Cyclopentadienylcobalt-mediated intermolecular cycloaddition of ,α ω-diynes to (Cyclo)alkenes: Synthesis of linearly fused fligocycles and extension to enantiomerically pure (6a R,10a R)-dihydroanthracyclinones

Article abstract of DOI:10.1055/s-0029-1220007

The generality of the [CpCoL₂]-mediated [2+2+2] cycloaddition of , α ω-diynes to (cyclo)alkenes has been extended to include linear oligocycles as models for the one-step, A + D→ ABCD construction of optically pure, novel 6,10-dihydroanthracyclinones. Georg Thieme Verlag Stuttgart - New York.

Full text of DOI:10.1055/s-0029-1220007

PAPER
2179
Cyclopentadienylcobalt-Mediated Intermolecular Cycloaddition of
a,w-Diynes to (Cyclo)alkenes: Synthesis of Linearly Fused Oligocycles and
Extension to Enantiomerically Pure (6aR,10aR)-Dihydroanthracyclinones
Cobalt-Mediate
d
o
Cycloadditio
r
ns inne Aubert,a Vincent Gandon,b Sangdon Han,c Barry M. Johnson,c Max Malacria,a Sten Schömenauer,c
K. Peter C. Vollhardt,*c Glenn D. Whitenerc
a
UPMC Université Paris 06, Institut Parisien de Chimie Moléculaire (UMR CNRS 7201), 4 place Jussieu, C. 229, 75005 Paris, France
Université Paris-Sud, UMR CNRS 8182, 91405 Orsay, France
Department of Chemistry, University of California at Berkeley, Berkeley, California 94720-1460, USA
Fax +1(510)6435208; E-mail: kpcv@berkeley.edu
b
c
Received 26 March 2010
Dedicated to Professor Rolf Huisgen, whose introductory organic ‘Experimentalvorlesung’ doomed the corresponding author’s ambitions
as a rock ’n roll musician, on the occasion of his 90th birthday
was, in addition, secured by comparison with the data for
Abstract: The generality of the [CpCoL2]-mediated [2+2+2] cy-
analogous complexes derived by cocyclization of nor-
cloaddition of a,w-diynes to (cyclo)alkenes has been extended to in-
bornene with diphenylacetylene.9 While some diastereo-
clude linear oligocycles as models for the one-step, A + D → ABCD
selectivity for the syn cycloadducts was discerned (the
metal emerging on the same side as the newly fused ring),
frequently mixtures of both isomers were observed, the
result of nearly isoenergetic pathways for exo versus endo
complexation of the alkene in the intermediate cobaltacy-
clopentadiene and its subsequent insertion, as expected on
the basis of DFT computational work.4a,10 Most relevant
to the stated aims in Scheme 1, the functionalized cyclo-
hexenes in the last two entries to Table 1 failed in this
chemistry. Switching from CpCo(CO)2 to Cp-
Co(CH2=CH2)2 as a cobalt source, a strategy used to great
advantage for other systems,3,4 was unsuccessful, al-
though cyclohexenone furnished some 15. The major
identifiable side product in all of these reactions was 1,4-
bis(5,6,7,8-tetrahydronaphthalen-2-yl)butane, the alkyne
cyclotrimerization product of 2.1k
construction of optically pure, novel 6,10-dihydroanthracyclinones.
Key words: alkenes, alkynes, cycloadditions, polycycles, transi-
tion metals
Transition-metal-enabled [2+2+2] cycloadditions of un-
saturated functionalities have emerged as a powerful strat-
egy for ring construction in organic synthesis.1 One of its
topological variants is the intermolecular cocyclization of
a,w-diynes with (cyclo)alkenes to give fused cyclohexa-
dienes.1b,d,g,2 While much progress has been made on this
approach, the published work indicates limitations with
respect to the choice of diyne, alkene, functionality, selec-
tivity toward the cyclic diene product, and lability of the
latter to undergo rearrangements and/or aromatization.2
We have used CpCoL2 (L = CO or CH2=CH2) to effect
cooligomerizations of alkynes with alkenes,3 but the
above option was employed only rarely and always within
the context of a specific substrate.4 This metal system has
the advantage of providing the products in complexed,
hence protected, form, from which the ligands are readily
obtained by mild oxidative decomplexation, and appears
to be the hitherto most versatile in functional scope. We
report a comprehensive study of such cyclizations, which
had as their ultimate goal the regioselective assembly of
enantiopure antitumor daunomycinone (1) derivatives5
according to Scheme 1.6–8
O
O
R1
OH
B
O
O
C
O
OP
OH
D
A
OP
OH
R2
OH
OMe
O
O
CpCo
OMe
1
O
R1
R2
OP
+
Table 1 depicts the simplest versions of the key reaction
shown in Scheme 1, featuring octa-1,7-diyne (2; Figure 1)
and various (cyclo)alkenes. The stereochemistry of the
metal relative to the newly generated ring junction (syn or
anti) was ascertained by 1H NMR spectroscopy, including
2D techniques, as described at length previously.1k,3,4 The
relative disposition of the norbornane bridges in 9 and 10
OMe
OP
O
P = protecting group
Scheme 1
O
TMS
TMS
TMS
TMS
TMS
TMS
SYNTHESIS 2010, No. 13, pp 2179–2200
x
x.
x
x
.
2
0
1
0
CpCo
18
Advanced online publication: 18.05.2010
DOI: 10.1055/s-0029-1220007; Art ID: C01210SS
2
17
28
© Georg Thieme Verlag Stuttgart · New York
Figure 1 Octa-1,7-diynes 2, 17, and 28, and cyclobutadiene 18

2180
C. Aubert et al.
PAPER
Table 1 Cocyclization of Octa-1,7-diyne (2) with Various Alkenesa
Table 1 Cocyclization of Octa-1,7-diyne (2) with Various Alkenesa
(continued)
Alkene
Products
Yield
(%)
Alkene
Products
Yield
(%)
H
H
a CpCo(CO)2 (1.0 equiv), alkene (5 equiv), boiling m-xylene, hn, 25–
72 h.
H
28b
20
b Mixture from which 3 was selectively crystallized (MeOH).
c Mixture from which 9 was selectively crystallized (MeOH).
d Known compounds: 13, see ref. 28; 14, see ref. 29.
e Only product using CpCo(CH2=CH2)2, Et2O, r.t., 6 h.
CpCo
CpCo
H
H
2:1
3
4
To mitigate the undesired selfreactivity of 2, the corre-
sponding 1,8-bis(trimethylsilyl) derivative 17 was scruti-
nized, albeit with some trepidation, as previous attempts
at employing this diyne as a cocyclization partner had fur-
nished the corresponding cyclobutadiene (18; Figure 1)
and cyclopentadienone cobalt complexes, possibly the re-
sult of excessive steric hindrance.4d,11 Gratifyingly, and
after extensive optimization procedures toward 19, the re-
sults summarized in Table 2 were collected. The desired
cycloadducts formed as only one diastereomer in moder-
ate to good yields (with the exception of 27), and the mass
balances were good to excellent, the bulk of the side prod-
ucts constituting 18. Compared to the dominant stere-
ochemistry at cobalt in Table 1, one notes that it is largely
inverted in Table 2. This is illustrated by example 19, for
which the tertiary hydrogens give rise to an 1H NMR sig-
nal at d = 1.87, in contrast to the corresponding hydrogens
in 5 (d = 0.68), but almost identical to those in 54 (vide in-
fra; d = 1.91), the constitution of which rests on an X-ray
structural analysis. Inspection of the calculated structures
of the relevant transition states to alkene insertion into the
Co–C bond of the cobaltacyclopentadiene unit4a,10 reveals
near eclipsing of the substituent a to Co (in the present
case TMS) with the exo substituent on the adjacent (in-
serting) alkene carbon, thus favoring an endo pathway. As
expected, the stereochemistry of the oct-4-ene substrates
is retained in the respective products 11 and 12. Encour-
aging for further synthetic applications is the successful
generation of 22–26 and the considerably reduced sensi-
tivity of all of the silylated complexes to manipulation in
air.
CpCo
CpCo
H
H
5
6
36
H
H
O
O
H
O
O
O
O
O
35
CpCo
CpCo
CpCo
H
H
H
H
O
O
3:4
1:1
8
7
29c
23
CpCo
CpCo
H
H
H
9
10
H
H
11
18
CpCo
H
12
13
O
O
OH
O
37d
O
TMS
H
OH
O
TMS
H
OH
28
1.0:1.2
+
14
66%
OH
CpCo
O
CpCo
O
H
H
H
TMS
TMS
10e
29
1:1
30
CpCo
CpCo
H
O
TMS
H
O
TMS
H
O
15
28
+
O
73%
H
O
O
CpCo
CpCo
H
H
1
TMS
O
TMS
32
1:1
31
H
16
Scheme 2 Reagents and conditions: CpCo(CO)2 (1.1 equiv), alkene
(10 equiv), boiling Et2O, hn, 60 h.
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Cobalt-Mediated Cycloadditions
2181
Table 2 Cocyclizations of 1,8-Bis(trimethylsilyl)octa-1,7-diyne
(17) with Various Alkenesa
Table 2 Cocyclizations of 1,8-Bis(trimethylsilyl)octa-1,7-diyne
(17) with Various Alkenesa (continued)
Alkene
Products
Yield (%) 18 (%)
Alkene
Products
Yield (%) 18 (%)
TMS
H
TMS
O
O
H
O
O
4c
81
55
21
19
36
CpCo
H
CpCo
H
TMS
TMS
19
27
TMS
H
a CpCo(CO)2 (1.1 equiv), alkene (10 equiv), boiling Et2O, hn, 52 h.
b The stereochemistry at the hydroxy carbon is tentative and based on
the assumption that in the intermediate cobaltacyclopentadiene cyclo-
hexenol complex, the OH group is pointing away from the metal.
c In addition to 26 (2%).
CpCo
H
TMS
20
In this vein, a brief excursion was made into testing the
potential regioselectivity of an unsymmetrical diyne,
namely the oxo derivative 28 (Figure 1), as a model for
addressing the (more intricate) regiochemical problem
embedded in Scheme 1 on route to 1. This substrate could
be synthesized readily by chromic acid oxidation of the
known12 alcohol precursor. Scheme 2 reveals that the
presence of the symmetry breaking oxo group in 28 is in-
consequential to the regio- (and stereo-) outcome of the
cyclization, equimolar mixtures of both isomers being
created, although in quite good yields. The regiochemical
assignments of molecules 29 and 30 are tentative and are
based on the observation of hindered rotation of the more
deshielded TMS group in 29. At room temperature, this
phenomenon manifests itself in a severely broadened res-
onance at d = 0.53, sharpened on heating and decoalesc-
ing on cooling to three singlets (d = 0.80, 0.53, and 0.27).
This signal was assigned to the silyl group b to the carbo-
nyl function, the anisotropy of which should cause a rela-
tively larger chemical shift, a supposition that is supported
by the NMR spectra of a number of similar structures
(vide infra). Molecular modeling (Chem 3D, MM2) indi-
cates slightly greater crowding of this substituent in 29,
compared to 30, leading to the respective structural
choices. The presence of a similarly uniquely encumbered
TMS moiety in 31 and related tentative arguments
prompted the suggested connectivities of 31 and 32. Hin-
dered TMS-rotation in other CpCo-mediated cyclization
products has been reported (and quantified) previously by
us.13
TMS
H
17
55
CpCo
H
TMS
21
TMS
H
OH
CpCo
TMS
OH
22
82
10
(ratio 4:3)
TMS
H
OH
CpCo
TMS
23
TMS
H
OH
OH
O
OH
42
39
44
50
CpCo
CpCo
CpCo
H
TMS
24
TMS OH
H
31b
H
TMS
25
Undaunted by the unsolved issue of regioselectivity and
encouraged by the reasonable yields, attention turned to
cyclizations more directly addressing the topological fea-
tures of Scheme 1 and involving the diynes shown in
Figure 2. Of these diynes, 3314 and 3415 were known, and
35 and 36 were accessed in an analogous manner from
benzenedicarboxaldehyde by alkynyl Grignard addition
(sequential for 36), followed by Cr(VI) oxidation. A se-
lective sequence (Scheme 3)16 was employed in the con-
struction of 37 and 38, starting from 3-hydroxyphthalide
(40), via monoalkynylated 41, its reduction to 42 (mixture
of diastereomers and the hydroxy aldehyde isomer), and
TMS
H
O
40
H
TMS
26
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2182
C. Aubert et al.
PAPER
renewed one-pot alkynylation-oxidation. Meso-diol 39 is stants around the A ring (see experimental section). Even-
an intermediate on route to 34, and was separated from its tually, two crystal structure analyses of analogues
(minor; ratio 1.7:1) diastereomer by fractional crystalliza- confirmed these assignments for the entire series (vide in-
tion.17
fra).19 The structure of 54 was also ascertained by X-ray
analysis, providing further confirmation of the configura-
tion of the CpCo unit in all related complexes.19
O
HO
R1
R2
TMS
TMS
As observed for 29 and 31 (Scheme 2), several of the
products exhibited rotational encumbrance of (at least
one) silyl group rotation on the NMR time scale, already
visible at ambient temperature by either line broadening
or decoalescence of the corresponding signal. The first
example is 45 (broadened signal at r.t.; three singlets at
–70 °C), for which VT NMR line shape analysis provided
activation parameters DHπ = 8.42 ( 0.04) kcal mol–1 and
DSπ = –11.0 ( 0.2) cal mol–1 K–1, comparable to those of
previously scrutinized systems.13 In the unsymmetrical
46, only one TMS signal is broadened at 20 °C, assumed
to be the one proximal to the benzoate function. The same
TMS group in 48 (and all of its congeners, e.g., 50, 52,
etc., vide infra) gives rise to three singlets at this temper-
ature in both its 1H and 13C NMR spectra, evidently the re-
sult of increased encumbrance by the sterically rigid A
ring. Relaxing this ring by quantitative conversion to the
acetal 55 (Figure 3; CH2Cl2, MeOH) was inconsequential
in this respect and served to illustrate the potential for
functional group manipulations. The stereochemical as-
signment at the acetal carbon is tentative and predicated
an attack by MeOH from the less hindered side of the mol-
ecule.
O
HO
33 R1 = R2 = H
39
34 R1 = R2 = TMS
35 R1 = R2 = SiMe2(CMe2CHMe2)
36 R1 = TMS, R2 = SiMe2(CMe2CHMe2)
37 R1 = TMS, R2 = SiMe2Et
38 R1 = TMS, R2 = TES
Figure 2 Diynes 33–39
SiMe3
1. ClMgC CSiMe3 (2 equiv),
THF, 0 °C
2. MeOH, HCl
OH
O
DIBAL-H,
toluene, −78 °C
O
O
O
40
41
SiMe3
1. ClMgC CR (2 equiv),
THF, 20 °C
2. CrO3, H2SO4,
H2O, acetone
O
37 R = SiMe2Et
38 R = TES
O
TMS
H
O
OH
TMS
TMS
OR
42
Me
Scheme 3
OMe
H
O
TMS
MeO
O
CpCo
O
The results of the cocycloadditions of these building
blocks with various cyclohexenes are summarized in
Table 3. In addition to the desired metallated dihydroan-
thraquinones, most runs also generated complexed cy-
clobutadienes and cyclopentadienones derived solely
from the diyne substrate (see experimental section). Their
proportion increased with the steric bulk of the diyne silyl
groups or alkene component. Indeed, in attempted addi-
tions of 35 or 36 to cyclohexene or prop-2-en-1-ol, respec-
tively, these were the only products isolated. In
consonance with the results in Table 1, reaction of 33 was
unselective and relatively low-yielding, compared to the
corresponding transformations of 34 or 39. Significantly,
employment of the enantiomerically pure 47a, which con-
tains all the structural and stereochemical information em-
bedded in the A ring,18 furnished the corresponding
(6aR,10aR)-dihydroanthracyclinone frames enantiospe-
cifically. Disappointingly, however, attempts to exert re-
giocontrol, by means of two different silyl groups on the
diyne, for example, using 37 or 38, failed, the respective
pairs of isomers 49/50 and 51/52 emerging in equimolar
ratios. Nevertheless, 48–52 materialized with exquisite
stereocontrol, established for 48 initially via extensive 2D
NMR experiments and analysis of H–H coupling con-
56
55 R = SiMe2(CMe2CHMe2)
Figure 3 Acetal 55 and diyne 56
Table 3 Cocyclizations of 33–39 with Various Cyclohexenesa
Substrates
Product
Yield (%)
O
H
H
O
CpCo
43
O
19b
H
H
33 +
O
CpCo
44
1:1
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PAPER
Cobalt-Mediated Cycloadditions
2183
Table 3 Cocyclizations of 33–39 with Various Cyclohexenesa
(continued)
Table 3 Cocyclizations of 33–39 with Various Cyclohexenesa
(continued)
Substrates
Product
Yield (%)
Substrates
Product
Yield (%)
TMS
H
TMS
H
O
OH
59c
34 +
H
H
TMS
TMS
O
OH
CpCo
CpCo
45
53
71c
TMS
H
O
TMS
H
OH
39 +
34 +
31c,d
H
H
OBz
TMS
O
CpCo
TMS
OH
CpCo
OBz
46
54
TMS
H
O
1:6
34
OR
+
a CpCo(CO)2 (1.3 equiv), alkene (10 equiv), solvent, r.t., hn, 2–3 days.
In the case of the valuable 47a, most of the excess reagent could be
OR
44e
recovered on chromatography.
H
O
TMS
b THF; inseparable mixture.
O
CpCo
O
c Benzene.
47a
48 R = SiMe2(CMe2CHMe2)
d Stereochemistry at the benzoyloxycarbon tentative. See footnote b
in Table 2.
TMS
H
O
e Toluene.
f Boiling Et2O.
OR
H
O
The phenomenon of hindered ethyl(dimethyl)silyl rota-
tion in 49 is particularly striking, as the different rotamers
are, in fact, diastereomers. Indeed, at 20 °C, a complex set
of resonances indicative of the presence of three isomers
was visible by NMR spectroscopy. Specifically, the well
separated signal due to the hydrogen next to the enol ether
oxygen appeared as three doublets of doublets at d = 4.82,
4.79, and 4.76 (J = ~7, 4 Hz) in the ratio 1:2:2, reflecting
the relative distribution of these rotamers. All these mul-
tiple signals (1H and 13C) coalesced to that of a single spe-
cies at 100 °C. In contrast, the ‘frozen’, symmetrical TES
substituent in 51 engendered simply three different sets of
peaks for the ethyl groups.
SiMe2Et
O
CpCo
37
+
OR
49 R = SiMe2(CMe2CHMe2)
16f
SiMe2Et
H
O
OR
O
47a
H
O
TMS
O
CpCo
50 R = SiMe2(CMe2CHMe2)
1:1
TMS
H
O
In a last set of experiments, the remaining missing compo-
nent of Scheme 1, the 4-methoxy appendage, was in-
stalled by way of diyne 56 (Figure 3), prepared in a
manner identical to 34 from 3-methoxyphthalaldehyde.20
The outcome of its cocyclizations is assembled in Table 4.
Notably, but perhaps not surprisingly in light of the results
obtained with 28, 37, and 38, the desymmetrizing meth-
oxy group in 56 did not influence the regioselectivity of
the cycloaddition to unsymmetrical cyclohexenes, in all
cases (nearly) equimolar mixtures being formed, although
again with remarkable stereoselectivity. That the pairs 58/
59 and 60/61 are indeed regio- and not stereoisomers was
surmised by the near identity of the spectral data of the re-
spective components in each pair, in addition to the like-
ness of the relevant spectral components with those of 25
and 46. Similar arguments apply to the pair 62/63. To ce-
OR
H
O
TES
O
CpCo
38
+
OR
51 R = SiMe2(CMe2CHMe2)
18f
TES
O
H
OR
O
47a
H
O
TMS
O
CpCo
52 R = SiMe2(CMe2CHMe2)
1:1
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2184
C. Aubert et al.
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Table 4 Cocyclizations of 56 with Various Cyclohexenesa
(continued)
ment them, a deliberate effort was made to obtain crystals
of suitable derivatives amenable for X-ray crystal analy-
sis. Such emerged by way of 47b and its cyclization to iso-
mers 64 and 65, which, on treatment with TBAF furnished
the crystalline alcohols 66 and 67 (Figure 4), respectively,
the structures of which could be determined unambigu-
ously.19 This circuitous route was necessitated by the in-
ertness of 47a, 62, and 63 to deprotection, using a variety
of fluoride sources. Therefore, 47b had to be made by
modification of the route to 47a from 68,18 as portrayed in
Scheme 4.
Cyclohexene
Products
Yield (%)
TMS
H
O
OR
H
O
TMS
OMe
O
CpCo
OR
62 R = SiMe2(CMe2CHMe2)
20
Table 4 Cocyclizations of 56 with Various Cyclohexenesa
TMS
H
OMe
O
O
OR
47a
Cyclohexene
Products
Yield (%)
H
O
TMS
O
TMS
H
O
CpCo
63 R = SiMe2(CMe2CHMe2)
43
1:1
H
TMS
OMe
O
CpCo
TMS
H
O
OTMS
57
OH
TMS
H
O
H
O
TMS
OMe
OMe
O
CpCo
OTMS
64
H
22
TMS
OMe
O
CpCo
TMS
H
O
O
OTMS
58
47b
56b
TMS
H
O
H
O
TMS
O
OH
CpCo
65
1:1
H
OH
TMS
OMe
O
CpCo
59
5:6
a CpCo(CO)2 (1.1 equiv), alkene (10 equiv), boiling Et2O, hn, 1–3 d.
b Stereochemistry at the hydroxycarbon tentative. See footnote b in
Table 2.
c Stereochemistry at the benzoyloxycarbon tentative. See footnote d
in Table 3.
OBz
TMS
H
O
1. Et3N, TMSCl, 95%
2. Zn (18 equiv), TMEDA,
TiCl4 (8 equiv), CH2Br2
H
TMS
OMe
O
CpCo
60
OH
(9 equiv), 54%
OTMS
O
O
3. BuLi (2.2 equiv), 55%
C6H5
39c
O
TMS
H
O
O
O
OBz
68
47b
Scheme 4
H
OBz
TMS
OMe
O
CpCo
Again, with the exception of 57, all compounds in Table 4
and Figure 4 exhibited NMR data showing restricted rota-
tion of one TMS group at room temperature (three sin-
glets), assigned to be located proximal to the A ring
oxygen substituent.
61
4:5
To demonstrate further synthetic utility of the complexes
described so far and to further corroborate the structural
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Cobalt-Mediated Cycloadditions
2185
matic tetrahydrotetracenediols.22 In this context, diene 73
was found to be remarkably resilient to aromatization.
Mild acid left it intact, but dilute base caused a color
change from yellow to red and eventual decomposition,
indicative of the occurrence of redox processes22b and/or
the generation of anions.23 Treatment with excess NaH
gave a red solution, which gradually turned green and
gave rise to NMR spectra consistent with the presence of
monoanion 78 (Figure 5). Attempted oxidation of 73 with
MCPBA (3 equiv) in benzene furnished the monooxacy-
clopropane 79 (62%; stereochemistry surmised on mech-
anistic grounds), inert to further oxacyclopropanation.
Other oxidizing agents (CAN, MnO2, O2) left 73 (and 76/
77) untouched. It is likely that the reluctance to aromatize
the bissilylated cyclohexadiene moiety is due to the ex-
pected extreme buttressing expected on its planariza-
tion.24 Consistent with this notion, exposure of complex
+
45 to BnNMe3 F– in THF (50 °C, 16 h) led to 44 (Table 3;
13%) and the known aromatic quinone 80 (65%).25
Finally, the carbonyls in 45 may be subject to further ste-
reoselective synthetic tinkering, as NaBH4 (13 equiv,
CH2Cl2, EtOH, r.t., 15 h) produced 81, a larger excess of
NaBH4 (40 equiv) 53 (Table 3).
Table 5 Oxidative Demetallation of CpCo(cyclohexadiene)
Complexesa
Complex
Free Diene
Yield (%)
17
H
3b
H
H
69
Figure 4 X-ray crystal structures of 66 and 67
O
assignments, a representative sample of them was oxida-
tively demetallated, in most cases using copper(II)
(Table 5). Monitoring these reactions by 1H NMR showed
high-yielding conversions, but isolated yields suffered ei-
ther from the sensitivity of the products or the small scale
of the experiments. It should be noted that all of these and
other ligands reported in this paper were unknown. The
stereoconvergent production of 69–71 from the pairs 5/6,
7/8, and 9/10, respectively, confirmed the stereochemical
assignments of the precursors as diverging only with re-
spect to the disposition of the CpCo-unit. Conversely, 53,
54, 60, and 61 each furnished a distinct respective isomer
of ligand. All of the TMS containing products exhibited
sharp singlets for this substituent, revealing free rotation
on the NMR time scale. Interestingly, 53 underwent de-
metallation by simple dissolution in MeOH, conditions
under which 54 (and 45) are inert.
O
7 + 8 (3:4)
50c
H
H
O
70
71
9 + 10 (1:1)
54
H
TMS
H
80
45
91d
H
TMS
72
TMS
H
O
Several other exploratory reactions were performed, fo-
cusing primarily on 73 and its complex 45 as simplified
representatives of the (6a,10a)-dihydroanthracyclinone
core embedded in the examples in Table 4. Various tauto-
meric forms of this array have been implicated in the bio-
logical activity of the actual antitumor drugs.21 As such,
they constitute bisenone forms of the corresponding aro-
74
H
TMS
O
73
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2186
C. Aubert et al.
PAPER
+TMS
O−Na
O
O
TMS
H
Table 5 Oxidative Demetallation of CpCo(cyclohexadiene) Com-
plexesa (continued)
O
Complex
Free Diene
Yield (%)
52e
H
H
TMS
H
OH
TMS
TMS
O
78
O
79
TMS
H
OH
53
H
TMS
OH
74
H
TMS
O
O
CpCo
TMS
H
OH
81
80
54
46f
Figure 5 Compounds 78–81
H
TMS
OH
while the remainder of the alkene starting materials and octa-1,7-
diyne were purified by distillation. CpCo(CO)226 (also commercial-
ly available) and CpCo(CH2=CH2)2 were prepared by literature
75
OBz
TMS
H
O
27
methods. BuLi and MeLi solutions were titrated with diphenylace-
tic acid. All reactions involving oxygen sensitive materials em-
ployed degassed solvents, the transfer of materials was carried out
in a glove box, via syringe, or using standard Schlenk techniques,
and the reaction mixtures were maintained under dry N2, until work-
up. Irradiation was effected by a Sylvania ELH 300 W slide projec-
tor lamp, powered by a variable transformer at an applied potential
of 40–60 V. Thin layer chromatography was done on EM Reagents
Kieselgel 60 F254 or EM Reagents neutral Al2O3 60 F254 sheets
(0.2 mm coating). Flash chromatography employed EM Scientific
SiO2 (230–400 mesh), column chromatography Baker SiO2 (60–
200 mesh) or Alfa Al2O3 (60 mesh). High performance liquid chro-
matography (HPLC) was executed on an IBM LC/9533 instrument
equipped with an LC/9522 fixed wavelength (254 nm) detector. For
semi-preparative purposes, two columns, each 25 cm × 10 mm ID,
packed with Microsorb 5 mm silica, were used two in sequence; pre-
parative separations were carried out on 25 cm × 21.4 mm ID col-
umns packed with Dynamax-60A 8 mm silica. Reverse phase HPLC
relied on the same instrument but occurred on Microsorb 5 mm C18
(two columns in sequence) or Dynamax-60A 8 mm C18 packings
under semipreparative and preparative conditions, respectively.
Gas-liquid chromatography (GLC) was performed with a Hewlett-
Packard 5880 instrument on a 6 ft × 2 mm ID glass column contain-
ing 3% OV-101 on Chromosorb W-HP (80/100 mesh), or a 30
m × 0.20 mm ID capillary column loaded with crosslinked 5% phe-
nyl methyl silicone. Melting points were determined in open capil-
H
TMS
OMe
O
O
76
60 + 61 (4:5)
71g
TMS
H
H
TMS
OBz
OMe
O
77
4:5
a CuCl2·H2O (5 equiv), Et3N (5 equiv), THF, H2O, 0 °C, 0.5–2.5 h, ex-
cept as noted.
b A 2:1 mixture of 3 and 4 (Table 1) resulted in only 69.
c CuCl2·H2O (5 equiv), EtOAc, MeCN, 0 °C, 5 min.
d 2 min.
e MeOH, r.t., 30 min.
f MCPBA, NaHCO3, CH2Cl2, r.t., 2 min.
g Regiochemical assignments tentative.
In summary, we have filled a void in the literature of
CpCo-mediated [2+2+2] cycloadditions by describing the
reaction of a,w-diynes (specifically octa-1,7-diynes) with
(cyclo)alkenes to give linear di-, tri-, and tetracyclic cy-
clohexadiene complexes. Without silyl protection, the
diynes give moderate yields of products, but bissilylation
improves this outcome considerably. Using chiral, enan-
tiomerically pure cyclohexene derivatives the method
laries with
a Thomas-Hoover Uni-Melt apparatus and are
uncorrected. Optical rotations were measured on a Perkin-Elmer
model 241 polarimeter in a 10 cm quartz cell at ambient tempera-
ture. A Hewlett-Packard 8450A diode array spectrophotometer en-
abled the recording of UV-Vis spectra, while a Perkin-Elmer model
681 instrument facilitated related analyses in the IR range (polysty-
rene reference at 1601 cm–1). 1H and 13C NMR (proton decoupled)
spectra were collected on the UCB-200, UCB-250, BVX-300, AM-
400, and AM-500 FT instruments. Although chemical shifts are re-
provides complexed analogues of the anthracyclinones. ported in ppm downfield of TMS, they are referenced to the residual
1
proton peak of the respective solvent for H NMR, or the central
peak of the solvent multiplet for 13C NMR. In those cases in which
DEPT 13C NMR was employed, the chemical shift data are aug-
mented by the labels in parentheses corresponding to the number of
hydrogens directly bound to carbon. Selected assignments are based
on additional 2D spectral correlations. The designation ‘Htert’ refers
to the complexed cyclohexadiene ring junction. Mass spectra were
obtained on a Hewlett-Packard 5970A mass selective detector or
provided by the Mass Spectral Service at UCB. Elemental analyses
were performed by the UCB Analytical Service Facility. Products
Some preliminary experiments demonstrate that these
systems, in complexed or uncomplexed form, appear to be
amenable to further synthetic manipulation.
Unless otherwise noted, all materials were obtained from commer-
cial suppliers and used without further purification. THF, Et2O,
benzene, toluene, and m-xylene were distilled from sodium-ben-
zophenone, while CH2Cl2 was purified over CaH2. Maleic anhy-
dride was recrystallized from Et2O, norbornadiene was sublimed,
Synthesis 2010, No. 13, 2179–2200 © Thieme Stuttgart · New York

PAPER
Cobalt-Mediated Cycloadditions
2187
13,28 and 1429 were known. Petroleum ether (PE) used refers to the
fraction boiling in the range 30–40 °C.
1H NMR (300 MHz, CDCl3): d = 4.61 (s, 5 H), 2.43 (br s, 2 H),
2.42–2.30 (m, 2 H), 2.21–1.99 (m, 4 H), 1.86–1.71 (m, 4 H), 1.62–
1.48 (m, 2 H), 1.44–1.12 (m, 8 H), 0.78 (br d, J = 8.4 Hz, 2 H).
Cocyclizations of Alkenes with Various Diynes; General Proce-
dure
13C NMR (75 MHz, CDCl3): d = 92.6, 79.9, 60.0, 42.6, 32.3, 31.1,
28.8, 26.2, 23.6.
A 100 mL round-bottomed flask equipped with a magnetic stir bar
and coil condenser was rinsed with hexamethyldisilazane and dried
at 100 °C for 1 h. It was then charged with the alkene (5–10 equiv)
in anhyd toluene (50 mL) or Et2O (10 mL), degassed by three
freeze-pump-thaw cycles, and the solution degassed by three
freeze-pump-thaw cycles and brought to boil. Separately, a solution
of diyne (1 equiv) in toluene or Et2O (5 mL) was deoxygenated by
a stream of dry N2, CpCo(CO)2 (1 equiv) added, and this mixture in-
jected via syringe pump to the boiling, irradiated alkene solution
over a period of 27–40 h. Heating and irradiation were continued for
3–12 h, the reaction mixture allowed to cool, and the volatile mate-
rials removed under vacuum. The crude, black residue was subject-
ed to flash chromatography (50 g, hexanes) under N2 to furnish the
product(s), described in order of elution (for mixtures).
MS (EI, 70 eV): m/z (%) = 340 (60, [M]+), 266 (17), 216 (100), 214
(35), 145 (55), 131 (25), 117 (23), 91 (22).
HRMS-EI: m/z [M]+ calcd for C21H29Co: 340.1601; found:
340.1609.
UV/Vis (MeOH): lmax (log e) = 263 (4.13), 342 (2.95), 397 nm
(2.85).
7
Red solid; mp 198–200 °C (25% EtOAc in hexanes).
IR (KBr): 2943, 1854, 1785, 1223, 1073, 1002, 910, 819, 729 cm–1.
1H NMR (300 MHz, CDCl3): d = 4.67 (s, 5 H), 3.09 (br s, 2 H), 2.44
(dt, J = 16.6, 6.1 Hz, 2 H), 2.24 (br t, J = 1.3 Hz, 2 H, Htert), 2.21
(dt, J = 16.6, 6.1 Hz, 2 H), 2.04 (m, 2 H), 1.81 (m, 2 H).
13C NMR (75 MHz, CDCl3): d = 172.5, 92.6, 81.1, 45.9, 44.4, 28.6,
23.2.
MS (EI, 70 eV): m/z (%) = 328 (22, [M]+), 256 (29), 252 (11), 188
(11), 187 (17), 124 (100), 59 (16).
3
Red needles; mp 129–130 °C (MeOH).
IR (KBr): 2932, 2842, 1441, 1431, 1246, 802 cm–1.
1H NMR (300 MHz, CDCl3): d = 4.61 (s, 5 H), 2.78 (br s, 2 H,
Halkenyl), 2.37 (dt, J = 16.6, 6.0 Hz, 2 H), 2.15 (dt, J = 16.6, 6.0 Hz,
UV/Vis (MeOH): lmax (log e) = 266 (4.00), 338 (2.75), 392 nm
(2.59).
2 H,), 2.06 (m, 2 H), 1.73 (m, 5 H), 1.46 (m, 2 H), 1.08 (dtt, J = 18.0,
6.0, 6.0 Hz, 1 H), 0.95 (br t, J = 5.8 Hz, 2 H, Htert).
13C NMR (75 MHz, CDCl3): d = 92.7 (C), 80.2 (CH), 57.8 (CH),
41.4 (CH), 34.2 (CH2), 29.2 (CH2), 26.0 (CH2), 23.6 (CH2).
Anal. Calcd for C17H17CoO3: C, 62.20; H, 5.22. Found: C, 62.48; H,
5.26.
MS (EI, 70 eV): m/z (%) = 298 (100, [M]+), 296 (77), 228 (46), 226
(30), 225 (23), 224 (65), 187 (17), 124 (20).
8
Reddish-brown solid; mp 178–179 °C (25% EtOAc in hexanes).
UV/Vis (MeOH): lmax (log e) = 263 (3.99), 338 (2.72), 402 nm
IR (KBr): 2928, 1850, 1770, 1265, 1213, 1055, 994, 910, 827 cm–1.
(2.62).
1H NMR (300 MHz, CDCl3): d = 4.72 (s, 5 H), 3.25 (dd, J = 3.0, 2.1
Hz, 2 H, Htert), 3.00 (t, J = 2.5 Hz, 2 H), 2.46 (dt, J = 16.8, 6.2 Hz,
2 H), 2.19 (dt, J = 16.8, 6.2 Hz, 2 H), 2.02 (m, 2 H), 1.84 (m, 2 H).
Anal. Calcd for C18H23Co: C, 72.47; H, 7.77. Found: C, 72.39; H,
7.71.
4 (admixed with 3)
1H NMR (300 MHz, CDCl3): d = 4.57 (s, 5 H), 2.65 (br s, 2 H,
Halkenyl), the remainder of the resonances were obscured by those of
13C NMR (75 MHz, CDCl3): d = 169.5, 94.5, 81.2, 48.1, 44.0, 28.7,
23.1.
MS (EI, 70 eV): m/z (%) = 328 (67, [M]+), 256 (74), 252 (60), 188
(61), 187 (72), 128 (60), 125 (40), 124 (100), 91 (32), 59 (78).
3.
13C NMR (75 MHz, CDCl3): d = 93.3 (C), 81.0 (CH), 53.7 (CH),
45.6 (CH), 34.5 (CH2), 30.0 (CH2), 25.9 (CH2), 23.8 (CH2).
UV/Vis (MeOH): lmax (log e) = 266 (4.04), 338 (2.95), 394 nm
(2.81).
Anal. Calcd for C17H17CoO3: C, 62.20; H, 5.22. Found: C, 62.23; H,
5.11.
5
Red needles; mp 40–41 °C (MeOH).
IR (film): 2940, 2860, 2820, 1440, 1275, 1116, 809 cm–1.
9
1H NMR (300 MHz, CDCl3): d = 4.64 (s, 5 H), 2.54 (br s, 2 H), 2.36
(dt, J = 15.9, 6.2 Hz, 2 H), 2.22–2.01 (m, 4 H), 1.86–1.73 (m, 2 H),
1.62–1.48 (m, 4 H), 1.32–1.16 (m, 4 H), 0.68 (m, 2 H).
Red solid; mp 124–126 °C (MeOH).
IR (KBr): 2937, 2856, 1430, 1262, 1110, 803 cm–1.
1H NMR (500 MHz, C6D6): d = 4.48 (s, 5 H), 3.84 (m, 1 H), 2.74 (s,
2 H, Halkenyl), 2.30 (dt, J = 16.2, 6.1 Hz, 2 H), 2.02 (dt, J = 16.2, 6.3
Hz, 2 H), 1.98 (s, 2 H), 1.87 (m, 2 H), 1.61 (m, 2 H), 1.46 (m, 2 H),
1.00–0.91 (m, 3 H), 0.69 (s, 2 H, Htert).
13C NMR (75 MHz, CDCl3): d = 92.8, 80.1, 57.0, 37.2, 29.1, 26.5,
23.6, 20.0.
MS (EI, 70 eV): m/z (%) = 312 (77, [M]+), 238 (100), 187 (11), 124
(6), 87 (10), 69 (10), 57 (12).
13C NMR (125 MHz, CDCl3): d = 91.0 (C), 81.9 (CH), 53.5
(CHalkenyl), 47.5 (CH, cyclohexadiene), 41.1 (CH, norbornane
bridgehead), 33.1 (CH2), 30.0 (CH2), 28.9 (CH2), 23.4 (CH2).
UV/Vis (MeOH): lmax (log e) = 263 (4.15), 341 (2.87), 398 nm
(2.81).
MS (EI, 70 eV): m/z (%) = 324 (100, [M]+), 322 (54), 252 (49), 124
(37), 59 (28).
Anal. Calcd for C19H25Co: C, 73.06; H, 8.07. Found: C, 72.77; H,
8.06.
UV/Vis (MeOH): lmax (log e) = 266 (4.21), 343 (2.92), 400 nm
6
(2.83).
Red-brown oil.
Anal. Calcd for C20H25Co: C, 74.06; H, 7.77. Found: C, 73.89; H,
7.64.
IR (film): 2907, 2841, 1443, 1346, 1240, 1111, 1007, 995, 801 cm–1.
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2188
C. Aubert et al.
PAPER
10 (admixed with 9)
HRMS-EI: m/z [M]+ calcd for C19H23CoO: 326.1081; found:
326.1078.
1H NMR (500 MHz, C6D6): d = 4.58 (s, 5 H), 2.81 (s, 2 H), 2.30 (m,
2 H), 2.11 (m, 2 H), 1.87 (m, 2 H), 1.78 (br s, 2 H), 1.75 (br s, 2 H),
1.61 (m, 2 H), 1.33 (m, 2 H), 1.09 (m, 1 H), 1.01 (m, 2 H), 0.60 (m,
1 H).
13C NMR (125 MHz, C6D6): d = 93.2, 80.3, 53.3, 50.5, 44.1, 42.1,
30.5, 29.1, 24.1.
16
Red oil.
1H NMR (300 MHz, CDCl3): d = 4.61 (s, 5 H), 3.65 (m, 4 H), 2.91
(s, 1 H), 2.80 (d, J = 3.0 Hz, 1 H), 2.65–1.20 (m, 15 H), 1.15 (d,
J = 8.1 Hz, 1 H).
11
MS (EI, 70 eV): m/z (%) = 370 (48, [M]+), 324 (28), 185 (28), 184
(100), 158 (38), 124 (60), 91 (42), 86 (66).
Red needles; mp 69–70 °C (MeOH).
IR (KBr): 2930, 2825, 1460, 1430, 1240, 1105, 795 cm–1.
19
1H NMR (250 MHz, CDCl3): d = 4.62 (s, 5 H), 2.65 (br s, 2 H), 2.35
(dt, J = 15.5, 6.0 Hz, 2 H,), 2.12 (m, 4 H), 1.77 (m, 2 H), 1.48 (m, 2
H), 1.28 (m, 4 H), 1.12 (m, 2 H), 0.90 (t, J = 6.9 Hz, 6 H,), 0.69 (td,
J = 5.1, 1.8 Hz, 2 H, Htert).
13C NMR (75 MHz, CDCl3): d = 93.2 (C), 80.0 (CH), 55.7 (CH),
39.4 (CH), 33.7 (CH2), 29.1 (CH2), 23.6 (CH2), 21.4 (CH2), 14.5
(CH3).
Brown plates; mp 115–116 °C (MeOH).
IR (KBr): 2925, 2855, 1448, 1263, 1249, 835, 799 cm–1.
1H NMR (300 MHz, C6D6): d = 4.57 (s, 5 H), 2.52 (dt, J = 15.5, 6.1
Hz, 2 H), 2.30 (dt, J = 15.5, 6.0 Hz, 2 H), 1.91 (m, 2 H), 1.87 (m, 2
H, Htert), 1.76–1.62 (m, 2 H), 1.50–1.40 (m, 2 H), 1.19–0.98 (m, 6
H), 0.26 (s, 18 H).
13C NMR (75 MHz, C6D6): d = 99.2, 81.0, 54.2, 41.6, 33.0, 31.3,
24.3, 23.8, 2.73.
MS (EI, 70 eV): m/z (%) = 456 (4, [M]+), 383 (51), 317 (28), 310
(100), 73 (81).
MS (EI, 70 eV): m/z (%) = 342 (100, [M]+), 340 (24), 299 (15), 273
(8), 272 (9), 270 (9), 244 (6), 201 (14), 187 (13), 124 (7), 67 (6).
UV/Vis (MeOH): lmax (log e) = 265 (4.04), 340 (2.84), 398 nm
(2.76).
UV/Vis (MeOH): lmax (log e) = 281 (3.90), 319 sh (3.27), 371
(2.73), 430 nm (2.64).
Anal. Calcd for C21H31Co: C, 73.66; H, 9.13. Found: C, 73.45; H,
9.12.
Anal. Calcd for C25H41CoSi2: C, 65.75; H, 9.05. Found: C, 65.76; H,
8.97.
12
Red-brown oil.
20
IR (film): 2930, 2865, 1450, 1250, 1198, 797 cm–1.
Brown solid; mp 70–71 °C (MeOH).
IR (film): 2964, 2939, 2878, 1252, 839, 803 cm–1.
1H NMR (300 MHz, C6D6): d = 4.56 (s, 5 H), 2.52 (dt, J = 16.2, 6.3
Hz, 2 H), 2.28 (dt, J = 15.9, 6.1 Hz, 2 H), 1.97 (d, J = 8.0 Hz, 2 H,
Htert), 1.93–1.82 (m, 2 H), 1.74–1.59 (m, 2 H), 1.39–1.17 (m, 4 H),
1.16–1.05 (m, 2 H), 0.95–0.80 (m, 2 H), 0.84 (t, J = 7.0 Hz, 6 H,),
0.30 (s, 18 H).
13C NMR (75 MHz, C6D6): d = 99.0, 81.2, 55.3, 44.3, 37.7, 31.5,
24.2, 23.2, 15.0, 2.75.
MS (EI, 70 eV): m/z (%) = 486 (4, [M]+), 413 (39), 340 (48), 215
(25), 187 (44), 145 (21), 73 (100).
1H NMR (300 MHz, CDCl3): d = 4.57 (s, 5 H), 2.70 (d, J = 4.1 Hz,
1 H), 2.51 (d, J = 2.0 Hz, 1 H), 2.41–2.28 (m, 2 H), 2.25–2.02 (m,
4 H), 1.85–1.72 (m, 2 H), 1.44–1.22 (m, 4 H), 1.21–1.03 (m, 3 H),
1.00–0.81 (m, 2 H), 0.89 (t, J = 6.8 Hz, 3 H), 0.75 (t, J = 7.2 Hz, 3
H), 0.27 (m, 1 H, Htert).
13C NMR (75 MHz, CDCl3): d = 92.8, 92.5, 80.1, 53.6, 53.4, 47.7,
42.6, 41.4, 40.2, 29.6, 29.2, 23.70, 23.68, 21.1, 20.3, 14.6, 14.5.
MS (EI, 70 eV): m/z (%) 342 (84, [M]+), 340 (30), 299 (100), 233
(33), 218 (33), 201 (61), 175 (46), 133 (67), 91 (58).
HRMS-EI: m/z [M]+ calcd for C21H31Co: 342.1758; found:
342.1753.
Anal. Calcd for C27H47CoSi2: C, 66.62; H, 9.73. Found: C, 66.34; H,
9.68.
UV/Vis (MeOH): lmax (log e) = 262 (4.04), 338 (2.90), 396 nm
(2.85).
21
1429
Brown plates; mp 238–239 °C (MeOH).
IR (film): 2955, 2930, 2868, 2810, 1248, 999, 837, 803 cm–1.
Colorless solid; mp 95–96 °C (MeOH).
IR (KBr): 3400–3320, 2931, 2850, 1682, 1503, 1085, 1061, 1043
cm–1.
1H NMR (300 MHz, CDCl3): d = 7.12 (s, 1 H), 6.81 (s, 1 H), 4.72
(m, 1 H), 2.71 (m, 6H), 1.92 (m, 3 H), 1.78 (m, 5 H), 1.59 (d, J = 6.4
Hz, 1 H).
MS (EI, 70 eV): m/z (%) = 202 (100, [M]+), 184 (97), 174 (95), 173
(82), 159 (6.3), 145 (69).
1H NMR (300 MHz, C6D6): d = 4.60 (s, 5 H), 2.67 (dt, J = 16.2, 6.2
Hz, 1 H), 2.45–2.24 (m, 3 H), 1.99–1.57 (m, 6 H), 1.53–1.24 (m, 2
H), 1.20–1.02 (m, 2 H), 1.09 (t, J = 7.3 Hz, 3 H), 1.04 (d, J = 10.4
Hz, 1 H), 0.98 (d, J = 10.4 Hz, 1 H), 0.82 (t, J = 6.8 Hz, 3 H), 0.50–
0.30 (m, 2 H), 0.21 (s, 9 H), 0.20 (s, 9 H).
13C NMR (75 MHz, C6D6): d = 98.0 (C), 97.6 (C), 81.1 (CH), 57.6
(C), 55.1 (C), 48.8 (CH), 43.1 (CH2), 42.4 (CH), 41.2 (CH2), 32.2
(CH2), 31.2 (CH2), 24.7 (CH2), 24.0 (CH2), 23.8 (CH2), 21.3 (CH2),
15.3 (CH3), 14.8 (CH3), 2.61 (CH3), 1.24 (CH3).
15
Red oil.
MS (EI, 70 eV): m/z (%) = 486 (26, [M]+), 413 (40), 73 (100), 59
(19).
1H NMR (300 MHz, CDCl3): d = 4.64 (s, 5 H), 2.80 (d, J = 3.5 Hz,
1 H), 2.76 (d, J = 4.5 Hz, 1 H), 2.51 (dd, J = 10.8, 3.5 Hz, 1 H),
2.46–2.31 (m, 3 H), 2.22 (m, 2 H), 2.14–1.88 (m, 4 H), 1.78 (m, 2
H), 1.60–1.34 (m, 3 H), 0.98 (m, 1 H).
Anal. Calcd for C27H47CoSi2: C, 66.62; H, 9.73. Found: C, 66.79; H,
9.68.
MS (EI, 70 eV): m/z (%) = 326 (39, [M]+), 201 (100), 184 (91), 174
(57), 145 (63), 131 (48), 68 (56).
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PAPER
Cobalt-Mediated Cycloadditions
2189
22
Anal. Calcd for C25H41CoOSi2: C, 63.52; H, 8.74. Found: C, 63.60;
H, 8.71.
Red-brown crystals; mp 115–119 °C (Et2O–PE, 1:10).
IR (KBr): 3400–3300, 2940–2850, 1245, 1007, 836, 795 cm–1.
26
1H NMR (500 MHz, C6D6): d = 4.45 (s, 5 H), 3.30 (br d, J = 9.9 Hz,
1 H), 2.52 (dt, J = 15.8, 5.9 Hz, 1 H), 2.44 (br t, J = 8.5 Hz, 1 H),
2.37–2.25 (m, 2 H), 2.21 (dt, J = 15.7, 5.7 Hz, 1 H), 1.95–1.79 (m,
2 H), 1.74 (m, 2 H, Htert and CHHendo), 1.67 (m, 1 H), 1.58 (m, 1 H),
1.14 (dd, J = 13.1, 6.5 Hz, 1 H, CHHexo), 0.70 (br s, 1 H), 0.21 (s, 9
H), 0.18 (s, 9 H).
13C NMR (125 MHz, C6D6): d = 98.6, 98.5, 80.7, 66.8, 51.3, 48.5,
41.3, 35.9, 31.4, 30.5, 24.3, 23.9, 2.09, 0.50.
MS (EI, 70 eV): m/z (%) = 432 (8, [M]+), 359 (42), 286 (27), 273
(26), 189 (20), 145 (45), 73 (100), 59 (54).
Brown solid; mp 134–135 °C (EtOAc–hexanes, 1:1).
IR (film): 2956, 2874, 1701, 1254, 844, 811 cm–1.
1H NMR (400 MHz, C6D6): d = 4.54 (s, 5 H), 2.70 (dt, J = 16.1, 6.1
Hz, 1 H), 2.68 (d, J = 10.5 Hz, 1 H, Htert), 2.58 (ddd, J = 16.0, 7.6,
5.8 Hz, 1 H), 2.39–2.17 (m, 3 H), 1.93–1.79 (m, 4 H), 1.78–1.68 (m,
2 H), 1.55–1.47 (m, 1 H), 1.31–1.23 (m, 1 H), 1.20–1.09 (m, 1 H),
0.68 (dddd, J = 13.6, 10.6, 9.2, 3.1 Hz, 1 H), 0.24 (s, 9 H), 0.16 (s,
9 H).
13C NMR (100 MHz, C6D6): d = 211.4, 100.8, 99.1, 81.1, 55.7, 54.6,
46.5, 46.2, 39.3, 33.3, 31.2, 30.9, 24.2, 23.9, 23.2, 2.65, 1.85.
MS (EI, 70 eV): m/z (%) = 470 (4, [M]+), 397 (11), 329 (10), 273
(20), 257 (21), 183 (13), 73 (100), 59 (22).
Anal. Calcd for C22H37CoOSi2: C, 61.08; H, 8.62. Found: C, 60.86;
H, 8.53.
23
Anal. Calcd for C25H39CoOSi2: C, 63.79; H, 8.35. Found: C, 63.60;
H, 8.39.
Red-brown crystals; mp 113–114 °C (Et2O–PE, 1:10).
IR (KBr): 3450, 2950–2830, 1245, 831, 804 cm–1.
27
1H NMR (500 MHz, C6D6): d = 4.55 (s, 5 H), 3.73 (m, 1 H), 3.59
(m, 1 H), 3.28 (br s, 1 H), 2.47–2.15 (m, 4 H), 1.76 (m, 2 H), 1.65
(m, 1 H), 1.46 (m, 2 H), 0.95 (m, 1 H, Htert), 0.37 (m, 1 H, CHHexo),
0.30 (s, 9 H), 0.23 (s, 9 H).
13C NMR (125 MHz, C6D6): d = 99.5, 98.3, 81.0, 67.9, 53.0, 51.2,
42.9, 32.1, 31.2, 30.5, 24.4, 23.4, 3.62, 0.61.
Red-brown oil.
IR (film): 2940, 2860, 1248, 1098, 1043, 936, 844, 800 cm–1.
1H NMR (300 MHz, C6D6): d = 4.62 (s, 5 H), 3.53 (m, 1 H), 3.47–
3.26 (m, 3 H), 2.69–2.54 (m, 2 H), 2.48 (d J = 8.4 Hz, 1 H), 2.38
(ddd, J = 13.6, 8.4, 4.6 Hz, 1 H), 2.28 (dt, J = 15.5, 5.6 Hz, 1 H),
2.09 (ddd, J = 13.6, 8.4, 4.6 Hz, 1 H), 1.99–1.83 (m, 2 H), 1.82–
1.71 (m, 1 H), 1.70–1.57 (m, 2 H), 1.56–1.40 (m, 1 H), 1.33–1.13
(m, 3 H), 0.78–0.61 (m, 1 H), 0.48 (s, 9 H), 0.23 (s, 9 H).
MS (EI, 70 eV): m/z (%) = 432 (9, [M]+), 416 (27), 189 (59), 129
(44), 124 (15), 73 (100), 59 (70).
13C NMR (75 MHz, C6D6): d = 110.8, 103.4, 97.5, 81.4, 64.5, 63.0,
54.4, 52.8, 51.7, 38.3, 33.4, 31.9, 30.9, 30.7, 24.6, 23.8, 22.8, 5.25,
2.16.
MS (EI, 70 eV): m/z (%) = 514 (7, [M]+), 441 (56), 124 (16), 99
(13), 86 (80), 73 (100), 59 (20).
Anal. Calcd for C22H37CoOSi2: C, 61.08; H, 8.62. Found: C, 61.01;
H, 8.57.
24
Red-brown oil.
IR (film): 3420, 2950, 2880, 1250, 1015, 840, 800 cm–1.
1H NMR (300 MHz, C6D6): d = 4.54 (s, 5 H), 3.20 (m, 1 H), 2.75
(m, 1 H), 2.55 (m, 1 H), 2.45–2.13 (m, 3 H), 1.91 (td, J = 7.4, 2.7
Hz, 1 H, Htert), 1.90–1.78 (m, 1 H), 1.73–1.48 (m, 3 H), 1.54 (br d,
J = 7.4 Hz, 1 H, Htert), 1.28–1.04 (m, 3 H), 0.98–0.85 (m, 1 H), 0.91
(t, J = 7.0 Hz, 3 H), 0.42 (br s, 1 H), 0.31 (s, 9 H), 0.24 (s, 9 H).
13C NMR (75 MHz, C6D6): d = 100.6 (C), 96.9 (C), 81.3 (CH), 64.8
(CH2), 56.0 (C), 50.4 (C), 48.0 (CH), 42.8 (CH), 37.2 (CH2), 31.7
(CH2), 31.0 (CH2), 24.3 (CH2), 24.0 (CH2), 22.7 (CH2), 14.9 (CH3),
3.28 (CH3), 1.96 (CH3).
28
Colorless oil; bp 86–91 °C/0.5 mm.
IR (film): 2964, 2900, 2175, 1680, 1254, 1113, 845, 762 cm–1.
1H NMR (300 MHz, CDCl3): d = 2.38 (t, J = 6.9 Hz, 2 H), 1.96 (t,
J = 6.4 Hz, 2 H), 1.63 (quint, J = 6.8 Hz, 2 H), 0.17 (s, 9 H), 0.04
(s, 9 H).
13C NMR (75 MHz, CDCl3): d = 185.5, 106.6, 103.0, 96.1, 85.6,
44.1, 22.8, 19.2, 0.27, –0.90.
MS (EI, 70 eV): m/z (%) = 264 (1, [M]+), 249 (29), 157 (27), 133
(29), 125 (44), 97 (33), 73 (100).
MS (EI, 70 eV): m/z (%) = 474 (4, [M]+), 401 (53), 328 (41), 259
(14), 245 (13), 187 (11), 73 (100), 59 (22).
Anal. Calcd for C14H24OSi2: C, 63.57; H, 9.14. Found: C, 63.74; H,
9.12.
Anal. Calcd for C25H43CoOSi2: C, 63.25; H, 9.13. Found: C, 63.39;
H, 9.05.
29
25
Red-brown solid; mp 110–112 °C (EtOAC–hexanes, 1:1).
Brown solid; mp 157–158 °C (EtOAc–hexanes, 1:1).
IR (film): 3440, 2960, 2865, 1671, 1395, 1250, 1033, 1020, 845,
807 cm–1.
IR (film): 3340, 2935, 2860, 1250, 838, 800 cm–1.
1H NMR (400 MHz, C6D6): d = 4.54 (s, 5 H), 3.88 (br s, 1 H), 2.63
(dt, J = 16.0, 5.8 Hz, 1 H), 2.40–2.28 (m, 2 H), 2.25 (br d, J = 7.5
Hz, 1 H, Htert), 2.15 (dt, J = 15.8, 5.6 Hz, 1 H), 1.97–1.80 (m, 3 H,
including Htert), 1.77–1.55 (m, 3 H), 1.54–1.41 (m, 1 H), 1.37–1.19
(m, 2 H), 1.06–0.95 (m, 2 H), 0.58–0.42 (m, 1 H), 0.26 (s, 9 H), 0.22
(s, 9 H).
13C NMR (100 MHz, C6D6): d = 101.2, 97.5, 81.2, 70.2, 53.7, 52.7,
51.1, 34.3, 33.3, 31.8, 30.7, 28.8, 24.4, 23.7, 19.5, 5.07, 2.15.
MS (EI, 70 eV): m/z (%) = 472 (5, [M]+), 399 (15), 257 (22), 243
1H NMR (500 MHz, C6D6): d = 4.57 (s, 5 H), 3.15 (ddd, J = 10.3,
4.0, 2.7 Hz, 1 H), 2.68 (ddd, J = 10.7, 8.0, 5.0 Hz, 1 H), 2.64–2.54
(m, 1 H), 2.31 (m, 1 H), 2.24 (t, J = 8.7 Hz, 1 H, Htert), 2.17–2.02
(m, 4 H, including Htert), 1.67 (m, 1 H), 1.53–1.42 (m, 2 H), 1.19 (m,
1 H), 0.90 (m, 1 H), 0.85 (t, J = 7.0 Hz, 3 H), 0.51 (br s, 9 H), 0.37
(br t, J = 5.1 Hz, 1 H), 0.19 (s, 9 H).
13C NMR (125 MHz, C6D6): d = 205.2, 108.6, 88.1, 81.6, 64.0,
59.4, 58.5, 46.3, 44.7, 39.7, 37.3, 29.6, 23.0, 22.5, 14.9, 3.61, 2.23.
(13), 183 (48), 73 (100), 59 (15).
Synthesis 2010, No. 13, 2179–2200 © Thieme Stuttgart · New York

2190
C. Aubert et al.
PAPER
MS (EI, 70 eV): m/z (%) = 488 (9, [M]+), 415 (15), 399 (10), 347
MS (EI, 70 eV): m/z (%) = 466 (0.4, [M]+), 396 (3), 382 (22), 297
(31), 259 (27), 185 (16), 75 (29), 73 (100), 59 (16).
(69), 269 (69), 84 (60), 73 (63), 69 (49), 57 (100).
Anal. Calcd for C25H41CoO2Si2: C, 61.44; H, 8.46. Found: C, 61.21;
H, 8.47.
Anal. Calcd for C28H42O2Si2: C, 72.04; H, 9.07. Found: C, 71.98; H,
9.19.
30
36
Deep brown solid; mp 163–164 °C (EtOAC–hexanes, 1:1).
Colorless solid; mp 36–40 °C (EtOAC–hexanes, 1:1).
IR (film): 3490, 2930, 2850, 1660, 1250, 990, 835, 810 cm–1.
IR (film): 2965, 2870, 2155, 1649, 1253, 1019, 849, 827 cm–1.
1H NMR (300 MHz, C6D6): d = 4.55 (s, 5 H), 3.12 (m, 1 H), 2.62–
2.50 (m, 2 H), 2.36–2.15 (m, 3 H), 2.12–1.95 (m, 3 H), 1.67–1.44
(m, 3 H), 1.28–1.07 (m, 2 H), 0.90 (t, J = 6.8 Hz, 3 H), 0.63 (br t,
J = 4.8 Hz, 1 H), 0.42 (s, 9 H), 0.22 (s, 9 H).
13C NMR (75 MHz, C6D6): d = 205.6, 111.2, 85.8, 81.4, 65.5, 64.5,
52.5, 49.6, 41.2, 39.5, 36.9, 29.2, 22.7, 22.4, 14.7, 3.20, 2.32.
1H NMR (300 MHz, CDCl3): d = 7.77 (m, 2 H), 7.59 (m, 2 H), 1.64
(sept, J = 6.9 Hz, 1 H), 0.91 (s, 6 H), 0.87 (d, J = 6.9 Hz, 6 H), 0.23
(s, 9 H), 0.22 (s, 6 H).
13C NMR (75 MHz, CDCl3): d = 178.52, 178.48, 139.1, 138.8,
131.9, 131.8, 129.7, 129.6, 102.5, 101.8, 101.4 (2 C), 34.4, 23.6,
20.6, 18.6, –0.84, –3.11.
MS (EI, 70 eV): m/z (%) = 488 (10, [M]+), 347 (13), 321 (33), 305
MS (EI, 70 eV): m/z (%) = 396 (1, [M]+), 311 (100), 297 (15), 237
(22), 275 (21), 75 (73), 73 (100), 66 (74), 59 (22).
(19), 155 (9), 73 (36).
Anal. Calcd for C25H41CoO2Si2: C, 61.44; H, 8.46. Found: C, 61.50;
H, 8.40.
Anal. Calcd for C23H32O2Si2: C, 69.64; H, 8.13. Found: C, 69.84; H,
8.20.
31
Compound 37 from 40 via 41 and 42
Brown solid; mp 151–152 °C (EtOAC–hexanes, 1:1).
IR (film): 2945, 2800, 1700, 1675, 1250, 842, 812 cm–1.
41: To ice-cooled 40 (15.4 g, 103 mmol) in THF (50 mL) was added
a solution of ClMgC≡CSiMe3 (210 mmol) in THF (160 mL) over
15 min and the mixture stirred for another 30 min. The solution was
quenched with aq 3.0 N HCl (100 mL), the aqueous phase extracted
with Et2O (2 × 100 mL), then aq 1.0 N HCl (2 × 100 mL), and dried
(MgSO4). The crude product was dissolved in MeOH (50 mL), aq
1.0 N HCl (5.0 mL) added, and the pale yellow solution stirred at
r.t. overnight. Aqueous workup gave 41 (19.9 g, 84%); colorless
solid; mp 55–57 °C (Et2O–PE).
1H NMR (400 MHz, C6D6): d = 4.55 (s, 5 H), 2.71 (ddd, J = 15.8,
11.5, 4.3 Hz, 1 H), 2.70 (d, J = 10.5 Hz, 1 H, Htert), 2.63–2.53 (m, 2
H), 2.49 (dddd, J = 15.9, 5.6, 4.2, 1.2 Hz, 1 H), 2.20 (ddd, J = 16.8,
11.7, 5.0 Hz, 1 H), 2.06 (m, 1 H), 1.78 (d, J = 5.7 Hz, 1 H), 1.76 (d,
J = 6.3 Hz, 1 H), 1.74–1.63 (m, 2 H), 1.24–1.06 (m, 2 H), 0.65
(dddd, J = 13.8, 10.4, 10.2, 4.1 Hz, 1 H), 0.40 (br s, 9 H), 0.14 (s, 9
H).
13C NMR (100 MHz, C6D6): d = 210.9, 205.1, 111.0, 87.2, 81.5,
57.8, 55.0, 54.4, 47.8, 39.8, 39.5, 33.5, 29.6, 22.9, 22.6, 3.65, 1.66.
MS (EI, 70 eV): m/z (%) = 484 (7, [M]+), 345 (21), 271 (49), 243
(17), 73 (76), 58 (63).
IR (KBr): 2960, 1765, 1471, 1283, 1254, 1069, 968, 850, 748, 712
cm–1.
1H NMR (300 MHz, CDCl3): d = 7.87 (d, J = 7.6 Hz, 1 H), 7.72 (td,
J = 7.5, 1.0 Hz, 1 H), 7.55 (m, 2 H), 6.04 (s, 1 H), 0.15 (s, 9 H).
13C NMR (75 MHz, CDCl3): d = 169.4, 146.8, 134.6, 129.7, 125.6,
125.0, 122.5, 97.5, 94.4, 70.3, –0.48.
Anal. Calcd for C25H37CoO2Si2: C, 61.95; H, 7.69. Found: C, 62.01;
H, 7.64.
MS (EI, 70 eV): m/z (%) = 230 (23, [M]+), 215 (79), 200 (82), 187
(100), 128 (44), 105 (34).
32
Dark brown solid; mp 173–174 °C (EtOAC–hexanes, 1:1).
IR (film): 2932, 2900, 1695, 1672, 1397, 1250, 839, 810 cm–1.
Anal. Calcd for C13H14O2Si: C, 67.79; H, 6.13. Found: C, 67.74; H,
6.08.
42: To a stirred solution of 41 (1.00 g, 4.34 mmol) in toluene (20
mL) at –78 °C was added DIBAL-H (1.5 M in toluene, 3.0 mL, 4.5
mmol) over 2 min. The stirring was continued for 45 min, MeOH
added (1.0 mL), and the mixture subjected to acidic (aq 0.1 N HCl,
Et2O) workup, furnishing a waxy mixture of the diastereomeric lac-
tols 42 contaminated by a small amount of its hydroxy aldehydic
form (937 mg, 93%; 7:5:1); colorless wax; mp 62–70 °C.
1H NMR (400 MHz, CDCl3): d (major diastereomer) = 7.41–7.34
(m, 4 H), 6.54 (d, J = 5.4 Hz, 1 H), 6.02 (s, 1 H), 3.79 (d, J = 7.0
Hz, 1 H), 0.15 (s, 9 H).
13C NMR (100 MHz, CDCl3): d (major diastereomer) = 139.7,
138.5, 129.7, 128.6, 122.8, 121.8, 102.2, 101.4, 91.3, 72.4, –0.29.
1H NMR (400 MHz, CDCl3): d (minor diastereomer) = 7.41–7.34
(m, 4 H), 6.35 (d, J = 9.5 Hz, 1 H), 5.73 (s, 1 H), 3.54 (d, J = 9.6
Hz, 1 H), 0.14 (s, 9 H).
13C NMR (100 MHz, CDCl3): d (minor diastereomer) = 139.5,
138.7, 129.8, 128.7, 123.0, 121.9, 103.3, 101.1, 91.4, 72.0, –0.32.
1H NMR (400 MHz, CDCl3): d (hydroxy aldehyde isomer) = 10.13
(s, 1 H), 7.85 (d, J = 7.5 Hz, 1 H), 7.80 (d, J = 7.1 Hz, 1 H), 7.62 (t,
J = 7.5 Hz, 1 H), 7.53 (t, J = 7.1 Hz, 1 H), 5.85 (d, J = 6.2 Hz, 1 H),
4.34 (d, J = 6.6 Hz, 1 H), 0.17 (s, 9 H).
1H NMR (400 MHz, C6D6): d = 4.54 (s, 5 H), 2.94 (d, J = 10.1 Hz,
1 H, Htert), 2.67 (m, 1 H), 2.35–1.98 (m, 5 H), 1.94–1.77 (m, 2 H),
1.62 (m, 1 H), 1.45 (m, 1 H), 1.25–1.06 (m, 2 H), 0.60 (dddd,
J = 13.5, 10.4, 9.4, 3.6 Hz, 1 H), 0.43 (s, 9 H), 0.06 (s, 9 H).
13C NMR (100 MHz, C6D6): d = 209.6, 204.3, 108.6, 89.1, 81.4,
66.7, 64.0, 56.0, 46.4, 39.9, 39.0, 33.1, 29.6, 23.2, 22.4, 2.63, 2.38.
MS (EI, 70 eV): m/z (%) = 484 (9, [M]+), 411 (5), 345 (15), 271
(60), 107 (13), 75 (39), 73 (100), 59 (13).
Anal. Calcd for C25H37CoO2Si2: C, 61.95; H, 7.69. Found: C, 61.69;
H, 7.85.
35
Pale yellow oil.
IR (film): 2960, 2864, 2158, 1771, 1646, 1468, 1249, 1017, 825,
778 cm–1.
1H NMR (300 MHz, CDCl3): d = 7.78 (AA¢m, 2 H), 7.58 (BB¢m, 2
H), 1.65 (sept, J = 6.8 Hz, 2 H), 0.91 (s, 12 H), 0.88 (d, J = 6.8 Hz,
12 H), 0.22 (s, 12 H).
13C NMR (75 MHz, CDCl3): d = 178.5, 139.0, 131.9, 129.7, 102.5,
101.7, 34.5, 23.6, 20.7, 18.6, –3.10.
Synthesis 2010, No. 13, 2179–2200 © Thieme Stuttgart · New York

PAPER
Cobalt-Mediated Cycloadditions
2191
13C NMR (100 MHz, CDCl3): d (hydroxy aldehyde isomer) =
194.4, 141.4, 135.0, 134.5, 133.5, 128.8, 128.7, 103.6, 92.1, 62.9,
–0.32.
13C NMR (125 MHz, C6D6): d = 188.9, 188.8, 134.9 (2 C), 133.3 (2
C), 126.6 (2 C), 84.8 (2 C), 82.9, 82.7, 65.3, 62.5, 38.5, 37.7, 30.5,
26.5, 21.0, 20.0.
37: To 42 (5.08 g, 21.9 mmol) in THF (20 mL) at r.t. was added a
solution of ClMgC≡CSiMe2Et (45.5 mmol)30 in THF (50 mL) over
5 min, and the mixture stirred overnight and then subjected to stan-
dard aqueous workup. The crude product was dissolved in acetone
(100 mL), cooled in an ice-water bath, and a solution of Jones
reagent31 (35.2 mL, l43.6 mmol) was added over 30 min. After stir-
ring for 2 h at r.t., aqueous workup yielded 37 (6.89 g, 93%); pale
orange oil.
MS (EI, 70 eV): m/z (%) = 388 (17, [M]+), 386 (100), 320 (20), 262
(37), 207 (69), 124 (35), 69 (56), 57 (60), 55 (56).
UV/Vis (MeOH): lmax (log e) = 263 (4.22), 297 sh (3.93), 327 sh
(3.81), 438 nm (3.18).
Anal. Calcd for C23H21CoO2: C, 71.13; H, 5.45. Found: C, 70.88; H,
5.30.
45
IR (film): 2965, 2158, 1647, 1248, 1015, 846 cm–1.
Red needles; mp 189–191 °C (EtOAc).
1H NMR (300 MHz, CDCl3): d = 7.79 (m, 2 H), 7.59 (m, 2 H), 1.00
(t, J = 7.8 Hz, 3 H), 0.66 (q, J = 7.8 Hz, 2 H), 0.24 (s, 9 H), 0.21 (s,
6 H).
13C NMR (75 MHz, CDCl3): d = 178.59, 178.56, 139.0, 138.9,
131.9 (2 C), 129.7 (2 C), 101.9, 101.6, 101.5, 101.0, 7.3, 7.2, –0.81,
–2.93.
IR (KBr): 2934, 2860, 1656, 1589, 1335, 1297, 1245, 845, 807, 729
cm–1.
1H NMR (300 MHz, CDCl3): d = 8.13 (AA¢m, 2 H), 7.71 (BB¢m, 2
H), 4.61 (s, 5 H), 2.19 (br s, 2 H, Htert), 1.51 (m, 2 H), 1.07 (m, 6 H),
0.26 (br s, 18 H).
13C NMR (75 MHz, CDCl3): d = 191.0 (C), 134.4 (C), 133.3 (CH),
126.0 (CH), 92.6 (C), 82.6 (CH), 71.0 (C), 41.6 (CH), 32.8 (CH2),
23.2 (CH2), 2.65 (CH3).
MS (EI, 70 eV): m/z (%) = 340 (14, [M]+), 312 (100), 297 (25), 237
(35), 73 (43).
Anal. Calcd for C19H24O2Si2: C, 67.01; H, 7.10. Found: C, 67.09; H,
7.37.
MS (EI, 70 eV): m/z (%) = 532 (45, [M]+), 408 (30), 392 (15), 319
(30), 73 (100).
UV/Vis (MeOH): lmax (log e) = 279 (4.26), 312 sh (4.02), 345 sh
38
(3.77), 472 nm (3.26).
The procedure described for 37 was repeated using ClMgC≡CSiEt3
to render 38; colorless oil.
IR (film): 2960, 2875, 2150, 1648, 1250, 1018, 847 cm–1.
Anal. Calcd for C29H37CoO2Si2: C, 65.39; H, 7.00. Found: C, 65.38;
H, 6.81.
1H NMR (300 MHz, CDCl3): d = 7.79 (m, 2 H), 7.58 (m, 2 H), 0.99
(t, J = 8.1 Hz, 9 H), 0.66 (q, J = 8.1 Hz, 6 H), 0.23 (s, 9 H).
A second product (6%) was the CpCo(cyclopentadienone) complex
(Figure 6) derived from 34.
13C NMR (75 MHz, CDCl3): d = 178.6, 178.4, 139.0, 138.9, 131.9
(2 C), 129.7, 129.6, 102.7, 101.43, 101.40, 99.8, 7.3, 3.76, –0.88.
O
TMS
MS (EI, 70 eV): m/z (%) = 368 (6, [M]+), 353 (14), 340 (79), 339
(100), 311(18), 283 (29), 165 (17), 73 (30).
O
TMS
O
CpCo
39
This intermediate on route to 3415 was crystallized from a mixture
(meso/d,l = 1.7:1) containing its d,l isomer [1H NMR (300 MHz,
CDCl3): d = 7.59 (AA¢m, 2 H), 7.34 (BB¢m, 2 H), 5.99 (s, 2 H), 3.48
(br s, 2 H), 0.20 (s, 18 H)]; colorless solid; mp 88–93 °C (PE).
Figure 6 CpCo[1,3-bis(trimethylsilyl)-1H-cyclopenta[b]naphtha-
lene-2,4,9-trione]
IR (KBr): 3530, 3365, 2960, 2898, 2170, 1422, 1248, 1031, 990,
973, 840, 760 cm–1.
1H NMR (500 MHz, CDCl3): d = 7.79 (AA¢m, 2 H), 7.38 (BB¢m, 2
H), 5.83 (s, 2 H), 3.18 (br s, 2 H), 0.21 (s, 18 H).
13C NMR (125 MHz, CDCl3): d = 137.6, 129.1, 128.1, 103.9, 92.8,
62.3, –0.24.
MS (EI, 70 eV): m/z (%) = 330 (1, [M]+), 312 (12), 214 (15), 147
(25), 75 (29), 73 (100).
Red-orange solid; mp 203–204 °C (EtOAc).
IR (KBr): 2216, 1672, 1621, 1586, 1552, 1392, 1243, 1227, 1003,
849, 728, 642 cm–1.
1H NMR (300 MHz, CDCl3): d = 8.21 (AA¢m, 2 H) 7.77 (BB¢m, 2
H), 4.94 (s, 5 H), 0.43 (s, 18 H).
13C NMR (75 MHz, CDCl3): d = 224.4, 134.6, 134.0, 126.9, 91.4,
83.1, 50.7, 0.26 [1 C (C=O) not detected].
MS (EI, 70 eV): m/z (%) = 478 (46, [M]+), 463 (14), 434 (13), 339
(10), 237 (13), 198 (10), 124 (15), 73 (51).
Anal. Calcd for C18H26O2Si2: C, 65.40; H, 7.93. Found: C, 65.63; H,
8.08.
HRMS-EI: m/z [M]+ calcd for C24H27CoO3Si2: 478.0831; found:
478.0822.
43 and 44 (1:1)
Red solid; mp 149–155 °C (EtOAc–hexanes, 1:3).
UV/Vis (THF): lmax (log e) = 258 (4.20), 303 (4.05), 404 nm (3.23).
IR (KBr): 2939, 2862, 1663, 1592, 1412, 1323, 1285, 1265, 961,
814, 733 cm–1.
Anal. Calcd for C24H27CoO3Si2: C, 60.24; H, 5.67. Found: C, 60.22;
H, 5.60.
1H NMR (500 MHz, C6D6): d = 8.36 (m, 4 H), 7.16 (m, 4 H), 4.34
(d, J = 3.4 Hz, 2 H, Halkenyl), 4.225 (s, 5 H), 4.222 (s, 5 H), 4.13 (br
s, 2 H, Halkenyl), 1.89 (m, 2 H, 44-Htert), 1.54 (m, 2 H), 1.46 (m, 2 H),
1.36–1.21 (m, 8 H), 1.02 (m, 2 H), 0.93 (m, 2 H), 0.72 (m, 2 H, 43-
Htert).
46
Reddish-brown powder; mp 206–210 °C (EtOAc).
IR (KBr): 2945, 2900, 1715, 1667, 1597, 1270, 1109, 970, 851, 813,
732, 710 cm–1.
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1H NMR (400 MHz, CDCl3): d = 8.19 (dd, J = 7.0, 1.7 Hz, 1 H),
8.11 (dd, J = 7.0, 1.1 Hz, 1 H), 8.03 (d, J = 7.0 Hz, 2 H), 7.74 (m,
2 H), 7.57 (t, J = 7.4 Hz, 1 H), 7.47 (t, J = 7.2 Hz, 2 H), 5.68 (br s,
1 H), 4.63 (s, 5 H), 2.70 (br d, J = 7.2 Hz, 1 H, Htert), 2.26 (ddd,
J = 11.6, 7.4, 4.9 Hz, 1 H, Htert), 1.79 (m, 1 H), 1.62 (m, 1 H), 1.38
(m, 1 H), 1.28–1.10 (m, 2 H), 0.53 (m, 1 H), 0.38 (br s, 9 H), 0.28
(s, 9 H).
13C NMR (100 MHz, CDCl3): d = 191.0 (C), 190.8 (C), 165.2 (C),
134.6 (C), 134.2 (C), 133.6 (CH), 133.4 (CH), 132.8 (CH), 130.8
(C), 129.6 (CH), 128.4 (CH), 126.13 (CH), 126.09 (CH), 95.1 (C),
91.4 (C), 82.9 (CH), 72.8 (CH), 70.6 (C), 65.4 (C), 50.4 (CH), 34.5
(CH2), 33.0 (CH), 25.3 (CH2), 20.0 (CH2), 3.10 (br, CH3), 1.75
(CH3).
(br t, J = 7.4 Hz, 3 H), 1.06 (dd, J = 12.1, 10.6 Hz, 1 H), 0.9–0.8 (m,
2 H), 0.82 (d, J = 6.8 Hz, 6 H), 0.76 (s, 3 H), 0.75 (s, 3 H), 0.5–0.3
(br s, 6 H), 0.34 (s, 9 H), –0.02 (s, 6 H).
13C NMR (75 MHz, toluene-d8, +100 °C): d = 190.6 (2 C), 166.7,
135.2, 135.1, 133.6, 133.3, 126.7, 126.5, 100.4, 95.6, 83.2, 79.8,
79.0, 76.7, 51.5, 51.3, 39.6, 35.4, 34.9, 25.6, 20.8, 20.7, 19.01,
18.97, 10.8 (br), 8.6 (br), 2.60 (2 C), 0.12, 0.0 (br), –0.97 (the sig-
nals for the terminal diene carbons were not observed).
MS (FAB, NBA): m/z (%) = 744 [M]+.
UV/Vis (MeOH): lmax (log e) = 280 (4.38), 310 sh (4.14), 345 sh
(3.85), 474 nm (3.34).
Anal. Calcd for C40H57CoO4Si3: C, 64.48; H, 7.71. Found: C, 64.58;
H, 8.10.
MS (EI, 70 eV): m/z (%) = 652 (1, [M]+), 586 (8), 530 (23), 406
(45), 392 (35), 194 (36), 189 (64), 179 (100), 147 (53), 135 (58),
124 (37), 105 (55).
50
Red-brown powder; mp 74–79 °C (EtOAc–hexanes); [a]D20 +285 (c
Anal. Calcd for C36H41CoO4Si2: C, 66.23; H, 6.33. Found: C, 66.23;
H, 6.34.
4.00 × 10–4, CHCl3).
IR (KBr): 2960, 2870, 1667, 1599, 1257, 832, 812 cm–1.
1H NMR (500 MHz, C6D6): d = 8.13 (m, 1 H), 8.07 (m, 1 H), 7.07
(m, 2 H), 4.78 (dd, J = 6.6, 3.8 Hz, 1 H), 4.45 (s, 1 H), 4.36 (s, 5 H),
4.23 (s, 1 H), 2.77 (dd, J = 8.3, 3.7 Hz, 1 H), 2.66 (dt, J = 10.6, 7.5
Hz, 1 H), 2.37 (ddd, J = 11.8, 7.0, 2.7 Hz, 1 H), 2.00 (ddd, J = 9.6,
6.9, 2.7 Hz, 1 H), 1.60 (d, J = 10.3 Hz, 1 H), 1.54 (sept, J = 6.8 Hz,
1 H), 1.17 (t, J = 7.6 Hz, 3 H), 1.16 (m, 1 H), 0.90 (m, 2 H), 0.85 (d,
J = 6.8 Hz, 3 H), 0.84 (d, J = 6.8 Hz, 3 H), 0.76 (s, 3 H), 0.75 (s, 3
H), 0.61 (s, 3 H), 0.39 (br s, 3 H), 0.37 (s, 3 H), 0.31 (s, 3 H) 0.05
(s, 3 H), –0.026 (s, 3 H), –0.029 (s, 3 H).
13C NMR (75 MHz, CDCl3): d = 190.7, 190.4, 166.4, 134.53,
134.48, 133.6, 133.3, 126.5, 126.3, 97.7, 92.1, 82.9, 79.4, 78.7,
76.8, 68.1, 64.4, 51.0, 50.8, 39.0, 34.7, 34.4, 25.0, 20.5, 20.4, 18.85,
18.75, 10.0, 8.81, 3.94, 3.79, 1.67, 0.01, –0.09, –0.14, –0.37.
48
Dark red oil.
IR (KBr): 2955, 1667, 1596, 1251, 1165, 996, 846, 830, 808 cm–1.
0.40
0.40
0.40
Si
O
1.18
0.75 0.84
0.77 0.85
8.14 or 8.07
−0.02
2.41
2.68
H 1.55
OSi
−0.03
7.06
4.25
4.47
2.01
1.60
2.77
8.14 or 8.07
4.35
4.79
0.36
0.62
O
Si
0.05
O
CpCo
MS (FAB, NBA): m/z (%) = 744 [M]+.
Figure 7 1H NMR assignments by 2D NMR
UV/Vis (MeOH): lmax (log e) = 279 (4.20), 307 sh (3.97), 341 sh
(3.70), 470 nm (3.16).
Anal. Calcd for C40H57CoO4Si3: C, 64.48; H, 7.71. Found: C, 64.43;
H, 7.99.
1H NMR [400 MHz, C6D6, assignments by 2D NMR (Figure 7)]:
d = 8.14 (m, 1 H), 8.07 (m, 1 H), 7.06 (m, 2 H), 4.79 (dd, J = 6.7,
3.6 Hz, 1 H), 4.47 (br s, 1 H), 4.35 (s, 5 H), 4.25 (d, J = 1.2 Hz, 1
H), 2.77 (dd, J = 8.4, 3.6 Hz, 1 H), 2.68 (ddd, J = 10.6, 8.5, 7.0 Hz,
1 H), 2.41 (ddd, J = 12.2, 7.0, 3.0 Hz, 1 H), 2.01 (ddd, J = 10.2, 6.7,
3.0 Hz, 1 H), 1.60 (d, J = 10.2 Hz, 1 H), 1.55 (sept, J = 6.9 Hz, 1 H),
1.18 (dd, J = 12.1, 10.7 Hz, 1 H), 0.85 (d, J = 6.9 Hz, 3 H), 0.84 (d,
J = 6.9 Hz, 3 H), 0.77 (s, 3 H), 0.75 (s, 3 H), 0.62 (s, 3 H), 0.40 (br
s, 9 H), 0.36 (s, 3 H), 0.05 (s, 3 H), –0.02 (s, 3 H), –0.03 (s, 3 H).
13C NMR (100 MHz, C6D6): d = 190.7, 190.6, 166.5, 134.6, 134.4,
133.6, 133.3, 126.5, 126.3, 94.8, 91.9, 82.8, 79.4, 78.7, 76.8, 67.9,
64.5, 51.0, 39.0, 34.8, 34.4, 32.3, 25.0, 20.5, 20.4, 18.84, 18.75,
3.92, 3.83, 2.45, 1.68, –0.09, –0.37.
The experiment generating 49 and 50 also gave, as the slowest elut-
ing component on column chromatography, the CpCo(cyclopenta-
dienone) complex (Figure 8) (11%) derived from 37.
O
SiMe2Et
O
TMS
O
CpCo
Figure 8 CpCo[1-(ethyldimethylsilyl)-3-(trimethylsilyl)-1H-cy-
clopenta[b]naphthalene-2,4,9-trione]
MS (FAB, NBA): m/z (%) = 730 [M]+.
Anal. Calcd for C39H55CoO4Si3: C, 64.08; H, 7.58. Found: C, 64.47;
H, 7.84.
Red powder; mp 169–172.5 °C (EtOAc–hexanes).
49
IR (KBr): 2960, 2910, 1683, 1609, 1394, 1248, 1231, 1010, 829,
708 cm–1.
1H NMR (500 MHz, C6D6): d = 8.12 (m, 2 H), 7.09 (m, 2 H), 4.33
(s, 5 H), 1.22 (m, 5 H), 0.64 (s, 3 H), 0.62 (s, 9 H), 0.55 (s, 3 H).
Red brown powder; mp 59–64 °C (EtOAc–hexanes); [a]D20 +177 (c
1.65 × 10–3, CHCl3).
IR (KBr): 2960, 2875, 1668, 1597, 1259, 833, 810 cm–1.
1H NMR (300 MHz, toluene-d8, +100 °C): d = 8.07 (m, 1 H), 7.98
(m, 1 H), 7.20 (m, 2 H), 4.69 (dd, J = 6.6, 3.6 Hz, 1 H), 4.44 (s, 5
H), 4.26 (br t, J = 1.0 Hz, 1 H), 4.07 (br d, J = 1.3 Hz, 1 H), 2.70
(dd, J = 8.3, 3.5 Hz, 1 H), 2.60 (ddd, J = 10.5, 8.4, 6.9 Hz, 1 H),
2.28 (ddd, J = 12.2, 6.9, 3.0 Hz, 1 H), 1.92 (ddd, J = 9.6, 6.8, 3.1
Hz, 1 H), 1.55 (sept, J = 6.8 Hz, 1 H), 1.53 (d, J = 9.9 Hz, 1 H), 1.11
13C NMR (125 MHz, C6D6): d = 187.42, 187.41, 175.7, 135.17,
135.15, 133.5 (2 C), 126.7 (2 C), 91.8, 82.4, 80.7, 71.0, 70.7, 8.18,
8.13, 0.39, –1.69, –2.11.
MS (EI, 70 eV): m/z (%) = 492 (5, [M]+), 235 (8), 221 (11), 161
(49), 147 (100), 133 (79), 73 (48).
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Cobalt-Mediated Cycloadditions
2193
UV/Vis (MeOH): lmax (log e) = 257 (4.40), 300 (4.30), 402 (3.48),
474 nm (3.12).
O
O
SiEt3
SiEt3
Anal. Calcd for C25H29CoO3Si2: C, 60.96; H, 5.93. Found: C, 61.00;
H, 6.00.
O
TMS
TMS
O
CpCo
O
CpCo
51
Red-brown powder; mp 75–81 °C (EtOAc–hexanes); [a]D20 +329 (c
7.0 × 10–4, CHCl3).
Figure 9 CpCo[1-(triethylsilyl)-2-(trimethylsilyl)cyclobu-
ta[b]naphthalene-3,8-dione] and CpCo[1-(triethylsilyl)-3-(trimethyl-
silyl)-1H-cyclopenta[b]naphthalene-2,4,9-trione]
IR (KBr): 2965, 2878, 1668, 1598, 1255, 999, 832, 811 cm–1.
1H NMR (500 MHz, C6D6): d = 8.13 (m, 1 H), 8.05 (m, 1 H), 7.08
(m, 2 H), 4.82 (dd, J = 6.3, 3.4 Hz, 1 H), 4.47 (s, 1 H), 4.38 (s, 5 H),
4.25 (s, 1 H), 2.77 (dd, J = 8.5, 3.5 Hz, 1 H), 2.71 (ddd, J = 10.6,
8.5, 7.1 Hz, 1 H), 2.42 (ddd, J = 12.1, 7.0, 2.9 Hz, 1 H), 2.03 (ddd,
J = 9.6, 6.6, 2.7 Hz, 1 H), 1.61 (d, J = 10.2 Hz, 1 H), 1.60–1.53 (m,
1 H), 1.54 (sept, J = 6.9 Hz, 1 H), 1.30 (t, J = 7.8 Hz, 3 H), 1.22 (t,
J = 7.8 Hz, 6 H), 1.18 (dd, J = 12.2, 10.8 Hz, 1 H), 1.09 (dq,
J = 15.0, 7.5 Hz, 1 H), 0.97–0.91 (m, 2 H), 0.85 (d, J = 6.9 Hz, 3 H),
0.84 (d, J = 6.9 Hz, 3 H), 0.77 (s, 3 H), 0.75 (s, 3 H), 0.69 (dq,
J = 15.0, 7.8 Hz, 1 H), 0.40 (br s, 9 H), 0.29 (dq, J = 15.0, 7.8 Hz,
1 H), –0.02 (s, 3 H), –0.03 (s, 3 H).
CpCo[1-(triethylsilyl)-2-(trimethylsilyl)cyclobuta[b]naphtha-
lene-3,8-dione]
Red powder; mp 114–115 °C (EtOAc–hexanes).
IR (KBr): 2950, 2875, 1663, 1597, 1463, 1218, 842, 820, 715 cm–1.
1H NMR (500 MHz, C6D6): d = 8.21 (m, 2 H), 7.10 (m, 2 H), 4.43
(s, 5 H), 1.08 (t, J = 7.8 Hz, 9 H), 0.94 (dq, J = 15.2, 7.6 Hz, 3 H),
0.80 (dq, J = 15.3, 7.7 Hz, 3 H), 0.35 (s, 9 H).
13C NMR (125 MHz, C6D6): d = 186.1, 186.0, 136.8 (2 C), 132.43,
132.41, 126.30, 126.28, 81.7, 80.6, 78.6, 78.51, 78.46, 8.16, 5.12,
0.59.
13C NMR (125 MHz, C6D6): d = 190.8, 190.7, 166.4, 134.7, 134.4,
133.6, 133.3, 126.5, 126.3, 95.2, 91.5, 82.9, 79.3, 79.0, 76.8, 67.4,
65.7, 51.2, 50.8, 39.2, 35.0, 34.4, 25.0, 20.5, 20.4, 18.9, 18.8, 10.1,
9.69, 9.43, 8.26, 7.62, 6.79, 2.58, –0.09, –0.38.
MS (EI, 70 eV): m/z (%) = 492 (46, [M]+), 463 (30), 435 (21), 87
(49), 73 (71), 59 (100).
UV/Vis (MeOH): lmax (log e) = 255 sh (4.38), 274 (4.43), 326
MS (FAB, NBA): m/z (%) = 772 [M]+.
(4.27), 383 (3.59), 470 nm (2.99).
UV/Vis (MeOH): lmax (log e) = 280 (4.28), 306 sh (4.07), 340 sh
(3.79), 470 nm (3.26).
Anal. Calcd for C26H33CoO2Si2: C, 63.39; H, 6.75. Found: C, 63.75;
H, 6.89.
Anal. Calcd for C42H61CoO4Si3: C, 65.25; H, 7.95. Found: C, 64.95;
H, 8.11.
CpCo[1-(triethylsilyl)-3-(trimethylsilyl)-1H-cyclopen-
ta[b]naphthalene-2,4,9-trione]
Red-brown powder; mp 140.5–144 °C (EtOAc–hexanes).
52
Red-brown powder; mp 68–72 °C (EtOAc–hexanes); [a]D20 +370 (c
IR (KBr): 2955, 2875, 1672, 1627, 1595, 1393, 1230, 1005, 826,
730 cm–1.
1H NMR (500 MHz, C6D6): d = 8.13 (m, 2 H), 7.15 (m, 2 H), 4.38
(s, 5 H), 1.27 (dq, J = 13.5, 6.7 Hz, 3 H), 1.23 (t, J = 6.7 Hz, 9 H),
1.06 (dq, J = 13.5, 6.7 Hz, 3 H), 0.60 (s, 9 H).
13C NMR (125 MHz, C6D6): d = 187.5, 187.4, 175.8, 135.2, 135.1,
133.5 (2 C), 126.8, 126.7, 91.83, 91.79, 82.5, 71.1, 70.4, 8.53, 4.69,
0.39.
MS (EI, 70 eV): m/z (%) = 520 (100, [M]+), 505 (20), 491 (92), 237
(24), 198 (24), 124 (58), 73 (52), 59 (53).
HRMS-EI: m/z [M]+ calcd for C27H33CoO3Si2: 520.1300; found:
520.1308.
1.2 × 10–4, CHCl3).
IR (KBr): 2963, 2878, 1667, 1600, 1255, 1168, 1001, 817 cm–1.
1H NMR (500 MHz, C6D6): d = 8.14 (m, 1 H), 8.05 (m, 1 H), 7.08
(m, 2 H), 4.78 (dd, J = 6.6, 3.9 Hz, 1 H), 4.44 (s, 1 H), 4.38 (s, 5 H),
4.23 (s, 1 H), 2.79 (dd, J = 8.2, 3.7 Hz, 1 H), 2.66 (dt, J = 10.9, 7.6
Hz, 1 H), 2.34 (ddd, J = 12.1, 6.8, 2.9 Hz, 1 H,), 2.00 (ddd, J = 10.3,
6.8, 2.3 Hz, 1 H), 1.64 (d, J = 10.3 Hz, 1 H), 1.55 (sept, J = 6.9 Hz,
1 H), 1.27 (t, J = 7.9 Hz, 9 H), 1.18 (t, J = 11.6 Hz, 1 H), 1.00 (dq,
J = 15.1, 7.6 Hz, 3 H), 0.89–0.83 (m, 3 H), 0.86 (d, J = 6.9 Hz, 3 H),
0.85 (d, J = 6.9 Hz, 3 H), 0.78 (s, 3 H), 0.75 (s, 3 H), 0.61 (s, 3 H),
0.38 (s, 3 H), 0.03 (s, 3 H), –0.01 (s, 3 H), –0.03 (s, 3 H).
13C NMR (125 MHz, C6D6): d = 190.9, 189.8, 166.4, 134.5 (2 C),
133.6, 133.3, 126.6, 126.2, 94.6, 92.6, 83.0, 79.4, 78.7, 76.8, 69.1,
64.4, 51.3, 50.4, 39.2, 34.7, 34.5, 25.0, 20.6, 20.4, 18.9, 18.8, 9.47,
7.07, 4.02, 3.73, 1.68, –0.17, –0.40.
UV/Vis (MeOH): lmax (log e) = 258 (4.35), 299 (4.22), 402 (3.42),
472 nm (3.09).
UV/Vis (MeOH): lmax (log e) = 281 (4.33), 307 sh (4.12), 340 sh
(3.87), 474 nm (3.32).
53
Red-black solid; mp 184–189 °C (EtOAc–hexanes).
MS (FAB, NBA): m/z (%) = 772 [M]+.
IR (KBr): 3360, 2930, 2855, 1418, 1250, 982, 928, 836, 806, 757
cm–1.
1H NMR (300 MHz, C6D6): d = 7.19 (AA¢m, 2 H), 6.98 (BB¢m, 2
H), 5.05 (d, J = 6.3 Hz, 2 H), 4.86 (s, 5 H), 3.96 (d, J = 6.3 Hz, 2 H),
1.91 (br t, J = 5.9 Hz, 2 H, Htert), 1.28–1.17 (m, 2 H), 0.85–0.67 (m,
4 H), 0.65–0.45 (m, 2 H), 0.36 (s, 18 H).
13C NMR (75 MHz, C6D6): d = 142.3, 128.8, 108.0, 81.0, 71.6, 58.5,
41.2, 32.9, 23.2, 2.03 (one aromatic carbon resonance was obscured
by solvent).
Anal. Calcd for C42H61CoO4Si3: C, 65.25; H, 7.95. Found: C, 65.18;
H, 7.82.
The experiment generating 51 and 52 also gave, as the slower elut-
ing components on column chromatography, the CpCo(cyclobuta-
diene) (33%) and (cyclopentadienone) complexes (Figure 9) (7%)
derived from 38.
MS (EI, 70 eV): m/z (%) = 536 (1, [M]+), 518 (4), 445 (4), 376 (10),
305 (27), 289 (28), 231 (31), 75 (59), 73 (100).
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UV/Vis (MeOH): lmax (log e) = 269 (4.23), 329 sh (3.41), 381
Red needles; mp 191–193 °C (CH2Cl2–MeOH).
(2.93), 428 nm (2.86).
IR (KBr): 2958, 2864, 1659, 1597, 1452, 1400, 1253, 1213, 952,
815, 777, 713 cm–1.
1H NMR (300 MHz, CDCl3): d = 8.05 (AA¢m, 2 H), 7.59 (BB¢m, 2
H), 4.77 (s, 5 H), 1.77 (sept, J = 6.8 Hz, 2 H), 0.94 (s, 6 H), 0.92 (s,
6 H), 0.86 (d, J = 6.8 Hz, 6 H), 0.84 (d, J = 6.8 Hz, 6 H), 0.50 (s, 6
H), 0.28 (s, 6 H).
Anal. Calcd for C29H41CoO2Si2: C, 64.89; H, 7.70. Found: C, 64.94;
H, 7.60.
54
Red-brown powder; mp 183–186 °C (EtOAc–hexanes).
IR (KBr): 3460–3300, 2945, 2858, 1417, 1253, 963, 834, 806, 759,
681, 633 cm–1.
1H NMR (500 MHz, CDCl3): d = 7.38 (AA¢m, 2 H), 7.35 (BB¢m, 2
H), 5.26 (d, J = 6.5 Hz, 2 H), 4.16 (s, 5 H), 3.11 (d, J = 6.5 Hz, 2 H,
exchangeable with D2O), 1.91 (br s, 2 H, Htert), 1.45 (m, 2 H), 1.20–
1.08 (m, 4 H), 1.04 (m, 2 H), 0.28 (s, 18 H).
13C NMR (125 MHz, C6D6): d = 140.0, 128.4, 127.7, 98.5, 80.6,
73.2, 60.5, 41.0, 32.8, 23.1, 2.72.
MS (EI, 70 eV): m/z (%) = 536 (11, [M]+), 463 (43), 305 (53), 231
(49), 136 (48), 121 (56), 105 (47), 91 (48), 73 (100).
13C NMR (75 MHz, CDCl3): d = 186.3, 136.0, 132.5, 126.1, 85.0,
82.7, 78.9, 33.9, 24.6, 21.8, 21.6, 18.9, 18.3, –1.03, –1.10.
MS (EI, 70 eV): m/z (%) = 590 (0.5, [M]+), 505 (85), 435 (76), 421
(95), 361 (58), 360 (50), 73 (95), 43 (100).
UV/Vis (MeOH): lmax (log e) = 275 (4.19), 327 (3.96), 386 (3.28),
470 sh nm (2.67).
Anal. Calcd for C33H47CoO2Si2: C, 67.08; H, 8.02. Found: C, 66.99;
H, 8.00.
Attempted cocyclization of 36 with cyclohexene gave only the Cp-
Co(cyclobutadiene) complex (Figure 12) of 36 (33%).
UV/Vis (MeOH): lmax (log e) = 264 (4.19), 315 sh (3.67), 412
(2.99), 544 nm (2.50).
O
Anal. Calcd for C29H41CoO2Si2: C, 64.89; H, 7.70. Found: C, 64.61;
H, 7.81.
TMS
The crude solution of the cyclization experiment generating 53 and
54 formed a precipitate of a CpCo(cyclopentadienone) complex
(Figure 10) (10%) derived from 39.
SiMe2(CMe2CHMe2)
O
CpCo
Figure 12 CpCo{1-[(2,3-dimethylbutan-2-yl)dimethylsilyl]-2-(tri-
methylsilyl)cyclobuta[b]naphthalene-3,8-dione}
OH
TMS
O
Red-brown powder; mp 111–113 °C (EtOAc–hexanes).
IR (KBr): 2970, 1661, 1600, 1460, 1259, 1214, 958, 821, 718 cm–1.
TMS
OH
CpCo
1H NMR (400 MHz, C6D6): d = 8.19 (m, 2 H), 7.12 (m, 2 H), 4.41
(s, 5 H), 1.69 (sept, J = 6.9 Hz, 1 H), 1.01 (s, 3 H), 0.97 (s, 3 H),
0.91 (d, J = 6.9 Hz, 6 H), 0.63 (s, 3 H), 0.37 (s, 9 H), 0.17 (s, 3 H).
Figure 10 CpCo[4,9-dihydroxy-1,3-bis(trimethylsilyl)-4,9-dihy-
dro-2H-cyclopenta[b]naphthalen-2-one]
13C NMR (100 MHz, C6D6): d = 186.2, 185.8, 136.8, 136.7, 132.5,
132.4, 126.4, 126.3, 82.7, 81.9, 81.5, 79.4, 78.8, 35.0, 24.9, 22.1,
21.7, 19.10, 19.09, 0.75, –1.32, –1.45.
MS (EI, 70 eV): m/z (%) = 520 (0.5, [M]+), 505 (0.8), 435 (100), 361
(26), 73 (57).
Orange-yellow powder; mp 250–253 °C (C6H6).
IR (KBr): 3400–3200, 2950, 2895, 1511, 1438, 1247, 1012, 861,
835, 825, 738 cm–1.
1H NMR (300 MHz, DMSO-d6): d = 7.48 (m, 2 H), 7.34 (m, 2 H),
5.23 (s, 2 H), 4.58 (s, 5 H), 0.32 (s, 18 H).
13C NMR (75 MHz, DMSO-d6): d = 172.3, 137.6, 129.7, 127.7,
98.9, 81.0, 66.2, 64.7, –0.31.
MS (EI, 70 eV): m/z (%) = 482 (45, [M]+), 449 (16), 375 (15), 325
UV/Vis (MeOH): lmax (log e) = 256 sh (4.40), 273 (4.46), 326
(4.27), 386 (3.61), 470 sh nm (3.04).
Anal. Calcd for C28H37CoO2Si2: C, 64.59; H, 7.16. Found: C, 64.78;
H, 7.30.
(14), 133 (26), 75 (41), 73 (100).
55
UV/Vis (MeOH): lmax (log e) = 288 (4.28), 365 (3.40), 428 nm
(3.08).
Dark red solid; mp 198–203 °C (CH2Cl2–MeOH).
IR (KBr): 2950, 1665, 1598, 1333, 1250, 842, 813 cm–1.
Anal. Calcd for C24H31CoO3Si2: C, 59.73; H, 6.47. Found: C, 59.61;
H, 6.45.
1H NMR (400 MHz, C6D6): d = 8.18 (m, 1 H), 8.12 (m, 1 H), 7.07
(m, 2 H), 4.57 (dd, J = 7.0, 4.1 Hz, 1 H), 4.38 (s, 5 H), 3.18 (s, 3 H),
2.77 (dd, J = 8.7, 4.0 Hz, 1 H), 2.65 (ddd, J = 10.6, 8.6, 7.7 Hz, 1
H), 2.54 (ddd, J = 9.7, 7.1, 2.6 Hz, 1 H), 2.39 (ddd, J = 13.8, 7.6,
2.9 Hz, 1 H), 1.56 (sept, J = 6.9 Hz, 1 H), 1.42 (d, J = 9.9 Hz, 1 H),
1.34 (s, 3 H), 1.05 (dd, J = 13.8, 10.7 Hz, 1 H), 0.88 (d, J = 6.9 Hz,
3 H), 0.86 (d, J = 6.9 Hz, 3 H), 0.76 (s, 3 H), 0.74 (s, 3 H), 0.63 (s,
3 H), 0.44 (br s, 9 H), 0.35 (s, 3 H), 0.07 (s, 3 H), 0.06 (s, 3 H), –
0.01 (s, 3 H).
Attempted cocyclization of 35 with cyclohexene gave only the Cp-
Co(cyclobutadiene) complex (Figure 11) of 35 (54%).
O
SiMe2(CMe2CHMe2)
SiMe2(CMe2CHMe2)
13C NMR (100 MHz, C6D6): d = 191.5, 191.2, 135.1, 135.0, 134.2,
133.9, 127.0, 126.9, 104.9, 95.6, 92.2, 83.2, 82.9, 77.4, 68.7, 66.2,
53.3, 48.3, 47.6, 35.9, 35.7, 35.2, 25.7, 21.2, 21.0, 19.4, 19.2, 15.0,
4.32, 4.20, 3.16, 2.17, 0.22, 0.08.
O
CpCo
Figure 11 CpCo[1,2-bis((2,3-dimethylbutan-2-yl)dimethylsi-
lyl)cyclobuta[b]naphthalene-3,8-dione]
MS (FAB, HEDS): m/z (%) = 762 [M]+.
Synthesis 2010, No. 13, 2179–2200 © Thieme Stuttgart · New York

PAPER
Cobalt-Mediated Cycloadditions
2195
Anal. Calcd for C40H59CoO5Si3: C, 62.96; H, 7.79. Found: C, 62.86;
H, 8.18.
1.16 (m, 1 H), 0.99–0.86 (m, 2 H), 0.49 (br s, 9 H), 0.40 (s, 9 H) (the
OH signal was not observed).
13C NMR (125 MHz, C6D6): d = 191.1, 189.7, 159.2, 137.2, 133.8,
124.7, 118.5, 117.0, 98.9, 91.1, 82.7, 70.1, 68.3, 66.2, 56.0, 52.7,
34.8, 33.3, 28.8, 19.6, 3.58, 2.08.
56
Colorless solid; mp 96–99 °C (CH2Cl2–PE).
IR (KBr): 2975, 2165, 1778, 1669, 1648, 1477, 1290, 1261, 1237,
1030, 858, 763 cm–1.
1H NMR (300 MHz, CDCl3): d = 7.74 (dd, J = 7.7, 0.6 Hz, 1 H),
7.49 (t, J = 8.0 Hz, 1 H), 7.18 (d, J = 8.4 Hz, 1 H), 3.85 (s, 3 H),
0.28 (s, 9 H), 0.19 (s, 9 H).
13C NMR (75 MHz, CDCl3): d = 179.4, 176.4, 156.8, 135.9, 130.7,
130.1, 123.9, 117.0, 102.3, 101.8, 100.6, 98.3, 56.4, –0.70, –0.76.
MS (FAB, NBA): m/z (%) = 578 [M]+.
HRMS-FAB (PEG): m/z [M]+ calcd for C30H39CoO4Si2: 579.1797;
found: 579.1800.
60
Red powder; 173–174.5 °C (EtOAc–hexanes).
IR (KBr): 2955, 1723, 1678, 1593, 1280, 857, 828, 724 cm–1.
1H NMR (300 MHz, C6D6): d = 8.23 (m, 2 H), 7.84 (dd, J = 7.4, 1.0
Hz, 1 H), 7.12–7.00 (m, 4 H), 6.57 (dd, J = 8.4, 0.6 Hz, 1 H), 6.02
(br s, 1 H), 4.39 (s, 5 H), 3.33 (s, 3 H), 2.81 (br d, J = 7.2 Hz, 1 H,
MS (EI, 70 eV): m/z (%) = 356 (32, [M]+), 341 (50), 283 (29), 267
(26), 254 (31), 165 (24), 134 (27), 97 (25), 73 (100).
Anal. Calcd for C19H24O3Si2: C, 64.00; H, 6.78. Found: C, 64.17; H,
6.59.
Htert), 2.34 (ddd, J = 12.0, 7.4, 4.8 Hz, 1 H, Htert), 1.88 (m, 1 H), 1.63
(m, 1 H), 1.45 (m, 1 H), 1.22 (m, 1 H), 0.97 (m, 1 H), 0.59 (br s, 9
H), 0.50 (m, 1 H), 0.45 (s, 9 H).
57
Red brown solid; mp 172–175 °C (EtOAc–hexanes).
IR (KBr): 2935, 2858, 1663, 1586, 1283, 1252, 850, 813 cm–1.
1H NMR (300 MHz, CDCl3): d = 7.71 (dd, J = 7.7, 0.8 Hz, 1 H),
7.60 (t, J = 7.7 Hz, 1 H), 7.25 (d, J = 7.7 Hz, 1 H), 4.55 (s, 5 H),
3.97 (s, 3 H), 2.18–2.05 (m, 2 H, Htert), 1.55–1.45 (m, 2 H), 1.20–
1.00 (m, 6 H), 0.27 (s, 9 H), 0.24 (s, 9 H).
13C NMR (75 MHz, CDCl3): d = 191.3, 188.8, 165.2, 159.4, 137.5,
133.7, 132.8, 131.5, 130.1, 125.2, 118.6, 117.4, 95.2, 94.7, 82.7,
73.1, 68.9, 63.1, 56.1, 50.8, 34.7, 33.5, 25.7, 20.5, 3.41, 2.09 (one
aromatic carbon resonance was obscured by solvent).
MS (EI, 70 eV): m/z (%) = 436 (3, [M – (CpCo + C6H5CO2H]+), 179
(44), 147 (49), 89 (65), 73 (33), 59 (77).
13C NMR (75 MHz, CDCl3): d = 191.6, 190.0, 158.6, 136.8, 133.7,
123.4, 118.1, 116.8, 96.1, 92.1, 82.4, 70.0, 68.6, 56.6, 41.32, 41.31,
32.8, 32.7, 23.4, 23.2, 2.48, 2.38.
MS (EI, 70 eV): m/z (%) = 562 (3, [M]+), 438 (3), 408 (5), 349 (9),
309 (26), 307 (16), 147 (20), 89 (100), 75 (26), 73 (27), 59 (74).
MS (FAB, sulfolane): m/z (%) = 683 [MH]+.
UV/Vis (MeOH): lmax (log e) = 273 (4.20), 355 (3.80), 462 nm
(3.25).
Anal. Calcd for C37H43CoO5Si2: C, 65.08; H, 6.35. Found: C, 64.97;
H, 6.32.
UV/Vis (MeOH): lmax (log e) = 276 (4.27), 313 sh (4.01), 354
(3.92), 470 nm (3.35).
61
Red powder; mp 172–174 °C (EtOAc–hexanes).
IR (KBr): 2960, 1727, 1671, 1596, 1287, 995, 858, 827, 730 cm–1.
Anal. Calcd for C30H39CoO3Si2: C, 64.03; H, 6.99. Found: C, 64.20;
H, 6.78.
1H NMR (300 MHz, C6D6): d = 8.23 (m, 2 H), 7.94 (d, J = 7.7 Hz,
1 H), 7.13–7.00 (m, 4 H), 6.54 (d, J = 8.4 Hz, 1 H), 6.02 (br s, 1 H),
4.37 (s, 5 H), 3.29 (s, 3 H), 2.86 (br d, J = 7.5 Hz, 1 H, Htert), 2.38
(ddd, J = 11.8, 7.2, 4.7 Hz, 1 H, Htert), 1.85 (m, 1 H), 1.62 (m, 1 H),
1.51 (m, 1 H), 1.35 (m, 1 H), 0.96 (m, 1 H), 0.65 (br s, 9 H), 0.50
(m, 1 H), 0.43 (s, 9 H).
13C NMR (125 MHz, C6D6): d = 190.9, 189.7, 165.2, 159.1, 137.1,
133.9, 132.8, 131.5, 129.8, 128.5, 124.0, 118.5, 117.1, 99.6, 90.9,
82.8, 73.1, 67.6, 64.6, 56.0, 50.8, 34.8, 33.2, 25.6, 20.5, 3.71 (br),
1.90.
58
Reddish black solid; mp 164–166 °C (acetone–hexanes).
IR (KBr): 3540–3390, 2945, 1665, 1590, 1477, 1287, 855, 819 cm–1.
1H NMR (500 MHz, C6D6): d = 7.86 (dd, J = 7.6, 0.8 Hz, 1 H), 7.06
(t, J = 8.0 Hz, 1 H), 6.56 (d, J = 8.3 Hz, 1 H), 4.45 (s, 5 H), 4.03 (br
s, 1 H), 3.32 (s, 3 H), 2.47 (d, J = 7.5 Hz, 1 H, Htert), 2.27 (ddd,
J = 11.7, 7.5, 4.8 Hz, 1 H, Htert), 1.74 (m, 1 H), 1.42–1.30 (m, 2 H),
1.16–1.04 (m, 2 H), 0.90 (m, 1 H), 0.69 (d, J = 3.5 Hz, 1 H), 0.45
(br s, 9 H), 0.42 (s, 9 H).
13C NMR (125 MHz, C6D6): d = 191.3, 189.1, 159.4, 137.4, 133.6,
124.7, 118.6, 117.4, 95.0, 94.6, 82.6, 70.1, 69.4, 64.7, 56.1, 52.6,
34.6, 33.6, 28.8, 19.4, 3.33, 2.19.
MS (EI, 70 eV): m/z (%) = 436 (4, [M – (CpCo + C6H5CO2H]+), 179
(62), 135 (59), 105 (66), 89 (64), 77 (70), 73 (46), 59 (84).
UV/Vis (MeOH): lmax (log e) = 274 (4.28), 354 (3.88), 460 nm
(3.34).
MS (FAB, TG-G): m/z (%) = 578 [M]+.
UV/Vis (MeOH): lmax (log e) = 275 (4.32), 356 (3.96), 468 nm
(3.40).
Anal. Calcd for C37H43CoO5Si2: C, 65.08; H, 6.35. Found: C, 64.87;
H, 6.33.
Anal. Calcd for C30H39CoO4Si2: C, 62.26; H, 6.79. Found: C, 61.89;
H, 7.05.
O
TMS
59
Reddish brown foam.
IR (KBr): 3435, 2945, 1662, 1586, 1279, 1248, 840 cm–1.
1H NMR (500 MHz, C6D6): d = 7.93 (dd, J = 7.6, 0.9 Hz, 1 H), 7.10
(t, J = 8.0 Hz, 1 H), 6.56 (d, J = 8.2 Hz, 1 H), 4.44 (s, 5 H), 4.06 (br
s, 1 H), 3.31 (s, 3 H), 2.52 (d, J = 7.3 Hz, 1 H, Htert), 2.27 (ddd,
J = 11.7, 7.3, 4.8 Hz, 1 H, Htert), 1.72 (m, 1 H), 1.42–1.26 (m, 2 H),
TMS
OMe
O
CpCo
Figure 13 CpCo[4-methoxy-1,2-bis(trimethylsilyl)cyclobu-
ta[b]naphthalene-3,8-dione]
Synthesis 2010, No. 13, 2179–2200 © Thieme Stuttgart · New York

2196
C. Aubert et al.
PAPER
Attempted cocyclization of 56 with 2-cyclohexenyl benzoate in
THF gave only the CpCo(cyclobutadiene) complex (Figure 13) of
56 (12%).
MS (FAB, sulfolane): m/z (%) = 761 [MH]+.
UV/Vis (MeOH): lmax (log e) = 276 (4.23), 305 sh (4.01), 357
(3.83), 464 nm (3.29).
Red-brown powder; mp 126–127 °C (EtOAc–hexanes).
Anal. Calcd for C40H57CoO5Si3: C, 63.13; H, 7.55. Found: C, 63.31;
H, 7.80.
IR (KBr): 2960, 1662, 1586, 1465, 1272, 1187, 975, 840, 818, 753
cm–1.
1H NMR (400 MHz, C6D6): d = 8.02 (dd, J = 7.7, 1.1 Hz, 1 H), 7.05
(t, J = 8.0 Hz, 1 H), 6.57 (d, J = 8.2 Hz, 1 H), 4.47 (s, 5 H), 3.36 (s,
3 H), 0.34 (s, 18 H).
The experiment generating 63 and 62 (in order of elution on column
chromatography) also gave the CpCo(cyclopentadienone) complex
(Figure 14) (9%) derived from 56.
13C NMR (100 MHz, CDCl3): d = 186.2, 185.6, 160.3, 139.6, 133.1,
125.0, 119.3, 117.8, 81.3, 80.1, 79.2, 78.3, 77.4, 56.1, 0.64, 0.57.
O
TMS
MS (EI, 70 eV): m/z (%) = 480 (69, [M]+), 465 (12), 145 (17), 75
O
(57), 73 (100).
TMS
HRMS-EI: m/z [M]+ calcd for C24H29CoO3Si2: 480.0987; found:
480.1006.
OMe
O
CpCo
Figure 14 CpCo[5-methoxy-1,3-bis(trimethylsilyl)-1H-cyclopen-
ta[b]naphthalene-2,4,9-trione]
UV/Vis (MeOH): lmax (log e) = 274 (4.35), 328 (4.13), 364 sh
(3.90), 394 sh (3.79), 466 sh nm (3.15).
Anal. Calcd for C24H29CoO3Si2: C, 59.98; H, 6.08. Found: C, 60.42;
H, 6.05.
Red powder; mp 201–203 °C (EtOAc–hexanes).
IR (KBr): 2960, 2904, 1679, 1611, 1592, 1287, 1248, 1199, 1013,
832, 736 cm–1.
1H NMR (300 MHz, C6D6): d = 7.90 (d, J = 7.5 Hz, 1 H), 7.12 (t,
J = 8.1 Hz, 1 H), 6.62 (d, J = 8.1 Hz, 1 H), 4.39 (s, 5 H), 3.35 (s, 3
H), 0.61 (s, 18 H).
63
Red brown powder; mp 178–183 °C (EtOAc–hexanes); [a]D20 +230
(c 3.2 × 10–4, CHCl3).
IR (KBr): 2962, 1674, 1593, 1278, 1257, 1004, 986, 843, 818 cm–1.
1H NMR (400 MHz, C6D6): d = 7.80 (dd, J = 7.6, 0.8 Hz, 1 H), 7.02
(t, J = 8.0 Hz, 1 H), 6.52 (d, J = 8.2 Hz, 1 H), 4.77 (dd, J = 6.7, 3.7
Hz, 1 H), 4.46 (s, 1 H), 4.41 (s, 5 H), 4.25 (d, J = 1.0 Hz, 1 H), 3.28
(s, 3 H), 2.71 (dd, J = 8.4, 3.6 Hz, 1 H), 2.64 (dt, J = 10.5, 7.1 Hz,
1 H), 2.41 (ddd, J = 12.2, 6.9, 2.8 Hz, 1 H), 2.00 (ddd, J = 9.7, 7.0,
2.6 Hz, 1 H), 1.65 (d, J = 10.2 Hz, 1 H), 1.56 (sept, J = 6.9 Hz, 1
H), 1.21 (dd, J = 12.1, 10.7 Hz, 1 H), 0.861 (d, J = 6.9 Hz, 3 H),
0.858 (d, J = 6.9 Hz, 3 H), 0.77 (s, 3 H), 0.76 (s, 3 H), 0.63 (s, 3 H),
0.41 (s, 9 H), 0.37 (s, 3 H), 0.05 (s, 3 H), 0.02 (s, 3 H), –0.02 (s, 3 H).
13C NMR (100 MHz, CDCl3): d = 191.4, 189.0, 166.6, 159.4, 137.0,
133.8, 123.5, 118.5, 117.5, 95.0, 94.3, 82.6, 79.4, 78.8, 76.6, 66.5,
62.1, 56.0, 50.8, 50.6, 39.0, 34.6, 34.5, 25.0, 20.5, 20.4, 18.84,
18.79, 4.05, 3.35, 2.34, 1.36, –0.04, –0.37.
13C NMR (75 MHz, CDCl3): d = 187.7, 185.6, 175.3, 160.2, 137.6,
134.3, 123.4, 119.2, 117.9, 94.7, 90.7, 82.2, 70.9, 69.6, 56.1, 0.51,
0.48.
MS (EI, 70 eV): m/z (%) = 508 (29, [M]+), 493 (10), 449 (13), 138
(11), 123 (21), 95 (21), 73 (100).
UV/Vis (MeOH): lmax (log e) = 255 (4.30), 296 (4.22), 381 (3.80),
462 nm (3.14).
Anal. Calcd for C25H29CoO4Si2: C, 59.04; H, 5.75. Found: C, 59.37;
H, 5.83.
47b
TMS-68a and TMS-68b: To a solution of the mixture of diastere-
omers 68 (13.5 g, 51 mmol)18 in anhyd THF (80 mL) under N2 at r.t.
was slowly added Et3N (14 mL, 2 equiv), followed by TMSCl (9
mL, 1.3 equiv), and the mixture was stirred for 12 h at r.t. Aqueous
workup resulted in the two diastereomers of TMS-protected 68
(16.1 g, 95%), separated by column chromatography (silica gel)
(Figure 15).
MS (FAB, sulfolane): m/z (%) = 761 [MH]+.
UV/Vis (MeOH): lmax (log e) = 277 (4.32), 306 sh (4.09), 356
(3.91), 466 nm (3.37).
Anal. Calcd for C40H57CoO5Si3: C, 63.13; H, 7.55. Found: C, 62.97;
H, 7.52.
62
OTMS
OTMS
O
O
20
O
O
Red brown solid; mp 68–72 °C (EtOAc–hexanes); [a]D +340 (c
C6H5
C6H5
1.8 × 10–4, CHCl3).
O
O
IR (KBr): 2960, 1670, 1590, 1280, 1254, 979, 839, 812 cm–1.
O
O
TMS-68a
TMS-68b
1H NMR (400 MHz, C6D6): d = 7.87 (dd, J = 7.7, 1.0 Hz, 1 H), 7.04
(t, J = 7.8 Hz, 1 H), 6.49 (d, J = 7.7 Hz, 1 H), 4.77 (dd, J = 6.7, 3.8
Hz, 1 H), 4.46 (s, 1 H), 4.39 (s, 5 H), 4.25 (d, J = 1.1 Hz, 1 H), 3.26
(s, 3 H), 2.74 (dd, J = 8.3, 3.7 Hz, 1 H), 2.62 (dt, J = 15.4, 7.1 Hz,
1 H), 2.39 (ddd, J = 12.1, 7.0, 2.9 Hz, 1 H), 2.01 (ddd, J = 10.1, 7.0,
2.7 Hz, 1 H), 1.71 (d, J = 10.3 Hz, 1 H), 1.56 (sept, J = 6.9 Hz, 1
H), 1.23 (dd, J = 12.0, 9.3 Hz, 1 H), 0.861 (d, J = 6.9 Hz, 3 H),
0.857 (d, J = 6.9 Hz, 3 H), 0.78 (s, 3 H), 0.76 (s, 3 H), 0.66 (s, 3 H),
0.39 (s, 9 H), 0.35 (s, 3 H), 0.16 (s, 3 H), 0.01 (s, 3 H), 0.00 (s, 3 H).
13C NMR (100 MHz, CDCl3): d = 191.1, 189.7, 166.6, 159.2, 137.0,
134.0, 123.5, 118.6, 117.1, 98.8, 91.0, 82.6, 79.4, 78.9, 76.6, 65.4,
63.6, 55.9, 50.74, 50.69, 39.0, 34.44, 34.41, 25.0, 20.5, 20.4, 18.84,
18.77, 4.62, 3.53, 2.22, 1.35, –0.08, –0.36.
Figure 15 TMS-68a and TMS-68b
TMS-68a: colorless oil.
IR (KBr): 3067, 3031, 3004, 2959, 2907, 1795, 1457, 1408, 1254,
1192, 1086, 1066, 971, 890, 839 cm–1.
1H NMR (400 MHz, CDCl3): d = 7.49 (m, 2 H), 7.42 (m, 3 H), 5.76
(s, 1 H), 4.76 (dd, J = 6.0, 2.4 Hz, 1 H), 4.52 (td, J = 7.6, 2.4 Hz, 1
H), 4.36 (dt, J = 6.8, 1.2 Hz, 1 H), 2.72 (d, J = 11.6 Hz, 1 H), 2.55
(ddd, J = 14.8, 7.6, 2.0 Hz, 1 H), 2.34 (ddt, J = 11.6, 6.4, 1.8 Hz, 1
H), 2.30 (dd, J = 14.8, 2.4 Hz, 1 H), 0.20 (s, 9 H).
Synthesis 2010, No. 13, 2179–2200 © Thieme Stuttgart · New York

PAPER
Cobalt-Mediated Cycloadditions
2197
13C NMR (100 MHz, CDCl3): d = 177.4, 135.8, 130.0, 128.8, 126.8,
Hz, 1 H), 4.44 (br s, 1 H), 4.35 (s, 5 H), 4.22 (d, J = 1.0 Hz, 1 H),
3.22 (s, 3 H), 2.71 (dd, J = 8.5, 3.5 Hz, 1 H), 2.58 (m, 1 H), 2.38
(ddd, J = 12.0, 7.0, 3.0 Hz, 1 H), 2.02 (ddd, J = 10.0, 7.0, 3.0 Hz, 1
H), 1.68 (d, J = 10.5 Hz, 1 H), 1.19 (m, 1 H), 0.62 (s, 3 H), 0.35 (br
s, 9 H), 0.31 (s, 3 H), 0.13 (s, 3 H), 0.00 (s, 9 H).
13C NMR (125 MHz, C6D6): d = 191.3, 190.0, 166.9, 159.6, 137.4,
134.4, 123.9, 119.0, 117.5, 99.1, 91.5, 83.1, 79.9, 79.2, 77.0, 65.9,
63.9, 56.3, 51.12, 51.09, 39.5, 34.7, 4.97, 3.97, 2.63, 2.52, 1.69.
103.9, 74.9, 73.5, 73.3, 73.0, 39.1, 35.7, 2.10.
HRMS-EI: m/z [M]+ calcd for C17H22O5Si: 334.1236; found:
334.1213.
TMS-68b: Colorless oil.
1H NMR (400 MHz, CDCl3): d = 7.40 (m, 5 H), 6.23 (s, 1 H), 4.84
(dd, J = 8.0, 4.4 Hz, 1 H), 4.56 (dt, J = 11.2, 7.6 Hz, 1 H), 4.35 (ddd,
J = 8.0, 4.0, 1.2 Hz, 1 H), 2.56 (d, J = 15.6 Hz, 1 H), 2.52 (ddd,
J = 18.8, 10.8, 3.6 Hz, 1 H), 2.44 (dddd, J = 15.6, 8.0, 3.2, 1.6 Hz,
1 H), 2.10 (dd, J = 18.8, 7.2 Hz, 1 H), 0.23 (s, 9 H).
HRMS-FAB (TG-G): m/z [M]+ calcd for C35H47CoO5Si3: 690.2063;
found: 690.2067.
UV/Vis (CH2Cl2): lmax (log e) = 230 (4.59), 277 (4.63), 352 (4.21),
466 nm (3.58).
13C NMR (100 MHz, CDCl3): d = 176.7, 137.9, 129.5, 128.7, 126.1,
103.9, 74.9, 73.4, 72.8, 72.4, 39.1, 37.1, 2.12.
Methylene Derivative of TMS-68a: A 250 mL three-necked round-
bottomed flask was loaded with Zn dust (5.60 g, 85.6 mmol),
purged with dry N2, charged with THF (50 mL) and TMEDA (22
mL), and cooled in an ice-water bath. TiCl4 (7.6 g, 4 equiv) in
CH2Cl2 (30 mL) was added cautiously and dissolved over 5 min.
The cooling bath was removed and the light green solution stirred
for 20 min. CH2Br2 (3.2 mL) was added via syringe and a solution
of TMS-68a (3.26 g, 9.75 mmol) in THF (15 mL) injected slowly.
The green mixture turned turquoise and gradually darkened after
about 1 h. Workup with aq K2CO3 was followed by filtration
through activated basic Al2O3 (50 g) and column chromatography
(silica gel, hexane–Et2O, 100:0 to 95:5) to furnish the methylene de-
rivative of TMS-68a (1.75 g, 54%); colorless oil.
65
Red solid.
IR (neat): 3070, 2956, 2917, 2849, 1666, 1585, 1470, 1446, 1304
1278, 1251, 1164, 1076, 998, 982, 842, 810, 757 cm–1.
1H NMR (500 MHz, C6D6): d = 7.76 (dd, J = 7.5, 1.0 Hz, 1 H), 6.98
(t, J = 8.0 Hz, 1 H), 6.48 (d, J = 7.5 Hz, 1 H), 4.73 (dd, J = 6.5, 4.0
Hz, 1 H), 4.44 (br s, 1 H), 4.37 (s, 5 H), 4.22 (br d, J = 1.0 Hz, 1 H),
3.25 (s, 3 H), 2.68 (dd, J = 8.5, 3.5 Hz, 1 H), 2.59 (m, 1 H), 2.40
(ddd, J = 12.5, 7.0, 3.0 Hz, 1 H), 2.02 (ddd, J = 10.0, 6.5, 2.5 Hz, 1
H), 1.62 (d, J = 10.0 Hz, 1 H), 1.21 (m, 1 H), 0.58 (s, 3 H), 0.36 (br
s, 9 H), 0.34 (s, 3 H), 0.02 (s, 3 H), 0.00 (s, 9 H).
13C NMR (125 MHz, C6D6): d = 191.6, 189.3, 166.9, 159.8, 137.4,
134.1, 123.9, 118.9, 117.9, 95.5, 94.6, 83.0, 79.9, 79.0, 77.0, 67.0,
62.4, 56.4, 51.2, 50.9, 39.5, 34.9, 4.39, 3.78, 2.75, 2.54, 1.77.
IR (KBr): 3117, 3082, 2962, 2925, 2892, 1686, 1655, 1459, 1404,
1250, 1175, 1083, 1065, 989, 833, 761 cm–1.
1H NMR (400 MHz, CDCl3): d = 7.50 (m, 2 H), 7.41 (m, 3 H), 5.80
(s, 1 H), 4.68 (dd, J = 6.0, 2.8 Hz, 1 H), 4.77 (ddd, J = 8.4, 7.2, 4.8
Hz, 1 H), 4.25 (dd, J = 6.4, 2.8 Hz, 1 H), 4.19 (br s, 1 H), 4.10 (br s,
1 H), 2.42 (m, 1 H), 2.39 (d, J = 10.8 Hz, 1 H), 2.18 (dd, J = 13.6,
4.8 Hz, 1 H), 2.16 (m, 1 H), 0.18 (s, 9 H).
HRMS-FAB (TG-G): m/z [M]+ calcd for C35H47CoO5Si3: 690.2063;
found: 690.2074.
UV/Vis (CH2Cl2): lmax (log e) = 230 (4.76), 278 (4.59), 309 (4.34),
355 (4.16), 467 nm (3.57).
13C NMR (100 MHz, CDCl3): d = 166.4, 136.7, 129.8, 128.7, 126.8,
66
104.4, 78.7, 76.5, 76.4, 75.2, 73.6, 44.9, 36.9, 2.26.
Red solid. Crystals suitable for X-ray crystallography were grown
as purple plates over several days by slow cooling of a hexanes–
CH2Cl2 solution to 5 °C.
HRMS-EI: m/z [M]+ calcd for C18H24O4Si: 332.1443; found:
332.1443.
1H NMR (500 MHz, C6D6): d = 7.82 (dd, J = 8.0, 1.0 Hz, 1 H), 7.12
(1 H, partly masked by solvent), 6.53 (d, J = 8.5 Hz, 1 H), 4.65 (dd,
J = 7.0, 4.0 Hz, 1 H), 4.40 (br s, 1 H), 4.30 (s, 5 H), 4.13 (d, J = 1.5
Hz, 1 H), 3.30 (s, 3 H), 2.64 (dd, J = 8.0, 3.5 Hz, 1 H), 2.50 (dt,
J = 11.0, 7.0 Hz, 1 H), 2.10 (ddd, J = 12.0, 7.0, 3.0 Hz, 1 H), 1.81
(br s, 1 H), 1.68 (ddd, J = 10.0, 7.0, 3.0 Hz, 1 H), 1.42 (d, J = 10.5
Hz, 1 H), 0.84 (m, 1 H), 0.56 (s, 3 H), 0.30 (s, 9 H), 0.27 (s, 3 H),
0.08 (s, 3 H).
13C NMR (125 MHz, C6D6): d = 190.9, 190.1, 166.8, 159.4, 137.1,
134.6, 123.7, 119.0, 117.3, 98.7, 91.3, 83.0, 79.2, 77.5, 76.4, 65.7,
64.1, 56.3, 51.1, 49.0, 39.8, 34.6, 4.93, 4.02, 2.66, 1.71.
HRMS-FAB (TG-G): m/z [M]+ calcd for C32H39CoO5Si2: 618.1668;
found: 618.1657.
47b: To a solution of the preceding methylene derivative (5.70 g, 17
mmol) in anhyd THF (150 mL) at –78 °C was added BuLi (2.50 M
in hexanes, 14 mL, 2.06 equiv). The mixture was allowed to warm
to –20 to –10 °C for 10 h and worked up with H2O to give 1.4 g
(55%, based on 1.7 g recovered starting material) of 47b; colorless
oil.
IR (neat): 3118, 3041, 2958, 2898, 1677, 1638, 1426, 1380, 1338,
1308, 1252, 1188, 1162, 1096, 998, 902, 878, 842, 752 cm–1.
1H NMR (400 MHz, CDCl3): d = 6.03 (m, 1 H), 5.86 (m, 1 H), 4.59
(td, J = 5.2, 1.2 Hz, 1 H), 4.21 (t, J = 1.6 Hz, 1 H), 4.12 (d, J = 1.6
Hz, 1 H), 2.61 (dt, J = 17.2, 2.8 Hz, 1 H), 2.46 (ddt, J = 17.2, 4.0,
1.6 Hz, 1 H), 2.40 (dd, J = 10.0, 5.6 Hz, 1 H), 2.02 (d, J = 9.6 Hz, 1
H), 0.17 (s, 9 H).
13C NMR (100 MHz, CDCl3): d = 167.9, 131.5, 128.8, 79.5, 78.7,
73.4, 44.5, 42.4, 2.25.
67
Red solid. Crystals suitable for X-ray crystallography were grown
as purple plates over several days by slow cooling of a hexanes–
CH2Cl2 solution to 5 °C.
MS (EI, 70 eV): m/z (%) = 210 (5, [M]+), 195 (9), 167 (20), 151
(26), 115 (20), 105 (11), 73 (100).
1H NMR (500 MHz, C6D6): d = 7.79 (dd, J = 7.5, 1.0 Hz, 1 H), 7.03
(t, J = 8 Hz, 1 H), 6.53 (d, J = 8.0 Hz, 1 H), 4.64 (dd, J = 6.5, 4.0
Hz, 1 H), 4.35 (br s, 6 H), 4.03 (d, J = 1.5 Hz, 1 H), 3.28 (s, 3 H),
2.61 (dd, J = 8.5, 4.0 Hz, 1 H), 2.51 (dt, J = 11.0, 7.0 Hz, 1 H), 2.13
(ddd, J = 9.0, 7.0, 3.0 Hz, 1 H), 1.52 (m, 1 H), 1.27 (d, J = 10.5 Hz,
1 H), 0.86 (d, J = 11.0 Hz, 1 H), 0.52 (s, 3 H), 0.34 (s, 9 H), 0.30 (s,
3 H), 0.00 (s, 3 H) (OH signal could not be located).
64
Red solid.
IR (neat): 3084, 2956, 2923, 2855, 1666, 1586, 1470, 1446, 1316,
1297, 1277, 1251, 1208, 1163, 1050, 999, 842, 810, 756 cm–1.
1H NMR (500 MHz, C6D6): d = 7.84 (dd, J = 8.0, 1.0 Hz, 1 H), 7.00
(t, J = 8.0 Hz, 1 H), 6.45 (d, J = 8.5 Hz, 1 H), 4.73 (dd, J = 6.5, 3.5
Synthesis 2010, No. 13, 2179–2200 © Thieme Stuttgart · New York

2198
C. Aubert et al.
PAPER
IR (KBr): 3490, 3010, 2935, 1485, 1291, 1009, 878, 800 cm–1.
1H NMR (300 MHz, C6D6): d = 7.03 (BB¢m, 2 H), 5.43 (d, J = 6.1
Hz, 2 H), 3.32 (d, J = 6.0 Hz, 2 H), 2.48 (m, 2 H), 1.57 (m, 2 H),
1.35–1.08 (m, 6 H), 0.40 (s, 18 H) (the AA¢ part of the aromatic pro-
ton signals was masked by solvent).
13C NMR (125 MHz, C6D6): d = 191.3, 189.2, 166.8, 159.8, 137.5,
134.1, 123.8, 118.9, 117.9, 95.2, 94.4, 83.0, 78.9, 77.5, 76.4, 66.8,
62.4, 56.4, 53.6, 51.1, 39.6, 34.7, 4.32, 3.83, 2.76, 1.78.
HRMS-FAB (NBA): m/z [M]+ calcd for C32H39CoO5Si2: 618.1668;
found: 618.1651.
13C NMR (75 MHz, CDCl3): d = 143.8, 143.0, 140.5, 72.7, 40.1,
28.0, 24.8, 2.89 (two sp2 carbon signals were either masked by sol-
vent or not observable).
MS (EI, 70 eV): m/z (%) = 412 (1, [M]+), 376 (36), 304 (31), 232
(31), 147 (52), 107 (45), 78 (87), 77 (64), 75 (81), 73 (100).
69
Unstable colorless oil.
IR (film): 2940, 2868, 1455, 1438, 831, 814 cm–1.
1H NMR (300 MHz, CDCl3): d = 5.25 (br t, J = 2.0 Hz, 2 H), 2.53
(br s, 2 H), 2.25–2.11 (m, 4 H), 1.92–1.80 (m, 2 H), 1.58–1.49 (m,
4 H), 1.49–1.32 (m, 4 H).
Anal. Calcd for C24H36O2Si2: C, 69.85; H, 8.79. Found: C, 69.98; H,
8.63.
13C NMR (75 MHz, CDCl3): d = 131.7, 124.5, 37.8, 34.1, 30.6,
24.3, 23.2.
75
Colorless solid; mp 172–178 °C (EtOAc–hexanes).
70
IR (KBr): 3390, 2925, 1440, 1250, 967, 838, 754 cm–1.
Unstable colorless oil.
1H NMR (300 MHz, CDCl3): d = 5.46 (br s, 2 H), 3.88 (br s, 2 H),
2.32 (m, 4 H), 1.60 (m, 4 H).
13C NMR (75 MHz, CDCl3): d = 172.5, 136.8, 111.9, 41.3, 29.8,
22.7.
MS (EI, 70 eV): m/z (%) = 204 (23, [M]+), 132 (54), 104 (100), 91
(37).
1H NMR (400 MHz, C6D6): d = 7.04 (BB¢m, 2 H), 5.48 (s, 2 H),
4.45 (br s, 2 H), 2.35 (m, 2 H), 1.95 (m, 2 H), 1.53 (m, 2 H), 1.45–
1.28 (m, 4 H), 0.32 (s, 18 H) (the AA¢ part of the aromatic proton
signals was masked by solvent).
13C NMR (100 MHz, C6D6): d = 145.0 (br), 142.5 (br), 140.2, 128.4,
72.4, 40.2, 28.1, 24.7, 2.40 (one sp2 carbon signal was masked by
solvent).
MS (EI, 70 eV): m/z (%) = 412 (5, [M]+), 321 (9), 305 (7), 232 (79),
75 (76), 73 (100).
71
Unstable colorless oil.
Anal. Calcd for C24H36O2Si2: C, 69.85; H, 8.79. Found: C, 69.24; H,
8.60.
1H NMR (500 MHz, C6D6): d = 5.10 (s, 2 H), 2.41 (s, 2 H), 2.13 (s,
4 H), 1.96 (s, 2 H), 1.91 (dt, J = 9.4, 1.8 Hz, 1 H), 1.42 (m, 6 H),
1.22 (m, 2 H), 1.17 (dt, J = 9.4, 1.3 Hz, 1 H).
13C NMR (75 MHz, C6D6): d = 132.1 (C), 123.1 (CH), 46.2 (CH),
43.9 (CH), 34.9 (CH2), 30.5 (CH2), 30.2 (CH2), 23.8 (CH2).
76
Pale yellow solid; mp 213–218 °C (CH2Cl2–Et2O).
IR (KBr): 2935, 1712, 1670, 1587, 1308, 1274, 1248, 986, 837, 718
cm–1.
72
1H NMR (400 MHz, C6D6): d = 8.21 (dd, J = 8.0, 1.5 Hz, 2 H), 7.90
(dd, J = 7.8, 1.0 Hz, 1 H), 7.08 (m, 3 H), 6.99 (t, J = 8.0 Hz, 1 H),
6.44 (d, J = 7.9 Hz, 1 H), 6.26 (br s,1 H), 3.29 (m, 1 H), 3.23 (s, 3
H), 2.95 (m, 1 H), 1.88–1.72 (m, 2 H), 1.60 (m, 1 H), 1.47–1.24 (m,
3 H), 0.53 (s, 9 H), 0.47 (s, 9 H).
Colorless oil.
IR (film): 2925, 2855, 1445, 1250, 840 cm–1.
1H NMR (500 MHz, C6D6): d = 2.41 (m, 6 H), 1.74 (m, 2 H), 1.57
(m, 6 H), 1.42 (m, 4 H), 0.33 (s, 18 H).
13C NMR (125 MHz, C6D6): d = 147.2, 134.9, 40.0, 31.1, 28.6,
13C NMR (100 MHz, C6D6): d = 186.2, 183.1 (2 C), 165.2, 163.2,
159.5, 137.7, 134.0, 132.9, 131.3, 129.9, 128.6, 125.3, 119.8, 117.2,
71.8, 55.8, 43.9, 37.5, 28.5, 26.1, 19.5, 2.23, 0.41 (two sp2 carbon
signals were either masked by solvent or not observable).
MS (EI, 70 eV): m/z (%) = 558 (2, [M]+), 543 (5), 436 (39), 421
(82), 406 (52), 362 (52), 347 (57), 324 (49), 179 (39), 160 (54), 105
(94), 77 (87), 73 (100).
24.8, 23.1, 1.96.
MS (EI, 70 eV): m/z (%) = 332 (3, [M]+), 259 (3), 186 (12), 185
(80), 73 (100), 59 (26).
73
Yellow powder; mp 182–186 °C (CH2Cl2–PE).
IR (KBr): 2920, 2840, 1667, 1593, 1540, 1508, 1277, 1245, 962,
845, 719 cm–1.
1H NMR (500 MHz, C6D6): d = 8.13 (AA¢m, 2 H), 7.09 (BB¢m, 2
H), 2.52 (m, 2 H), 1.77 (m, 2 H), 1.43 (m, 2 H), 1.33 (m, 2 H), 1.26
(m, 2 H), 0.39 (s, 18 H).
13C NMR (100 MHz, CDCl3): d = 184.4, 164.7, 141.6, 135.7, 133.6,
127.1, 40.3, 27.3, 24.3, 0.98.
77
Pale yellow solid; mp 223–227 °C (CH2Cl2–Et2O).
IR (KBr): 2937, 1710, 1664, 1584, 1273, 1247, 980, 839, 705 cm–1.
1H NMR (400 MHz, C6D6): d = 8.18 (m, 2 H), 7.81 (d, J = 7.7 Hz,
1 H), 7.07 (m, 3 H), 6.97 (t, J = 8.0 Hz, 1 H), 6.43 (d, J = 7.7 Hz, 1
H), 6.09 (br s, 1 H), 3.23 (s, 3 H), 3.14 (m, 1 H), 2.96 (m, 1 H), 1.79
(m, 1 H), 1.71–1.59 (m, 3 H), 1.40–1.29 (m, 2 H), 0.48 (s, 9 H), 0.47
(s, 9 H).
13C NMR (100 MHz, C6D6): d = 165.4, 160.4, 159.6, 138.4, 134.2,
132.9, 131.3, 129.9, 128.6, 124.5, 119.3, 117.2, 72.4, 55.9, 44.8,
38.0, 29.5, 26.6, 20.5, 1.71, 1.21 (signals for the three carbonyl and
two sp2 carbons were not observed).
MS (EI, 70 eV): m/z (%) = 408 (35, [M]+), 393 (25), 319 (15), 147
(17), 78 (13), 75 (100).
UV/Vis (MeOH): lmax (log e) = 250 (4.24), 350 (3.68), 390 sh
(3.42), 410 sh nm (3.22).
Anal. Calcd for C24H32O2Si2: C, 70.53; H, 7.89. Found: C, 70.53; H,
7.97.
MS (EI, 70 eV): m/z (%) = 558 (5, [M]+), 543 (3), 436 (29), 428
(49), 406 (31), 105 (100), 77 (45), 73 (77).
74
Colorless solid; mp 160–165 °C (MeOH).
Synthesis 2010, No. 13, 2179–2200 © Thieme Stuttgart · New York

PAPER
Cobalt-Mediated Cycloadditions
2199
78
References
1H NMR (400 MHz, THF-d8): d = 7.91 (d, J = 6.2 Hz, 1 H), 7.85
(m, 1 H), 7.20 (m, 1 H), 7.04 (m, 1 H), 3.18 (d, J = 8.0 Hz, 1 H),
2.86 (br d, J = 9.7 Hz, 1 H), 2.04–1.96 (m, 2 H), 1.78–1.57 (m, 3
H), 1.37 (m, 1 H), 1.13 (app q, J = 8.0 Hz, 1 H), 0.25 (br s, 9 H),
0.19 (s, 9 H).
(1) For recent reviews, see: (a) Galan, B. R.; Rovis, T. Angew.
Chem. Int. Ed. 2009, 48, 2830. (b) Hess, W.; Treutwein, J.;
Hilt, G. Synthesis 2009, 3537. (c) Ogasawara, M.;
Watanabe, S. Synthesis 2009, 1761. (d) Shibata, T.;
Tsuchikama, K. Org. Biomol. Chem. 2008, 6, 1317.
(e) Scheuermann née Taylor, C. J.; Ward, B. D. New J.
Chem. 2008, 32, 1850. (f) Omae, I. Appl. Organometal.
Chem. 2008, 22, 149. (g) Rayabarapu, D. K.; Cheng, C.-H.
Acc. Chem. Res. 2007, 40, 971. (h) Tanaka, K.; Nishida, G.;
Sagae, H.; Hirano, M. Synlett 2007, 1426. (i) Heller, B.;
Hapke, M. Synlett 2007, 1085. (j) Agenet, N.; Buisine, O.;
Slowinski, F.; Gandon, V.; Aubert, C.; Malacria, M. Org.
React. 2007, 68, 1. For selected reviews specifically dealing
with CpCo-mediated cooligomerizations of unsaturated
substrates, see: (k) Vollhardt, K. P. C. Angew. Chem., Int.
Ed. Engl. 1984, 23, 539. (l) See also: Vollhardt, K. P. C.
Lect. Heterocycl. Chem. 1987, 9, 59. (m) See also:Miljanić,
O. Š.; Vollhardt, K. P. C. In Carbon-Rich Compounds: From
Molecules to Materials; Haley, M. M.; Tykwinski, R. R.,
Eds.; Wiley-VCH: Weinheim, 2006, 140.
13C NMR (100 MHz, THF-d8): d = 181.2, 154.5, 152.2, 140.7,
139.3, 138.8, 134.1, 127.9, 125.0, 124.2, 121.5, 120.4, 107.2, 45.6,
33.3, 32.5, 28.0, 23.7, 0.87 (br), –3.32.
79
Light yellow oil.
IR (KBr): 2950, 2875, 1704, 1663, 1600, 1302, 1259, 976, 860, 735
cm–1.
1H NMR (300 MHz, C6D6): d = 8.16 (dd, J = 7.7, 1.4 Hz, 1 H), 7.94
(dd, J = 7.7, 1.4 Hz, 1 H), 7.02 (td, J = 7.5, 1.5 Hz, 1 H),6.95 (td,
J = 7.5, 1.5 Hz, 1 H), 2.88 (br t, J = 4.5 Hz, 1 H), 2.34 (br d,
J = 13.8 Hz, 1 H), 2.21 (ddd, J = 12.1, 6.6, 3.2 Hz, 1 H), 1.52–1.32
(m, 3 H), 1.07 (m, 2 H), 0.89 (m, 1 H), 0.72 (m, 1 H), 0.41 (s, 9 H),
0.40 (s, 9 H).
13C NMR (75 MHz, C6D6): d = 192.6 (C), 183.1 (C), 179.1 (C),
145.2 (C), 136.5 (C), 134.7 (CH), 134.4 (C), 133.5 (CH), 126.9
(CH), 74.2 (C), 61.1 (C), 40.6 (CH), 39.7 (CH), 29.9 (CH2), 25.9
(CH2), 25.2 (CH2), 24.3 (CH2), 2.60 (CH3), 0.21 (CH3) (one signal
was masked by solvent).
13C NMR (125 MHz, CDCl3): d = 192.6, 183.0, 180.7, 144.4, 136.1,
134.8, 133.7, 127.7, 126.9, 74.5, 61.2, 40.2, 39.5, 29.7, 25.6, 24.8,
23.9, 2.17, –0.31.
MS (EI, 70 eV): m/z (%) = 424 (7, [M]+), 409 (60), 127 (28), 75
(41), 73 (100), 57 (38).
(2) (a) García-Rubín, S.; Varela, J. A.; Castedo, L.; Saá, C.
Chem. Eur. J. 2008, 14, 9772. (b) Kim, D. H.; Chung, Y. K.;
Han, J. W. Bull. Korean Chem. Soc. 2008, 29, 1224.
(c) Alvarez, L. X.; Bessières, B.; Einhorn, J. Synlett 2008,
1376. (d) Shibata, T.; Kawachi, A.; Ogawa, M.; Kuwata, Y.;
Tsuchikama, K.; Endo, K. Tetrahedron 2007, 63, 12853.
(e) Tanaka, K.; Nishida, G.; Sagae, H.; Hirano, M. Synlett
2007, 1426. (f) Varela, J. A.; Rubín, S. G.; González-
Rodriguez, C.; Castedo, L.; Saá, C. J. Am. Chem. Soc. 2006,
128, 9262. (g) Kezuka, S.; Tanaka, S.; Ohe, T.; Nakaya, Y.;
Takeuchi, R. J. Org. Chem. 2006, 71, 543. (h) Tsuchikama,
K.; Kuwata, Y.; Shibata, T. J. Am. Chem. Soc. 2006, 128,
13686. (i) Wu, Y.-T.; Hayama, T.; Baldridge, K. K.; Linden,
A.; Siegel, J. S. J. Am. Chem. Soc. 2006, 128, 6870. (j) Wu,
M.-S.; Rayabarapu, D. K.; Cheng, C.-H. Tetrahedron 2004,
60, 10005. (k) Sung, M. J.; Pang, J.-H.; Park, S.-B.; Cha, J.
K. Org. Lett. 2003, 5, 2137. (l) Nishikawa, T.; Shinokubo,
H.; Oshima, K. J. Am. Chem. Soc. 2001, 123, 4629.
(m) Sambaiah, T.; Huang, D.-J.; Cheng, C.-H. J. Chem. Soc.,
Perkin Trans. 1 2000, 195. (n) Yamamoto, Y.; Kitahara, H.;
Ogawa, R.; Kawaguchi, H.; Tatsumi, K.; Itoh, K. J. Am.
Chem. Soc. 2000, 122, 4310. (o) Son, S. U.; Choi, D. S.;
Chung, Y. K.; Lee, S.-G. Org. Lett. 2000, 2, 2097.
Anal. Calcd for C24H32O3Si2: C, 67.88; H, 7.59. Found: C, 68.01; H,
7.48.
81
Red-brown solid; mp 96–98 °C (EtOAc–hexanes).
IR (KBr): 3460–3320, 2928, 2852, 1635, 1601, 1247, 853, 832, 812
cm–1.
1H NMR (500 MHz, C6D6): d = 8.20 (d, J = 7.7 Hz, 1 H), 7.56 (d,
J = 7.7 Hz, 1 H), 7.27 (t, J = 7.5 Hz, 1 H), 7.12 (t, J = 7.5 Hz, 1 H),
5.13 (d, J = 9.9 Hz, 1 H), 4.43 (s, 5 H), 2.32 (dt, J = 8.0, 5.9 Hz, 1
H), 1.83 (ddd, J = 10.8, 8.2, 4.6 Hz, 1 H), 1.67 (m, 1 H), 1.53–1.41
(m, 3 H), 1.21 (dt, J = 12.5, 4.7 Hz, 1 H), 1.11 (m, 2 H), 0.99 (m, 1
H), 0.60 (m, 1 H), 0.52 (br s, 9 H), 0.32 (s, 9 H).
13C NMR (125 MHz, C6D6): d = 192.7, 144.0, 132.5, 132.3, 128.3,
126.1, 125.6, 105.9, 90.7, 81.1, 67.7, 62.2, 59.3, 44.4, 39.8, 32.9,
32.3, 24.8, 21.9, 3.82 (2 C).
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Cheng, C.-H. New J. Chem. 1998, 22, 1147. (u)Yamamoto,
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(x) Johnson, E. S.; Balaich, G. J.; Rothwell, I. P. J. Am.
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(y) Zhou, Z.; Costa, M.; Chiusoli, G. P. J. Chem. Soc.,
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MS (EI, 70 eV): m/z (%) = 534 (2, [M]+), 518 (1), 443 (3), 408 (3),
320 (22), 305 (31), 75 (42), 73 (100).
UV/Vis (MeOH): lmax (log e) = 268 (4.21), 350 sh (3.50), 464 nm
(3.05).
Anal. Calcd for C29H39CoO2Si2: C, 65.14; H, 7.35. Found: C, 65.33;
H, 7.44.
Acknowledgment
This work was made possible by initial support from the NIH (GM-
22479) and then by the NSF (CHE 0907800).
(3) For recent work, see: Amslinger, S.; Aubert, C.; Gandon, V.;
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Synthesis 2010, No. 13, 2179–2200 © Thieme Stuttgart · New York

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C. Aubert et al.
PAPER
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Synthesis 2010, No. 13, 2179–2200 © Thieme Stuttgart · New York