Synthesis and trapping of some substituted 1-bromocyclopropenes

Article abstract of DOI:10.1007/s00706-006-0441-0

Treatment of a number of 2-substituted 1,1,2-tribromocyclopropanes with MeLi at -78°C gave the corresponding 1-bromocyclopropenes, which were reacted with three cyclic dienes to yield the [4 + 2]-cycloadducts. Cycloaddition with 1,3-diphenylisobenzofuran

Full text of DOI:10.1007/s00706-006-0441-0

Monatshefte f€ur Chemie 137, 483–500 (2006)
DOI 10.1007/s00706-006-0441-0
Synthesis and Trapping of Some
Substituted 1-Bromocyclopropenes
ꢀ
Karl F. S. Alnes and Leiv K. Sydnes
Department of Chemistry, University of Bergen, NO-5007 Bergen, Norway
Received June 27, 2005; accepted (revised) August 17, 2005
Published online March 17, 2006 # Springer-Verlag 2006
Summary. Treatment of a number of 2-substituted 1,1,2-tribromocyclopropanes with MeLi at ꢁ78ꢂC
gave the corresponding 1-bromocyclopropenes, which were reacted with three cyclic dienes to yield
the [4þ 2]-cycloadducts. Cycloaddition with 1,3-diphenylisobenzofuran (DPIBF) gave the exo
adducts, in most cases in excellent yield, whereas cyclopentadiene afforded endo adducts only, but
in moderate yield. In most reactions with furan no adduct was formed, but two 1-bromocyclopropenes
derivatives with an aromatic side chain were exceptions and furnished mixtures of exo and endo
adducts in moderate yields.
Keywords. Cycloadditions; Small rings; Organolithium compounds; Alkynes; Allenes.
Introduction
During the last few decades the interest in the chemical properties of cyclopro-
penes has grown considerably. New synthesis methods have been developed and
made a variety of such compounds more easily available [1–4]. As a result, cy-
clopropenes have gradually emerged as a valuable group of synthetic intermedi-
ates, particularly for the synthesis of polycyclic and strained hydrocarbons [2–4].
Most of the cyclopropenes prepared and investigated have been alkyl- and aryl-
substituted compounds, but more recently 1-halocyclopropenes have attracted
considerably more attention due to their ability to rearrange, to form versatile
organolithium reagents which react with a range of electrophiles, and to undergo
[4 þ 2] cycloaddition reactions (Diels-Alder reactions).
The most predictable and versatile reaction involving any cyclopropene is
the Diels-Alder reaction, usually with the cyclopropene as the dienophile [5–7].
Most of these reactions have involved cyclic dienes, e.g. cyclopentadiene, furan,
1,3-diphenylisobenzofuran (DPIBF), and thiophene dioxide [5, 8–11], but
some acyclic dienes have also been employed. The simplest example involving
an acyclic, conjugated diene is the reaction between cyclopropene itself [1] and
ꢀ
Corresponding author. E-mail: leiv.sydnes@kj.uib.no

484
K. F. S. Alnes and L. K. Sydnes
buta-1,3-diene, which has been thoroughly studied and proved to proceed via an
endo transition state due to decisive influence of favourable secondary orbital
interactions (SOI) [12, 13]. An analogous transition state is probably involved
when the same cyclopropene reacts with cyclopentadiene, but when reacted with
DPIBF, a 3:1 mixture of the exo and the endo adducts is formed [5]. The pre-
dominant formation of the exo adduct in the latter reaction is explained as lack of
stabilising SOI [5].
In addition to reactions with cyclopropene itself, some cyclopropene deriva-
tives have been used in Diels-Alder reactions for synthetic purposes. Most of them
have been either 1,2-dihalocyclopropenes or tetrahalocyclopropenes, which have
been utilized to synthesize some highly strained cycloproparenes [14–16], but in
recent years a growing number of 1-halocyclopropenes have proved to be excel-
lent dienophiles as well. Thus, Banwell et al. used a 1-chlorocyclopropene in a
crucial step in the synthesis of the colchicine framework [8], and Ng and Wege used
a similar compound in their total synthesis of favelanone [17]. Furthermore, a few
substituted 1-halocyclopropenes have been trapped with dienes to prove the (trans-
cient) existence of the former [6, 18–20].
Based on the willingness of 1-halocyclopropenes to undergo Diels-Alder reac-
tions and the fact that 1-halocyclopropenes appear to be easily available from
readily accessible 1,1,2-trihalocyclopropanes, we decided to study the reactivity
of selected 2-substituted 1-bromocyclopropenes as dienophiles toward some con-
jugated dienes, with special emphasis on stereochemical aspects. The results of our
investigations are reported here.
Results and Discussion
The 2-substituted 1,1,2-tribromocyclopropanes 1 used as precursors for the cyclo-
propenes 2 in this study were synthesized from the corresponding 2-bromo-
1-alkenes as described in literature [21–24]. Formation of 2 was achieved by
dehalogenation of 1 with MeLi based on a procedure published by Baird et al.
[6, 25]. As expected the conversion of 1 to 2 was accompanied by a spontaneous
change of colour, from colourless to yellow=orange [26]. The compounds included
in this study are summarized in Fig. 1.
In order to find the optimum conditions for the whole process from 1 to the
[4 þ 2] cycloadducts, exploratory experiments were performed with some of the
Fig. 1. Addition of MeLi to 1 leads to bromine-lithium exchange, followed by elimination of LiBr
and formation of 2; a: R1,R2 ¼ –CH2CH2CH2CH2CH2CH2–; b: R1 ¼ phenoxymethyl, R2 ¼ H;
c: R1 ¼ (4-methylphenoxy)methyl, R2 ¼ H; d: R1 ¼ phenyl, R2 ¼ H; e: R1 ¼ 2-phenylethyl, R2 ¼ H;
f: R1 ¼ propyl, R2 ¼ H; g: R1 ¼ pentyl, R2 ¼ H; h: R1 ¼ octyl, R2 ¼ H; i: R1 ¼ cyclohexylmethyl,
R2 ¼ H; j: R1 ¼ isobutyl, R2 ¼ H; k: R1 ¼ tert-butyl, R2 ¼ H

Synthesis and Trapping of 1-Bromocyclopropenes
485
Scheme 1
cyclopropanes, varying the relative amount of MeLi and the reaction temperatures.
When the former parameter was varied, it appeared that even a moderate excess
of the reagent led to lithiation of the primary product and subsequent forma-
tion of by-products. Thus, when 1e was treated with more than 1.2 equivalents
of MeLi, 2-methyl-1-(2-phenylethyl)cyclopropene was obtained in addition to
1-bromo-2-(2-phenylethyl)cyclopropene (2e). The hydrocarbon is conceivably
formed in a two-step process, i.e. lithiation of 2e and formation of 1-lithio-2-
(2-phenylethyl)cyclopropene, which reacts with MeBr (Scheme 1), and its forma-
tion is no surprise when results reported in literature are considered [3, 27]. We
therefore decided to perform the conversion of 1 to 2 with a very small (1–3%)
excess of MeLi.
Secondly, it appeared to be important to control the reaction tempera-
tures properly due to the somewhat limited stability of the primary products, i.e.
1-bromocyclopropene derivatives 2. Thus, treatment of 1a with MeLi afforded
9-bromobicyclo[6.1.0]non-1(9)-ene (2a) (in quantitative yield), which turned out
to be stable at least for one week in the refrigerator, but which decomposes rapidly
at room temperature [28]. The product formed during such decomposition has been
studied by Lee et al., who reported that the chloro analogue to 2a, 9-chlorobicy-
clo[6.1.0]non-1(9)-ene, decomposes to an aldehyde and an allylic alcohol when
kept at room temperature [19]. It is therefore preferable to carry out the Diels-Alder
reaction well below room temperature if the reaction rates so permit.
Finally, it also appeared that the stability of some 1-bromocyclopropenes
could be increased by storing the compounds as solutions in THF. For instance,
treatment of 1,1,2-tribromo-2-octylcyclopropane (1h) with 1.02 equivalents of
MeLi gave 1-bromo-2-octylcyclopropene (2h), which was stable in THF at room
temperature for an extended period of time, but which turned out to decompose
when kept neat under otherwise identical conditions. Two rearrangement prod-
ucts, an acetylene and an allene, were formed in a 3:1 ratio and identified as
1-bromoundec-2-yne and 3-bromoundeca-1,2-diene on the basis of thorough
spectroscopic analyses. Other 2-substituted 1-bromocyclopropenes (2d, 2g, and
2i) behaved in a similar fashion. On the basis of reports published by Baird and
others formation of both compounds may be explained in terms of a 1,2-bromo
Scheme 2

486
K. F. S. Alnes and L. K. Sydnes
shift in an intermediate vinylcarbene as outlined in Scheme 2 [29]. It is interest-
ing to observe that 1-bromoundec-1-yne, which conceivably could result from a
1,2-alkyl shift in the alternative vinylcarbene, carrying a bromo substituent at the
divalent carbon, is not observed.
In order to minimise the possibility for the by-product formation discussed
above, the Diels-Alder reactions were carried out below room temperature. Three
dienes were employed, viz. 1,3-diphenylisobenzofuran (DPIBF), cyclopentadiene,
and furan, which have been reported to react with some cyclopropene derivatives,
albeit with different rates. Thus, DPIBF and cyclopentadiene react smoothly with
such dienophiles at room temperature [30–32], whereas furan reacts more reluc-
tantly [18] and therefore can be used to uncover reactivity differences among the
cyclopropene derivatives. A deficiency of the diene was used in the experiments
with both DPIBF and cyclopentadiene, the former because unreacted DPIBF
proved difficult to remove, and the latter because dicyclopentadiene formation
hampered the product isolation. (Removal of DPIBF could be achieved by oxida-
Scheme 3
Table 1. 1,2-Dehalogenation of 2-substituted 1,1,2-tribromocyclopropanes (1) with MeLi and sub-
sequent trapping of 2 with different dienes
Entry
Cyclopropane
Isolated yield of adducts=%
Exo-3
Endo-4
Exo-5
(DPIBF)
(cyclopentadiene)
(furan)
1
2
1a
1b
1c
1d
1e
1f
94
81
76
88
75
84
86
80
82
63
33
72
0a
46b
49
0
70
3
74
4
54
56a
5
0a
6
22
0
7
1g
1h
1i
29
0
8
35a
19a,c
26
0c
0a
0
9
10
11
1j
1k
12d
0
a
1-Bromocyclopropene (2) was isolated; b pure exo (31%) and impure endo-5b (15%) were isolated;
by-products were isolated; d the yield is based on 1H NMR data from a 3:6:1 mixture of 1k, endo-
c
4k, and exo-4k

Synthesis and Trapping of 1-Bromocyclopropenes
487
Fig. 2. The syn and anti positions of the exo and endo isomers of cycloadducts 3
tion with air [33], but this oxidation was slow and a complete conversion of DPIBF
to o-benzoylbenzophenone took several days.)
When cyclopropenes 2a–2k were reacted with DPIBF, the corresponding
cycloadduct 3 was isolated in good to excellent yield in all cases except one, viz.
3k (R1 ¼ tert-butyl) which was isolated in 33% only (Scheme 3; Table 1, Entry 11).
All adducts were formed and isolated as a single isomer, which in all cases was
assigned the exo configuration on the basis of spectroscopic evidence. NMR spectros-
copy appeared to be particularly informative in the case of compounds 3b–3k
because one of the cyclopropyl protons appeared consistently at a much lower field
than the other: The signal associated with the proton anti to the oxygen atom was
found at 1.69–2.17 ppm, while the syn proton appeared between 2.80 and 3.09 ppm.
This difference may conceivably be attributed to the diamagnetic anisotropy of the
oxygen atom, which causes a decrease in the shielding of the syn proton relative to
the anti proton (Fig. 2) [34]. This interpretation is in agreement with that reported by
Binger et al. [5], which showed that the formation of the exo isomer at the expense
of endo was due to the lack of a favourable SOI in the transition state. Moreover, it is
noteworthy that halogen-substituted dienophiles are believed to favour endo addition
to dienes, and in some cases the halogen substituent may even compete with car-
boxyl groups for the endo orientation [35–37].
When DPIBF was replaced by cyclopentadiene, the addition to cyclopropenes
2a–2k and the formation of the corresponding cycloadducts 4a–4k proceeded much
slower and were significantly less efficient than when DPIBF was used (Scheme 4).
The yield ranged from poor to good, but in all cases adduct 4 was obtained in lower
yield than the corresponding adduct 3. The best yields were furnished when substit-
uent R1 contained an aromatic moiety (Table 1, Entries 2–5), and this trend clearly
indicates the influence of some sort of ꢀ–ꢀ interaction, which overcomes the steric
repulsion otherwise present (Table 1, Entries 9–11). Since monitoring of the reaction
by TLC and GC showed a rapid and complete conversion of 1 to 2, the low yields
of adducts 4 must be due to poor reactivity towards cyclopentadiene. It is therefore
not surprising that considerable amounts of unreacted 2 were isolated in some cases
Scheme 4

488
K. F. S. Alnes and L. K. Sydnes
Fig. 3. Favourable SOI and steric hindrance favour the endo adduct over the exo analogue
(Table 1, Entries 5, 8, and 9; 13, 39, and 35%), and in the reaction with 1i 1-bromo-4-
cyclohexylbut-2-yne (5%) was also isolated.
The reactions with cyclopentadiene proceed in accordance with Alder’s endo
rule [38] in all cases except one, viz. the reaction with 1k (R1 ¼ tert-butyl) where
the endo and exo isomers were formed in a 6:1 ratio. The small difference in
the shift values of the cyclopropyl protons supported the assignment. In 4d
(R1 ¼ phenyl) the two protons even gave signals that overlapped so extensively
1
that a broad singlet appeared at 1.78 ppm in the H NMR spectrum. In addition
to favourable secondary orbital interactions, steric hindrance caused by the methy-
lene bridge is probably a decisive factor for the outcome of the reaction (Fig. 3).
This reasoning is supported by observations reported by Closs et al., who isolated
only the endo adduct when 3-methylcyclopropene reacted with cyclopentadiene,
whereas no adduct was observed at all when 3,3-dimethylcyclopropene was reacted
under similar conditions [4, 39].
Furan, the least reactive of the dienes used in this study, did not react with the
cyclopropenes under the conditions employed for cyclopentadiene and DPIBF; this
is not surprising considering the fact that Diels-Alder reactions involving furan are
usually performed around 80ꢂC [30]. Since such a high temperature is incom-
patible with the relatively low thermal stability of the cyclopropenes generated
in this study, we adopted a modified procedure, developed by Baird et al. [18],
which makes use of a large excess of furan (10 eq.) that is present during the MeLi
addition and the generation of 2 (Scheme 5). In spite of this modification, however,
cycloadduct formation was observed in two reactions only, viz. those involving
1-bromo-2-(phenoxymethyl)cyclopropene (2b) and 1-bromo-2-[(4-methylphenoxy)-
methyl]cyclopropene (2c). The corresponding cycloadducts 5b and 5c were formed
as mixtures of the exo and endo isomers, but due to formation of at least four other
products, complete analysis of the reaction mixtures and proper isolation of the
cycloadducts were hampered. However, it was determined that exo-5b and exo-5c
each was formed in 45–50% yield (Table 1, Entries 2 and 3) and that the corre-
sponding endo isomers were obtained in significantly lower yield (see Experimen-
Scheme 5

Synthesis and Trapping of 1-Bromocyclopropenes
489
Scheme 6
tal). Furthermore, pure samples of exo-5b and exo-5c were isolated in 31 and
49% yield.
The reactions with 1a, 1e, and 1i afforded no cycloadduct, but were never-
theless very clean and gave one product only. In each case the product appeared to
be the corresponding 1-bromocyclopropene, which was isolated in 100, 96, and 74%
yield. The rest of the 1,1,2-tribromocyclopropanes, however, gave complex reac-
tion mixtures, from which it was generally very difficult to isolate pure samples of
the individual compounds. One exception is the reaction involving furan and 1,1,2-
tribromo-2-octylcyclopropane (1h); from the product mixture 1-bromoundec-2-yne
(6) and 3-bromoundeca-1,2-diene (7) were isolated in 22 and 17% yield (Scheme 6).
These products are most likely formed as outlined in Scheme 3, although formation
of 7 from 6 can be envisaged. However, when pure 6 in THF was refluxed in the
presence and absence of MeLi, no allene was formed; hence, the allene does not
originate from the acetylene by rearrangement.
On the basis of the results reported here, it can be concluded that the 1-bro-
mocyclopropenes studied here exhibit the same reactivity toward cyclopentadiene,
DPIBF, and furan as cyclopropene and alkyl-substituted cyclopropenes, viz. the
reaction rate and the chemical yield vary in the order DPIBF>cyclopentadieneꢃ
furan. Due to the reluctance of furan to react the thermal instability of the cyclo-
propenes becomes important; as a result most of the product mixtures from the
furan reactions contain several compounds formed by decomposition of the
1-bromocyclopropenes. Furthermore, it appears that the lack of secondary orbital
interactions are important in the reactions with DPIBF; thus, in these cycloaddi-
tions exo adducts are formed exclusively whereas Alder’s endo rule is followed
when cyclopentadiene is involved.
Experimental
General Remarks
The instrumentation and analyses methods have been described in Ref. [24]. Some of the HRMS
analyses were obtained on an Autospec Ultima2000 Micromass spectrometer with EBE-geometry. The
spectrometer was operated in the EI mode at 70eV and the samples were injected at an ion source
temperature of 170ꢂC.
THF was distilled from Na-benzophenone ketyl under N2 immediately prior to use. MeLi was
obtained from commercial sources (Fluka) and standardized by titration against butan-2-ol in xylene
with N-phenyl-1-naphthylamine as indicator [40].

490
K. F. S. Alnes and L. K. Sydnes
The structure elucidation of the adducts (3, 4, and 5) was simplified with the use of 2D NMR
experiments (COSY, HSQC, HMBC and NOESY) [41], in addition to the standard analyses listed
under Experimental. The connectivity between 1H nuclei was revealed by COSY, whereas HSQC and
HMBC gave an overview of the H,C correlation and in some cases useful information about close
1
spatial relationship between H nuclei were given by using the NOESY experiment.
Formation and Trapping of 1-Bromocyclopropenes 2 with DPIBF; General Procedure
The cyclopropane 1 was dissolved in 40 cm3 THF in a round-bottomed flask, equipped with a con-
denser connected to a N2 inlet. The solution was cooled to ꢁ78ꢂC (acetone=dry-ice or ethyl acetate=
liquid N2). MeLi (1.01–1.03 eq) was added dropwise with magnetic stirring. Stirring was continued at
rt for 1 h, before DPIBF (0.8 eq) was added at a temperature well below 0ꢂC [6]. The reactions were
monitored by TLC and quenched with a portion of water. The product 3 was extracted with diethyl
ether, the solution was dried (MgSO4), filtrated, and evaporated in vacuo, and finally 3 was isolated by
either flash chromatography or recrystallization.
10-Bromo-14-oxa-1,11-diphenyl-12,13-benzotetracyclo[9.2.1.02,9.02,10]tetradecane
(3a, C29H27OBr)
The synthesis was carried out with 0.90 g 1a (2.49 mmol), 1.60cm3 MeLi (1.60 M, 2.56mmol), and
0.54g DPIBF (2.00 mmol). Flash chromatography (n-hexane:ethyl acetate ¼ 98:2) afforded 0.89 g 3a
(94%) as a colourless oil. Subsequent recrystallization (n-hexane) gave white crystals, mp 187–188ꢂC.
IR (KBr): ꢁꢀ¼ 3036m, 2914 s, 2852 s, 1496w, 1454s, 1343m, 1295 m, 1273m, 1168w, 989 br, 916m,
1
753 br, 700 s cmꢁ1; H NMR (400 MHz; CDCl3; Me4Si): ꢂ ¼ 0.90–1.10 (2H, m), 1.28–1.56 (8H, m),
1.64–1.68 (1H, m), 1.95–2.00 (1H, m), 2.54–2.58 (1H, m), 7.24–7.51 (9H, m), 7.75–7.78 (2H, m),
7.84–7.90 (3H, m) ppm; 13C NMR (100MHz; CDCl3; Me4Si): ꢂ ¼ 25.5 (CH2), 25.6 (CH2), 25.9
(CH2), 26.5 (CH2), 26.8 (CH2), 27.6 (CH2), 32.4 (CH), 39.8 (C), 57.6 (CBr), 89.5 (CO), 89.8 (CO),
121.6 (CH2), 122.7 (CH2), 126.0 (CH), 126.2 (CH), 126.5 (CH), 127.9 (CH), 128.0 (CH), 128.3 (CH),
128.9 (CH), 129.7 (CH), 133.8 (C), 137.2 (C), 146.7 (C), 148.4 (C) ppm; MS (EI): m=z (%) ¼ 391
(Mþꢁ Br, 100), 270 (25), 105 (80), 91 (16), 77 (24); HRMS (EI): m=z calcd. for Mþꢁ Br, C29H27Oþ,
391.2062; found 391.2083.
2-Bromo-8-oxa-4-phenoxymethyl-1,5-diphenyl-6,7-benzotricyclo[3.2.1.02,4]octane
(3b, C30H23O2Br)
The synthesis was carried out with 0.96 g 1b (2.49 mmol), 1.70 cm3 MeLi (1.50 M, 2.55mmol), and
0.54g DPIBF (2.00 mmol). Flash chromatography (n-hexane:ethyl acetate ¼ 97.5:2.5) afforded
0.80g 3b (81%) as a colourless oil. Subsequent recrystallization (n-hexane) gave white crystals, mp
146–148ꢂC. IR (KBr): ꢁꢀ¼ 3041 m, 2907m, 2857m, 1595 m, 1495 m, 1452m, 1395w, 1337 w,
1
1295 m, 1242s, 1176 w, 1124 w, 1077 w, 1033 m, 982 m, 945 w, 895 w, 755 s, 695 s cmꢁ1; H NMR
(400 MHz; CDCl3; Me4Si): ꢂ ¼ 2.07 (1H, d, J ¼ 6.5 Hz), 2.98 (1H, dd, J ¼ 6.5 and 0.7 Hz), 3.91 (1H, d,
J ¼ 10.7Hz, OCH), 4.14 (1H, dd, J ¼ 10.7 and 0.7 Hz, OCH), 6.77–6.81 (2H, m), 6.91–6.95 (1H, m),
7.21–7.51 (12H, m), 7.79–7.87 (4H, m) ppm; 13C NMR (50 MHz; CDCl3; Me4Si): ꢂ ¼ 28.2 (CH2),
36.6 (C), 49.9 (CBr), 67.9 (OCH2), 90.0 (CO), 90.3 (CO), 114.4 (CH), 120.9 (CH), 121.7 (CH), 122.9
(CH), 126.5 (CH), 126.6 (CH), 128.2 (CH), 128.4 (CH), 128.8 (CH), 128.9 (CH), 129.1 (CH), 129.2
(CH), 129.3 (CH), 133.2 (C), 133.9 (C), 147.6 (C), 148.0 (C), 158.4 (C) ppm; MS (EI): m=z (%) ¼ 415
(Mþꢁ Br, 30), 321 (46), 270 (10), 105 (100), 77 (35); HRMS (EI): m=z calcd. for Mþꢁ Br,
C30H23O2þ, 415.1698; found 415.1699.
2-Bromo-4-(4-methylphenoxy)methyl-8-oxa-1,5-diphenyl-6,7-benzotricyclo[3.2.1.02,4]octane
(3c, C31H25O2Br)
The synthesis was carried out with 1.00 g 1c (2.51 mmol), 1.60cm3 MeLi (1.60 M, 2.56 mmol), and
0.54g DPIBF (2.01 mmol). Flash chromatography (n-hexane:ethyl acetate¼ 97.5:2.5) afforded 0.78g
3c (76%) as a colourless oil. Subsequent recrystallization (n-hexane) gave white crystals, mp 140ꢂC. IR

Synthesis and Trapping of 1-Bromocyclopropenes
491
(KBr): ꢁꢀ¼ 3030m, 2915 m, 2855 m, 1510s, 1449 m, 1390w, 1298m, 1237 s, 1175m, 1031m, 983m,
811 br, 755 s, 698 s cmꢁ1; 1H NMR (400 MHz; CDCl3; Me4Si): ꢂ ¼ 2.06 (1H, d, J ¼ 6.3 Hz, CH), 2.26
(3H, s, CH3), 2.96 (1H, d, J ¼ 6.3Hz, CH), 3.88 (1H, d, J ¼ 10.4 Hz, OCH), 4.11 (1H, d, J ¼ 10.4Hz,
OCH), 6.67–6.70 (2H, m, 2ꢄCH), 7.03–7.04 (2H, m, 2ꢄCH), 7.27–7.50 (10H, m, 10ꢄCH),
7.79–7.81 (2H, m, 2ꢄCH), 7.85–7.86 (2H, m, 2ꢄCH) ppm; 13C NMR (100 MHz; CDCl3; Me4Si):
ꢂ ¼ 20.3 (CH3), 28.1 (CH2), 36.7 (C), 49.9 (CBr), 68.0 (OCH2), 90.0 (CO), 90.3 (CO), 114.2 (2ꢄCH),
121.7 (CH), 122.8 (CH), 126.4 (CH), 126.6 (CH), 128.2 (2ꢄCH), 128.4 (2ꢄCH), 128.8 (2ꢄCH),
128.9 (CH), 129.1 (CH), 129.2 (2ꢄCH), 129.7 (2ꢄCH), 130.1 (C), 133.2 (C), 133.9 (C), 147.7 (C),
148.0 (C), 156.3 (C) ppm; MS (EI): m=z (%) ¼ 510=508 (Mþ, 1=1), 429 (26), 403=401 (13=13), 321
(100), 270 (14), 105 (83), 91 (7), 77 (19); HRMS (EI): m=z calcd. for Mþ, C31H25O2Brþ, 508.1038;
found 508.1002.
2-Bromo-8-oxa-1,4,5-triphenyl-6,7-benzotricyclo[3.2.1.02,4]octane (3d, C29H21OBr)
The synthesis was carried out with 0.89 g 1d (2.51 mmol), 1.70 cm3 MeLi (1.50 M, 2.55 mmol),
and 0.54 g DPIBF (2.00 mmol). Flash chromatography (n-hexane:ethyl acetate ¼ 95:5) afforded
0.82 g 3d (88%) as a colourless oil. Subsequent recrystallization (n-hexane) gave white crystals,
mp 134–136ꢂC. IR (KBr): ꢁꢀ¼ 3062 m, 3028 m, 2999 m, 2954 m, 2867 m, 1495 m, 1448 m, 1345 m,
1
1297 m, 1177 w, 1013 w, 977 s, 912 w, 883 m, 760 br, 700 s cmꢁ1; H NMR (400 MHz; CDCl3;
Me4Si): ꢂ ¼ 1.90 (1H, d, J ¼ 5.8 Hz), 3.09 (1H, d, J ¼ 5.8 Hz), 6.59–6.62 (2H, m), 7.14–7.55 (15H,
m), 7.91–7.94 (2H, m) ppm; 13C NMR (100 MHz; CDCl3; Me4Si): ꢂ ¼ 29.4 (CH2), 44.4 (C), 49.1
(CBr), 90.1 (CO), 90.3 (CO), 122.1 (CH), 123.0 (CH), 126.2 (CH), 126.6 (CH), 126.7 (2ꢄCH),
127.48 (2ꢄCH), 127.50 (CH), 127.9 (3ꢄCH), 128.4 (2ꢄCH), 129.1 (CH), 129.3 (2ꢄCH), 131.7
(2ꢄCH), 133.7 (C), 134.8 (C), 135.2 (C), 147.7 (C), 147.9 (C) ppm; MS (EI): m=z (%) ¼ 466=464
(Mþ, 2=2), 385 (Mþꢁ Br, 100), 270 (27), 105 (48), 77 (36); HRMS (EI): m=z calcd. for Mþꢁ Br,
C29H21Oþ, 385.1592; found 385.1595.
2-Bromo-8-oxa-1,5-diphenyl-4-(2-phenylethyl)-6,7-benzotricyclo[3.2.1.02,4]octane
(3e, C31H25OBr)
The synthesis was carried out with 0.96g 1e (2.50 mmol), 1.60cm3 MeLi (1.60 M, 2.56mmol),
and 0.54g DPIBF (2.00 mmol). Flash chromatography (n-hexane:ethyl acetate ¼ 97.5:2.5) afforded
0.74g 3e (75%) as a colourless oil. Subsequent recrystallization (n-hexane) gave white crystals,
mp 142–143ꢂC. IR (KBr): ꢁꢀ¼ 3065 m, 3026 m, 2929m, 2857m, 1496 w, 1451m, 1348 m, 1300m,
1156 w, 978 br, 910 w, 754 br, 699s cmꢁ1; 1H NMR (200MHz; CDCl3; Me4Si): ꢂ ¼ 1.48–1.64 (1H, m),
1.77 (1H, d, J ¼ 6.3 Hz, CH), 1.91–2.07 (1H, m), 2.54–2.63 (2H, m, CH2), 2.85 (1H, d, J ¼ 6.3 Hz,
CH), 7.01–7.32 (7H, m, 7ꢄCH), 7.41–7.52 (8H, m, 8ꢄCH), 7.72–7.77 (2H, m, 2ꢄCH), 7.81–7.87
(2H, m, 2ꢄCH) ppm; 13C NMR (50 MHz; CDCl3; Me4Si): ꢂ ¼ 27.8 (CH2), 30.3 (CH2), 34.4 (CH2),
36.9 (C), 50.5 (CBr), 90.2 (CO), 90.3 (CO), 121.8 (CH), 122.8 (CH), 125.8 (CH), 126.2 (CH), 126.4
(CH), 128.1 (2ꢄCH), 128.2 (2ꢄCH), 128.3 (2ꢄCH), 128.4 (2ꢄCH), 128.5 (2ꢄCH), 128.9 (CH),
129.0 (CH), 129.2 (2ꢄCH), 133.5 (C), 134.4 (C), 141.5 (C), 147.1 (C), 148.0 (C) ppm; MS (EI): m=z
(%) ¼ 413 (Mþꢁ Br, 50), 270 (19), 105 (100), 91 (34), 77 (25); HRMS (EI): m=z calcd. for Mþꢁ Br,
C31H25Oþ, 413.1905; found 413.1902.
2-Bromo-8-oxa-1,5-diphenyl-4-propyl-6,7-benzotricyclo[3.2.1.02,4]octane (3f, C26H23OBr)
The synthesis was carried out with 0.80 g 1f (2.50 mmol), 1.70 cm3 MeLi (1.50 M, 2.55mmol), and
0.55g DPIBF (2.02 mmol). Flash chromatography (n-hexane:ethyl acetate ¼ 98:2) afforded 0.72g
3f (84%) as a light yellow oil. IR (film): ꢁꢀ¼ 3061s, 3041 s, 2959s, 2931s, 2870 s, 1604w, 1497 m,
1453 s, 1422 m, 1348s, 1301 s, 1181 m, 1160 w, 1093m, 1058 w, 981 br, 938 m, 907 br, 754br,
1
700 s cmꢁ1; H NMR (200 MHz; CDCl3; Me4Si): ꢂ ¼ 0.81 (3H, t, J ¼ 7.0 Hz, CH3), 1.10–1.37 (3H,
m), 1.57–1.64 (1H, m), 1.69 (1H, d, J ¼ 6.3 Hz), 2.80 (1H, d, J ¼ 6.3 Hz), 7.22–7.48 (10H, m),
7.68–7.72 (2H, m), 7.82–7.86 (2H, m) ppm; 13C NMR (50 MHz; CDCl3; Me4Si): ꢂ ¼ 14.2 (CH3),
21.4 (CH2), 27.6 (CH2), 30.3 (CH2), 36.9 (C), 50.7 (CBr), 90.26 (CO), 90.33 (CO), 121.8 (CH), 122.7

492
K. F. S. Alnes and L. K. Sydnes
(CH), 126.1 (CH), 126.2 (CH), 128.3 (CH), 128.4 (CH), 128.6 (CH), 128.8 (CH), 128.9 (CH), 129.2
(CH), 133.6 (C), 134.5 (C), 147.2 (C), 148.0 (C) ppm; MS (EI): m=z (%) ¼ 351 (Mþꢁ Br, 75), 327
(15), 270 (6), 246 (30), 103 (100), 91 (63), 77 (73); HRMS (EI): m=z calcd. for Mþ, C26H23OBrþ,
430.0932; found 430.0934.
2-Bromo-8-oxa-4-pentyl-1,5-diphenyl-6,7-benzotricyclo[3.2.1.02,4]octane (3g, C28H27OBr)
The synthesis was carried out with 0.88g 1g (2.52 mmol), 1.60 cm3 MeLi (1.60 M, 2.56 mmol), 0.55 g
DPIBF (2.02 mmol). Flash chromatography (n-hexane:ethyl acetate ¼ 98:2) afforded 0.80 g 3g (86%)
as a colourless oil. Subsequent recrystallization (n-hexane) gave white crystals, mp 84–86ꢂC. IR
(KBr): ꢁꢀ¼ 3064 m, 3037m, 2932 s, 2854s, 1600w, 1497 w, 1451s, 1423w, 1347m, 1297 s, 1180 w,
1100 w, 1004 m, 982 br, 934 w, 909 w, 875 br, 753 s, 699 s cmꢁ1; 1H NMR (400MHz; CDCl3; Me4Si):
ꢂ ¼ 0.80–0.84 (3H, m, CH3), 1.14–1.34 (7H, m), 1.62–1.68 (1H, m), 1.71 (1H, d, J ¼ 6.2 Hz), 2.80
(1H, d, J ¼ 6.2Hz), 7.25–7.32 (3H, m), 7.38–7.49 (7H, m), 7.69–7.71 (2H, m), 7.83–7.85 (2H, m)
ppm; 13C NMR (100MHz; CDCl3; Me4Si): ꢂ ¼ 13.9 (CH3), 22.3 (CH2), 27.6 (CH2), 27.8 (CH2), 27.9
(CH2), 31.9 (CH2), 37.0 (C), 50.8 (CBr), 90.3 (CO), 90.4 (CO), 121.8 (CH), 122.7 (CH), 126.1 (CH),
126.3 (CH), 128.3 (CH), 128.4 (CH), 128.6 (CH), 128.8 (CH), 128.9 (CH), 129.2 (CH), 133.7 (C),
134.6 (C), 147.3 (C), 148.1 (C) ppm; MS (EI): m=z (%) ¼ 379 (Mþꢁ Br, 100), 270 (25), 105 (96), 77
(36); HRMS (EI): m=z calcd. for Mþꢁ Br, C28H27Oþ, 379.2062; found 379.2104.
2-Bromo-4-octyl-8-oxa-1,5-diphenyl-6,7-benzotricyclo[3.2.1.02,4]octane (3h, C31H33OBr)
The synthesis was carried out with 0.98 g 1h (2.50 mmol), 1.70 cm3 MeLi (1.50 M, 2.55mmol), and
0.54g DPIBF (2.00 mmol). Flash chromatography (n-hexane:ethyl acetate¼ 97.5:2.5) afforded 0.80g
3h (80%) as a light yellow oil. IR (film): ꢁꢀ¼ 3061m, 3041m, 2926 s, 2856s, 1497m, 1454 s, 1349m,
1
1300 s, 1178 w, 1110 w, 1058 w, 982 br, 935 w, 909 m, 879 m, 756 s, 700 s cmꢁ1; H NMR (200MHz;
CDCl3; Me4Si): ꢂ ¼ 0.82–0.88 (3H, m, CH3), 1.19–1.30 (13H, m), 1.62–1.68 (1H, m), 1.70 (1H,
d, J ¼ 6.2 Hz), 2.80 (1H, d, J ¼ 6.2 Hz), 7.25–7.32 (3H, m), 7.38–7.48 (7H, m), 7.69–7.71 (2H, m),
7.83–7.85 (2H, m) ppm; 13C NMR (50 MHz; CDCl3; Me4Si): ꢂ ¼ 14.0 (CH3), 22.5 (CH2), 27.6 (CH2),
28.0 (CH2), 28.1 (CH2), 29.1 (CH2), 29.2 (CH2), 29.7 (CH2), 31.7 (CH2), 37.0 (C), 50.8 (CBr), 90.3
(CO), 90.4 (CO), 121.8 (CH), 122.7 (CH), 126.1 (CH), 126.2 (CH), 128.3 (CH), 128.4 (CH), 128.6
(CH), 128.8 (CH), 128.9 (CH), 129.2 (CH), 133.7 (C), 134.6 (C), 147.3 (C), 148.1 (C) ppm; MS (EI):
m=z (%) ¼ 421 (Mþꢁ Br, 100), 316 (32), 270 (20), 105 (48), 77 (12); HRMS (EI): m=z calcd. for
Mþꢁ Br, C31H33Oþ, 421.2531; found 421.2530.
2-Bromo-4-cyclohexylmethyl-8-oxa-1,5-diphenyl-6,7-benzotricyclo[3.2.1.02,4]octane
(3i, C30H29OBr)
The synthesis was carried out with 0.94 g 1i (2.50 mmol), 1.70 cm3 MeLi (1.50 M, 2.55 mmol), and
0.54g DPIBF (2.00 mmol). Flash chromatography (n-hexane:ethyl acetate ¼ 98:2) afforded 0.80 g 3i
(82%) as a white powder, mp 54–56ꢂC. IR (KBr): ꢁꢀ¼ 3060 br, 2921s, 2847 s, 1497w, 1449 m,
1347 m, 1298m, 1174 w, 1122 w, 1078 w, 981br, 906 w, 874 w, 754 s, 697s cmꢁ1 1H NMR
;
(400 MHz; CDCl3; Me4Si): ꢂ ¼ 0.76–0.84 (2H, m), 0.99–1.25 (5H, m), 1.49–1.70 (6H, m), 1.76
(1H, d, J ¼ 6.3 Hz), 2.93 (1H, d, J ¼ 6.3 Hz), 7.27–7.32 (3H, m), 7.39–7.48 (7H, m), 7.74–7.76
(2H, m), 7.82–7.85 (2H, m) ppm; 13C NMR (100MHz; CDCl3; Me4Si): ꢂ ¼ 26.1 (2ꢄCH2), 26.3
(CH2), 28.5 (CH2), 33.5 (CH2), 33.6 (CH2), 35.1 (C), 35.4 (CH2), 35.6 (CH), 50.3 (CBr), 90.2 (CO),
90.5 (CO), 122.1 (CH), 122.8 (CH), 126.1 (CH), 126.3 (CH), 128.3 (4ꢄCH), 128.8 (2ꢄCH), 128.9
(2ꢄCH), 129.3 (2ꢄCH), 133.6 (C), 134.6 (C), 147.1 (C), 148.0 (C) ppm; MS (EI): m=z (%) ¼ 405
(Mþꢁ Br, 100), 300 (20), 270 (26), 105 (71), 77 (21); HRMS (EI): m=z calcd. for Mþ, C30H29OBrþ,
484.1402; found 484.1442.
2-Bromo-4-isobutyl-8-oxa-1,5-diphenyl-6,7-benzotricyclo[3.2.1.02,4]octane (3j, C27H25OBr)
The synthesis was carried out with 0.84 g 1j (2.50 mmol), 1.70 cm3 MeLi (1.50 M, 2.55mmol), and
0.54g DPIBF (2.00 mmol). Flash chromatography (n-hexane:ethyl acetate¼ 95:5) afforded 0.56 g 3j

Synthesis and Trapping of 1-Bromocyclopropenes
493
(63%) as a colourless oil. IR (film): ꢁꢀ¼ 3061m, 2956s, 2926m, 2870m, 1497w, 1454 m, 1348 m,
1300 m, 1271 w, 1179w, 1105 w, 983 br, 908 m, 754 br, 701 s, 650 m cmꢁ1 1H NMR (400MHz;
;
CDCl3; Me4Si): ꢂ ¼ 0.84 (6H, t, J ¼ 6.7 Hz, 2ꢄCH3), 0.94–1.04 (1H, m), 1.50–1.63 (2H, m), 1.79
(1H, d, J ¼ 6.3 Hz), 2.94 (1H, d, J ¼ 6.3 Hz), 7.21–7.28 (3H, m), 7.33–7.44 (7H, m), 7.74–7.76 (2H,
m), 7.83–7.86 (2H, m) ppm; 13C NMR (100MHz; CDCl3; Me4Si): ꢂ ¼ 22.7 (CH3), 22.8 (CH3), 26.1
(CH), 28.2 (CH2), 35.5 (C), 36.5 (CH2), 50.3 (CBr), 90.1 (CO), 90.4 (CO), 121.9 (CH), 122.7 (CH),
126.1 (CH), 126.2 (CH), 128.22 (2ꢄCH), 128.23 (2ꢄCH), 128.6 (2ꢄCH), 128.80 (CH), 128.82
(CH), 129.1 (2ꢄCH), 133.6 (C), 134.6 (C), 147.0 (C), 147.9 (C) ppm; MS (EI): m=z (%) ¼
446=444 (Mþ, 2=2), 403=401 (11=11), 365 (Mþꢁ Br, 100), 270 (30), 105 (83), 77 (32); HRMS
(EI): m=z calcd. for Mþꢁ Br, C27H25Oþ, 365.1905; found 365.1923.
2-Bromo-4-tert-butyl-8-oxa-1,5-diphenyl-6,7-benzotricyclo[3.2.1.02,4]octane (3k, C27H25OBr)
The synthesis was carried out with 0.84 g 1k (2.50 mmol), 1.70 cm3 MeLi (1.50 M, 2.55mmol), and
0.54g DPIBF (2.00 mmol). TLC indicated that at least three compounds were formed, but flash
chromatography (n-hexane:ethyl acetate ¼ 97.5:2.5) afforded only 0.29¼ g 3k (33%) as a colourless
oil. This was recrystallized (n-hexane) to give white crystals, mp 145–146ꢂC. IR (KBr): ꢁꢀ¼ 3059m,
3036 m, 2958 s, 2909 m, 2872m, 1452m, 1396w, 1364 w, 1342w, 1292 m, 1203 w, 1151w, 1004 w,
979 m, 905 br, 874 w, 756 s, 698 brcmꢁ1
;
1H NMR (400MHz; CDCl3; Me4Si): ꢂ ¼ 0.83 (9H, s,
3ꢄCH3), 2.17 (1H, d, J ¼ 6.2 Hz), 3.04 (1H, d, J ¼ 6.2 Hz), 7.31–7.46 (9H, m), 7.70–7.72 (1H, m),
7.78–7.80 (2H, m), 7.85–7.87 (2H, m) ppm; 13C NMR (100 MHz; CDCl3; Me4Si): ꢂ ¼ 28.8 (CH2),
31.0 (3ꢄCH3), 32.0 (C), 43.8 (C), 49.2 (CBr), 89.6 (CO), 90.9 (CO), 123.2 (CH), 123.8 (CH), 125.8
(CH), 126.3 (CH), 128.2 (2ꢄCH), 128.3 (2ꢄCH), 128.5 (2ꢄCH), 128.8 (CH), 128.9 (CH), 129.5
(2ꢄCH), 133.4 (C), 136.5 (C), 147.4 (C), 148.6 (C) ppm; MS (EI): m=z (%) ¼ 446=444 (Mþ, 3=3),
390=388 (10=10), 365 (Mþꢁ Br, 66), 270 (37), 105 (100), 77 (24), 57 (81); HRMS (EI): m=z calcd. for
Mþꢁ Br, C27H25Oþ, 444.1089; found 444.1090.
General Procedure for the Formation and Trapping of 2 with Cyclopentadiene
The cyclopropane 1 was dissolved in 40 cm3 THF in a round-bottomed flask, equipped with a con-
denser connected to a N2 inlet. The solution was cooled to ꢁ78ꢂC (acetone=dry-ice or ethyl acetate=
liquid N2). MeLi (1.00–1.20 eq) was added dropwise with magnetic stirring. Stirring was continued at
rt for 1 h, before cyclopentadiene (0.88–0.97 eq) was added at a temperature well below 0ꢂC [6]. The
reactions were monitored by either TLC or GC and quenched with a portion of water. The product 4
was extracted with diethyl ether, the solution was dried (MgSO4), filtrated, and evaporated in vacuo,
and finally 4 was isolated by flash chromatography.
10-Bromotetracyclo[9.2.1.02,9.02,10]tetradec-12-ene (4a, C14H19Br)
The synthesis was carried out with 0.91 g 1a (2.52 mmol), 1.60cm3 MeLi (1.50 M, 2.56mmol), and
0.20cm3 cyclopentadiene (d ¼ 0.80g=cm3, 2.42mmol). TLC and GC indicated that at least four
compounds were formed, but flash chromatography (n-hexane) afforded only 0.47g 4a (72%) as a
colourless oil. IR (film): ꢁꢀ¼ 3061w, 2973 s, 2921s, 2856 s, 1451m, 1356 w, 1323 w, 1250m, 1164 w,
1
1096 w, 1060 br, 1034 w, 948 w, 887 w, 797 w, 736 m cmꢁ1; H NMR (400MHz; CDCl3; Me4Si):
ꢂ ¼ 1.01–1.04 (1H, m), 1.28–1.44 (6H, m), 1.51–1.76 (7H, m), 2.08 (1H, td, J ¼ 7.3 and 1.8Hz),
2.74–2.76 (1H, m), 3.09–3.11 (1H, m), 5.88–5.90 (1H, m, ¼CH), 5.98–6.00 (1H, m, ¼CH) ppm;
13C NMR (100MHz; CDCl3; Me4Si): ꢂ ¼ 26.5 (CH2), 26.8 (CH2), 27.2 (CH2), 27.6 (CH2), 27.9 (CH2),
28.6 (CH2), 28.8 (C), 37.9 (CH), 48.3 (CH), 52.8 (CBr), 56.4 (CH), 58.6 (CH2), 132.5 (¼CH), 134.1
(¼CH) ppm; MS (EI): m=z (%) ¼ 268=266 (Mþ, 2=2), 187 (Mþ ꢁ Br, 41), 145 (14), 131 (22), 117
(44), 105 (49), 91 (100), 79 (57), 67 (69), 55 (41).
2-Bromo-4-phenoxymethyltricyclo[3.2.1.02,4]oct-6-ene (4b, C15H15OBr)
The synthesis was carried out with 1.02 g 1b (2.65 mmol), 2.00 cm3 MeLi (1.50 M, 3.00mmol), and
0.20cm3 cyclopentadiene (d ¼ 0.80g=cm3, 2.42mmol). GC indicated that at least three compounds

494
K. F. S. Alnes and L. K. Sydnes
were formed, but flash chromatography (n-hexane:ethyl acetate ¼ 98:2) afforded only 0.49g 4b (70%)
as a colourless liquid. IR (film): ꢁꢀ¼ 3063 w, 2982m, 2937m, 2866w, 1599s, 1495s, 1388s, 1367s,
1300 m, 1240 s, 1172 m, 1033 s, 856 w, 752s, 691 s cmꢁ1; 1H NMR (400MHz; CDCl3; Me4Si): ꢂ ¼ 1.35
(1H, dd, J ¼ 6.6 and 2.5 Hz), 1.59 (1H, dd, J ¼ 6.6 and 1.1 Hz), 1.81–1.84 (1H, m), 2.35–2.38 (1H, m),
3.05–3.07 (1H, m), 3.14–3.16 (1H, m), 4.20 (1H, d, J ¼ 10.0Hz, OCH), 4.30 (1H, d, J ¼ 10.0Hz,
OCH), 6.01–6.07 (2H, m, HC¼CH), 6.91–6.98 (3H, m, Ph), 7.25–7.32 (2H, m, Ph) ppm; 13C NMR
(100 MHz; CDCl3; Me4Si): ꢂ ¼ 28.5 (C), 33.6 (CH2), 43.7 (CBr), 47.3 (CH), 54.5 (CH), 60.6 (CH2),
72.4 (OCH2), 114.7 (2ꢄCH), 120.8 (CH), 129.3 (2ꢄCH), 133.2 (¼CH), 135.2 (¼CH), 159.0 (C)
ppm; MS (EI): m=z (%) ¼ 292=290 (Mþ, 2=2), 198=196 (21=21), 117 (100), 91 (44), 77 (37); HRMS
(EI): m=z calcd. for Mþ, C15H15OBrþ, 290.0306; found 290.0326. After a couple of months in the
freezer, white crystals were formed and isolated by filtration, mp 38–39ꢂC.
2-Bromo-4-(4-methylphenoxy)methyltricyclo[3.2.1.02,4]oct-6-ene (4c, C16H17OBr)
The synthesis was carried out with 1.00 g 1c (2.51 mmol), 2.00cm3 MeLi (1.50 M, 3.00mmol), and
0.20cm3 cyclopentadiene (d ¼ 0.80g=cm3, 2.42mmol). GC indicated that at least five compounds
were formed, but flash chromatography (n-hexane:ethyl acetate ¼ 95:5) afforded only 0.55 g 4c (74%)
as a light yellow oil. IR (film): ꢁꢀ¼ 3063 w, 2982m, 2935 m, 2865 m, 1613 w, 1585w, 1512 s, 1458 w,
1388 w, 1290m, 1237s, 1175 w, 1099 w, 1026 s, 856 w, 814 s, 742 m, 717w cmꢁ1; 1H NMR (400MHz;
CDCl3; Me4Si): ꢂ ¼ 1.33 (1H, dd, J ¼ 6.6 and 2.6 Hz), 1.57 (1H, dd, J ¼ 6.6 and 1.0 Hz), 1.79–1.82
(1H, m), 2.28 (3H, s, CH3), 2.34–2.36 (1H, m), 3.03–3.06 (1H, m), 3.12–3.15 (1H, m), 4.16 (1H, d,
J ¼ 10.0Hz, OCH), 4.26 (1H, dd, J ¼ 10.0 and 1.1 Hz, OCH), 6.00–6.02 (1H, m, ¼CH), 6.03–6.05
(1H, m, ¼CH), 6.83–6.87 (2H, m, 2ꢄCH), 7.07–7.09 (2H, m, 2ꢄCH) ppm; 13C NMR (100MHz;
CDCl3; Me4Si): ꢂ ¼ 20.4 (CH3), 28.5 (C), 33.5 (CH2), 43.6 (CBr), 47.3 (CH), 54.4 (CH), 60.5 (CH2),
72.6 (OCH2), 114.5 (2ꢄCH), 129.7 (2ꢄCH), 129.9 (C), 133.2 (¼CH), 135.1 (¼CH), 156.9 (C) ppm;
MS (EI): m=z (%) ¼ 306=304 (Mþ, 4=4), 198=196 (25=25), 117 (100), 108 (83), 91 (64), 77 (28);
HRMS (EI): m=z calcd. for Mþ, C16H17OBrþ, 304.0463; found 304.0465.
2-Bromo-4-phenyltricyclo[3.2.1.02,4]oct-6-ene (4d, C14H13Br)
The synthesis was carried out with 0.96g 1d (2.71 mmol), 2.00cm3 MeLi (1.50 M, 3.00mmol),
and 0.20cm3 cyclopentadiene (d ¼ 0.80 g=cm3, 2.42 mmol). GC indicated that at least six compounds
were formed, but flash chromatography (n-hexane) afforded only 0.34g 4d (54%) as a colourless oil.
IR (film): ꢁꢀ¼ 3061m, 2979s, 2870 w, 1600 w, 1498m, 1448 m, 1321m, 1255m, 1101 m, 1058m,
1
1014 m, 899 w, 856 m, 761 m, 741 s, 698 s cmꢁ1; H NMR (400 MHz; CDCl3; Me4Si): ꢂ ¼ 1.78 (2H,
br s, CH2), 1.91–1.93 (1H, m), 2.62–2.64 (1H, m), 3.05–3.07 (1H, m), 3.24 (1H, m), 6.08–6.10 (1H, m,
¼CH), 6.17–6.19 (1H, m, ¼CH), 7.23–7.40 (5H, m, Ph) ppm; 13C NMR (100MHz; CDCl3; Me4Si):
ꢂ ¼ 32.6 (CH2), 33.2 (C), 46.9 (CBr), 52.1 (CH), 54.7 (CH), 61.0 (CH2), 126.4 (CH), 128.1 (2ꢄCH),
128.3 (2ꢄCH), 134.6 (¼CH), 135.7 (¼CH), 140.2 (C) ppm; MS (EI): m=z (%) ¼ 262=260 (Mþ, 6=6),
181 (Mþꢁ Br, 100), 77 (30); HRMS (EI): m=z calcd. for Mþꢁ Br, C14H13þ, 181.1017; found 181.1008.
2-Bromo-4-(2-phenylethyl)tricyclo[3.2.1.02,4]oct-6-ene (4e, C16H17Br)
The synthesis was carried out with 0.96 g 1e (2.51 mmol), 1.70cm3 MeLi (1.50 M, 2.55 mmol), and
0.20cm3 cyclopentadiene (d ¼ 0.80 g=cm3, 2.42mmol). TLC and GC indicated that at least seven
compounds were formed. Purification by flash chromatography (n-hexane) afforded 0.39g 4e (56%)
as a colourless liquid (Rf ¼ 0.22). IR (film): ꢁꢀ¼ 3063m, 3025m, 2967 s, 2931s, 2861 m, 1603w,
1495 m, 1449 m, 1357 w, 1321 m, 1256m, 1121w, 1091m, 1048m, 1027m, 959 w, 900 br, 856 m,
795 w, 742 s, 701 s cmꢁ1; 1H NMR (200 MHz; CDCl3; Me4Si): ꢂ ¼ 0.96 (1H, dd, J ¼ 6.3 and 2.5Hz),
1.35 (1H, dd, J ¼ 6.3 and 1.4 Hz), 1.68–1.74 (1H, m), 1.81–2.14 (2H, m, CH2), 2.17 (1H, td, J ¼ 7.3
and 1.7 Hz), 2.61–2.66 (1H, m), 2.65–2.91 (2H, m, CH2), 3.07–3.12 (1H, m), 5.85–5.89 (1H, m,
¼CH), 5.95–6.00 (1H, m, ¼CH), 7.13–7.32 (5H, m, Ph) ppm; 13C NMR (50 MHz; CDCl3; Me4Si):
ꢂ ¼ 28.7 (C), 33.6 (CH2), 34.6 (CH2), 35.9 (CH2), 46.7 (CBr), 48.1 (CH), 54.7 (CH), 59.8 (CH2), 125.7
(CH), 128.2 (2ꢄCH), 128.4 (2ꢄCH), 132.8 (¼CH), 135.0 (¼CH), 141.9 (C) ppm; MS (EI):

Synthesis and Trapping of 1-Bromocyclopropenes
495
m=z (%) ¼ 290=288 (Mþ, 1=1), 209 (Mþꢁ Br, 10), 117 (31), 105 (21), 91 (100), 77 (12), 65 (19), 51
(10); HRMS (EI): m=z calcd. for Mþ, C16H1781Brþ, 290.0493; found 290.0500.
In addition 0.07 g 1-bromo-2-(2-phenylethyl)cyclopropene (2e, 13%) were isolated as a light
yellow liquid (Rf ¼ 0.34). IR (film): ꢁꢀ¼ 3062w, 3027 m, 2963s, 2926s, 2880s, 1836 w, 1603 w,
1
1495 m, 1451 m, 1078 w, 1034 s, 746 m, 699 s cmꢁ1; H NMR (200MHz; CDCl3; Me4Si): ꢂ ¼ 1.55
(2H, t, J ¼ 0.5 Hz, CH2), 2.70–2.96 (4H, m, 2ꢄCH2), 7.16–7.35 (5H, m, Ph) ppm; 13C NMR (50 MHz;
CDCl3; Me4Si): ꢂ ¼ 17.2 (CH2), 27.3 (CH2), 32.4 (CH2), 92.9 (C), 117.1 (C), 126.1 (CH), 128.2
(2ꢄCH), 128.3 (2ꢄCH), 140.7 (C) ppm; MS (EI): m=z (%) ¼ 224=222 (Mþꢁ C5H6, 1=1), 143
(Mþꢁ C5H6-Br, 40), 128 (25), 105 (5), 91 (100), 77 (6), 65 (20), 51 (42); HRMS (EI): m=z calcd.
for Mþ, C11H11Brþ, 222.0044; found 222.0028.
2-Bromo-4-propyltricyclo[3.2.1.02,4]oct-6-ene (4f, C11H15Br)
The synthesis was carried out with 0.80 g 1f (2.49 mmol), 1.70 cm3 MeLi (1.50 M, 2.55mmol), and
0.20cm3 cyclopentadiene (d ¼ 0.80 g=cm3, 2.42 mmol). According to TLC at least eight products were
formed, but flash chromatography (n-hexane) yielded only 0.12 g 4f (22%) as a colourless liquid. IR
(film): ꢁꢀ¼ 3063 m, 2962s, 2931 s, 2869s, 1456 m, 1377 w, 1322w, 1268 w, 1245w, 1074m, 995 w,
1
898 w, 857 w, 738 m cmꢁ1; H NMR (200MHz; CDCl3; Me4Si): ꢂ ¼ 0.88–1.01 (5H, m), 1.34–1.76
(5H, m), 2.17 (1H, td, J ¼ 7.3 and 1.7 Hz), 2.71–2.76 (1H, m), 3.07–3.12 (1H, m), 5.89–5.94 (1H, m,
¼CH) and 5.97–6.02 (1H, m, ¼CH) ppm; 13C NMR (50 MHz; CDCl3; Me4Si): ꢂ ¼ 14.2 (CH3), 21.4
(CH2), 28.7 (C), 33.6 (CH2), 35.8 (CH2), 46.7 (CBr), 48.1 (CH), 54.7 (CH), 59.7 (CH2), 132.7 (¼CH),
135.1 (¼CH) ppm; MS (EI): m=z (%) ¼ 228=226 (Mþ, 3=3), 185=183 (16=16), 147 (Mþꢁ Br, 80), 117
(40), 105 (96), 91 (100), 77 (48), 51 (34); HRMS (EI): m=z calcd. for Mþ, C11H15Brþ, 226.0357;
found 226.0369.
2-Bromo-4-pentyltricyclo[3.2.1.02,4]oct-6-ene (4g, C13H19Br)
The synthesis was carried out with 0.87 g 1g (2.50 mmol), 2.35cm3 MeLi (1.27 M, 2.98 mmol),
0.21cm3 cyclopentadiene (d ¼ 0.80g=cm3, 2.42mmol). TLC indicated that at least five compounds
were formed, but flash chromatography (n-hexane) afforded only 0.18 g 4g (29%) as a colourless
liquid. IR (film): ꢁꢀ¼ 3064m, 2960 s, 2927s, 2860 s, 1456 s, 1375 w, 1322m, 1256 m, 1081 s, 1052m,
1
1015 m, 898 m, 858 m, 800 w, 735 cmꢁ1; H NMR (200MHz; CDCl3; Me4Si): ꢂ ¼ 0.87 (4H, m),
1.30–1.62 (8H, m), 1.65–1.79 (2H, m), 2.14–2.19 (1H, m, CH), 2.70–2.75 (1H, m, CH), 3.07–3.12
(1H, m, CH), 5.89–5.93 (1H, m, ¼CH), 5.97–6.01 (1H, m, ¼CH) ppm; 13C NMR (50 MHz; CDCl3;
Me4Si): ꢂ ¼ 14.0 (CH3), 22.6 (CH2), 27.8 (CH2), 28.8 (C), 31.9 (CH2), 33.6 (CH2), 33.7 (CH2), 46.8
(CBr), 48.0 (CH), 54.7 (CH), 59.7 (CH2), 132.7 (¼CH), 135.1 (¼CH) ppm; MS (EI): m=z
(%) ¼ 256=254 (Mþ, 6=6), 185=183 (23=23), 175 (Mþꢁ Br, 65), 117 (44), 105 (100), 91
(96), 77 (40), 55 (48); HRMS (EI): m=z calcd. for Mþꢁ Br, C13H19þ, 175.1487; found 175.1486.
2-Bromo-4-octyltricyclo[3.2.1.02,4]oct-6-ene (4h, C16H25Br)
The synthesis was carried out with 0.99 g 1h (2.53 mmol), 1.70 cm3 MeLi (1.50 M, 2.55mmol), and
0.20cm3 cyclopentadiene (d ¼ 0.80 g=cm3, 2.42 mmol). According to TLC and GC at least five com-
pounds were formed. Purification by flash chromatography (n-hexane) afforded 0.25g 4h (35%) as a
colourless liquid (Rf ¼ 0.73). IR (film): ꢁꢀ¼ 3064w, 2973s, 2926 s, 2856 s, 1458m, 1374 w, 1321 w,
1
1255 w, 1085 w, 1051w, 1034 w, 897 w, 857 w, 737 m cmꢁ1; H NMR (200 MHz; CDCl3; Me4Si):
ꢂ ¼ 0.85–1.00 (5H, m), 1.29–1.75 (6H, m), 2.14–2.19 (1H, m), 2.71–2.74 (1H, m), 3.08–3.11 (1H,
m), 5.89–5.93 (1H, m, ¼CH), 5.97–6.01 (1H, m, ¼CH) ppm; 13C NMR (50 MHz; CDCl3; Me4Si):
ꢂ ¼ 14.0 (CH3), 22.6 (CH2), 28.2 (CH2), 28.9 (C), 29.2 (CH2), 29.5 (CH2), 29.7 (CH2), 31.8 (CH2), 33.6
(CH2), 33.7 (CH2), 46.8 (CBr), 48.1 (CH), 54.8 (CH), 59.8 (CH2), 132.7 (¼CH), 135.1 (¼CH) ppm;
MS (EI): m=z (%) ¼ 298=296 (Mþ, 9=9), 217 (Mþꢁ Br, 64), 185=183 (29=29), 117 (43), 105 (100),
91 (84), 77 (28), 57 (42); HRMS (EI): m=z calcd. for Mþ, C16H2581Brþ, 298.1119; found 298.1119.
In addition 0.23g 1-bromo-2-octylcyclopropene (2h, 39%) were isolated as a light yellow liquid
(Rf ¼ 0.90). IR (film): ꢁꢀ¼ 2927 s, 2857 s, 1836 w, 1461m, 1375 w, 1259w, 1106 w, 1033m, 804 w,

496
K. F. S. Alnes and L. K. Sydnes
1
722 w cmꢁ1; H NMR (200 MHz; CDCl3; Me4Si): ꢂ ¼ 0.85–0.92 (3H, m, CH3), 1.28–1.43 (10H, m,
5ꢄCH2), 1.52 (2H, t, J ¼ 0.5 Hz, CH2), 1.53–1.62 (2H, m, CH2), 2.42 (2H, t, J ¼ 7.0 Hz, CH2) ppm;
13C NMR (50 MHz; CDCl3; Me4Si): ꢂ ¼ 14.0 (CH3), 17.1 (CH2), 22.6 (CH2), 25.3 (CH2), 26.2 (CH2),
29.1 (CH2), 29.2 (2ꢄCH2), 31.7 (CH2), 92.1 (C), 117.9 (C) ppm; MS (EI): m=z (%) ¼ 151 (Mþꢁ Br,
11), 134=132 (18=18), 109 (21), 95 (59), 81 (49), 67 (46), 55 (78), 41 (100).
2-Bromo-4-cyclohexymethyltricyclo[3.2.1.02,4]oct-6-ene (4i, C15H21Br)
The synthesis was carried out with 0.96 g 1i (2.56 mmol), 1.70 cm3 MeLi (1.50 M, 2.55 mmol), and
0.21cm3 cyclopentadiene (d ¼ 0.80 g=cm3, 2.42mmol). TLC indicated that at least three compounds
were formed. Purification by flash chromatography (n-hexane) afforded 0.13g 4i (19%) as a colourless
liquid (Rf ¼ 0.62). IR (film): ꢁꢀ¼ 3062 w, 2923 br, 2850 s, 1448 m, 1321 w, 1257 w, 1078 br, 1006 w,
966 w, 902 w, 857 w, 738 m cmꢁ1; 1H NMR (200MHz; CDCl3; Me4Si): ꢂ ¼ 1.03 (1H, dd, J ¼ 6.3 and
2.4 Hz), 1.07–1.39 (5H, m), 1.42 (1H, dd, J ¼ 6.3 and 1.7 Hz), 1.69–1.78 (9H, m), 2.13–2.18 (1H, m),
2.71–2.76 (1H, m), 3.07–3.12 (1H, m), 5.91–5.95 (1H, m, ¼CH), 5.97–6.02 (1H, m, ¼CH) ppm;
13C NMR (50 MHz; CDCl3; Me4Si): ꢂ ¼ 26.2 (CH2), 26.3 (CH2), 26.5 (CH2), 27.1 (C), 32.9 (CH2),
34.0 (CH2), 34.1 (CH2), 37.6 (CH), 40.9 (CH2), 46.7 (CBr), 48.7 (CH), 54.8 (CH), 59.6 (CH2), 132.8
(¼CH), 134.9 (¼CH) ppm; MS (EI): m=z (%) ¼ 282=280 (Mþ, 5=5), 201 (Mþꢁ Br, 12), 185=183
(8=8), 117 (29), 105 (70), 91 (37), 55 (100); HRMS (EI): m=z calcd. for Mþꢁ Br, C15H21þ, 201.1643;
found 201.1650.
In addition two by-products, 1-bromo-2-(cyclohexylmethyl)cyclopropene (2i, 0.19g, 35%) and 1-
bromo-4-cyclohexylbut-2-yne (0.03 g, 5%) were also isolated (Rf ¼ 0.79 and 0.42). 2i: IR (film):
ꢁꢀ¼ 2924 s, 2852 s, 1834w, 1711 br, 1615 w, 1447 m, 1266m, 1210 m, 1076 w, 1032s, 956 w, 908w,
736 br, 687 w cmꢁ1; 1H NMR (400MHz; CDCl3; Me4Si): ꢂ ¼ 0.96–1.32 (5H, m), 1.51 (2H, t, J ¼ 0.5 Hz,
CH2), 1.57–1.75 (6H, m), 2.32 (2H, d, J ¼ 6.6 Hz) ppm; 13C NMR (50 MHz; CDCl3; Me4Si): ꢂ ¼ 17.3
(CH2), 26.07 (2ꢄCH2), 26.13 (CH2), 32.99 (2ꢄCH2), 33.03 (CH2), 36.0 (CH), 92.6 (C), 117.1 (C) ppm;
MS (EI): m=z (%) ¼ 135 (Mþꢁ Br, 16), 105 (14), 91 (23), 67 (94), 55 (100).
1-Bromo-4-cyclohexylbut-2-yne: IR (film): ꢁꢀ¼ 2923 s, 2851s, 2249 w, 1448 m, 1211m,
1
607 m cmꢁ1; H NMR (200MHz; CDCl3; Me4Si): ꢂ ¼ 0.86–1.82 (11H, m), 2.13 (2H, td, J ¼ 2.4 and
6.6 Hz, CH2), 3.94 (2H, t, J ¼ 2.4 Hz, (CH2)Br) ppm; 13C NMR (50 MHz; CDCl3; Me4Si): ꢂ ¼ 15.8
(CH2), 26.0 (2ꢄCH2), 26.1 (CH2), 26.6 (CH2), 32.5 (2ꢄCH2), 37.0 (CH), 76.0 (C), 87.2 (C) ppm; MS
(EI): m=z (%) ¼ 216=214 (Mþ, 0.3=0.3), 135 (Mþꢁ Br, 26), 107 (6), 93 (17), 83 (98), 67 (24), 55 (100).
2-Bromo-4-isobutyltricyclo[3.2.1.02,4]oct-6-ene (4j, C12H17Br)
The synthesis was carried out with 0.83 g 1j (2.49 mmol), 1.70 cm3 MeLi (1.50 M, 2.55mmol), and
0.20cm3 cyclopentadiene (d ¼ 0.80g=cm3, 2.42mmol). TLC and GC indicated that at least four
compounds were formed, but purification by flash chromatography (n-hexane) afforded only 0.15g
4j (26%) as a colourless oil. IR (film): ꢁꢀ¼ 3063 m, 2958br, 2871s, 2841 m, 1462m, 1366w, 1324m,
1
1249 w, 1081 br, 1004 w, 956 w, 901 w, 856m, 738m cmꢁ1; H NMR (200MHz; CDCl3; Me4Si):
ꢂ ¼ 0.90 (3H, d, J ¼ 6.5 Hz, CH3), 0.97 (3H, d, J ¼ 6.3 Hz, CH3), 1.04 (1H, dd, J ¼ 6.3 and 2.5Hz),
1.25–1.38 (1H, m), 1.44 (1H, dd, J ¼ 6.3 and 1.6 Hz), 1.68–1.86 (3H, m), 2.16 (1H, td, J ¼ 7.3 and
1.7 Hz), 2.73–2.78 (1H, m), 3.08–3.13 (1H, m), 5.90–5.95 (1H, m, ¼CH), 5.98–6.03 (1H, m, ¼CH)
ppm; 13C NMR (50 MHz; CDCl3; Me4Si): ꢂ ¼ 22.2 (CH3), 23.4 (CH3), 27.6 (C), 28.1 (CH), 34.1
(CH2), 42.2 (CH2), 46.5 (CBr), 48.6 (CH), 54.8 (CH), 59.6 (CH2), 132.8 (¼CH), 134.9 (¼CH) ppm;
MS (EI): m=z (%) ¼ 242=240 (Mþ, 3=3), 185=183 (14=14), 161 (Mþꢁ Br, 20), 117 (53), 105 (100), 91
(67), 77 (40), 57 (39); HRMS (EI): m=z calcd. for Mþ, C12H17Brþ, 240.0514; found 240.0500.
Reaction with 1k
The synthesis was carried out with 0.85 g 1k (2.54 mmol), 1.70 cm3 MeLi (1.50 M, 2.55mmol), and
0.20cm3 cyclopentadiene (d ¼ 0.80 g=cm3, 2.42 mmol). TLC and GC indicated that at least nine
compounds were formed. Purification by flash chromatography (n-hexane) yielded a colourless oil
(0.10 g, Rf ¼ 0.63). NMR analysis proved that this was a mixture of 1k, and the endo and exo isomers

Synthesis and Trapping of 1-Bromocyclopropenes
497
of 2-bromo-4-tert-butyltricyclo[3.2.1.02,4]oct-6-ene (4k) in a 3:6:1 ratio. Thus, the combined yield
of the endo and exo isomers of 4k is 12%. The cyclopropane ring protons in 1k give rise to two
1
doublets at 1.90 and 2.21ppm in the H NMR spectrum, while the two multiplets at 5.75–5.98 and
5.88–6.04ppm are due to the vinylic protons in the endo and exo isomers of 4k, respectively.
General Procedure for the Formation and Trapping of 1-Bromocyclopropenes with Furan
Cyclopropane 1 and furan (ꢅ10 eq) were dissolved in 40 cm3 THF in a round-bottomed flask, equipped
with a condenser connected to a N2 inlet. The solution was cooled to ꢁ78ꢂC (acetone=dry-ice or ethyl
acetate=liquid N2). MeLi (1.01–1.13 eq) was added dropwise with a syringe with magnetic stirring.
The reactions were monitored by either TLC or GC and quenched with a portion of water. The product
5 was extracted with diethyl ether, the solution was dried (MgSO4), filtrated, and evaporated in vacuo,
and finally 5 was isolated by flash chromatography.
Reaction with 1a
The synthesis was carried out with 0.95 g 1a (2.63 mmol), 2.00cm3 MeLi (1.50 M, 3.00mmol), and
2.00cm3 furan (d ¼ 0.94g=cm3, 27.61 mmol). Evaporation in vacuo afforded 0.47g 9-bromobicyclo-
[6.1.0]non-1(9)-ene (2a, 100%) as a yellow oil [19, 42, 43]. IR (film): ꢁꢀ¼ 2924s, 2855s, 1702m,
1
1452 s, 1348 w, 1319 w, 1237 w, 1059 m, 1019m, 862 w, 754 w, 671w cmꢁ1; H NMR (400MHz;
CDCl3; Me4Si): ꢂ ¼ 1.19–1.67 (9H, m), 1.79–1.88 (1H, m), 2.12–2.23 (2H, m), 2.70 (1H, ddd,
J ¼ 14.7, 5.7 and 3.9 Hz) ppm; 13C NMR (100 MHz; CDCl3; Me4Si): ꢂ ¼ 19.7 (CH2), 24.7 (CH2),
24.97 (CH2), 24.99 (CH2), 29.0 (CH), 29.4 (CH2), 30.5 (CH2), 97.1 (C), 123.4 (C) ppm; MS (EI):
m=z (%) ¼ 202=200 (Mþ, 25=25), 121 (Mþꢁ Br, 21), 105 (11), 93 (74), 91 (42), 79 (100), 67 (38).
2-Bromo-8-oxa-4-phenoxymethyltricyclo[3.2.1.02,4]oct-6-ene (5b, C14H13O2Br)
The synthesis was carried out with 0.96 g 1b (2.50 mmol), 1.70 cm3 MeLi (1.50 M, 2.55mmol), and
2.00cm3 furan (d ¼ 0.94 g=cm3, 27.61 mmol). According to TLC and GC at least eight compounds
were formed, but only 0.23 g 5b (31%) were isolated by flash chromatography (n-hexane:ethyl
acetate ¼ 98:2) as a colourless oil. This was characterised as pure exo isomer, because of the large
difference in the chemical shift of the doublet and double doublet at 1.44 and 2.41ppm, which were
assigned to the H atoms in the cyclopropane moiety. In addition impure endo isomer (0.11 g, 15%) was
isolated. This was not pure enough to obtain satisfying spectra, but in the 1H NMR spectrum a doublet
at 1.76 ppm (J ¼ 6.9 Hz) and a double doublet at 1.86ppm (J ¼ 6.9 and 1.4Hz) were assigned to the H
atoms in the cyclopropane moiety. Exo-5b: IR (film): ꢁꢀ¼ 3062w, 3006m, 2916 w, 2869w, 1594s,
1494 s, 1467 m, 1429 w, 1392m, 1295 s, 1237 br, 1174 m, 1132 m, 1081m, 1030s, 919 s, 886 m, 873s,
821 w, 782 w, 754 s, 692 cmꢁ1; 1H NMR (400MHz; CDCl3; Me4Si): ꢂ ¼ 1.44 (1H, d, J ¼ 6.4 Hz), 2.41
(1H, dd, J ¼ 6.4 and 1.3 Hz), 3.95 (1H, d, J ¼ 10.5Hz, OCH), 4.05 (1H, dd, J ¼ 10.5 and 1.3 Hz), 4.84
(1H, d, J ¼ 1.5 Hz), 4.91 (1H, d, J ¼ 1.5 Hz), 6.67 (1H, dd, J ¼ 5.7 and 1.5 Hz, ¼CH), 6.72 (1H, dd,
J ¼ 5.7 and 1.5 Hz, ¼CH), 6.89–6.98 (3H, m, Ph), 7.25–7.30 (2H, m, Ph) ppm; 13C NMR (50 MHz;
CDCl3; Me4Si): ꢂ ¼ 29.4 (CH2), 34.4 (C), 44.8 (CBr), 69.6 (OCH2), 79.0 (OCH), 81.4 (OCH), 114.4
(2ꢄCH), 121.0 (CH), 129.3 (2ꢄCH), 138.6 (¼CH), 139.5 (¼CH), 158.5 (C) ppm; MS (EI): m=z
(%) ¼ 294=292 (Mþ, 4=4), 213 (Mþꢁ Br, 3), 91 (100), 77 (20), 65 (26).
2-Bromo-4-(4-methylphenoxy)methyl-8-oxatricyclo[3.2.1.02,4]oct-6-ene (5c, C15H15O2Br)
The synthesis was carried out with 1.04 g 1c (2.61 mmol), 2.00cm3 MeLi (1.50 M, 3.00 mmol), and
2.00cm3 furan (d ¼ 0.94 g=cm3, 27.61 mmol). TLC and GC indicated that at least six compounds were
formed. Purification by flash chromatography (n-hexane:ethyl acetate¼ 97.5:2.5) afforded 0.38 g 5c
(49%) as a colourless oil (Rf ¼ 0.16). This was characterised as pure exo isomer on the same grounds as
1
for 5b. Traces of the endo isomer were observed in the H NMR spectrum of the crude product as a
doublet at 1.75 ppm (J ¼ 6.9 Hz) and a double doublet at 1.85 ppm (J ¼ 6.9 and 1.4Hz), which were
assigned to the H atoms in the cyclopropane moiety. Isolation efforts were unsuccessful. Exo-5c: IR
(film): ꢁꢀ¼ 3004m, 2919m, 2866 w, 1612 m, 1587w, 1512 s, 1464m, 1433 w, 1391 m, 1293s, 1235 br,

498
K. F. S. Alnes and L. K. Sydnes
1179 m, 1127m, 1028 s, 920 br, 871 s, 815 s, 753 w, 702 m, 614w cmꢁ1; 1H NMR (400MHz; CDCl3;
Me4Si): ꢂ ¼ 1.44 (1H, d, J ¼ 6.3 Hz), 2.28 (3H, s, CH3), 2.41 (1H, dd, J ¼ 6.3 and 1.3 Hz), 3.94 (1H,
d, J ¼ 10.5 Hz, OCH), 4.04 (1H, dd, J ¼ 10.5 and 1.3 Hz, OCH), 4.84 (1H, d, J ¼ 1.7 Hz), 4.92 (1H,
d, J ¼ 1.5 Hz), 6.68 (1H, dd, J ¼ 5.8 and 1.7 Hz, ¼CH), 6.74 (1H, dd, J ¼ 5.8 and 1.5 Hz, ¼CH),
6.80–6.83 (2H, m, 2ꢄCH), 7.07–7.09 (2H, m, 2ꢄCH) ppm; 13C NMR (100 MHz; CDCl3; Me4Si):
ꢂ ¼ 20.4 (CH3), 29.5 (CH2), 34.5 (C), 44.8 (CBr), 69.9 (OCH2), 79.1 (CO), 81.4 (CO), 114.4 (2ꢄCH),
129.8 (2ꢄCH), 130.3 (C), 138.7 (¼CH), 139.5 (¼CH), 156.5 (C) ppm; MS (EI): m=z (%) ¼ 308=306
(Mþ, 8=8), 201=199 (4=4), 108 (26), 91 (100), 77 (15); HRMS (EI): m=z calcd. for Mþ, C15H15O2Brþ,
306.0255; found 306.0252.
In addition 0.08g impure 1-bromo-2-[(4-methylphenoxy)methyl]cyclopropene (2b, 13%) were
isolated as a yellow oil (Rf ¼ 0.34). 13C NMR (100 MHz; CDCl3; Me4Si): ꢂ ¼ 9.2 (CH2), 20.4 (CH3),
63.9 (OCH2), 105.9 (C), 110.8 (C), 114.5 (2ꢄCH), 129.7 (2ꢄCH), 129.8 (C), 156.1 (C) ppm.
Reaction with 1d
The synthesis was carried out with 0.89 g 1d (2.51 mmol), 1.70 cm3 MeLi (1.50 M, 2.55mmol), and
2.00cm3 furan (d ¼ 0.94g=cm3, 27.61 mmol). The brown crude product consisted of at least four
compounds according to TLC. NMR analyses indicated that two compounds were 1-(3-bromoprop-
1-ynyl)benzene and 1-(1-bromopropa-1,2-dienyl)benzene (in a 2:3 ratio). The acetylene gives rise to a
singlet at 4.05 ppm, which is assigned to the methylene group. The same group in the allene gives rise
to a singlet at 5.29ppm. Efforts to isolate the products were unsuccessful.
Reaction with 1e
The synthesis was carried out with 0.96 g 1e (2.51 mmol), 1.70cm3 MeLi (1.50 M, 2.55 mmol), and
2.00cm3 furan (d ¼ 0.94g=cm3, 27.61 mmol). The yellow crude product was 0.54 g essentially pure 2e
(96%), but some was lost during purification by flash chromatography (n-hexane). The spectroscopic
data were identical to those given above.
Reaction with 1f
The synthesis was carried out with 0.80 g 1f (2.51 mmol), 1.70 cm3 MeLi (1.50 M, 2.55mmol), and
2.00cm3 furan (d ¼ 0.94 g=cm3, 27.61 mmol). Evaporation in vacuo afforded an orange liquid (0.42 g)
which according to TLC consisted of at least five compounds. Isolation of the compounds by flash
chromatography (n-hexane:ethyl acetate ¼ 97.5:2.5) was not successful.
Reaction with 1g
The synthesis was carried out with 0.87 g 1g (2.49 mmol), 1.70cm3 MeLi (1.50 M, 2.55mmol), and
2.00cm3 furan (d ¼ 0.94 g=cm3, 27.61 mmol). Evaporation in vacuo afforded an orange liquid (0.65 g)
which according to TLC consisted of at least four compounds. Purification by flash chromatography
1
(n-hexane) yielded a colourless oil (0.42 g) which according to H NMR consisted of some 1-bro-
mooct-2-yne and 3-bromoocta-1,2-diene (in a 1:30 ratio). The acetylene gives rise to a singlet at
4.11ppm, which are assigned to the methylene group at C1; the same group in the allene gives rise
to a singlet at 5.00ppm. However, isolation efforts were unsuccessful.
Reaction with 1h
The synthesis was carried out with 0.98 g 1h (2.51 mmol), 1.70 cm3 MeLi (1.50 M, 2.55mmol), and
2.00cm3 furan (d ¼ 0.94 g=cm3, 27.61 mmol). Evaporation in vacuo afforded an orange liquid (0.60 g)
which according to TLC consisted of at least five compounds. Purification by flash chromatography
(n-hexane) afforded 0.13 g 1-bromoundec-2-yne (6) (22%) and 0.10 g 3-bromoundeca-1,2-diene (7)
(17%) as colourless oils (Rf ¼ 0.44 and 0.70).
6: IR (film): ꢁꢀ¼ 2926 s, 2857s, 2249 w, 1461m, 1374 w, 1330w, 1212m cmꢁ1
;
1H NMR
(400 MHz; CDCl3; Me4Si): ꢂ ¼ 0.87–0.90 (3H, m, CH3), 1.28–1.40 (10H, m, 5ꢄCH2), 1.47–1.54
(2H, m, CH2), 2.21–2.26 (2H, m, CH2), 3.93 (2H, t, J ¼ 2.4 Hz, (CH2)Br) ppm; 13C NMR (100MHz;

Synthesis and Trapping of 1-Bromocyclopropenes
499
CDCl3; Me4Si): ꢂ ¼ 14.0 (CH3), 15.7 (CH2), 18.8 (CH2), 22.5 (CH2), 28.3 (CH2), 28.7 (CH2), 28.9
(CH2), 29.0 (CH2), 31.7 (CH2), 75.1 (C), 88.2 (C) ppm; MS (EI): m=z (%) ¼ 175=173 (Mþꢁ Bu, 4=4),
109 (26), 95 (100), 81 (54), 67 (43), 55 (43), 41 (44).
1
7: IR (film): ꢁꢀ¼ 2927 s, 2857 s, 1460m, 1376w, 1255w, 1117w, 1049w, 962 w, 867m cmꢁ1; H
NMR (400MHz; CDCl3; Me4Si): ꢂ ¼ 0.88 (3H, t, J ¼ 6.9 Hz, CH3), 1.28–1.34 (10H, m, 5ꢄCH2),
1.48–1.55 (2H, m, CH2), 2.36–2.41 (2H, m, CH2), 4.82 (2H, t, J ¼ 3.2 Hz, ¼CH2) ppm; 13C NMR
(100 MHz; CDCl3; Me4Si): ꢂ ¼ 14.0 (CH3), 22.5 (CH2), 27.7 (CH2), 28.4 (CH2), 29.10 (CH2), 29.14
(CH2), 31.7 (CH2), 37.1 (CH2), 81.1 (¼CH2), 93.1 (¼CBr), 203.9 (C) ppm; MS (EI): m=z (%) ¼ 151
(Mþꢁ Br, 14), 134=132 (44=44), 109 (40), 95 (83), 81 (68), 67 (57), 55 (84), 41 (100).
Reaction with 1i
The synthesis was carried out with 0.93 g 1i (2.48 mmol), 1.60 cm3 MeLi (1.60 M, 2.56 mmol), and
2.00cm3 furan (d ¼ 0.94g=cm3, 27.61 mmol). The orange crude product was 0.52 g essentially pure 2i
(74%), but some was lost during purification by flash chromatography (n-hexane:ethyl acetate ¼ 98:2).
The spectroscopic data were consistent with previous analyses.
Reaction with 1j
The synthesis was carried out with 0.83 g 1j (2.48 mmol), 1.70 cm3 MeLi (1.50 M, 2.55mmol), and
2.00cm3 furan (d ¼ 0.94g=cm3, 27.61 mmol). Evaporation in vacuo afforded a yellow liquid (0.52g)
which according to TLC consisted of at least four compounds. However, purification by flash chro-
matography (n-hexane:ethyl acetate ¼ 98:2) was unsuccessful.
Reaction with 1k
The synthesis was carried out with 0.84 g 1k (2.49 mmol), 1.60 cm3 MeLi (1.60 M, 2.56mmol), and
2.00cm3 furan (d ¼ 0.94 g=cm3, 27.61 mmol). Evaporation in vacuo afforded an orange liquid (0.64 g)
which according to TLC consisted of at least four compounds. However, purification by flash chro-
matography (n-hexane:ethyl acetate ¼ 98:2) was unsuccessful.
Acknowledgements
Financial support from Norsk Hydro is gratefully acknowledged. Thanks are also due to A. M. Wyhatt,
University of Bergen, and D. Ekeberg, Norwegian University of Life Sciences, for recording the mass
spectra.
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