Carbo-siloles, part 2: Synthesis and stereochemical resolution of a carbo-silolane redox equivalent

Article abstract of DOI:10.1080/10426500902947922

Carbo-siloles could a priori be generated by eliminative aromatization of sila[5]pericyclyne precursors with adjacent COR and CH vertices. The synthesis of tetraoxy-sila[5]pericyclyne representatives (carbo-silolanes 2a and 2b) has been tackled through se

Full text of DOI:10.1080/10426500902947922

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Carbo-siloles, Part 2: Synthesis
and Stereochemical Resolution
of a Carbo-silolane Redox
Equivalent
Catherine Saccavini a , Christine Tedeschi a ,
Christine Lepetit a , Leila Yahi a , Caroline Pistre a ,
Valérie Maraval a & Remi Chauvin a
a Laboratoire de Chimie de Coordination , Toulouse,
France
Published online: 06 Jun 2009.
To cite this article: Catherine Saccavini , Christine Tedeschi , Christine Lepetit ,
Leila Yahi , Caroline Pistre , Valérie Maraval & Remi Chauvin (2009) Carbo-siloles,
Part 2: Synthesis and Stereochemical Resolution of a Carbo-silolane Redox Equivalent,
Phosphorus, Sulfur, and Silicon and the Related Elements, 184:6, 1573-1585, DOI:
10.1080/10426500902947922
To link to this article: http://dx.doi.org/10.1080/10426500902947922
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Phosphorus, Sulfur, and Silicon, 184:1573–1585, 2009
Copyright © Taylor & Francis Group, LLC
ISSN: 1042-6507 print / 1563-5325 online
DOI: 10.1080/10426500902947922
Carbo-siloles, Part 2: Synthesis and Stereochemical
Resolution of a Carbo-silolane Redox Equivalent
Catherine Saccavini, Christine Tedeschi, Christine
´
Lepetit, Leila Yahi, Caroline Pistre, Valerie Maraval,
and Remi Chauvin
Laboratoire de Chimie de Coordination, Toulouse, France
Carbo-siloles could
a priori be generated by eliminative aromatization of
sila[5]pericyclyne precursors with adjacent C OR and C H vertices. The synthesis
of tetraoxy-sila[5]pericyclyne representatives (“carbo-silolanes” 2a and 2b) has been
tackled through several [(15–n)+n] ring formation strategies. After having first at-
tempted a [14+1] route from dichlorodiphenylsilane and a skipped pentayne (3), a
[5+10] route proceeded successfully from diethynyldiphenylsilane (7) and a triyne-
dial (4), to give the sila[5]pericyclynediol (2a) as a mixture of six diastereomers
in 20% yield. Sequential chromatographies afforded one pure diastereomer of 2a.
DFT calculations of a model dihydroxy, dimethoxy-carbo-silolane indicate an en-
velope conformation of the carbo-meric five-membered ring. Methylation of the two
secondary carbinol vertices of 2a afforded the corresponding tetramethoxy carbo-
silolane (2b) in 68% yield. Aromatization to the targeted carbo-silole by treatment
with Et O·BF of 2b proved awkward.
2
3
Keywords Carbo-mers; β-diynes; pericyclynes; silolane; silole; stereochemical resolu-
tion
INTRODUCTION
To date, efforts for the synthesis of aromatic ring carbo-mers have
been reported in the carbocyclic series only. They were all based
Received 18 January 2008; 12 February 2008.
Dedicated to Professor Marian Mikolajczyk, CBMiM PAN in Lo´dz´, Poland, on the
ꢀ
ꢀ
occasion of his 70th birthday.
The authors wish to thank the Centre National de la Recherche Scientifique and the
Ministe`re de l’Education Nationale, de la Recherche et de la Technologie for financial
support, in particular through ACI fundings. The authors also wish to thank CALMIP
(Calcul intensif en Midi-Pyre´ne´es, Toulouse, France), IDRIS (Institut du De´veloppement
et des Ressources en Informatique Scientifique, Orsay, France), and CINES (Centre
Informatique de l’Enseignement Supe´rieur, Montpellier, France) for computing facilities
and the Ministe`re de l’Education Nationale de la Recherche et de la Technologie for ACI
financial support. Thanks are also due to Dr. Dianne M. Fisher for her valuable comments
and to Miss Katherine Black for a careful final reading.
Address correspondence to Remi Chauvin, Laboratoire de Chimie de Coordination,
205 Route de Narbonne 31077, Toulouse Cedex 4, France. E-mail: chauvin@lcc-toulouse.fr
1573

1574
C. Saccavini et al.
on the retrosynthetic scheme: carbo-[n]annulene => functional [n]
pericyclyne.1 The related heterocyclic carbo-silole ring has been the-
oretically predicted to be an intriguing structure, not only from an
academic standpoint, but also for unweiling new horizons in the de-
sign of functional materials with chromophoric and/or conducting
properties.2 The tetraphenyl representative 1 could be a priori sta-
bilized by extended conjugation, and can be targeted from functional
sila-[5]pericyclynes 2, here termed as “carbo-silolanes.” Double elimi-
nation of methanol from 2 to 1 is indeed a priori a reasonable principle
(Scheme 1).
SCHEME 1 Retrosynthetic scheme to tetraphenyl-carbo-silolanes 2 and
carbo-siloles 1.
According to Scott et al.’s definition,3 “[n]pericyclynes” are 3n-
membered homoconjugated macrocycles. These rings, first exampli-
fied for n = 5 in the hydrocarbon series,3,4 were then generalized in
the functional series by introduction of carbinol vertices (and ether
thereof).5 The C(OR’)R vertices generate stereochemical ambiguity,
but several pentaoxy[5]pericyclynes were stereochemically resolved by
semi-preparative HPLC.5 In principle, the ease of resolution depends
on the number of possible stereoisomers and is simplified for molecules
of high topographical symmetry (e.g., when all vertices are chemically
identical). An ideal way to reduce the number of stereoisomers is to re-
move the stereogenicity of one or more vertices: This was achieved for a
carbo-cyclopentanone equivalent, where the keto vertex was masked
as a symmetrical ketal (C(OR’)2). Symmetrization by two identical

Carbo-silolane Redox Equivalent
1575
non-oxy substituents is however more problematic: a general method
for the preparation of quaternary 1,4-diynes Rꢀ C C C(R2) C C Rꢀ
is indeed missing for R = alkyl, aryl.6 Although double substitution at
X2CR2 vertices is an awkward process, the analogous process at Cl2SiR2
vertices is facilitated by the polarity of the Si–Cl bonds.7
The tetraoxy-tetraphenyl-sila[5]pericyclyne structures 2, namely
the ring carbo-mers of the parent silolanes, are therefore reasonable
targets. The results of two different [(15–n)+n] strategies for the ring
formation step are hereafter reported for n = 1 and n = 10 (Scheme 1).
RESULTS AND DISCUSSION
Attempted [14+1] Ring Formation Route
A [11+4] ring formation strategy based on a double substitution process
was previously explored in the C15 [5]pericyclyne series.8 In the C14Si
series, a generalization of the double substitution strategy has thus
been first attempted from Ph2SiCl2 and the bisacetylide of pentayne 3
(Scheme 1).
Pentayne 3 was previously obtained by reaction of two equivalents
of acetylene magnesium bromide with the triyndial 4.1b The prepara-
tion of 4 is however tedious. In particular, double formylation of the
known triyne 5 required purification by chromatography, resulting in
partial decomposition and affording 4 in a poor 32% yield.4 An alterna-
tive hydroxymethylation-oxidation route was thus explored. Hydrox-
ymethylation of 5 was achieved in excellent yield (95%) by bubbling
formaldehyde gas through a solution of the dilithium salt of 5 (Scheme
2). The diol product 6 was then submitted to various oxidizing reagents
(Swern,9 DCC/Py/TFA,10 BaMnO4/CuSO4/Al2O3,11 etc.), but most of
them were not selective, affording mixtures of mono- and dialdehydes.
The use of a large excess of MnO2 (40 equivalents) in dichloromethane
gave spectroscopically pure triyndial 4 in 29% yield after simple fil-
tration: the side-products (likely resulting from over-oxidation of 6 to
carboxylic acids) thus remain adsorbed on MnO2. Finally, pretreatment
of MnO2 under vacuum at 150◦C for 17 h allowed us to increase the
yield of 4 to 61% (Scheme 2).
SCHEME 2 Preparation of triyndial 4 without a requirement of chromato-
graphic purification.

1576
C. Saccavini et al.
The synthesis of 3 was then performed from 4 according to the de-
scribed method.1b Deprotonation of 3 with four equivalents of EtMgBr
followed by addition of Cl2SiPh2 was unsuccessful: After treatment,
only unreacted 3 and unidentified insoluble (polymeric) products were
recovered. Since the tetraanion of 3 did not precipitate, the lack of
selectivity was likely not due the tetraanionic nature of the nucleophile.
Protection of the OH groups of 3 was therefore not attempted, and we
turned to an alternative ring formation strategy.
[5+10] Ring Formation Route
The alternative [5+10] double addition strategy was devised from the
C4Si β-diyne 7 and the C10 dialdehyde 4 (Scheme 1), the preparation of
which has been improved (see above).
SCHEME 3 Synthesis of carbo-silolanes 2a and 2b.
Diethynylsilane 7 was obtained from two equivalents of ethynyl mag-
nesium bromide and Cl2SiPh2 in 88% yield (Scheme 3).12 The dilithium
salt of 7 (soluble in THF) reacted with triyndial 4 to give a mixture of
the targeted sila[5]pericyclyne 2a along with the unexpected acyclic
C14 pentayne 3. Despite several chromatographic runs, 2a could not be
enriched beyond 80% of purity. The formation of 3, which could result
from a Brook [1,4]rearrangement followed by hydrolysis of the O–Si
bond,13 therefore had to be prevented. Considering that the lithium
alkoxide groups of the product (before hydrolysis) are prone to cleave
the vicinal C Si bonds, deprotonation of 7 was tentatively achieved
with EtMgBr instead of n−BuLi. And indeed, the dimagnesium salt of
7 readily reacted with 4 (over a 1 min reaction time before hydrolysis)
to give the sila[5]pericyclyne 2a as a mixture of six diastereomers, in 20
% yield after chromatography over silica gel (CombiflashꢀR ). The orange
oily product was resolved by further Combiflash chromatography. One
of the diastereomers was thus separated. Since single signals were
obtained for both the CH(OH) and OCH3 types of protons (Figure 1,
top), the structure of this diastereomer is either C2-symmetric (E, F) or
Cs–symmetric (A, B) (Scheme 4).

Carbo-silolane Redox Equivalent
1577
FIGURE 1 1H NMR spectra (250 MHz, CDCl3) of one ideally C2- or Cs-
symmetric diastereomer of 2a (top, structure A, B, E or F in Scheme 4) and a
70:30 mixture of two non-symmetric diastereomers (bottom, structures C and
D in Scheme 4).
A second fraction contained a mixture of two other diastereomers
of 2a in a 70:30 ratio, where both the OCH3 and CH(OH) groups are
in distinct chemical environments (Figure 1, bottom): they can thus be
ascribed to the non-symmetric structures C and D (Scheme 4).
Alkylation of the CH(OH) vertices was achieved with methyl triflate
on a small sample of 2a. The tetramethylether 2b was obtained in
1
68% yield and characterized by MS, IR, H, and 13C NMR analyses
(Scheme 3).
Since no X-ray crystal structure determination of 2a or 2b has been
made possible, the geometry of a model 8F of the carbo-silolane 2a
was investigated theoretically at the B3PW91/6-31G** level of calcula-
tion. The selected stereochemistry corresponds to the stereochemistry

1578
C. Saccavini et al.
SCHEME 4 Haworth representations of the six possible diastereomers of
sila[5]pericyclyne 2a (vertical lines feature C–Ph bonds). The chiral isomer
F has been selected for DFT calculations.
of diastereomer 2aF (Schemes 4 and 5). In the model 8F, the two phenyl
C-substituents of 2a are replaced by H atoms.
Geometrical and electronic features of the calculated structure 8F
(Figure 2) were compared with those of all-carbon [5]pericyclynic
analogues (Scheme 5, Table I). By contrast to the calculated planar
SCHEME 5 Set of representative [5]pericyclynes and sila analogues studied
either experimentally (2aF, 11), or computationally (8F, 9, 10F).

Carbo-silolane Redox Equivalent
1579
TABLE I Comparison of Selected Experimental (XRD) and
Calculated (B3PW91/6-31G**) Geometrical Data in the Carbo-Silolane
and [5]Pericyclyne Series
Bond lengths (Å)
Envelope HOMO LUMO GAP
Si Ph
C–Si CC CSi CC CC Csp–Csp3
folding
(a.u.)
(a.u.)
(eV)
8F (calcd)
1.876 1.834
1.218
1.209 1.466
1.473
1.208 1.466
1.209 1.466,
1.473
16.7◦
−0.2565 −0.0362 5.996
9 (calcd)
10F (calcd)
—
—
—
—
—
—
0◦
−0.2414 −0.0244 7.231
−0.2605 −0.0119 6.763
9.7◦
11 (XRD)[14]
—
—
—
1.190 1.480
40.1◦
—
—
—
—
—
—
—
—
—
—
—
Ph2Si(C CR)2 1.855b 1.822a 1.207a
—
—
—
—
(XRD)
1.816b 1.200b
Distances are given in Å, angles in degrees.
aFrom reference [17].
bFrom reference [18].
structure of unsubstituted [5]pericyclyne 9, the 15-membered ring of
8F is folded by angle θ = 16.7 degrees, where the Si atom is part of a
quasi-planar C9Si moiety. The folding is not only due to the presence of a
silicon atom in the 15-membered ring of 8F: the planarity of the [5]per-
icyclyne 9 also is lost in tetrahydroxy-[5]pericyclyne 10F (θ = 10 de-
grees), displaying the enantiomeric stereochemistry of carbo-silolane
8F. More generally, substitution of [5]pericyclyne 9 induces an out-of-
plane distorsion. Indeed, an envelope conformation was also observed
by X-ray diffraction analysis of decamethyl [5]pericyclyne 11 (θ = 40
degrees),14 and related twisted conformations were obtained by DFT
calculations of various stereoisomers of pentahydroxy[5]pericyclynes.15
FIGURE 2 Calculated structures of the model carbo-silolane 8F (left) and a
related diastereoisomer of tetrahydroxy[5]pericyclyne 10F (right).

1580
C. Saccavini et al.
It is however noteworthy that the global geometry of 8F is very sim-
ilar to that of 10F at the same level of calculation (Table I, Figure 2).
The angle between the Si–phenyl substituent planes of 8F (63 degrees)
falls close to the range (79–84 degrees) observed in related crystallo-
graphic structures of hexaphenylsilole16 or oligoacetylenic silanes.17,18
The calculated bonds lengths are also in quite good agreement with
related available X-ray diffraction data (Table I), thus validating the
calculation level used for 8F and 10F. As previously recognized,19 the
calculated bond distances are just slightly longer than those suggested
by X-ray diffraction data.
CONCLUSION
The first functional sila[5]pericyclynes 2a and 2b have been obtained
via a [5+10] cyclization route in nine and ten steps (including the
previously described preparation of triyne 5), in 4.5% and 3% overall
yields, respectively. For this purpose, an improved preparation of the
key triyndial 4 has been developed. One of the five vertices (SiPh2)
being not stereogenic, the reduced number of diastereomers (six in all)
allowed us to purify one of them by silica gel chromatography (for the
carbo-cyclopentane analogues, the use of semi-preparative HPLC tech-
niques had been necessary).5 In the absence of crystallographic data
for 2a, the geometry of a model stereoisomer (10F) has been studied at
the DFT level. The optimized geometry of 10F is envelope-shaped, as
already observed for related substituted all-carbon [5]pericyclynes, but
the silicon atom does not occupy the tip of the envelope. Non-reducing
eliminative aromatization of 2b was attempted with two equivalents
of a Lewis acid (Et2O·BF3) in dichloromethane, but the expected carbo-
silole 1 could not be detected beside polymeric products. In spite of this
failure, both carbo-silolanes 2a and 2b can be regarded as redox (or
isohypsic) equivalents of 1 after elimination of two MeOH molecules.
Further investigations will focus on the aromatization step. Keeping
in mind the ultimate potential applications in material sciences,2 the
numerous physicochemical properties of the silole core20 could indeed
be tuned in its ring carbo-mer and justify these efforts.
EXPERIMENTAL
General
All reagents were used as their commercially available form
(from Acros Organics, Avocado, Aldrich, Lancaster, Strem) without

Carbo-silolane Redox Equivalent
1581
further purification. THF and diethylether were dried and dis-
tilled on sodium/benzophenone, pentane, and dichloromethane on
P2O5. Commercial solutions of EtMgBr are 3M in diethylether.
Commercial solutions of n−BuLi are 1.6 or 2.5 M in hexane, and
their effective concentrations were checked by titration with 2,2,
2ꢀ-trimethylpropionanilide.21 All reactions were conducted under ei-
ther a nitrogen or argon atmosphere, using Schlenk and vacuum line
techniques. Thin layer chromatography plates were purchased from
SDS (60F254, 0.25 mm) and revealed by treatment with an ethano-
lic solution of phosphomolybdic acid (20%). Column chromatographies
were carried out with SDS silicagel (60 Å, 70–200 µ m). Special chro-
matographies were performed with a Combiflash Graduate ISCO Sys-
tem on Normal Phase Silice packs. The following analytical instru-
ments were used: IR: 0.1 mm CaF2 cell, Perkin-Elmer GX FT-IR; 1H and
13C NMR: Brucker AC 200, WM 250, DPX 300, or AMX 400; Mass spec-
trometry: Quadrupolar Nermag R10-10H; Elemental analyses: Perkin-
Elmer 2400 CHN (flash combustion and detection by catharometry).
IR absorption frequencies ν are in cm−1. NMR chemical shifts δ are in
ppm, with positive values to high frequency relative to the tetramethyl-
silane reference; coupling constants J are in Hz. As most compounds
were isolated as oily mixtures of diastereomers, characteristic assign-
ments are given in order to trace the analytical consistency within the
quite homogeneous series of compounds.
Syntheses
4,7-Dimethoxy-4,7-diphenyldeca-2,5,8-triyndial (4)
To a solution of 6 (100 mg, 0.267 mmol) in CH2Cl2 (10 mL) at 0◦C,
MnO2 (928 mg, 10.7 mmol) was added after having been activated by
drying under vacuum (10−2 mbar) for 17 h at 150◦C. After 30 min at
0◦C and 5 h 30 min at r.t., the reaction mixture was filtered over celite
and concentrated under reduced pressure to give 4 as a yellow oil (60
mg, 61%). The spectroscopic data were identical to those previously
reported.1b
4,7-Dimethoxy-4,7-diphenyldeca-2,5,8-triyn-1,10-diol (6)
A solution of n−BuLi (14 mL, 32 mmol) was added dropwise to a
solution of 5 (4.6 g, 14.6 mmol) in THF (150 mL) at –78◦C. The reaction
mixture was warmed to –40◦C for 10 min and at –40◦C, fresh formalde-
hyde (dried over drierite and just formed from p-formaldehyde heated
at 165◦C) was bubbled via a needle into the solution for 2 h and an-
other 1 h at –20◦C. The bubbling was then stopped, and the solution

1582
C. Saccavini et al.
was stirred for 30 min at –20◦C followed by 30 min at r.t. The re-
action mixture was then quenched with the addition of a saturated
NH4Cl solution and washed with a solution of KOH (5%) to neutralize
potential excess of formaldehyde. Further addition of saturated aque-
ous NH4Cl decreased the pH to 7. The aqueous layer was extracted
with Et2O, and the combined organic layers were washed with brine,
dried over anhydrous MgSO4, and concentrated under reduced pres-
sure. The residue was chromatographied over silica gel (heptane/AcOEt
2:8) to give 6 as an orange oil (5.21 g, 95%). Rf ≈ 0.35 (heptane/AcOEt
4:6). MS (DCI/NH3): m/z = 392 ([M+NH4]+), 360 ([M+NH4–MeOH]+),
343 ([M+H–MeOH]+). 1H NMR (200 MHz, CDCl3): δ = 2.81 (s, 2
H, O-H), 3.46, 3.49 (s, 6 H, OCH3), 4.27 (s, 4 H, CH2OH), 7.32–7.41
(m, 6 H, m-, p-C6H5), 7.69–7.75 (m, 4 H, o-C6H5). 13C NMR (63 MHz,
1
1
CDCl3): δ = 50.71 (t, JC−H = 148 Hz, CH2OH), 53.25 (q, JC−H = 144
Hz, OCH3), 71.85 [s, PhC(OMe)], 82.27 (s, Ph C–C C C Ph), 84.36
(s, C C CH2OH), 85.74 (s, C C CH2OH), 125.10–130.44 (m, o-, m-,
p − C6H5), 139.60 (s, ipso-C6H5–COMe). IR (CDCl3): ν = 3423 (m, O–H),
2935 (m, Csp3 H), 2826 (m, OCsp3 H), 1599, 1490 and 1453 (m, C C),
1068 (m, C–O).
Diethynyldiphenylsilane (7)
A solution of ethynylmagnesium bromide (45.7 mL, 22.8 mmol) was
added dropwise to a solution of dichlorodiphenylsilane (1.2 mL, 5.7
mmol) in THF (20 mL) at 0◦C. After stirring for 15 min at 0◦C and
17 h at r.t., the solution was treated with saturated NH4Cl solution.
The organic layer was extracted with Et2O, washed with brine, dried
over anhydrous MgSO4, and concentrated under reduced pressure to
give 7 as a red oil (1.158 g, 88%). Rf ≈ 0.37 (heptane/AcOEt 9:1). MS
1
(DCI/NH3): m/z = 267 ([M+N2H7]+), 250 ([M+NH4]+). H NMR (250
MHz, CDCl3): δ = 2.79 (s, 2 H, C H), 7.46–7.48 (m, 6 H, m-, p-C6H5),
1
7.81–7.84 (m, 4 H, o−C6H5). 13C{ H} NMR (63 MHz, CDCl3): δ = 83.40
(C CH), 97.55 (C C H), 128.29 (Cm of Ph), 130.72 (Cp of Ph), 131.29
(Ci of Ph), 134.83 (Co of Ph). IR (CDCl3): ν = 3288 (Csp–H), 3073 and
3055 (Csp2–H), 2926 (Csp3–H), 2042 (C C), 1589, 1486 and 1430 (C C
of cycle).
7,10-Dimethoxy-1,1,7,10-tetraphenyl-1silacyclopentadeca-
2,5,8,11,14-pentayn-4,13-diol (2a)
A solution of 7 (200 mg, 0.86 mmol) in THF (50 mL) was treated with
EtMgBr (574 µL, 1.72 mmol) at 0◦C. After stirring for 30 min at 0◦C
and 2 h at r.t., a solution of triyne dialdehyde 4 (319 mg, 0.86 mmol)
in THF (100 mL) was added dropwise. After stirring 1 min at r.t., the

Carbo-silolane Redox Equivalent
1583
solution was treated with saturated NH4Cl solution. The organic layer
was extracted with Et2O, washed with brine, dried over anhydrous
MgSO4, and concentrated under reduced pressure. Purification through
silica Combiflash column chromatography (heptane/AcOEt 8:2) gave
2a as an orange oil (107 mg, 20%). Rf ≈ 0.08 (heptane/AcOEt 8:2).
MS (DCI/NH3): m/z = 620 ([M+NH4]+), 588 ([M–MeO−+NH3]+), 571
([M+H–MeOH]+). 1H NMR (250 MHz, CDCl3): δ = 2.48 (s, br, 2 H, O–
H), 3.42–3.58 (m, 6 H, OCH3), 5.23–5.30 (m, 2 H, CH–OH), 7.32–7.46
1
(m, 12 H, m-, p-C6H5), 7.66–7.78 (m, 8 H, o−C6H5). 13C{ H} NMR (63
MHz, CDCl3): δ = 52.78 (OCH3), 53.50 (CHOH), 71.92 (C–OMe), 80.99–
83.72 (C C), 104.25 (C C–Si), 126.51–129.12 (Cm, Co et Cp of Ph-C and
Cp of Ph-Si), 130.79 (Cm of Ph-Si), 134.90 (Co of Ph-Si), 139.12, 139.21
(Ci of Ph-Si and Ci of Ph-C). IR (CDCl3): ν = 3584 (O–H), 3073 (Csp2–H),
2935 (Csp3–H), 2186 (CC CC), 2042 (SiC CC), 1590, 1490, 1450 and
1430 (C C of cycle), 1068 (C O).
4,7,10,13-Tetramethoxy-1,1,7,10-tetraphenyl-1-
silacyclopentadeca-2,5,8,11,14-pentayne (2b)
A solution of pentayne 2a (24 mg, 0.04 mmol) in Et2O (10 mL) was
treated with n−BuLi (32 µL, 0.08 mmol) for 3 min at –78◦C. Methyl
triflate (13 µL, 0.12 mmol) was then added dropwise. The tempera-
ture was allowed to warm to 0◦C and the stirring was continued for
17 h at 0◦C. After neutralization with NaHCO3 (5%), the organic layer
was hydrolized with saturated NH4Cl solution, extracted with Et2O,
washed with brine, dried over anhydrous MgSO4, and concentrated
under reduced pressure to give 2b as an orange oil (17 mg, 68%).
MS (DCI/NH3): m/z = 648 ([M+NH4]+), 616 ([M–MeO−+NH3]+), 599
1
([M+H–MeOH]+). H NMR (250 MHz, CDCl3): δ = 3.40–3.62 (m, 12
H, OCH3), 5.14–5.21 (m, 2 H, CH–OMe), 7.31–7.45 (m, 12 H, m-, p-
1
C6H5), 7.66–7.79 (m, 8 H, o−C6H5). 13C{ H} NMR (100 MHz, CDCl3):
δ = 54.05 (PhC OCH3), 55.33 (HC OCH3), 60.76 (H C OMe), 69.97
(Ph C OMe), 80.96–84.89 (C C), 102.41 (C C Si), 126.88–131.34
(Cm, Co and Cp of Ph-C and Cp of Ph-Si), 128.64 (Cm of Ph–Si), 135.27 (Co
of Ph–Si), 139.76, 139.90 (Ci of Ph–Si and Ci of Ph–C). IR (CDCl3): ν =
3073 (Csp2–H), 2952 and 2933 (Csp3–H), 2182 (CC CC), 2038 (SiC CC),
1589, 1490, 1450 and 1430 (C C of cycle), 1074 (C O).
Computational Details
Geometries were fully optimized (under symmetry constraint when
possible) at the B3PW91/6-31G∗∗ level in the singlet spin state, using
Gaussian98.22 Vibrational analysis was performed at the same level in

1584
C. Saccavini et al.
order to check that a minimum was obtained on the potential energy
surface.
REFERENCES AND NOTES
[1] (a) V. Maraval and R. Chauvin, Chem. Rev., 106, 5317 (2006); (b) C. Saccavini, C.
Tedeschi, L. Maurette, C. Sui-Seng, C. Zou, M. Soleilhavoup, L. Vendier, and R.
Chauvin, Chem. Eur. J., 13, 4895 (2007); (c) C. Saccavini, C. Sui-Seng, L. Maurette,
C. Lepetit, S. Soula, C. Zou, B. Donnadieu, and R. Chauvin, Chem. Eur. J., 13, 4914
(2007); (d) C. Zou, C. Duhayon, V. Maraval, and R. Chauvin, Angew. Chem. Int. Ed.,
46, 4337 (2007); (e) L. Leroyer, C. Zou, V. Maraval, and R. Chauvin, C. R. Chimie,
12, 412 (2009).
[2] C. Lepetit and R. Chauvin, Phosphorus, Sulfur, and Silicon, 184, 1561 (2009).
[3] L. T. Scott, G. J. DeCicco, J. L. Hyunn, and G. Reinhardt, J. Am. Chem. Soc., 105,
7760 (1983).
[4] K. N. Houk, L. T. Scott, N. G. Rondan, D. C. Spellmeyer, G. Reinhardt, J. L. Hyun,
G. J. DeCicco, R. Weiss, M. H. M. Chen, L. S. Bass, J. Clardy, F. S. Jorgensen, T.
A. Eaton, V. Sarkosi, C. M. Petit, L. Ng, and K. D. Jordan, J. Am. Chem. Soc., 107,
6546 (1985).
[5] L. Maurette, C. Tedeschi, E. Sermot, F. Hussain, M. Soleilhavoup, B. Donnadieu,
and R. Chauvin, Tetrahedron, 60, 10077 (2004).
[6] (a) C. Tedeschi, C. Saccavini, L. Maurette, M. Soleilhavoup, and R. Chauvin, J.
Organomet. Chem., 670, 151 (2003); (b) V. Maraval, C. Duhayon, Y. Coppel, and R.
Chauvin, Eur. J. Org. Chem., 5144 (2008).
[7] W.-Y. Wong, A. W.-M. Lee, C.-K. Wong, G.-L. Lu, H. Zhang, T. Mo, and K.-T. Lam,
New J. Chem., 26, 354 (2002).
[8] L. Maurette, C. Godard, S. Frau, C. Lepetit, M. Soleilhavoup, and R. Chauvin,
Chem. Eur. J., 7, 1165 (2001).
[9] A. J. Mancuso, S. L. Huang, and D. Swern, J. Org. Chem., 43, 2480 (1978).
[10] E. J. Corey and G. Schmidt, Tetrahedron Lett., 20, 399 (1979).
[11] P. J. DeClercq and L. A. Van Royen, Synth. Commun., 9, 771 (1979).
[12] U. Kruerke, J. Organomet. Chem., 21, 83 (1970).
[13] A. G. Brook, Acc. Chem. Res., 7, 77 (1974).
[14] (a) K. N. Houk, L. T. Scott, N. G. Rondan, D. C. Spellmeyer, G. Reinhardt, J. L. Hyun,
G. J. DeCicco, R. Weiss, M. H. M. Chen, L. S. Bass, J. Clardy, F. S. Jrargensen, T. A.
V. Sarkozi, C. M. Petit, L. Ng, and K. D. Jordan, J. Am. Chem., 107, 6556 (1985).
[15] C. Zou, C. Lepetit, Y. Coppel, and R. Chauvin, Pure and Applied Chem., 78, 791
(2006).
[16] J. Chen, C. C. W. Law, J. W. Y. Lam, Y. Dong, S. M. F. Lo, I. D. Williams, D. Zhu, and
B. Z. Tang, Chem. Mater., 15, 1535 (2003).
[17] L. Guo, J. D. Bradshaw, D. B. McConville, C. A. Tessier, and W J. Youngs,
Organometallics, 16, 1685 (1997).
[18] W.-Y. Wong, A. W.-M Lee, C.-K. Wong, G.-L. Lu, H. Zhang, T. Mo, and K.-T. Lam,
New J. Chem., 26, 354 (2002).
[19] B. Ma, H. M. Sulzbach, Y. Xie, and H. F. Schaefer III, J. Am. Chem. 116, 3529 (1994).
[20] (a) K. Tamao and S. Yamaguchi, J. Organomet. Chem., 611, 5 (2000); (b) B.-H. Kim
and H.-G. Woo, Organometallics, 21, 2796 (2002); (c) Y. Matsuzaki, M. Nakano, K.
Yamaguchi, K. Tanaka, and T. Yamabe, Chem. Phys. Lett., 263, 119 (1996); (d) P.
Dufour, M. Dartiguenave, Y. Dartiguenave, and J. Dubac, Organometallics, 9, 2832
(1990).

Carbo-silolane Redox Equivalent
1585
[21] J. Suffert, J. Org. Chem., 54, 509 (1989).
[22] M. J. Frisch et al. M. J. Frisch, G. W. Trucks, H. B. Schlegel, G. E. Scuseria, M.
A. Robb, J. R. Cheeseman, J. A. Montgomery, Jr., T. Vreven, K. N. Kudin, J. C.
Burant, J. M. Millam, S. S. Iyengar, J. Tomasi, V. Barone, B. Mennucci, M. Cossi, G.
Scalmani, N. Rega, G. A. Petersson, H. Nakatsuji, M. Hada, M. Ehara, K. Toyota,
R. Fukuda, J. Hasegawa, M. Ishida, T. Nakajima, Y. Honda, O. Kitao, H. Nakai,
M. Klene, X. Li, J. E. Knox, H. P. Hratchian, J. B. Cross, V. Bakken, C. Adamo, J.
Jaramillo, R. Gomperts, R. E. Stratmann, O. Yazyev, A. J. Austin, R. Cammi, C.
Pomelli, J. W. Ochterski, P. Y. Ayala, K. Morokuma, G. A. Voth, P. Salvador, J. J.
Dannenberg, V. G. Zakrzewski, S. Dapprich, A. D. Daniels, M. C. Strain, O. Farkas,
D. K. Malick, A. D. Rabuck, K. Raghavachari, J. B. Foresman, J. V. Ortiz, Q. Cui,
A. G. Baboul, S. Clifford, J. Cioslowski, B. B. Stefanov, G. Liu, A. Liashenko, P.
Piskorz, I. Komaromi, R. L. Martin, D. J. Fox, T. Keith, M. A. Al-Laham, C. Y. Peng,
A. Nanayakkara, M. Challacombe, P. M. W. Gill, B. Johnson, W. Chen, M. W. Wong,
C. Gonzalez, and J. A. Pople, Gaussian 98, Revision A.9, Gaussian, Inc., Pittsburgh,
PA, 1998.