. Chem. 1971, 36, 369.
[11] K. Kitatani, T. Hiyama, H. Nozaki, Bull. Chem. Soc. Jpn. 1977, 50, 3288; D. Seyferth, R. L. Lambert,
D. C. Annarelli, J. Organomet. Chem. 1976, 122, 311; D. Seyferth, R. L. Lambert, M. C. Massol, J.
Organomet. Chem. 1975, 88, 255.
[12] M. G. Banwell, J. M. Cameron, M. P. Collins, G. L. Gravatt, Aust. J. Chem. 1997, 50, 395.
[13] J. Touster, A. J. Fry, Tetrahedron Lett. 1997, 38, 6553; D. Seyferth, R. L. Lambert, M. C. Massol, J.
Organomet. Chem. 1975, 88, 287.
[14] R. M. Blankens, K. A. Burdett, J. S. Swenton, J. Org. Chem. 1974, 39, 2300.
[15] A. V. Vorogushin, M. D. Reshetova, N. G. Akhmedov, Y. A. Ustynyuk, I. L. Eremenko, S. E.
Nefedov, A. I. Zinin, Russ. Chem. Bull. 1998, 47, 699.
[16] M. Balci, ꢆBasic 1H- and 13C-NMR Spectroscopyꢂ, Elsevier, 2005.
[17] G. D. Allred, L. S. Liebeskind, S. A. Sanford, J. Am. Chem. Soc. 1996, 118, 2748; I. Paterson, J. Man,
Tetrahedron Lett. 1997, 38, 695; B. W. Dymock, P. J. Kocienski, J.-M. Pons, Synthesis 1998, 1655.
[18] S. Zhang, D. Zhang, L. S. Liebeskind, J. Org. Chem. 1997, 62, 2312; F. Babudri, A. Cardone, G. M.
Farinola, F. Naso, Tetrahedron 1998, 54, 14609.

950
Helvetica Chimica Acta – Vol. 96 (2013)
[19] F. Fabris, L. Zambrini, E. Rosso, O. De Lucchi, Eur. J. Org. Chem. 2004, 3313; A. Armstrong, P. A.
Barsanti, L. H. Jones, G. Ahmed, J. Org. Chem. 2000, 65, 7020.
[20] F. Fabris, L. Pellizzaro, C. Zonta, O. De Lucchi, Eur. J. Org. Chem. 2007, 283; V. Maslak, Z. Yan, S.
Xia, J. Gallucci, C. M. Hadad, J. D. Badjic, J. Am. Chem. Soc. 2006, 128, 5887; G. Borsato, S.
Brussolo, M. Crisma, O. De Lucchi, V. Lucchini, A. Zambon, Synlett 2005, 1125; C. Zonta, F. Fabris,
O. De Lucchi, Org. Lett. 2005, 7, 1003; F. Fabris, L. Bellotto, O. De Lucchi, Tetrahedron Lett. 2003,
44, 1211; G. Borsato, O. De Lucchi, F. Fabris, V. Lucchini, M. Pasqualotti, A. Zambon, Tetrahedron
Lett. 2003, 44, 561; H. Sakurai, T. Daiko, T. Hirao, Science (Washington, DC, U.S.) 2003, 301, 1878;
O. De Lucchi, A. Das¸tan, A. Altundas¸, F. Fabris, M. Balcı, Helv. Chim. Acta 2004, 87, 2364; A.
Dastan, E. Uzundumlu, M. Balci, F. Fabris, O. De Lucchi, Eur. J. Org. Chem. 2004, 183; A. Dastan, F.
Fabris, O. De Lucchi, M. Gꢁney, M. Balci, Helv. Chim. Acta 2003, 86, 3411; E. DalkiliÅ, M. Gꢁney, A.
Dastan, N. Saracoglu, O. De Lucchi, F. Fabris, Tetrahedron Lett. 2009, 50, 1989.
[21] CrystalClear Rigaku/MSC, Inc., 9009 New Trails Drive, The Woodlands, TX 77381, USA, 2005.
[22] G. M. Sheldrick, SHELXS97 and SHELXL97, University of Gçttingen, Germany, 1997.
Received June 6, 2012