Synthesis of chiral organotin reagents: Synthesis of enantiomerically enriched bicyclo[2.2.1]hept-2-yl tin hydrides from camphor. X-Ray crystal structures of (dimethyl)[(1R,2S,4R)-1,7,7-trimethylbicyclo[2.2.1]hept-2-yl]tin chloride and methyl(phenyl)bis[(

Article abstract of DOI:10.1039/b200317c

2-Iodo-1,7,7-trimethylbicyclo[2.2.1]hept-2-ene 27 was prepared in two steps from camphor 23. Halogen-metal exchange using butyllithium followed by addition of the appropriate tin halide gave the corresponding bicyclo[2.2.1]-hept-2-en-2-ylstannanes 26, 35-

Full text of DOI:10.1039/b200317c

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Synthesis of chiral organotin reagents: synthesis of
enantiomerically enriched bicyclo[2.2.1]hept-2-yl tin hydrides
from camphor. X-Ray crystal structures of (dimethyl)[(1R,2S,4R)-
1,7,7-trimethylbicyclo[2.2.1]hept-2-yl]tin chloride and
methyl(phenyl)bis[(1R,2S,4R)-1,7,7-trimethylbicyclo[2.2.1]hept-
2-yl]stannane
1
Madeleine Helliwell, Eric J. Thomas* and Linda A. Townsend
The Department of Chemistry, The University of Manchester, Manchester, UK M13 9PL
Received (in Cambridge, UK) 8th January 2002, Accepted 3rd April 2002
First published as an Advance Article on the web 19th April 2002
2-Iodo-1,7,7-trimethylbicyclo[2.2.1]hept-2-ene 27 was prepared in two steps from camphor 23. Halogen–metal
exchange using butyllithium followed by addition of the appropriate tin halide gave the corresponding bicyclo[2.2.1]-
hept-2-en-2-ylstannanes 26, 35–38 and the (diphenyl)bis[1,7,7-trimethylbicyclo[2.2.1]hept-2-en-2-yl]stannane 48.
Reduction of the 1,7,7-trimethylbicyclo[2.2.1]hept-2-en-2-ylstannanes 35–38 using diimide took place predominantly
from the exo-face to give the endo-1,7,7-trimethylbicyclo[2.2.1]hept-2-ylstannanes 18, 43–45, endo–exo = ca. 80 : 20
in all cases. The methyl(phenyl)bis[endo-1,7,7-trimethylbicyclo[2.2.1]hept-2-yl]stannane 51 was prepared from the
diphenyl(methyl)[endo-1,7,7-trimethylbicyclo[2.2.1]hept-2-yl]stannane 40 by selective removal of one of the phenyl
groups using iodine to give the dialkyl(phenyl)tin iodide 49 which was treated with the alkenyllithium reagent
generated from the vinyl iodide 27 to give the bicyclo[2.2.1]hept-2-en-2-yl(dialkyl)phenylstannane 50, as a mixture
of epimers at the tin. Reduction using diimide then gave the methyl(phenyl)bis[endo-1,7,7-trimethylbicyclo[2.2.1]-
hept-2-yl]stannane 51 whose structure was established by X-ray crystallography.
The major (trimethyl)[1,7,7-trimethylbicyclo[2.2.1]hept-2-yl]stannane 39 was shown to be the endo-isomer by an
X-ray crystal structure determination of the tin chloride 46 prepared by treatment of the trimethylstannane 39 with
tin tetrachloride. The configurations of the other stannanes 40–42 were established by analogy and by comparison
of their 1H NMR spectra with those of 39. The dimethyl[1-dimethylaminomethyl-7,7-dimethylbicyclo[2.2.1]hept-2-
enyl](phenyl)stannane 56 was similarly prepared from the parent ketone 52. The stannanes 41/44 and 51 were
converted into the tin hydrides 59 and 61, but these gave only very modest enantiomeric excesses when used to
reduce the bromoketone 62.
Introduction
Tin hydrides are widely used reducing agents in organic
synthesis.1 The introduction of chiral, non-racemic tin hydrides
for the asymmetric reduction of alkyl halides and ketones
is therefore of interest, especially as the tin hydride may be
used in catalytic amounts along with a stoichiometric achiral
reducing agent. Most studies in this area have involved
tin hydrides with chiral ligands on the tin, although in some
cases, if the tin itself was attached to four different ligands,
this meant that mixtures of diastereoisomers were being
used. Examples of chiral tin hydrides investigated to date for
asymmetric synthesis include the o-[(R)-1-dimethylaminoethyl]-
phenyltin hydride 1,2 as a mixture of epimers at the tin, the
binaphthyltin hydrides 23 and 3,4 and monoterpene derived tin
hydrides including 4 and 5.5 The dimethylamino co-ordinated
naphthyltin hydrides 6 and 7 have also been prepared and fully
characterised.6
The enantiomeric excesses induced by reduction of alkyl
halides using these chiral tin hydrides have, generally, been only
modest by modern standards. This has been explained in terms
of the large distance between the Sn atom and the radical bear-
ing carbon atom in the transition structure for transfer of a
hydrogen from a tin hydride to a prochiral carbon radical.7
Exciting exceptions are, however, Lewis acid catalysed reduc-
tions of α-halocarbonyl compounds.8 Extremely high enantio-
meric excesses have been observed in these systems; for
example, the reduction of the α-bromo-ester 8 using the tin
hydride 10 in the presence of the salen complex 11 gave the
reduced ester 9 with ≥96% enantiomeric excess.9 Steroid based
tin hydrides, in the presence of the salen complex 11, similarly
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This journal is © The Royal Society of Chemistry 2002
DOI: 10.1039/b200317c

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reduced the halo-ester 8 giving the product 9 with enantiomeric
with the 2-lithiated bicyclo[2.2.1]hept-2-ene 19 followed by
excesses of 62 and 90%.10
reduction of the intermediate bicyclo[2.2.1]hept-2-enyl-
stannane 20 by hydrogenation or reaction with diimide, see
Scheme 1. At the onset of this work, it was expected that the
During the course of our own work, enantiomerically
enriched bicyclo[2.2.1]hept-2-yl(diphenyl)tin hydrides were
prepared using Diels–Alder reactions of (E)-3-triphenyl-
acrylates to assemble the bicyclic nucleus.11–13 Functional group
transformations then led to the preparation of several bicyclo-
[2.2.1]heptyltin hydrides including the ethers 12–15. These tin
hydrides did not prove to be useful for asymmetric synthesis,
although these preliminary studies were not carried out in the
presence of a Lewis acid. Nevertheless, it was felt that further
work on the chemistry of bicyclo[2.2.1]heptyl tin hydrides was
justified; for example, it was hoped that by the incorporation of
a suitably positioned nitrogen in the chiral ligand, the trajectory
of the hydrogen to be transferred in the reduction step, e.g. of a
prochiral radical, would be controlled.
Scheme 1 Proposed synthesis of bicyclo[2.2.1]hept-2-yl(dialkyl)tin
hydrides.
syn-7-methyl substituent would direct reduction of the double-
bond to the endo-face giving more of the exo-isomers 22 but
this remained to be established.
A Shapiro reaction was initially investigated for generation
of the vinyllithium intermediate 19. The 2,4,6-triisopropyl-
phenyl hydrazone 25 was prepared from camphor 2315 but
treatment with sec-butyllithium followed by triphenyltin
chloride gave variable yields (19–57%) of the triphenylvinyl-
stannane 26, see Scheme 2. As an alternative route to a
We now report the synthesis of enantiomerically enriched
bicyclo[2.2.1]hept-2-ylstannanes from camphor,
a readily
available monoterpene. This work complements Diels–Alder
approaches to stannanes of this type. Indeed, a synthesis of a
stannane identified as the exo-1,7,7-trimethylbicyclo[2.2.1]hept-
2-yl(trimethyl)stannane 18 from α-pinene 16 via exo-2-bromo-
bornane 17 was reported several years ago, an electron transfer
mechanism being postulated for the reaction between the
bromide 17 and trimethyltin sodium,14 although the use of the
corresponding tin hydride for asymmetric synthesis was not
investigated.
Scheme 2 Reagents and conditions: i, trisyl hydrazide,† MeCN,
concentrated HCl, rt, 16 h (76%); ii, TMEDA, hexane, s-BuLi, 2 h, Ϫ55
ЊC to 0 ЊC then Ph3SnCl, rt, 16 h (19–57%); iii, hydrazine hydrate,
EtOH, reflux 18 h (90%); iv, I2, 1,1,3,3-tetramethylguanidine, 1 h (49%);
v, BuLi, Ph3SnCl, 1 h, Ϫ78 ЊC (74%).
vinyllithium intermediate equivalent to 19, the vinyl iodide 27
was prepared from camphor hydrazone 24.16,17 In this case,
treatment with butyllithium followed by the addition of tri-
phenyltin chloride gave a more reliable yield (74%) of the
bicyclo[2.2.1]hept-2-en-2-yl(triphenyl)stannane 26. However,
attempts to reduce this vinylstannane to the corresponding
saturated bicyclo[2.2.1]hept-2-ylstannane (21, R = Ph) were
Results and discussion
The bicyclo[2.2.1]heptyltin hydrides 22 were to be prepared
from the corresponding phenyl substituted stannanes 21 which
were to be obtained by reaction of the appropriate tin halide
† The IUPAC name for trisyl hydrazide is 2,4,6-triisopropylbenzene-
sulfonohydrazide.
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Table 1 Preparation of bicyclo[2.2.1]hept-2-yl[trialkyl(aryl)]stannanes
Vinyl stannane
Yield (%)
74
Bicyclo[2.2.1]heptylstannane
R1
R2
R3
endo-isomer
exo-isomer
endo–exo ratio
Yield (%)
Ph
Ph
Me
Ph
Me
Ph
Ph
Me
Ph
Ph
tBu
26
35
36
37
38
–
–
–
Me
Me
Me
Ph
69
70
71
65
39
40
41
42
18
43
44
45
85 : 15
78 : 22
78 : 22
82 : 18
80
89
97
67
unsuccessful. Only unchanged starting material was recovered
from attempts at alkene hydrogenation (10% Pd/C, methanol,
1–5 atm H2; 5% Rh/C, tetrahydrofuran, water, 5 atm H2; PtO2,
ethanol, 5 atm H2) and reduction using diimide was also
unsuccessful.
To ascertain whether steric hindrance was responsible for the
problems encountered in the reduction of the vinylstannane 26,
it was decided to prepare a series of structurally related alkenyl-
stannanes to see whether any could be reduced to the corre-
sponding alkylstannanes. For this purpose a series of tin halides
had to be prepared. Diphenyl(methyl)tin iodide 30 was
prepared from triphenyltin hydride 28 by deprotonation and
alkylation using methyl iodide to give methyl(triphenyl)-
stannane 29. Treatment of this with iodine gave the diphenyl-
(methyl)tin iodide 30,18 see Scheme 3. Dimethyl(phenyl)tin
The endo-configuration of the major bicyclo[2.2.1]hept-2-
yl(trimethyl)stannane 39 was established by an X-ray crystal
structure determination for the corresponding dimethyltin
chloride 46 prepared by treatment of the trimethylstannane
with one equivalent of tin() chloride.14 This gave a good yield
of an 85 : 15 mixture of the endo and exo-isomers of the tin
chlorides from which the major endo-chloride 46 was isolated
by recrystallisation. Fig. 1 shows a projection of a molecule
Scheme 3 Reagents and conditions: i, LDA, THF, Ϫ78 ЊC, 1 h then
MeI, Ϫ10 ЊC to 40 ЊC (99%); ii, I2, CH2Cl2, rt, 10 min (89%); iii,
MeMgBr, THF, Ϫ78 ЊC then rt, 2 h (97%); iv, I2, CH2Cl2, rt, 30 min
(83%); v, tBuMgCl, THF, Ϫ78 ЊC then 10 ЊC, 1 h, (87%).
Fig. 1 Structure of the bicyclo[2.2.1]heptyltin chloride 46 as deter-
mined by X-ray crystallography.
of 46 as established by the X-ray crystal study which clearly
illustrates the assigned endo-configuration.
iodide 3319 was obtained by reacting diphenyltin dichloride 31
with methyl magnesium bromide to give dimethyl(diphenyl)-
stannane 32 which gave the dimethyl(phenyl)tin iodide 33 on
treatment with iodine. The tert-butyl(diphenyl)tin chloride 34
was prepared by treatment of diphenyltin dichloride 31 with
one equivalent of tert-butyllithium.
Generation of a vinyllithium corresponding to 19 from the
vinyl iodide 27 using butyllithium, and treatment of this
intermediate with trimethyltin chloride and the tin halides 30,
33 and 34 gave the corresponding bicyclo[2.2.1]hept-2-en-2-
ylstannanes 35–38 in yields 65–71% based on the vinyl iodide
27, see Table 1. Hydrogenation of the trimethyl vinylstannane
35 gave only unchanged starting material (5% Pd/C, ethanol, 5
atm of H2; PtO2, ethanol, 5 atm. of H2). However, reduction of
the vinylstannanes 35–38 using diimide was successful and gave
the endo-bicyclo[2.2.1]hept-2-ylstannanes 39–42 in excellent
yields together with ca. 15–20% of their exo-diastereoisomers.
The bicyclo[2.2.1]hept-2-yl(dimethyl)tin chloride 46 was
converted into the corresponding monomethyltin dichloride
4714 using a second equivalent of tin() chloride, and back into
the endo-trimethylstannane 39 on reaction with methyllithium.
In this case the product obtained was identical to the major
product from the diimide reduction of the vinylstannane 35 so
confirming that no epimerisation had taken place during these
reactions. This sequence also provided a stereochemically
homogeneous sample of the endo-stannane 39.
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Table 2 13C NMR data for the bicyclo[2.2.1]heptylstannanes 18, 39–42
δC(ppm) (nJCSn/Hz)
Compound
C(1)
C(2)
C(3)
C(4)
C(5)
C(6)
C(7)
C(8)
C(9/10)
39
40
41
42
18
49.0
49.1
48.5
49.0
48.8
35.1
(426/408)
36.9
(449/428)
35.5
(437/412)
38.0
32.9
33.1
32.4
33.5
34.0
45.7
(18.2)
45.5
(20.0)
45.2
28.5
28.2
27.8
28.2
27.8
36.8
(41.9)
37.7
(42.5)
36.8
(46.6)
38.04
(31.0)
41.8
48.0
(48.8)
48.1
(57.8)
47.4
(52)
48.0
(53.4)
47.1
16.2
16.3
15.6
16.7
17.5
19.5/18.8
19.5/18.9
19.0/18.4
19.7/18.9
20.6/19.8
45.4
(16.2)
45.8
(368/361)
37.9
The endo configuration assigned to the monomethyltin
dichloride 47 was consistent with the three-bond carbon to tin
couplings observed in its 13C NMR spectrum. Such couplings
vary with torsional angle according to a Karplus relationship
and so in conformationally rigid structures are a reliable guide
3
to stereochemistry.20 In bicyclo[2.2.1]hept-2-ylstannanes, JCSn
between the tin and C(7) is diagnostic of the endo or exo
orientation of the tin, being ca. 50–60 Hz if the tin is endo and
very small, ca. 0 Hz, if the tin is exo, see Fig. 2.21 The three bond
Fig. 2 Some 13C NMR couplings (Hz) observed for endo and exo-
bicyclo[2.2.1]hept-2-yl(trimethyl)stannanes.
coupling between the tin and C(6) also depends on the orient-
ation of the tin substituent with couplings of ca. 36 and 67 Hz
being recorded for endo and exo-stannanes, respectively, see
Fig. 2.21 For the tin dichloride 47 the three-bond coupling
3
between the tin and C(7), JC(7)Sn, was 94 Hz, fully supportive
3
of the endo position of the tin. A JC(7)Sn of 48.8 Hz was
also observed for the major bicyclo[2.2.1]hept-2-yl(trimethyl)-
stannane 39 consistent with the endo-configuration assigned on
the basis of the X-ray crystal structure of 46.
The other major bicyclo[2.2.1]hept-2-ylstannanes 40–42 were
assigned the endo-configuration by analogy and on the basis of
comparison of their 13C NMR data with those of the exo- and
endo-isomers 18 and 39. The endo-assignments for the major
Scheme 4 Reagents and conditions: i, I2, CH2Cl2, 20 min (99%); ii, 27,
BuLi, Ϫ78 ЊC, 1 h, then add 49 (60%); iii, toluene-p-sulfonyl hydrazide,
NaOAc, (MeOCH2)2 (93%).
3
isomers were also supported by their JC(7)Sn couplings, see
ing ca. 20% of its exo-isomer 43) with one equivalent of iodine
gave the dialkyl(phenyl)tin iodide 49 (Scheme 4). Treatment of
this with the vinyllithium reagent generated from the vinyl
iodide 27 gave the vinylstannane 50 together with ca. 20% of
its exo-isomer, as a mixture of diastereoisomers at the tin. This
mixture was not separated but was successfully reduced using
diimide to give the bis-endo-bicyclo[2.2.1]hept-2-yl(methyl)-
(phenyl)stannane 51 again containing minor amounts of the
mono- and bis-exo-isomers. Recrystallisation of this mixture
gave pure samples of the bis-endo-stannane 51 the structure of
which was confirmed by X-ray crystallography. Fig. 3 shows
the structure of this bis-bicyclo[2.2.1]hept-2-ylstannane as
determined by crystallography which illustrates the bis-endo-
stereochemistry. Again this crystal structure determination
confirms that the diimide reductions of the bicyclo[2.2.1]hept-
2-en-2-ylstannanes take place selectively from the exo-direction
to give rise to the formation of the endo-stannanes as the major
products.
Table 2. The minor products had similar 13C NMR spectra but
no observable three bond Sn–C(7) coupling, the data for the
minor exo-trimethylstannane 18 being given in Table 2.‡
Having prepared a series of mono-bicyclo[2.2.1]hept-2-
ylstannanes by reduction of the corresponding vinylstannanes,
it was decided to see whether this approach could be extended
to the synthesis of bis[bicyclo[2.2.1]hept-2-yl]stannanes. The
reaction of diphenyltin dichloride 31 with two equivalents of
the vinyllithium species generated by treatment of the vinyl
iodide 27 with butyllithium gave the bis[bicyclo[2.2.1]hept-2-en-
2-yl](diphenyl)stannane 48 but attempts to reduce this with
diimide were unsuccessful. However, reaction of the endo-
bicyclo[2.2.1]hept-2-yl(diphenyl)(methyl)stannane 40 (contain-
‡ Comparison of the literature 13C NMR data for the exo-stannane 18
with the data obtained for the exo- and endo-bicyclo[2.2.1]hept-2-
yl(trimethyl)stannanes prepared during the course of our work,14
suggest that the major stannane prepared from the exo-bromide 17 was
in fact the endo-isomer 39 and not the exo-isomer 18 as reported. This
revision of structure is supported by comparison of the 13C data for the
corresponding tin chloride 46 and tin dichloride 47 which suggest that
our endo compounds are the same as those described as being exo in the
literature.14
En route to an amino-substituted tin hydride, 8-dimethyl-
aminocamphor 52 was prepared from camphor following the
literature procedure.22 This was converted into the hydrazone 53
which on treatment with tetramethylguanidine and iodine,
following the procedure used to prepare the iodide 27, gave the
J. Chem. Soc., Perkin Trans. 1, 2002, 1286–1296
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Fig. 3 Structure of the bis-bicyclo[2.2.1]heptylstannane 51 as deter-
mined by X-ray crystallography.
vinyl iodide 54 but only in a rather low yield (19%), together
with a minor product which may have been the rearranged
product 55 but which was not isolated sufficiently pure for full
identification. Treatment of the iodide 54 with butyllithium
followed by the addition of dimethyl(phenyl)tin iodide 33 gave
the vinylstannane 56. The spectroscopic data obtained for 56
didn’t indicate any significant nitrogen–tin co-ordination. For
example, the two diastereotopic methyl groups gave rise to
Scheme 5 Reagents and conditions: i, hydrazine hydrate (50%); ii, I2,
1,1,3,3-tetramethylguanidine (19%); iii, BuLi, Ϫ78 ЊC, then PhSnMe2I
1
(66%); iv, tosyl hydrazide, NaOAc.
peaks in its H NMR spectrum at δ 0.03 and δ 0.00 ppm with
2JSnH couplings of 56.4/54 and 55.9/53.4 Hz which are very
similar to the corresponding peaks in the 1H NMR spectrum of
the vinylstannane 37. Nevertheless, this vinylstannane was
reduced using di-imide to give a stannane believed to be the
endo-dimethyl(phenyl)stannane 57 but this was not fully
characterised because of insufficient material (Scheme 5).
Finally, the mixture of the phenyldimethylstannanes 41–44
(41–44 = 78 : 22) was taken through to the tin hydride 59
(containing ca. 20% of its exo-isomer) by cleavage of the
phenyl group using iodine and reduction of the iodide 58 so
obtained using sodium borohydride. The bis-bicyclo[2.2.1]-
heptylstannane 51 was similarly converted via the iodide 60 into
the stannane 61. However, preliminary studies of the reduction
of bromoketone 62 using these tin hydrides, albeit in the
absence of a Lewis acid, gave the debrominated product 63 with
less than 5% ee.
Conclusion
This work has shown that endo-bicyclo[2.2.1]hept-2-ylstannanes
can be prepared by coupling bicyclo[2.2.1]hept-2-en-2-yllithium
with tin halides followed by reductive removal of the double-
bond using diimide. This approach has been used to prepare
both mono- and bis-bicyclo[2.2.1]hept-2-ylstannanes and is
also useful for the preparation of dialkylamino-substituted
stannanes. The selective formation of endo-isomers during the
diimide reduction of the vinylstannanes was unexpected since
a syn-7-methyl substituent usually directs bidentate attack on
a bicyclo[2.2.1]hept-2-ene to the endo-face giving rise to the
formation of exo-products. The selectivity observed here may
well be due to the bulk of the tin and its substituents. The steric
interaction between a exo-2-tin substituent and the 7-syn-
methyl group in the transition structure for endo-reduction may
be substantial and lead to a lower energy transition structure
for exo-attack.
stannanes were reduced, e.g. the tert-butyldiphenylstannane 38
was reduced to the endo- and exo-bicyclo[2.2.1]heptylstannanes
42 and 45. Perhaps electronic effects involving increased
electron withdrawal by the triphenyltin group are also involved
although this observation was not examined further.
Further work in this area will be to evaluate further the
potential of enantiomerically enriched bicyclo[2.2.1]heptyltin
hydrides and related tin reagents for asymmetric synthesis,
specifically the possible advantages of having a suitably posi-
tioned nitrogen substituent.
Experimental
1H and 13C NMR were recorded on Varian INOVA 300
(300 MHz) or Varian Unity 500 (500 MHz) spectrometers
in chloroform-d1 at 300 MHz for protons and at 75 MHz for
carbon unless otherwise stated. Coupling constants J are given
The lack of success in attempts to reduce the bicyclo[2.2.1]-
hept-2-en-2-yl(triphenyl)stannane 26 using diimide cannot be
attributed solely to steric effects since analogous more hindered
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in Hz. Coupling constants for 119/117Sn–13C (nJCSn) and 119/117Sn–
1H (nJHSn) are quoted when observed. When couplings to
119Sn and 117Sn are discrete they are quoted with the value
for 119Sn given first. Infrared spectra were recorded on an ATI
Mattson Genesis Series FTIR spectrometer as thin films
(produced by evaporation of a dichloromethane solution) on a
sodium chloride plate. Low resolution chemical ionisation (CI)
and electron impact (EI) mass spectra were recorded on a
Fisons TRIO 2000 quadrupole mass spectrometer. All high
resolution mass spectra were recorded on a Kratos Concept-1S
lithium (1.5 M in hexanes; 0.52 cm3, 0.79 mmol). The solution
was stirred at Ϫ78 ЊC for 30 min before the addition of tri-
phenyltin chloride (303 mg, 0.79 mmol) in THF (5 cm3), stirred
at Ϫ78 ЊC for 3 h then methanol (1 cm3) was added. The solu-
tion was warmed to ambient temperature and partitioned
between water and diethyl ether. The aqueous phase was
extracted with diethyl ether (3 × 5 cm3) and the combined
extracts were dried over magnesium sulfate, filtered and concen-
trated under reduced pressure. Flash column chromatography
of the residue using petrol–triethylamine (100 : 1) as eluent
afforded the stannane 26 (270 mg, 74%) as a colourless oil.
mass spectrometer coupled to
a Mach 3 data system.
Compounds containing tin showed characteristic clusters of
peaks in their mass spectra, only those corresponding to 120Sn
are quoted.
(1R,4R)-2-Iodo-1,7,7-trimethylbicyclo[2.2.1]hept-2-ene 2716,17
A nitrogen flushed three-necked flask was fitted with a mech-
anical stirrer, condenser and gas outlet. The flask was charged
with the hydrazone 24 (22.76 g, 137 mmol) and diethyl ether
(200 cm3) containing 1,1,3,3-tetramethylguanidine (60.1 cm3,
479 mmol). A solution of iodine (72.96 g, 287 mmol) in diethyl
ether (600 cm3) was added over a period of 1 h, during which
time the pale yellow solution turned deep pink and then brown
in colour. On completion of the addition, the mixture was
stirred for a further 15 min at ambient temperature. The mix-
ture was washed with hydrochloric acid (3.5 M, 3 × 150 cm3),
saturated aqueous sodium thiosulfate (3 × 150 cm3) and satur-
ated aqueous sodium bicarbonate (3 × 100 cm3) before being
dried over magnesium sulfate, filtered and concentrated under
reduced pressure. Repeated chromatography of the residue
using petrol as eluent gave the title compound 27 (17.75 g, 49%)
as a colourless oil, [α]D Ϫ15.5 (c 0.62 in CHCl3) (lit.17 [α]D Ϫ8.8
in CHCl3) (Found: Mϩ, 262.0219. C10H15I requires M,
262.0220); νmax/cmϪ1 2986, 2955, 2872 and 812; δH 6.33 (1 H, d,
J 3.5, 3-H), 2.30 (1 H, t, J 3.5, 4-H), 1.72 (1 H, m), 1.38 (1 H,
m), 0.95 (2 H, m), 0.90 (3 H, s, 1-CH3), 0.78 and 0.77 (each 3 H,
s, 2 × 7-CH3); δC 142.9, 106.6, 57.9, 55.6. 54.5, 30.5, 25.1, 20.2,
19.4 and 15.1; m/z (EI) 262 (Mϩ, 38%), 247 (14), 135 (9) and 49
(100).
Optical rotations were recorded at ambient temperature (22
ЊC) on an Optical Activity AA-100 polarimeter at 589 nm using
either chloroform or hexane as solvent and are given in 10Ϫ1 deg
cm2 gϪ1
.
Preparative high performance liquid chromatography was
carried out using a Gilson 303 pump (with manometric
module) attached to a Dynamax 83–121-C, 60 Å, 300 × 10 mm
column. The packed column contained a SiO 8 µ stationary
phase. The mobile phase consisted of hexane. Detection was by
ultraviolet (UV) absorption at 255 nm monitored by a Gilson
115 UV detector. Chromatography refers to flash column
chromatography and was performed using Merck silica gel
60H (40–63 µ, 230–300 mesh) as the stationary phase. Thin
layer chromatography was performed using Machery Nagel
DC-Fertigplatten SIL G-25 UV254 silica gel glass plates.
Visualisation was by UV absorption at 254 nm and by treat-
ment with 10% w/v methanolic dodecamolybdophosphoric
acid and subsequent heating.
Petrol refers to the fraction with bp 40–60 ЊC and was
redistilled prior to use. Tetrahydrofuran was dried over
sodium–benzophenone and distilled under an atmosphere of
nitrogen. Dichloromethane was dried over calcium hydride
and distilled under an atmosphere of nitrogen. Diethyl ether
and hexane were dried over sodium wire. All other com-
mercially available reagents were purified following standard
procedures.
Methyl(triphenyl)stannane 29
Butyllithium (1.5 M in hexanes; 10.1 cm3, 15.1 mmol) was
added to a solution of diisopropylamine (2.31 cm3, 16.4 mmol)
in THF (2 cm3) at 0 ЊC. The mixture was stirred for 20 min
before being cooled to Ϫ78 ЊC. A solution of triphenyltin
hydride 28 (4.81 g, 13.7 mmol) in THF (4 cm3) was added and
the pale yellow solution immediately darkened to a custard
yellow colour. The solution was stirred at Ϫ78 ЊC for 1 h before
being warmed to Ϫ10 ЊC. Methyl iodide (0.94 cm3, 15.1 mmol)
was added and the mixture was heated at 45 ЊC for 1 h during
which time the solution adopted a dark brown colour. After
cooling to ambient temperature, saturated aqueous ammonium
chloride (6 cm3) was added and the mixture was extracted using
diethyl ether (3 × 8 cm3). The combined organic extracts were
dried over magnesium sulfate, filtered and concentrated under
reduced pressure to afford the stannane 29 (4.93 g, 99%) as a
pale cream solid, used without further purification, mp 61–63
ЊC (Found: Mϩ, 366.0429. C19H18Sn requires M, 366.0429);
νmax/cmϪ1 3048, 3004, 1479, 1427, 1075 and 996; δH 7.50 (15 H,
m, Ar–H) and 0.78 (3 H, s, 2JHSn 56.3/54.0, Sn–CH3); δC 139.1,
136.7, 128.8, 128.4 and Ϫ10.6; m/z (EI) 366 (Mϩ, 2%) and 351
(100).
[(1R,4R)-1,7,7-Trimethylbicyclo[2.2.1]hept-2-en-2-yl]-
(triphenyl)stannane 26
From trisylhydrazone 25. A solution of the trisylhydrazone
2515 (1.0 g, 2.31 mmol) and TMEDA (5 cm3) in hexane (12 cm3)
was cooled to Ϫ55 ЊC before the addition of sec-butyllithium
(1.3 M in hexanes; 3.91 cm3, 5.08 mmol) over 15 min. The
mixture was stirred at Ϫ55 ЊC for 2 h before being warmed
slowly to 0 ЊC. The evolution of nitrogen gas was observed. On
cessation of nitrogen evolution a solution of triphenyltin
chloride (1.07 g, 2.77 mmol) in THF (5 cm3) was added. The
reaction mixture was warmed to ambient temperature and was
stirred for 16 h before being poured into distilled water
(10 cm3). The solution was extracted using diethyl ether (3 × 10
cm3), and the combined organic phases were washed with water
(3 × 10 cm3) before being dried over magnesium sulfate, filtered
and concentrated under reduced pressure. Column chrom-
atography of the residue using petrol–triethylamine (100 : 1)
as eluent afforded the title compound 26 (639 mg, 57%) as a
colourless oil, [α]D Ϫ23.3 (c 1.7, CHCl3) (Found: Mϩ, 486.1366.
C28H30Sn requires M, 486.1368); νmax/cmϪ1 3062, 3048, 3015,
2950, 1479, 1428 and 1074; δH 7.67 (6 H, m, Ar–H), 7.45 (9 H,
m, Ar–H), 6.59 (1 H, d, J 3, 3JHSn 46.6, 3-H), 2.52 (1 H, t, J 3,
4-H), 1.17–1.95 (4 H, m, 5-H2 and 6-H2) and 1.12, 1.04 and 0.89
(each 3 H, s, 1-CH3 and 2 × 7-CH3); m/z (CI) 486 (Mϩ, 3%), 426
(100) and 368 (92).
Diphenyl(methyl)tin iodide 3018
Iodine (3.37 g, 13.3 mmol) was added in small portions to
methyl(triphenyl)stannane 29 (4.85 g, 13.3 mmol) dissolved in
dry dichloromethane (30 cm3) over 10 min. The mixture was
stirred for a further 20 min before being concentrated. The
residue was distilled under reduced pressure to furnish the tin
iodide 30 (2.61 g, 89%) as a yellow oil, bp 158–164 ЊC, 1.0
mmHg (lit.18 115–116 ЊC, 0.008 mmHg) (Found: Mϩ ϩ NH4,
From vinyl iodide 27. A solution of vinyl iodide 27 (200 mg,
0.75 mmol) in THF (1 cm3) at Ϫ78 ЊC was treated with butyl-
J. Chem. Soc., Perkin Trans. 1, 2002, 1286–1296
1291

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433.9429. C13H17INSn requires M, 433.9428); νmax/cmϪ1 3064,
3047, 1480, 1429, 1073, 997 and 756; δH 7.44–7.74 (10 H, m,
filtered and concentrated under reduced pressure. Chrom-
atography of the pale brown residue using petrol–triethylamine
(100 : 1) afforded the stannane 35 (380 mg, 67%) as a colourless
oil, [α]D Ϫ26.5 (c 0.34 in CHCl3); νmax/cmϪ1 2985, 2950, 2868
2
Ar–H) and 1.29 (3 H, s, JHSn 57.5, Sn–CH3); δC 137.3, 135.8,
130.0, 128.9 and Ϫ3.0; m/z (CI) 434 (Mϩ ϩ 18, 3%), 418 (10),
3
373 (14) and 356 (100).
and 767; δH (500 MHz) 6.04 (1 H, d, J 3, JHSn 44, 3-H), 2.17
(1 H, t, J 3.3, 4-H), 1.66 and 1.37 (each 1 H, m), 0.94 (3 H, s,
1-CH3), 0.74 (2 H, m), 0.68 and 0.65 (each 3 H, s, 2 × 7-CH3)
and 0.00 [9 H, s, 2JHSn 55.0/53.0, Sn(CH3)3]; δC (125 MHz) 152.4
(1JCSn 458, 2-C), 145.1 (2JCSn 24.2, 3-C), 57.2 (1-C), 56.2 (7-C),
53.7 (3JCSn 48.6, 4-C), 31.3 (6-C), 24.4 (5-C), 19.84 and 19.76
(9-C and 10-C), 15.0 (8-C) and Ϫ9.6 [1JCSn 344/330, Sn(CH3)3];
m/z (EI) 300 (Mϩ, 16%), 285 (57), 135 (65) and 121 (100).
Dimethyl(diphenyl)stannane 3219
Methylmagnesium bromide (3.0 M in diethyl ether; 2.04 cm3,
6.1 mmol) was added dropwise to a solution of dichloro-
(diphenyl)stannane 31 (1.0 g, 2.9 mmol) in THF (2 cm3) at Ϫ78
ЊC. The mixture was warmed to ambient temperature and
was stirred for 2 h before the addition of saturated aqueous
ammonium chloride (2 cm3). The mixture was extracted using
diethyl ether (3 × 5 cm3) and the combined organic layers were
dried over magnesium sulfate, filtered and concentrated under
reduced pressure to yield the stannane 32 (856 mg, 97%) as a
pale yellow oil used without further purification (Found: Mϩ Ϫ
CH3, 289.0041. C13H13Sn requires M, 289.0038); νmax/cmϪ1
3063, 2916, 1428, 1075 and 752; δH 7.23 (4 H, m, Ar–H), 7.06
(6 H, m, Ar–H) and 0.22 (6 H, s, 2JHSn 55.9/53.4, 2 × Sn–CH3);
δC 140.6, 136.2, 128.5, 128.2 and Ϫ10.1; m/z (CI) 304 (Mϩ,
10%), 289 (4) and 244 (100).
Diphenyl(methyl)[(1R,4R)-1,7,7-trimethylbicyclo[2.2.1]hept-2-
en-2-yl]stannane 36
Following the general procedure, vinyl iodide 27 (1.50 g, 5.7
mmol) in dry THF (8 cm3), butyllithium (1.6 M in hexanes;
3.7 cm3, 6.3 mmol) and the tin iodide 30 (2.62 g, 6.3 mmol)
dissolved in THF (5 cm3) gave, after flash column chrom-
atography of the residue using petrol–triethylamine (100 : 1) as
eluent, the title compound 36 (1.64 g, 67%) as a colourless oil,
[α]D Ϫ28.8 (c 0.34 in CHCl3) (Found: Mϩ, 424.1213. C23H28Sn
requires M, 424.1212); νmax/cmϪ1 3063, 2986, 2950, 2868, 1428
and 1075; δH (500 MHz) 7.58 (4 H, m, Ar–H), 7.41 (6 H, m
Ar–H), 6.43 (1 H, d, J 2.9, 3JHSn 44.5, 3-H), 2.44 (1 H, t, J 3.2,
4-H), 1.90 (1 H, m), 1.60 (1 H, m), 1.10, 0.95 and 0.85 (each 3
H, s, 1-CH3 and 2 × 7-CH3), 1.04 (2 H, m) and 0.63 (3 H, s, 2JHSn
55.6/53.2, Sn–CH3); δC (125 MHz) 149.8 (2-C), 148.7 (2JCSn
23.5, 3-C), 140.3 and 140.2 (ipso-C), 136.6 (2JCSn 34.9, ortho-C),
128.5 and 128.2 (meta-C and para-C), 57.5 (2JCSn 39.0, 1-C),
56.6 (7-C), 53.9 (3JCSn 54.4, 4-C), 31.4 (6-C), 24.3 (5-C), 19.9
(9-C and 10-C), 15.3 (8-C) and Ϫ10.1 (1JCSn 371, Sn–CH3); m/z
(EI) 424 (Mϩ, 34%), 409 (100), 381 (27), 289 (49), 197 (45) and
91 (87).
Dimethyl(phenyl)tin iodide 3319
Iodine (4.31 g, 17.0 mmol) dissolved in dichloromethane
(25 cm3) was added dropwise to a solution of dimethyl-
(diphenyl)stannane 32 (5.14 g, 17.0 mmol) in dichloromethane
(25 cm3) over a period of 30 min. The mixture was stirred at
ambient temperature for 3 h before being concentrated under
reduced pressure. Distillation of the residue under reduced
pressure afforded the stannane 33 (4.96 g, 83%) as a colourless
oil, bp 100–101 ЊC, 1.4 mmHg (lit.19 bp 100–101 ЊC, 1.4 mmHg)
(Found: Mϩ, 353.8928. C8H11ISn requires M, 353.8928);
νmax/cmϪ1 3064, 3048, 1429, 1073 and 763; δH 7.63 (2 H, m,
2
Ar–H), 7.47 (3 H, m, Ar–H) and 1.12 (6 H, s, JHSn 58.1/55.6,
Dimethyl(phenyl)[(1R,4R)-1,7,7-trimethylbicyclo[2.2.1]hept-2-
en-2-yl]stannane 37
2 × Sn–CH3); δC 137.4, 135.2, 129.8, 128.7 and Ϫ2.3; m/z (CI)
354 (Mϩ, 4%), 294 (100), 244 (23) and 202 (18).
Following the general procedure, vinyl iodide 27 (1.31 g,
5.0 mmol) in dry THF (4 cm3), butyllithium (1.6 M in hexanes;
3.42 cm3, 5.5 mmol) and the tin iodide 33 (1.93 g, 5.5 mmol) in
THF (2 cm3) gave, after flash column chromatography of the
residue using petrol–triethylamine (100 : 1) as eluent, the title
compound 37 (1.29 g, 71%) as a pale yellow oil, [α]D Ϫ26.4
(c 3.18 in CHCl3) (Found: Mϩ, 362.1053. C18H26Sn requires M,
362.1055); νmax/cmϪ1 2985, 2949, 2868 and 1428; δH 7.26 (2 H,
m, Ar–H), 7.08 (3 H, m, Ar–H), 6.02 (1 H, d, J 3, 3-H), 2.09
(1 H, t, J 3.3, 4-H), 1.56 and 1.27 (each 1 H, m), 0.80 (3 H, s,
1-CH3), 0.66 (2 H, m), 0.58 and 0.54 (each 3 H, s, 7-CH3), 0.10
and 0.09 (each 3 H, s, 2JHSn 52.0, Sn–CH3); δC (125 MHz) 150.6
tert-Butyl(diphenyl)tin chloride 34
Dichlorodiphenylstannane 31 (4.00 g, 11.6 mmol) was dissolved
in dry THF (15 cm3) before being cooled to Ϫ78 ЊC. tert-
Butylmagnesium chloride (1.0 M in THF; 11.6 cm3, 11.6 mmol)
was added dropwise and the stirred mixture was warmed to
Ϫ10 ЊC over 1 h before the addition of saturated aqueous
ammonium chloride (10 cm3). The mixture was filtered through
Celite and the filtrate was extracted using diethyl ether (3 × 10
cm3). The combined organic layers were dried over magnesium
sulfate, filtered and concentrated under reduced pressure to
yield the title compound 34 (3.69 g, 87%) as a cream coloured oil
(Found: Mϩ Ϫ C(CH3)3, 308.9496. C12H10ClSn requires M,
308.9492); νmax/cmϪ1 3585, 3066, 3049, 2955, 2922, 2852, 1480,
1466, 1430, 1367, 1166, 1073 and 997; δH 7.32–7.85 (10 H, m,
2
(2-C), 146.4 (3-C, JCSn 25.9), 141.2 (ipso-C), 135.6 (ortho-C,
2JCSn 36.1), 127.7 and 127.5 (meta and para-C), 56.8 (1-C, 3JCSn
3
3
35.4), 55.8 (7-C, JCSn 17.4), 53.2 (4-C, JCSn 49.5), 30.8 (6-C),
23.9 (5-C), 19.3 (9-C and 10-C), 14.7 (8-C), Ϫ10.4 and Ϫ10.6
(2 × Sn–CH3, 1JCSn 354); m/z (CI) 362 (Mϩ, 10%), 302 (27) and
244 (100).
3
Ar–H) and 1.49 [9 H, s, JHSn 97.1/92.8, SnC(CH3)3]; δC 138.4,
136.1, 129.9, 128.9, 35.2 and 29.5; m/z (EI) 366 (Mϩ, 3%), 353
(6), 309 (100), 197 (25) and 154 (29).
Preparation of the bicyclo[2.2.1]hept-2-en-2-ylstannanes general
procedure: trimethyl[(1R,4R)-1,7,7-trimethylbicyclo[2.2.1]hept-
2-en-2-yl]stannane 35
tert-Butyl(diphenyl)[(1R,4R)-1,7,7-trimethylbicyclo[2.2.1]hept-
2-en-2-yl]stannane 38
Following the general procedure, vinyl iodide 27 (555 mg,
2.11 mmol) in THF (2 cm3), butyllithium (1.2 M in hexanes;
1.94 cm3, 2.33 mmol) and the tin chloride 34 (850 mg, 2.33
mmol) in THF (7 cm3) gave, after chromatography of the
residue using petrol–triethylamine (100 : 1) as eluent, the title
compound 38 (640 mg, 65%) as a colourless oil, [α]D Ϫ27.3
(c 1.42 in CHCl3) (Found: Mϩ Ϫ C(CH3)3, 409.0980. C22H25Sn
requires M, 409.0977); νmax/cmϪ1 3063, 2986, 2951, 2869, 1466,
1428 and 1073; δH 7.35–7.68 (10 H, m, Ar–H), 6.52 (1 H, d, J 3,
3JHSn 40.7, 3-H), 2.44 (1 H, t, J 3.4, 4-H), 1.88 (1 H, m), 1.57
Butyllithium (1.6 M in hexanes; 1.25 cm3, 2.00 mmol) was
added to a solution of iodide 27 (500 mg, 1.91 mmol) in THF
(5 cm3) at Ϫ78 ЊC. After stirring for 45 min, trimethyltin
chloride (1.0 M in THF; 2.00 cm3, 2.00 mmol) was added and
the mixture was stirred at Ϫ78 ЊC for a further 1 h before the
addition of methanol (3 cm3). The solution was warmed to
ambient temperature and was poured into water (5 cm3). The
mixture was extracted using diethyl ether (3 × 10 cm3) and
the combined organic layers were dried over magnesium sulfate,
1292
J. Chem. Soc., Perkin Trans. 1, 2002, 1286–1296

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(1 H, m), 1.36 [9 H, s, 3JHSn 72.1/68.8, Sn–C(CH3)3], 1.07 (1 H,
m), 0.98 and 0.97 (each 3 H, s, 2 × 7-CH3), 0.91 (1 H, m) and
0.82 (3 H, s, 1-CH3); δC (125 MHz) 149.7 (3-C), 149.6 (2-C),
140.3 and 140.4 (ipso-C), 137.4 and 137.5 (ortho-C), 128.2 and
128.3 (meta-C and para-C), 57.5 (1-C), 56.5 (7-C), 53.9 (4-C,
3JCSn 50.0), 31.3 (6-C), 31.0 [–C(CH3)3], 27.9 [–C(CH3)3], 24.3
(5-C), 20.1 and 19.9 (9-C and 10-C) and 15.6 (8-C); m/z (EI) 466
(Mϩ, 10%), 409 (100), 381 (10), 275 (12) and 197 (34).
(2 H, m), 1.6, 1.46, 1.34 and 0.98 (each 1 H, m), 0.83, 0.78 and
0.75 (each 3 H, s, 1-CH3 and 2 × 7-CH3), 0.49 (2.34 H, s, 2JHSn
2
51.2/49.0, Sn–CH3) and 0.43 (0.66 H, s, JHSn 46.4/44.0, Sn–
CH3); δC (125 MHz) 40 141.5 (ipso-C), 141.3 (ipso-C), 136.7
(ortho-C), 128.1 and 128.3 (meta-C and para-C), 49.1 (1-C),
3
3
3
48.1 (7-C, JCSn 57.8), 45.5 (4-C, JCSn 20.0), 37.7 (6-C, JCSn
42.5), 36.9 (2-C, 1JCSn 449/428), 33.1 (3-C), 28.2 (5-C), 19.5 and
18.9 (9-C and 10-C), 16.3 (8-C) and Ϫ9.6 (Sn–CH3, 1JCSn 314);
δC (125 MHz) 43 141.5 (ipso-C), 141.3 (ipso-C), 136.7 (ortho-C),
128.1 and 128.3 (meta-C and para-C), 48.9 (1-C), 47.4 (7-C),
46.8 (4-C), 41.5 (6-C), 38.2 (2-C), 34.2 (3-C), 27.7 (5-C), 20.8
and 19.5 (9-C and 10-C), 18.2 (8-C) and Ϫ8.1 (Sn–CH3); m/z
(EI) 411 (Mϩ Ϫ 15, 3%), 349 (10), 289 (81), 197 (47), 136 (19)
and 81 (100).
Preparation of 1,7,7-trimethylbicyclo[2.2.1]hept-2-ylstannanes
general procedure: (trimethyl)[(1R,4R)-1,7,7-trimethylbicyclo-
[2.2.1]hept-2-yl]stannanes 18 and 39
Vinylstannane 35 (2.25 g, 7.52 mmol) was dissolved in 1,2-
dimethoxyethane (35 cm3) containing 4-methylbenzenesulfonyl
hydrazide (17.4 g, 93.3 mmol). The mixture was heated under
reflux and sodium acetate (15.4 g, 0.19 mol) in water (20 cm3)
was added over a period of 4 h. On completion of the addition
the mixture was heated under reflux for a further 1 h before
being cooled and concentrated under reduced pressure. The
residue was taken up in saturated aqueous ammonium chloride
(50 cm3) and was extracted using dichloromethane (3 × 30 cm3).
The combined organic layers were dried over magnesium
sulfate, filtered and concentrated under reduced pressure. The
residue was dissolved in petrol (10 cm3) and passed through
a plug of silica gel using petrol as eluent. The organic phase was
concentrated. Preparative HPLC of the resulting mixture using
hexane as eluent afforded an inseparable mixture of the
stannanes 18 and 39 (15 : 85) (1.81 g, 80%) as a colourless oil,
[α]D ϩ2.1 (c 0.76, in CHCl3) (Found: Mϩ, 302.1059. C13H26Sn
requires M, 302.1055); νmax/cmϪ1 2949, 1459, 1386 and 763; δH
(500 MHz) 2.03 (1 H, m, 4-H), 1.75 and 1.69 (each 1 H, m), 1.55
(2 H, m), 1.24 (2 H, m), 1.12 (1 H, m), 0.91 (0.45 H, s, 1-CH3),
0.88 (5.10 H, s, 2 × 7-CH3), 0.86 (0.90 H, s, 2 × 7-CH3), 0.84
Dimethyl(phenyl)[(1R,4R)-1,7,7-trimethylbicyclo[2.2.1]hept-
2-yl]stannanes 41 and 44
Following the above procedure, vinylstannane 37 (2.35 g, 6.51
mmol) gave, after preparative HPLC using hexane as the eluent,
an inseparable mixture of the title compounds 41 and 44
(78 : 22) (2.27 g, 97%) as a colourless oil, [α]D ϩ6.2 (c 0.92 in
CHCl3) (Found: Mϩ Ϫ CH3, 349.0969. C17H25Sn requires M,
349.0977); νmax/cmϪ1 3062, 2983, 2949, 2926, 2873, 1480, 1459,
1428, 1386, 1075 and 745; δH (500 MHz) 7.24 (2 H, m, Ar–H),
7.06 (3 H, m, Ar–H), 1.83 (1 H, m, 4-H), 1.49, 1.32 and 1.04
(each 2 H, m), 0.80 (1 H, m), 0.62 (6 H, s, 2 × 7-CH3), 0.57 (3 H,
s, 1-CH3), 0.08 (3 H, s, 2JHSn 51.4/48.4, Sn–CH3) and 0.05 (3 H,
2
s, JHSn 50.8/48.6, Sn–CH3); δC (125 MHz) 41 142.5 (ipso-C),
2
135.6 (ortho-C, JCSn 28.1), 127.5 (meta-C and para-C), 48.5
(1-C), 47.4 (7-C, 3JCSn 52), 45.2 (4-C), 36.8 (6-C, 3JCSn 46.6), 35.5
(2-C, 1JCSn 437, 412), 32.4 (3-C), 27.8 (5-C), 19.0 and 18.4 (9-C
1
and 10-C), 15.6 (8-C) and Ϫ9.8 (Sn–CH3, JCSn 300, 310) and
1
Ϫ10.3 (Sn–CH3, JCSn 318, 305); δC (125 MHz) 44 142.5 (ipso-
2
C), 135.6 (ortho-C, 2JCSn 28.1), 127.5 (meta-C and para-C), 48.3
(1-C), 46.8 (7-C), 46.4 (4-C), 41.0 (6-C), 37.6 (2-C), 33.6 (3-C),
27.3 (5-C), 20.2 and 19.1 (9-C and 10-C), 17.3 (8-C) and Ϫ8.1
and Ϫ9.6 (2 × Sn–CH3); m/z (EI) 349 (Mϩ Ϫ 15, 9%), 227 (88),
197 (22), 136 (66) and 81 (100).
(2.55 H, s, 1-CH3), 0.09 [7.65 H, s, JHSn 50.4/48.2, Sn–(CH3)3]
and 0.05 [1.35 H, s, Sn–(CH3)3]; δC (125 MHz) 39 49.0 (1-C),
3
3
3
48.0 (7-C, JCSn 48.8), 45.7 (4-C, JCSn 18.2), 36.8 (6-C, JCSn
41.9), 35.1 (2-C, 1JCSn 426/408), 32.9 (3-C), 28.5 (5-C), 19.5 and
18.8 (9-C and 10-C), 16.2 (8-C) and Ϫ9.4 (Sn–CH3, JCSn 305/
1
289); δC (125 MHz) 18 48.8 (1-C), 47.1 (7-C), 45.8 (4-C), 41.8
(6-C), 37.9 (2-C), 34.0 (3-C), 27.8 (5-C), 20.6 and 19.8 (9-C and
10-C), 17.5 (8-C) and Ϫ8.3 (Sn–CH3); m/z (EI) 287 (Mϩ Ϫ 15,
6%), 163 (12), 136 (16), 84 (80) and 49 (100).
tert-Butyl(diphenyl)[(1R,4R)-1,7,7-trimethylbicyclo[2.2.1]hept-
2-yl]stannanes 42 and 45
Methyllithium (1.0 M in THF–cumene; 0.93 cm3, 0.93 mmol)
was added to a solution of the endo-tin chloride 46 (100 mg,
0.31 mmol) in THF–diethyl ether (1 : 1) (2 cm3) at 0 ЊC. The
mixture was warmed to ambient temperature and stirred for 2.5
h before being cooled to 0 ЊC and quenched by the addition of
water (1 cm3). The mixture was extracted using diethyl ether
(3 × 5 cm3) and the combined organic layers were dried over
magnesium sulfate, filtered and concentrated under reduced
pressure to afford the stannane 39 (79 mg, 84%) as a colourless
oil, [α]D ϩ13.4 (c 1.58 in CHCl3) [lit.14 [α]D ϩ20.6 (c 2.54 in
Following the above procedure, which was repeated seven times,
vinylstannane 38 (600 mg, 1.3 mmol) afforded an inseparable
mixture of the title compounds 42 and 45 (82 : 18) after prepar-
ative HPLC using hexane as eluent (402 mg, 67%) as a colour-
less oil, [α]D ϩ4.5 (c 1.72 in CHCl3) (Found: Mϩ Ϫ C(CH3)3,
411.1138. C22H27Sn requires M, 411.1134); νmax/cmϪ1 3063,
2950, 2928, 2872, 2844, 1480, 1464, 1427, 1365 and 1071;
δH (500 MHz) 7.33–7.64 (10 H, m, Ar–H), 2.24 (1 H, m, 4-H),
1.28–1.74 (6 H, m), 1.31 [7.4 H, s, 3JHSn 66.9/63.9, Sn–C(CH3)3],
3
1.26 [1.6 H, s, JHSn 65.5/62.6, Sn–C(CH3)3], 0.88 (1H, m) and
3
0.95, 0.875 and 0.865 (each 3 H, s); δC (125 MHz) 42 141.3 (ipso-
CHCl3)]; δC (125 MHz) 49.0 (1-C), 48.0 (7-C, JCSn 48.8), 45.7
1
(4-C, 3JCSn 18.2), 36.8 (6-C, 3JCSn 41.9), 35.1 (2-C, 1JCSn 426/408),
C, JCSn 375/360), 137.7 (ortho-C), 128.0 (meta-C and para-C),
3
3
49.0 (1-C), 48.0 (7-C, JCSn 53.4), 45.4 (4-C, JCSn 16.2), 38.04
32.9 (3-C), 28.5 (5-C), 19.5 and 18.8 (9-C and 10-C), 16.2 (8-C)
3
1
1
(6-C, JCSn 31.0), 38.0 (2-C, JCSn 368/361), 33.5 (3-C), 31.0
[Sn–C(CH3)3], 28.2 (5-C), 19.7 [Sn–C(CH3)3], 19.7 and 18.9
(9-C and 10-C) and 16.7 (8-C); m/z (EI) 411 (Mϩ Ϫ 57, 10%),
197 (25), 137 (27), 95 (32) and 81 (100).
and Ϫ9.4 [Sn–(CH3)3, JCSn 305/289]. All other data were
consistent with the material provided by the previous synthetic
route.
Methyl(diphenyl)[(1R,4R)-1,7,7-trimethylbicyclo[2.2.1]hept-
2-yl]stannanes 40 and 43
(Dimethyl)[(1R,2S,4R)-1,7,7-trimethylbicyclo[2.2.1]hept-2-yl]-
tin chloride 46
Vinylstannane 36 (1.32 g, 3.12 mmol) was subjected twice to the
conditions outlined in the general procedure to afford an
inseparable mixture of the title compounds 40 and 43 (78 : 22)
after preparative HPLC using hexane as the eluent (1.18 g,
89%) as a white oil, [α]D ϩ10.7 (c 1.54 in CHCl3) (Found: Mϩ Ϫ
CH3, 411.1142. C22H27Sn requires M, 411.1134); νmax/cmϪ1
3063, 2948, 1480, 1428 and 1074; δH (500 MHz) 7.45 (4 H, m,
Ar–H), 7.26 (6 H, m, Ar–H), 2.2 and 2.1 (each 1 H, m), 1.69
Tin() chloride (1.0 M in dichloromethane; 6.0 cm3, 6.0 mmol)
was added to a solution of stannanes 39–18 (1.80 g, 6.0 mmol;
39–18 = 85 : 15) in dichloromethane (6 cm3) at 0 ЊC. The mixture
was stirred at 0 ЊC for 45 min before being concentrated under
reduced pressure. Methyltin trichloride was then removed by
sublimation by heating the residue to 60 ЊC under reduced pres-
sure (1 mmHg). The remaining brown solid was crystallised
J. Chem. Soc., Perkin Trans. 1, 2002, 1286–1296
1293

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from hot hexane to afford the tin chloride 46 and its exo-isomer
(85 : 15) (1.47 g, 76%) as a cream solid, mp 54–57 ЊC; [α]D ϩ3.6
(c 0.74 in CHCl3). This mixture was repeatedly recrystallised
from hexane to yield the tin chloride 46 (786 mg, 54%) as a
white solid, mp 68–70 ЊC (lit.14 mp 70–71 ЊC); [α]D ϩ19.2 (c 1.32
stannanes 40 and 43 (201 mg, 0.47 mmol) in dichloromethane
(3 cm3) and the mixture was stirred at ambient temperature for
20 min. The solution was concentrated under reduced pressure.
The residue was distilled under reduced pressure to remove
iodobenzene (bp 23–25 ЊC, 1 mmHg) leaving the title compound
49 (223 mg, >99%) as a pale yellow oil, used without further
purification; νmax/cmϪ1 2981, 2950, 2873, 1479, 1458, 1428,
1388, 1072 and 751; δH 7.52 (2 H, m, Ar–H), 7.30 (3 H, m,
Ar–H), 2.17 (1 H, m, 4-H), 1.83–1.04 (7 H, m, 2-H, 3-H2, 5-H2
and 6-H2), 1.01 (3 H, s, Sn–CH3) and 0.81 (9 H, m, 2 × 7-CH3
and 1-CH3); δC 135.6, 129.4, 128.6, 45.3, 37.6, 33.2, 27.9, 19.4,
18.6, 16.2 and Ϫ2.0; m/z (CI) 416 (Mϩ ϩ 18 Ϫ 77, 100%), 366
(35) and 137 (65).
in CHCl3) [lit.14 [α]D ϩ20.5 (c 3.61 in CHCl3)] (Found: Mϩ
Ϫ
CH3, 307.0275. C11H20Sn requires M, 307.0275); νmax/cmϪ1
2976, 2952, 2929, 2874, 1459, 1450, 1387, 1095, 779 and 759;
δH 2.22 and 2.04 (each 1 H, m), 1.83 (2 H, m), 1.71, 1.55, 1.28
and 1.1 (each 1 H, m), 0.98 (3 H, s, 1-CH3), 0.93 and 0.92 (each
2
3 H, s, 2 × 7-CH3) and 0.70 [6 H, s, JHSn 49.7, Sn–(CH3)2];
δC (125 MHz) 49.1 (1-C), 48.3 (7-C), 45.5 (4-C, 3JCSn 23.2), 44.1
3
(2-C), 37.9 (6-C, JCSn 57.4), 32.0 (3-C), 28.2 (5-C), 19.4 and
18.7 (9-C and 10-C), 16.2 (8-C) and Ϫ0.36 and Ϫ1.26 (2 × Sn–
CH3); m/z (EI) 307 (Mϩ, 10%), 287 (36), 253 (19), 185 (10),
137 (30) and 81 (100).
Methyl(phenyl)[(1R,4R)-1,7,7-trimethylbicyclo[2.2.1]hept-2-en-
2-yl][(1R,2RS,4R)-1,7,7-trimethylbicyclo[2.2.1]hept-2-yl]-
stannane 50
Butyllithium (1.6 M in hexanes; 3.2 cm3, 5.09 mmol) was added
to a solution of vinyl iodide 27 (1.21 g, 4.63 mmol) in THF
(5 cm3) at Ϫ78 ЊC and the mixture was stirred for 1 h. The tin
iodide 49 (2.20 g, 4.63 mmol) dissolved in THF (5 cm3) was
added via cannula and the solution was stirred at Ϫ78 ЊC for 1 h
before the addition of methanol (5 cm3). The mixture was
warmed to ambient temperature and was concentrated under
reduced pressure. Chromatography of the residue using petrol–
triethylamine (100 : 1) as eluent afforded the title compound 50
(1.33 g, 60%) as a mixture of four diastereoisomers, [α]D Ϫ15.9
(c 0.54 in CHCl3) (Found: Mϩ Ϫ C10H17, 347.0822. C17H23Sn
requires M, 347.0821); νmax/cmϪ1 3062, 3046, 2984, 2949, 2871,
1459, 1428, 1384, 1290 and 1073; δH 7.16–7.52 (5 H, m, Ar–H),
6.21 (1 H, d, J 2.9, 3Ј-H), 2.25 (1 H, t, J 3.3, 4Ј-H), 0.60–2.12
(12 H, m), 0.95, 0.81, 0.78, 0.76, 0.69 and 0.67 (each 3 H, s)
(Methyl)[(1R,2S,4R)-1,7,7-trimethylbicyclo[2.2.1]hept-2-yl]tin
dichloride 47
A solution of tin chloride 46 (100 mg, 0.31 mmol) in dichloro-
methane (0.31 cm3) was heated under reflux with tin() chloride
(1.0 M in dichloromethane; 0.31 cm3, 0.31 mmol) for 24 h. The
mixture was concentrated under reduced pressure and the
methyltin trichloride removed by sublimation on heating to
60 ЊC under reduced pressure (1 mmHg). The residue was taken
up in dichloromethane–carbon tetrachloride (2 cm3) (1 : 1)
before being treated with decolourising charcoal (20 mg). The
mixture was filtered, the filtrate was concentrated and the
residue was recrystallised from hexane to afford the tin
dichloride 47 (92 mg, 87%) as a white solid, mp 84–86 ЊC (lit.14
mp 85–86 ЊC); [α]D ϩ11.4 (c 1.30 in CHCl3) [lit.14 [α]D ϩ13.8
(c 5.81 in CHCl3)] (Found: Mϩ ϩ NH4, 360.0312. C11H24Cl2-
NSn requires M, 360.0307); νmax/cmϪ1 2956, 2880, 1460, 1388,
1105 and 770; δH 2.49–0.99 (8 H, overlapping m, 2-H, 3-H2, 4-
H, 5-H2 and 6-H2), 1.12 (3 H, s, 2JHSn 56.2/53.7, Sn–CH3), 0.96
(3 H, s, 1-CH3) and 0.84 (6 H, s, 2 × 7-CH3); δC (125 MHz) 54.2
(2-C, 1JCSn 545/521), 49.5 (1-C), 48.6 (7-C, 3JCSn 93.9), 45.2 (4-C,
2
and 0.34 (3 H, s, JHSn 49.6, Sn–CH3); δC 147.4, 147.3,
142.7, 136.4, 127.9, 127.8, 57.3, 56.3, 53.7, 49.0, 48.0, 45.5,
37.1, 36.3, 33.4, 31.3, 28.4, 24.3, 19.8, 19.5, 18.8, 16.2, 15.3 and
Ϫ9.3; m/z (EI) 467 (Mϩ Ϫ 17, 65%), 347 (Mϩ Ϫ 137, 80)
and 197 (29).
3
2
3JCSn 29.1), 38.9 (6-C, JCSn 72.9), 31.2 (3-C, JCSn 13.2), 27.8
(5-C), 19.4 and 18.7 (9-C and 10-C), 16.2 (8-C) and 7.5 (Sn–
CH3, 1JCSn 360/344); m/z (CI) 360 (Mϩ ϩ 18, 75%), 326 (25), 154
(27), 137 (62) and 102 (100).
Methyl(phenyl)bis[(1R,2S,4R)-1,7,7-trimethylbicyclo[2.2.1]-
hept-2-yl]stannane 51
The stannane 50 (1.33 g, 2.75 mmol) was dissolved in 1,2-
dimethoxyethane (45 cm3) containing 4-methylbenzenesulfonyl
hydrazide (6.35 g, 34.4 mmol) and the mixture was heated
under reflux. Anhydrous sodium acetate (5.64 g, 68.8 mmol)
dissolved in water (20 cm3) was added dropwise over a period of
4 h. On completion of addition the mixture was heated under
reflux for a further 1 h before being cooled and poured into
saturated aqueous ammonium chloride (50 cm3). The mixture
was extracted using dichloromethane (3 × 75 cm3) and the
organic layers were dried over magnesium sulfate, filtered and
concentrated under reduced pressure. Chromatography of the
residue through a small silica plug using petrol as eluent,
followed by preparative HPLC using hexane as eluent, afforded
the product 51 together with minor exo-diastereoisomers (1.24
g, 93%). Repeated recrystallisation using acetone yielded the
title compound 51 (534 mg, 63%) as white crystals, mp 99–100
ЊC; [α]D ϩ23.6 (c 1.07 in CHCl3) (Found: Mϩ Ϫ CH3, 471.2064.
C26H39Sn requires M, 471.2073); νmax/cmϪ1 2982, 2948, 2928,
2872, 1459 and 1386; δH 7.28–7.64 (5 H, m, Ar–H), 2.18 (1 H, tt,
J 11.5, 5.7, 4-Ha), 2.04 (1 H, tt, J 12.4, 3.7, 4-Hb), 1.90–1.10
(14 H, m), 0.93 and 0.89 (each 6 H, s, 2 × 7-CH3), 0.91 and 0.77
Diphenylbis[(1R,4R)-1,7,7-trimethylbicyclo[2.2.1]hept-2-en-
2-yl]stannane 48
Butyllithium (1.9 M in hexanes; 1.04 cm3, 1.97 mmol) was
added to a solution of vinyl iodide 27 (505 mg, 1.93 mmol) in
THF (2 cm3) at Ϫ78 ЊC. The mixture was stirred for 1 h before
the addition of dichloro(diphenyl)stannane 31 (331 mg, 0.96
mmol) in THF–diethyl ether (1 : 1) (4 cm3) via cannula. The
solution was stirred for 1 h before the addition of methanol
(3 cm3). The solution was washed with water (3 × 5 cm3) and the
organic layer was dried over magnesium sulfate, filtered and
concentrated under reduced pressure. Chromatography of the
residue using petrol–triethylamine (100 : 1) as eluent afforded
the title compound 48 (220 mg, 42%) as a cream coloured oil,
[α]D Ϫ46.5 (c 0.92 in CHCl3) (Found: Mϩ, 544.2158. C32H40Sn
requires M, 544.2151); νmax/cmϪ1 3063, 2948, 2868, 1471, 1428,
1384, 1289 and 1074; δH 7.50 (10 H, m, Ar–H), 6.46 (2 H, d,
J 3.2, 3JHSn 46, 2 × 3-H), 2.42 (2 H, t, J 3.3, 2 × 4-H), 1.89 and
1.57 (each 2 H, m), 1.15–0.96 (4 H, overlapping m) and 1.05,
0.94 and 0.82 (each 6 H, s, 2 × 1-CH3 and 4 × 7-CH3); δC 149.6,
149.5, 140.1, 137.1, 128.2, 128.1, 57.5, 56.6, 53.8, 31.3, 24.2,
19.9, 19.8 and 15.3; m/z (EI) 544 (Mϩ, 10%), 467 (25), 408 (44),
211 (33), 197 (25), 84 (65) and 49 (100).
2
(each 3 H, s, 1-CH3) and 0.50 (3 H, s, JHSn 47/45, Sn–CH3);
δC (125 MHz) 143.4 (ipso-C), 136.7 (ortho-C), 127.8 and 127.7
(meta-C and para-C), 49.3 and 49.1 (2 × 1-C), 48.2 and 48.0
(2 × 7-C), 45.6 (2 × 4-C), 37.2 and 37.1 (2 × 6-C), 33.6 and 33.3
(2 × 2-C), 28.6 (2 × 3-C), 28.1 (2 × 5-C), 19.5, 19.4 and 18.8
(2 × 9-C and 2 × 10-C), 16.2 and 16.1 (2 × 8-C) and Ϫ9.0
(Sn–CH3); m/z (EI) 471 (Mϩ, 13%), 409 (4), 349 (10), 197 (42),
137 (53) and 81 (100).
(Methyl)(phenyl)[(1R,2SR,4R)-1,7,7-trimethylbicyclo[2.2.1]-
hept-2-yl]tin iodide 49
Iodine (120 mg, 0.47 mmol) was added to a solution of
1294
J. Chem. Soc., Perkin Trans. 1, 2002, 1286–1296

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(1R,4R)-1-[(Dimethylamino)methyl]-7,7-dimethylbicyclo[2.2.1]-
heptan-2-one hydrazone 53
3JHSn 47, 3-H), 2.28 [1 H, d, J 12.6, CHHN(CH3)2], 2.02 (1 H,
t, J 3.3, 4-H), 1.77 [6 H, s, N(CH3)2], 1.69 [1 H, d, J 12.4,
CHHN(CH3)2], 1.55, 1.33, 0.93 and 0.67 (each 1 H, m), 0.61
Keto-amide 5222 (1.01 g, 5.1 mmol) was dissolved in
di(ethyleneglycol)–ethanol (5 : 1) (6 cm3). Hydrazine hydrate
(0.69 cm3, 22.1 mmol) was added and the mixture was heated
under reflux for 18 h. After cooling to ambient temperature
the mixture was extracted using hexane–benzene (1 : 1) (3 ×
10 cm3). The combined organic layers were extracted using
cold hydrochloric acid (3.5 M, 3 × 10 cm3) and the combined
aqueous layers were immediately added to a mixture of 10%
aqueous sodium bicarbonate (10 cm3) and hexane–benzene
(1 : 1) (8 cm3). The pH of the mixture was adjusted to pH ≈ 14
before extraction using hexane–benzene (1 : 1) (2 × 10 cm3). The
combined organic layers were dried over magnesium sulfate,
filtered and concentrated under reduced pressure to yield the
title compound 53 (535 mg, 50%) as a brown oil, used without
further purification, [α]D ϩ5.5 (c 1.38 in CHCl3) (Found: Mϩ,
209.1893. C12H23N3 requires M, 209.1892); νmax/cmϪ1 3360,
2963, 2882, 2816, 2763, 1664, 1452, 1386, 1370, 1296, 1263,
1096, 1039, 1027, 842 and 797; δH 4.75 (2 H, br s, NH2), 2.64
[1 H, d, J 14.0, CHHN(CH3)2], 2.31 (6 H, s, 2 × NCH3), 2.29
(2 H, m), 2.08 (1 H, m), 1.9 (2 H, m), 1.74 [1 H, d, J 16.5,
CHHN(CH3)2], 1.5 and 1.21 (each 1 H, m) and 1.01 and 0.79
(each 3 H, s, 7-CH3); δC 163.7, 57.1, 55.2, 48.6, 48.3, 44.0,
32.2, 28.1, 27.3, 19.8 and 19.6; m/z (CI) 210 (Mϩ ϩ 1, 100%)
and 193 (13).
2
and 0.52 (each 3 H, s), 0.03 (3 H, s, JHSn 56.4/54.0, Sn–CH3)
2
and 0.00 (3 H, s, JHSn 55.9/53.4, Sn–CH3Ј); δC 149.2, 147.2,
144.7, 135.9, 127.6, 127.4, 65.8, 60.3, 60.0, 57.3, 53.6, 48.2, 30.9,
24.3, 20.4, 20.3, Ϫ8.9 and Ϫ9.0; m/z (EI) 390 (Mϩ Ϫ 15, 26%),
328 (14), 135 (18), 84 (43), 58 (49) and 49 (100).
N,N-Dimethyl-{(1R,4R)-2-[dimethyl(phenyl)stannyl]-7,7-
dimethylbicyclo[2.2.1]hept-2-yl}methylamine 57
The vinyl stannane 56 (173 mg, 0.5 mmol) was dissolved in 1,2-
dimethoxyethane (8 cm3) containing 4-methylbenzenesulfonyl
hydrazide (1.07 g, 5.7 mmol) and the mixture was heated under
reflux. Anhydrous sodium acetate (0.95 g, 11.6 mmol) dissolved
in water (2 cm3) was added over a period of 4 h. On completion
of addition the mixture was heated under reflux for a further
1 h before being cooled and poured into saturated aqueous
ammonium chloride (5 cm3). The mixture was extracted using
dichloromethane (3 × 10 cm3) and the organic layers were dried
over magnesium sulfate, filtered and concentrated under
reduced pressure. Chromatography of the residue through
a small silica plug using petrol as eluent afforded the title
compound 57 (15 mg, 9%) as a colourless oil (Found: Mϩ ϩ H,
408.1711. C20H34NSn requires M, 408.1712); νmax/cmϪ1 3062,
2955, 2923, 2871, 2853, 1428 and 1075; m/z (CI) 408 (Mϩ ϩ H,
6%), 306 (13), 244 (88), 224 (100) and 207 (78).
N,N-Dimethyl-[(1R,4R)-2-iodo-7,7-dimethylbicyclo[2.2.1]hept-
2-en-1-yl]methylamine 54
(Dimethyl)[(1R,2SR,4R)-1,7,7-trimethylbicyclo[2.2.1]hept-
2-yl]tin iodide 58
Hydrazone 53 (1.68 g, 8.0 mmol) was dissolved in diethyl ether
(10 cm3) containing tetramethylguanidine (3.50 cm3, 28.0
mmol). A solution of iodine (4.27 g, 16.8 mmol) in diethyl ether
(80 cm3) was added dropwise over 15 min. On completion of
addition the mixture was stirred for a further 15 min before
being washed with dilute hydrochloric acid (3.5 M, 3 × 50 cm3),
saturated aqueous sodium thiosulfate (3 × 50 cm3) and satur-
ated aqueous sodium bicarbonate (3 × 50 cm3). The pH of the
solution was adjusted to pH 14 using aqueous sodium carb-
onate solution, and the organic phase was dried over mag-
nesium sulfate, filtered and concentrated under reduced pres-
sure. Chromatography of the residue, using petrol–diethyl ether
(8 : 1) as eluent, afforded the title compound 54 (472 mg, 19%) as
a pale yellow oil, [α]D ϩ1.3 (c 0.92 in CHCl3) (Found: Mϩ,
305.0643. C12H20IN requires M, 305.0642); νmax/cmϪ1 2950,
2875, 2817, 2764, 1453, 1285, 1035 and 812; δH 6.47 (1 H, d,
J 3.4, 3-H), 2.59 and 2.44 [each 1 H, d, J 14.2, CHHN(CH3)2],
2.37 [6 H, s, N(CH3)2], 2.34 (1 H, m, 4-H), 1.88 and 1.07 (each
2 H, m) and 0.98 and 0.97 (each 3 H, s, 2 × 7-CH3); δC 144.4,
104.0, 60.3, 59.9, 56.4, 55.3, 48.4, 26.9, 24.9, 20.4 and 19.9; m/z
(CI) 306 (Mϩ ϩ 1, 100%).
A mixture of the endo- and exo-stannanes 41–44 (78 : 22)
(257 mg, 0.71 mmol) was dissolved in dichloromethane (2 cm3).
Iodine (180 mg, 0.71 mmol) was added and the mixture was
stirred at ambient temperature for 3 h before being concen-
trated under reduced pressure. Iodobenzene (bp 23–25 ЊC,
1 mmHg) was removed by distillation under reduced pressure
to afford the title compound 58 (275 mg, 94%) (endo–exo 78 : 22)
as a white solid, mp 61–63 ЊC; [α]D ϩ7.4 (c 0.9 in CHCl3);
(Found: Mϩ, 413.9867. C12H13ISn requires M, 413.9867);
νmax/cmϪ1 2973, 2948, 2926, 2872, 1458 and 752; δH 2.2–1.10
(7 H, m), 1.0 (3 H, s) and 0.94 (13 H, m); δC 49.5, 48.7, 45.3,
43.2, 37.2, 33.0, 28.1, 19.4, 18.6, 16.2 and Ϫ1.3; m/z (EI) 414
(3%), 399 (Mϩ Ϫ 15, 6), 287 (35), 247 (21), 137 (48) and 81 (100).
Dimethyl[(1R,2SR,4R)-1,7,7-trimethylbicyclo[2.2.1]hept-2-yl]-
tin hydride 59
The tin iodide 58 (1.14 g, 2.8 mmol) was taken up in ethanol
(7 cm3) and the solution cooled to 0 ЊC. Sodium borohydride
(240 mg, 5.6 mmol) was added portionwise, and the mixture
was stirred for 10 min before the addition of water (3 cm3).
The mixture was extracted using diethyl ether (3 × 10 cm3) and
the combined organic extracts were dried over magnesium
sulfate, filtered and concentrated under reduced pressure.
Chromatography of the residue using petrol–triethylamine
(100 : 1) afforded the title compound 59 (621 mg, 78%) (endo–exo
78 : 22) as a colourless oil, [α]D Ϫ7.5 (c 0.98 in hexane) (Found:
N,N-Dimethyl-{(1R,4R)-2-[dimethyl(phenyl)stannyl]-7,7-
dimethylbicyclo[2.2.1]hept-2-en-1-yl} methylamine 56
Butyllithium (1.6 M in hexanes; 0.50 cm3, 0.79 mmol) was
added to a solution of vinyl iodide 54 (220 mg, 0.72 mmol) in
THF (2 cm3) at Ϫ78 ЊC. The mixture was stirred for 1.5 h before
a solution of the phenyl(dimethyl)tin iodide 33 (280 mg, 0.79
mmol) in THF (2 cm3) was added via cannula. The reaction
mixture was stirred at Ϫ78 ЊC for 1 h before being quenched
by addition of methanol (2 cm3). The mixture was washed
with water (3 × 3 cm3) and the organic layer was dried over
magnesium sulfate, filtered and concentrated under reduced
pressure. Chromatography of the residue using petrol–diethyl
ether–triethylamine (80 : 20 : 1) gave the title compound 56
(179 mg, 66%) as a yellow oil, [α]D Ϫ48.9 (c 0.92 in CHCl3)
(Found: Mϩ Ϫ CH3, 390.1246. C19H28NSn requires M,
390.1243); νmax/cmϪ1 3061, 2984, 2949, 2871, 1454, 1428, 1029,
1010 and 747; δH 6.98–7.24 (5 H, m, Ar–H), 5.94 (1 H, d, J 3.0,
M
ϩ Ϫ H, 287.0813. C12H23Sn requires M, 287.0821); νmax/cmϪ1
2983, 2948, 2928, 2874, 1816, 1479, 1459, 1386, 1372, 1097,
761 and 707; δH (C6D6) 5.02 (0.2 H, br, Sn–H), 4.89 (0.8 H,
br, Sn–H), 1.96–0.96 (7 H, 3-H2, 4-H, 5-H2 and 6-H2), 0.77 (1 H,
m, 2-H), 0.73 (6 H, s, 2 × 7-CH3), 0.72 (3 H, s, 1-CH3) and 0.06
(6 H, m, 2 × –SnCH3); δC (C6D6) 48.6, 47.5, 45.8, 36.4, 34.2,
33.4, 28.4, 19.4, 18.5, 15.8, Ϫ12.0 and Ϫ12.5; m/z (EI) 287 (Mϩ
Ϫ 1, 49%), 273 (84), 205 (44), 136 (51) and 81 (100).
(Methyl)bis[(1R,2S,4R)-1,7,7-trimethylbicyclo[2.2.1]hept-2-yl]-
tin hydride 61
Iodine (100 mg, 0.63 mmol) was added to a solution of stannane
J. Chem. Soc., Perkin Trans. 1, 2002, 1286–1296
1295

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51 (305 mg, 0.63 mmol) in dichloromethane (2 cm3) at ambient
temperature. The solution was stirred for 20 min before being
concentrated under reduced pressure. The residue was taken up
in ethanol–diethyl ether (2 : 1) (6 cm3) and the solution cooled
to 0 ЊC. Sodium borohydride (100 mg) was added over 10 min
and the solution was stirred at 0 ЊC for 10 min then water
(2 cm3) was added. The mixture was allowed to warm to ambi-
ent temperature and was extracted using diethyl ether (3 × 5
cm3). The organic extracts were dried over magnesium sulfate,
filtered and concentrated under reduced pressure. Column
chromatography of the residue using petrol as the eluent
afforded the title compound 61 (246 mg, 96%) as a colourless oil,
[α]D ϩ39.3 (c 1.4 in hexane) (Found: Mϩ Ϫ H, 409.1917.
C21H37Sn requires M, 409.1916); νmax/cmϪ1 2982, 2948, 2928,
2873, 1801, 1478, 1459, 1386, 1371 and 738; δH (C6D6) (500
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1
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8.8 and 48.7 (2 × 1-C), 47.6 and 47.5 (2 × 7-C), 45.9 and 45.8
(2 × 4-C), 36.8 and 36.7 (2 × 6-C), 34.5 and 33.4 (2 × 2-C), 29.8
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Crystal data§ for (dimethyl)[(1R,2S,4R)-1,7,7-trimethylbicyclo-
[2.2.1]hept-2-yl]tin chloride 46
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C12H23ClSn, M = 321.46, monoclinic, a = 6.696(7), b =
10.816(8), c = 9.659(7) Å, U = 698(1) Å3, T = 296(1) K, space
group P21 (#4), Z = 2, µMo-Kα = 2.00 mmϪ1; 1406 reflections
measured, 1291 unique (Rint = 0.095); Flack parameter = 0.12
(6). The final Rω on F = 0.042 [based on 971 reflections with
I > 2.00σ(I )].
Crystal data§ for methyl(phenyl)bis[(1R,2S,4R)-1,7,7-trimethyl-
bicyclo[2.2.1]hept-2-yl]stannane 51
C27H42Sn, M = 485.32, orthorhombic, a = 10.072(2), b =
25.978(3), c = 9.617(2) Å, U = 2516.2(6)Å3, T = 296(1) K, space
group P212121 (#19), Z = 4, µCu-Kα radiation = 8.30 mmϪ1, Flack
parameter = 0.019(5), 2769 reflections measured, final Rω on
F = 0.028 [based on 2438 reflections with I > 2.00σ(I )].
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Acknowledgements
We thank the EPSRC and Eli Lilly for a CASE studentship
(to L. A. T.) and Dr C. Dell of Lilly for many helpful
discussions.
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§ CCDC reference number(s) 177844 and 177845. See http://
www.rsc.org/suppdata/p1/b2/b200317c/ for crystallographic files in .cif
or other electronic format.
1296
J. Chem. Soc., Perkin Trans. 1, 2002, 1286–1296