Studies in the Cycloproparene Series: Unexpected Products from Peterson Olefinations

Article abstract of DOI:10.1002/ejoc.200300382

Reaction of tetraphenylcyclopentadienone with anion 8 derived by monodesilylation of 1,1-bis(trimethylsilyl)cyclopropa[b]naphthalene (10) gives the 1-(5′-cyclopentadienyl)-substituted cycloproparene 17 from simple anion addition to the carbonyl group rather than fulvalene 16 from loss of Me₃SiO^-. Reactions of anion 8 with p-(trifluoromethyl)benzaldehyde and thiophene-2-carbaldehyde give the expected exocyclic olefins 12a and 12b, respectively. In contrast, the 3,6-dimethoxy analogue 24, obtained from cycloproparene 20, gives the C1 unsubstituted cycloproparene 19 and the Tishchenko products, p-(trifluoromethyl)benzyl p-(trifluoromethyl)benzoate (21) and 2-thienylmethyl thiophene-2-carboxylate (22), respectively. Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003.

Full text of DOI:10.1002/ejoc.200300382

FULL PAPER
Studies in the Cycloproparene Series: Unexpected Products from Peterson
Olefinations
[a]
[b]
[a]
Brian Halton,* Roland Boese, and Gareth M. Dixon
Keywords: Arenes / Small ring systems / Olefination / Nucleophilic addition / Strained molecules / Hydrosilation
Reaction of tetraphenylcyclopentadienone with anion 8 de- 3,6-dimethoxy analogue 24, obtained from cycloproparene
rived by monodesilylation of 1,1-bis(trimethylsilyl)cyclo-
20, gives the C1 unsubstituted cycloproparene 19 and the
propa[b]naphthalene (10) gives the 1-(5Ј-cyclopentadienyl)- Tishchenko products, p-(trifluoromethyl)benzyl p-(trifluoro-
substituted cycloproparene 17 from simple anion addition to
methyl)benzoate (21) and 2-thienylmethyl thiophene-2-carb-
oxylate (22), respectively.
the carbonyl group rather than fulvalene 16 from loss of
−
Me
3
SiO . Reactions of anion 8 with p-(trifluoromethyl)benz-
aldehyde and thiophene-2-carbaldehyde give the expected
( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
exocyclic olefins 12a and 12b, respectively. In contrast, the
Germany, 2003)
1
Introduction
has come from the transformation of 1 into 11 (R ϭ Ph;
2
R ϭ H) employing benzaldehyde. In this instance, and
The class of strained aromatic hydrocarbons known as
the cycloproparenes, and illustrated by parent 1H-cyclopro-
pabenzene (1) and 1H-cyclopropa[b]naphthalene (2), has
after short reaction periods, an unstable oil was obtained in
yields of up to 40% that was proposed as the β-hydroxysil-
ane 13 (Scheme 1) from workup prior to the loss of trimeth-
[1,2]
provided much fascinating chemistry
since Anet and
[12]
ylsilyl oxide.
We provide here the first examples of at-
[
3]
Anet reported the first authenticated derivative in 1964.
tempted Peterson olefinations in the cyclopropanaph-
thalene series where the desired olefination is thwarted and
unexpected products are obtained.
[
4,5]
The fact
that the pK of 1 is ca. 36 means that the C1
a
cyclopropabenzenyl anion 3 and its naphthalenyl analogue
4
can be generated with relative ease and used in synthesis.
[6,7]
This has proved to be the case
as 3 and 4 have been used
routinely in Peterson olefinations[
8Ϫ11]
to give exocyclic al- Results and Discussion
kenes 11 and 12 (Scheme 1) of which there now exist well
in excess of 100 examples.[
1]
The provision of polar fulvalenes from 1 and 2 has been
[
13]
appropriately demonstrated
for derivatives of ring sys-
In the cyclopropabenzene series the reaction sequence
tems rather than for the parent molecules themselves. Thus,
can be performed as a one-pot operation for the transform-
ation of 1 into 11.[12] This contrasts with cyclopropa[b]-
the fluorenylidene derivatives 14 and 15 are available in
[
14]
good yields
although no simpler cyclopentadienylidene
naphthalene where the transformation of 2 into disilane 10
because monosilane 6 is deprotonated under the reaction
conditions by unconsumed 4, regenerates 2 and gives 10
analogues are known Ϫ the facile thermal dimerisation of
cyclopentadienone has precluded its use. In our study of
‘‘push-pull’ electronic effects in the cycloproparenes,[ we
attempted to prepare the tetracyclone derivative 16 for use
as a model compound by employing what are now conven-
tional procedures and workup. While an orange solid was
isolated it proved not to be the alkylidene derivative 16, but
alcohol 17 resulting from nucleophilic addition of anion 8
to the tetracyclone ϾCϭO bond and subsequent pro-
15]
via anion 8) in equimolar quantities (Scheme 1).[
6,11,12]
(
Use
of excess reagents leads to 10 in good yield (66%) and this
stable, crystalline synthon can be stored in the refrigerator
almost indefinitely. Desilylation of 10 with potassium tert-
butoxide regenerates anion 8 and this is able to react with
added aldehyde or ketone to give the desired exocyclic al-
kene 12. In all but one of such reported Peterson olefina-
1
[
1]
tonation. The presence of H NMR singlets at δ ϭ
tions the sequences from 1 to 11, and from 10 to 12, pro-
0
.22 ppm (Me Si) and 5.20 ppm (OH) in a ratio of 9:1 to-
ceed directly to the alkene; the only side product recorded
3
gether with an envelope of 26 aromatic protons in the range
[
[
a]
b]
School of Chemical & Physical Sciences, Victoria University δ ϭ 7.22Ϫ7.95 ppm is fully consistent with this (see Exp.
of Wellington,
Sect.). That the cyclopropa[b]naphthalenyl moiety had been
P. O. Box 600, Wellington, New Zealand
Institute for Inorganic Chemistry, University of Essen,
[
1,16]
retained was clearly evident from the diagnostic
shield-
Universitaetsstr. 3Ϫ5, 45117 Essen, Germany
ing of the C2/C7 arene carbon atoms adjacent to the three-
Eur. J. Org. Chem. 2003, 4507Ϫ4512
DOI: 10.1002/ejoc.200300382
 2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
4507

B. Halton, R. Boese, G. M. Dixon
FULL PAPER
Scheme 1
membered ring (δ ϭ 113.6 ppm). Confirmation of the com-
position as C H OSi has come from high-resolution mass
4
3
36
measurement and the compound is confidently assigned as
the 1,1-disubstituted cycloproparene 17. The formation of
alcohol is quite understandable when one considers the un-
favourable geometrical constraints that are present in the
syn-periplanar transition structure 18 needed for the ejec-
tion the trimethylsilyloxy anion in the additionelimination
pathway. The formation of alcohols under the Peterson pro-
tocol is well documented and can be the normal outcome if
the alkene is not stabilized.[ Moreover, subsequent alkene
formation can often be brought about by dehydroxysilation
under acid conditions. However, treatment of 17 with acid
does not lead to the sought after exocyclic alkene. The
cycloproparenes and their alkylidene derivatives are known
to be sensitive to acids[ and the complex mixture of prod-
ucts formed is thought to be due to this. A comparable out-
come was obtained from attempted Peterson olefination of
17]
18]
the 3,6-dimethoxycyclopropanaphthalene 19 by way of dis- (Scheme 2).[11] In contrast, comparable reactions employing
ilane 20. However, in this instance the reaction product, as- the 3,6-dimethoxy-substituted analogue 20 result in differ-
sumed to be the 3,6-dimethoxy-substituted alcohol corre- ent outcomes that are less easily explained.
sponding to 17 was not isolated as it proved to be light and
air sensitive; it decomposed during attempted purification.
Following chromatography, the reaction of 20 with tert-
butoxide in the presence of p-(trifluoromethyl)benzaldehyde
The behaviour of the unsubstituted disilane 10 towards leads to yellow platelets that bear all the obvious external
p-(trifluoromethyl)benzaldehyde in the presence of base is characteristics of a coloured, crystalline alkylidenecyclopro-
in agreement with expectation (Scheme 2)[ in that ex- parene. However, the NMR spectra immediately exclude
1]
1
ocyclic alkene 12a (R ϭ p-CF C H ) is obtained as bright such a structure since the H spectrum shows an absence
3
6
4
yellow needles in 62% yield, although this quantity is ob- of methoxy protons and the 13C analogue has no shielded
[
1]
tained only after variations in the reaction conditions (see cycloproparene C2/C7 aromatic carbon atoms. Not only
Exp. Sect.). Spectroscopic data that are fully in agreement is a derivative of 12 discounted, but also is any compound
with the assigned structure were obtained, but these do not in which the elements of the cycloproparenyl moiety were to
justify discussion here. Similarly, anion 8 is known to react have become involved. This was confirmed from subsequent
with thiophene-2-carbaldehyde to give conjugated alkene continued chromatography, which provided the desilylated
1
2
1
2b (R ϭ H; R ϭ 2-thienyl), but only in low (34%) yield dimethoxycycloproparene 19 in almost quantitative yield.
4508
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www.eurjoc.org Eur. J. Org. Chem. 2003, 4507Ϫ4512

Studies in the Cycloproparene Series
FULL PAPER
The reaction of an aldehyde to give an ester that carries
the acid component from oxidation and the alcohol moiety
from reduction is the known as the Tishchenko reaction,[
20]
and it is catalysed by early lanthanoid reagents; Cp LaH-
2
(SiMe3)2 is particularly effective. It has analogy to the
Cannizzaro reaction inasmuch as an aldehyde with no α
hydrogen atom has half an equivalent reduced and the other
half oxidized. However, unlike the Cannizzaro reaction, an
ester is obtained instead of an acid and an alcohol. Of par-
ticular relevance here is the fact that attempted hydro-
silation of benzaldehyde with dimethylphenylsilane and
catalyst provided the Tishchenko ‘‘dimer’’ benzyl benzoate
[
19]
in 90% yield. Moreover, when the silane was omitted, the
same yield of dimer (88%) was obtained (Scheme 3). Under
such catalysis, Tanaka and co-workers report a quantitative
conversion of thiophene-2-carbaldehyde into ester 22.[
19]
Scheme 2
The nature of the unexpected product became more obvi-
ous from observation of a conjugated carbonyl stretching
Ϫ1
vibration at 1685 cm in the IR spectrum and a molecular
Scheme 3
ion as the base peak of the E.I. mass spectrum at m/z ϭ
356. Furthermore, the presence of two independent para
disubstituted benzene rings each carrying a CF group
3
1
9
13
Of all the aldehydes and ketones that have reacted with
(with appropriate long range F, C couplings from dis-
[
15,21]
disilane 20 in the presence of base
only p-(trifluorome-
tinct p-CF3 moieties at δ ϭ 130.3 ppm and 134.7 ppm,
respectively Ϫ see Exp. Sect.) and a benzylic function (δH:
thyl)benzaldehyde and thiophene-2-carbaldehyde have af-
forded Tishchenko dimers and regenerated the original
cycloproparene hydrocarbon 19. The regeneration of parent
5
.48 ppm; δ : 66.2 ppm) are evident from the 2-D NMR
C
spectra recorded. The product is confirmed as p-trifluoro-
methybenzyl p-(trifluoromethyl)benzoate (21; 41%;
2
upon desilylation of disilane 10 has been the subject of a
[
6]
detailed investigation in these laboratories. The reaction
is base catalysed and requires one equivalent each of base
and water to effect monodesilylation and subsequent pro-
tonation of the α-silyl anion. Proton capture releases hy-
droxide ion for the removal of the second trimethylsilyl
group and protonation upon workup completes the se-
quence. The same process is presumed to operate for the
analogous 20 Ǟ 19 transformation. The involvement of
water in the Tishchenko reactions in which 21 and 22 are
formed has been discounted, however, from the results of
a dual reaction in which both p-(trifluoromethyl)- and p-
methoxybenzaldehyde can react with α-silyl anion 24 from
Scheme 2) from single-crystal X-ray structure determi-
nation. The details of the analysis have been deposited (see
Exp. Sect.) and Figure 1 shows an ORTEP plot of the mol-
ecule at 50% probability. The recorded bond lengths and
angles fall within expectation for such a routine structure
but the six fluorine atoms are disordered over two sites with
an occupancy at 0.5 each.
20. Thus, reaction of 2 mol. equiv. each of disilane 20 and
potassium tert-butoxide with a mixture of 1 mol. equiv. of
each aldehyde leads to the isolation of hydrocarbon 19
Figure 1. ORTEP plot of p-(trifluoromethyl)benzyl p-(trifluorome- (47%), Tishchenko dimer 21 (40%), and the normal ex-
thyl)benzoate (21) at 50% probability
ocyclic alkene 23 from anisaldehyde (77%; cf. 83% from a
dedicated procedure with p-anisaldehyde alone Ϫ Exp.
In a similar vein, the reaction between 20 and base in the Sect.; Scheme 4).
presence of thiophene-2-carbaldehyde does not give antici-
A Cannizzaro reaction of p-(trifluoromethyl)benzal-
pated exocyclic analogue of 12b. It also yields the desilyl- dehyde to give a 1:1 mixture of acid (from oxidation) and
ated diether 19 (91%) this time accompanied by 2-thienyl- alcohol (from reduction) in 90% overall yield is effected by
methyl thiophene-2-carboxylate (22) (45%), the latter dis- aqueous NaOH over 30 minutes. In contrast, potassium
playing spectroscopic data that match those recently pub- tert-butoxide is ineffective and returns unchanged aldehyde
[
19]
lished.
almost quantitatively under conditions that match those
Eur. J. Org. Chem. 2003, 4507Ϫ4512
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 2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
4509

B. Halton, R. Boese, G. M. Dixon
FULL PAPER
Scheme 5
7
0 eV data from a HewlettϪPackard 5995C instrument. 1H and
C NMR spectra were recorded with a Varian Unity INOVA
00 MHz instrument for [D]chloroform solutions using the residual
1
3
Scheme 4
3
solvent peak as internal standard. The usual notations define NMR
multiplicities and coupling constants are in Hertz. The assignment
from which Tishchenko dimer is obtained. Furthermore, es-
ter 21 is not hydrolysed by tert-butoxide in dry THF under
the conditions of its formation. Given these data, we con-
clude that the two Tishchenko reactions recorded herein re-
13
1
of C and H NMR resonances was made with the aid of DEPT
1
1
13
1
and H- H COSY and C- H HSQC experiments, and heteronu-
clear multiple bond connectivity (HMBC) experiments. IR spectra
sult from attack of cycloproparenyl anion 24 on the al- of solid samples were recorded for KBr disks using a Biorad FTS
dehydic carbon of the added aldehyde to give anion 25, as 7 spectrophotometer while UV/Vis spectra were measured with a
shown in Scheme 5 for the trifluoromethyl compound. In- HewlettϪPackard 8452A diode array spectrophotometer. Melting
points were determined with a Reichert hot-stage melting point
apparatus and are uncorrected.
termolecular hydride ion transfer to aldehyde then gener-
ates acylcycloproparene 26 and alkoxide. In turn, this can
then react at the acyl carbonyl centre in an addition-elimin-
Thin-layer chromatographic (TLC) analyses were performed using
ation sequence to liberate the Tishchenko dimer 21 and re- Merck Kieselgel (Alufolien) 60 F254 to a thickness of 0.2 mm. Com-
generate anion 24 which affords hydrocarbon 19 from base- ponents were detected under an ultraviolet lamp at 254 or 350 nm,
induced desilylation.
or in an iodine chamber. Radial chromatography plates were coated
with Merck Kieselgel 60 GF254 to a thickness of 2.0 or 4.0 mm.
While the sequence of Scheme 5 adequately accounts for
the formation of the observed products, it offers little to
account for the anomalous behaviour of the two aldehydes
General Method for the Synthesis of Alkylidene-1H-cyclopropa[b]-
[11]
naphthalenes: To a stirred solution of disilane 10 or 20 (1 equiv.)
in question. The fact that exocyclic alkenes are obtained and the carbonyl compound (1 equiv.) in anhydrous THF (ca.
using the same aldehydes with non-ether 10 argues strongly 10 mL), cooled to Ϫ70 °C and under nitrogen, was added dropwise
for the electron donating capacity of the methoxy groups via syringe needle to a solution of freshly sublimed potassium tert-
butoxide (1 equiv.) in the same anhydrous solvent (ca. 10 mL). The
mixture was stirred at Ϫ70 °C for 1 h then warmed to ambient
of 20 to influence subtly the course of reaction. This ap-
pears most likely, as differences in steric demand at the reac-
tion sites of 10 and 20 should not be large. We continue to
explore the chemistry of these novel compounds.
temperature overnight. The mixture was quenched (satd. NaHCO
0 mL) and the organic phase extracted with dichloromethane (3
ϫ 20 mL). The combined organic extracts were washed (water; 3 ϫ
0 mL), dried (MgSO ), filtered, and concentrated under reduced
3
;
3
2
4
pressure to give a crude product that was purified by radial chro-
matography.
Experimental Section
General: The Analytical Facility of Otago University, Dunedin,
performed all microanalyses. Mr. O. Zubkov recorded mass meas-
urements with high resolution coming from a PE Biosystems Mari-
1-(5-Hydroxytetraphenylcyclopenta-1,3-dienyl)-1-trimethylsilyl-1H-
cyclopropa[b]naphthalene (17): Treated as described above, disilane
20 (100 mg. 0.35 mmol),[ tetracyclone (135 mg, 0.35 mmol) and
21]
ner 5158 TOF spectrometer operating in electrospray mode, and potassium tert-butoxide (40 mg, 0.35 mmol) gave an orange-brown
4510  2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim www.eurjoc.org Eur. J. Org. Chem. 2003, 4507Ϫ4512

Studies in the Cycloproparene Series
FULL PAPER
solid, which upon radial chromatography (light petroleum/di-
0.29 mmol)[21] and p-(trifluoromethyl)benzaldehyde (51 mg,
0.29 mmol) gave a bright yellow solid that was radially chromato-
graphed (3:1 light petroleum/dichloromethane elution). The most
[
14]
chloromethane, 4:1) gave 1H-cyclopropa[b]naphthalene
(2) as
the most mobile fraction. Yield 8 mg, (16%). The second fraction
comprised of 17. Yield 94 mg, (45%). Orange powder, m.p. mobile fraction provided title benzoate 21. Yield: 50 mg (41%). Yel-
1
1
1
06.0Ϫ107.5 °C. H NMR (300 MHz, CDCl
3
3
): δ ϭ 0.22 (s, 9 H,
low platelets (light petroleum), m.p. 61.0Ϫ62.0 °C. H NMR
4
3
SiMe ), 5.20 (broad s, 1 H, OH), 7.22 (tt,
3
J
AB ϭ 7.5,
J
AC
ϭ
(300 MHz, CDCl
3
): δ ϭ 5.48 (s, 2 H, 8-H), 7.57 (d, JAB ϭ 8.1 Hz,
2 H, 2Ј/6Ј-H), 7.65 (d, JAB ϭ 8.1 Hz, 2 H, 3Ј/5Ј-H), 7.72 (d, JAB ϭ
3
3
3
3
1
.6 Hz, 2 H), 7.32 (t, JAB ϭ 7.8 Hz, 4 H), 7.33 (tt, JAB ϭ 7.5,
4
AC ϭ 1.6 Hz, 2 H), 7.42Ϫ7.55 (m, 8 H), 7.61Ϫ7.76 (m, 8 H, 2 ϫ 8.1 Hz, 2 H, 3/5-H), 8.19 (d, JAB ϭ 8.1 Hz, 2 H, 2/6-H) ppm. 13C
3
J
1
1
4/18-H, 4/5-H and 2/7-H), 7.91Ϫ7.95 (BBЈ of AAЈBBЈ, 2 H, 3/6-
NMR (75 MHz, CDCl
3
): δ ϭ 66.2 (C8), 123.5 (q, JC,F ϭ 273 Hz,
), 36.3 (C1), C10), 123.9 (q, JC,F ϭ 273 Hz, C9), 125.5 (q, JC,F ϭ 3 Hz, C3/5),
13
1
3
H) ppm. C NMR (75 MHz, CDCl
3
): δ ϭ 0.2 (SiMe
3.8 (C8), 113.6 (C2/7), 125.3(C1a/7a), 126.8 (C4/5) 127.1(C3/6),
28.1 (C22), 128.6 (C10/11), 128.8 (C9/12), 129.7 (C16), 130.5 (C21/
3
3
8
1
125.7 (q, JC,F ϭ 3 Hz, C3Ј/5Ј), 128.3 (C2Ј/6Ј), 130.1 (C2/6), 130.3
(q, JC,F ϭ 33 Hz, C4Ј), 132.9 (C1), 134.7 (q, JC,F ϭ 33 Hz, C4),
2
2
2
3), 130.6 (C20/24), 130.7 (C15/17), 131.5 (C14/18), 132.7 (C19), 139.5 (C1Ј), 165.0 (C7) ppm. IR (KBr): ν˜ max ϭ 2934, 2374, 1724,
1
33.1 (C13), 136.5 (C2a/6a) ppm. HRMS (positive APCI) calcd. 1513, 1445, 1413, 1324, 1276, 1166, 1125, 1109, 1065, 1016, 860,
ϩ
Ϫ1
for C43
H
36OSi [M ϩ H ] 597.2613; found 597.2608 (Ϫ0.84 mmu).
774 cm . UV/Vis (cyclohexane): λmax (log ε) ϭ 234 (4.21), 268
ϩ
ϩ
MS (70 eV): m/z (%) ϭ 597 (52) [M ϩ 1 ] 596 (100) [M ], 582
(3.68), 272 (3.65), 284 nm (3.62) nm; (acetonitrile): λmax ϭ 236
(4.12), 270 (3.71), 274 (3.65) nm. MS (70 eV): m/z (%) ϭ 357 (25)
(
(
23), 581 (45), 568 (19), 525 (33), 524 (80), 522 (11), 496 (23), 105
17). IR (KBr): ν˜ max ϭ 3440, 3051, 2968, 2923, 2169, 1685, 1561,
ϩ
ϩ
[M ϩ 1 ], 356 (100) [M ], 342 (15), 341 (71), 327 (13), 326 (56),
Ϫ1
1
438, 1384, 1293, 1231, 1132, 1095, 1028, 955 cm . UV/Vis (cyclo-
313 (6), 298 (18), 270 (11). C16
H
10
F
6
O
2
(316.06): calcd. C 55.2, H
hexane): λmax (log ε) ϭ 226 (4.05), 284 (3.84), 340 (3.88) nm; 2.9, F 32.7; found C 55.5, H 2.7, F 32.9.
(
acetonitrile): λmax ϭ 226 (4.02), 286 (3.79), 340 (3.86) nm.
Further radial chromatography (light petroleum elution) provided
Reaction of Silanol 17 with Dilute Hydrochloric Acid: During the
space of 1 min an aqueous solution of HCl (10% v/v, 0.5 mL) was
added dropwise to silanol 17 (30 mg, 0.05 mmol) in refluxing THF
3,6-dimethoxy-1H-cyclopropa[b]naphthalene (19) identical to that
previously prepared and with spectroscopic data in agreement with
[21]
those published. Yield: 55 mg (95%).
(20 mL). The mixture was refluxed for 30 min whereupon the col-
our changed from orange to black-brown. Following workup and
concentration, the components of the resultant brown solid proved
Reactions of p-(Trifluoromethyl)benzaldehyde with Bases
inseparable by radial chromatography. The 13C NMR spectrum of
the crude product showed no shielded C2/7 centres and ring open-
i) With Potassium tert-Butoxide: Under conditions analogous to
those employed above but in the absence of cycloproparene, p-(tri-
fluoromethyl)benzaldehyde (51 mg, 0.29 mmol) was recovered
quantitatively from attempted reaction with potassium tert-butox-
ide (34 mg, 0.29 mmol).
ing of the cycloproparene is presumed to have taken place.[
1]
1
-(p-Trifluoromethylphenyl)methylidene-1H-cyclopropa[b]-
naphthalene (12a): Although p-(trifluoromethyl)benzaldehyde is
stable to the reaction conditions (see below), the best yield of al-
kene 12a resulted from a variation in the general procedure. Thus
ii) With Aqueous Sodium Hydroxide: When stirred for 30 min at
ambient temperature, p-(trifluoromethyl)benzaldehyde (102 mg,
p-(trifluoromethyl)benzaldehyde (0.78 mL, 61 mg, 0.35 mmol) was 0.58 mmol) and aqueous sodium hydroxide (50% w/w, 1.0 mL) pro-
added to anion 8, preformed by reacting disilane 10 (100 mg,
vided a 1:1 mixture of p-(trifluoromethyl)benzoic acid and p-(tri-
.35 mmol) with potassium tert-butoxide (40 mg, 0.35 mmol) at fluoromethyl)benzyl alcohol in 90% overall yield.
[
21]
0
Ϫ70 °C. Workup according to the general procedure gave a yellow
solid, which upon radial chromatography (light petroleum elution)
yielded from the most mobile fraction the title alkene 12a. Yield:
Reactions of Ester 21 with Bases
i) With Potassium tert-Butoxide: Ester 21 (50 mg, 0.14 mmol) and
potassium tert-butoxide (19 mg, 0.14 mmol) were refluxed for 1 h
in THF. Workup gave recovered ester in quantitative yield.
6
1
8
7
4 mg (62%). Bright yellow needles (light petroleum), m.p.
62.5Ϫ164.0 °C. H NMR (300 MHz, CDCl ): δ ϭ 6.57 (s, 1 H,
3
-H), 7.49Ϫ7.55 (AAЈ, 2 H, 4/5-H), 7.63Ϫ7.66 (m, 2 H, 11/13-H),
1
.71 (d, Jpara ϭ 1.7 Hz, 1 H, 7-H), 7.78 (d, Jpara ϭ 1.7 Hz, 1 H, 2-
ii) With Aqueous Sodium Hydroxide: Ester 21 (50 mg, 0.14 mmol)
and aqueous sodium hydroxide (50% w/w, 1.0 mL) were refluxed
for 1 h in THF. A 1:1 mixture of p-(trifluoromethyl)benzoic acid
and p-(trifluoromethyl)benzyl alcohol was isolated in 90% overall
yield.
3
H), 7.88 (d, JAB ϭ 8.3 Hz, 2 H, 10/14-H), 7.92Ϫ7.98 (BBЈ, 2 H,
3
/6-H) ppm. 13C NMR (75 MHz, CDCl
3
): δ ϭ 104.9 (C8), 109.0
), 124.9
1
(C7), 109.3 (C2), 114.0 (C1), 124.2 (q, JC,F ϭ 272 Hz, CF
3
3
(
C7a), 125.6 (q, JC,F ϭ 4 Hz, C11/13), 127.0 (C1a), 127.1(0) (C10/
4), 127.1(5) (C5), 127.2 (C4), 129.0 (C6), 129.2 (C3), 129.0 (q,
J
1
2
C,F ϭ 32 Hz, C12), 138.5 (C6a), 138.6 (C9), 139.2 (C2a) ppm. IR In situ Reaction of Disilane 20 with Potassium tert-Butoxide in the
(
KBr): ν˜ max ϭ 3235, 2926, 2853, 2170, 1773, 1636, 1616, 1406,
1
Presence of p-(Trifluoromethyl)benzaldehyde and p-Methoxybenzal-
dehyde: Disilane 20 (200 mg, 0.58 mmol), potassium tert-butox-
ide (68 mg, 0.58 mmol), p-(trifluoromethyl)benzaldehyde (51 mg,
325, 1161, 1111, 1067, 1006, 860, 752, 610 cmϪ1. UV/Vis (cyclo-
[21]
hexane): λmax (log ε) ϭ 286 (3.32), 394 (3.40), 422 (3.51) nm;
(
(
2
acetonitrile): λmax ϭ 286 (3.30), 394 (3.41), 418 (3.46) nm. MS 0.29 mmol) and p-methoxybenzaldehyde (39 mg, 0.29 mmol) were
ϩ ϩ
70 eV): m/z (%) ϭ 297 (22) [M ϩ 1 ], 296 (100), [M ], 275 (10),
46 (8), 226 (31) [M Ϫ CF ], 123 (11). µ (21 °C) ϭ 3.02 D. and radial chromatography gave:
(296.08): calcd. C 77.0, H 3.7; found C 77.1; H 3.6.
3,6-Dimethoxy-1-(p-methoxyphenyl)methylidene-1H-cyclopropa-
b]naphthalene (12c): Yield: 71 mg (77%). Yellow needles (light
reacted in anhydrous THF (30 mL) as described above. Workup
3
19 11 3
C H F
[
1
-(2Ј-Thienyl)methylidene-1H-cyclopropa[b]naphthalene (12b) was
petroleum), m.p. 148.5Ϫ151.0 °C (see below),
synthesised in the same yield and with the same spectroscopic data
as described previously.[
11]
p-(Trifluoromethyl)benzyl p-(trifluoromethyl)benzoate (21): Yield:
48 mg (40%). Yellow platelets (light petroleum), m.p. 60.0Ϫ62.0
°C, and
p-(Trifluoromethyl)benzyl p-(Trifluoromethyl)benzoate (21): The
general procedure described above employing disilane 20 (100 mg,
Eur. J. Org. Chem. 2003, 4507Ϫ4512
www.eurjoc.org
 2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
4511

B. Halton, R. Boese, G. M. Dixon
FULL PAPER
3,6-Dimethoxy-1H-cyclopropa[b]naphthalene (19): Yield: 55 mg
X-ray Structure Determination of p-(Trifluoromethyl)benzyl p-(Tri-
(95%). Clear prisms, m.p. 129.0Ϫ131.0 °C. No evidence was ob- fluoromethyl)benzoate (21): CCDC-213488 contains the supplemen-
tained for 1-(p-trifluoromethylphenyl)methylidene-3,6-dimethoxy-
tary crystallographic data for this structure. These data can be ob-
tained free of charge at www.ccdc.cam.ac.uk/conts/retrieving.html
1H-cyclopropa[b]naphthalene.
[
or from the Cambridge Crystalographic Data Centre, 12 Union
Road, Cambridge CB2 1EZ, UK; Fax (internat.) ϩ44-1223/336-
33; E-mail: deposit@ccdc.cam.ac.uk].
3
[
,6-Dimethoxy-1-(p-methoxyphenyl)methylidene-1H-cyclopropa-
b]naphthalene (23): Disilane 12 (100 mg, 0.29 mmol)[ and p-
11]
0
methoxybenzaldehyde (40 mg, 0.29 mmol) gave a yellow solid,
which upon radial chromatography (light petroleum/dichlorometh-
ane, 4:1) provided from the most mobile fraction the title com-
pound 23. Yield: 76 mg (83%). Yellow needles (light petroleum),
m.p. 148.5Ϫ150.0 °C. H NMR (300 MHz, CDCl
Acknowledgments
Financial support in New Zealand from Victoria University and in
1
3
): δ ϭ 3.86 (s, 3
H, C12ϪOMe), 3.89 (s, 3 H, C3/6ϪOMe), 3.89 (s, 3 H, C6/ Germany from the Deutsche Forschungsgemeinschaft and Fonds
3
3
8
ϪOMe), 6.44 (s, 1 H, 8-H), 6.70 (s, 2 H, 4/5-H), 7.00 (d, JAB
ϭ
der Chemischen Industrie is gratefully acknowledged.
3
.3 Hz, 2 H, 11/13-H), 7.61 (d, JAB ϭ 8.3 Hz, 2 H, 10/14-H), 7.81
(
d, Jpara ϭ 1.7 Hz, 1 H, 7-H), 7.85 (d, Jpara ϭ 1.7 Hz, 1 H, 2-
[1]
B. Halton, Chem. Rev. 2003, 103, 1327Ϫ1370.
13
H) ppm. C NMR (75 MHz, CDCl
3
): δ ϭ 55.1 (C12ϪOMe), 55.9
[2]
B. Halton, Chem. Rev. 1989, 89, 1161Ϫ1185.
(C3/6ϪOMe), 102.0 (C7), 102.0(5) (C2), 104.2 (C5), 104.3 (C4),
[3]
R. Anet, F. A. L. Anet, J. Am. Chem. Soc. 1964, 86, 525Ϫ526.
C. Eaborn, R. Eidenschink, S. J. Harris, D. R. M. Walton, J.
Organomet. Chem. 1977, 124, C27ϪC29.
C. Eaborn, J. G. Stamper, J. Organomet. Chem. 1980, 192,
155Ϫ161.
B. Halton, C. S. Jones, J. Chem. Soc., Perkin Trans. 2 1998,
2505Ϫ2508; B. Halton, C. S. Jones, J. Chem. Soc., Perkin Trans.
[
[
[
4]
5]
6]
1
1
1
05.8 (C8), 111.1 (C1), 112.5 (C11/13), 125.8 (C7a), 127.7 (C1a),
27.8 (C10/14), 130.4 (C6a), 130.5 (C2a), 131.2 (C9), 150.4 (C6),
50.5 (C3), 157.2 (C12 ppm. HRMS (positive APCI) calcd. for
ϩ
21 18 3
C H O [M ϩ H ] 319.1334; found 319.1338 [ϩ1.2(5) mmu]. IR
(
KBr): ν˜ max ϭ 3054, 2965, 2929, 2856, 1931, 1774 (w), 1660, 1646,
Ϫ1
1
λ
598, 1254, 1165, 1034, 866, 822, 787 cm . UV/Vis (cyclohexane):
max (log ε) ϭ 312 (3.77), 320 (3.82), 416 (4.01), 440 (4.10) nm;
acetonitrile): λmax ϭ 314 (3.71), 320 (3.80), 414 (3.99), 436 nm
4.05). µ (21 °C) ϭ 0.92 D. C21 (319.13): calcd. C 79.2, H
.7. found C 79.1, H 5.5(5).
2
1999, 387.
[7]
[8]
[9]
C. A. Cutler, B. Halton, Aust. J. Chem. 1997, 50, 267Ϫ270.
B. Halton, G. M. Dixon, Org. Lett. 2002, 4, 4563Ϫ4565.
B. Halton, M. J. Cooney, R. Boese, A. H. Maulitz, J. Org.
Chem. 1998, 63, 1583Ϫ1590.
(
5
18 3
H O
[10]
B. Halton, P. J. Stang, Synlett 1997, 145Ϫ158.
B. Halton, M. J. Cooney, T. W. Davey, G. S. Forman, Q. Lu,
R. Boese, D. Bläser, A. H. Maulitz, J. Chem. Soc., Perkin Trans.
1995, 1, 2819Ϫ2827.
B. Halton, C. J. Randall, G. J. Gainsford, P. J. Stang, J. Am.
Chem. Soc. 1986, 108, 5949Ϫ5956.
Y. Apeloig, R. Boese, D. Bläser, B. Halton, A. H. Maulitz, J.
Am. Chem. Soc. 1998, 120, 10147Ϫ10153.
B. Halton, S. J. Buckland, Q. Lu, Q. Mei, P. J. Stang, J. Org.
Chem. 1988, 53, 2418Ϫ2422.
G. M. Dixon, PhD thesis, Victoria University of Wellington
Reaction of Disilane 20 with Potassium tert-Butoxide in the Presence
of 2-Thiophenecarbaldehyde: Disilane 20 (100 mg, 0.29 mmol)[
and 2-thiophenecarboxaldehyde (33 mg, 0.39 mL, 0.29 mmol) pro-
duced from application of the general procedure, a bright yellow
solid. Radial chromatography (light petroleum/dichloromethane,
[11]
21]
[
[
[
12]
13]
14]
3
:1) provided from the most mobile fraction 2-thienylmethyl thio-
[
19]
phene-2-carboxylate (22).
(
CDCl
1
Yield: 29 mg (45%). Yellow needles
1
light petroleum), m.p. 72.0Ϫ72.5 °C. H NMR (300 MHz,
3
): δ ϭ 5.49 (s, 2 H, 7-H), 7.02 (dd, J2,3 ϭ 3.4, J1,2 ϭ 5.1 Hz,
[15]
[16]
[17]
H, 4-H), 7.10 (dd, J2,3 ϭ 3.9, J1,2 ϭ 4.9 Hz, 1 H, 4Ј-H), 7.18Ϫ7.19
(
Wellington), 2002.
(m, 1 H, 5Ј-H), 7.35 (dd, J1,3 ϭ 1.2 Hz, J1,2 ϭ 5.1 Hz, 1 H, 3Ј-H),
B. Halton, in The Chemistry of the Cyclopropyl Group, Vol. 2,
(Ed.: Z. Rappoport), Wiley, Chichester, 1995, pp. 707Ϫ772.
D. J. Ager, Synthesis 1984, 384; W. P. Weber, Silicon Reagents
for Organic Synthesis, Springer-Verlag: New York, 1983.
S. J. Buckland, B. Halton, Q. Mei, P. J. Stang, Aust. J. Chem.
1987, 40, 1375Ϫ1387.
7
J
6
(
(
2
2
5
1
2
.56 (dd, J1,3 ϭ 1.2, J1,2 ϭ 4.9 Hz, 1 H, 3-H), 7.83 (dd, J1,3 ϭ 1.2,
2,3 ϭ 3.9 Hz, 1 H, 5-H) ppm. 13C NMR (75 MHz, CDCl
): δ ϭ
1.0 (C7), 126.9 (C4Ј), 127.0 (C3Ј), 127.8 (C4), 128.4 (C5Ј), 132.7
3
[
[
18]
19]
C3), 133.4 (C1Ј), 133.8 (C5Ј), 137.7 (C1), 161.9 (C6) ppm. HRMS
ϩ
8 2 2
positive APCI) calcd. for C10H O S [M ϩ H ] 223.9966; found
ϩ
S-y. Onozawa, T. Sakakura, M. Tanaka, M. Shiro, Tetrahedron
1996, 52, 4291Ϫ4302.
23.9959 (Ϫ3.1 mmu). MS (70 eV): m/z (%) ϭ 225 (2) [M ϩ 1 ],
ϩ
ϩ
24 (14) [M ], 179 (3), 111 (59) [M Ϫ O-thienylmethyl ], 97 (100),
7 (13), 53 (18), 39 (55). IR (KBr): ν˜ max ϭ 2930, 1852, 1670, 1564,
329, 1107, 956, 823 cmϪ1. UV/Vis (cyclohexane): λmax (log ε) ϭ
30 (4.00), 268 (3.77), 346 (3.65) nm; (acetonitrile): λmax ϭ 230
[20]
V. Tishchenko, J. Russ. Phys. Chem. Soc. 1906, 38, 355; L.
Claisen, Ber. Dtsch. Chem. Ges. 1887, 20, 646; O. P. Tormak-
angas, A. M. P. Koskinen, Recent Research Developments in
Organic Chemistry 2001, 5(Pt. 1), 225Ϫ255.
B. Halton, A. J. Kay, Z. Zhi-mei, R. Boese, T. Haumann, J.
Chem. Soc., Perkin Trans. 1 1996, 1445Ϫ1452.
Received June 25, 2003
[21]
(4.01), 270 (3.72), 348 (3.63) nm.
Further radial chromatography (light petroleum elution) provided
3
authentic sample. Yield: 53 mg (91%).
,6-dimethoxy-1H-cyclopropa[b]naphthalene (19) identical to an
Early View Article
Published Online October 2, 2003
[
21]
4512
 2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
Eur. J. Org. Chem. 2003, 4507Ϫ4512