Sterically hindered cyclic diynes - Syntheses and structures

Article abstract of DOI:10.1002/ejoc.200300151

The synthesis of three 14-membered ring systems 8a-8c with the 1,3,8,10-tetraoxa-2,9-disilacyclotetradeca-5,12-diyne skeleton is described. In all three ring systems the α-positions are substituted with gem-dimethyl and/or gem-diphenyl groups. Structural investigations on 8a and 8c reveal a chair like conformation of the central ring with parallel alkyne units. For 8b the voluminous phenyl groups cause a twist-chair and a twist-boat conformation. Columnar structures were encountered for 8a in the solid state. Reactions with octacarbonyldicobalt yield for 8a mono- and biscomplexation (12, 13). For 8b only the mono complexation product 14 was isolated. For 8c the bis(hexacarbonyldicobalt) complex 15 was obtained. X-ray investigations revealed columnar structures in the solid state for 12, 13, and 15. Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003.

Full text of DOI:10.1002/ejoc.200300151

FULL PAPER
Sterically Hindered Cyclic Diynes ؊ Syntheses and Structures
Carsten Schaefer,[a] Rolf Gleiter,*[a] and Frank Rominger[a]
Keywords: Heterocycles / Steric hindrance / Cobalt / Alkynes / Intermolecular forces
The synthesis of three 14-membered ring systems 8a−8c
were encountered for 8a in the solid state. Reactions with
with the 1,3,8,10-tetraoxa-2,9-disilacyclotetradeca-5,12-diyne octacarbonyldicobalt yield for 8a mono- and biscomplexation
skeleton is described. In all three ring systems the α-positions
are substituted with gem-dimethyl and/or gem-diphenyl
groups. Structural investigations on 8a and 8c reveal a chair
like conformation of the central ring with parallel alkyne
units. For 8b the voluminous phenyl groups cause a twist-
chair and a twist-boat conformation. Columnar structures
(12, 13). For 8b only the mono complexation product 14 was
isolated. For 8c the bis(hexacarbonyldicobalt) complex 15
was obtained. X-ray investigations revealed columnar
structures in the solid state for 12, 13, and 15.
( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
Germany, 2003)
Introduction
Cyclic alkynes with methyl groups in the positions adjac-
ent to the triple bonds are rare but not unknown.[1Ϫ6] One
of the most prominent members of the family of cyclic
monoalkynes is 1-thia-3,3,6,6-tetramethyl-4-cycloheptyne
(1) and those congeners in which the sulfur atom is replaced
by a CH2, a SO2, or a SiMe2 group.[7] For 1 a rich and
partly unexpected chemistry has been unravelled (Scheme 1)
which was ascribed to steric effects and the bent triple
bond.[8,9] As an example Scheme 1 shows the generation of
the first stable cyclobutadiene derivative, 3, resulting
from 1.
Scheme 2
Scheme 3. Irradiation of 7 in the presence of CpMn(CO)3
yielded the species 16 and 17 which demonstrate a skeletal
rearrangement.[10] A related rearrangement was also re-
ported when 7 was heated with Fe(CO)5 or Fe2(CO)9.[11]
These differences prompted us to synthesise cyclic diynes
with bulky CR2 groups adjacent to the triple bonds such as
8aϪc (Scheme 4).
Scheme 1
The results reported for 1 encouraged us to look for ways
to prepare cyclic diynes with bulky substituents in positions
adjacent to the triple bonds. Most candidates known so far
which fulfil the steric requirements are those with dimethyl-
silyl groups next to the triple bonds such as 4Ϫ6[1Ϫ6] de-
picted in Scheme 2.
The weaker CϪSi bond as compared to a CϪC bond
often causes quite unexpected chemistry, as shown in
[a]
Organisch-Chemisches Institut, Universität Heidelberg,
INF 270, 69120 Heidelberg, Germany
Fax: (internat.) ϩ49Ϫ(0)6221/544205
E-mail: rolf.gleiter@urz.uni-heidelberg.de
Scheme 3
Eur. J. Org. Chem. 2003, 3051Ϫ3059
DOI: 10.1002/ejoc.200300151
 2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
3051

C. Schaefer, R. Gleiter, F. Rominger
FULL PAPER
Scheme 4
Results and Discussion
Synthesis
The synthesis of 8 is straightforward and is summarised
in Scheme 5. It commences with the reaction of 2-methyl-
3-butyn-2-ol (9) with either dimethyldichlorosilane (R1 ϭ
CH3) or diphenyldichlorosilane (R1 ϭ C6H5) to yield the
dialkynes 10a and 10c respectively. The bis(lithium) salt of
10a and 10c can be converted into the bis(alcohols) 11aϪc
by reaction with acetone or benzophenone.
Figure 1. Molecular structures of 8a, 8c and the two independent
molecules of 8b; the hydrogen atoms have been omitted for clarity.
The oxygen atoms are represented by full circles
the literature.[12] The actual ring conformation of 8a and
8c is compared to the chair conformation in Figure 2. The
substituents at the silicon evade the substituents at the α-
position to the triple bonds so that the bridge deviates
strongly from the ideal zigzag arrangement. This brings the
butyne-units closer together in a parallelogram like arrange-
ment. In Table 1 the most relevant structural parameters of
8aϪc are listed. A comparison with the transannular dis-
tances of cyclotetradeca-4,11-diyne (464 pm), cyclotetra-
deca-4,11-diyne-1,8-dione (520 pm), and 1,8-dioxacyclote-
tradeca-4,11-diyne (471 pm)[12] shows that the transannular
distances in all three cyclic diynes 8aϪc are shorter.
Scheme 5. Reagents: (i) R1 SiCl2, DMAP, CH2Cl2; (ii) nBuLi,
2
THF; (iii) R2 CO; (iv) R3 SiCl2, DMAP, CH2Cl2
2
2
Further condensation of 11aϪc with R3 SiCl2 afforded
2
the final products 8aϪc. The yields for the various steps
vary strongly. The overall yield is 25% for 8a and decreases
to 4% (8b) and 19% (8c) when the substituents change to
C6H5.
Figure 2. Ring conformation of 8a and 8c in the solid state (left;
substituents at the silicon are omitted) and chair conformation for
cyclotetradeca-1,8-diyne (right)
Structural Investigations
All three final products of the reaction sequence in
Scheme 5 were colourless solids from which crystals were
obtained. In Figure 1 the molecular structures of 8aϪc are
shown.
Table 1. Transannular distances between the triple bonds, torsion
angles between the triple bonds and bond angles at the sp-centres
of 8a؊8c
In all three cyclic diynes the geometry of the 14-mem- Compound Distance d [a]/pm Torsion γ[a] /° CϪCϵC angles /°
bered ring is determined by the rigid and linear 1,1,4,4-
8a
8b
8c
450.1
364.5/384.8
419.3
0
176.7Ϫ177.0
174.3Ϫ179.5
175.1Ϫ177.5
tetrasubstituted 2-butyne units. These parts are bridged at
both ends by a bent OϪSiϪO bridge. For 8a and 8c a chair
like conformation results with parallel alkyne units, similar
to several cyclotetradeca-4,11-diyne derivatives reported in
59.4/61.8
0
[a]
See Figure 7 for illustration of distance d and torsion angle γ.
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Sterically Hindered Cyclic Diynes
FULL PAPER
For 8b we found two independent molecules in the unit
cell. One molecule adopts a twisted boat-like conformation
while the other molecule adopts a twisted chair-like confor-
mation as can be seen in Figure 3. These structures are
mainly due to a minimisation of steric interactions between
the two pairs of bulky diphenylmethano and the diphenylsi-
lano units. In the resulting conformations the torsional
angles between the opposite triple bonds are found to be
61.5° and 64.8° respectively. The torsional angle γ is illus-
trated in Figure 7.
Figure 5. CϪH···O interactions within the columnar structure of
8a. The silicon centres are hatched, the oxygen atoms are rep-
resented by full circles
Figure 3. Different ring conformations of 8b in the unit cell:
Twisted boat-like conformation (top), twisted chair-like confor-
mation (bottom); all substituents have been omitted for clarity. The
oxygen atoms are represented by full circles
alt is a well established method in organometallic chemis-
try.[16] We used this reaction to investigate whether the steri-
cally hindered alkynes were still able to be attacked at the
triple bonds. Recently, unsubstituted cyclic diynes were in-
vestigated regarding their reactivity towards octacarbonyl-
dicobalt and it was shown that these diynes afford the two-
fold complexes in good yields.[17] To test the reactions with
cobaltcarbonyls we treated 8aϪc with an excess of octacar-
bonyldicobalt in dichloromethane at room temperature
For 8a we noticed in the solid state the appearance of a
columnar structure. This structure arises by stacking the
rings on top of each other (see Figure 4). In the solid state
of 8a we find interactions between the CϪH bonds of the
methyl groups of one entity and the oxygen atoms of the
other (Figure 5). The H···O intermolecular distance
˚
˚
amounts to 2.703 A (C···O distance 3.603 A). This value is
similar to that found for weak H···O bonds.[13Ϫ15]
Figure 4. Columnar structure of 8a in the solid state (view along a
axis of the unit cell)
Reactions with Octacarbonyldicobalt
The formation of hexacarbonyldicobalt complexed
alkynes by the reaction of alkynes with octacarbonyldicob- Scheme 6
Eur. J. Org. Chem. 2003, 3051Ϫ3059
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3053

C. Schaefer, R. Gleiter, F. Rominger
FULL PAPER
(Scheme 6). In the case of 8a the use of 4 equivalents of methyl groups which make the attack at the triple bonds
octacarbonyldicobalt afforded the mono complexed prod- difficult. By the use of 8 equivalents of octacarbonyldico-
uct 12 in 30% yield. We ascribe this result to the bulky balt the twofold complexed product 13 could be isolated in
45% yield. When reacting the cyclic diyne 8b with octacar-
bonyldicobalt, even 10 equivalents of octacarbonyldicobalt
lead only to the formation of the mono complexed product
14 in 25% yield. This decrease in reactivity can be attributed
to the extreme shielding of the triple bond by the phenyl
groups. In the case of 8c the reaction with 10 equivalents
of octacarbonyldicobalt afforded the twofold complexed
product in 79% yield. All yields are lower than for the anal-
ogous unsubstituted all-carbon ring, 1,8-cyclotetradeca-
diyne, which affords the twofold complexed product in
90% yield.[17,18]
Table 2. Transannular distances between the (former) triple bonds,
torsion angles between the (former) triple bonds, and bond angles
at the (former) sp centres of 12؊15
Compound Distance d [a]/pm Torsion γ[a] /° CϪCϵC angles /°
12
13
14
519.5
632.2
534.6
5.3
70.3
17.9
141.4/172.8Ϫ172.9
141.1Ϫ143.3
143.9Ϫ144.8/
169.4Ϫ175.8
15
648.3
0
144.4Ϫ145.6
[a]
For all isolated complexes, single crystals were obtained
from a mixture of ethanol and diethyl ether at 4 °C. As an
example, the molecular structures of 13 and 15 are shown
in Figure 6. The most relevant distances and angles of
12؊15 are compiled in Table 2. The transannular distance
d and the torsion angle γ is illustrated in Figure 7.
See Figure 7 for illustration of distance d and torsion angle γ.
Figure 7. Illustration of the triple bond length d (the transannular
distance between the triple bond centres or former triple bond
centres, respectively) and the torsion angle γ (the torsion angle 1
Ϫ centre 1,2 Ϫ centre 3,4Ϫ4)
The distances between the metal atoms, between Co and
CO, as well as the CϪC distances for the former triple bond
compare well with those reported for Co2(CO)6 complexes
of cyclic diynes.[17] As anticipated, the distance between one
complexed triple bond and one uncomplexed (12, 14) is
considerably shorter than between two complexed triple
bonds.
It is also noteworthy that 12, 13, and 15 (Figure 8) form
columnar structures in the solid state. In the case of 15 the
dipolar interactions between CO groups of neighbouring
molecules are found within the column (Figure 9). The
Figure 6. Molecular structures of 13 and 15; the hydrogen atoms
have been omitted for clarity. The oxygen atoms are represented by
full circles
Figure 8. Columnar structure of 15 in the solid state (view along a axis of the unit cell)
3054 www.eurjoc.org
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Eur. J. Org. Chem. 2003, 3051Ϫ3059

Sterically Hindered Cyclic Diynes
FULL PAPER
˚
O···CO contacts (3.056 and 3.161 A) are shorter than the
In the case of 12 and 13 the interactions within the crys-
sum of the van der Waals radii.[15] Between the columns tal are less clear cut and more difficult to visualise than for
there are CϪH···O interactions (2.584 A, C···O distance 15. Therefore we summarise the observed intermolecular
3.499 A) between phenyl groups and CO units (Figure 10). short contacts. In the crystal structure of 12 we find dipolar
˚
˚
These intermolecular interactions seem to be partially re- interactions between CO groups within the columns
˚
sponsible for the columnar arrangement in the solid state. (3.194 A) and CϪH···O interactions between the columns
˚
˚
The distances found are in the same order of those reported (2.685 A, C···O distance 3.706 A). In the crystal structure of
in the literature.[13]
13 there are again dipolar interactions between CO groups
˚
within the columns (3.184 A) and also between the columns
˚
(3.162 A) as well as CϪH···O interactions between the col-
˚
˚
umns (2.686 A, C···O distance 3.432 A).
Conclusion
Starting from 2-methyl-3-butyn-2-ol we were able to de-
sign a simple and short route to prepare sterically hindered
cyclic diynes with the 1,3,8,10-tetraoxa-2,9-disilacyclotetra-
deca-5,12-diyne skeleton. The gem-dimethyl and gem-di-
phenyl groups in the α-position of the triple bonds and at
the silicon atoms influence the conformation of the 14-
membered ring in so far as the expected zigzag arrangement
of the CR2ϪOϪSiR2ϪOϪCR2 chain is not adopted in the
solid state. For 8b the expected chair like conformation is
not possible. A boat like twisted and chair like twisted con-
formation is preferred instead. The steric hindrance of the
triple bonds also shows up in the reactivity with Co2(CO)8.
To get the bis complexation, an eightfold excess had to be
used and in the case of 8b even a tenfold excess yielded only
the mono complexed species 14. It is interesting to note that
the rings of 8a, 12, 13, and 15 show columnar stacking in
the solid state. In the case of 8a this observation could par-
tially be traced back to weak CϪH···O interactions. For 12,
13, and 15 we assume that the columnar stacking is a result
of dipolar interactions between the CO groups and weak
CϪH···O bonds between the oxygen centres of the CO
groups and the CϪH groups of the phenyl ring.
Figure 9. O···CO interactions within the columnar structure of 15
(phenyl substituents are omitted for clarity). The silicon centres are
hatched, the oxygen atoms are represented by full circles
Experimental Section
General Remarks: All melting points are uncorrected. The NMR
spectra were measured with a Bruker WH 300 or Avance 500 spec-
trometer (1H NMR at 300 or 500 MHz and 13C NMR at 75 or
125 MHz) using the solvent as internal standard (δ). The mass
spectra refer to data from a JEOL JMS-700 instrument. IR spectra
were recorded with a Bruker Vector 22 FT-IR spectrometer. UV/
Vis absorption data were recorded using a Hewlett Packard HP
8452A Diode Array-spectrometer. Elemental Analysis: Microana-
lytical laboratory of the University of Heidelberg. All reactions
were carried out under an argon atmosphere using dried and oxy-
gen-free solvents.
X-ray Crystallographic Study: Data were collected on a Bruker
Smart CCD-diffractometer at 200 K. Relevant crystal and data col-
lection parameters are given in Tables 3 and 4. The structures were
solved by direct methods and refined against F2 with a full-matrix
least-square algorithm by using SHELXTL-97[19] software. In all
cases an empirical absorption correction was applied by using SA-
DABS,[20] based on the Laue symmetry of the reciprocal space.
Figure 10. CϪH···O interactions between the columns of 15. The
silicon centres are hatched, the oxygen atoms are represented by
full circles
Eur. J. Org. Chem. 2003, 3051Ϫ3059
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C. Schaefer, R. Gleiter, F. Rominger
FULL PAPER
Table 3. Crystal data and structural refinement for 8a, 8b, and 8c
8a
8b
8c
Empirical formula
Molecular mass
Wavelength [A]
C20H36O4Si2
396.67
0.71073
C50H48O4Si2
769.06
0.71073
C40H44O4Si2
644.93
0.71073
˚
Crystal system
Space group
triclinic
P1
triclinic
P1
triclinic
P1
¯
¯
¯
Temp. [K]
200(2)
1
200(2)
4
200(2)
1
Z
a
b
c
7.6905(1)
8.8782(2)
9.2541(1)
103.407(1)
107.154(1)
91.458(1)
584.3
11.2936(3)
19.5588(5)
20.0941(5)
80.151(1)
89.200(1)
80.780(1)
4316.2
9.8850(1)
9.8861(1)
11.4361(1)
69.514(1)
75.144(1)
61.628(1)
915.6
α
β
γ
3
˚
V [A ]
Dcalcd. [g/cm3]
1.13
0.17
1.18
0.13
1.17
0.14
Abs. coeff. µ [mmϪ1
]
Max./min. transmission
Crystal shape
0.82/0.98
polyhedron
0.39 ϫ 0.20 ϫ 0.14
2.4 to 27.5
Ϫ9Յ h Յ9
Ϫ11Յ k Յ11
Ϫ12Յ l Յ12
6102
2660 (0.0297)
2308 [I Ͼ 2σ(I)]
2660/0/190
1.06
0.49/0.98
polyhedron
0.36 ϫ 0.36 ϫ 0.14
1.0 to 24.1
Ϫ12Յ h Յ12
Ϫ22Յ k Յ22
Ϫ23Յ l Յ23
34568
13670 (0.0432)
9719 [I Ͼ 2σ(I)]
13670/0/1021
1.03
0.73/0.97
polyhedron
0.44 ϫ 0.34 ϫ 0.22
1.9 to 27.5
Ϫ12Յ h Յ12
Ϫ12Յ k Յ12
Ϫ14Յ l Յ14
9426
4143 (0.0238)
3554 [I Ͼ 2σ (I)]
4143/0/212
1.04
Crystal size [mm3]
θ range for data coll. [deg]
Index ranges
Reflns. collected
Indep. reflns. [R(int)]
Observed reflns.
Data/restraints/params.
Goodness-of-fit on F2
R(F)
0.035
0.095
0.42 and Ϫ0.31
0.042
0.101
0.28 and Ϫ0.34
0.037
0.097
0.38 and Ϫ0.31
RW(F2)
(∆p)max, (∆p)min [e·A
Ϫ3
˚
]
CCDC-205108 (8a), -205109 (8b), -205110 (8c), -205111 (12),
-205112 (13), -205113 (14), and -205114 (15) contain the sup-
plementary crystallographic data for this paper. These data can be
obtained free of charge at www.ccdc.cam.ac.uk/conts/retriev-
3,3,7,7-Tetramethyl-5,5-diphenyl-4,6-dioxa-5-silanona-1,8-diyne
(10c): Reaction mixture: 2-methyl-3-butyn-2-ol (2.00 g, 23.8 mmol),
dichloromethane (100 mL), DMAP (22 mg, 0.20 mmol), triethyl-
amine (3.13 mL, 29.0 mmol), diphenyldichlorosilane (3.01 g,
ing.html [or from the Cambridge Crystallographic Data Centre, 12, 11.9 mmol). Yield 3.86 g (93%). White solid, m.p. 39 °C. 1H NMR
Union Road, Cambridge CB2 1EZ, UK; Fax: (internat.) (500 MHz, CDCl3): δ ϭ 1.55 (s, 12 H, CH3), 2.28 (s, 2 H, CH),
ϩ44Ϫ1223/336-033; E-mail: deposit@ccdc.cam.ac.uk].
7.30Ϫ7.34 (m, 6 H, CH), 7.68Ϫ7.70 (m, 4 H, CH) ppm. 13C NMR
(125 MHz, CDCl3): δ ϭ 32.7 (CH3), 68.1 (C), 70.8 (CH), 88.6 (C),
127.4 (CH), 129.8 (CH), 135.6 (C) ppm. HRMS (positive EI) calcd.
for C22H24O2Si ([M]ϩ), 348.1546; found, 348.1541 (Ϫ0.5 mmu). IR
(KBr): ν˜ ϭ 3284, 3070, 2985, 1428, 1382, 1363, 1226 cmϪ1. UV/
Vis (CH2Cl2) (logε) λmax ϭ 254 (2.81), 260 (2.88), 266 (2.92), 272
(2.81), 286 (2.20) nm. C22H24O2Si (348.52): calcd. C 75.82, H 6.94;
found C 75.42, H 6.92.
General Procedure for the Synthesis of the Terminal Diynes 10a and
10c: A solution of 2-methyl-3-butyn-2-ol in dichloromethane was
cooled to 0 °C. Then DMAP and triethylamine were added. To this
mixture the dichlorosilane was added slowly. After warming up to
room temperature the mixture was hydrolysed. The organic phase
was separated, dried and the solvent was removed. Column chro-
matography (SiO2, diethyl ether/petroleum ether, 1:2) yielded the
pure compounds.
General Procedure for the Synthesis of the Terminal Diols 11a؊c:
A solution of the respective diyne in THF was cooled to Ϫ40 °C
and n-butyllithium was added. After warming up to room tempera-
ture the ketone was added. Aqueous workup and extraction of the
aqueous phase with dichloromethane yielded after further purifi-
cation by column chromatography (SiO2, diethyl ether/petroleum
ether, 1:1) the pure diols.
3,3,5,5,7,7-Hexamethyl-4,6-dioxa-5-silanona-1,8-diyne (10a): Reac-
tion mixture: 2-methyl-3-butyn-2-ol (2.00 g, 23.8 mmol), dichloro-
methane (100 mL), DMAP (22 mg, 0.20 mmol), triethylamine
(3.13 mL, 29.0 mmol), dimethyldichlorosilane (1.54 g, 11.9 mmol).
Yield 1.67 g (63%). Colourless liquid. 1H NMR (300 MHz,
CDCl3): δ ϭ 0.28 (s, 6 H, CH3), 1.55 (s, 12 H, CH3), 2.40 (s, 2 H,
CH) ppm. 13C NMR (75 MHz, CDCl3): δ ϭ 1.7 (CH3), 32.9 (CH3), 2,12-Dihydroxy-2,5,5,7,7,9,9,12-octamethyl-6,8-dioxa-7-silatrideca-
66.8 (C), 70.7 (CH), 89.0 (C) ppm. HRMS (positive EI) calcd. for 3,10-diyne (11a): Reaction mixture: 10a (6.93 g, 31.2 mmol), THF
C12H19O2Si ([M Ϫ H]ϩ), 223.1155; found, 223.1176 (ϩ2.1 mmu).
(1 L), n-butyllithium (1.6  in hexane, 39.2 mL, 62.7 mmol), ace-
IR (film): ν˜ ϭ 3307, 2986, 2936, 1464, 1379, 1361, 1258, 1224 cmϪ1
.
tone (2.0 g, 34.4 mmol). Yield 8.50 g (80%). Colourless oil. 1H
3056
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Eur. J. Org. Chem. 2003, 3051Ϫ3059

Sterically Hindered Cyclic Diynes
FULL PAPER
Table 4. Crystal data and structural refinement for 12, 13, 14, and 15
12
13
14
15
Empirical formula
Molecular mass
Wavelength [A]
C28H41Co2O10.50Si2
719.65
0.71073
C32H36Co4O16Si2
968.51
0.71073
C60H58Co2O11Si2
1129.10
0.71073
C52H44Co4O16Si2
1216.77
0.71073
˚
Crystal system
Space group
monoclinic
P21/n
triclinic
P1
triclinic
P1
triclinic
P1
¯
¯
¯
Temp. [K]
200(2)
4
200(2)
2
200(2)
2
200(2)
1
Z
a
b
c
8.1528(1)
22.6349(2)
19.3840(3)
90
93.171(1)
90
3571.6
1.34
1.04
0.85/0.75
polyhedron
0.49 ϫ 0.21 ϫ 0.19
1.4 to 27.5
Ϫ10Յ h Յ10
Ϫ29Յ k Յ29
Ϫ24Յ l Յ25
36769
8193 (0.0387)
6469 [I Ͼ 2σ (I)]
8193/10/418
1.03
8.1680(1)
15.1054(2)
16.9358(1)
86.054(1)
89.442(1)
83.581(1)
2071.5
10.8861(2)
13.5324(2)
21.4017(4)
72.516(1)
78.186(1)
69.516(1)
2799.4
8.8530(2)
13.0117(3)
13.4693(3)
117.287(1)
97.246(1)
98.947(1)
1327.2
α
β
γ
3
˚
V [A ]
Dcalcd. [g/cm3]
1.55
1.70
1.34
0.69
1.52
1.34
Abs. coeff. µ [mmϪ1
Max./min. transm.
Crystal shape
]
0.95/0.66
polyhedron
0.31 ϫ 0.09 ϫ 0.04
1.2 to 27.5
Ϫ10Յ h Յ10
Ϫ19Յ k Յ19
Ϫ21Յ l Յ21
21671
9444 (0.0575)
5572 [I Ͼ 2σ (I)]
9444/0/499
0.96
1.00/0.93
polyhedron
0.50 ϫ 0.24 ϫ 0.17
1.0 to 25.7
Ϫ13Յ h Յ13
Ϫ16Յ k Յ16
Ϫ26Յ l Յ26
25591
10613 (0.0237)
8753 [I Ͼ 2σ(I)]
10613/0/682
1.07
0.95/0.58
polyhedron
0.46 ϫ 0.14 ϫ 0.05
1.8 to 27.5
Ϫ11Յ h Յ11
Ϫ16Յ k Յ16
Ϫ17Յ l Յ17
13726
6026 (0.0322)
4482 [I Ͼ 2σ(I)]
6026/0/338
0.97
Crystal size [mm3]
θ range for data coll. [deg]
Index ranges
Reflns. collected
Indep. reflns. [R(int)]
Observed reflns.
Data/restraints/params.
Goodness-of-fit on F2
R(F)
0.030
0.068
0.30 and Ϫ0.33
0.044
0.081
0.40 and Ϫ0.42
0.030
0.075
0.34 and Ϫ0.34
0.031
0.068
0.48 and Ϫ0.37
RW(F2)
Ϫ3
˚
(∆p)max, (∆p)min [e·A
]
NMR (300 MHz, CDCl3): δ ϭ 0.27 (s, 6 H, CH3), 1.49 (s, 12 H, (m, 4 H, CH) ppm. 13C NMR (75 MHz, CDCl3): δ ϭ 31.1 (CH3),
CH3), 1.52 (s, 12 H, CH3), 2.45 (s, 2 H, OH) ppm. 13C NMR 33.1 (CH3), 64.8 (C), 68.0 (C), 86.7 (C), 87.6 (C), 127.6 (CH), 129.9
(75 MHz, CDCl3): δ ϭ 1.8 (CH3), 31.5 (CH3), 33.0 (CH3), 65.1 (CH), 135.4 (CH), 136.5 (C). HRMS (positive FAB) calcd. for
(C), 66.9 (C), 87.2 (C), 87.2 (C) ppm. HRMS (positive FAB) calcd. C28H36NaO4Si ([M
ϩ
Na]ϩ), 487.2281; found, 487.2258
for C18H32O4SiNa ([M ϩ Na]ϩ), 363.1967; found, 363.1956 (Ϫ2.3 mmu). IR (KBr): ν˜ ϭ 3357, 3296, 2983, 2933, 1429, 1398,
(Ϫ0.4 mmu). IR (film): ν˜ ϭ 3359, 2983, 2934, 1456, 1369, 1256 1377, 1362, 1263 cmϪ1. UV/Vis (CH2Cl2) (logε) λmax ϭ 230 (3.66),
cmϪ1. C18H32O4Si (340.53): calcd. C 63.49, H 9.47; found C 63.20, 260 (2.92), 266 (2.96), 272 (2.83) nm. C28H36O4Si (464.68): calcd.
H 9.50.
C 72.37, H 7.81; found C 72.08, H 7.78.
1,11-Dihydroxy-4,4,6,6,8,8-hexamethyl-1,1,11,11-tetraphenyl- General Procedure for the Synthesis of the Cyclic Diynes 8a؊c: A
5,7-dioxa-6-silaundeca-2,9-diyne (11b): Reaction mixture: 10a solution of the diol and a solution of the respective dichlorosilane,
(6.93 g, 31.2 mmol), THF (1 L), n-butyllithium (1.6  in hexane, both in dichloromethane, were added synchronously to a solution
39.2 mL, 62.7 mmol), benzophenone (5.83 g, 32.0 mmol). Yield of triethylamine and DMPA in dichloromethane over a period of
14.3 g (78%). Colourless oil. 1H NMR (300 MHz, CDCl3): δ ϭ one hour at 0 °C. The mixture was warmed to room temperature
0.15 (s, 6 H, CH3), 1.57 (s, 12 H, CH3), 3.13 (br., OH), 7.08Ϫ7.17 and after aqueous workup and purification by column chromatog-
(m, 12 H, CH), 7.31Ϫ7.45 (m, 8 H, CH) ppm. 13C NMR (75 MHz, raphy (SiO2, diethyl ether/petroleum ether, 5:1) the cyclic diynes
CDCl3): δ ϭ 1.4 (CH3), 32.7 (CH3), 67.1 (C), 74.2 (C), 85.2 (C), were obtained.
92.1 (C), 126.1 (CH), 127.5 (CH), 128.1 (CH), 145.0 (C) ppm.
2,2,4,4,7,7,9,9,11,11,14,14-Dodecamethyl-1,3,8,10-tetraoxa-
2,9-disilacyclotetradeca-5,12-diyne (8a): Reaction mixture: 11a
(8.10 g, 23.8 mmol) in dichloromethane (50 mL), dimethyldichloro-
silane (3.07 g, 23.8 mmol) in dichloromethane (50 mL), DMAP
HRMS (positive EI) calcd. for C38H40O4Si ([M]ϩ), 588.2768;
found, 588.2732 (ϩ3.6 mmu). IR (KBr): ν˜ ϭ 3060, 2983, 1658,
1598, 1490, 1448, 1318, 1279, 1244 cmϪ1. UV/Vis (CH2Cl2) (logε)
λmax ϭ 254 (4.38), 332 (2.60) nm.
(42.7 mg, 0.35 mmol) and triethylamine (6.22 mL, 57.9 mmol) in
2,12-Dihydroxy-2,5,5,9,9,12-hexamethyl-7,7-diphenyl-6,8- dichloromethane (150 mL). Yield 4.72 g (50%). White solid, m.p.
dioxa-7-silatrideca-3,10-diyne (11c): Reaction mixture: 10c (10.9 g, 71 °C. 1H NMR (300 MHz, CDCl3): δ ϭ 0.23 (s, 12 H, CH3), 1.53
31.2 mmol), THF (1 L), n-butyllithium (1.6  in hexane, 39.2 mL, (s, 24 H, CH3) ppm. 13C NMR (75 MHz, CDCl3): δ ϭ 2.0 (CH3),
62.7 mmol), acetone (2.0 g). Yield 11.5 g (79%). White solid, m.p. 32.6 (CH3), 67.1 (C), 87.0 (C) ppm. HRMS (positive EI) calcd. for
75 °C. 1H NMR (300 MHz, CDCl3): δ ϭ 1.30 (s, 12 H, CH3), 1.59 C20H36O4Si2 ([M]ϩ), 396.2152; found, 396.2169 (ϩ1.7 mmu). IR
(s, 12 H, CH3), 1.80 (br., OH), 7.34Ϫ7.40 (m, 6 H, CH), 7.71Ϫ7.74 (film): ν˜ ϭ 3310, 2984, 2935, 2868, 2362, 1908, 1729, 1459, 1407,
Eur. J. Org. Chem. 2003, 3051Ϫ3059
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C. Schaefer, R. Gleiter, F. Rominger
1367, 1257 cmϪ1. UV/Vis (CH2Cl2) (logε) λmax ϭ 252 (2.56) nm. (4.09), 406 (3.74) nm. C32H36Co4O16Si2 (968.53): calcd. C 39.68, H
FULL PAPER
C20H36O4Si2 (396.67): calcd. C 60.56, H 9.15. found: calcd. C
60.46, H 9.10.
3.75, found C 39.78, H 3.73.
(µ:µ-2,2,4,4,14,14-Hexamethyl-7,7,9,9,11,11-hexaphenyl-1,3,8,10-
tetraoxa-2,9-disilacyclotetradeca-5,12-diyne)mono(hexacarbonyl-
dicobalt) (14): Reaction mixture: 8b (500 mg, 0.650 mmol),
Co2(CO)8 (500 mg, 6.50 mmol), dichloromethane (40 mL). Yield
144 mg (25%). Brownish red solid, m.p. 124 °C (dec.). 1H NMR
(300 MHz, CDCl3): δ ϭ 0.23 (s, 6 H, CH3), 1.55 (s, 6 H, CH3),
2.23 (s, 6 H, CH3), 6.96 (m, 14 H, CH), 7.26 (m, 10 H, CH), 7.53
(m, 4 H, CH) ppm. 13C NMR (75 MHz, CDCl3): δ ϭ 2.0 (CH3),
32.9 (CH3), 34.4 (CH3), 67.0 (C), 77.4 (C), 86.5 (C), 88.5 (C), 92.9
(C), 109.9 (C), 111.3 (C), 126.5 (CH), 127.0 (CH), 127.0 (CH),
127.2 (CH), 127.3 (CH), 127.6 (CH), 129.2 (CH), 130.6 (CH), 133.5
(C), 136.3 (CH) 145.3 (C), 146.1 (C), 199.9 (CO) ppm. HRMS
(positive FAB) calcd. for C50H48Co2O4Si2 ([Mϩ Ϫ 6 CO]) 886.1755;
found, 886.1777 (ϩ2.2 mmu). IR (KBr): ν˜ ϭ 2087, 2049, 2020,
1627, 1448, 1258 cmϪ1. UV/Vis (CH2Cl2) (logε) λmax ϭ 264 (4.17),
318 (3.16), 348 (3.47), 418 (2.77), 426 (2.77), 432 (2.76) nm.
2,2,4,4,14,14-Hexamethyl-7,7,9,9,11,11-hexaphenyl-1,3,8,10-tetra-
oxa-2,9-disilacyclotetradeca-5,12-diyne (8b): Reaction mixture: 11b
(14.0 g, 23.8 mmol) in dichloromethane (50 mL), diphenyldichloro-
silane (6.03 g, 23.8 mmol) in dichloromethane (50 mL), DMAP
(42.7 mg, 0.35 mmol), and triethylamine (6.22 mL, 57.9 mmol) in
dichloromethane (150 mL). Yield 1.46 g (8%). White solid, m.p. 139
1
°C. H NMR (300 MHz, CDCl3): δ ϭ Ϫ0.02 (s, 6 H, CH3), 1.41
(s, 12 H, CH3), 7.03Ϫ7.11, 7.17Ϫ7.25, 7.39Ϫ7.42 (m, 30 H, CH)
ppm. 13C NMR (75 MHz, CDCl3): δ ϭ 1.5 (CH3), 32.4 (CH3), 67.1
(C), 76.8 (C), 84.5 (C), 92.8 (C), 126.8 (CH), 126.9 (CH), 127.0
(CH), 127.5 (CH), 129.0 (CH), 134.6 (C), 135.2 (CH), 145.6 (C)
ppm. MS (positive FAB): m/z ϭ 691 ([M Ϫ Ph]ϩ). IR (KBr): ν˜ ϭ
3059, 2980, 1489, 1448, 1430, 1378, 1245 cmϪ1. UV/Vis (CH2Cl2)
(logε) λmax ϭ 254 (3.63), 286 (2.71) nm. C50H48O4Si2 (769.10):
calcd. C 78.08, H 6.29. found C 77.83, H, 6.27.
(µ:µ-4,4,7,7,11,11,14,14-Octamethyl-2,2,9,9-tetraphenyl-1,3,8,10-
tetraoxa-2,9-disilacyclotetradeca-5,12-diyne)bis(hexacarbonyl-
dicobalt) (15): Reaction mixture: 8c (94 mg, 0.146 mmol), Co2(CO)8
(499 mg, 1.46 mmol), dichloromethane (10 mL). Yield 140 mg
(79%). Dark red solid, m.p. 110 °C (dec.). 1H NMR (300 MHz,
CDCl3): δ ϭ 1.62 (s, 24 H, CH3), 7.14Ϫ31, 7.65 (m, 20 H, CH)
ppm. 13C NMR (75 MHz, CDCl3): δ ϭ 34.1 (CH3), 78.1 (C), 127.5
(CH), 130.3 (CH), 136.0 (C), 136.7 (CH) ppm. MS (positive FD):
m/z ϭ 1216 ([M]ϩ). IR (KBr): ν˜ ϭ 2990, 2088, 2051, 2020, 1632,
1460, 1430, 1380, 1221 cmϪ1. UV/Vis (CH2Cl2) (logε) λmax ϭ 260
(4.57), 324 (4.02), 350 (4.11), 422 (3.57) nm.
4,4,7,7,11,11,14,14-Octamethyl-2,2,9,9-tetraphenyl-1,3,8,10-
tetraoxa-2,9-disilacyclotetradeca-5,12-diyne (8c): Reaction mixture:
11c (11.1 g, 23.8 mmol) in dichloromethane (50 mL), diphenyldi-
chlorosilane (6.03 g, 23.8 mmol) in dichloromethane (50 mL), DMAP
(42.7 mg, 0.35 mmol) and triethylamine (6.22 mL, 57.9 mmol) in
dichloromethane (150 mL). Yield 3.99 g (26%). White solid, m.p.
186 °C. 1H NMR (300 MHz, CDCl3): δ ϭ 1.48 (s, 24 H, CH3),
7.27Ϫ7.38 (m, 6 H, CH), 7.68Ϫ7.71 (m, 4 H, CH) ppm. 13C NMR
(75 MHz, CDCl3): δ ϭ 32.3 (CH3), 68.0 (C), 86.4 (C), 127.1 (CH),
129.2 (CH), 134.8 (CH), 136.7 (C) ppm. HRMS (positive EI) calcd.
for C40H44O4Si2 ([M]ϩ), 644.2778; found, 644.2768 (Ϫ1.0 mmu).
IR (KBr): ν˜ ϭ 3068, 2985, 1628, 1429, 1378, 1361, 1271 cmϪ1. UV/
Vis (CH2Cl2) (logε) λmax ϭ 256 (3.00), 262 (3.11), 266 (3.13), 272
(2.96) nm. C40H44O4Si2 (644.96): calcd. C 74.49, H 6.88, found C
74.31, H 7.14.
Acknowledgments
We thank the Deutsche Forschungsgemeinschaft (SFB 623), the
Fonds der Chemischen Industrie and the BASF Aktiengesellschaft,
Ludwigshafen, for financial support.
General Procedure for the Synthesis of the Co2(CO)6 Complexed
Diynes: To the solution of the diyne in dichloromethane dico-
baltoctacarbonyl was added and stirred overnight. The solvent was
evaporated and the residue purified by column chromatography on
Al2O3/6%H2O with petroleum ether as mobile phase.
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E. Kloster-Jensen, G. A. Eliassen, Angew. Chem. 1985, 97,
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(12): Reaction mixture: 8a (100 mg, 0.252 mmol), Co2(CO)8
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(Ed.: P. J. Stang, F. Diederich), VCH, Weinheim, 1995, p.
(30%). Dark red solid, m.p. 71 °C. H NMR (300 MHz, CDCl3):
321Ϫ351.
δ ϭ 0.21 (s, 12 H, CH3), 1.49 (s, 12 H, CH3), 1.75 (s, 12 H, CH3)
ppm. 13C NMR (75 MHz, CDCl3): δ ϭ 2.0 (CH3), 32.8 (CH3), 33.3
(CH3), 66.8 (C), 79.3 (C), 87.5 (C), 109.3 (C), 208.8 (CO) ppm. MS
(positive FD): m/z ϭ 682 ([M]ϩ). IR (KBr): ν˜ ϭ 2985, 2088, 2048,
2020, 1628, 1459, 1378, 1360, 1258 cmϪ1. UV/Vis (CH2Cl2) (logε)
λmax ϭ 254 (4.27), 312 (3.78), 350 (3.80) nm. C26H36Co2O10Si2
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(µ:µ-2,2,4,4,7,7,9,9,11,11,14,14-Dodecamethyl-1,3,8,10-tetra-
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dicobalt) (13): Reaction mixture: 8a (100 mg, 0.252 mmol),
Co2(CO)8 (690 mg, 2.016 mmol), dichloromethane (10 mL). Yield
110 mg (45%). Dark red solid, m.p. 60 °C (dec.). 1H NMR
(300 MHz, CDCl3): δ ϭ 0.27 (s, 12 H, CH3), 1.73 (s, 24 H, CH3)
ppm. 13C NMR (75 MHz, CDCl3): δ ϭ 3.5 (CH3), 33.1 (CH3), 76.2
(C), 108.4 (C), 200.5 (CO) ppm. MS (positive FD): m/z ϭ 968
([M]ϩ). IR (KBr): ν˜ ϭ 2934, 2088, 2050, 2017, 1632, 1378, 1261
cmϪ1. UV/Vis (CH2Cl2) (logε) λmax ϭ 252 (4.62), 316 (4.05), 350
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 2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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Sterically Hindered Cyclic Diynes
FULL PAPER
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Eur. J. Org. Chem. 2003, 3051Ϫ3059
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 2003 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
3059