Bromine-magnesium exchange in gem-dibromocyclopropanes using Grignard reagents

Article abstract of DOI:10.1016/S0040-4020(02)00018-2

Reaction of gem-dibromocyclopropanes with ethylmagnesium bromide at ambient temperature leads to very high yields of allenes; when cyclopropylidene-allene ring opening is suppressed, alternative carbenic products are observed, although other reactions compete. When the reactions are carried out at -60°C, a 1-bromo-1-(bromomagnesio)-cyclopropane is formed which may be trapped by a number of electrophiles.

Full text of DOI:10.1016/S0040-4020(02)00018-2

TETRAHEDRON
Pergamon
Tetrahedron 58 12002) 1581±1593
Bromine±magnesium exchange in gem-dibromocyclopropanes
using Grignard reagents
Mark S. Baird,a,p Alexey V. Nizovtsevb and Ivan G. Bolesovb
aDepartment of Chemistry, University of Wales, Bangor, Gwynedd LL57 2UW, UK
bDepartment of Chemistry, State University of Moscow, Moscow, Russian Federation
Received 4 November 2001; accepted 3 January 2002
AbstractÐReaction of gem-dibromocyclopropanes with ethylmagnesium bromide at ambient temperature leads to very high yields of
allenes; when cyclopropylidene±allene ring opening is suppressed, alternative carbenic products are observed, although other reactions
compete. When the reactions are carried out at 2608C, a 1-bromo-1-1bromomagnesio)-cyclopropane is formed which may be trapped by a
number of electrophiles. q 2002 Elsevier Science Ltd. All rights reserved.
It has been known for nearly 40years that the reaction of a
gem-dibromocyclopropane with an alkyllithium, normally
methyllithium, leads in many cases to very high yields of
an allene, apparently derived through lithium±bromine
exchange and then loss of lithium bromide to give a cyclo-
propylidene or a related carbenoid.1 The lithiobromocyclo-
propane can be intercepted by reaction with an electrophile,
although in many cases this can only be observed at low
temperature, often below 21008C. The rearrangement of
the cyclopropylidene to allene can also be suppressed
when the latter is strained or when a favourable alternative
carbene reaction is available.2 The reaction of gem-dibromo-
cyclopropanes with metallic sodium, lithium or magnesium
1a reaction predating the use of an alkyllithium)3,4 or the
reaction of gem-dichlorocyclopropanes with magnesium in
the presence of ethyl bromide5 has also been reported to lead
to allenes, although in general yields are only moderate. The
reaction of such dibromides with methylmagnesium bro-
mide in ether has been reported to follow a quite different
course, leading to the formation of a monobromocyclopro-
pane at ambient temperature in a relatively slow reaction;6
we have recently reported that, with a number of Grignard
reagents, this hydrodebromination is strongly promoted by
titanium isopropoxide.6 Seyferth and Lambert also
reported, however, that the reaction of a gem-dibromo-
cyclopropane, 7,7-dibromobicyclo[4.1.0]heptane, with
2-propylmagnesium chloride in tetrahydrofuran 1THF) at
21038C and then at 2758C for 6 h leads to organomag-
nesium species 12 and 3) that can be trapped effectively at
low temperature by reaction with acid, again giving
the monobromides or by trimethyltin chloride, giving
a single isomer, endo-7-bromo-exo-7-trimethylstannyl-
bicyclo[4.1.0]heptane. Apparently, under these conditions,
hydrogen abstraction from the solvent does not occur.7
Reaction of the same dibromide with MeMgBr in THF at
ambient temperature is reported by Seyferth and Prokai to
lead to an exothermic reaction and also to the formation of
the corresponding exo- and endo-monobromides; in this
case, the origin of the hydrogen introduced in the reaction
was shown to be the solvent.8 No products characteristic of
the formation of the cyclopropylidene 14) were observed
1Scheme 1).
We were surprised, therefore, to see the very brief report by
Scheme 1.
Keywords: bromine±magnesium exchange; gem-dibromocyclopropanes; Grignard reagent; cyclopropylidenes.
Corresponding author. Tel.: 144-1248-382-374; fax: 144-1248-370-528; e-mail: chs028@bangor.ac.uk
p
0040±4020/02/$ - see front matter q 2002 Elsevier Science Ltd. All rights reserved.
PII: S0040-4020102)00018-2

1582
M. S. Baird et al. / Tetrahedron 58 *2002) 1581±1593
Scheme 2.
Table 1. Reaction of gem-dibromocyclopropanes with ethylmagnesium bromide in THF at ambient temperature
Starting
material
Amount
1mmol)
Amount of Grignard
1mol equiv.)
Time of addition
1min)
Time of stirring
1min)
Products 1by GLC)
Isolated yield
1%)
5
6
7
5a
3
3
1.3
1.5
9
7
7
0
3014
86
97
Trace
Trace
±
±
303
10
99
a
101.7
101.3
101.3
3
102.0
3
101.7
Trace
3±0
3±0
96
5b
5c
5d
4
5
±
96
±
2
0
30
99
7
3±0 92 10
98
±
2.03
±
±
93
4
6±0
5e
1.7
302
94
2
±
b
12
Tra6c0e
95
1
91
a
Less than 0.5% by GLC. If the Grignard reagent was prepared from 98% pure magnesium 1rather than 99.98% pure as in all other experiments), 2% 17a) was
obtained by GLC under the same conditions.
The reactions in this table were carried out using freshly distilled THF. When this experiment was carried out using THF that had been standing far one week
without excluding air and light the amount of monobromides 17e) was 17% and allene 16e) 79%.
b
Table 2. Reaction of 15a) with different Grignard reagents in THF at ambient temperature
1
Products by GLC 1by H NMR)
Grignard
Amount of Grignard
1equiv.)
Time of
reaction
Ratio 17a) trans/cisa
by 1H NMR
7a
5
a
6a
EtMgBr
1.3
1.5
1.7
1.5
30min
30min
30 min
30min
16
14 117)
3 13)
± 10)
±
86 183)
97 197)
100 1100)
81
Trace b
Trace b
Traceb
18
±
±
±
EtMgClc
t-BuMgCl
1.74:1
min
2.030 33
48
±
1 h
24 h
30 min
30min
4 h
19
23
50±
55 156)
1 10)
Traceb
Traceb
Traceb
Traceb
2
12 114)
± 10)
16
28 130)
98 1100)
82 d
1.41:1
±
±
±
±
i-PrMgBr
PhCH2MgBr
1.5
1.5
13 133)
85d 167)
d
min
2.030 11
1.5
84
24 h
8 115)
92
75
64 191)
87
43
87d 185)
1
2
3 13)
11
51
68 160)
±
±
PhMgBr
30min
7 h
24 h
30min
4 h
24 h
7
±
1.14:1
±
±
1.20:1
1016)
2
4
6 15)
MeMgClc
1.5
26 135)
a
Relative to the phenyl substituent.
Less than 0.5% by GLC data.
From Aldrich.
b
c
d
Peak of 16a) together with benzyl bromide.

M. S. Baird et al. / Tetrahedron 58 *2002) 1581±1593
1583
Inoue et al. that the reaction of 1,1-dibromo-2-hexylcyclo-
propane with butylmagnesium bromide in THF, apparently
at 08C leads ef®ciently to 1,2-nonadiene, although no
reaction time is given, suggesting the intermediacy of
the corresponding cyclopropylidene.9 We have therefore
re-examined the reaction of dibromocyclopropanes with
Grignard reagents in THF.
mechanism for this reaction may involve initial magnesium
bromine exchange, followed by loss of magnesium bromide
to give the corresponding cyclopropylidene 1or a related
carbenoid) and rearrangement 1Scheme 3).
The reaction of gem-dibromocyclopropanes with Grignard
reagents was rather dependent on the exact nature of these.
Thus reaction of 15a) with ethylmagnesium chloride in THF
proceeded just as quickly as that with ethylmagnesium
bromide, but was considerably less selective 1Table 2).
The formation of allene 16a) was also successful when
15a) was treated with prop-2-yl magnesium bromide in
THF. Reaction with benzylmagnesium bromide also led to
allene as the only major product, although it occurred slowly
and required a large excess of the Grignard reagent 1see
Table 2). The reaction with t-butylmagnesium chloride did
give allene, though not in such high yield as with the other
Grignard reagents; indeed the major product was the mono-
bromide 17a). However, no reaction occurred when 15a) was
treated with phenyl magnesium bromide in THF. Unfortu-
nately, 1,1-dichloro-2-methyl-2-phenylcyclopropane did
not react with either ethyl magnesium bromide or t-butyl-
magnesium chloride in THF and only about 7% allene
formation occurred when it was treated with prop-2-yl-
magnesium bromide for 18 h at 208C.
Reaction of a number of gem-dibromocyclopropanes with
ethylmagnesium bromide in THF at 220to 20 8C does
indeed lead rapidly and ef®ciently to the corresponding
allene 1Tables 1±3). Given the practical advantages of
preparing a Grignard reagent rather than an organolithium,
we believe this method may offer signi®cant bene®ts in
allene synthesis. In a typical experiment, 1.3±2.0mol
equiv. of ethylmagnesium bromide in THF and 1.0mol
equiv. of dibromocyclopropane were stirred in dry THF
under nitrogen for 30min±1 h at room temperature.
Aqueous work up gave the corresponding allene in 91±
96% yield after puri®cation 1Scheme 2).
The results of these reactions are summarised in Table 1. It
can be seen that an excess of the Grignard reagent was
required in each case but that the allenes 16) were produced
in each case with no more than 2% of the corresponding
monobromide.
Reaction with 1.5 mol equiv. of methylmagnesium chloride
in THF at ambient temperature led to incomplete reaction.
After 8 h, 32% of the starting material remained and a
By comparison with the reaction of gem-dibromocyclopro-
panes with methyllithium described earlier, a reasonable
Table 3. Reactions of 11) with Grignard reagents in THF
Conditions
Products 1by GLC and GC/MS data)
1
4
6
±
11112
13a
14b
20
2
1516
±
MeMgCl, 3 mol equiv.,
24 h, rt, RˆMe, EˆH,D
EtMgBr, 2 mol equiv.,
30min, rt, R ˆEt, EˆH,D
i-PrMgBr, 2 mol equiv.,
30min, rt, R ˆi-Pr, EˆH
4
9
23 exo/endo 3.0:1
66 exo/endo 3.8:1
23 exo/endo 3.9:1
45 exo:endo 1:2.0
Trace
12
±
55
1
6 exo:endo1:1.9
a
Isomers 113) were characterized only by MS and NMR of the mixture. The stereochemical assignment was made on the basis of relative retention times.10
Compound 114) was one peak by GLC but it is not clear whether only one stereoisomer is present and, if so, which it is.
b
Scheme 3.

1584
M. S. Baird et al. / Tetrahedron 58 *2002) 1581±1593
mixture of 63% allene and 3% monobromide was
observed by GLC; after 24 h, the yield of allene had
increased to 68%. The reaction of the dibromide 11) with
3 mol equiv. of methyl magnesium chloride in THF is
described later.
differences in product ratio. In particular, the very high
proportion of carbene insertion products 111) and 112) in
the reaction with i-PrMgBr may be of value. The detailed
explanation of these differences would require additional
work.
The reaction of 7,7-dibromobicyclo[4.1.0]heptane 11) with
methyllithium represents a classical example of a process in
which allene formation from an intermediate cyclopropyl-
idene is suppressed and alternative processes such as inter-
and intramolecular insertion of the carbene into C±H bonds
and formal dimerisation are observed.1 It was of interest
therefore to examine the corresponding reaction of 11)
with ethylmagnesium bromide; this led, after aqueous
work up, to a complex mixture including 111)±116) 1Rˆ
Et, EˆH). The stereochemistry of 115) was not established.
The tricycles 111) and 112) were also observed in the corre-
sponding reaction of 11) with methyllithium, as was the
7-bromo-7-methyl- analogue 114, RˆMe); however,
products 113, RˆEt, EˆH) and 115, RˆEt, EˆH) appear
to derive by reaction of the cyclopropylidene 14) with the
excess of ethylmagnesium bromide to give 113, RˆEt,
EˆMgBr); this in turn is either quenched on work up or
reacts with a second molecule of the carbene 14) to give
115, RˆEt, EˆMgBr), and is in turn quenched on work
up. In agreement, D2O quenching led to the appropriate
deuterated products. The requirement for an excess of
Grignard reagent for complete reaction may result in such
trapping of the carbene 1carbenoid) whenever the latter has
no favourable intramolecular process available.
The reaction of 15a) with EtMgBr in THF was then carried
out at a range of temperatures; the results are given in Table 4.
This clearly shows that the reaction occurred relatively
quickly even at 2808C and that when the reactions were
carried out and worked up at 2608C or below with a proton
source, the major product was a mixture of stereoisomeric
monobromides; the ratio of this mixture changed with tempera-
ture. Quenching with MeOD led to essentially complete incor-
poration of deuterium at C-1 of the cyclopropane.
The results in Table 4, and the incorporation of deuterium
suggested that at low temperature an organomagnesium
species was obtained that might be expected to be trapped
by added electrophiles 1Scheme 4).
The results of such trapping experiments are shown in Table
5; in most cases with 15b), the major product was the mono-
bromide and did not incorporate the electrophile; however,
deuteration was ef®cient and trapping with iodine or carbon
dioxide occurred in about 45% yield. Reaction with the
dibromide 15c) was more ef®cient; in particular with carbon
dioxide, the acid 110c, EˆCOOH) was obtained as a
mixture of isomers in 94% yield. Acids of type 110) have
previously been obtained from the dibromocyclopropane by
reaction with an alkyllithium at low temperature followed
by quenching with carbon dioxide,11 and by other routes.12
The results in Table 3 suggest that the reactions of the
dibromide 11) with simple Grignard reagents follow a
common pattern; however, there are clearly signi®cant
Although trapping of the intermediate organomagnesium
Table 4. Effect of temperature on the reaction of 15a) with ethylmagnesium bromide in THF
Temperature, 8C
Time of stirring, 1min)
Products 1by GLC)
Ratio 17a) trans/cisa by 1H
NMR
5
a
7a
6a
T4r7ac2e8030
26 26030
2601 h
22 25030
13 24030
127723030
50
70
1:1.1
,1
1.2:1
1.1:1
b
26
:15
22
2.8:1
99
69
1
b
b
68
61
10
1
2.0
3.9:1
±
22030
±
Work up was carried out by adding methanol at the reaction temperature.
Relative to the phenyl substituent.
Reaction mixture was worked up with CH3OD to give completely deuterated monobromides.
a
b
Scheme 4.

M. S. Baird et al. / Tetrahedron 58 *2002) 1581±1593
Table 5. Trapping of 1-bromomagnesio-1-bromocyclopropanes with electrophiles
1585
Starting
material
EtMgBr
1mol equiv.)
Electrophile
Mol
equiv.
Temperature
18C)
Time
1min)
Temperature 18C)/
quenching agent
Product
Yield
1%)
a
a
a
a
5b
5b
5b
5b
5b
5b
5b
5b
5b
5a
5c
5c
5c
5e
5e
5e
3
3
3
3
3
3
3
3
3
4
4
4
4
3j
3j
3j
Allyl bromide
ClSiMe3
ClCO2Me
CH3COCl
MeOD
1CH3)2CO
1CD3)2CO
Iodine
CO2
MeOD
ClSiMe3
MeOH
CO2
5
5
5
5
18
7
, H
260030
26060
2O
260, MeOH
6b
7b
6b
, MeOH260060
, MeOH260030
26,0H±
, H
, H
, H
, H
7bb
7bc
7bd
7be
0
2O
2O
2O
2O
2O/HCl
2O
2O
95
96
98
47f
46
260030
260030
260030
280060
26,0H±
260060
26,0H±
280060
27,0H±
7
10
40
7
7
5
60
7
5
60
10b, EˆI
10b, EˆCOOH
0
0
0
7ag
6c
95
a
, H
, H
2O
7ch
97
94
2O/HCl
2O
2O
10c, EˆCOOHi
MeOH
ClSiMe3
CO2
7ek
6e
97
a
, H
, H
270060
280060
2O/HCl
10e, EˆCOOHl
74
a
Only dibromocyclopropane-derived product by NMR.
b
The reaction mixture contained 96% of 17b) and 4% of 16b) by 1H NMR. Compound 17b) probably formed by reaction of bromomagnesiocyclopropane with
2-butanone, which derived from reaction of excess of EtMgBr with acetyl chloride; an alternative could involve a direct elimination of hydrogen from acetyl
chloride by bromomagnesiocyclopropane since the C±H acidity of the latter is higher than that of the former.
c
d
e
f
17b) was completely deuterated.
4-Methyl-4-hydroxy-2-pentanone was isolated as a by-product 180%, calculated on amount of 11b)).
17b) was completely deuterated, 4-methyl-4-hydroxy-2-pentanone-d11 was isolated as a by-product 179%, calculated on amount of 11b)).
Yield after crystallization. The reaction mixture contained 75% 1,1-diphenyl-2-bromo-2-iodo-cyclopropane and 25% of 3,3-diphenyl-1,2-diiodoprop-2-ene
1separate addition of iodine in chloroform to the allene at 208C led to this di-iodide in 97% yield. The di-iodide in turn is converted ef®ciently into the
corresponding 2-iodo-1-acetoxypropene by reaction with sodium acetate and this is readily hydrolysed to 3,3-diphenyl-2-iodoprop-2-en-1-ol with sodium
hydroxide in aqueous ethanol36), the product of addition of iodine to 1,1-diphenylpropa-1,2-diene, by H NMR.
17a) was completely deuterated, ratio trans/cis 1.13:1.
trans/cis 1.25:1 by GLC.
Isolated as methyl esters after treatment with diazomethane, trans/cis 1.4:1 by H NMR.
i-PrMgBr used instead of EtMgBr.
trans/cis 1:1 by GLC.
Isolated as methyl esters after treatment with diazomethane, trans/cis 1:1 by H NMR.
1
g
h
i
1
j
k
l
1
species was very ef®cient with a source of H1, D1, or on
quenching with carbon dioxide, and moderately ef®cient
with a source of I1, trapping with other electrophiles was
not generally successful. This contrasts the trapping of
1-lithio-1-bromocyclopropanes with allylic halides,13 tri-
alkylchlorosilanes,14 acetone,15 acid chlorides,16 or esters,17
a number of successful examples of which are reported. It is
interesting to note that the a-bromomagnesiocyclopropane
18a), if the intermediate does have such a structure, shows
rather a unusual combination of high protophilic activity in
reactions with alcohols and with acetone and acetyl chloride
and a very low nucleophilic activity in reactions with the
same carbonyl compounds. Reactions of compound 15b)
with a Grignard reagent followed by acetone and d6-acetone
at 2608C for 30min proved to be a very effective route to
4-methyl-4-hydroxy-2-pentanone 180%) or its d11-analogue
179%), together with the 1-bromo-2,2-diphenylcyclo-
propane or 1-bromo-1-deuterio-2,2-diphenyl-cyclopropane,
respectively. It is worth noting that in a traditional synthesis
of 4-methyl-4-hydroxy-2-pentanone from acetone and
barium hydroxide, yields are about 71% after approximately
95±120h. 18 In an attempt to promote trapping of 18c) with
allyl bromide, the dibromide 15c) was treated with 4 mol
equiv. of ethylmagnesium bromide at 2608C and then
with 4.25 mol equiv. of cuprous iodide followed by 8 mol
equiv. of allyl bromide. This led to a mixture of 1-ethyl-
1-allyl-2-phenyl-cyclopropane 176%) 1trans/cis 1.4:1)
together with 1,1-diethyl-2-phenylcyclo-propane 114%)
and trans-1-bromo-1-allyl-2-phenylcyclopropane 19%)
1Scheme 5).
Reaction of 15b) with 3 mol equiv. of EtMgBr at 2608C for
Scheme 5.

1586
M. S. Baird et al. / Tetrahedron 58 *2002) 1581±1593
Scheme 6.
30min 1to ensure complete reaction of 1 5b)) followed by the
addition of 2.5 mol equiv. of 15a) and stirring for a further
30min at 2608C, gave a mixture which included by H
18c), was signi®cantly increased by transformation of this
into the appropriate cuprate and 1-allyl-1-ethyl-2-phenyl-
cyclopropane was isolated in a reasonable preparative
yield.
1
NMR no 15b) and 61% 15a). In the same way, reaction of
15a) with 4 mol equiv. of EtMgBr at 2608C for 30min
following addition of 3 mol equiv. of 15b) and stirring for
further 30min at 2608C gave a mixture that contained no
15a) and 50% 15b). These results suggest that there is no
equilibrium between the magnesiobromocyclopropane and
dibromocyclopropane as has been reported in the case of the
lithiobromocyclopropanes.7
1. Experimental
Commercial reagents were used without further puri®cation
unless stated. Magnesium was 99.98% pure from Aldrich.
gem-Dibromocyclopropanes were prepared using standard
procedure from alkenes and bromoform in two phase reac-
tions and spectral data of these compounds were identical to
those described in literature. THF was distilled over sodium
wire. Petroleum ether was of boiling point 40±608C unless
stated. Reactions requiring anhydrous conditions were
performed using oven dried glassware 11608C) cooled
under a stream of dry nitrogen or argon; the experiments
were conducted under a positive atmosphere of one of these
gases. Unless stated, organic solutions were dried over
anhydrous magnesium sulphate, and evaporated at 14
mmHg; yields quoted are for puri®ed compounds and any
ratios given are calculated by comparing integrals in the 1H
NMR spectrum. New compounds were homogeneous by
GLC or TLC. GLC was conducted using a Carlo Erba
HRGC 5300 1F.I.D., on a capillary column). TLC was
performed using Aldrich silica plates coated with silica
gel 601F254). Compounds were visualised using an ultra-
violet source, by exposure to iodine vapour or by contact
with phosphomolybdic acid hydrate 12% in ethanol)
followed by heating to 1808C. Column chromatography
was conducted with Fisher Scienti®c Silica Gel 60under
medium pressure.
The reaction of 2-hexyl-1,1,2-tribromocyclopropane with
1.3 mol equiv. ethylmagnesium bromide in THF for
30min at ambient temperature led in high yield to 1,2-
debromination and the formation of 2-hexyl-1-bromocyclo-
propene 1Scheme 6).
Similar dehalogenations have been very effectively
achieved by reaction of this and related tribromides with
an alkyllithium; in this case the elimination occurs rapidly
even below ambient temperature and a second mol equiv. of
the organolithium undergoes lithium±bromine exchange to
produce a 1-lithiocyclopropene that can be trapped by a
range of electrophiles.19 Reaction of 2-hexyl-1,1,2-tri-
bromocyclopropane with 7 mol equiv. of ethyl magnesium
bromide for 3 h at ambient, followed by quenching with
trimethylsilyl chloride led, in a similar process to 1-tri-
methylsilyl-2-hexylcyclopropene by crude 1H NMR,
presumably by a magnesium±bromine exchange in the
intermediate bromocyclopropene; incomplete reaction
occurred with fewer than 7 mol equiv. of the reagent.
Given the large excess of Grignard reagent required in the
present reaction, it would seem likely that an alkyllithium
will remain the reagent of choice in such transformations.19
Melting points are uncorrected. Infrared spectra were
obtained as a solution in CHCl3 or as liquid ®lms on a
Perkin±Elmer 1600 FTIR spectrometer. Low-resolution
mass spectra were obtained on a Finnigan 8430spectro-
meter. Microanalyses were performed on a Carlo Erba
Model 1106 CHN analyser. NMR spectra were recorded
in CDCl3, unless stated, on a Bruker AC250at 250MHz
for protons, at 62.9 MHz for carbons and in the latter case
were either broad-band or gated decoupled. Previously
described compounds were characterized by comparison
with literature data using IR, 1H and 13C NMR where
these were reported; they corresponded closely to those
described except the 13C NMR data for 1,1-diphenyl-
propa-1,2-diene.21 Where no such data are given in the
literature, they are included herein.
It is important to note that no reaction was observed
between 1,1-dichlorocyclopropanes and Grignard reagents
in THF even at ambient temperature. In this context, it is
also worth noting that magnesium cyclopropylidenes can be
generated by reaction of a 1-chlorocyclopropyl sulphoxide
with Grignard reagents and that under proper conditions
these can either be trapped as monochlorides after proto-
nation, or rearrange to allenes.20
In summary, ethyl- and isopropylmagnesium bromide in
THF are convenient reagents for highly selective and
effective transformations of gem-dibromocyclopropanes
into aliphatic and non-strained alicyclic allenes. Inter-
mediate formation of 1-bromo-1-bromomagnesiocyclo-
propanes is supported by reactions with water, methanol,
methanol-d. The a-brominated cyclopropylmagnesio-
bromides proved to be rather poor nucleophiles in reactions
with allyl bromide, acetone, acetone-d6, acetyl chloride,
methyl chloroformate and TMSCl. Nevertheless, the reac-
tivity of one of the a-bromocyclopropylmagnesiobromides,
1.1. Preparation of allenes
Standard procedure. 1.0M ethylmagnesium bromide in
THF 113.0±20.0 ml, 13.0±20.0 mmol, 1.30±2.00 mol
equiv.) was added to a stirred solution of dibromocyclo-
propane 110.0 mmol) in dry THF 120 ml) under nitrogen

M. S. Baird et al. / Tetrahedron 58 *2002) 1581±1593
1587
at room temperature. Stirring was continued for 30min±1 h
when water 12 ml) was added. The organic layer was sepa-
rated, the water suspension of magnesium salt was dissolved
in a small amount of 4 M hydrochloric acid and extracted
with petroleum 12£10ml). The combined organic layers
were dried and evaporated in vacuo. The product was trea-
ted with petroleum 15 ml), ®ltered through silica 15 g),
washing the silica with petroleum and evaporated to give
allene. The product was generally pure enough to use
directly.
in THF 14.5±6.0ml, 4.5±6.0mmol, 1.50±2.00mol equiv.)
was added to a stirred solution of 1,1-dibromo-2-methyl-2-
phenylcyclopropane 1870mg, 3.0mmol) in dry THF 16 ml)
under nitrogen at room temperature. Stirring was continued
for 30min±24 h at room temperature when water 10.5 ml)
was added. The organic layer was separated, the water
suspension of magnesium salt was dissolved in a small
amount of 4 M hydrochloric acid and extracted with petro-
leum 12£5 ml). The combined organic layers were dried and
1
evaporated. The product was analysed by H NMR. The
reactions were monitored by removing samples 10.1 ml)
for GLC at 30min, 1, 2, 4, 8 and 24 h. The results of
these experiments are presented in Table 2.
1.1.1. 3-Phenylbuta-1,2-diene. 1,1-Dibromo-2-methyl-2-
phenylcyclopropane 12.90g, 10.0mmol) was treated as
above with 1.0M ethylmagnesium bromide 117.0ml,
17.0mmol, 1.70mol equiv.) adding over 9 min and stirring
for 30min to give 3-phenylbuta-1,2-diene22 11.26 g, 9.6
mmol, 96%) as a colourless oil, dC: 16.71, 76.92, 99.8,
125.71, 126.61, 128.31, 136.7, 209.0.
1.4. A study of the stability of 1-bromomagnesio-1-
bromo-2-methyl-2-phenylcyclopropane
1.0M ethylmagnesium bromide in THF 15.1 ml, 5.1 mmol,
1.70mol equiv.) was added to a stirred solution of
1,1-dibromo-2-methyl-2-phenylcyclopropane 1870mg, 3.0
mmol) in dry THF 16 ml) under nitrogen at the appropriate
temperature. Stirring was continued for 30min at that
temperature when methanol or methanol-O-d 12 ml) was
slowly added. The resulting solution was warmed to 08C
and water 10.5 ml) was added. The mixture was diluted
with petroleum to 50ml, dried, analysed by GLC and
evaporated to give an oil, which was analysed by 1H
NMR. The conditions and results of these experiments are
given in Table 4.
1.1.2. 1,1-Diphenylpropa-1,2-diene. 1,1-Dibromo-2,2-
diphenylcyclopropane 13.521 g, 10.0 mmol) was treated as
above with 1.0M ethylmagnesium bromide 113.0ml,
1.30mol equiv.) adding over 4 min and stirring for 30min
to give 1,1-diphenylpropa-1,2-diene.21 11.849 g, 9.6 mmol,
96%) as a slightly yellow liquid 1mp 4.5±58C), dC: 78.12,
127.21, 128.41, 136.3, 209.9.
1.1.3. Phenylpropa-1,2-diene. 1,1-Dibromo-2-phenylcyclo-
propane 12.760g, 10.0mmol) was treated as above with
1.0M ethylmagnesium bromide 113.0ml, 13.0mmol,
1.30mol equiv.) adding over 5 min and stirring for 30min
to give phenylpropa-1,2-diene23 11.068 g, 9.2 mmol, 92%)
as a colourless liquid.
1.5. Reactions of 1-bromomagnesio-1-bromocyclo-
propanes with electrophiles
1.5.1. 1-Bromomagnesio-1-bromo-2,2-diphenylcyclopro-
pane. 1i) With CH3OD. 1-Bromomagnesio-1-bromo-2,2-
diphenylcyclopropane was prepared as above using 1,1-
dibromo-2,2-diphenylcyclopropane 1704 mg, 2.0 mmol),
THF 14 ml) and 1.0M ethylmagnesium bromide 16 ml,
6.0mmol, 3.00mol equiv.) at 2608C. The reaction mixture
was cooled to 2808C and methanol-O-d 11 ml) was slowly
added at not above 2608C. The reaction mixture was
warmed to 08C and water 10.5 ml) was added. The resulting
solution was diluted with ether to 75 ml, dried and evapo-
rated in vacuo to give a solid, which was ®ltered through
silica 11 g) washing with petroleum to give 1,1-diphenyl-2-
bromo-2-deuteriocyclopropane 1522 mg, 1.9 mmol, 95%)
1.1.4. Cyclonona-1,2-diene. 9,9-Dibromobicyclo[6,1,0]-
nonane 12.820g, 10.0mmol) was treated as above with
1.0 M ethylmagnesium bromide 120.0 ml, 20.0 mmol,
2.0mol equiv.) adding over 4 min and stirring for 1 h to
give cyclonona-1,2-diene24 11.14 g, 9.3 mmol, 93%) as a
colourless oil.
1.1.5. Nona-1,2-diene. 1,1-Dibromo-2-hexylcyclopropane
12.840g, 10.0mmol) was treated as above with 1.0M ethyl-
magnesium bromide 117.0ml, 17.0mmol, 1.70mol equiv.)
adding over 12 min and stirring for 1 h to give nona-1,2-
diene25 11.129 g, 9.1 mmol, 91%) as a colourless liquid.
as
a
white solid 1mp 77±798C) 1Calculated for
1.2. Generation of 1-bromo-1-bromomagnesiocyclo-
propanes
C15H12BrD: C 65.71; H 5.15%. Found: C 65.8; H 4.9%),
dH: 1.85 11H, d, Jˆ6.4 Hz), 1.9011H, d, Jˆ6.4 Hz), 7.16±
7.48 110H, m); dC: 23.92, 28.1 1t, Jˆ28.6 Hz), 36.2,
126.71, 127.01, 127.81, 128.31, 128.61, 130.51,
140.7, 144.2; IR 1cm21, in CHCl3): 1599 m, 1494 s, 1446
s, 1069 m, 1014 m, 702 s.
Standard procedure. 1.0M ethylmagnesium bromide or
0.8 M isopropylmagnesium bromide in THF 19.0±
12.0 mmol, 3.00±4.00 mol equiv.) was added to a stirred
solution of the dibromocyclopropane 13.0mmol) in dry
THF 16±30ml) under nitrogen at 260^1 or 270^18C.
Stirring was continued for 30min at the same temperature
to give the solution of 1-bromomagnesio-1-bromocyclo-
propane.
1ii) With acetone. 1-Bromomagnesio-1-bromo-2,2-diphenyl-
cyclopropane was prepared as in 1i). A solution of acetone
11 ml) in dry THF 11 ml) was added at 2608C and stirring
was continued for 30min at the same temperature. The
mixture was warmed to 08C and water 11 ml) was added.
The resulting solution was diluted with ether to 50ml, dried
and evaporated to give product 1880mg), which was sepa-
rated by column chromatography on silica 140g) eluting
with 3:2 petroleum/ether to give 1-bromo-2,2-diphenyl-
1.3. Reactions of 1,1-dibromo-2-methyl-2-phenylcyclo-
propane with Grignard reagents
Standard procedure. A 1.0M solution of a Grignard reagent

1588
M. S. Baird et al. / Tetrahedron 58 *2002) 1581±1593
cyclopropane26 1522 mg, 1.91 mmol, 96%) as a white solid
1mp 77±798C) which showed dH: 1.85 11H, dd, Jˆ6.4,
5.2 Hz), 1.89 11H, dd, Jˆ7.6, 6.4 Hz), 3.78 11H, dd,
Jˆ7.6, 5.2 Hz), 7.13±7.46 110H, m); dC: 24.02, 28.51,
36.4, 126.81, 127.21, 127.81, 128.31, 128.71, 130.61,
140.8, 144.2; IR 1cm21, in CHCl3): 1598 m, 1494 s, 1445 s,
1423 m, 1314 m, 1079 m, 918 m, 703 s, 633 m, 604 m; and
4-hydroxy-4-methylpentan-2-one27 1186 mg, 1.60mmol,
1vii) With acetyl chloride. 1-Bromomagnesio-1-bromo-2,2-
diphenylcyclopropane was prepared as in 1i). Then a solu-
tion of acetyl chloride 1785 mg, 0.71 ml, 10 mmol, 5 mol
equiv.) in dry THF 11.3 ml) was added at 2608C and stirring
was continued for 30min. The reaction mixture was
warmed to 08C over 50min and methanol 11.5 ml) was
added followed after 15 min by water 10.5 ml). The
resulting solution was diluted with ether to 40ml, dried
and evaporated to give an oil, which contained only
1-bromo-2,2-diphenylcyclopropane 196%) and 1,1-
diphenylpropa-1,2-diene 14%) derived from cyclopropane
by 1H NMR.
80%) as a colourless liquid which showed IR 1cm21
,
®lm): 3442 br.s, 2974 s, 2933 m, 1702 s, 1418 m, 1408 m,
1378 s, 1364 s, 1333 m, 1217 m, 1180m, 1147 m, 915 m,
734 m.
1iii) With acetone-d6. The above experiment was repeated
except that acetone was replaced by acetone-d6 to give crude
product 1880mg), which was separated by column chroma-
tography on silica 140g) eluting with 3:2 petroleum/ether
to give 1-bromo-2,2-diphenyl-1-deuteriocyclopropane 1539
mg, 1.97 mmol, 98%) as a white solid 1mp 77±798C) with
spectral data identical to above and 4-hydroxy-4-methyl-
pentan-2-one-d11 1201 mg, 1.58 mmol, 79%) as a colourless
liquid which showed dH: 3.58 11H, broad s); dC: 28.3
1septet, Jˆ19.1 Hz), 31.3 1septet, Jˆ19.1 Hz), 53.5 1pentet,
Jˆ19.1 Hz), 68.9, 210.8; IR 1cm21, ®lm): 3452 br.s, 2229 s,
1696 s, 1384 br.s, 1257 br.s, 1204 br.s, 1153 br.s, 1096 m,
1053 s, 818 s.
1viii) With iodine. 1-Bromomagnesio-1-bromo-2,2-diphenyl-
cyclopropane was prepared as in 1i). A solution of iodine
15.076 g, 20mmol, 10mol equiv.) in dry THF 116 ml) was
added at 2608C and stirring was continued for 30min at the
same temperature. The mixture was warmed to 08C for
40min, poured into chloroform 1100ml) and washed with
sat. aq. sodium thiosulphate 140ml). The organic layer was
separated and the water layer extracted with chloroform
13£20ml). The combined organic layers were dried and
evaporated to give a solid 1783 mg), which contained 25%
3,3-diphenyl-1,2-di-iodoprop-2-ene 1given later) and 75%
1-bromo-1-iodo-2,2-diphenyl-cyclopropane by 1H NMR.
The solid was crystallized from hexane 120ml) to give
pure 1-bromo-1-iodo-2,2-diphenylcyclopropane 1376 mg,
0.94 mmol, 47%) as a white solid 1mp 156±1588C 1dec.))
1Calculated for C15H12BrI: C 45.15; H 3.03%. Found C 45.1;
H 2.9%) which shown dH: 2.52 11H, d, Jˆ7.4 Hz), 2.60
11H, d, Jˆ7.4 Hz), 7.20±7.37 16H, m), 7.49±7.57 14H,
m); dC: 25.7, 36.02, 44.4, 127.31, 127.41, 128.41,
128.51, 129.01, 129.51, 141.4, 144.3; IR 1cm21, in
CHCl3): 1492 s, 1446 s, 1057 s, 1001 m, 994 m, 706 s,
691 m, 629 m.
1iv) With trimethylchlorosilane. 1-Bromomagnesio-1-
bromo-2,2-diphenylcyclopropane was prepared as in 1i).
Then a solution of trimethylchlorosilane 11.086 g, 1.27 ml,
10mmol, 5 mol equiv.) in dry THF 10.7 ml) was added at
the same temperature and stirring was continued for 60min.
The mixture was cooled to 2808C and methanol 11.5 ml)
was slowly added at not above 2608C. It was then warmed
to 08C and water 11 ml) was added. The organic layer was
separated, the water suspension of magnesium salt was
dissolved in a small amount of 4 M hydrochloric acid and
extracted with ether 13£5 ml). The combined organic layers
were dried and evaporated to give an oil, which contained
only 1-bromo-1,1-diphenylcyclopropane derived from the
1ix) With CO2. 1-Bromomagnesio-1-bromo-2,2-diphenyl-
cyclopropane was prepared as above using 1,1-dibromo-
2,2-diphenylcyclopropane 11.056 g, 3.0 mmol), dry THF
120ml) and 1.0M ethylmagnesium bromide 19 ml, 9.0
mmol, 3.00 mol equiv.) at 2608C. The reaction mixture
was cooled to 2908C and dry CO2 was passed in for
10min 1rate 280ml/min, 2.8 l, 125 mmol, 40mol equiv.)
and stirring was continued for 60min at 2808C. The reac-
tion mixture was warmed to 08C for 100 min, poured into
chloroform 150ml) and washed with a solution of concen-
trated hydrochloric acid 120ml) in water 1100ml). The
organic layer was separated and the water layer was
extracted with chloroform 13£15 ml). The combined
organic layers were extracted with sat. aq. sodium bicarbo-
nate 13£15 ml) and the combined aqueous layers were
extracted with chloroform 110ml). Concentrated hydro-
chloric acid was added until pH 1 and the mixture was
extracted with chloroform 14£15 ml). The combined
organic layers were dried and evaporated to give 1-bromo-
2,2-diphenylcyclopropanecarboxylic acid28 1436 mg, 1.37
mmol, 46%) as white solid 1mp 179.5±1818C 1dec); lit.
mp 185±1888C) which showed dH: 2.11 11H, d, Jˆ
6.6 Hz), 2.75 11H, d, Jˆ6.6 Hz), 7.22±7.51 110H, m),
10.98 11H, br.s); dC1acetone-d6): 28.2, 39.6, 45.5, 127.8,
127.9, 129.1, 129.2, 129.4, 130.4, 141.8, 143.0, 168.9; IR
1cm21, in CHCl3): 3064 br.m, 3023 br.m, 2873 br.m, 2664
br.m, 2524 br.m, 1687 s, 1268 s, 744 s, 705 s.
1
cyclopropane, by H NMR.
1v) With allyl bromide. 1-Bromomagnesio-1-bromo-2,2-
diphenylcyclopropane was prepared as in 1i). Then a solu-
tion of allylbromide 11.210g, 0.87 ml, 10mmol, 5 mol
equiv.) in dry THF 11 ml) was added at 2608C and stirring
was continued for 30min at the same temperature. The
mixture was warmed to 08C for 40min and water 11 ml)
was added. The resulting solution was diluted with ether
to 75 ml, dried and evaporated to give an oil, which
1
contained only 1,1-diphenylpropa-1,2-diene by H NMR.
1vi) With methyl chloroformate. 1-Bromomagnesio-1-
bromo-2,2-diphenylcyclopropane was prepared as in 1i).
Then a solution of methyl chloroformate 1945 mg, 0.77
ml, 10mmol, 5 mol equiv.) in dry THF 11.2 ml) was
added at the same temperature and stirring was continued
for 60min. The mixture was warmed to 0 8C for 40min and
methanol 11.5 ml) was added. After 15 min water 10.5 ml)
was added. The resulting solution was diluted with ether to
50ml, dried and evaporated to give an oil, which by 1H
NMR contained only 1,1-diphenylpropa-1,2-diene derived
from cyclopropane.

M. S. Baird et al. / Tetrahedron 58 *2002) 1581±1593
1589
1x) With 1,1-dibromo-2-methyl-2-phenylcyclopropane.
1-Bromomagnesio-1-bromo-2,2-diphenylcyclopropane was
prepared as above using 1,1-dibromo-2,2-diphenylcyclo-
propane 1352 mg, 1.0mmol), dry THF 12 ml) and 1.0M
ethylmagnesium bromide 13 ml, 3.0mmol, 3.00mol equiv.)
at 2608C. Then a solution of 1,1-dibromo-2-methyl-2-
phenylcyclopropane 1725 mg, 2.5 mmol, 2.5 mol equiv.) in
dry THF 13 ml) was added at 2608C and stirring was con-
tinued for 30min at the same temperature. The mixture was
cooled to 2808C while methanol 11.5 ml) was slowly added
at not more than 2608C, and then warmed to 08C and water
11 ml) was added. The resulting solution was diluted with
ether to 50ml, dried and evaporated to give an oil, which
contained 1-bromo-2,2-diphenylcyclopropane 131%), 1,1-di-
bromo-2-methyl-2-phenylcyclopropane 162%) and 1-bromo-
2-methyl-2-phenyl cyclopropane 17%, trans/cis 1.13:1) by
1H NMR.
2,2-diphenylcyclopropane 150%) and 1-bromo-2-methyl-2-
phenylcyclopropane 123%, trans/cis 1.38:1) by 1H NMR.
1.5.3. 1-Bromomagnesio-1-bromo-2-phenylcyclopropane.
1i) With CH3OH. 1-Bromomagnesio-1-bromo-2-phenyl-
cyclopropane was prepared as above using 1,1-dibromo-2-
phenylcyclopropane 1828 mg, 3.0mmol), dry THF 16 ml)
and 1.0M ethylmagnesium bromide 112 ml, 12.0mmol,
4.00 mol equiv.) at 2608C. The reaction mixture was cooled
to 2808C and methanol 11 ml) was slowly added at not more
than 2608C. The mixture was warmed to 08C and water
11 ml) was added. The organic layer was separated, the
water suspension of magnesium salt was dissolved in a
small amount of 4 M hydrochloric acid and extracted with
pentane 13£10ml). The combined organic layers were dried
and evaporated in vacuo. The product was treated with pen-
tane 12 ml), ®ltered through silica 11.5 g), washing the silica
with pentane and evaporated to give 1-bromo-2-phenylcyclo-
propane29 1574 mg, 2.91 mmol, 97%, trans/cis 1.25:1 by
1.5.2. 1-Bromomagnesio-1-bromo-2-methyl-2-phenyl-
cyclopropane. 1i) With CH3OD. 1-Bromomagnesio-1-
bromo-2-methyl-2-phenylcyclopropane was prepared as
above using 1,1-dibromo-2-methyl-2-phenylcyclopropane
1870mg, 3.0mmol), dry THF 16 ml) and 1.0M ethyl-
magnesium bromide 112 ml, 12.0mmol, 4.00mol equiv.)
at 2608C. The reaction mixture was cooled to 2808C and
methanol-O-d 11 ml) was slowly added at not more than
2608C. The mixture was warmed to 08C and water 11 ml)
was added. The organic layer was separated, the water
suspension of magnesium salt was dissolved in a small
amount of 4 M hydrochloric acid and extracted with petro-
leum 13£10ml). The combined organic layers were dried
and evaporated in vacuo. The product was treated with
petroleum 12 ml), ®ltered through silica 11.5 g), washing
the silica with petroleum, and evaporated to give
1-bromo-1-deuterio-2-methyl-2-phenylcyclopropane 1604
GLC data) as a colourless liquid which showed IR 1cm21
,
®lm): 1604 m, 1499 m, 1455 m, 1261 m, 1234 m, 763 m,
696 s.
1ii) With trimethylchlorosilane. 1-Bromomagnesio-1-bromo-
2-phenylcyclopropane was prepared as in 1i). A solution of
trimethylchlorosilane 12.173 g, 2.54 ml, 20mmol, 6.67
mol equiv.) in dry THF 11.5 ml) was added at 2608C and
stirring was continued for 60min at the same temperature.
The mixture was warmed to 08C for 90min and water 13 ml)
was added. The organic layer was separated and extracted
with petroleum 13£10ml). The combined organic layers
were dried and evaporated to give oil, which contained
only 1-phenylallene by 1H NMR derived from cyclopropane.
1iii) With CO2. 1-Bromomagnesio-1-bromo-2-phenylcyclo-
propane was prepared as above using 1,1-dibromo-2-
phenylcyclopropane 1552 mg, 2.0mmol), dry THF 110ml)
and 1.0M ethylmagnesium bromide 18 ml, 8.0mmol,
4.00 mol equiv.) at 2608C. The mixture was cooled to
2908C, and dry CO2 was passed in for 10min 1rate
300ml/min, 3 l, 130mmol, 65 mol equiv.) and stirring
was continued for 60min at 2808C. The mixture was
warmed to 08C for 100 min, poured into chloroform
140ml) and washed with conc. hydrochloric acid 110ml)
in water 150ml). The organic layer was separated and the
water layer was extracted with chloroform 13£10ml). The
combined organic layers were extracted with sat. aq. sodium
bicarbonate 14£15 ml); the combined layers were washed
with chloroform 12£10ml). Concentrated hydrochloric acid
was added until pH 1 and they were extracted with chloro-
form 14£20ml). The combined organic layers were dried
and evaporated in vacuo to give an oil, which was dissolved
in ether 12 ml), treated with diazomethane until a yellow
colour persisted, dried and evaporated to give methyl
1-bromo-2-phenylcyclopropanecarboxylate30 1480mg, 1.88
mmol, 94%, trans/cis 1.4:1 by 1H NMR data) as a colourless
liquid which showed dC: 22.22, 24.02, 31.3, 33.51, 35.0,
36.81, 53.01, 53.71, 127.41, 127.61, 128.11, 128.21,
128.71, 129.41, 134.4, 135.6, 167.4, 170.5.
1
mg, 2.85 mmol, 95%, trans/cis 1.13:1 by H NMR data)
as a colourless liquid 1Calculated for C10H10BrD: C,
56.63; H, 5.70%. Found: C, 56.4; H, 5.4%) which showed
1trans isomer) dH: 1.09 11H, d, Jˆ6.4 Hz), 1.63 13H, s), 1.65
11H, d, Jˆ6.4 Hz), 7.19±7.82 15H, m); dC: 23.22, 23.91,
25.7, 30.3 1t, Jˆ29.2 Hz), 126.51, 127.01, 128.61, 144.5;
1cis isomer) dH: 1.38 11H, d, Jˆ6.5 Hz), 1.41 11H, d, Jˆ
6.5 Hz), 1.48 13H, s), 7.26±7.46 15H, m); dC: 22.02, 26.91,
27.5, 28.3 1t, Jˆ14.5 Hz), 126.81, 128.21, 129.41, 142.2;
IR 1cm21, ®lm, mixture of isomers): 3059 m, 3025 m, 2959
m, 1602 m, 1497 m, 1445 s, 1074 m, 1061 m, 1027 m, 764 s,
730m, 699 s.
1ii) With 1,1-dibromo-2,2-diphenylcyclopropane. 1-Bromo-
magnesio-1-bromo-2-methyl-2-phenylcyclopropane was pre-
pared as in 1i) above using 1,1-dibromo-2-methyl-2-
phenylcyclopropane 1290mg, 1.0mmol), dry THF 12 ml)
and 1.0M ethylmagnesium bromide 14 ml, 4.0mmol,
4.00 mol equiv.) at 260^18C. Then a solution of 1,1-
dibromo-2,2-diphenylcyclopropane 11.056 g, 3.0 mmol,
3.0mol equiv.) in dry THF 13 ml) was added at 260^18C
and stirring was continued for 30min at the same tempera-
ture. The mixture was cooled to 2808C and methanol
11.5 ml) was slowly added at not more than 2608C. The
mixture was warmed to 08C and water 10.5 ml) was
added. The resulting solution was diluted with ether to
50ml, dried and evaporated to give an oil, which contained
1-bromo-2,2-diphenylcyclopropane 127%), 1,1-dibromo-
1iv) With copper *I) iodide and allyl bromide. 1-Bromo-
magnesio-1-bromo-2-phenyl-cyclopropane was prepared
as above using 1,1-dibromo-2-phenylcyclopropane 1221

1590
M. S. Baird et al. / Tetrahedron 58 *2002) 1581±1593
mg, 0.8 mmol), dry THF 11.2 ml) and 1.0 M ethylmag-
nesium bromide 13.2 ml, 3.2 mmol, 4.00 mol equiv.) at
2608C. Copper 1I) iodide 1647 mg, 3.4 mmol, 4.25 mol
equiv.) was added at temperature 2608C and stirring was
continued for 30min at that temperature. A solution of allyl
bromide 1774 mg, 0.55 ml, 6.4 mmol, 8.00 mol equiv.) in
dry THF 10.45 ml) was added at 260^18C and stirring
was continued for 30min at that temperature. The mixture
was warmed to 08C for 180min, then water 10.5 ml) was
added and the resulting suspension was diluted with petro-
leum to 20ml. Magnesium sulphate 11 g) was added and
solution decanted, the solid was washed with petroleum
12£10ml). The combined organic layers were dried
and evaporated to give a colourless liquid 1129 mg) which
contained 1,1-diethyl-2-phenylcyclopropane 114%), 1-ethyl-
1-allyl-2-phenylcyclopropane 176%, trans/cis 1.4:1 by
GLC) and trans-1-bromo-1-allyl-2-phenyl-cyclopropane
19%) by GLC. Part of this 1110mg) was separated by
column chromatography on silica eluting with petroleum
to give 1,1-diethyl-2-phenylcyclopropane 16 mg) which
showed dH: 0.70±0.90 16H, m), 1.01 13H, t, Jˆ7.3 Hz),
1.15±1.29 12H, m), 1.64 11H, dd, Jˆ14.6, 7.3 Hz), 1.92
11H, dd, Jˆ7.9, 6.1 Hz), 7.17±7.3015H, m); 1 m/z, %):
175 12, M111), 174 114, M1), 146 114), 145 1100), 130
116), 128 116), 117 136), 115 112), 105 110), 104 155), 91
132), 77 128), 65 115), 55 121), 51 122), trans-1-bromo-1-
allyl-2-phenylcyclopropane31 110mg) and 1-allyl-1-ethyl-2-
phenyl-cyclopropane 150mg) which showed dH: 0.78±1.35
17H, m), 1.51±1.75 11H, m), 1.92±2.44 12H, m), 4.89±5.00
11H, m), 5.08±5.20 11H, m), 5.62±6.05 11H, m), 7.16±7.34
15H, m); dC: 10.51, 10 .71, 15.92, 16.42, 23.62, 27.8,
28.71, 29.01, 30.12, 34.92, 41.22, 115.62, 116.22,
125.51, 125.61, 127.81, 127.91, 129.01, 136.51,
136.81, 139.7; IR 1cm21, ®lm): 3061 m, 3025 m, 2995 m,
2962 s, 2921 m, 2873 m, 995 m, 910s, 734 s, 698 s; 1 m/z, %)
1trans isomer) 1Rt 11.3 min): 186 11, M1), 171 11), 146 113),
145 1100), 129 141), 117 133), 115 119), 105 112), 104 151),
91 149), 77 133), 67 126), 65 116), 53 115), 51 119); 1m/z, %)
1cis isomer) 1Rt 11.33 min): 186 11, M1), 146 113), 145
1100), 129 143), 117 133), 115 130), 104 162), 91 163), 77
149), 67 137), 65 116), 63 113), 53 122), 51 121). The isomers
were inseparable by column chromatography.
1,1-dibromo-2-hexylcyclopropane 1568 mg, 2.0mmol), dry
THF 14 ml) and 0.8 M isopropylmagnesium bromide
17.5 ml, 6.0mmol, 3.00mol equiv.) at 2708C. A solution
of trimethylchlorosilane 11.086 g, 1.27 ml, 10 mmol, 5.0
mol equiv.) in dry THF 10.73 ml) was added at 2708C
and stirring was continued for 60min at the same tempera-
ture. The mixture was warmed to 08C for 60min and water
12 ml) was added. The organic layer was separated and the
water layer was extracted with petroleum 13£10ml). The
combined organic layers were dried and evaporated to give
1
an oil, which contained by H NMR only nona-1,2-diene
derived from cyclopropane.
1iii) With CO2. 1-Bromomagnesio-1-bromo-2-hexylcyclo-
propane was prepared as in 1ii). The mixture was cooled
to 2908C, dry CO2 was passed in for 10min 1rate 300ml/
min, 3 l, 130mmol, 65 mol equiv.) and stirring was con-
tinued for 60min at 2808C. The mixture was warmed to
08C for 100 min, poured in chloroform 140 ml) and washed
with a solution of concentrated hydrochloric acid 110ml) in
water 150ml). The organic layer was separated and the
water layer was extracted with chloroform 13£10ml). The
combined organic layers were extracted with sat. aq. sodium
bicarbonate 14£15 ml); the combined sodium bicarbonate
layers were extracted with chloroform 12£10ml), treated
with concentrated hydrochloric acid until pH 1 and
extracted with chloroform 14£20ml). The combined
organic layers were dried and evaporated to give an oil,
which was dissolved in ether 12 ml), treated with diazo-
methane until the yellow colour persisted, dried with
magnesium sulphate and evaporated in vacuo to give
methyl 2-bromo-1-hexylcyclopropanecarboxylate 1190mg,
0.72 mmol, 36%, trans/cis 1:1 by 1H NMR) as a colourless
liquid 1Calculated for C11H19BrO2: C 50.20; H 7.28%.
Found C 50.5; H 7.4%) which showed dH: 0.82±0.94 13H,
m), 1.02 11H, ®rst isomer, dd, Jˆ7.3, 5.5 Hz), 1.20±1.89
113H, m), 3.73 13H, s, ®rst isomer), 3.75 13H, s, second
isomer); dC: 13.91, 14.01, 22.472, 22.522, 24.62,
26.32, 27.62, 28.62, 28.72, 28.902, 28.932, 29.6,
31.62, 31.72, 34.11, 34.41, 53.11, 53.31, 169.3,
171.1; IR 1cm21, ®lm): 2954 s, 2926 s, 2856 m, 1744 s,
1723 s, 1210s, 1126 m. The combined organic layers
from neutral fractions were washed with 10% aqueous
sodium hydroxide 13£10ml); the combined sodium
hydroxide layers were extracted with dichloromethane
12£10ml), treated with hydrochloric acid until pH 1 and
extracted with dichloromethane 13£10ml). The combined
organic layers were dried and evaporated in vacuo to give an
oil. This was dissolved in ether 12 ml), treated with diazo-
methane until the yellow colour persisted, dried with
magnesium sulphate and evaporated to give methyl
1-bromo-2-hexylcyclopropanecarboxylate 1200 mg, 0.76
mmol, 38%, trans/cis 1:1 by 1H NMR data) as a colourless
liquid with spectral data identical to those above 1total
1.5.4. 1-Bromomagnesio-1-bromo-2-hexylcyclopropane.
1i) With CH3OH. 1-Bromomagnesio-1-bromo-2-hexyl-
cyclopropane was prepared as above using 1,1-dibromo-2-
hexylcyclopropane 1852 mg, 3.0mmol), dry THF 16 ml)
and 0.8 M isopropylmagnesium bromide 111.25 ml,
9.0mmol, 3.00mol equiv.) at 2708C. The reaction mixture
was cooled to 2908C and methanol 11 ml) was slowly added
at not more than 2708C. The mixture was warmed to 08C
and water 11 ml) was added. The organic layer was sepa-
rated, the water suspension of magnesium salt was dissolved
in a small amount of 4 M hydrochloric acid and extracted
with pentane 13£10ml). The combined organic layers were
dried and evaporated. The product was treated with pentane
12 ml), ®ltered through silica 11.5 g), washing the silica with
pentane and evaporated to give 1-bromo-2-hexylcyclo-
propane31,32 1595 mg, 2.90mmol, 97%, trans/cis 1:1 by
GLC) as a colourless liquid.
1
390mg, 1.48 mmol, 74%, trans/cis 1:1 by H NMR.
1.5.5. Reactions of 7,7-dibromonorcarane with Grignard
reagents in THF. 1a) With methylmagnesium chloride.
1.0M Methylmagnesium chloride in THF 112.0ml, 12.0
mmol, 3.00 mol equiv.) was added to a stirred solution of
7,7-dibromobicylo[4,1,0]heptane 11.016 g, 4.0 mmol) in
dry THF 18 ml) under nitrogen at room temperature. Stirring
was continued for 24 h at room temperature when 5 ml of
1ii) With trimethylchlorosilane. 1-Bromomagnesio-1-
bromo-2-hexylcyclopropane was prepared as above using

M. S. Baird et al. / Tetrahedron 58 *2002) 1581±1593
1591
reaction mixture was worked up with D2O 12 ml). This
sample contained by GLC and GC/MS, tricyclo[4.1.0.02,7]-
heptane33 and tricyclo[3.2.0.02,7]heptane34 14%, Rt 2.30and
2.48 min) which showed 1m/z, %): 94 133, M1), 93 118), 91
116), 79 1100), 77 137), 62 19), 61 110), 56 111); 7-methyl-7-
deuteriobicylo[4,1,0]heptane 123%, exo-13 1RˆMe, EˆD)/
endo-13 1RˆMe, EˆD)ˆ3.0:1, Rt 1exo-13 1RˆMe, EˆD))
3.22 min, 1endo-13 1RˆMe, EˆD)) 4.17 min) which
showed 1m/z, %): 111 199, M1), 96 146), 82 142), 81
1100), 78 15), 77 16), 70 118), 69 147), 68 157), 67 153);
7-bromobicyclo[4,1,0]heptane31 145%, exo-16/endo-16ˆ
1:2.0, Rt 1exo-16) 6.57 min, 1endo-16) 7.30min),
for 30min at room temperature, D 2O 11 ml) was added.
The reaction mixture contained by GLC and GC/MS
data 7,7-dibromobicylo[4,1,0]heptane35 16%), 7-ethyl-7-
deuterio-bicyclo[4,1,0]heptane 166%, exo-13 1RˆEt, Eˆ
D)/endo-131RˆEt, EˆD)ˆ3.8:1, Rt 1exo-13 1RˆEt, Eˆ
D)) 3.48 min, 1endo-13 1RˆEt, EˆD)) 4.26 min) which
showed 1m/z, %): 125 112, M1), 11014), 97 17), 96 140),
84 110), 81 172), 69 110), 67 1100), 54 184); tricyclo-
[4.1.0.02,7]heptane and tricyclo[3.2.0.02,7]heptane 19%, Rt
2.16 min),7-ethyl-7-bromobicylo[4,1,0]heptane 12%, Rt 7.30
min), with spectral data identical to those above and 7-ethyl-
70-deuterio-*7,70)-bi*bicyclo-[4,1,0]heptyl) 112%, Rt 11.13
and 11.32 min) which showed 1m/z, %) for isomer with Rt
11.13: 219 12, M1), 191 15), 190128), 176 19), 162 13), 137
19), 134 16), 122 141), 108 128), 105 117), 94 146), 92
126), 82 110), 80 1100), 77 115), 68 127), 67 128), 65 114),
53 111); 1m/z, %) for isomer with Rt 11.32: 219 12, M1), 191
13), 190129), 176 110), 162 13), 15016), 137 111), 123 112),
122 124), 108 154), 106 119), 105 19), 95 168), 93 118), 92
141), 81 1100), 79 149), 77 122), 67 150), 65 19), 55 159),
53 128). The components were inseparable by column
chromatography.
7-bromo-7-methylbicyclo[4,1,0]heptane31 120%) which
1
showed 1m/z, %): 190115, M
,
81Br), 188 115, M1, 79Br),
148 118), 146 118), 135 16), 133 16), 109 1100), 81 115), 79
113), 77 16), 68 118), 67 137) and 7,7-dibromobicyclo[4,1,0]-
heptane 14%). The rest of the reaction mixture was worked
up with water and contained by GLC and GC/MS tri-
cyclo[4.1.0.02,7]heptane33 and tricyclo[3.2.0.02,7]heptane34
with spectral data identical to those above, 7-methylbi-
cyclo[4,1,0]heptane 123%, exo-13 1RˆMe, EˆH)/endo-13
1RˆMe, EˆH)ˆ3.0:1, Rt 1exo-13 1RˆMe, EˆH)) 3.22 min,
1endo-13 1RˆMe, EˆH)) 4.17 min) which showed 1m/z,
%): 110157, M 1), 95 129), 82 129), 81 1100), 68 159), 67
178); 7-bromobicyclo[4,1,0]heptane31 145%, exo-16/endo-
16ˆ1:2.0, Rt 1exo-16) 6.57 min, 1endo-16) 7.30min),
7-bromo-7-methyl-bicyclo[4,1,0]heptane31 120%) with
spectral data identical as above and 7,7-dibromo-bicyclo-
[4,1,0]heptane35 14%). The components were inseparable
by column chromatography.
1d) With isopropylmagnesium bromide. 0.8 M Isopropyl-
magnesium bromide in THF 15.0ml, 4.0mmol, 2.00mol
equiv.) was added to a stirred solution of 7,7-dibromobi-
cylo[4,1,0]heptane 1508 mg, 2.0 mmol) in dry THF 14 ml)
under nitrogen at room temperature. Stirring was continued
for 30min at room temperature when water 11 ml) was
added. The reaction mixture contained by GLC and GC/
MS tricyclo[4.1.0.02,7]heptane33 and tricyclo[3.2.0.02,7]-
heptane34 155%, Rt 2.30and 2.48 min) with spectral data
identical to those above, 7-isopropylbicylo[4,1,0]heptane
123%, exo-13 1Rˆi-Pr, EˆH)/endo-13 1Rˆi-Pr, EˆH)ˆ
3.9:1, Rt 1exo-13 1Rˆi-Pr, EˆH)) 5.11 min, 1endo-13
1Rˆi-Pr, EˆH)) 6.00 min) which shown 1m/z, %): 138
111, M1), 123 119), 109 15), 96 115), 95 198), 93 110),
82 178), 81 166), 80 148), 79 119), 67 1100); 7-bromo-
bicyclo-[4,1,0]heptane27 16%, exo-16/endo-16ˆ1:1.9, Rt
1exo-16) 6.57 min, 1endo-16) 7.30min) and 7-isopropyl-7-
bromobicyclo[4,1,0]heptane 11%, Rt 9.20min) which
showed 1m/z, %): 218 115, M1, 81Br), 216 115, M1, 79Br),
137 1100), 131 111), 123 111), 95 140), 81 199), 69 115).
All compounds were inseparable by column chromato-
graphy.
1b) With ethylmagnesium bromide *work up with H2O).
1.0 M Ethylmagnesium bromide in THF 110.0 ml, 10.0
mmol, 2.00 mol equiv.) was added to a stirred solution of
7,7-dibromobicylo[4,1,0]heptane 11.270 g, 5.0 mmol) in
dry THF 110ml) under nitrogen at room temperature.
Stirring was continued for 30min at room temperature
when water 11 ml) was added. The reaction mixture
contained by GLC and GC/MS 7,7-dibromobicylo[4,1,0]-
heptane35 16%), 7-ethylbicylo[4,1,0]heptane 166%, exo-13
1RˆEt, EˆH)/endo-13 1RˆEt, EˆH)ˆ3.8:1, Rt 1exo-13
1RˆEt, EˆH)) 3.48 min, 1endo-13 1RˆEt, EˆH)) 4.26
min) which showed 1m/z, %): 124 112, M1), 109 14), 96
17), 95 141), 83 19), 81 172), 79 116), 77 111), 68 124), 67
183), 54 1100); tricyclo[4.1.0.02,7]heptane33 and tri-
cyclo[3.2.0.02,7]heptane34 19%, Rt 2.16 min) with spectral
data identical as above, 7-bromo-7-ethyl-bicylo[4,1,0]-
heptane 12%, Rt 7.30min) which showed 1 m/z, %): 204 13,
M1, 81Br), 202 13, M1, 79Br), 162 12), 16012), 123 118), 108
12), 96 17), 94 17), 81 192), 67 1100), 55 139) and 7-ethyl-
17,70)-bi1bicyclo[4,1,0]heptyl) 112%, Rt 11.13 and 11.32
min) which showed 1m/z, %) for isomer with Rt 11.13:
218 12, M1), 189 154), 175 15), 162 16), 148 116), 135
132), 132 110), 122 131), 119 114), 108 156), 96 122), 94
134), 92 122), 81 138), 79 1100), 67 159), 55 139); 1m/z, %)
for isomer with Rt 11.32: 218 14, M1), 189 177), 176 118),
149 110), 147 17), 136 114), 134 114), 132 110), 121 164), 118
111), 108 164), 106 125), 96 134), 93 153), 81 125), 79 187),
67 156), 55 1100). All compounds were inseparable by
column chromatography.
1.5.6. Synthesis of 1-bromo-2-hexylcyclopropene. 1.0M
ethylmagnesium bromide in THF 13.9 ml, 3.9 mmol,
1.30mol equiv.) was added to a stirred solution of 1,1,2-
tribromo-2-hexylcyclopropane 11.089 g, 3.0 mmol) in dry
THF 16 ml) under nitrogen at room temperature for
12 min. Stirring was continued for 30min at room
temperature when water 10.5 ml) was added. The
reaction mixture was diluted with petroleum to 50ml,
dried and evaporated to give a yellow liquid 1597 mg)
which was puri®ed on silica 115 g) eluting with
petroleum
to
give
1-bromo-2-hexylcyclopropene36
1491 mg, 2.42 mmol, 81%) as a colourless liquid which
showed dH: 0.89±0.93 13H, m), 1.26±1.47 16H, m), 1.53
12H, s), 1.54±1.63 12H, m), 2.44 12H, t, Jˆ7.0Hz); dC:
14.01, 17.12, 22.52, 25.42, 26.32, 28.92, 31.52, 92.2,
118.0; IR 1cm21, ®lm): 2958 s, 2929 s, 2879 s, 2858 s,
1033 s.
1c) With ethylmagnesium bromide *work up with D2O).
Procedure 1a) was repeated except that, after stirring

1592
M. S. Baird et al. / Tetrahedron 58 *2002) 1581±1593
675. Baird, M. S.; Huber, F. A. M.; Tverezovsky, V. V.; Bole-
sov, I. G. Tetrahedron 2000, 56, 4799.
Acknowledgements
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1935. Danheiser, R. L.; Morin, J. M.; Yu, M.; Basak, A.
Tetrahedron Lett. 1981, 4205.
This work was carried out as a part of a project supported by
the Copernicus programme.
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