Regioselective preparation of functionalized exo-methylene- cyclopentanes and exo-methylenepyrrolidines via silaborative carbocyclization of 1,6-enynes

Article abstract of DOI:10.1002/adsc.201000434

Silaborative carbocyclization of 1,6-enynes catalyzed by Pd-PEPPSI-IPr {PEPPSI=pyridine-enhanced precatalyst preparation stabilization and initiation; IPr=N,N-bis[2,6-(diisopropyl)phenyl]imidazolium} employing either (dimethylphenylsilyl)pinacolborane or (chlorodimethylsilyl)pinacolborane provides access to densely functionalized five-membered rings as single diastereomers in excellent yields. The vinylboronate functions were employed in palladium-catalyzed Suzuki cross-coupling reactions with a range of aryl bromides, containing electron-withdrawing as well as electron-donating substituents, furnishing arylated exo-methylenecyclopentanes or exo-methylenepyrrolidines in good yields. Subsequent oxidation of the isopropoxydimethylsilyl function generated via addition of (chlorodimethylsilyl) pinacolborane provided access to hydroxymethyl derivatives of the arylated compounds. Use of a chiral ester, bismenthyl (2-propenyl)(2-propynyl)malonate, afforded two diastereomeric products which could be separated, thereby giving access to the cyclized compounds as single isomers, with opposite absolute configurations at the newly formed stereocenter.

Full text of DOI:10.1002/adsc.201000434

FULL PAPERS
DOI: 10.1002/adsc.201000434
Regioselective Preparation of Functionalized exo-Methylene-
cyclopentanes and exo-Methylenepyrrolidines via Silaborative
Carbocyclization of 1,6-Enynes
Martin Gerdin,a Sailendra Kumar Nadakudity,a Christin Worch,a
and Christina Moberga,*
a
KTH School of Chemical Science and Engineering, Organic Chemistry, SE-10044 Stockholm, Sweden
Fax : (+46)-8-791-2333; e-mail: kimo@kth.se
Received: June 3, 2010; Revised: August 26, 2010; Published online: October 12, 2010
Supporting information for this article is available on the WWW under
http://dx.doi.org/10.1002/adsc.201000434.
Abstract: Silaborative carbocyclization of 1,6-enynes exo-methylenepyrrolidines in good yields. Subse-
catalyzed by Pd-PEPPSI-IPr {PEPPSI=pyridine-en- quent oxidation of the isopropoxydimethylsilyl func-
hanced precatalyst preparation stabilization and ini- tion generated via addition of (chlorodimethylsilyl)-
tiation; IPr=N,N-bisACTHNUTRGENUGN[2,6-(diisopropyl)phenyl]imida- pinacolborane provided access to hydroxymethyl de-
zolium} employing either (dimethylphenylsilyl)pina- rivatives of the arylated compounds. Use of a chiral
colborane or (chlorodimethylsilyl)pinacolborane pro- ester, bismenthyl (2-propenyl)(2-propynyl)malonate,
vides access to densely functionalized five-membered afforded two diastereomeric products which could be
rings as single diastereomers in excellent yields. The separated, thereby giving access to the cyclized com-
vinylboronate functions were employed in palladi- pounds as single isomers, with opposite absolute con-
um-catalyzed Suzuki cross-coupling reactions with a figurations at the newly formed stereocenter.
range of aryl bromides, containing electron-with-
drawing as well as electron-donating substituents, Keywords: cross-coupling; cyclization; enynes; oxi-
furnishing arylated exo-methylenecyclopentanes or dation; palladium; silylboranes
Introduction
bond, resulting in the formation of vinylsilanes
(Figure 1, a), whereas the other two types of interele-
A large variety of catalytic methods, using a wide ment compounds react via insertion into the metal-
range of metal catalysts, for the cyclization of 1,6- boron bond, thereby producing vinylboronates
enynes have been reported in recent years.[1] The re- (Figure 1, b and c, respectively).
actions provide efficient and convenient access to
The silastannylative carbocyclization of 1,6-enynes
five-membered carbocycles and heterocycles. Of par- has been most thoroughly studied. A number of 1,6-
ticular interest are methods leading to products con- enynes were successfully employed using either phos-
taining reactive functional groups for further synthetic phine-free Pd complexes[6a] or Pd N-heterocyclic car-
elaboration. Silacarbocyclizations,[2] boracarbocycliza- bene complexes[6b,c] as catalysts, giving the products in
tions,[3] and stannacarbocyclizations,[4] including a few good yields. Terminally substituted enynes were gen-
enantioselective processes,[2d,f,3a] are examples of trans- erally less reactive than unsubstituted substrates, the
formations of this type.
former resulting in moderate to poor yields. The only
When compounds containing interelement link-
[6]
[7]
[8]
ACHTUNGTRENNUNG
ages,[5] such as Si Sn, B Sn, and B Si are added,
À
À
À
cyclized products containing two reactive functional
groups can be obtained. The carbocyclizations are
usually catalyzed by group 10 metal complexes and
proceed in competition with interelement addition to
the triple bond.[9] Compounds with Si Sn linkages
À
Figure 1. Products obtained by carbocyclization of 1,6-
À
À
À
react by insertion of the alkyne into the metal-silicon enynes with Si Sn (a), B Sn (b), and B Si (c) bonds.
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formed products, and that 4 is commercially avail-
able.[14] For the initial experiments 1:2 mixtures of
Pd2ACTHNUTRGNE(NUG dba)3 and various phosphorus ligands were at-
tempted. The electronic and steric properties of the
catalysts are crucial for the different steps in the cata-
lytic cycle to proceed. However, neither phosphanes
such as PPhMe2 and PPh3, nor phosphites [P
(OPh)3] resulted in formation of the desired cyclized
ACHTUNGTRENNUNG(OEt)3,
PACHTUNGTRENNUNG
product in toluene at 1108C, although the product
from silaboration of the alkyne could be observed.
N-heterocyclic carbenes[15] have proven to serve as
versatile ligands for a number of catalytic processes.[16]
PEPPSI (pyridine-enhanced precatalyst preparation
stabilization and initiation) catalysts,[17] which are
Scheme 1. Silaborative carbocyclization of enyne 1a accord-
ing to Tanaka.[8]
silaborative carbocyclization reported is that by commercial air- and water-stable palladium com-
Tanaka and co-workers who, as part of a study on si- plexes, have proven to exhibit excellent reactivity in a
laborations of alkynes and diynes, reacted enyne 1a large number of palladium-catalyzed cross-coupling
(OCH2)3CEt reactions.[18] The commercial Pd(II) complexes are ac-
with silylborane 2 using a Pd2ACHTNUGTRNENUG(dba)3/PCAHTUNGTRENNUGN
(etpo) catalyst system (M:L ratio 1:2, C6D6, 1108C, tivated with base to generate catalytically active
2 h) to obtain cyclopentane derivative 3 in 84% yield Pd(0) carbene species. Encouraged by the fact that N-
along with a by-product (9%) believed to be obtained heterocyclic carbenes catalyzed the silastannative car-
by silaboration of the triple bond (Scheme 1).[8] Al- bocyclization of 1,6-enynes,[6b,c] in moderate to good
though the product offers promising reactivities for yields, we decided to switch to dichloro-N,N-bisACHTUNGTRENNUNG[2,6-
further synthetic elaborations, its reactivity was not (diisopropyl)phenyl]imidazolium(3-chloropyridine)-
investigated. Due to the synthetic versatility of silyl[10] palladium, Pd-PEPPSI-IPr,[19] as catalyst. We were
and boryl[11] functions generated via silaborations of pleased to find that the desired product was obtained
unsaturated substrates,[12] we decided to extend our in 50% yield in diethyl ether as a 5:1 mixture of iso-
studies on silylboranes[13] to the silaborative carbocyc- mers,[20] with that having Z configuration of the ole-
lization of 1,6-enynes, and to explore the utility of the finic bond (5b) as the major isomer. Although no by-
products formed.
products could be identified, the enyne was complete-
ly consumed during the reaction. As enyne decompo-
sition seemed to be a major problem, the amount of
enyne 1b, which is readily available from inexpensive
starting materials, was increased to 2 equivalents and
the reaction temperature decreased to 508C. This led
to the formation of the cyclized compound 5b in 98%
Results and Discussion
Palladium-Catalyzed Silaborations
We started our investigation by examining the reac- yield as a single diastereomer (Scheme 2), suggesting
tion of enyne 1b, derived from dimethyl malonate, that substrate decomposition was caused by the cata-
with (dimethylphenylsilyl)pinacolborane (4) in the lyst. The ethyl ester 1a reacted under the same condi-
presence of Pd(0) catalysts. The choice of 4 rather tions to provide 5a (96% yield), also as a single dia-
than 2 was dictated by the facts that boronic esters stereomer.
are suitable partners for Suzuki cross-couplings, thus
Silaborative carbocyclization of enyne 6 was also
allowing further transformations of the initially possible using Pd-PEPPSI-IPr as a catalyst. Pyrroli-
Scheme 2. Silaborative carbocyclization of enynes 1.
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Regioselective Preparation of Functionalized exo-Methylenecyclopentanes and exo-Methylenepyrrolidines
Table 1. Silaborative carbocyclization of enyne 6.[a] Table 2. Silaborative carbocyclization of enyne 6.[a]
Entry
Temp. [8C]
Yield [%][b]
dr
Entry
Catalyst (mol%)
Equiv. of 6
Yield [%][b]
1
2
3
4
110
80
50
31
42
49
25
2:1
5:1
>98:2
>98:2
1
2
3
4
10
10
5
1
2
2
2
56
84
93
96
r.t.
1
[a]
Reactions performed on a 0.1-mmol scale in Et2O using
10 mol% Pd-PEPPSI-IPr.
Determined by H NMR using 1-methoxynaphthalene as
[a]
Reactions performed on a 0.1-mmol scale in THF using
Pd-PEPPSI-IPr catalysis for 24 h at 508C, yielding the
product as a single detectable diastereomer (1H NMR).
[b]
1
internal standard.
[b]
1
Determined by H NMR using 1-methoxynaphthalene as
internal standard.
dine 7 was obtained in modest yield (25–39%) when
1:1 mixtures of enyne and silylborane were used
(Table 1); at 1108C merely a 31% yield of a 2:1 mix- moiety were subjected to the same reaction condi-
ture of isomers was obtained (entry 1). The optimum tions (50, 80 and 1108C employing 5 mol% Pd-
reaction temperature was found to be 508C; at this PEPPSI-IPr). In most cases no cyclized product was
temperature decomposition was reduced and the de- observed, although low yields of products were ob-
sired product was formed in 49% yield (entry 3). tained from 8 and 9, which provided cyclized com-
Gratifyingly, the selectivity of the reaction was also pounds 10 (as two diasteromers in a 14.3:1 ratio) and
improved and the product was now obtained as a 11 (as a 19:1 mixture of diastereomers) in 10 and
single detectable diastereomer (1H NMR).
22% yield, respectively (Scheme 3).
Slow addition of enyne 6 (over 15 h, using a syringe
Cyclizations of enynes 1c and d, with ester groups
pump) to silylborane 4 did not lead to any improve- derived from chiral alcohols, proceeded with low but
ment; after 18 h at 508C a disappointing 50% yield significant selectivities, as determined by 1H NMR
was recorded. Exchange of diethyl ether for THF im- spectroscopy (Scheme 4). Thus 5c was obtained as a
proved the yield slightly, to 56% (Table 2, entry 1). 61:39 ratio of diastereomers, in a combined yield of
Use of two equivalents of 6 resulted in a considerably 78% after chromatography, and 5d as a 59:41 mixture
higher yield, 84% (entry 2). The yield could be im- in 68% yield. Although poor diastereoselectivity was
proved even further by reducing the amount of cata- observed, the two diastereomers obtained by silabora-
lyst employed, underlining the importance of sup- tive cyclization of bismenthyl (2-propenyl)(2-propy-
pressing the decomposition pathways (entries 3 and nyl)malonate (1c) could be separated by column chro-
4).
matography, thus providing the two compounds as
A number of enynes bearing substituents at the ter- single isomers (Figure 2).
minal position of either the alkene[21] or alkyne[22]
Scheme 3. Cyclization of substituted enynes 8 and 9.
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Scheme 4. Chiral esters employed in silaborative carbocyclizations of enyne.
metal center. In the case of phosphorus ligands, which
usually lead to SiBML2 complexes, decoordination of
one ligand is needed, whereas with the present 1:1
metal ligand ratio, the required three-coordinate com-
plex is directly formed. Reductive elimination, finally,
is facilitated by bulky ligands, such as PEPPSI-IPr.[18]
The success of the carbene ligand is probably the
result of these elementary catalytic steps being fa-
vored.
Figure 2. Diastereomers obtained from chiral enyne.
Mechanism
Palladium-Catalyzed Arylations
The mechanism of Pt-catalyzed silaborations of al- To explore the reactivity of the vinylboronates
kynes in the presence of phosphane ligands was inves- formed, the Suzuki cross-coupling reaction between
tigated by Ozawa et al. by means of NMR spectrosco- pyrrolidine 7 and bromobenzene was investigated.
py.[23] The reaction was shown to follow the generally After an initial screening of reaction conditions we
accepted catalytic cycle, proceeding via oxidative ad- found that the best result was obtained by using
dition of the silylborane to a zerovalent metal com- Pd
(PPh3)4 as catalyst in a mixture of toluene, ethanol
À
plex, insertion of the acetylene into the Pt B bond and water. Next, the substrate scope was examined
and, finally, reductive elimination. In reactions of 1,6- using various aryl bromides and two types of vinylbor-
enynes, carbopalladation to form a five-membered onates. The results are summarized in Table 3.
ring probably precedes reductive elimination, al-
though an alternative path proceeding via pallada- pling of vinylpyrrolidine 7 and bromobenzene proved
stannylation was suggested for silastannative carbocy- to be efficient for all other aryl bromides tested, and
clization of 1,6-enynes.[6c] The mechanism of interele- the corresponding arylated products were isolated in
The optimized conditions for the Suzuki cross-cou-
ACHTUNGTRENNUNG
ACHTUNGTRENNUNG
ment additions catalyzed by metal-carbene complexes good yields. Neither electron-donating nor electron-
has not been studied, but probably follows a similar withdrawing substituents on the aryl bromides
pathway (Scheme 5). Pd-PEPPSI-IPr is activated by seemed to have a significant influence on the outcome
treatment with MeMgCl to form the active Pd(0) car- of the reaction (entries 2 and 5). Moreover, it was
bene complex, with dissociation of the labile 3-chloro- possible to couple even sterically demanding aryl bro-
pyridine ligand.[18] Oxidative addition of the silylbor- mides such as 2-bromomesitylene (entry 8) and 1-bro-
ane to this complex is facilitated by the good s-donor monaphthalene (entry 9) in good yields. Not only vi-
ability of the carbene ligand. Insertion of the alkyne nylpyrrolidine 7 but also vinylcyclopentane 5a turned
must proceed via a three-coordinated complex, in out to be a suitable substrate for the Suzuki cross-
order to allow coordination of the triple bond to the coupling (entries 10 and 11).
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Regioselective Preparation of Functionalized exo-Methylenecyclopentanes and exo-Methylenepyrrolidines
Scheme 5. Proposed mechanism for silaboration of 1,6-enynes.
Addition of (Chlorodimethylsilyl)pinacolborane –
Oxidation of the Silyl Function
Table 3. Suzuki cross-coupling of vinylboronates 5a or 7 Next we moved to the functionalization of the silyl
with aryl bromides.[a]
group. The dimethylphenylsilyl substituent proved to
be inert towards the standard conditions used for oxi-
dation.[24] Suginome and co-workers recently prepared
a number of silylboranes which exhibit higher reactiv-
ity in silaborations and which result in products with
more reactive silyl functions.[25] (Chlorodimethylsilyl)-
pinacolborane (14) was prepared according to their
procedure and reacted with enynes 1a and 6 in the
presence of Pd-PEPPSI-IPr to yield cyclized products
15 and 16, respectively (Scheme 6). The reaction con-
ditions were optimized using enyne 6. The reaction
proceeded smoothly in THF at room temperature
overnight, but the yield was highly dependent on the
amount of catalyst (Table 4). With 10 mol% catalyst
and 1.5 equivalents of enyne, the cyclized product 15
was obtained as a single diastereomer in 75% yield
(entry 1). This was somewhat improved, to 85%,
when the catalyst was added slowly over 2 h (entry 2).
Like in reactions using silylborane 4, the yield was
further improved by lowering the amount of the cata-
lyst to 5 mol% (entry 3). Even in the presence of only
one equivalent of enyne the reaction was successful.
With 1–2 mol% catalyst a quantitative yield of 15 was
observed (entries 5–6), whereas with 5 mol% of cata-
lyst the yield was slightly lower (entry 4). With silyl-
borane 14 decomposition of the substrate by the cata-
lyst is evidently less pronounced than with 4, probably
as a result of the enhanced reactivity of 14 in the sila-
borative carbocyclization.
Entry Substrate Ar
Product Yield [%][b]
1[c]
2
3
4
5
7
7
7
7
7
7
7
Ph
12a
12b
12c
12d
12e
12f
12g
87
77
78
80
83
88
77
77
86
80
85
4-MeOC6H4
3-MeOC6H4
2-MeOC6H4
4-CNC6H4
4-ClC6H4
3-pyridyl
6
7
8
7
2,4,6-Me3C6H2 12h
9
10
11
7
5a
5a
1-naphthyl
4-MeOC6H4
4-CNC6H4
12i
13a
13b
[a]
All reactions were performed on a 0.20-mmol scale using
substrate 7 or 5a (1.0 equiv.), aryl bromide (1.2 equiv),
Na2CO3 (5 equiv.), and PdACTHNURTGENUNG(PPh3)4 (10 mol%), in toluene/
ethanol/water (3:1:1) (0.05M with respect to the sub-
strate 7 or 5a), at 808C for 18 h.
Isolated yield.
Reaction was performed using 2.0 equiv. of bromoben-
zene.
[b]
[c]
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Scheme 6. Silaborative carbocyclizations followed by arylation and oxidation.
Table 4. Silaborative carbocyclization of 6 with silylborane
and H2O2 in DMF[26] in order to oxidize the silyl func-
tional groups. Both reactions yielded the same pyrro-
lidine derivative 21. Therefore, the mixture of 19a
and b was oxidized to yield pyrrolidine derivative 21
(70% yield from 17, Scheme 5). This type of com-
pound, with an E/Z ratio of 1:3, has previously been
obtained in low yield via titanocene-mediated vinyla-
tion.[27] Treatment of 20 with KF and H2O2 in DMF
provided alcohol 22 (64% from 18).
14.
Entry Catalyst
(mol%)
Equiv. of Yield of 15
6
dr
[%][a]
1
2
3
4
5
6
10
10[b]
5[b]
5
2
1
1.5
1.5
1.5
1
75
85
96
98
>99:1
>99:1
>99:1
>99:1
>99:1
>99:1
1
1
>99
>99
Borylcarbocyclizations[3a] and silylcarbocycliza-
tions[2g] have previously been shown to be synthetical-
ly versatile processes in that the products obtained
can be further elaborated via Pd-catalyzed cross-
coupling reactions. The silaborative carbocyclization
presented here provides products with an additional
functional group, thereby serving as more versatile
starting materials.
[a]
Reactions performed in THF using Pd-PEPPSI-IPr as
catalyst overnight at room temperature; yields were de-
termined by H NMR using 1-methoxynaphthalene as in-
1
ternal standard.
[b]
Slow addition of catalyst.
Cyclization of 1a required a higher catalyst loading.
Optimized conditions employed 5 mol% of the cata-
lyst and 1 equivalent of 1a. The products (15 and 16) Conclusions
were sensitive to moisture and therefore converted
into isopropyl derivatives 17 and 18, respectively, A silaborative carbocyclization reaction using either
which were stable to chromatography and isolated in (dimethylphenylsilyl)pinacolborane (4) or the more
89 and 78% yields (over two steps), respectively.
reactive (chlorodimethylsilyl)pinacolborane (14) has
Suzuki cross-couplings of 17 and 18 with 4-bromo- been developed, selectively furnishing functionalized
benzonitrile proceeded as expected. As a conse- five-membered derivatives in high yields. The reaction
quence of the basic conditions (Na2CO3) the silyl al- shows tolerance to substituents at the double or triple
cohol 19b was obtained along with the expected 19a bond of the enyne. Cyclization of an enyne containing
from 17. Formation of 19b could be avoided by menthyl ester functions resulted in the formation of
adding water and ethanol (used as co-solvents) when two diastereomers, which could be separated, thereby
the temperature of the reaction mixture had reached providing access to single isomers of the cyclized com-
808C. By nOe studies it was concluded that the con- pounds.
figuration of the double bond remained intact. In con-
A protocol for the Suzuki cross-coupling of the re-
trast to the situation with 17, Suzuki coupling of 18 sulting vinylboronates formed was also developed. A
with the same bromide always resulted in a single wide range of aryl bromides, containing electron-do-
product, 20. Attempts to perform the palladium-cata- nating as well as electron-withdrawing substituents,
lyzed silaboration and the Suzuki coupling in one-pot, reacted to afford the corresponding arylated products
using the same catalyst (Pd-PEPPSI-IPr), were unsuc- in good yields and with retention of the double bond
cessful.
configuration. Subsequent oxidation of the silyl func-
Compounds 19a and 19b were separated by flash tion resulted in formation of alcohol derivatives. The
chromatography and each compound treated with KF methodology presented here thus provides access to
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Regioselective Preparation of Functionalized exo-Methylenecyclopentanes and exo-Methylenepyrrolidines
stereo- and regiochemically defined exo-methylenecy- (Z)-Dimethyl 3-[(Dimethylphenylsilyl)methyl]-4-
clopentanes and exo-methlyenepyrrolidines contain- [(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-
ing two functional groups for further synthetic elabo- methylene]cyclopentane-1,1-dicarboxylate (5b)
rations.
The reaction was performed using 2 equiv. of enyne 5 and
1 mol% Pd-PEPPSI-IPr catalyst at 508C for 24 h. After
flash chromatography on SiO2 (gradient of 5–20% Et2O in
hexane) the product was isolated as a colorless oil; yield:
Experimental Section
98%. The E configuration of the double bond was assigned
1
by NOESY spectroscopy. H NMR (500 MHz, CDCl3): d=
0.34 (s, 3H), 0.35 (s, 3H), 0.87 (dd, J=14.3, 12.8 Hz, 1H),
1.21 (s, 6H), 1.23 (s, 6H), 1.39 (dd, J=14.3, 2.4 Hz, 1H),
1.83 (dd, J=13.5, 5.7 Hz, 1H), 2.60 (ddd, J=13.5, 8.3,
1.0 Hz, 1H), 2.80 (d, J=16.6 Hz), 3.13 (m, 1H), 3.26 (app.
dt, J=16.6, 2.1 Hz, 1H), 3.67 (s, 3H), 3.68 (s, 3H), 5.18–5.21
(m, 1H), 7.31–7.36 (m, 3H), 7.51–7.55 (m, 2H); 13C NMR
(125 MHz, CDCl3): d=À1.88, À1.58, 25.1, 25.3, 38.8, 41.3,
44.2, 53.07, 53.09, 59.0, 83.2, 110.0 (br), 130.0, 129.1, 133.9,
140.0, 172.4, 172.8, 173.4; anal calcd. for C25H37BO4Si: C
63.55, H 7.89; found: C 63.48, H 7.73%.
General Considerations
All transition metal-catalyzed reactions were performed
inside a nitrogen-filled glovebox using oven dried glassware.
After the reaction flask had been sealed, heating was per-
formed outside the glovebox. Toluene, THF, Et2O, and
CH2Cl2 were dried using a Glass-contour solvent dispensing
system. Compounds 1a,[28] 1b,[29] 4,[30] 6,[31] 9,[32] and 14[25]
were synthesized according to literature procedures. All
other chemicals were of at least 97% purity and used as re-
1
ceived. H NMR spectra were recorded at 500 or 400 MHz
and 13C NMR spectra at 125 or 100 MHz. The H and 13C
1
chemical shifts are reported relative to CHCl3.
(E)-3-[(Dimethylphenylsilyl)methyl]-4-[(4,4,5,5-tetra-
methyl-1,3,2-dioxaborolan-2-yl)methylene]-1-
tosylpyrrolidine (7)
General Procedure for Silaborative Carbocyclization
of Enynes using Silylborane 4
The reaction was performed using 2 equiv. of enyne 6 and
1 mol% Pd-PEPPSI-IPr catalyst at 508C for 24 h. After
flash chromatography on SiO2 (1:1 DCM/hexane) the prod-
uct was isolated as a white solid; yield: 81%. The E configu-
ration of the double bond was assigned by NOESY spectros-
MeMgCl in THF (3M, 13.3 mL, 0.04 mmol) was added to a
THF solution (400 mL) of Pd-PEPPSI-IPr (13.6 mg,
0.02 mmol) at À358C inside a nitrogen-filled glovebox, and
the resulting solution allowed to reach room temperature
over 1 h. This solution (0.05M in Pd, 10–100 mL) was added
to a vial containing silylborane 4 (26.2 mg, 0.1 mmol), the
enyne (1–2 equiv.), and 1-methoxynapthalene (15.8 mg,
0.1 mmol) in THF (300 mL). The vial was capped and heated
outside the glovebox. The reaction was monitored by taking
out 20 mL samples, evaporating the solvent and recording
the 1H NMR spectrum. NMR yields were calculated by
comparing the integrals of the signals from the olefinic
proton in the product and the methoxy group in 1-methoxy-
napthalene. Purification was performed by evaporating the
solvents, adding the crude product onto a SiO2 column and
eluting with an appropriate eluent. p-Anisaldehyde solution
was used to develop TLC plates.
1
copy. H NMR (400 MHz, CDCl3): d=0.32 (s, 3H), 0.34 (s,
3H), 0.88–0.96 (m, 2H), 1.213 (s, 6H), 1.216 (s, 6H), 2.40 (s,
3H), 2.97 (dd, J=9.0, 6.0 Hz, 1H), 3.08 (dd, J=9.6, 1.8 Hz,
1H), 3.17–3.27 (m, 1H), 3.58 (dd, J=15.0, 1.8 Hz, 1H), 4.03
(app. dt, J=15.0, 1.7 Hz, 1H), 5.08–5.12 (m, 1H), 7.26–7.30
(m, 2H), 7.33–7.39 (m, 3H), 7.47–7.53 (m, 2H), 7.58–7.64
(m, 2H); 13C NMR (125 MHz, CDCl3): d=À2.18, À2.15,
21.5, 22.6, 24.7, 24.8, 39.2, 53.3, 54.0, 83.1, 109.0 (br), 127.80,
127.82, 129.0, 129.5, 132.6, 133.6, 138.8, 143.5, 167.6.
(Z)-Dimethyl 3-[(Dimethylphenylsilyl)methoxy-
carbonylmethyl]-4-[(4,4,5,5-tetramethyl-1,3,2-dioxa-
borolan-2-yl)methylene]cyclopentane-1,1-
dicarboxylate (10)
(Z)-Diethyl 3-[(Dimethylphenylsilyl)methyl]-4-
[(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-
methylene]cyclopentane-1,1-dicarboxylate (5a)
The reaction was performed using 1.5 equiv. of enyne 8 and
5 mol% Pd-PEPPSI-IPr catalyst at 1108C, 24 h. After flash
chromatography on SiO2 the product was isolated as a color-
less oil contaminated by what seems to be by-products
formed via alkyne silaboration (purity: ~80%, dr 14.3:1).
1H NMR (500 MHz, CDCl3): d=0.43 (s, 3H), 0.45 (s, 3H),
1.26 (s, 12H), 2.44 (ddd, J=12.5, 8.8, 1.7 Hz, 1H), 2.64 (dd,
J=12.5, 10.0 Hz, 1H), 2.82 (d, J=15.9 Hz, 1H), 2.9–3.0 (m,
1H), 3.33 (app. dt, J=15.9, 2.6 Hz, 1H), 3.51 (s, 3H), 3.61
(s, 3H), 3.70 (s, 3H), 5.26 (s, 1H), 7.32–7.40 (m, 3H), 7.54–
7.59 (m, 2H); 13C NMR (125 MHz, CDCl3): d=À2.64,
À1.89, 25.1, 25.4, 37.0, 40.1, 40.5, 46.6, 51.0, 53.0, 53.2, 59.3,
83.4, 128.1, 129.7, 134.3, 134.4, 137.1, 171.1, 171.9, 172.4,
174.8.
The reaction was performed using 1.5 equiv. of enyne 1 and
5 mol% Pd-PEPPSI-IPr catalyst at 508C for 24 h. After
flash chromatography on SiO2 the product was isolated as a
colorless oil. The E configuration of the double bond was
assigned by NOESY spectroscopy. 1H NMR (500 MHz,
CDCl3): d=0.34 (s, 3H), 0.35 (s, 3H), 0.89 (dd, J=12.9,
14.4 Hz, 1H), 1.18 (t, J=7 Hz, 3H), 1.19 (t, J=7 Hz, 6H),
1.21 (s, 6H), 1.22 (s, 6H), 1.40 (dd, J=14.4, 2.2 Hz, 1H),
1.77 (dd, J=13.5, 5.8 Hz, 1H), 2.59 (dd, J=13.5, 8.3 Hz,
1H), 2.78 (d, J=16.5 Hz, 1H), 3.08–3.18 (m, 1H), 3.25 (app.
dt, J=16.5, 2.0 Hz, 1H), 4.05–4.21 (m, 4H), 5.19 (s, 1H),
7.30–7.35 (m, 3H), 7.50–7.56 (m, 2H); 13C NMR (125 MHz,
CDCl3): d=À1.88, À1.60, 14.32, 14.33, 25.13, 25.28, 25.34,
38.8, 41.3, 44.2, 59.2, 61.7, 61.8, 83.2, 110.0, 128.0, 129.1,
133.9, 140.0, 171.9, 172.3, 173.7.
Adv. Synth. Catal. 2010, 352, 2559 – 2570
ꢀ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
asc.wiley-vch.de
2565

Martin Gerdin et al.
FULL PAPERS
ing the cyclized product as a mixture of two diastereomers
(dr 59:41); yield: 98% (1H NMR). After flash chromatogra-
phy on SiO2, using a gradient of Et2O (5–10%) in hexane as
eluent, the product was isolated as a white fluffy solid;
(Z)-Dimethyl 3-[(Dimethylphenylsilyl)-phenyl-
methyl]-4-[(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-
yl)methylene]cyclopentane-1,1-dicarboxylate (11)
1
The reaction was performed using 1.5 equiv. of enyne 9 and
5 mol% Pd-PEPPSI-IPr catalyst at 808C for 24 h. After
flash chromatography on SiO2 (gradient of 5–20% Et2O in
hexane) the product could be isolated as a colorless oil in
~70% purity, dr 95:5. Major contaminant was what seem to
be products of alkyne silaboration. 1H NMR (500 MHz,
CDCl3): d=0.37 (s, 3H), 0.40 (s, 3H), 1.29 (s, 12H), 2.09
(app. dt, J=15.6, 2.3 Hz, 1H), 2.34 (dd, J=13.8, 7.2 Hz,
1H), 2.48 (d, J=15.6 Hz, 1H), 2.68 (ddd, J=13.8, 8.8,
1.2 Hz, 1H), 2.75–2.85 (m, 1H), 3.15 (d, J=5.1 Hz, 1H),
3.64 (s, 3H), 3.65 (s, 3H), 5.21 (br s, 1H), 6.97–7.02 (m, 2H),
7.08–7.17 (m, 3H), 7.24–7.34 (m, 3H), 7.42–7.46 (m, 2H).
yield: 68% (59:41 mixture of isomers). H NMR (500 MHz,
CDCl3): d=0.31 (s, 3H, minor), 0.338 (s, 3H, minor), 0.344
(s, 3H, major), 0.35 (s, 3H, major), 0.62–0.78 (m, 2H), 0.80–
1.02 (m, 12H), 1.18–1.63 (m, 32H), 1.75–2.05 (m, 5H), 2.41
(dd, J=13.0, 7.8 Hz, 1H, major), 2.60–2.78 (m, 2H), 2.98–
3.20 (m, 1H major, 2H minor), 4.79–4.96 (m, 2H), 5.19 (s,
1H, minor), 5.21 (s, 1H, major), 7.14–7.19 (m, 2H), 7.22–
7.37 (m, 11H), 7.52–7.59 (m, 2H); 13C NMR (125 MHz,
CDCl3): d=À1.95, À1.81, À1.45, À1.39, 22.17, 22.23, 23.7,
23.9, 24.0, 24.5, 25.17, 25.20, 25.22, 25.27, 25.7, 25.9, 27.67,
27.74, 30.5, 31.0, 31.2, 31.3, 31.6, 31.7, 34.79, 38.2, 38.6, 40.7,
40.8, 41.6, 41.7, 41.8, 42.0, 43.8, 44.8, 50.5, 50.6, 50.78, 50.80,
60.1, 60.2, 76.85, 76.89, 77.0, 83.1125.72, 125.75, 125.77,
126.02, 126.06, 126.2, 126.3, 128.03, 128.06, 128.39, 128.42,
128.45, 129.14, 129.18, 133.95, 133.99, 139.9, 140.0, 150.55,
150.67, 150.75, 150.79, 171.14, 171.18, 171.24, 173.3, 174.2.
(Z)-3-[(Dimethylphenylsilyl)methyl]-4-[(4,4,5,5-tetra-
methyl-1,3,2-dioxaborolan-2-yl)methylene]cyclopen-
tane-1,1-dicarboxylic Acid Bis-[(À)-menthol] ester (5c)
The reaction was performed using 1.2 equiv. of enyne 1c General Procedure for Suzuki Cross-Coupling of
and 5 mol% Pd-PEPPSI-IPr catalyst at 508C for 24 h, yield-
ing the cyclized product as two diastereomers (dr 61:39);
yield: 95% (1H NMR). After flash chromatography on SiO2,
using 5% Et2O in hexane as eluent, a mixture of the two
products were isolated as a colorless oil; yield: 78% (dr
61:39). The diastereomers were separated using a Biotage SP1
employing a gradient of 1–10% Et2O in pentane as eluent.
Major isomer: Rf =0.32 (10% Et2O/pentane); 1H NMR
(500 MHz, CDCl3): d=0.34 (s, 3H), 0.35 (s, 3H), 0.70 (app.
t, J=7.0 Hz, 6H), 0.78–0.90 (m, 18H), 0.9–1.1 (m, 2H), 1.21
(s, 6H), 1.22 (s, 6H), 1.30–1.53 (m, 4H), 1.64–1.71 (m, 4H),
1.78–1.87 (m, 3H), 1.88–1.95 (m, 2H), 2.51 (ddd, J=13.3,
8.1, 1.4 Hz, 1H), 2.88–3.08 (m, 3H), 4.59–4.71 (m, 2H), 5.22
(s, 1H), 7.30–7.35 (m, 3H), 7.51–7.57 (m, 2H); 13C NMR
(125 MHz, CDCl3): d=À2.02, À1.64, 16.2, 16.3, 21.22, 21.27,
22.35, 22.36, 23.35, 23.42, 25.1, 25.3, 25.6, 26.2, 31.7, 34.6,
38.3, 40.7, 40.9, 41.9, 44.7, 47.16, 47.22, 59.9, 75.69, 75.71,
Vinylboronates 7 and 5a
PdACHTNURTGNEGNU(PPh3)4 (23.11 mg, 0.02 mmol), sodium carbonate
(106 mg, 1.00 mmol), ethanol (0.8 mL), distilled water
(0.8 mL) and aryl bromide (0.24 mmol) were added to a so-
lution of vinylboronate 7 or 5a (1.0 equiv., 0.20 mmol) in tol-
uene (2.4 mL) in a Schlenk tube under a nitrogen atmos-
phere. The reaction mixture was heated for 18 h to 808C,
and then taken up in dichloromethane (10 mL), and the or-
ganic layer was separated. The aqueous phase was extracted
with dichloromethane (2ꢁ10 mL), and the combined organ-
ic layers dried over MgSO4, filtered, and the solvent re-
moved under reduced pressure. The products were purified
by column chromatography furnishing the corresponding
pyrrolidines 12a–i or cyclopentanes 13a and b.
(E)-3-Benzylidene-4-[(dimethylphenylsilyl)methyl]-1-
83.1, 110.1 (br), 128.0, 129.1, 133.9, 140.1, 171.3, 171.6, 173.9; tosylpyrrolidine (12a)
anal. calcd. for C43H69BO6Si: C 71.64, H 9.65; found: C
71.55, H 9.79%
Compound 12a was isolated after flash chromatography on
silica gel (pentane:Et2O=5:1, Rf =0.17) as a yellow oil;
yield: 87%. 1H NMR (500 MHz, CDCl3): d=0.28 (s, 3H),
0.32 (s, 3H), 0.80–0.95 (m, 2H), 2.42 (s, 3H), 3.07–3.15 (m,
3H), 3.81 (dd, J=13.7, 1.7 Hz, 1H), 4.12 (d, J=13.7 Hz,
1H), 6.15 (s, 1H), 6.99–7.04 (m, 2H), 7.14–7.18 (m, 3H),
7.31 (d, J=8.1 Hz, 2H), 7.37–7.42 (m, 3H), 7.42–7.46 (m,
2H), 7.69 (d, J=8.1 Hz, 2H); 13C NMR (125 MHz, CDCl3):
d=À2.6, À2.5, 20.0, 21.5, 36.0, 52.8, 54.8, 121.2, 126.8, 127.8,
128.0, 128.1, 128.3, 129.3, 129.6, 133.0, 133.6, 136.2, 138.0,
143.5, 143.7.
Minor isomer: Rf =0.28 (10% Et2O/pentane). 1H NMR
500 MHz, (CDCl3): d=0.326 (s, 3H), 0.331 (s, 3H), 0.66 (d,
J=6.9 Hz, 3H), 0.70 (d, J=6.9 Hz, 3H), 0.80–0.92 (m,
18H), 0.94–1.1 (m, 2H), 1.20 (s, 6H), 1.22 (s, 6H), 1.27–1.37
(m, 2H), 1.40–1.50 (m, 4H), 1.60–1.95 (m, 9H), 2.70 (ddd,
J=12.9, 8.2, 1.7 Hz, 1H), 2.74 (d, J=16.7 Hz, 1H), 3.07–3.17
(m, 1H), 3.22 (app. dt, J=15.5, 2.2 Hz, 1H), 4.60–4.72 (m,
2H), 5.17 (s, 1H), 7.31–7.35 (m, 3H), 7.51–7.56 (m, 2H);
13C NMR (125 MHz, CDCl3) d=À1.95, À1.65, 16.3, 16.5,
21.12, 21.21, 22.36, 22.40, 23.34, 23.6, 25.1, 25.3, 26.1, 26.2,
26.4, 31.7, 34.6, 38.3, 40.9, 41.0, 42.0, 45.0, 47.3, 47.4, 60.1,
75.4, 75.5, 83.1, 128.0, 129.1, 133.9, 140.0, 171.0, 171.4, 173.4.
(E)-3-[(Dimethylphenylsilyl)methyl]-4-(4-methoxy-
benzylidene)-1-tosylpyrrolidine (12b)
Compound 12b was isolated after flash chromatography on
silica gel (pentane:Et2O=4:1, Rf =0.15) as a yellow oil;
yield: 77%. 1H NMR (500 MHz, CDCl3): d=0.28 (s, 3H),
0.34 (s, 3H), 0.80–0.95 (m, 2H), 2.42 (s, 3H), 3.05–3.14 (m,
3H), 3.75–3.80 (m, 4H), 4.10 (d, J=13.6 Hz, 1H), 6.07 (s,
1H), 6.64–6.68 (m, 2H), 6.90–6.94 (m, 2H), 7.31 (d, J=
8.0 Hz, 2H), 7.37–7.44 (m, 3H), 7.45–7.48 (m, 2H), 7.68 (d,
(Z)-3-[(Dimethylphenylsilyl)methyl]-4-[(4,4,5,5-
tetramethyl-1,3,2-dioxaborolan-2-yl)methylene]cyclo-
pentane-1,1-dicarboxylic Acid Bis-[(À)-8-
phenylmenthol] Ester (5d)
The reaction was performed using 1.2 equiv. of enyne 1d
and 5 mol% Pd-PEPPSI-IPr catalyst at 508C for 24 h, yield-
2566
asc.wiley-vch.de
ꢀ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Adv. Synth. Catal. 2010, 352, 2559 – 2570

Regioselective Preparation of Functionalized exo-Methylenecyclopentanes and exo-Methylenepyrrolidines
J=8.2 Hz, 2H); 13C NMR (125 MHz, CDCl3): d=À2.6,
À2.4, 19.9, 21.5, 35.9, 52.8, 54.9, 55.2, 113.7, 120.5, 127.7,
128.0, 128.8, 129.2, 129.3, 129.6, 133.0, 133.6, 138.1, 141.5,
143.5, 158.3.
CDCl3) d=À2.7, À2.5, 20.1, 21.5, 36.0, 52.8, 54.8, 120.0,
127.8, 128.0, 128.4, 129.3, 129.4, 129.6, 132.4, 132.9, 133.5,
134.6, 137.8, 143.6, 144.6.
(E)-3-{[4-[(Dimethylphenylsilyl)methyl]-1-tosyl-
pyrrolidin-3-ylidene}methyl]pyridine (12g)
(E)-3-[(Dimethylphenylsilyl)methyl]-4-(3-methoxy-
benzylidene)-1-tosylpyrrolidine (12c)
Compound 12g was isolated after flash chromatography on
silica gel (pentane:EtOAc=1:1, Rf =0.26) as a colorless oil;
yield: 77%. 1H NMR (500 MHz, CDCl3) d=0.28 (s, 3H),
0.31 (s, 3H), 0.79–0.93 (m, 2H), 2.42 (s, 3H), 3.00–3.08 (m,
1H), 3.09–3.17 (m, 2H), 3.81 (dd, J=14.1, 1.5 Hz, 1H), 4.12
(d, J=14.1 Hz, 1H), 6.11 (s, 1H), 6.99 (dd, J=7.9, 4.8 Hz
,1H), 7.19–7.23 (m, 1H), 7.32 (d, J=8.1 Hz, 2H), 7.35–7.45
(m, 5H), 7.68 (d, J=8.2 Hz, 2H), 8.34–8.36 (m, 1H), 8.37–
8.40 (m, 1H); 13C NMR (125 MHz, CDCl3) d=À2.7, À2.6,
20.2, 21.5, 36.2, 52.8, 54.7, 117.5, 123.1, 127.8, 128.0, 129.4,
129.7, 131.9, 132.8, 133.5, 134.4, 137.7, 143.7, 146.7, 147.7,
149.6.
Compound 12c was isolated after flash chromatography on
silica gel (pentane:Et2O=4:1, Rf =0.15) as a yellow oil;
yield: 78%. 1H NMR (500 MHz, CDCl3): d=0.28 (s, 3H),
0.30 (s, 3H), 0.81–0.88 (m, 1H), 0.93 (d, J=15.0 Hz, 1H),
2.42 (s, 3H), 3.05–3.16 (m, 3H), 3.76 (s, 3H), 3.80 (dd, J=
13.8, 1.1 Hz, 1H), 4.09 (d, J=13.8 Hz, 1H), 6.13 (s, 1H),
6.62 (d, J=7.7 Hz, 1H), 6.64–6.66 (m, 1H), 6.72–6.75 (m,
1H), 7.05–7.09 (m, 1H), 7.31 (d, J=8.0 Hz, 2H), 7.35–7.44
(m, 5H), 7.68 (d, J=8.2 Hz, 2H); 13C NMR (125 MHz,
CDCl3): d=À2.6, À2.5, 20.0, 21.5, 36.2, 52.8, 54.8, 55.1,
111.9, 114.4, 120.2, 121.1, 127.7, 127.9, 129.2, 129.3, 129.6,
132.9, 133.5, 137.6, 138.1, 143.6, 144.2, 159.6.
(E)-3-[(Dimethylphenylsilyl)methyl]-1-tosyl-4-(2,4,6-
trimethylbenzylidene)pyrrolidine (12h)
(E)-3-[(Dimethylphenylsilyl)methyl]-4-(2-methoxy-
benzylidene)-1-tosylpyrrolidine (12d)
Compound 12h was isolated after flash chromatography on
silica gel (pentane:Et2O=9:1, Rf =0.10) as a yellow oil;
yield: 77%. 1H NMR (500 MHz, CDCl3): d=0.01 (s, 3H),
0.02 (s, 3H), 0.46–0.52 (m, 2H), 2.02 (br s, 6H), 2.29 (s, 3H),
2.41–2.49 (m, 4H), 2.79 (dd, J=9.8, 4.2 Hz, 1H), 3.23 (dd,
J=9.8, 7.0 Hz, 1H), 3.91–4.01 (m, 2H), 6.13 (s, 1H), 6.82 (s,
2H), 7.09–7.12 (m, 2H), 7.24–7.28 (m, 2H), 7.31–7.35 (m,
3H), 7.68 (d, J=8.1 Hz, 2H); 13C NMR (125 MHz, CDCl3):
d=À3.0, À2.8, 18.9, 20.1, 20.9, 21.5, 36.9, 51.8, 54.9, 120.0,
127.7, 127.8, 128.0, 128.9, 129.6, 132.7, 132.8, 133.2, 135.3,
136.3, 138.0, 143.5, 144.2.
Compound 12d was isolated after flash chromatography on
silica gel (pentane:Et2O=4:1, Rf =0.15) as a yellow oil;
yield: 80%. 1H NMR (500 MHz, CDCl3): d=0.22 (s, 3H),
0.25 (s, 3H), 0.70–0.77 (m, 1H), 0.87 (d, J=15.0 Hz, 1H),
2.42 (s, 3H), 2.97 (d, J=9.7 Hz, 1H), 3.03–3.09 (m, 1H),
3.16–3.21 (m, 1H), 3.77 (s, 3H), 3.89 (d, J=13.7 Hz, 1H),
4.07 (d, J=13.6 Hz, 1H), 6.39 (s, 1H), 6.70–6.75 (m, 1H),
6.82 (d, J=8.2 Hz, 1H), 6.95 (d, J=7.5 Hz, 1H), 7.16–7.21
(m, 1H), 7.31 (d, J=7.9 Hz, 2H), 7.33–7.41 (m, 5H), 7.66
(d, J=7.9 Hz, 2H); 13C NMR (125 MHz, CDCl3): d=À2.7,
À2.6, 19.9, 21.5, 36.0, 52.8, 54.9, 55.3, 110.4, 116.3, 120.2,
125.3, 127.8, 127.9, 128.2, 128.7, 129.1, 129.6, 133.1, 133.5,
138.1, 143.4, 143.6, 156.5.
(E)-3-[(Dimethylphenylsilyl)methyl]-4-(naphthalen-1-
ylmethylene)-1-tosylpyrrolidine (12i)
Compound 12i was isolated after flash chromatography on
silica gel (pentane:Et2O=5:1, Rf =0.13) as a colorless oil;
yield: 86%. H NMR (500 MHz, CDCl3): d=0.016 (s, 3H),
(E)-4-{[(4-Dimethylphenylsilyl)methyl-1-tosyl-
pyrrolidin-3-ylidene]methyl}benzonitrile (12e)
1
0.020 (s, 3H), 0.59–0.69 (m, 2H), 2.45 (s, 3H), 2.88–2.98 (m,
2H), 3.21 (dd, J=9.6, 6.4 Hz, 1H), 4.06 (dd, J=13.6, 1.4 Hz,
1H), 4.14–4.18 (m, 1H), 6.72 (s, 1H), 7.12–7.16 (m, 3H),
7.24–7.37 (m, 6H), 7.45–7.52 (m, 2H), 7.72 (d, J=8.1 Hz,
2H), 7.75 (d, J=8.2 Hz, 1H), 7.82 (d, J=8.2 Hz, 1H), 7.84–
7.87 (m, 1H); 13C NMR (125 MHz, CDCl3): d=À2.9, À2.8,
20.3, 21.5, 36.2, 52.5, 54.9, 119.3, 124.4, 125.2, 125.7, 125.9,
126.0, 127.5, 127.76, 128.80, 128.4, 129.0, 129.7, 131.4, 133.0,
133.3, 133.5, 133.8, 137.9, 143.6, 145.9.
Compound 12e was isolated after flash chromatography on
silica gel (pentane:Et2O=2:1, Rf =0.14) as a yellow oil;
yield: 83%. 1H NMR (500 MHz, CDCl3): d=0.27 (s, 3H),
0.34 (s, 3H), 0.76–0.91 (m, 2H), 2.42 (s, 3H), 3.01–3.07 (m,
3H), 3.12–3.19 (m, 2H), 3.80 (dd, J=14.4, 1.6 Hz, 1H),
4.12–4.16 (m, 1H), 6.12 (s, 1H), 7.01 (d, J=8.3 Hz, 2H),
7.31–7.35 (m, 2H), 7.38–7.48 (m, 5H), 7.68–7.71 (m, 2H);
13C NMR (125 MHz, CDCl3) d=À2.7, À2.5, 20.2, 21.5, 36.2,
52.9, 54.7, 110.0, 118.7, 119.7, 127.8, 128.1, 128.4, 129.5,
129.7, 132.1, 132.8, 133.5, 137.6, 140.6, 143.8, 148.0.
(Z)-Diethyl 3-[(Dimethylphenylsilyl)methyl]-4-(4-
(E)-3-(4-Chlorobenzylidene)-4-[(dimethylphenylsilyl)- methoxybenzylidene)cyclopentane-1,1-dicarboxylate
methyl]-1-tosylpyrrolidine (12f)
(13a)
Compound 12f was isolated after flash chromatography on
silica gel (pentane:Et2O=5:1, Rf =0.14) as a yellow oil;
yield: 88%. 1H NMR (500 MHz, CDCl3): d=0.28 (s, 3H),
0.33 (s, 3H), 0.83–0.86 (m, 2H), 2.42 (s, 3H), 3.01–3.07 (m,
1H), 3.10–3.16 (m, 2H), 3.78 (dd, J=13.9, 1.4 Hz, 1H),
4.08–4.12 (m, 1H), 6.08 (s, 1H), 6.90 (d, J=8.5 Hz, 2H),
7.08 (d, J=8.5 Hz, 2H), 7.32 (d, J=8.0 Hz, 2H), 7.38–7.45
(m, 5H), 7.69 (d, J=8.2 Hz, 2H); 13C NMR (125 MHz,
Compound 13a was isolated after flash chromatography on
silica gel (pentane:Et2O=10:1, Rf =0.12) as a colorless oil;
yield: 80%. 1H NMR (500 MHz, CDCl3): d=0.31 (s, 3H),
0.36 (s, 3H), 0.81 (dd, J=14.9, 12.4 Hz, 1H), 1.15–1.27 (m,
7H), 1.87 (dd, J=13.3, 5.7 Hz, 1H), 2.68 (ddd, J=13.3, 8.1,
1.2 Hz, 1H), 2.88 (d, J=15.6 Hz, 1H), 3.13–3.22 (m, 1H),
3.25 (app. dt, J=15.6, 2.2 Hz, 1H), 3.79 (s, 3H), 4.08–4.26
(m, 4H), 6.16 (s, 1H), 6.67–6.72 (m, 2H), 6.98–7.03 (m, 2H),
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Martin Gerdin et al.
FULL PAPERS
7.35–7.40 (m, 3H), 7.47–7.51 (m, 2H); 13C NMR (125 MHz,
CDCl3) d=À2.4, À2.2, 14.0, 21.7, 35.4, 42.1, 42.8, 55.2, 58.5,
61.4, 61.5, 113.5, 120.7, 127.8, 129.0, 129.4, 129.9, 133.6,
138.8, 146.6, 157.8, 171.6, 172.0; anal. calcd. for C28H36O5Si:
C 69.97, H 7.55; found: C 69.62, H 7.55%
J=14 Hz, 1H), 0.85 (app. t, J=14 Hz, 1H), 1.14 (d, J=
6.1 Hz, 3H), 1.17 (d, J=6.1 Hz, 3H), 1.20 (s, 12H), 2.40 (s,
3H), 3.07 (dd, J=9, 6.7 Hz, 1H), 3.18–3.23 (m, 1H), 3.48 (d,
J=9 Hz, 1H), 3.59 (d, J=15.2, 1.4 Hz, 1H), 3.98 (sept, J=
6.1 Hz, 1H), 4.06 (d, J=15.2 Hz, 1H), 5.09 (s, 1H), 7.30 (d,
J=8.1 Hz, 2H), 7.69 (d, J=8.1 Hz, 2H); 13C NMR
(125 MHz, CDCl3): d=À0.57, À0.22, 21.8, 24.1, 25.0, 25.2,
26.15, 26.19, 39.1, 53.6, 54.4, 65.3, 83.4, 128.3, 129.9, 133.1,
143.8, 168.3.
(Z)-Diethyl 3-(4-Cyanobenzylidene)-4-[(dimethyl-
phenylsilyl)methyl]cyclopentane-1,1-dicarboxylate
(13b)
Compound 13b was isolated after flash chromatography on (E)-Diethyl 3-[(Chlorodimethylsilyl)methyl]-4-
silica gel (pentane:Et2O=8:1, Rf =0.13) as a colorless oil;
yield: 85%. 1H NMR (400 MHz, CDCl3): d=0.29 (s, 3H),
0.36 (s, 3H), 0.82 (dd, J=14.9, 12.4 Hz, 1H), 1.02 (dd, J=
14.9, 1.8 Hz 1H), 1.22 (t, J=7.1 Hz, 3H), 1.26 (t, J=7.1 Hz,
3H), 1.93 (dd, J=13.3, 5.6 Hz, 1H), 2.70 (ddd, J=13.3, 8.1,
1.2 Hz, 1H), 2.92 (d, J=16.1 Hz, 1H), 3.10–3.20 (m, 1H),
3.30 (app. dt, J=6.1, 2.2 Hz, 1H), 4.10–4.28 (m, 4H), 6.21 (s,
1H), 7.09 (d, J=8.3 Hz, 2H), 7.35–7.43 (m, 5H), 7.44–7.48
(m, 2H); 13C NMR (100 MHz, CDCl3): d=À2.5, À2.3, 14.0,
22.2, 35.8, 41.9, 43.0, 58.3, 61.6, 61.7, 109.2, 119.1, 120.0,
128.0, 128.6, 129.3, 131.9, 133.6, 138.2, 141.7, 153.4, 171.4,
171.6.
[(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-
methylene]cyclopentane-1,1-dicarboxylate (16)
The solvent was removed under reduced pressure and the
residue analyzed by 1H NMR spectroscopy. 1H NMR
(500 MHz, CDCl3): d=0.46 (s, 3H), 0.48 (s, 3H), 0.99 (br t,
J=14 Hz, 1H), 1.18–1.29 (m, 18H), 1.46 (d, J=14 Hz, 1H),
2.00 (dd, J=13.5, 5.8 Hz, 1H), 2.71 (dd, J=13.5, 8.5 Hz,
1H), 2.83 (d, J=16.7 Hz, 1H), 3.15–3.22 (m, 1H), 3.25 (dd,
J=16.7, 1.8 Hz, 1H), 4.10–4.27 (m, 4H), 5.24 (br s, 1H).
(E)-Diethyl 3-[(Isopropoxydimethylsilyl)methyl]-4-
[(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-
yl)methylene]cyclopentane-1,1-dicarboxylate (18)
General Procedure for Silaborative Carbocyclization
of Enynes 6 and 1a using Chlorosilylborane 14
The reaction was performed with enyne 1a using 5 mol%
Pd-PEPPSI-IPr catalyst at room temperature for 18 h. After
flash chromatography on SiO2 (5% ethyl acetate in hexane),
the product was isolated as a highly viscous oil; overall
yield: 188 mg (0.39 mmol, 78%). 1H NMR (500 MHz,
CDCl3): d=0.15 (s, 3H), 0.17 (s, 3H), 0.77 (dd, J=14.3,
12.8 Hz, 1H), 1.14 (d, J=6 Hz, 6H), 1.20–1.27 (m, 19H),
1.95 (dd, J=13.6, 6.1 Hz, 1H), 2.72 (dd, J=13.6, 8.3 Hz,
1H), 2.80 (d, J=16.4 Hz, 1H), 3.07- 3.16 (m, 1H), 3.27 (app.
dt, J=16.4, 2.2 Hz, 1H), 4.00 (sept, J=6 Hz, 1H), 4.00–4.23
(m, 4H), 5.20 (br s, 1H); 13C NMR (125 MHz, CDCl3) d=
À0.29, À0.06, 14.37, 14.41, 25.16, 25.24, 25.33, 26.20, 26.23,
26.29, 38.1, 41.3, 44.3, 59.3, 61.75, 61.82, 65.1, 83.1, 172.0,
172.4, 173.8.
The reactions were run in 0.5 mmol scale as described for si-
laborations using 4 except that the reaction mixture was
stirred at room temperature for 18 h. After the reaction was
completed, propan-2-ol (38 mL, 0.5 mmol) and triethylamine
(139 mL, 1.0 mmol) were added and the reaction mixture
stirred for 1 h at room temperature. Then, the reaction mix-
ture was filtered through a column filled with silica gel using
diethyl ether as eluent to afford the crude product. Purifica-
tion was performed by adding the crude product onto a
SiO2 column and eluting with an appropriate eluent. Phos-
phomolybdic acid (for reactions with 6) and KMnO4 (for re-
actions with 1a) were used to develop TLC plates.
(E)-3-[(Chlorodimethylsilyl)methyl]-4-[(4,4,5,5-tetra-
methyl-1,3,2-dioxaborolan-2-yl)methylene]-1-
tosylpyrrolidine (15)
General Procedure for Suzuki Cross-Coupling of
Vinylboronates 17 and 18
The reactions were run as described for vinylboronates 7
and 5a using PdACTHUNTRGNE(UNG PPh3)4 (23.11 mg, 0.02 mmol), sodium car-
A sample (20 mL) was taken from the reaction mixture prior
to the addition of propan-2-ol. The solvent was removed
under reduced pressure and the residue analyzed by
bonate (106 mg, 1.00 mmol), ethanol (0.8 mL), distilled
water (0.8 mL), 4-bromobenzonitrile (40 mg, 0.22 mmol)
and vinylboronate 17 or 18 (0.20 mmol) in toluene (2.4 mL)
at 808C. The crude products obtained (a mixture of 19a and
b or cyclopentane 20) were used for the next step without
further purification.
1
1H NMR spectroscopy. H NMR (500 MHz, CDCl3): d=0.45
(s, 3H), 0.46 (s, 3H), 0.9–1.1 (m, 2H), 1.22 (s, 12H), 2.43 (s,
3H), 3.10 (dd, J=9.6, 6.3 Hz, 1H), 3.28–3.32 (m, 1H), 3.43
(d, J=9.6 Hz, 1H), 3.60 (d, J=15.2 Hz, 1H), 4.09 (d, J=
15.2 Hz, 1H), 5.15 (s, 1H), 7.33 (d, J=8.1 Hz, 2H), 7.70 (d,
J=8.1 Hz, 2H).
(E)-4-{[4-(Isopropoxydimethylsilyl)methyl-1-tosyl-
pyrrolidin-3-ylidene]methyl}benzonitrile (19a)
(E)-3-[(Isopropoxydimethylsilyl)methyl]-4-[(4,4,5,5-
tetramethyl-1,3,2-dioxaborolan-2-yl)methylene]-1-
tosylpyrrolidine (17)
A small portion of the crude reaction mixture was taken,
and the product purified by flash chromatography (20–50%
1
ethyl acetate in hexane). H NMR (400 MHz, CDCl3): d=
After flash chromatography on SiO2 (20% ethyl acetate in
hexane), the product was isolated as a highly viscous oil;
overall yield: 217 mg (0.44 mmol, 89%). 1H NMR
(500 MHz, CDCl3): d=0.09 (s, 3H), 0.15 (s, 3H), 0.65 (d,
0.10 (s, 3H), 0.11 (s, 3H), 0.60–0.75 (m, 2H), 1.15 (d, J=
6.0 Hz, 3H), 1.16 (d, J=6.0 Hz, 3H), 2.43 (s, 3H), 3.18–3.23
(m, 2H), 3.39–3.44 (m, 1H), 3.82 (dd, J=14.4, 1.7 Hz, 1H),
3.98 (sept, J=6.0 Hz, 1H), 4.17 (d, J=14.4 Hz, 1H), 6.17 (s,
2568
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Adv. Synth. Catal. 2010, 352, 2559 – 2570

Regioselective Preparation of Functionalized exo-Methylenecyclopentanes and exo-Methylenepyrrolidines
1H), 7.33 (m, 4H), 7.57 (d, J=8.3 Hz, 2H), 7.74 (d, J=
8.3 Hz, 2H); 13C NMR (125 MHz, CDCl3): d=À0.46, À0.37,
21.3, 21.9, 26.2, 26.3, 36.2, 53.4, 55.2, 65.6, 110.5, 119.2, 119.9,
128.2, 129.1, 130.1, 132.5, 133.3, 141.2, 144.1, 148.8.
(E)-Diethyl 3-(4-Cyanobenzylidene)-4-(hydroxy-
methyl)cyclopentane-1,1-dicarboxylate (22)
After flash chromatography on SiO2 (20–50% ethyl acetate
in hexane), the product was isolated as a highly viscous oil;
yield: 43 mg (0.12 mmol, 60% based on 19). 1H NMR
(500 MHz, CDCl3): d=1.25 (t, J=7.1 Hz, 3H), 1.27 (t, J=
7.1 Hz, 3H), 1.56 (s, 1H), 2.36 (dd, J=13.7, 4.9 Hz, 1H),
2.65 (dd, J=13.7, 7.5 Hz, 1H), 3.07 (A part of ABX, J=
16.6 Hz, JX =0 Hz, 1H), 3.21 (B part of ABX, J=16.6 Hz,
JX =2 Hz, 1H), 3.4–3.5 (m, 2H), 3.58–3.67 (m, 1H), 4.18–
4.27 (m, 4H), 6.49 (s, 1H), 7.28 (d, J=8.3 Hz, 2H), 7.75 (d,
J=8.3 Hz, 2H); 13C NMR (125 MHz, CDCl3): d=1.33,
14.34, 37.52, 43.25, 43.88, 58.39, 62.01, 62.10, 63.68, 123.87,
127.94, 128.45, 131.50, 141.28, 144.87, 169.73, 171.94,
172.22 ppm.
(E)-4-{[(4-(Hydroxydimethylsilyl)methyl-1-tosyl-
pyrrolidin-3-ylidene]methyl}benzonitrile (19b)
The formation of this compound could be avoided by
adding ethanol and water after heating the reaction mixture
1
to 808C. H NMR (500 MHz, CDCl3): d=0.14 (s, 3H), 0.15
(s, 3H), 0.70 (d, J=15.0 Hz, 1H), 0.85 (dd, J=15.0, 11.3 Hz,
1H), 2.1 (br s, 1H), 2.43 (s, 3H), 3.13 (dd, J=9.6, 6.1 Hz,
1H), 3.27 (m, 1H), 3.48 (d, J=9.6 Hz, 1H), 3.76 (d, J=
14 Hz, 1H), 4.22 (d, J=14 Hz, 1H), 6.19 (s, 1H), 7.30–7.35
(m, 4H), 7.57 (d, J=8.2 Hz, 2H), 7.73 (d, J=8.2 Hz, 2H).
Supporting Information
(E)-Diethyl 3-(4-Cyanobenzylidene)-4-[(isopropoxy-
dimethylsilyl)methyl]cyclopentane-1,1-dicarboxylate
(20)
Experimental procedures for the preparation of compounds
1
1c, 1d, and 8 and H and 13C NMR spectra for all new com-
pounds are presented in the Suppoprting Information. This
material is also available free of charge from the corre-
sponding author.
A small portion of the crude reaction mixture was taken,
and the product purified by flash chromatography (20–50%
ethyl acetate in hexane). H NMR (500 MHz, CDCl3): d=
1
0.11 (s, 3H), 0.13 (s, 3H), 0.65 (dd, J=15.0, 12.3 Hz, 1H),
0.90 (dd, J=15.0, 1.6 Hz, 1H), 1.14 (app t, J=6.1 Hz, 6H),
1.23 (t, J=7.1 Hz, 3H), 1.27 (t, J=7.1 Hz, 3H), 2.03 (dd, J=
13.6, 5.9 Hz, 1H), 2.83–2.73 (m, 1H), 2.95 (d, J=16.0 Hz,
1H), 3.25–3.39 (m, 2H), 3.95 (sept, J=6.1 Hz, 1H), 4.12–
4.29 (m, 4H), 6.26 (s, 1H), 7.36 (d, J=8.3 Hz, 2H), 7.56 (d,
J=8.3 Hz, 2H); 13C NMR (CDCl3) d=À0.33, À0.15, 14.4,
22.9, 26.16, 26.24, 35.6, 42.2, 43.4, 58.6, 61.9, 62.0, 65.3, 109.7,
119.5, 120.3, 129.2, 132.3, 142.3, 153.9, 171.8, 172.0.
Acknowledgements
This work was supported by the Swedish Research Council,
the Carl Trygger Foundation for Scientific Research, and the
Deutscher Akademischer Austausch Dienst (DAAD). We are
grateful to Sigma–Aldrich for a generous gift of Pd-PEPPSI-
IPr. We would also like to thank Georgios Passas-Lagos for
his efforts in the initial stages of this project.
General Procedure for Oxidation of the Silyl Group
To a solution of crude products 19a, b or 20 in DMF (2 mL)
were successively added solid KF (0.8 mmol, 4 equiv.) and
50% H2O2 aqueous solution (2.4 mmol, 12 equiv.) at room
temperature. The reaction mixture was stirred overrnight at
room temperature, then diluted with H2O and extracted
with Et2O. The extract was successively washed with 1M
Na2S2O3 solution and H2O and dried over MgSO4. The sol-
vent was removed by evaporation, followed by flash chro-
matography on silica gel to give alcohols 21 or 22.
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Adv. Synth. Catal. 2010, 352, 2559 – 2570