Conjugated and Cross-Conjugated ?-Extended Cycloproparanes with dithiole and Cyclopentadiene Functionality

Full text of DOI:10.1002/ejoc.200300619

FULL PAPER
Conjugated and Cross-Conjugated π-Extended Cycloproparenes with Dithiole
and Cyclopentadiene Functionality
Brian Halton*[a] and Carissa S. Jones[a]
Keywords: Small ring systems / Arenes / Hydrocarbons / Sulfur heterocycles / Peterson olefination / WittigϪHorner
reactions / Strained molecules
Dithiole and cyclopentadiene rings have been introduced
into functionalised cyclopropa[b]naphthalenes to provide
tones with 1,1-bis(trimethylsilyl)cyclopropa[b]naphthalene
10 gives the π-extended cycloproparenes 27 and 29 in
highly coloured, conjugated and cross-conjugated π-ex- Peterson olefinations that are more efficient than
tended derivatives that have varying stability. Cyclo- Wittig−Horner reactions of cyclopropanthraquinone 31 with
pentadienylidene-containing cyclopropanaphthalene 18 and
dithiolate 24 to give the cross-conjugated cycloproparenes 34
its dithiolylidene analogue 25 are prepared from bromophen- and 35.
ylcyclopropanaphthalene 12, and the 1,1-biscyclopentadien- ( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
ylidene 20 from dibromide 13. Use of dithiole-containing ke-
Germany, 2004)
Introduction
tives,[1,7] fluorescent compounds,[6,8,9] and, with some, the
ability to form charge-transfer complexes.[10] These features
suggest that the cycloproparene frame could behave as a
valuable template for electronic effects from inclusion of ex-
tended π-conjugation.
The class of strained aromatic hydrocarbons known as
the cycloproparenes, and illustrated by parent 1H-cyclopro-
pabenzene 1 has provided much fascinating chemistry[1]
since Anet and Anet[2] reported the first authenticated de-
rivative in 1964. The benzylic nature of the C1 protons, with
a measured[3] pKa for 1 (ca. 36) has led to use[4] of the C1
cycloproparenyl anion (e.g. 2) in routine syntheses to give
exocyclic alkenes (e.g. 5) from Peterson olefinations
(Scheme 1).[5Ϫ8] Because of the notable malodour of vol-
atile 1, the bulk of the studies have employed crystalline
cyclopropa[b]naphthalene 6 to provide a wide range of ex-
amples[1] (e.g. 11) that now encompass ‘‘push-pull’’ deriva-
The generation of the cyclopentadienyl anion as the elec-
tron sink in ‘‘push-pull’’ π-conjugated systems forms a cor-
nerstone of physical-organic chemistry and therefore, the
physical and chemical properties of tetrathiafulvene (TTF)
derivatives have been extensively explored.[11] While the
TTF core has been modified, particularly by way of quino-
noid spacers,[12] much less attention has been devoted to
compounds that carry just one dithiole unit, even though
they form charge transfer (CT) complexes with comparable
properties to those derived from TTF.[13] Since strained
molecules incorporating modified TTF or dithioles are even
rarer,[14] it became evident that the incorporation of cyclo-
pentadiene and dithiole into cycloproparenes carrying exo-
cyclic π-conjugation should be examined. Here, we provide
details on the cyclopentadienylidene-containing cyclopro-
parenes 18 and 20, and the dithiole derivatives 25, 27, 29,
and the cross-conjugated dithioles 33 and 34.
Results and Discussion
By employing the reaction sequence of Scheme 1, shelf-
stable disilane[1,7] 10 was obtained for subsequent use. Pet-
erson olefination of this with p-bromo- and p,pЈ-dibromo-
benzophenone gave the previously unknown exocyclic al-
kenes 12 (R1 ϭ p-BrC6H4, R2 ϭ Ph) and 13 (R1 ϭ R2 ϭ
p-BrC6H4; Scheme 2) in isolated yields of 90 and 94 % as
bright yellow and lustrous orange crystals, respectively. As
Scheme 1
[a]
School of Chemical & Physical Sciences, Victoria University
of Wellington,
P. O. Box 600, Wellington, New Zealand
138
 2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
DOI: 10.1002/ejoc.200300619
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Cross-Conjugated π-Extended Cycloproparenes
FULL PAPER
alkylidenecycloproparenes are stable to base,[1] halogen- discernible resonances in the range δ ϭ 107Ϫ152 ppm. Of
lithium exchange is easily accomplished, and under anaer- these twelve are quaternary and C2(C7) are not differen-
obic conditions a solution of 14 was formed from 11 and tiated but appear as a shielded[1] singlet at δ ϭ 107.5 ppm.
nBuLi. Subsequent reaction of this with N,N-dimethyl- Unfortunately, only small ‘‘push-pull’’ character could be
benzamide gave the benzoyl derivative 15 (77 %) together inferred from the shifts (ca. 3Ϫ4 nm) in absorption maxima
with a small amount of the known[15] un-substituted on changing the UV-Vis solvent from nonpolar to polar
hydrocarbon 16 (Scheme 2).
(Exp. Sect.). Furthermore, compound 18 was obtained as
a powder that did not provide crystals suitable for X-ray
structural analysis.
Attempts to prepare the cyclopentadiene-containing 18
and its bromine-containing homologue 19 from bromides
12 and 13, respectively, were also devised following pro-
cedures developed by Oda et al.[18] They found that the in-
termediate derived from addition of an organolithium to an
amide can be intercepted directly by cyclopentadiene to give
a 6,6-disubstituted pentafulvalene through in situ formation
of the ketone and cyclopentadienyl anion (Scheme 3). In-
deed, this procedure is most efficacious because in our lab-
oratory 6,6-diphenylpentafulvalene was prepared in good
yield (65 %) from lithiation of bromobenzene followed by
the addition of N,N-dimethylbenzamide and then cyclopen-
tadiene.[18] When applied to monobromide 12, the reaction
produced a complex mixture of at least ten products from
which radial chromatography afforded a red oil (RF, 0.5) the
spectroscopic data for which clearly showed the presence of
Scheme 2
The formation of 15 follows from a classical ‘‘addition- 18 (vide supra); all attempts to isolate a pure sample led to
elimination’’ reaction between lithiate 14 and an amide-car- product decomposition.
bonyl group, while the formation of hydrocarbon 16 is con-
sistent only with protonation of the reactive intermediate
14, which is likely to occur during workup rather than with
residual water in the reaction medium.[4] It is important that
atmospheric oxygen be excluded from the reaction appar-
atus otherwise oxygenation of the lithiate takes place[16]
with subsequent formation of the phenol 17 (20 %) that is
accompanied by hydrocarbon 16 (40 %); specific aeration
of a solution of lithiate 14 followed by workup affords 16
and 17 in yields of 33 and 20 %, respectively (Exp. Sect.).
With the exception of reactive 14, the structures of the
alkylidenecycloproparenes 12؊17 are assigned with confi-
dence from their analytical and spectroscopic data. In par-
Scheme 3
Dibromide 13 with 1 molar equivalent of nBuLi (as re-
ticular, shielding of the C2(C7) carbon atoms in the 13C quired for the preparation of monocyclopentadiene-con-
NMR spectra matches expectation.[1] It is notable that ben- taining 19) and cyclopentadiene also provided a complex
zoyl derivative 15 occludes dichloromethane and is hygro- mixture containing about ten components. In this case rad-
scopic. It forms a 2:1 complex with water which provided ial chromatography provided a bright orange oil (RF, 0.5)
1
appropriate analytical data.
but the H NMR spectrum indicated not 19, but the bis-
Reaction of ketone 15 with the cyclopentadienyl anion cyclopentadiene derivative 20 (Scheme 2) since the H2(H7)
was accomplished following literature procedures[17] and signal appears as a distinct singlet (δ ϭ 7.65 ppm) in a ratio
produced the π-extended pentafulvalenyl cycloproparene 18 of 1:1:1:2 with the three types of cyclopentadienylidene pro-
(31 %) (Scheme 2) that also occludes solvent. The 1H NMR tons (δ ϭ 6.32Ϫ6.36, 6.48Ϫ6.52, and 6.63Ϫ6.70 ppm). At-
spectrum shows the olefinic cyclopentadienyl protons as tempts to purify the product resulted in significant de-
three distinct 1:1:2 multiplets as expected from their non- composition and only after routine chromatography, separ-
equivalence [δ ϭ 6.32Ϫ6.34 (1H), 6.49Ϫ6.51 (1H), and ation over the size-exclusion gel Sephadex-LH-20TM, and
6.63Ϫ6.69 (2H) ppm]. The remote H3(H6) signal of the further radial chromatography could a pure sample be ob-
cyclopropanaphthalene appears as a clearly discernible two- tained for analysis (1 % yield). The marked sensitivity of
proton AAЈ multiplet, and H2(H7) reflects the facial asym- this compound to the conditions of purification deterred us
metry appearing as para-coupled one-proton doublets (δ ϭ from subsequent attempts to gain further samples of it or,
7.59 and 7.63 ppm, J ϭ 1.6 Hz). The 13C NMR spectrum indeed, the search for the monocyclopentadienyl-containing
of unsymmetrical 18 is complex and displays twenty-one analogue 19.
Eur. J. Org. Chem. 2004, 138Ϫ146
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139

B. Halton, C. S. Jones
FULL PAPER
The incorporation of a dithiole moiety into an organic
ketone is now achieved comparatively easily by
WittigϪHorner olefination using carbanion 24 as described
by Moore and Bryce.[19] This essential anion is generated
readily by metallation of phosphonate ester 23 with n-butyl-
lithium at low temperatures and, in turn, ester 23 is pre-
pared from commercially available vinylene trithiocarbon-
ate 21 (Scheme 4) in four steps through 22 in 66 % overall
yield. In order to test the efficacy of the WittigϪHorner
reaction with anion 24, its reaction with benzophenone was
repeated whereupon olefination was achieved in 74 % yield
(Scheme 4), somewhat higher than the literature value.[19]
Scheme 5
Table 1. Electronic absorption data for DDQ, 25, and 25·DDQ
(1:2); recorded at ambient temperature on a HewlettϪPackard
8452A diode-array spectrophotometer for acetonitrile solutions
Compound
λmax (nm)
DDQ
25
25 ϩ DDQ (1:2)
272, 280, 372
230, 275, 294 sh, 441
252, 347, 436, 540Ϫ620 (broad)
is the appearance of a weak long wavelength absorption[20]
and, indeed 25·DDQ (1:2) has such a broad absorption
band in the range 540Ϫ620 nm, viz. at markedly longer
wavelengths than the absorption maxima of the individual
components. Attempts to isolate the solid CT complex were
unsuccessful and decomposition took place at Ϫ16 °C over-
night.
An alternative strategy for incorporating novel π-electron
donors into the cycloproparene frame would involve the
Peterson olefination of α-silyl anion 9 with a carbonyl-
containing compound already carrying a dithiole moiety,
for example, the known[19] anthronedithiolylidene 26 to give
the linear π-extended alkylidenecycloproparene 27
(Scheme 6). Synthon 26 is available from the WittigϪ
Horner olefination of anthraquinone by phosphonate ester
24 but it is obtained in only low (10 %) yield as the bis-
adduct dominates.[19] An alternative preparation uses the
dithiolium salt 22 (Scheme 4) and anthrone, which upon re-
flux in pyridine and acetic acid provides the sought after 26
in 85 % yield (Scheme 6).[21]
Scheme 4
Reaction of benzoylcycloproparene 15 with 24 likewise
resulted in an efficient olefination of the carbonyl group
and the novel π-extended dithiole-containing cyclopropar-
ene 25 was isolated in 66 % yield as a bright rust coloured
powder that is both light and acid sensitive; it too occludes
1
solvent. The aromatic region of the H NMR spectrum in-
tegrates for the twenty protons expected. Of these a single
one-proton para-coupled doublet (δ ϭ 7.54 ppm, J ϭ
1.8 Hz) for H2 or H7 is clearly visible as is the two-
proton AAЈ component of an AAЈBBЈ spin system
[7.86Ϫ7.90 ppm, H3(H6)]. Importantly, the two nonequiva-
lent vinyl protons of the newly incorporated dithiole ring
appear as doublets [δ ϭ 6.24 and 6.28 ppm, J ϭ 6.6 Hz].
The 13C NMR spectrum has 25 of the expected 28 reson-
ances distinguishable with the C2(C7) carbon atoms shi-
elded and at δ ϭ 107.0(6) and 107.1(6) ppm. The assigned
resonances compare well with those of (diphenylmethylid-
ene)cyclopropanaphthalene 16 but with the C1 and C3(C6)
methine carbon signals slightly shifted upfield. The mole-
cule is presumed to be stabilised by charge separation
throughout as indicated in Scheme 5.
The good yield in which 25 was obtained provided suf-
ficient material to assess its ability to act as a donor and
form a CT salt with an appropriate electron acceptor. In
the event, a MeCN solution of 25 gave an instantaneous
colour change from red/yellow to dark green when two mo-
lar equivalents of DDQ were added. The electronic absorp-
tion spectrum of the green solution showed the absorption
bands of donor 25 and acceptor DDQ to be replaced by
new absorptions (Table 1). Characteristic of CT formation Scheme 6
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Cross-Conjugated π-Extended Cycloproparenes
FULL PAPER
Treatment of ketone 26 with anion 9 gave a complex mix- extended derivative in which a simple alkene extends the
ture of products, the separation of which led to a red resi- conjugation.[1]
due. This produced analytically pure dark red/black needles
The WittigϪHorner reaction between lithiate 24 and
of the sought after alkylidenecycloproparene 27 carrying naphthoquinone[23] 30 failed to provide any evidence for
the anthrylidene spacer, but only in 6 % yield and this could either the mono- or bis-substituted derivatives 32 and 33
1
not be improved upon in subsequent experiments. The H (Scheme 7) despite many variations in the reaction con-
NMR spectrum of 27 matches the symmetrical structure as ditions. By way of contrast, the reactions of 24 with cyclo-
it shows a four-proton AAЈBBЈ spin system [δ ϭ 7.89Ϫ7.92 propanthraquinone[24] 31 led to the mono- and bis(dithiole)
and 7.47Ϫ7.50 ppm for H3(H6)and H4(H5), respectively] containing cross-conjugated cyclopropanthracenes 34
with the H2(H7) and H20(H21) methine protons of the di- (23 %) and 35 (23 %), the former from employing equimo-
thiole ring as two-proton singlets (δ ϭ 7.65 and 6.28 ppm, lar quantities of reagents and the latter from reaction with
respectively); the 13C NMR spectrum displays the respective 2 molar equivalents of 24. Dithiole 34 was isolated as a rust
carbon atom signals at δ ϭ 107.8 (C2 and C7) and 117.1 coloured powder of near analytical quality characterised
(C20 and C21) ppm. The low yields of 27 have precluded a from the protonated molecular ion in the APCI mass spec-
1
detailed examination of its physicochemical properties al- trum. The H NMR spectrum is fully compatible with the
though one flake showed packing in highly ordered sheet- structure and the influence of the dithiole ring is notable in
like arrays from attempted single-crystal analysis. Each that H2 and H9 resonate as well separated para-coupled
sheet has the molecules of 27 aligned parallel to one an- doublets (δ ϭ 8.10 and 7.81 ppm, J ϭ 1.8 Hz), while the
other with the dithiole moiety continuing the bending from vinylic dithiole protons appear as a two-proton singlet (δ ϭ
the plane that contains the cycloproparene Adjacent sheets 6.42 ppm). The benzylic hydrogen atoms appear as a singlet
are stacked such that a molecule in one layer holds its
neighbour in the next layer in a ‘‘ying-yang’’ or ‘‘fireman’s
grip’’ array, but with the molecules offset so as to maximise
the S···S interactions. Although the crystal data obtained
were far from an acceptable accuracy for deposition they
adequately described the crystal packing present in the
structure.[22] This is illustrated in Figure 1 which employs
the 6Ϫ31G** energy minimised structure.
In separate experiments, the monodithiole 28 derived
from 1,2-diphenylethanone was prepared, and it provided
the linear π-extended cycloproparene 29 (Scheme 6) but,
once again, the compound is available only in low (13%)
yield and it is sensitive to light, acid, and the chromato-
graphic adsorbants used in its separation. This butadiene-
containing cycloproparene 29 is the first example of a π- Scheme 7
Figure 1. Packing in the sheets of dithiole 20
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141

B. Halton, C. S. Jones
FULL PAPER
(δ ϭ 3.39 ppm) in marked contrast to homologue 35 (vide pose over 24 hours in solution, within one week in the solid
infra); the assumed nonplanar saddle-like shape[25] of 34 state, or when left in a well-lit room. This and the low yield-
must be inverting rapidly in CDCl3 solvent at room tem- ing syntheses have precluded any further examination of
perature to equate the methylene protons.
their properties.
It seems clear that a range of conjugated and cross-conju-
The 13C NMR spectrum of cyclopropanthracene 34 also
fits nicely with the assigned structure with the diagnostic gated alkylidenecycloproparenes beyond those described
C2(C9) carbon atoms adjacent to the three-membered ring here should be capable of synthesis. However, the poor
shielded at δ ϭ 113.0 and 113.8 ppm; the APCI mass spec- product yields and the limited stability of most of the com-
trum provides an appropriate protonated molecular ion. At- pounds described here imply that little is to be gained from
tempts were made to grow crystals of 34 suitable for an X- such work. We are continuing our investigations upon the
ray analysis and, while significant decomposition took characteristics of specifically targeted novel π-extended
place, a few truncated cones were obtained, but no diffrac- cycloproparenes and will report upon these studies in due
tion patterns were observed.[22]
course.
Bis(dithiole) 35 (23 %) was isolated from the reaction of
31 with two molar equivalents of 24 as an unstable yellow
powder that decomposed upon attempted purification; 35
Experimental Section
1
General: Microanalyses were performed by the Analytical Facility,
Otago University, Dunedin. Mr. O. Zubkov recorded the mass
spectra with high resolution coming from a PE Biosystems Mariner
5158 TOF spectrometer operating in electrospray mode, and Elec-
tron Impact (EI) 70 eV data from a HewlettϪPackard 5995C in-
is sensitive to both acid and light. However, the H NMR
spectrum of the somewhat impure sample, clearly showed
the expected AAЈBBЈ spin system (δ ϭ 7.68Ϫ7.73,
7.29Ϫ7.32 ppm) for H3(H6) and H4(H5), and a two-proton
singlet for H2(H) at δ ϭ 7.65 ppm. The formally nonequiv-
alent vinylic protons of the dithiole moiety are unaffected
by the remote cyclopropa-fusion and resonate as a broad
singlet at δ ϭ 6.27 ppm that compares well with that in the
analogous product from anthraquinone (δ ϭ 6.30 ppm).[19]
1
strument. H and 13C NMR spectra were recorded with a Varian
Unity INOVA 300 MHz spectrometer with deuterated chloroform
using the residual solvent peak as internal standard. 31P NMR
spectra were recorded on the same instrument using 10 % phos-
phoric acid in D2O as internal standard (δ ϭ 0.00 ppm). The usual
The most notable feature of the spectrum is the nonequival- notations define NMR multiplicities and coupling constants are in
1
Hertz. The assignment of 13C and H NMR resonances was made
ence of the C1 geminal protons which resonate as a pair of
one-proton doublets at δ ϭ 3.14 and 3.60 ppm (J ϭ
with the aid of DEPT and 1H-1H COSY and 13C-1H HSQC experi-
ments, and heteronuclear multiple-bond connectivity (HMBC)
4.2 Hz). This must arise from the adoption of a nonplanar,
experiments. IR spectra of solid samples were recorded with KBr
saddle conformation in which the two 1,3-dithiole rings as-
disks using a Biorad FTS 7 spectrophotometer while UV-Vis spec-
sume a U-shape with the bridging ring, such that the steric
tra were measured on a HewlettϪPackard 8452A diode-array spec-
repulsions between the sulfur atoms and the C2(C4) and
trophotometer. Melting points were determined with a Reichert
hot-stage melting point apparatus and are uncorrected. Thin-layer
chromatographic analyses were performed using Merck Kieselgel
C7(C9) peri-hydrogen atoms of the cyclopropanthracene
moiety are minimised (Figure 2).[25] In turn, this causes the
nonequivalence of the C1 methylene protons, such that
(Alufoilen) 60F254 to a thickness of 0.2 mm and components de-
boat-to-boat inversion to equate hydrogen atoms (Ha and tected under a UV lamp at 254 or 350 nm. Radial chromatography
plates were coated with silica gel DGF254 to a thickness of 1, 2, 3,
Hb) is slow in CDCl3 on the NMR time scale (25 °C).
or 4 mm, and the total amount of material loaded onto the plate
was 0.25 g, 0.75 g, 1.12 g, and 1.5 g, respectively. Column chroma-
tography employed Kieselgel 60 (230Ϫ400 ASTM) as the station-
ary phase unless otherwise stated. Solvents were purified before use
according to the procedures given in Perrin, Armarego, and Per-
rin.[26]
General Method for the Synthesis of Alkylidene-1H-cyclopropa[b]-
naphthalenes: A solution of freshly sublimed potassium tert-butox-
ide (1 equiv.) in anhydrous THF (ca. 10 mL) was added dropwise
by a syringe needle to a cooled solution (Ϫ70 °C) of disilane[8] 10
Figure 2. Minimum energy conformers of bis(dithiole) 35
(1 equiv.) and the carbonyl compound (1 equiv.), in THF (ca.
10 mL) under a nitrogen atmosphere. The mixture was stirred at
Ϫ70 °C for 1 h then warmed to ambient temperature overnight.
The reaction was quenched (water/dichloromethane, 1:1; 50 mL)
The 13C NMR spectrum of 35 shows C2(C9) shielded
(δ ϭ 113.1 ppm) as expected,[1] and distinct signals for the
aromatic methines C4(C7) and C5(C6) (δ ϭ 124.8 and
125.9 ppm); the nonequivalence of the dithiole C4Ј and C5Ј
and the organic phase extracted with dichloromethane (3 ϫ
is only just detectable [δ ϭ 117.0(3) and 117.0(5) ppm]. 20 mL). The combined organic extracts were washed (water; 3 ϫ
20 mL), dried (MgSO4), filtered, and concentrated under reduced
pressure to give a crude product that was purified as described.
These last three resonances have essentially the same chemi-
cal shifts as those in the parent anthracene analogue (δ ϭ
124.9, 125.9, and 117.1 ppm).[19] Importantly, the APCI
mass spectrum provides a protonated molecular ion (m/z ϭ
392.9890) that confirms the composition. Unfortunately,
1-[(p-Bromophenyl)phenylmethylidene]-1H-cyclopropa[b]naphthalene
(12): A stirred solution of disilane 10 (284 mg, 1 mmol)[8] and p-
bromobenzophenone (261 mg, 1 mmol) in dry THF (10 mL) gave
the dithiole-containing cycloproparenes 34 and 35 decom- a bright yellow oil which on trituration (hexane, Ϫ16 °C) afforded
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Cross-Conjugated π-Extended Cycloproparenes
FULL PAPER
1-[(p-bromophenyl)phenylmethylidene]-1H-cyclopropa[b]naph-
H and 17-H or 25-H), 7.75Ϫ7.79 (m, 2 H), 7.88Ϫ7.96 (m, 8 H)
thalene (12). Yield 345 mg, 90 %. Bright yellow needles, m.p.
ppm. 13C NMR (75 MHz, CDCl3): δ ϭ 107.9 (C2 or C7), 108.0
1
100Ϫ101 °C. H NMR (300 MHz, CDCl3): δ ϭ 7.37 (apparent tt, (C2 or C7), 113.7 (C1), 118.5 (C8), 126.8, 127.0 (CH), 127.5 (CH),
J ϭ 7.3, 1.6 Hz, 1 H, 18-H), 7.44Ϫ7.51 (m, 4 H, 4-H/5-H and 17-
127.6 (C17 or C25), 128.2 (CH), 128.3 (CH), 128.6 (CH), 128.9
H/19-H), 7.53Ϫ7.63 (m, 6 H, 2-H/7-H, 10-H/14-H, and 11-H/13- (CH), 130.0 (CH), 130.5 (CH), 132.3 (C25 or C17), 135.3, 135.9,
H), 7.70Ϫ7.74 (m, 2 H, 16-H/20-H), 7.86Ϫ7.89 (m, 2 H, 3-H/6-H) 137.9, 138.8, 138.9, 139.0, 143.9, 196.1 (C13) ppm. HRMS (positive
ppm. 13C NMR (75 MHz, CDCl3): δ ϭ 107.4(7) (C2 or C7), APCI) calcd. for C31H21O [M ϩ H]ϩ 409.1587; found 409.1565
107.6(0) (C7 or C2), 112.3 (Cl), 118.5 (C8), 121.1 (C12), 126.9(0)
(Ϫ5.4 mmu). IR (KBr): ν˜ ϭ 3049, 2923, 1774, 1650, 1594, 1444,
(C4/C5), 126.9(4) (Cla or C7a), 126.9(9) (C7a or Cla), 127.6 (C18), 1346, 1314, 1277, 1174, 1135, 936, 923, 850, 763, 747, 698, 664
128.1 (C16/C20), 128.6 (C17/C19), 128.8 (C3/C6), 129.7 (C10/C14 cmϪ1. UV-Vis (hexane) (log ε) λmax ϭ 230 (4.99), 260 (4.93), 278
or C11/C13), 131.6 (C11/C13 or C10/C14), 138.5 (C9), 138.7(9)
(4.95), 422 (4.81), 446 nm (4.80); (acetonitrile) (log ε) λmax ϭ 230
(C2a or C6a), 138.8(1) (C6a or C2a), 139.0 (C15) ppm. MS (70 eV): (5.09), 260 (4.91), 280 (4.79), 423 (4.99), 442 nm (4.97).
m/z (%) ϭ 385 (16) [C24H1581Br ϩ 1], 384 (63) [C24H1581Br], 382 C31H20O·0.85 CH2Cl2 (480.39): calcd. C 79.5, H 4.3; found C 79.0,
(57) [C24H1579Br], 304 (10), 303 (37) [M Ϫ Br], 302 (100) [M Ϫ
H 4.6. Pulverising the sample and placing it under high vacuum
HBr], 301 (18), 300 (47), 298 (10), 151 (19), 150 (19). IR (KBr): gave hemihydrate 1-(p-benzoylphenyl)phenylmethylidene-1H-
ν˜ ϭ 3036, 3007, 1777, 1588, 1478, 1443, 1418, 1345, 1136, 1069,
cyclopropa[b]naphthalene·0.5·H2O. Yellow powder, m.p. 66Ϫ69 °C.
1009, 841, 760, 748, 741, 698 cmϪ1. UV-Vis (hexane) (log ε) λmax ϭ C31H20O·0.5H2O (417.2) calcd. C 89.2, H 5.1; found C 89.4, H, 5.0.
230 (4.71), 276 (4.47), 292 sh (4.27), 412 (4.62), 438 nm (4.64);
Preparation of 1-[(p-Hydroxyphenyl)phenylmethylidene]-1H-cyclo-
propa[b]naphthalene (17) from Lithiate 14 and Oxygen: n-Butyllith-
ium (2.5 , 0.1 mL, 0.26 mmol) was added to a stirred solution of
12 (100 mg, 0.26 mmol) in dry THF (2 mL) at Ϫ78 °C under argon.
The dark mixture was stirred for 1 h then 10 mL of air was injected
into the flask. After warming to ambient temperatures overnight,
(acetonitrile) (log ε) λmax ϭ 230 (4.73), 273 (4.49), 288 sh (4.36),
412 (4.64), 435 nm (4.65). C24H15Br (383.02): calcd. C 75.2, H
3.9(5), Br 20.8(5); found C 75.4, H 3.7(5), Br 20.7.
1-[Bis(p-bromophenyl)methylidene]-1H-cyclopropa[b]naphthalene
(13): A stirred solution of 10 (500 mg, 1.76 mmol)[8] and p,pЈ-di-
bromobenzophenone (598 mg, 1.76 mmol) in THF (20 mL) gave a the mixture was poured into a mixture of water/dichloromethane
bright orange solid which upon trituration (hexane, Ϫ16 °C) af-
forded 1-[bis(p-bromophenyl)methylidene]-1H-cyclopropa[b]naph-
thalene (13). Yield 759 mg, 94 %. Lustrous orange crystals, m.p.
193Ϫ194 °C. 1H NMR (300 MHz, CDCl3): δ ϭ 7.50Ϫ7.53 (BBЈ, 2
(100 mL; 1:1), the phases were separated, and the organic layer was
washed (water, 2 ϫ 25 mL), dried (MgSO4), and concentrated un-
der reduced pressure to produce an orange oil. Radial chromatog-
raphy (light petroleum elution) gave hydrocarbon 16. Yield 26 mg,
H, 4-H/5-H), 7.59 (broad s, 10 H, 2-H/7-H, 9-H/13-H and 10-H/ 33 %. Bright yellow oil with NMR spectroscopic data identical to
12-H), 7.89Ϫ7.93 (AAЈ, 2 H, 3-H/6-H) ppm. 13C NMR (75 MHz, those of the authentic sample.[27] Further elution (dichloromethane/
CDCl3): δ ϭ 107.8 (C2/C7), 112.6 (C1), 117.3 (C8), 121.3 (C12), light petroleum; 1:1) gave 1-[(p-hydroxyphenyl)phenylmethylidene]-
126.6 (Cla/C7a), 127.1 (C4/C5), 128.9 (C3/C6), 129.5 (C10/C14 or
C11/C13), 131.7 (C11/C13 or C10/C14), 138.0 (C9), 138.9 (C2a/
C6a) ppm. HRMS (positive APCI) calcd. for C24H1579Br2 [M ϩ
1H-cyclopropa[b]naphthalene (17). Yield 17 mg, 20%. Dark green/
brown solid, m.p. 85Ϫ88 °C. 1H NMR (300 MHz, CDCl3): δ ϭ
5.02 (br. s, 1 H, OH), 6.93Ϫ6.97 (m, 2 H, 11-H/13-H), 7.37
Hϩ] 460.9541; found 460.9549 (ϩ1.74 mmu). IR (KBr): ν˜ ϭ 3046, (apparent tt, J ϭ 7.3, 1.7 Hz, 1 H, 18-H), 7.45Ϫ7.52 (m, 6 H, 2-H/
3034, 1777, 1482, 1423, 1392, 1346, 1248, 1176, 1136, 1071, 1005, 7-H, 4-H/5-H and 17-H/19-H), 7.63Ϫ7.68 (m, 2 H, 10-H/14-H),
967, 835, 825, 751, 721, 703 cmϪ1. UV-Vis (cyclohexane) (log ε) 7.74Ϫ7.77 (m, 2 H, 16-H/20-H), 7.86Ϫ7.89 (AAЈ, 2 H, 3-H/6-H)
λmax ϭ 230 (4.68), 276 sh (4.50), 284 (4.53), 414 (4.59), 440 nm
(4.60); (acetonitrile) (log ε) λmax ϭ 230 (4.68), 274 sh (4.49), 281
ppm. 13C NMR (75 MHz, CDCl3): δ ϭ 106.6(8) (C2 or C7),
106.7(1) (C7 or C2), 110.7 (C1), 115.4 (C11/C13), 119.6 (C8),
(4.52), 412 (4.59), 438 nm (4.59). C24H14Br2 (462.9) calcd. C 62.4, 126.5(6) (C4/C5), 126.5(8) (C4/C5), 127.4 (C18), 127.5 (Cla/C7a),
H 3.0(5); found C 62.3, H 3.0.
128.2 (C16/C20), 128.4 (C17/C19), 128.7 (C3/C6), 129.6 (C10/C14),
132.1 (C9), 138.5(8) (C2a or C6a), 138.6(2) (C6a or C2a), 139.6
(C15), 155.0 (C12) ppm. HRMS (positive APCI) calcd. for
C24H15O [M Ϫ H]ϩ 319.1137; found 319.1131 (Ϫ1.88 mmu). IR
(KBr): ν˜ ϭ 3401, 2975, 2953, 1633, 1608, 1445, 1413, 1384, 1267,
1173, 1138, 1089, 1049, 880, 845, 698 cmϪ1. UV-Vis (hexane) (log
ε) λmax ϭ 230 (4.58), 275, (4.28), 413 (4.43), 441 nm (4.50); (aceto-
nitrile) (log ε) λmax ϭ 230 (4.58), 274 (4.29), 275 (4.29), 414 (4.43),
440 nm (4.48).
1-[(p-Benzoylphenyl)phenylmethylidene]-1H-cyclopropa[b]naph-
thalene·0.85 CH2Cl2 (15): n-Butyllithium (2.30 , 0.79 mL,
1.82 mmol) was added to a cooled (Ϫ78 °C) stirred solution of 12
(700 mg, 1.82 mmol) in dry THF (20 mL) under argon. The dark
mixture was stirred and kept at this temperature for 1 h before solid
N,N-dimethylbenzamide (411 mg, 1.82 mmol) was quickly added in
one portion under a steady flow of dry argon. The mixture was
warmed to ambient temperatures overnight, poured into water/di-
chloromethane (200 mL; 1:1), and the phases separated. The or-
1-[10Ј-(6,6-Diphenylpentafulvalenyl)]phenylmethylidene-1H-cyclo-
ganic layer was washed (water, 2 ϫ 50 mL), dried (MgSO4), and propa[b]naphthalene·0.18 C6H14 (18): Cyclopentadiene (0.02 mL,
concentrated under reduced pressure to produce an orange oil.
Radial chromatography (light petroleum elution) provided 1-di-
0.25 mmol) followed by freshly ground potassium hydroxide
(14 mg, 0.25 mmol) was added to stirred solution of p-
a
phenylmethylidene-1H-cyclopropa[b]naphthalene
(16).
Yield
benzoylphenylcyclopropanaphthalene·0.9 CH2Cl2 (15) (100 mg, ca.
0.83 mg unsolvated, ca. 0.20 mmol) and 18-crown-6 (4 mg,
0.01 mmol) in dry THF (10 mL) at 0 °C and under argon. The
dark red mixture was stirred overnight at room temperature and
68 mg, 12 %. Bright yellow oil with NMR spectroscopic data
identical to those of an authentic sample.[27] Further elution (di-
chloromethane/light petroleum; 1:1) gave a yellow residue, recrys-
tallisation of which (diethyl ether) provided 1-[(p-benzoylphe- poured into water/dichloromethane (100 mL; 1:1). After separating
nyl)phenylmethylidene]-1H-cyclopropa[b]naphthalene·0.85 CH2Cl2
the phases the aqueous layer was extracted (dichloromethane, 2 ϫ
25 mL), and the combined organic layers were washed (water; 2 ϫ
(15). Yield 570 mg, 77 %. Bright yellow crystals, m.p. 76Ϫ78 °C. 1H
NMR (300 MHz, CDCl3): δ ϭ 7.41 (apparent tt, J ϭ 7.3, 1.7 Hz, 1 25 mL), dried (MgSO4) and concentrated under reduced pressure
H, 17-H or 25-H), 7.48Ϫ7.56 (m, 6 H), 7.60Ϫ7.65 (m, 3 H, 2-H/7- to a red oil. Radial chromatography (dichloromethane/light petro-
Eur. J. Org. Chem. 2004, 138Ϫ146
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 2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
143

B. Halton, C. S. Jones
leum elution; 4:1) and collection of the only mobile component (m, 4 H, 2Ј-H/3Ј-H), 7.42Ϫ7.48 (m, 14 H, 8Ј-H/12Ј-H, 14Ј-H/18Ј-
FULL PAPER
gave an orange oil that on trituration (dichloromethane/hexane
H, 15Ј-H/17Ј-H and 16Ј-H), 7.49Ϫ7.54 (BBЈ, 2 H, 4-H/5-H), 7.65
(s, 2 H, 2-H/7-H), 7.82Ϫ7.87 (m, 4 H, 9Ј-H/11Ј-H), 7.91Ϫ7.95
Ϫ16 °C) gave 1-[10Ј-(6,6-diphenylpentafulvalenyl)]phenylmethylid-
ene-1H-cyclopropa[b]naphthalene·0.18 C6H14 (18). Yield 30 mg, (AAЈ, 2 H, 3-H/6-H) ppm. 13C NMR (75 MHz, CDCl3): δ ϭ 107.8
31 %; based on the unsolvated alkylidenecyclopropanaphthalene
(C2/C7), 113.3 (C1), 118.4 (C8), 124.3 (C1Ј or C4Ј), 124.5 (C4Ј or
C1Ј), 127.0(3) (C4/C5), 127.0(6) (Cla/C7a), 127.3 (C8Ј/C12Ј, C14Ј/
used. Orange powder, m.p. 122Ϫ124 °C. 1H NMR (300 MHz,
CDCl3): δ ϭ 6.32Ϫ6.34 (m, 1 H, 1Ј-H or 5Ј-H), 6.49Ϫ6.51 (m, 1 C18Ј or C15Ј/C17Ј), 127.7 (C9Ј/C11Ј), 128.7 (C16Ј), 128.9 (C3/C6),
H, 5Ј-H or 1Ј-H), 6.63Ϫ6.69 (m, 2 H, 3Ј-H/H4Ј-H), 7.40Ϫ7.53 (m, 132.1 (C2Ј or C3Ј), 132.2 (C8Ј/C12Ј, C14Ј/C18Ј or C15Ј/C17Ј),
12 H), 7.59 (d, J ϭ 1.6 Hz, 1 H, 2-H or 7-H), 7.63 (d, J ϭ 1.6 Hz,
1 H, 7-H or 2-H), 7.78Ϫ7.84 (m, 4 H), 7.89Ϫ7.93 (AAЈ, 2 H, 3-H/
132.4 (C2Ј or C3Ј), 132.5 (C8Ј/C12Ј or C14Ј/C18Ј or C15Ј/C17Ј),
139.0 (C2a/C6a), 139.7 (C6Ј, C7Ј, C10Ј, C13Ј), 140.2 (C10Ј or C7Ј),
6-H) ppm. 13C NMR (75 MHz, CDCl3): δ ϭ 107.5 (C2/C7), 112.7 141.3 (C6Ј, or C7Ј, or C10Ј, or C13Ј), 143.9 (C5Ј), 151.7 (C7Ј, C6Ј,
(C1), 119.0 (C8), 124.3 (C5Ј or C1Ј), 124.4 (C1Ј or C5Ј), 126.8(4) C 10Ј or C 13Ј) ppm. HRMS (positive APCI) calcd. for C48H33 [M
(CH), 126.8(6) (CH), 127.0, 127.1 (CH), 127.4, 127.5 (CH), 127.7
ϩ H]ϩ 609.2577; found 609.2679 (ϩ16.7 mmu). IR (KBr): ν˜ ϭ
(CH), 128.3 (CH), 128.5 (CH), 128.7(2) (CH), 128.7(9) (CH), 128.9 3052, 2922, 1773, 1584, 1489, 1466, 1442, 1425, 1361, 1347, 1323,
(C3/C6), 132.1 (C3Ј or C4Ј), 132.2 (CH), 132.3 (C4Ј or C3Ј), 132.5 1176, 1137, 1084, 1073, 1029, 1017, 997, 849, 824, 780, 745, 697
(CH), 138.8, 138.9, 139.1, 140.1, 141.3, 143.8, 151.8 ppm. HRMS
cmϪ1. UV-Vis (hexane) (log ε) λmax ϭ 232 (4.83), 257 (4.65), 288
(positive APCI) calcd. for C36H25 [M ϩ H]ϩ 457.1951; found (4.59), 350 (4.51), 444 nm (4.68); (acetonitrile) (log ε) λmax ϭ 232
457.1941 (Ϫ2.19 mmu). IR (KBr): ν˜ ϭ 3049, 2952, 2922, 1776,
1581, 1485 1442, 1360, 1325, 1137, 966, 848, 822, 696 cmϪ1. UV-
Vis (hexane) (log ε) λmax ϭ 232 (4.62) 256 (4.46), 280 (4.42), 346
(4.19), 431 (4.53), 448 nm (4.53); (acetonitrile) (log ε) λmax ϭ 230
(4.68), 254 (4.48), 283 (4.41), 344 (4.25), 437 rim (4.59). Attempts
were made to prepare compound 18 from 12 (550 mg, 1.44 mmol)
and nBuLi (1.92 , 0.78 mL, 1.5 mmol) in dry THF (35 mL) with
N,N-dimethylbenzamide (245 mg, 1.64 mmol) and then cyclopen-
tadiene (0.24 mL, 2.88 mmol) according to the method of Oda et
al.[18] The dark mixture was allowed to attain ambient temperatures
overnight and was then poured into water/dichloromethane
(400 mL; 1:1). The phases were separated and the aqueous mixture
extracted (dichloromethane; 2 ϫ 100 mL) and the combined or-
ganic layers washed (water, 100 mL), dried (MgSO4) and concen-
trated under reduced pressure to produce a red oil. Radial chroma-
tography (dichloromethane/light petroleum elution; 1:4) and collec-
tion of the component with RF ϭ 0.5 afforded a red oil that con-
tained the title compound 18 (1H NMR), vide infra. Attempts to
further purify this oil by radial chromatography, trituration, subli-
mation, or by use of the Sephadex LH-20 size exclusion gel all
resulted in decomposition. The identity of the decomposition prod-
ucts remains unknown.
(4.74), 254 (4.56), 286 (4.51), 337 (4.38), 441 nm (4.58).
Dimethyl (1,3-Dithiol-2-yl)phosphonate (23): This was prepared
from vinylene trithiocarbonate (see Scheme 4) as described pre-
viously.[19,28,29] The pale hygroscopic oil, which became red upon
standing, is best stored under argon in the absence of light.
2-(Diphenylmethylidene)-1,3-dithiole: n-Butyllithium (2.5 , 0.19
mL, 0.47 mmol) was added to a stirred solution of phosphonate
ester 23 (100 mg, 0.47 mmol) in dry THF (20 mL) at Ϫ78 °C under
argon. The suspension was stirred for 30 min at Ϫ78 °C and then
benzophenone (86 mg, 0.47 mmol) was added dropwise in THF
(1 mL) over 5 min. Warming to room temperature overnight was
followed by quenching in water/dichloromethane (100 mL; 1:1).
The phases were separated, the aqueous extracts (dichloromethane,
50 mL), and the combined organic layers were washed (water,
100 mL), dried (MgSO4) and concentrated under reduced pressure
to produce a pale yellow oil. Radial chromatography (dichloro-
methane elution) and collection of the major component followed
by recrystallisation gave the title compound. Yield 93 mg, 74 %.
Cream solid, m.p. 99Ϫ100 °C (ref.[19] 68 %, m.p. Ͼ 240 °C). The
spectroscopic data were in excellent agreement with the literature
values.[19]
1-{Bis[10Ј-(6,6-diphenylpentafulvalenyl)]methylidene}-1H-cyclo- 1-{[10Ј-(6,6-Diphenyl-2,5-dithiapentafulvenyl)]phenylmethylidene}-
propa[b]naphthalene (20): n-Butyllithium (1.92 , 0.52 mL,
1.14 mmol) was added to a stirred solution of dibromide 13
(461 mg, 1.0 mmol) in dry THF (35 mL) at Ϫ78 °C under argon,
which follows the procedure outlined by Oda et al.[18] The mixture
became dark yellow-brown and was stirred at Ϫ78 °C for 1 h, then
N,N-dimethylbenzamide (169 mg, 1.14 mmol) was added under a
1H-cyclopropa[b]naphthalene·0.25 C6H14 (25): n-Butyllithium (1.65
, 0.25 mL, 0.42 mmol) was added to a stirred solution of phos-
phonate ester 23 (88 mg, 0.42 mmol) in dry THF (2 mL), at Ϫ78
°C under argon. The suspension was stirred for 30 min at this tem-
perature and then 20 (in CH2Cl2, 170 mg, 0.45 mmol) was added
dropwise in THF (4 mL) over 5 min. The dark red mixture was
stream of argon. The mixture was warmed, stirred at 0 °C for 1 h warmed to room temperature overnight and then poured into
and then cyclopentadiene (0.17 mL, 2.0 mmol) added. The dark
mixture was then allowed to attain ambient temperatures over-
night, and was then poured into water/dichloromethane (400 mL;
1:1), and the phases separated. The aqueous mixture was extracted
(dichloromethane; 2 ϫ 100 mL) and the combined organic layers
water/dichloromethane (200 mL; 1:1). The phases were separated,
the aqueous phase extracted (dichloromethane, 100 mL), and the
combined organic layers washed (water, 100 mL), dried (MgSO4)
and concentrated under reduced pressure to produce a red/orange
oil. Column chromatography (basic alumina, dichloromethane/
were washed (water, 100 mL), dried (MgSO4) and concentrated un- hexane, 1:4, elution) gave an analytical sample of 1-{[10Ј-(6,6-di-
der reduced pressure to produce an orange oil that contained in
excess of ten components (TLC). Radial chromatography (di-
chloromethane/light petroleum elution; 1:4) and collection of the
band with RF ϭ 0.5 afforded an impure orange solid. Recrystallis-
phenyl-2,5-dithiapentafulvenyl)]phenylmethylidene}-1H-cyclo-
propa[b]naphthalene·0.25 C6H14 (25). Yield 134 mg, 66 %. Bright
red powder, m.p. 69Ϫ70 °C. 1H NMR (300 MHz, CDCl3): δ ϭ 6.24
(d, J ϭ 6.6 Hz, 1 H, 4Ј-H or 5Ј-H), 6.28 (d, J ϭ 6.6 Hz, 1 H, 4Ј-H
ation (dichloromethane, Ϫ16 °C) followed by purification on Se- or 5Ј-H), 7.28Ϫ7.50 (m, 10 H), 7.54 (d, J ϭ 1.8 Hz, 1 H, 2-H or
phadex LH-20TM size-exclusion gel (THF elution) and one further
radial chromatography (dichloromethane elution) gave 20. Yield
7-H), 7.58 (d, J ϭ 1.8 Hz, 1 H, 7-H or 2-H), 7.70Ϫ7.78 (m, 4 H),
7.86Ϫ7.90 (AAЈ, 2 H, 3-H/6-H) ppm. 13C NMR (75 MHz, CDCl3):
δ ϭ 107.0(6) (C2 or C7), 107.1(6) (C7 or C2), 111.8 (C1), 117.4
6 mg, 1 %. Bright orange oil proposed as the title compound 20,
1
b.p. Ͼ 305 °C. H NMR (300 MHz, CDCl3): δ ϭ 6.32Ϫ6.36 (m, 2 (C4Ј or C5Ј), 117.6 (C5Ј or C4Ј), 119.5 (C8), 124.6, 126.7 (C4/C5),
H, 1Ј-H or 4Ј-H), 6.48Ϫ6.52 (m, 2 H, 4Ј-H or 1Ј-H), 6.63Ϫ6.70 127.2 (CH), 127.4 (CH), 127.6, 127.9 (CH), 128.1 (CH), 128.3(5)
144
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Eur. J. Org. Chem. 2004, 138Ϫ146

Cross-Conjugated π-Extended Cycloproparenes
FULL PAPER
(CH), 128.4(3) (CH), 128.7(0) (C3 or C6), 128.7(2) (C6 or C3), sequentially to a mixture of salt 22 (500 mg, 2.11 mmol) and 1,2-
128.9 (CH), 136.5, 137.4, 138.7, 138.8, 139.3, 140.9, 142.8 ppm. diphenylethanone (416 mg, 2.11 mmol) under argon. The mixture
HRMS (positive APCI) calcd. for C34H23S2 [M ϩ H]ϩ 495.1236; was then stirred under reflux for 45 min, cooled, and poured into
found 495.1249 (ϩ2.6 mmu). IR (KBr): ν˜ ϭ 3048, 2951, 1773, 1593,
1487, 1442, 1419, 1345, 1135, 1029, 845, 799, 748, 697 cmϪ1. UV-
Vis (hexane) (log ε) λmax ϭ 230 (4.77), 278 (4.47), 292 sh (4.42),
water/dichloromethane (200 mL; 1:1). The phases were separated,
the aqueous extracted (dichloromethane, 3 ϫ 40 mL), and the com-
bined organic layers were washed (water, 200 mL), dried (MgSO4)
396 sh (4.35), 449 nm (4.62); (acetonitrile) (log ε) λmax ϭ 230 (4.75), and concentrated under reduced pressure to produce a brown oil
1
275 (4.45), 294 sh (4.41), 441 nm (4.59).
that contained (from H NMR examination) a 1:1 mixture of un-
changed ethanone and compound 28. The residue was then dis-
solved in acetic acid (5 mL) and additional salt 22 (213 mg,
1.06 mmol) added followed by pyridine (0.5 mL). Reflux with stir-
ring for 45 min was followed by cooling with workup as described
above, and the resultant was purified by column chromatography
(ethyl acetate elution) to give a yellow/brown solid. Recrystallis-
ation (THF/hexane; 1:1, Ϫ16 °C) gave the title compound 28. Yield
575 mg, 90 % (based upon ketone used). Lustrous yellow crystals,
Charge-Transfer Complexation of 25 with DDQ: A solution of
DDQ (18.4 mg, 0.08 mmol) in dry acetonitrile (6 mL) was added
to a stirred solution of solvated 25 (20 mg, 0.04 mmol) in MeCN
(6 mL). The initially red coloured solution developed a dark green
colouration: UV-Vis (acetonitrile) (log ε) λmax ϭ 252 (4.56), 282
(4.07), 294 (4.04), 312 (4.03), 347 (4.07), 436 (3.88), 540Ϫ620 nm
(3.34). All attempts to isolate a crystalline product were unsuccess-
ful and the mixture become brown, even upon standing in the
freezer for 16 h.
1
m.p. 134Ϫ136 °C. H NMR (300 MHz, CDCl3): δ ϭ 6.80 (d, J ϭ
6.7 Hz, 1 H, 4-H or 5-H), 7.00 (d, J ϭ 6.7 Hz, 1 H, 5-H or 4-H),
7.11Ϫ7.17 (m, 2 H), 7.22Ϫ7.39 (m, 8 H) ppm. 13C NMR (75 MHz,
CDCl3): δ ϭ 118.9 (C4 or C5), 121.3, 125.4 (C5 or C4), 127.4 (CH),
127.9 (CH), 129.0 (CH), 129.3 (CH), 129.8 (CH), 130.3 (CH),
139.3, 140.0, 167.8, 185.8 (C8) ppm. HRMS (positive APCI) calcd.
for C17H13OS2 [M ϩ H]ϩ 297.0402; found 297.0395 (Ϫ2.36 mmu).
IR (KBr): ν˜ ϭ 3095, 3068, 1597, 1584, 1564, 1545, 1443, 1413,
1386, 1330, 1305, 1263, 1072, 989, 741, 698 cmϪ1. UV/Vis (aceto-
nitrile) (log ε) λmax ϭ 231 (4.13), 250 (3.88), 400 nm (4.39).
C17H12OS2 (296.2): calcd C 68.9, H 4.1; found C 68.7, H, 4.0.
10-(1,3-Dithiol-2-ylidene)anthracene-9(10H)one (26): Glacial acetic
acid (10 mL, 174.7 mmol) followed by pyridine (2 mL, 24.7 mmol)
was added to a mixture of salt 22 (1 g, 4.24 mmol) and anthrone
(0.82 mmol) under argon. The mixture was then stirred under re-
flux for 30 min, cooled, and the orange precipitate filtered off. The
solid was washed (water, 5 ϫ 40 mL), dried in vacuo, and recrystal-
lised (dichloromethane) to give the title compound 26. Yield
940 mg, 79% (ref.[21] 85 %). Bright orange needles, m.p. 220Ϫ221
1
°C (ref.[21] 219Ϫ221 °C). The H NMR spectroscopic data were in
agreement with those reported.[21] 13C NMR (75 MHz, CDCl3):
δ ϭ 116.1, 117.1 (CH), 124.9 (CH), 125.9 (CH), 126.1 (CH), 129.7,
130.9 (CH), 138.5, 145.0, 182.7 ppm.
1-[1,2-Diphenyl-2-(1,3-dithiol-2-ylidene)ethylidene]-1H-cyclo-
propa[b]naphthalene (29): Employing ketone 28 (156 mg,
0.52 mmol) and disilane 10 (150 mg, 0.52 mmol) and following the
general procedure given above, a dark red/orange oil was obtained.
Column chromatography (basic alumina, dichloromethane/light
petroleum elution; 4:1) afforded 1-[1,2-diphenyl-2-(1,3-dithiol-2-yli-
dene)ethylidene]-1H-cyclopropa[b]naphthalene (29). Yield 28.5 mg,
13 %. A red oil was isolated. 1H NMR (300 MHz, CDCl3): δ ϭ
6.26 (d, J ϭ 6.7 Hz, 1 H, 18-H or 19-H), 6.31 (d, J ϭ 6.7 Hz, 1 H,
19-H or 18-H), 7.16Ϫ7.45 (m, 9 H), 7.57Ϫ7.60 (m, 2 H, 10-H/14-
H or 22-H/26-H), 7.68 (d, J ϭ 1.6 Hz, 1 H, 2-H or 7-H), 7.82Ϫ7.93
(m, 4 H, 3-H/6-H and 10-H/14-H or 22-H/26-H) ppm. 13C NMR
(75 MHz, CDCl3): δ ϭ 107.7 (C2 or C7), 109.0 (C7 or C2), 112.6
(C1), 116.9 (C18 or C19), 119.5 (C19 or C18), 120.6, 121.8, 126.5
(CH), 126.6(8) (CH), 126.7(1) (CH), 127.1 (CH), 127.4, 127.7,
128.1 (CH), 128.5 (CH), 128.7 (CH), 128.8 (CH), 137.5, 138.7,
138.9, 141.2 ppm. HRMS (positive APCI) calcd. for C28H19S2 [M
ϩ H]ϩ 419.0923; found 419.0925 (ϩ0.48 mmu). IR (KBr): ν˜max
3048, 1765, 1630, 1592, 1542, 1486, 1439, 1413, 1344, 1144, 905,
845, 760, 744, 727, 692 cmϪ1. UV-Vis (hexane) (log ε) λmax ϭ 230
(4.69), 290 (4.33), 380 (4.24), 428 (3.99), 474 (4.18), 502 nm (4.21);
(acetonitrile) (log ε) λmax ϭ 232 (4.65), 288 (4.31), 378 (4.22), 422
(3.99), 476 nm (4.02).
9-(1H-Cyclopropa[b]naphthalene-l-ylidene)-10-(1,3-dithiol-2-
ylidene)-9,10-dihydroanthracene (27): Potassium tert-butoxide
(40 mg, 0.34 mmol) in dry THF (3 mL) was added dropwise over
5 min. to a stirred suspension of dithiole 26 (96 mg, 0.34 mmol)
and 10 (100 mg, 0.34 mmol) in the same solvent (15 mL) at
Ϫ78 °C under argon The dark red mixture was then allowed to
warm to room temperature overnight and then poured into water/
dichloromethane (200 mL; 1:1). The phases were separated, the
aqueous extracted (dichloromethane, 100 mL), and the combined
organic layers were washed (water, 100 mL), dried (MgSO4) and
concentrated under reduced pressure to produce a dark red oil.
Column chromatography (basic alumina, dichloromethane elution)
and trituration (dichloromethane) gave 9-(1H-cyclopropa[b]naph-
thalene-l-ylidene)-10-(1,3-dithiol-2-ylidene)-9,10-dihydro-
anthracene (27). Yield 8.9 mg, 6 %. Red/black needles, m.p.
253Ϫ254 °C (the sample darkened at 111Ϫ112 °C). 1H NMR
(300 MHz, CDCl3): δ ϭ 6.28 (s, 2 H, 20-H/21-H), 7.40Ϫ7.44 (m, 4
H, 10-H/11-H/15-H/16-H), 7.47Ϫ7.50 (BBЈ, 2 H, 4-H/5-H), 7.65 (s,
2 H, 2-H/7-H), 7.76Ϫ7.78 (m, 2 H, 12-H/14-H), 7.89Ϫ7.92 (AAЈ,
2 H, 3-H/6-H) ppm. 13C NMR (75 MHz, CDCl3): δ ϭ 107.9 (C2/
C7), 109.7 (C1), 113.6 (C8), 117.1 (C20/C21), 122.3 (C13), 123.5
(C9/C17), 126.0 (C12/C14), 126.4 (C10/C16 or C11/C15), 126.7(0)
(C11/C15 or C10/C16), 126.7(2) (Cla/C7a), 126.9 (C4/C5), 128.7
(C3/C6), 132.9 (C8a/C17a or C12a/C13a), 135.0 (C12/C13a or C8a/
C17a), 136.8 (C18), 139.1 (C2a/C6a) ppm. HRMS (positive APCI)
calcd. for C28H17S2 [M ϩ H]ϩ 417.0766; found 417.0760 (Ϫ1.44
mmu). IR (KBr): ν˜ ϭ 3057, 1631, 1497, 1442, 1416, 1142, 1115,
752, 742 cmϪ1. UV-Vis (acetonitrile) (log ε) λmax ϭ 236 (4.59), 268
(3.95), 295 sh (3.89), 382 (3.98), 420 (4.07), 508 nm (4.18). Further
attempts to prepare 27 afforded yields of 3Ϫ6 %.
Attempted Preparation of 3,6-Bis(1,3-dithiol-2-ylidene)-3,6-dihydro-
1H-cyclopropa[b]naphthalene (33): Attempts to effect reaction be-
tween 1 or 2 mol. equiv. of cyclopropanaphthoquinone[23] 30 and
dithiole 24 (250 mg, 1.18 mmol) afforded a dark green solution
which transformed upon work up to produce a viscous red oil con-
taining a complex mixture of components. The 1H NMR spectrum
and TLC showed no signals which corresponded to either 30, 24
(or, 23), or dithioles 32 or 33. Attempts to purify the mixture and
identify its components were unsuccessful.
8-(1,3-Dithiol-2-ylidene)-3,8-dihydro-1H-cyclopropa[b]anthracene-
3(8H)-one (34): n-Butyllithium (1.65 , 0.55 mL, 0.90 mmol) was
(2-Benzoyl)phenylmethylidene-1,3-dithiole (28): Glacial acetic acid
(5 mL, 87.4 mmol) and pyridine (1 mL, 12.4 mmol) were added added to a stirred solution of phosphonyl 24 (193 mg, 0.90 mmol)
Eur. J. Org. Chem. 2004, 138Ϫ146
www.eurjoc.org  2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim 145

B. Halton, C. S. Jones
FULL PAPER
[1]
in dry THF (3 mL) Ϫ78 °C under argon. After stirring the suspen-
sion for 30 min anthracenedione[24] 31 was added (100 mg,
0.45 mmol) dropwise in THF (3 mL) over 5 min. The coloured mix-
ture was warmed to room temperature overnight and poured into
water/dichloromethane (200 mL; 1:1). The phases were separated,
the aqueous extracted (dichloromethane, 100 mL), and the com-
bined organic layers were washed (water, 100 mL), dried (MgSO4)
and concentrated under reduced pressure to produce a red/orange
oil. Column chromatography (basic alumina, dichloromethane/
light petroleum elution; 4:1) gave a red solid as a near analytical
sample of 8(1,3-dithiol-2-ylidene)-3,8-dihydro-1H-cyclopropa[b]-
anthracene-3(8H)-one (34). Yield 40 mg, 23 %. Rust coloured pow-
der, m.p. Ͼ 350 °C. 1H NMR (300 MHz, CDCl3): δ ϭ 3.39 (s, 2
H, 1-H), 6.42 (broad s, 2 H, 4Ј-H/5Ј-H), 7.38Ϫ7.43 (m, 1 H, 6-H),
7.59Ϫ7.65 (m, 1 H, 5-H), 7.81 (d, J ϭ 1.8 Hz, 1 H, 9-H), 7.80Ϫ7.92
(m, 1 H, 7-H), 8.10 (d, J ϭ 1.8 Hz, 1 H, 2-H), 8.24Ϫ8.27 (m, 1 H,
4-H) ppm. 13C NMR (75 MHz, CDCl3): δ ϭ 19.8 (C1), 113.0 (C9),
113.8 (C2), 117.8, 117.9 (C4Ј or C5Ј), 118.0 (C5Ј or C4Ј), 125.3,
125.8 (C7), 126.4 (C6), 126.9 (C4), 130.6, 130.9, 131.5 (C5), 133.0,
139.9, 142.7, 145.7, 183.6 (C3) ppm. HRMS (positive APCI) calcd.
for C18H11S2O [M ϩ H]ϩ 307.0246; found 307.0253 (ϩ2.3 mmu).
IR (KBr): ν˜ ϭ 3093, 3059, 2926, 2852, 1636, 1594, 1573, 1479,
1443, 1285, 1231, 1123, 1099, 759, 688 cmϪ1. UV-Vis (hexane) (log
ε) λmax ϭ 251 (4.00), 358 (3.34), 431 (3.56), 451 nm (3.64); (aceto-
nitrile) (log ε) λmax ϭ 252 (4.57), 365 (3.89), 467 nm, (4.14). Recrys-
tallisation (dichloromethane/hexane; 1:1, Ϫ16 °C) resulted in sig-
nificant decomposition and Ͻ 1 mg of truncated rust coloured
cones were obtained.
B. Halton, Chem. Rev. 2003, 103, 1327Ϫ1370; B. Halton,
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´
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T. Finn, M. R. Bryce, A. S. Batsanov, J. A. K. Howard,
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[14b]
T. K. Hansen, T.
Jørgensen, F. Jensen, P. H. Thygesen, K. Christiansen, M. B.
Hursthouse, M. E. Harman, M. A. Malik, B. Girmay, A. E.
3,8-Bis(1,3-dithiol-2-ylidene)-3,8-dihydro-1H-cyclopropa[b]-
anthracene (35): n-Butyllithium (1.65 , 0.41 mL, 0.68 mmol) was
added to a stirred solution of phosphonyl 24 (145 mg, 0.68 mmol)
in dry THF (5 mL) at Ϫ78 °C under argon. The suspension was
stirred for 30 min and dione[24] 31 (150 mg, 0.68 mmol) was added
dropwise in THF (4 mL) over 5 min. The mixture was then allowed
to warm to room temperature overnight, poured into water/di-
chloromethane (200 mL; 1:1) and the phases separated. The aque-
ous phase was extracted (dichloromethane, 100 mL) and the com-
bined organic layers were washed (water, 100 mL), dried (MgSO4),
and concentrated under reduced pressure to produce a red/orange
oil. Column chromatography (basic alumina, dichloromethane/
light petroleum elution; 4:1) gave a yellow solid that contained pre-
dominately 3,8-bis(1,3-dithiol-2-ylidene)-3,8-dihydro-1H-cyclopro-
pa[b]anthracene (35). Yield 49 mg, 23 %. The compound decom-
posed upon further attempted purification (chromatography or
recrystallisation). 1H NMR (300 MHz, CDCl3) data abstracted
from the crude product for 35: δ ϭ 3.14 (d, J ϭ 4.2 Hz, 1 H, H-
1), 3.60 (d, J ϭ 4.2 Hz. 1 H, H-1), 6.27 (broad s, 4 H, 4Ј-H/5Ј-H/
9Ј-H/10Ј-H), 7.29Ϫ7.32 (BBЈ, 2 H, 5-H/6-H), 7.65 (s, 2 H, 2-H/9-
H), 7.68Ϫ7.73 (AAЈ, 2 H, 4-H/7-H) ppm. 13C NMR (75 MHz,
CDCl3) data abstracted from the crude product for 35: δ ϭ 21.0
(C1), 113.1 (C2/C9), 117.0(3) (C4Ј/C9Ј or C5Ј/C10Ј), 117.0(5) (C5Ј/
C10Ј or C4Ј/C9Ј), 124.8 (C4/C7), 125.9 (C5/C6) ppm. HRMS (posi-
tive APCI) calcd. for C21H13S4 [M ϩ H]ϩ 392.9895; found 392.9890
(Ϫ1.3 mmu).
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Acknowledgments
[28]
Support for this work from the Victoria University Science Faculty
Grants Committee (B. H., C. S. J.), and the Curtis-Gordon and
VUW Alumni Scholarship Funds (C. S. J.) is gratefully acknowl-
edged.
[29]
Received October 10, 2003
146
 2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
Eur. J. Org. Chem. 2004, 138Ϫ146