An alternative general preparation of 2-alkyl-1-benzostannepines and their conversion into 1-benzostibepines and 1-benzoborepines via a tin-metal exchange

Article abstract of DOI:10.1039/b000900h

The 2-alkyl-1-benzostannepines 4a-g were prepared by the intramolecular hydrostannation of the tin intermediates 3 to an acetylenic moiety in one pot from (Z)-1-(o-bromophenyl)but-1-en-3-ynes 1. The obtained stannepines 4 were easily converted into the 1-benzostibepines 9, 10, 11, 12 and the 1-benzoborepines 14, 15 by tin-antimony and t/n-boron exchange reactions in moderate to good yields, respectively. The 1-benzoborepines 14 and 15 are hitherto unknown heterocyclic ring systems.

Full text of DOI:10.1039/b000900h

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An alternative general preparation of 2-alkyl-1-benzostannepines
and their conversion into 1-benzostibepines and 1-benzoborepines
via a tin–metal exchange†
1
Haruki Sashida* and Atsuhiro Kuroda
Faculty of Pharmaceutical Sciences, Hokuriku University, Kanagawa-machi,
Kanazawa 920-1181, Japan. E-mail: h-sashida@hokuriku-u.ac.jp
Received (in Cambridge, UK) 1st February 2000, Accepted 7th April 2000
Published on the Web 23rd May 2000
The 2-alkyl-1-benzostannepines 4a–g were prepared by the intramolecular hydrostannation of the tin intermediates
3 to an acetylenic moiety in one pot from (Z)-1-(o-bromophenyl)but-1-en-3-ynes 1. The obtained stannepines 4
were easily converted into the 1-benzostibepines 9, 10, 11, 12 and the 1-benzoborepines 14, 15 by tin–antimony
and tin–boron exchange reactions in moderate to good yields, respectively. The 1-benzoborepines 14 and 15 are
hitherto unknown heterocyclic ring systems.
Introduction
There has been considerable interest in the chemistry of hetero-
cycles containing a tin atom. The chemistry of the stannole ring
system,1,2 stannacyclopentadiene, has been reviewed and a large
number of compounds has been prepared. Although the chem-
istry of the six-membered tin-containing heterocycles3 has also
been widely studied, the corresponding seven-membered hetero-
cycles (stannepines) have only occasionally been studied. The
C-unsubstituted 3-benzostannepine IIA,4 the fully unsaturated
heterocycle containing a tin atom at the C-3 position, was pre-
pared by the intermolecular hydrostannation of o-diethynyl-
benzene I more than 35 years ago. The thiophene ring- IIB5a
and IIC,5b the pyrrole ring- IID6 and the cyclopentane
ring-fused stannepines IIE7 have also been synthesized by the
extension of this annellation reaction. Furthermore, mono-
cyclic stannepines IV have been obtained by not only the
above hydrostannation8 but also by ring enlargement9 of the
carbene intermediate from the 1,4-dihydrostannabenzene III
(Scheme 1).
On the one hand, it is well known that these parent stan-
nepines can be transformed into the corresponding derivatives
of borepines4b,5–7,8b,10 and stibepines11 by the tin–metal
exchange reaction. Stannepines are thus useful as the key
starting materials for the preparation of other heteroepines.
However, only two reports of the synthesis of the 1-benzo-
stannepines V,12,13 theoretically possible structural isomers,
have been known in very recent years. The C-unsubstituted
1-benzostannepine12 and the 2-trimethylsilyl derivative12 have
been prepared by the coupling of dimethyltin dichloride and
the 1,6-dilithium compound, generated from (Z,Z)-1-bromo-
4-(2-bromophenyl)-1-trimethylsilylbuta-1,3-diene. 2-tert-Butyl-
and 2-n-butyl-1-benzostannepines13,14 have also been obtained
by the reaction of the corresponding 1-benzotellurepines15 with
tert-butyllithium, followed by treatment with di-n-butyltin
dichloride. However, these routes are fairly limited and not
general; in particular, the former method provides no variety
of 2-alkyl substituted 1-benzostannepines.
Previously, we reported the synthesis of the 1-benzotellur-
epines15 and the 1-benzoselenepines,15 which are novel seven-
Scheme 1
† The yields obtained for compounds 4, 5 and 6, together with 1H and
membered heterocycles containing a tellurium or selenium
element, via the successive intramolecular addition of telluroles
or selenoles to a triple bond. Moreover, for several years we
13C NMR measurements for the 1-benzostannepines 4, are available as
supplementary data. For direct electronic access see http://www.rsc.org/
suppdata/p1/b0/b000900h/
DOI: 10.1039/b000900h
J. Chem. Soc., Perkin Trans. 1, 2000, 1965–1969
This journal is © The Royal Society of Chemistry 2000
1965

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Scheme 2
have focused on the synthesis of various heterocyclic ring
benzostannepine 4g are new compounds, although 2-tert-butyl
systems16 using efficient intramolecular cyclization reactions
involving an acetylenic group. In this paper, we describe the
novel route for preparation of the stable 2-alkyl-1-benzo-
stannepines by a similar cyclization and the transformation of
stannepines into 1-benzoborepines and 1-benzostibepines via
the replacement of tin with antimony or boron.14
4a and 2-n-butyl derivative 4b have been prepared in our recent
work.13 These results are summarized in the electronic sup-
plementary data (Table 1). The structural assignment of the
products 4, 5 and 6 could be made from the 1H and 13C NMR
and HRMS spectra (electronic supplementary data, Table 2,
and Experimental section). No six-membered 6-exo-dig
products 8 were formed by this ring closure reaction, although
in the case of intramolecular hydrotelluration and hydroselen-
ation at a carbon–carbon triple bond, as described in our previ-
ous paper,15 both the 7-endo-dig and the 6-exo-dig reactions
took place. Furthermore, a similar hydrosilylation gave only the
6-exo-dig products.16i The reason for the differences caused by
changing the element is not clear at present.
Results and discussion
Synthesis of 1-benzostannepines
The synthesis of the 2-alkyl-1,1-dibutyl-1-benzostannepines 4 is
shown in Scheme 2. (Z)-1-(o-Bromophenyl)but-1-en-3-ynes 1,
which were obtained in our previous study,15b were lithiated
with 2.2 equiv. of ButLi in the presence of N,N,NЈ,NЈ-tetra-
methylethylenediamine (TMEDA) in anhydrous hexane at
Ϫ80 ЊC, and then treated with 1.1 equiv. of di-n-butylchlorotin
Conversion of stannepines into stibepines
C-unsubstituted 1-benzostibepine12 and the 2-tert-butyl and
2-n-butyl derivatives13 have been previously obtained. The
tin–antimony exchange reactions of 3-benzostannepine11 and
the six-membered tin-containing heterocyclic compounds3a,3h,23
have been extensively studied. These reactions prompted us to
examine a similar replacement reaction using the 1-benzo-
stannepines obtained in this work for the purpose of producing
the 1-benzostibepines. The stannepines 4a,b readily reacted
with 1.0 equiv. of antimony trichloride (SbCl3) in CHCl3 at 0 ЊC
to almost quantitatively afford the corresponding 1-chloro-1-
benzostibepines 9a,b, but these compounds were too unstable
to be isolated. Thus, we planned the transformation of 9 into
the Sb-phenyl or -alkyl substituted derivatives. Treatment of the
1-chlorostibepines 9 (freshly prepared without purification after
hydride (Bun ClSnH),17 which was freshly generated from an
2
equal amount of di-n-butyltin dichloride (Bun SnCl2) and di-n-
2
butyltin dihydride (Bun SnH2), giving the desired 2-alkyl-1-
2
benzostannepines 4a–g as stable colorless oils, together with the
debrominated (Z)-1-(phenyl)but-1-en-3-ynes 5 and the bis[(Z)-
o-(but-1-en-3-ynyl)phenyl]dibutylstannanes 6. These materials
could be separated by silica gel column chromatography. The
enyne compounds 5 were probably produced by the hydrolysis
of the lithio derivatives 2. The formation of the diarylstannanes
6 could be easily explained by the process involving a 1:2
coupling of Bun Cl2Sn and 2. Treatment of the trimethylsilyl
2
derivative 1h with ButLi in a similar manner gave a complex
mixture without any detectable compounds, and lithiation of
the phenyl derivative 1i resulted in 5-exo-dig cyclization to
afford 1-benzylideneindene 7 in low yield without producing
any tin-containing compounds. A similar cyclization of the
lithio compound having a phenylacetylene moiety18 that pro-
duced a five-membered compound has already been reported.
It is well known that the intermolecular addition of organo-
tin hydride compounds to a carbon–carbon triple bond induced
by radical initiators (e.g., AIBN, Et3B),19 transition metal
catalysts (e.g., Pd(PPh3)4),20 base catalysts4 or Lewis acid
catalysts (e.g., ZrCl4, HfCl4)21 gives the hydrostannylation
products, and this addition frequently proceeds in the absence
of a catalyst.22 Therefore, the stannepines 4 may probably be
obtained by the intramolecular 7-endo-dig ring closure of the
tin hydride intermediates 3 at the sp carbon of the triple bond,
as shown in Scheme 2. Compounds 4 are quite stable and are
not sensitive to air, light or even moisture. 2-Methyl- 4c, 2-n-
propyl- 4d, 2-n-hexyl- 4e, 2-n-octyl- 4f and 2-cyclohexyl-1-
removal of the solvent and the generated Bun SnCl2 under
2
reduced pressure) with a small excess of phenyllithium in ether
at Ϫ20 ЊC afforded the 1-phenyl-1-stibepines 10 in moderate
yields (Scheme 3). The methyl 11 and 1-n-butyl derivatives 12
were also obtained in a similar manner by using methyllithium
and n-butyllithium instead of phenyllithium, respectively.
Compounds 10, 11 and 12 were more stable than the 1-chloro-
stibepines 9 and could easily be purified by normal silica gel
chromatography.
After the reaction of the stannepine 4a with dichlorophenyl-
stibine (Cl2SbPh) in CHCl3, 4a was recovered together with a
small amount of the diene compound 13.15b Although the
Sb-phenyl substituted stibepines are described in the literature,
the Sb-alkyl derivatives could not be obtained due to the
thermal instability of the reagents (dihaloalkylstibines). Thus,
compounds 11 and 12 are the first isolated examples of 1-alkyl-
1-benzostibepines.
1966
J. Chem. Soc., Perkin Trans. 1, 2000, 1965–1969

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Conclusions
In the present work, the general synthesis of 2-alkyl-1-benzo-
stannepines by an intramolecular hydrostannation reaction
with a triple bond was achieved. The parent stannepines were
transformed into the corresponding 1-benzostibepines and
1-benzoborepines by a tin–metal exchange. Further reactions
and applications of the stannepines including other tin–metal
exchanges are now under investigation.
Experimental
Melting points were measured on a Yanagimoto micro melting
point hot stage apparatus and are uncorrected. IR spectra were
recorded on a Hitachi 270–30 spectrometer. Mass spectra (MS)
and HR-MS were recorded on a JEOL JMS-DX300 instru-
1
ment. H NMR spectra were recorded on a JEOL PMX-60SI
(60 MHz), JEOL EX-90A (90 MHz) or JEOL JNM-GSX 400
(400 MHz) spectrometer in CDCl3 using tetramethylsilane as
internal standard and J values are given in Hz. 13C NMR
spectra were recorded on a JEOL JNM-GSX 400 (400 MHz)
spectrometer.
Scheme 3 Reagents and conditions: i, SbCl3 (1 equiv.), CHCl3, 0 ЊC, 30
min; ii, PhLi (1.2 equiv.), ether, Ϫ20 ЊC, 30 min (for 10); iii, MeLi (1.2
equiv.), ether, Ϫ20 ЊC, 30 min (for 11); iv, n-BuLi (1.2 equiv.), ether,
Ϫ20 ЊC, 30 min (for 12); v, PhSbCl2, CHCl3, 0 ЊC; vi, BCl3 (1 equiv.),
hexane, room temp., 1 h (for 14); vii, PhBCl2 (1 equiv.), hexane, room
temp., 1 h (for 15).
General procedure for the reaction of (Z)-1-(o-lithiophenyl)but-
1-en-3-ynes with Bun SnHCl: formation of 2-alkyl-1,1-dibutyl-1-
2
benzostannepines 4, (Z)-1-(phenyl)but-1-en-3-ynes 5 and bis[(Z)-
o-(but-1-en-3-ynyl)phenyl]dibutylstannane 6
To a stirred solution of (Z)-1-(o-bromophenyl)but-1-en-3-yne 1
(5 mmol) and TMEDA (1.8 ml, 10 mmol) under an argon
atmosphere was slowly added ButLi (1.6 mol in pentane
solution, 7.5 ml, 12 mmol). After the reaction mixture had been
stirred at the same temperature for 30 min, di-n-butyl-
chlorotin hydride (5.5 mmol, freshly prepared from di-n-
butyltin dihydride and one equivalent of di-n-butyltin dichlor-
ide at room temperature in quantitative yield) was added. The
reaction mixture was allowed to warm to room temperature
during 3–4 h with stirring. Saturated aqueous NH4Cl (50 ml)
was added, and the layers were separated. The aqueous layer
was extracted with ether (50 ml × 2). The organic layers were
washed with brine (50 ml × 2), dried (MgSO4), and concen-
trated in vacuo. The resulting residue was chromatographed on
silica gel eluted with n-hexane to give 4, 5 and 6. The results are
summarized in Table 1 and the spectral data for the stannepines
Conversion of stannepines into borepines
We next examined the tin–boron exchange reaction24 in order
to form the novel 1-benzoborepines using the more stable and
easily available 2-tert-butyl-1-benzostannepine 4a. The reaction
of 1-stannepine 4a with 1.0 equiv. of boron trichloride (BCl3) in
n-hexane at room temperature resulted in the desired tin–boron
exchange to give 2-tert-butyl-1-chloro-1-benzoborepine 14a,
which could be purified by distillation under reduced pressure
in spite of its being air- and moisture-sensitive. The treatment
of 1-chloroborepine 14a with phenyllithium or alkyllithium
resulted in decomposition and afforded no products. However,
the air- and moisture-sensitive 1-phenyl derivative 15a was
obtained by the reaction of 4a with dichlorophenylborane
(PhBCl2) under similar conditions.
The monocyclic fully unsaturated borepines,8,25 3-benzo-
borepines4,10 and other ring-fused derivatives5–7,26 have now
been recognized and established as aromatic compounds by 1H
and 13C NMR spectroscopic studies, molecular orbital calcu-
lations and X-ray crystal analyses. It is well known4,8 that the
olefinic protons of these borepines appear at lower field because
of a diamagnetic ring current induced by cyclic conjugation
through the boron atom, and/or the decrease in electron dens-
ities on the olefinic protons due to the overlap between the
boron vacant p orbital and π systems.3e,27 The 1H NMR spectra
of the 1-benzoborepines 14 and 15 show signals arising from
the borepine ring protons (3-H, 4-H and 5-H) at lower field
than those of the 1-benzostannepines 4 and the 1-benzo-
stibepines 9, 10, 11 and 12 obtained in this work. In particular,
the proton signals of 4-H are shifted 0.34–0.64 ppm downfield,
and appeared 0.25–0.62 ppm more downfield in comparison
to those of the Sn-di-n-butyl substituted 1-benzostannepines 4.
In addition, the observed coupling constants, J3,4 (14a: 8.4 Hz,
15a: 7.0 Hz) are somewhat large, while the values of J4,5 of 11.0
and 11.7 Hz observed in 14a and 15a are smaller than those of
the normal seven-membered 1-benzoheteroepines containing a
4 are listed in Table 2 (see electronic supplementary inform-
᎐
ation). The absorption due to C᎐C of compounds 5 could not
᎐
be observed in the IR spectrum.
(Z)-5,5-Dimethyl-1-phenylhex-1-en-3-yne 5a. Colorless oil,
δH (90 MHz, CDCl3) 1.30 (9H, s, But), 5.68 (1H, d, J 11.8,
Ph-CH᎐CH-), 6.56 (1H, d, J 11.8, Ph-CH᎐CH-), 7.30–7.45 and
᎐
᎐
7.83–8.00 (3H, m and 2H, m, Ph-H) (HRMS m/z Calc. for
C14H16: 184.1253. Found 184.1258).
(Z)-1-Phenyloct-1-en-3-yne 5b. Colorless oil, δH (90 MHz,
CDCl3) 0.80–1.69 and 2.24–2.57 (7H, m and 2H, m, Bun), 5.70
(1H, dt, J 12.0, 2.4, Ph-CH᎐CH-), 6.58 (1H, d, J 12.0, Ph-
᎐
CH᎐CH-), 7.22–7.47 and 7.80–8.04 (3H, m and 2H, m, Ph-H)
᎐
(HRMS m/z Calc. for C14H16: 184.1253. Found: 184.1250).
(Z)-1-Phenylhept-1-en-3-yne 5d. Colorless oil, δH (90 MHz,
CDCl3) 1.05, 1.40–1.75 and 2.42 (3H, t, J 7.6, 2H, m and 2H,
tq, J 6.8, 2.4, Prn), 5.69 (1H, dt, J 11.9, 2.4, Ph-CH᎐CH-), 6.55
᎐
heavier element.12,13,15,28 In the 13C NMR of 15, three sp2
α
᎐
(1H, d, J 11.9, Ph-CH᎐CH-), 7.25–7.45 and 7.81–7.92 (3H, m
and 2H, m, Ph-H) (HRMS m/z Calc. for C13H14: 170.1096.
Found: 170.1098).
carbon atoms, appearing at δ 141.6 (s), 148.4 (s) and 159.3 (s),
are almost identically deshielded while the signals of the
other sp2 doublet γ carbons are in the normal region for
aromatic and olefinic carbon atoms. These observations
indicate that the 1-benzoborepines obtained in this work are
aromatic.
(Z)-1-Phenyldec-1-en-3-yne 5e. Colorless oil, δH (90 MHz,
CDCl3) 0.79–1.73 and 2.23–2.38 (11H, m and 2H, m, n-C6H13),
5.69 (1H, dt, J 12.0, 2.2, Ph-CH᎐CH-), 6.56 (1H, d, J 12.0, Ph-
᎐
J. Chem. Soc., Perkin Trans. 1, 2000, 1965–1969
1967

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CH᎐CH-), 7.20–7.50 and 7.79–7.98 (3H, m and 2H, m, Ph-H)
2-tert-Butyl-1-phenyl-1-benzostibepine 10a
᎐
(HRMS m/z Calc. for C16H20: 212.1566. Found: 212.1560).
A solution of 4a (71 mg, 0.17 mmol) in CHCl3 (2 ml) was added
in one portion with stirring to SbCl3 (39 mg, 0.17 mmol) in
CHCl3 (10 ml) under an argon atmosphere at 0 ЊC. The reaction
mixture was vigorously stirred at room temperature for 30 min.
After removal of the solvent at room temperature in vacuo,
followed by exclusion of BuSnCl2 at 100–110 ЊC/2 mmHg using
a semimicro distillation apparatus, the resulting residue was dis-
solved in hexane (10 ml). To this hexane solution of crude 9a at
Ϫ20 ЊC was added PhLi (1.14 mol lϪ1, 0.25 ml, 0.17 mmol). The
mixture was stirred under the above conditions for 30 min,
quenched by the addition of aqueous NH4Cl (10 ml) and
extracted with hexane (30 ml × 3). The organic layer was
washed with brine (30 ml × 2), dried (MgSO4) and evaporated.
The resulting residue was chromatographed on silica gel using
hexane as eluent to give 10a (23 mg, 36% from 4a) as a colorless
oil. This compound was identical with the authentic sample
prepared in our previous paper.13
(Z)-4-Cyclohexyl-1-phenylbut-1-en-3-yne 5g. Colorless oil, δH
(90 MHz, CDCl3) 0.90–1.95 and 2.61 (10H, m and 1H, m, Cy),
5.70 (1H, dd, J 12.1, 2.2, Ph-CH᎐CH-), 6.55 (1H, d, J 12.1, Ph-
᎐
CH᎐CH-), 7.25–7.35 and 7.53–7.94 (3H, m and 2H, m, Ph-H)
᎐
(HRMS m/z Calc. for C16H18: 210.1409. Found: 210.1400).
Bis[(Z)-o-(5,5-dimethylhex-1-en-3-ynyl)phenyl]di-n-butyl-
stannane 6a. Pale yellow oil, νmax(neat)/cmϪ1 2225 (C᎐C);
᎐
᎐
δH (90 MHz, CDCl3) 0.65–1.08 and 1.30–1.56 (6H, m and 12H,
m, Bun × 2), 1.26 (18H, s, But × 2), 5.58 (2H, d, J 11.8, Ph-
CH᎐CH- × 2), 6.53 (2H, d, J 11.8, Ph-CH᎐CH- × 2), 7.05–7.57
᎐
᎐
and 8.34–8.56 (6H, m and 2H, m, Ph-H) (HRMS m/z Calc. for
C32H39Sn (Mϩ Ϫ Bun, 57): 543.2074. Found: 543.2070).
Bis[(Z)-o-(oct-1-en-3-ynyl)phenyl]di-n-butylstannane 6b. Pale
yellow oil, νmax(neat)/cmϪ1 2200 (C᎐C); δ (90 MHz, CDCl3)
᎐
᎐
H
0.66–1.63 and 2.20–2.53 (32H, m and 4H, m, Bun × 4), 5.60
2-n-Butyl-1-phenyl-1-benzostibepine 10b
(2H, dt, J 11.8, 2.2, Ph-CH᎐CH- × 2), 6.57 (2H, d, J 11.8, Ph-
᎐
CH᎐CH- × 2), 7.10–7.59 and 8.33–8.53 (6H, m and 2H, m,
Ph-H) (HRMS m/z Calc. for C36H48Sn: 600.2778. Found:
600.2794).
᎐
The stannepine 4b was treated with SbCl3 and worked up
as described for the preparation of 10a to give 10b (27 mg,
41% from 4b) as a colorless oil. This compound was identi-
cal with the authentic sample prepared in our previous
paper.13
Bis[(Z)-o-(pent-1-en-3-ynyl)phenyl]di-n-butylstannane
6c.
Pale yellow oil, νmax(neat)/cmϪ1 2210 (C᎐C); δ (90 MHz,
᎐
᎐
H
CDCl3) 0.63–1.04 and 1.33–1.60 (6H, m and 12H, m, Bun × 2),
1.98 (6H, d, J 2.6, Me × 2), 5.58 (2H, dt, J 11.4, 2.6, Ph-
2-tert-Butyl-1-methyl-1-benzostibepine 11a
The stannepine 4a was treated with MeLi instead of PhLi and
worked up as described for the preparation of 10a to give 11a
(31 mg, 57% from 4a) as a colorless oil; δH (400 MHz, CDCl3)
0.95 (3H, s, Sb-Me), 1.18 (9H, s, But), 6.28 (1H, dd, J 6.0, 13.2,
4-H), 6.69 (1H, d, J 6.0, 3-H), 6.82 (1H, d, J 13.2, 5-H), 7.29–
7.49 and 7.61–7.71 (3H, m and 1H, m, Ph-H); δC (100 MHz,
CDCl3) Ϫ6.2 (q), 30.6 (q), 39.4 (s), 127.4 (d), 127.9 (d), 128.1
(d), 129.4 (d), 129.6 (d), 132.6 (d), 133.8 (s), 137.1 (d), 142.8 (s),
157.2 (s) (HRMS m/z Calc. for C15H19Sb: 320.0525. Found:
320.0533).
CH᎐CH- × 2), 6.51 (2H, d, J 11.4, Ph-CH᎐CH- × 2), 7.14–7.56
and 8.30–8.46 (6H, m and 2H, m, Ph-H) (HRMS m/z Calc. for
C30H36Sn: 516.1876. Found: 516.1839).
᎐
᎐
Bis[(Z)-o-(hept-1-en-3-ynyl)phenyl]di-n-butylstannane
6d.
Pale yellow oil, νmax(neat)/cmϪ1 2200 (C᎐C); δ (90 MHz,
᎐
᎐
H
CDCl3) 0.84–1.07, 1.36–1.70 and 2.26–2.42 (12H, m, 16H, m
and 4H, m, Bun × 2 and Prn × 2), 5.59 (2H, dt, J 12.1, 2.4, Ph-
CH᎐CH- × 2), 6.50 (2H, d, J 12.1, Ph-CH᎐CH- × 2), 7.17–7.40
᎐
᎐
and 8.38 (6H, m and 2H, d, J 7.7, Ph-H) (HRMS m/z Calc. for
C30H35Sn (Mϩ Ϫ Bun, 57): 515.1761. Found: 515.1753).
2-n-Butyl-1-methyl-1-benzostibepine 11b
Bis[(Z)-o-(dec-1-en-3-ynyl)phenyl]di-n-butylstannane 6e. Pale
The stannepine 4b was treated with MeLi instead of PhLi and
worked up as described for the preparation of 10a to give 11b
(22 mg, 41% from 4b) as a colorless oil; δH (400 MHz, CDCl3)
1.13 (3H, s, Sb-Me), 0.90, 1.22–1.58 and 2.36 (3H, t, J 7.5, 4H,
m and 2H, t, J 7.3, Bun), 6.30 (1H, dd, J 5.3, 12.3, 4-H), 6.46
(1H, d, J 5.3, 3-H), 6.92 (1H, d, J 12.3, 5-H), 7.23–7.35 and
7.46–7.50 (3H, m and 1H, m, Ph-H); δC (100 MHz, CDCl3)
Ϫ5.5 (q), 14.0 (q), 22.3 (t), 32.3 (t), 38.4 (t), 127.5 (d), 128.2 (d),
128.6 (d), 130.7 (d), 130.8 (d), 132.3 (d), 133.9 (s), 136.0 (d),
142.0 (s), 144.9 (s) (HRMS m/z Calc. for C15H19Sb: 320.0525.
Found: 320.0526).
yellow oil, νmax(neat)/cmϪ1 2205 (C᎐C); δ (90 MHz, CDCl3)
᎐
᎐
H
0.84–0.88, 1.29–2.02 and 2.31–2.38 (total 44H, m, Bun × 2 and
n-C6H13 × 2), 5.59 (2H, dt, J 11.7, 2.4, Ph-CH᎐CH- × 2), 6.51
᎐
(2H, d, J 12.1, Ph-CH᎐CH- × 2), 7.12–7.57 and 8.38 (6H, m
᎐
and 2H, d, J 7.3, Ph-H) (HRMS m/z Calc. for C36H47Sn
(Mϩ Ϫ Bun, 57): 599.2700. Found: 599.2706).
Bis[(Z)-o-(dodec-1-en-3-ynyl)phenyl]di-n-butylstannane 6f.
Pale yellow oil, νmax(neat)/cmϪ1 2200 (C᎐C); δ (90 MHz,
᎐
᎐
H
CDCl3) 0.69–1.03, 1.20–1.59 and 2.23–2.46 (total 52H, m,
Bun × 2 and n-C8H17 × 2), 5.58 (2H, dt, J 12.0, 2.4, Ph-CH᎐
᎐
CH- × 2), 6.53 (2H, d, J 12.0, Ph-CH᎐CH- × 2), 7.12–7.50 and
᎐
2-tert-Butyl-1-n-butyl-1-benzostibepine 12a
8.30–8.50 (6H, m and 2H, m, Ph-H) (HRMS m/z Calc. for
The stannepine 4a was treated with BunLi instead of PhLi and
worked up as described for the preparation of 10a to give 12a
(14 mg, 23% from 4a) as a colorless oil; δH (400 MHz, CDCl3)
1.20 (9H, s, But), 0.81 and 1.23–1.73 (3H, t, J 7.3 and 6H, m,
Bun), 6.24 (1H, dd, J 6.0, 13.2, 4-H), 6.76 (1H, d, J 6.0, 3-H),
6.78 (1H, J 13.2, 5-H), 7.28–7.32 and 7.60–7.72 (3H, m and 1H,
m, Ph-H) (HRMS m/z Calc. for C18H25Sb: 362.0995. Found:
362.0994.
C40H43Sn (Mϩ Ϫ Bun, 57): 655.3326. Found: 655.3299).
Bis[(Z)-o-(1-cyclohexylbut-1-en-3-ynyl)phenyl]di-n-butyl-
stannane 6g. Pale yellow oil, νmax(neat)/cmϪ1 2200 (C᎐C); δ (90
᎐
᎐
H
MHz, CDCl3) 0.77–1.76 and 2.58 (38H, m, and 2H, m, Bun × 2
and Cy-H × 2), 5.61 (2H, dt, J 11.7, 2.2, Ph-CH᎐CH- × 2),
᎐
6.50 (2H, d, J 11.7, Ph-CH᎐CH- × 2), 7.17–7.47 and 8.43 (6H,
᎐
m and 2H, d, J 8.1, Ph-H) (HRMS m/z Calc. for C36H43Sn
(Mϩ Ϫ Bun, 57): 595.2387. Found: 595.2362).
1,2-Di-n-butyl-1-benzostibepine 12b
Conversion of 4a into 2-tert-butyl-1-chloro-1-benzostibepine 9a
The stannepine 4a was treated with BunLi instead of PhLi and
worked up as described for the preparation of 10a to give 12b
(15 mg, 25% from 4b) as a colorless oil; δH (400 MHz, CDCl3)
0.85–1.20, 1.20–1.60 and 2.22–2.35 (8H, m, 8H, m and 2H, m,
Bun × 2), 6.25 (1H, dd, J 6.0, 13.0, 4-H), 6.50 (1H, d, J 6.0,
The reaction of 4a with SbCl3 was carried out in an NMR tube;
δH (400 MHz, CDCl3) 1.25 (9H, s, But), 6.41 (1H, dd, J 5.5,
12.7, 4-H), 6.68 (1H, d, J 5.5, 3-H), 7.07 (1H, d, J 12.7, 5-H),
7.25–7.59 and 7.92 (3H, m and 1H, d, J 6.4, Ph-H).
1968
J. Chem. Soc., Perkin Trans. 1, 2000, 1965–1969

View Article Online
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14 Preliminary communication; H. Sashida, A. Kuroda and T.
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15 (a) H. Sashida, K. Ito and T. Tsuchiya, J. Chem. Soc., Chem.
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Commun., 1991, 802; (b) H. Sashida, K. Sadamori and T. Tsuchiya,
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165; (e) H. Sashida and S. Yasuike, J. Heterocycl. Chem., 1998, 35,
725; ( f ) H. Sashida, Heterocycles, 1998, 48, 631; (g) H. Sashida
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(i) H. Sashida and A. Kuroda, Synthesis, 1999, 921; (j) H. Sashida
and A. Kawamukai, Synthesis, 1999, 1145.
17 A. K. Sawyer and H. G. Kuviila, Chem. Ind., (London), 1961, 260.
18 S. A. Kandil and R. E. Dessy, J. Am. Chem. Soc., 1966, 88, 3027.
19 K. Nozaki, K. Oshima and K. Uchimoto, J. Am. Chem. Soc., 1987,
109, 2547 and references cited therein.
20 Y. Ichinose, H. Oda, K. Oshima and K. Uchimoto, Bull. Chem. Soc.
Jpn., 1987, 60, 3468 and references cited therein.
21 N. Asao, J.-X. Liu, T. Sudoh and Y. Yamamoto, J. Chem. Soc.,
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22 (a) A. J. Leusink, H. A. Budding and J. W. Marsman, J. Organomet.
Chem., 1967, 9, 285; (b) A. J. Leusink, H. A. Budding and W. Drenth,
J. Organomet. Chem., 1967, 9, 295.
23 (a) A. J. Ashe, III, J. Am. Chem. Soc., 1971, 93, 6690; (b) A.
Meinema, C. J. R. Crispimromao and J. G. Noltes, J. Organomet.
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and R. J. M. Weustink, Recl. Trav. Chim. Pays-Bas, 1979, 98, 3.
24 A. J. Ashe, III, F. J. Drone, C. M. Kausch, J. Krocker and S. M.
Al-Taweel, Pure Appl. Chem., 1990, 62, 513.
25 (a) S. M. van der Kerk, J. Borsma and G. J. M. van der Kerk,
J. Organomet. Chem., 1981, 215, 303; (b) J. M. Schulman, R. L.
Disch and M. L. Sabio, J. Am. Chem. Soc., 1982, 104, 3875; (c) R. L.
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3-H), 6.88 (1H, d, J 13.0, 5-H), 7.30–7.33 and 7.60–7.75 (3H, m
and 1H, m, Ph-H) (HRMS m/z Calc. for C18H25Sb: 362.0995.
Found: 362.0999).
Conversion of 4a into 2-tert-butyl-1-chloro-1-benzoborepine 14a
A solution of 4a (71 mg, 0.17 mmol) in CHCl3 (2 ml) was added
in one portion with stirring to BCl3 (20 mg, 0.17 mmol) in
CHCl3 (10 ml) under an argon atmosphere at 0 ЊC. The reaction
mixture was vigorously stirred at room temperature for 30 min.
After evaporation of the solvent, the resulting residue was dis-
tilled under reduced pressure to give 14a (17 mg, 44%) as a pale
yellow oil, bp 90–100 ЊC (2 mmHg); δH (400 MHz, CDCl3) 1.43
(9H, s, But), 6.75 (1H, dd, J 8.4, 11.9, 4-H), 7.25 (1H, d, J 8.4,
5-H), 7.49 (1H, d, J 11.9, 3-H), 7.40–7.60 and 8.30–8.40 (3H, m
and 1H, m, Ph-H) (HRMS m/z Calc. for C14H16BCl: 230.1034,
232.1004. Found: 230.1031, 232.1011).
Conversion of 4a into 2-tert-butyl-1-phenyl-1-benzoborepine 15a
The stannepine 4a was treated with PhBCl2 instead of BCl3
and worked up as described for the preparation of 14a to give
15a (25 mg, 54%) as a colorless oil, bp 80–100 ЊC (4 × 10Ϫ6
mmHg); δH (400 MHz, CDCl3) 1.19 (9H, s, But), 6.50 (1H,
dd, J 7.0, 11.7, 4-H), 6.75 (1H, d, J 7.0, 3-H), 6.88 (1H, d,
J 11.7, 5-H), 7.32–7.52 and 7.71–7.80 (6H, m and 3H, m,
Ph-H); δC (100 MHz, CDCl3) 32.4 (q), 36.9 (s), 124.8 (d), 126.8
(d), 127.0 (d), 127.3 (d), 127.4 (d), 127.5 (d), 128.6 (d),
131.0 (d), 131.3 (d), 135.8 (d), 136.6 (s), 141.6 (s), 148.4 (s),
159.3 (s) (HRMS m/z Calc. for C20H21B: 272.1736. Found:
272.1734).
Acknowledgements
The authors wish to express thanks to Mr S. Yasuike (Faculty
of Pharmaceutical Sciences Horuriku University) for the 13C
NMR spectral measurements.
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J. Chem. Soc., Perkin Trans. 1, 2000, 1965–1969
1969