Lewis acid or Bronsted acid catalyzed reactions of vinylidene cyclopropanes with activated carbon-nitrogen, nitrogen-nitrogen, and iodine-nitrogen double-bond-containing compounds

Article abstract of DOI:10.1002/chem.200801785

Lewis acid or Bronsted acid catalyzed reactions of vinylidene cyclopropanes (VDCPs), 1, with activated carbon-nitrogen, nitrogen-nitrogen, and iodine-nitrogen double-bond-containing compounds have been thoroughly investigated. We found that pyrrolidine an

Full text of DOI:10.1002/chem.200801785

FULL PAPER
DOI: 10.1002/chem.200801785
Lewis Acid or Brønsted Acid Catalyzed Reactions of Vinylidene
Cyclopropanes with Activated Carbon–Nitrogen, Nitrogen–Nitrogen, and
Iodine–Nitrogen Double-Bond-Containing Compounds
Jian-Mei Lu, Zhi-Bin Zhu, and Min Shi*[a]
Abstract: Lewis acid or Brønsted acid
catalyzed reactions of vinylidene cyclo-
propanes (VDCPs), 1, with activated
ed carbon–nitrogen and nitrogen–nitro-
gen double-bond-containing com-
used as the substrate, six-membered cy-
cloaddition products 10 and 11 were
formed in moderate yields in the pres-
ence of a Brønsted acid, trifluorome-
thanesulfonic acid (TfOH). The reac-
tions of VDCPs 1 with N-Ts-iminophe-
nyliodinane (12) were also carried out
in the presence of (CuOTf)2·C6H6 and
it was found that nitrogen-containing
indene derivatives 13 were obtained,
rather than the aziridination products.
Plausible mechanisms for all of these
transformations are discussed, based on
the obtained results.
pounds, such as N-toluene-4-sulfonyl
(N-Ts) imines 5 and diisopropylazodi-
carboxylate (7), can also react with
VDCPs 1 to give [3+2] cycloaddition
products in moderate to good yields in
the presence of a Lewis acid. When N-
carbon–nitrogen,
nitrogen–nitrogen,
and iodine–nitrogen double-bond-con-
taining compounds have been thor-
oughly investigated. We found that pyr-
rolidine and 1,2,3,4-tetrahydroquino-
line derivatives can be formed in good
yields in the reactions of VDCPs 1
with ethyl (arylimino)acetates 2 by a
[3+2] cycloaddition or intramolecular
Friedel–Crafts reaction pathway. Based
on these results, we found that activat-
tert-butoxycarbonyl aldimine
9 was
Keywords: Brønsted acids · cyclo-
additions · imines · indenes · Lewis
acids · vinylidene cyclopropanes
Introduction
VDCPs 1 with nitriles, mediated by a Brønsted acid, namely
trifluoromethanesulfonic acid (TfOH).[3] Moreover, Stepa-
kov et al. recently reported reactions of VDCPs 1 with aro-
matic imines in the presence of a Lewis acid to give [3+2]
cycloaddition products.[4] At the same time, we found that,
in the Lewis acid catalyzed reactions of aryl VDCPs 1 with
ethyl (arylimino)acetates 2, pyrrolidine and 1,2,3,4-tetrahy-
droquinoline derivatives were prepared selectively in moder-
ate to good yields depending on the electronic nature of 1
and 2. For example, the corresponding [3+2] cycloaddition
products 3, pyrrolidine derivatives, were obtained in moder-
ate to good yields when R5 was an electron-poor aromatic
group, whereas 1,2,3,4-tetrahydroquinoline derivatives 4, de-
rived from an intramolecular Friedel–Crafts reaction, were
formed when R5 was an electron-rich aromatic group
(Scheme 1).[5] In the continuing investigations, we found that
both [3+2] cycloaddition product 3a and intramolecular
Friedel–Crafts reaction product 4a were obtained in the
presence of a Lewis acid when R1 and R2 were both elec-
tron-rich aromatic groups (R1 =R2 =p-MeC6H4) and R5 was
Vinylidene cyclopropanes (VDCPs) 1,[1] which contain an
allene moiety and a connected cyclopropane ring, are one of
the most remarkable known organic compounds in the
chemistry of highly strained small rings. It is already known
that these highly strained cyclopropanes are thermally stable
and yet reactive substances, which can easily react with
carbon–carbon or carbon–heteroatom multiple bonds to
produce [3+2] or [2+2] cycloaddition products in good
yields upon heating or photoirradiation.[2] For example, very
recently, we reported [3+2] cycloaddition reactions of
[a] Dr. J.-M. Lu, Z.-B. Zhu, Prof. Dr. M. Shi
State Key Laboratory of Organometallic Chemistry
Shanghai Institute of Organic Chemistry
Chinese Academy of Sciences
354 Fenglin Road, Shanghai 200032 (China)
Fax : (+86)21-6416-6128
E-mail: Mshi@mail.sioc.ac.cn
an
electron-poor
aromatic
group
(R5 =p-BrC6H4;
Supporting information for this article (spectroscopic data for all new
compounds shown in Tables 1–6, detailed descriptions of experimen-
tal procedures, and X-ray data for compounds 6e, 10a, and 13a) is
available on the WWW under http://dx.doi.org/10.1002/
chem.200801785.
Scheme 2). Furthermore, we also disclosed the Lewis acid
catalyzed reactions of VDCPs 1 with an activated carbon–
oxygen double bond, which give the corresponding function-
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963

(PhI=NTs), could also react with VDCPs 1 in the presence
of Lewis acids or Brønsted acids to afford the cycloadducts
in moderate to good yields. Herein, we wish to disclose the
full details of these interesting cycloaddition reactions. Plau-
sible mechanisms for all of these transformations are dis-
cussed, based on the results obtained.
Results and Discussion
BF3·OEt2-catalyzed reactions of VDCPs 1 with ethyl (aryl-
imino)acetates 2: Initially, the reactions were carried out by
using VDCPs 1b and 1c (R1 and R2 are both electron-rich
aromatic groups) with ethyl (arylimino)acetates 2a and 2b
(R5 is an electron-poor aromatic group). Both the [3+2] cy-
cloaddition products 3 and 1,2,3,4-tetrahydroquinoline deriv-
atives 4 were obtained in good total yields from the reac-
tions in DCE at 608C in the presence of BF3·OEt2
(10 mol%; Table 1, entries 1–3). When ethyl (arylimino)ace-
tate 2c (R5 =p-Cl-o-MeC6H3) was used as the substrate, the
reaction with VDCP 1a gave 3e and 4e in 70 and 28%
yield, respectively (Table 1, entry 4). The reaction of 1b
with 2c gave 3 f and 4 f in 48 and 38% yield, respectively
(Table 1, entry 5). Interestingly, it should be noted that, as
reported in our previous short communication,[5] the reac-
tion of 1a with 2b (R5 =p-ClC6H4) exclusively gave the
[3+2] cycloaddition product under identical conditions,
which suggests that the electronic nature of 2 can signifi-
cantly affect the reaction outcome of this cascade cycloaddi-
tion. A plausible reaction mechanism for the formation of
cycloaddition products 3 and 4 is outlined in Scheme 4.
Firstly, ethyl (arylimino)acetate 2 is activated by BF3·OEt2
to afford intermediate A, which subsequently adds electro-
philically to the C1’ carbon atom of VDCP 1 to give the cor-
responding allylic carbocationic intermediates B-1 and B-2.
As long as one of the R1 and R2 groups is not an electron-
rich aromatic group and R5 is an electron-poor aromatic
group, then carbocationic intermediate B-2 is less stable
than if it had electron-rich groups, and an intramolecular
Friedel–Crafts reaction cannot easily take place with elec-
tron-poor aromatic groups as R5 in this case. This is why the
corresponding [3+2] cycloaddition products 3 are formed
exclusively if R1 or R2 and R5 are electron-poor aromatic
groups (Scheme 1).[5] If both R1 and R2 are electron-rich ar-
omatic groups, intermediate B-2 is more stable than if it had
electron-poor groups, and products 3 and 4 are both formed,
even when R5 is an electron-poor aromatic group
(Scheme 4). When R5 is an electron-rich aromatic group, the
intramolecular Friedel–Crafts reaction with R5 takes place
more easily, regardless of the electronic characters of the R1
Scheme 1. BF3·OEt2-catalyzed reactions of VDCPs 1 with ethyl (arylimi-
no)acetates 2. Ar: aryl; EWG: electron-withdrawing group; EDG: elec-
tron-donating group.
Scheme 2. BF3·OEt2-catalyzed reaction of VDCP 1b with ethyl (arylimi-
no)acetate 2a. DCE: 1,2-dichloroethane.
alized tetrahydrofuran and 3,6-dihydropyran derivatives in
moderate to good yields (Scheme 3).[6] These interesting re-
sults have stimulated us to further explore such cascade
ring-opening and cycloaddition processes with VDCPs as
the substrates. During our ongoing investigation of these cy-
cloaddition reactions, we found that activated carbon–nitro-
gen, nitrogen–nitrogen, and iodine–nitrogen double-bond-
containing compounds, such as N-toluene-4-sulfonyl (N-Ts)
imines 5, diisopropylazodicarboxylate (7), N-tert-butoxycar-
bonyl (N-Boc) aldimine 9, and N-Ts-iminophenyliodinane
and R2 groups, and only product
4 was obtained
(Scheme 1).[5] On the basis of the above results, the full de-
tails of BF3·OEt2-catalyzed reactions of VDCPs 1 with ethyl
(arylimino)acetates
2 have been disclosed (Scheme 5).
Therefore, a more comprehensive mechanistic insight can be
drawn. Intermediate B-1 undergoes [3+2] cycloaddition to
give product 3 through a cyclopropane-ring-opening process,
Scheme 3. Lewis acid catalyzed reactions of VDCPs 1 with an activated
carbon–oxygen double bond.
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Reactions of Vinylidene Cyclopropanes
FULL PAPER
Table 1. BF3·OEt2-catalyzed reactions of VDCPs 1 with ethyl (arylimino)acetates 2.[a]
[3+2] cycloaddition product 6a
was obtained exclusively in
92% yield in the presence of
BF3·OEt2 (10 mol%) within 1 h
(Table 2, entry 1). We did not
further optimize the reaction
conditions but directly exam-
ined a variety of VDCPs 1 with
N-Ts imines 5 under the same
conditions. As can been seen
from Table 2, with respect to
the electron-rich and electron-
poor VDCPs 1 (R1 and R2) and
N-Ts imines 5 (R7), the corre-
sponding [3+2] cycloaddition
products 6 were obtained in
moderate to good yields
(Table 2). With VDCP 1c,
which bears a strongly electron-
donating methoxy group on the
benzene ring, 6 f was obtained
in 64% yield along with 30%
Entry
1 (R1/R2)
2 (R5)
Product, yield[b] [%]
3
4
1
2
3
4
5
1b (p-MeC6H4/p-MeC6H4)
1c (p-MeOC6H4/p-MeOC6H4)
1c (p-MeOC6H4/p-MeOC6H4)
1a (C6H5/C6H5)
2b (p-ClC6H4)
2a (p-BrC6H4)
2b (p-ClC6H4)
2c (p-Cl-o-MeC6H3)
2c (p-Cl-o-MeC6H3)
3b, 62
3c, 51
3d, 55
3e, 70
3 f, 48
4b, 34
4c, 49
4d, 30
4e, 28
4 f, 38
1b (p-MeC6H4/p-MeC6H4)
[a] All reactions were carried out with 1 (0.2 mmol), 2 (0.3 mmol), and BF3·OEt2 (10 mol%) in DCE (2.0 mL)
at 608C. [b] Yield of isolated product.
of a rearrangement product, a naphthalene derivative, pre-
sumably due to the fact that the electron-rich VDCP 1c is
more labile in the presence of Lewis acid upon heating
(Table 2, entry 6).[7] For unsymmetrical VDCPs 1 f and 1g,
compounds 6i and 6j were obtained as E/Z isomeric mix-
tures in 87 and 76% yield, respectively (Table 2, entries 9
and 10). Alkyl VDCP 1h (R1, R2 =4-phenylcyclohexylene)
was also used as the substrate in this reaction. However,
none of the desired product was obtained in this case
(Table 2, entry 11). A plausible mechanism for the forma-
tion of products 6 is outlined in Scheme 6. Initially, N-Ts
imine 5 is activated by BF3·OEt2 to afford intermediate D,
which subsequently adds to the C1’ carbon atom of VDCP 1
to give the corresponding intermediate E. Ring opening of
intermediate E gives intermediate F, which affords [3+2] cy-
cloadduct 6 by cyclization (Scheme 6). The electron-defi-
cient Ts group is not suitable for an intramolecular Friedel–
Crafts reaction. Therefore, the six-membered nitrogen-con-
taining heterocyclic product could be not formed in this
case.
Further investigation revealed that the reaction of imine
5e with VDCP 1a not only gave the product 6k in 27%
yield, derived from [3+2] cycloaddition with the carbon–ni-
trogen double bond of 5e, but also afforded aldehyde 6l in
53% yield by cycloaddition with the carbon–carbon double
bond of 5e and subsequent hydrolysis of the imino group
(Scheme 7). The structure of product 6k was unambiguously
determined by X-ray diffraction and the ORTEP drawing is
presented in Figure 1.[8]
Scheme 4. Plausible reaction mechanism for the BF3·OEt2-catalyzed reac-
tions of VDCPs 1 with ethyl (arylimino)acetates 2.
whereas intermediate B-2 undergoes an intramolecular Frie-
del–Crafts reaction with the R5 aromatic group to give prod-
uct 4 (Scheme 4).
ScACTHNUGTRENNG(U OTf)3-catalyzed reactions of VDCPs 1 with diisopropyl-
BF3·OEt2-catalyzed reactions of VDCPs 1 with N-Ts imines
5: When N-benzylidene-4-methylbenzenesulfonamide (5a)
was used as the substrate instead of the ethyl (arylimino)-
acetates 2 in DCE at 608C, we found that the corresponding
azodicarboxylate (7): When the reaction of VDCP 1a with
diisopropylazodicarboxylate (DIAD; 7) was carried out in
the presence of BF3·OEt2 (10 mol%) in DCE at 608C, pyra-
zolidine derivative 8a was obtained in 65% yield within 1 h.
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965

M. Shi et al.
nism for the formation of prod-
ucts 8 is outlined in Scheme 8.
Initially, zwitterionic intermedi-
ate G was formed by the reac-
tion of DIAD and ScACHTUNGTRENNUNG
(OTf)3;[9]
this intermediate subsequently
adds to the C1’ carbon atom of
VDCP
1 to give the corre-
sponding cationic intermediate
H. Ring opening of intermedi-
ate H gives intermediate I. Cyc-
lization of intermediate I af-
fords the corresponding [3+2]
cycloadduct 8 (Scheme 8).
TfOH-catalyzed reactions of
VDCPs 1 with N-Boc aldimine
9: N-Boc aldimine derivatives
have been used widely as elec-
trophiles in various reactions
such as aza-Friedel–Crafts and
Mannich type reactions.[10] We
next attempted to use an N-Boc
aldimine as the substrate to
react with VDCPs under the
standard conditions. The initial
examination was carried out by
using VDCP 1a and N-Boc al-
dimine 9 as the substrates with
BF3·OEt2 (10 mol%) as the cat-
alyst. We found that six-mem-
bered cycloaddition products
10a and 11a were obtained in
Scheme 5. Full selectivity details of the BF3·OEt2-catalyzed reactions of VDCPs 1 with ethyl (arylimino)ace-
tates 2.
Table 2. BF3·OEt2-catalyzed reactions of VDCPs 1 with N-Ts imines 5.[a]
Entry
1
(R1/R2)
5 (R7)
Product
Yield[b]
[%]
1
2
3
4
5
6
7
8
9
1a
1a
1a
1a
1b
1c
1d
1e
1 f
1g
(C6H5/C6H5)
(C6H5/C6H5)
(C6H5/C6H5)
(C6H5/C6H5)
(p-MeC6H4/p-MeC6H4)
(p-MeOC6H4/p-MeOC6H4)
(p-ClC6H4/p-ClC6H4)
(p-FC6H4/p-FC6H4)
(C6H5/p-ClC6H4)
(C6H5/m-Me-p-MeC6H3)
5a (C6H5)
6a
6b
6c
6d
6e
6 f
6g
6h
6i
92
98
74
73
5b (p-BrC6H4)
5c (p-MeC6H4)
5d (o-HOC6H4)
5a (C6H5)
5a (C6H5)
5a (C6H5)
5a (C6H5)
5a (C6H5)
5a (C6H5)
82
64[c]
81
47–54% total yields with
a
85
ratio of 1.3:1 in DCE at 608C
or at 808C in DCE (Table 4, en-
tries 1–3). The structure of
product 10a was determined by
X-ray diffraction and the
ORTEP drawing is shown in
Figure 2.[11] Other Lewis acids,
87[d]
76[e]
10
6j
[f]
[f]
11
1h
5a (C6H5)
–
–
[a] All reactions were carried out with 1 (0.2 mmol), 5 (0.3 mmol), and BF3·OEt2 (10 mol%) in DCE (2.0 mL)
at 608C. [b] Yield of isolated product. [c] 30% of a rearrangement product was obtained:
[d] E/Z=[d] E/Z=1:1. [e] E/Z or Z/E=1.7:1. [f] No desired product was obtained.
.
such as Yb
ACHUTNGTRNENUG(OTf)3, ScACHTUNGTRENNUNG(OTf)3,
and Cu(OTf)2, were also used
AHCTUNGTRENNUNG
as the catalysts under the stan-
dard conditions. It was found
The screening of Lewis acids revealed that Sc
most effective catalyst for this reaction (Table 3, entry 1).
We next examined the reaction of an assortment of VDCPs
(OTf)3 is the
that all of the reactions proceeded smoothly to produce 10a
and 11a in moderate total yields (Table 4, entries 4–6).
When the Brønsted acid trifluoromethanesulfonic acid
(TfOH) was used as the catalyst, products 10a and 11a were
obtained in 70% total yield with a ratio of 1.2:1 (Table 4,
entry 7). Other Brønsted acids, such as TsOH, Tf2NH, and
CF3CO2H, were also used as the catalysts in this reaction
and these afforded the corresponding products in lower
total yields under otherwise identical conditions (Table 4,
entries 8–10). With the optimized reaction conditions in
hand (Table 4, entry 7), we next examined the reactions of a
variety of VDCPs 1 with N-Boc aldimine 9 in the presence
1 with DIAD by using ScACTHNUTRGNE(UGN OTf)3 (10 mol%) as the catalyst
and the results of these experiments are summarized in
Table 3. For VDCPs 1b, 1g and 1i, substituted with elec-
tron-rich aromatic groups, pyrazolidine derivatives 8b, 8e,
and 8 f were obtained in good yields (Table 3, entries 2, 5,
and 6). However, with VDCPs 1d and 1 f, substituted with
electron-poor aromatic groups, the reactions proceeded
slowly to give the corresponding adducts 8c and 8d in mod-
erate yields (Table 3, entries 3 and 4). A plausible mecha-
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Reactions of Vinylidene Cyclopropanes
FULL PAPER
Table 3. ScACTHNUTRGNEUNG
(OTf)3-catalyzed reactions of VDCPs 1 with DIAD (7).[a]
Entry
1 (R1/R2)
t [h]
Product
Yield[b] [%]
1
2
3
4
5
6
1a (C6H5/C6H5)
16
16
96
47
16
16
8a
8b
8c
8d
8e
8 f
76
84
1b (p-MeC6H4/p-MeC6H4)
1d (p-ClC6H4/p-ClC6H4)
1 f (C6H5/p-ClC6H4)
1g (C6H5/m-Me-p-MeC6H3)
1i (C6H5/p-MeC6H4)
45[c]
62[d]
88[d]
77[d]
Scheme 6. Plausible mechanism for the BF3·OEt2-catalyzed reactions of
VDCPs 1 with N-Ts imines 5.
[a] All reactions were carried out with 1 (0.2 mmol), DIAD (0.3 mmol),
Sc(OTf)3 (10 mol%), and DCE (2.0 mL). [b] Yield of isolated product.
AHCTUNGTRENNUNG
[c] 14% of 1d was recovered. [d] E/Z=1:1.
Scheme 7. BF3·OEt2-catalyzed reaction of VDCP 1a with N-Ts imine 5e.
Scheme 8. Plausible mechanism for the ScACHTNUTRGNEUNG(OTf)3-catalyzed reactions of
VDCPs 1 with DIAD (7).
Table 4. Optimization of the reaction conditions of VDCP 1a with N-
Boc aldimine 9.[a]
Entry
Catalyst
T [oC]
t [h]
Total yield[b] [%]
10a/11a
1
BF3·OEt2
BF3·OEt2
BF3·OEt2
60
60
80
80
80
80
80
80
80
80
5
5
5
10
10
5
5
5
5
10
47
47
54
33
46
60
70
67
63
9[d]
1.3:1.0
1.3:1.0
1.3:1.0
1.4:1.0
1.3:1.0
1.2:1.0
1.2:1.0
1.2:1.0
1.2:1.0
1.4:1.0
2[c]
3
4
5
6
7
8
9
10
Yb
Sc(OTf)3
Cu(OTf)2
A
ACHTUNGTRENNUNG
ACHTUNGTRENNUNG
TfOH
TsOH·H2O
Tf2NH
CF3CO2H
[a] All reactions were carried out with 1a (0.2 mmol), 9 (0.3 mmol), cata-
lyst (10 mol%), and DCE (2.0 mL). [b] Yield of isolated product. [c] The
ratio of 1a and 9 was 1:2. [d] 62% of 1a was recovered.
Figure 1. ORTEP drawing of compound 6k. Ellipsoids are shown at the
50% probability level.
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967

M. Shi et al.
Figure 2. ORTEP drawing of compound 10a. Ellipsoids are shown at the
50% probability level.
of TfOH, and the results of these experiments are outlined
in Table 5. As can be seen from Table 5, the corresponding
six-membered cycloaddition products 10 and 11 were ob-
tained in moderate yields in all cases. In the case of VDCPs
1d and 1e, substituted with electron-poor aromatic groups,
the ratios of 10 to 11 were higher than that for a VDCP sub-
stituted with electron-rich aromatic groups (Table 5, en-
tries 2 and 3 versus entry 1). A plausible mechanism for the
formation of products 10 and 11 is outlined in Scheme 9. Ini-
tially, N-Boc aldimine 9 is activated by Brønsted acid TfOH
to afford intermediate J, which subsequently adds to the C1’
carbon atom of VDCP 1 to give the corresponding inter-
mediates K-1 and K-2. Ring closure of intermediates K-1
and K-2 affords intermediates L-1 and L-2, respectively. Hy-
drolysis of L-1 and L-2 produces 10 and 11, respectively
(Scheme 9). Intermediate K-2 is more stable when both R1
and R2 are electron-rich groups than if it contained elec-
tron-poor groups; therefore, this intermediate subsequently
affords product 11 in higher yield and the ratio of 10 to 11 is
lower (Table 5, entries 2 and 3). It was believed that cycliza-
Scheme 9. Plausible mechanism for the TfOH-catalyzed reactions of
VDCPs 1 with N-Boc aldimine 9.
tion of intermediates K-1 and K-2 is faster than the cyclo-
propane ring-opening reaction in this particular case, so the
six-membered products 10 and 11 were formed instead of
the [3+2] cycloaddition products.
AHCTUNTGREN(GNUN CuOTf)2·C6H6-catalyzed reactions of VDCPs 1 with N-Ts-
iminophenyliodinane (12): Copper(I)-catalyzed aziridination
of olefin by using N-Ts-iminophenyliodinane, an iodine–ni-
trogen double-bond-containing compound, as the nitrene
source has attracted much attention and many catalytic sys-
tems have been explored.[12] In the course of an examination
of CuI-catalyzed aziridination of VDCPs 1, we found that,
when the (CuOTf)2·C6H6-catalyzed reactions of VDCPs 1
with N-Ts-iminophenyliodinane (12) were carried out in di-
chloromethane at room temperature, none of the aziridina-
tion products were obtained but, interestingly, indene deriv-
atives 13 were formed in 20–36% yields, along with some of
the starting materials being recovered (Table 6). The prod-
uct structure of 13a was further confirmed by X-ray diffrac-
tion and the ORTEP drawing is depicted in Figure 3.[13] To
Table 5. TfOH-catalyzed reactions of VDCPs 1 with N-Boc aldimine 9.[a]
Entry 1 (R1/R2)
Products Total yield[b] [%] 10/11
improve the yield of 13, other catalysts such as Cu
Sc(OTf)3, [Fe(TCPP)Cl] (TCPP: tetra(4-carboxyphenyl)por-
phyrin), [Cu(salen)] complex (salen: N,N’-bis(salicylidene)-
ACHTUNGTRENNUNG(OTf)2,
1
2
3
1b (p-MeC6H4/p-MeC6H4) 10b+11b 78
1d (p-ClC6H4/p-ClC6H4)
1e (p-FC6H4/p-FC6H4)
1.0:1.0
3.0:1.0
2.8:1.0
A
ACHTUNGTRENNUNG
10c+11c 52[c]
10d+11d 74
AHCTUNGTRENNUNG
ethylenediamine), and [Cu(2,2’-bipyridine)2]ClO4 complex
were also examined, and the reaction outcomes were not as
good as those of (CuOTf)2·C6H6-catalyzed reactions. A plau-
[a] All reactions were carried out with 1 (0.2 mmol), 9 (0.3 mmol), TfOH
(10 mol%), and DCE (2.0 mL) at 808C. [b] Yield of isolated product.
[c] 29% of 1 was recovered.
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Chem. Eur. J. 2009, 15, 963 – 971

Reactions of Vinylidene Cyclopropanes
FULL PAPER
Table 6.
ACHTUNGTRENNUNG(CuOTf)2·C6H6-catalyzed reactions of VDCPs 1 with N-Ts-imi-
nophenyliodinane (12).[a]
Entry 1 (R1/R2/R3/R4)
t [h] Product Yield[b]
[%]
1
2
3
4
1j (C6H5/C6H5/C6H5/C6H5)
8
4
10
10
13a
13b
13c
13d
33
20
36
30
1k (p-MeC6H4/p-MeC6H4/C6H5/C6H5)
1l (p-FC6H4/p-FC6H4/C6H5/C6H5)
1m (C6H5/C6H5/p-FC6H4/p-FC6H4)
[a] All reactions were carried out with 1 (0.2 mmol), 12 (0.4 mmol),
(CuOTf)2·C6H6 (10 mol%), and CH2Cl2 (4.0 mL) at room temperature.
[b] Yield of isolated product.
Scheme 10. Plausible mechanism for the CuI-catalyzed reactions of
VDCPs 1 with PhI=NTs (12).
Conclusion
We have developed several interesting Lewis acid or Brønst-
ed acid catalyzed reactions of VDCPs 1 with activated
carbon–nitrogen, nitrogen–nitrogen, and iodine–nitrogen
double-bond-containing compounds to furnish a variety of
nitrogen-containing cyclic products in moderate to good
yields depending on the electronic nature and steric effects
of the employed substrates. These transformations provide a
new synthetic protocol for the preparation of heterocyclic
frameworks from easily available starting materials under
mild conditions. Plausible mechanisms for all of these trans-
formations have been discussed, based on the results ob-
tained. Efforts are in progress to elucidate further the mech-
anistic details and to understand the scope and limitations
of these reactions.
Figure 3. ORTEP drawing of compound 13a. Ellipsoids are shown at the
50% probability level.
sible mechanism for the formation of 13 is outlined in
Scheme 10. Initially, intermediate N is formed by the reac-
tion of CuI with PhI=NTs according to the general mecha-
nism in the CuI-catalyzed aziridination of olefin.[12a] Then,
the reaction of intermediate N with VDCP 1 gives the ring-
opened zwitterionic intermediate O presumably through nu-
cleophilic attack of the cyclopropane ring on the nitrene
species. The allylic rearrangement of zwitterionic intermedi-
ate O produces the corresponding zwitterionic intermediate
P, which undergoes an intramolecular Friedel–Crafts reac-
tion with the R3/R4 aromatic group to generate intermediate
Experimental Section
1H and 13C NMR spectra were recorded on a Bruker AM-300 spectrome-
ter for solutions in CDCl3 with tetramethylsilane (TMS) as an internal
standard at 300 and 75 MHz, respectively. Mass and HRMS spectra were
recorded by EI and MALDI methods, and HRMS was measured on a
Finnigan MA+ mass spectrometer. CHN microanalyses were recorded
on a Carlo-Erba 1106 analyzer. Organic solvents were dried by standard
methods when necessary. Satisfactory elemental microanalyses were ob-
Q. Protonation of intermediate
Q gives product 13
(Scheme 10).
Chem. Eur. J. 2009, 15, 963 – 971
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969

M. Shi et al.
tained with an analyzer. Commercially obtained reagents were used with-
out further purification. All of the reactions were monitored by TLC
with silica-gel-coated plates. Flash column chromatography was carried
out by using silica gel and at increased pressure.
Compound 6a: White solid; m.p. 169–1708C; 1H NMR (CDCl3,
300 MHz, TMS): d=1.15 (s, 3H; CH3), 1.54 (s, 3H; CH3), 1.56 (s, 3H;
CH3), 1.65 (s, 3H; CH3), 2.34 (s, 3H; CH3), 5.51 (s, 1H), 6.97–7.00 (m,
4H; Ar), 7.09 (d, J=8.4 Hz, 2H; Ar), 7.18–7.33 (m, 9H; Ar), 7.43 (d, J=
8.4 Hz, 2H; Ar), 7.57 ppm (d, J=6.9 Hz, 2H; Ar); 13C NMR (CDCl3,
75 MHz, TMS): d=20.6, 21.4, 25.1, 25.5, 30.2, 66.3, 66.9, 126.5, 126.8,
127.3, 127.8, 127.9, 128.1, 128.16, 128.22, 129.0, 129.1, 129.6, 129.7, 135.5,
137.7, 139.0, 141.4, 142.1, 142.6, 142.8 ppm; IR (CH2Cl2): n˜ =3059, 3027,
2991, 2926, 1599, 1493, 1443, 1336, 1156, 1092, 1031, 699 cmÀ1; MS (EI):
m/z (%): 533 [M]+ (6), 91 (100), 167 (43), 275 (20), 518 (19), 229 (16),
105 (15), 165 (11); elemental analysis calcd (%) for C35H35NO2S: C 78.76,
H 6.61, N 2.62; found: C 78.69, H 6.47, N 2.47.
General procedure for BF3·OEt2-catalyzed reactions of VDCPs 1 with
ethyl (arylimino)acetates 2: Under an argon atmosphere, VDCPs
1
(0.2 mmol), ethyl (arylimino)acetates 2 (0.3 mmol), and DCE (2.0 mL)
were added into a Schlenk tube. The reaction mixture was stirred at
608C, then BF3·OEt2 (10 mol%) was added. The reaction mixture was
stirred at 608C for 1 h, then the solvent was removed under reduced
pressure and the residue was purified by flash column chromatography.
General procedure for BF3·OEt2-catalyzed reactions of VDCPs 1 with N-
Ts imines 5: Under an argon atmosphere, VDCPs 1 (0.2 mmol), N-Ts
imines 5 (0.3 mmol), and DCE (2.0 mL) were added into a Schlenk tube.
The reaction mixture was stirred at 608C, then BF3·OEt2 (10 mol%) was
added. The reaction mixture was stirred at 608C for 1 h, then the solvent
was removed under reduced pressure and the residue was purified by
flash column chromatography.
Compound 8a: Pale-yellow oil; 1H NMR (CDCl3, 300 MHz, TMS): d=
0.98 (d, J=6.3 Hz, 3H; CH3), 1.10 (d, J=5.7 Hz, 3H; CH3), 1.11 (s, 3H;
CH3), 1.21 (d, J=5.7 Hz, 3H; CH3), 1.24 (d, J=6.3 Hz, 3H; CH3), 1.66
(s, 3H; CH3), 1.69 (s, 3H; CH3), 1.91 (s, 3H; CH3), 4.75–4.90 (m, 1H),
4.90–5.00 (m, 1H), 7.19–7.28 (m, 8H; Ar), 7.37–7.41 ppm (m, 2H; Ar);
13C NMR (CDCl3, 75 MHz, TMS): d=20.1, 21.6, 21.8, 24.8, 24.9, 25.4,
65.5, 67.9, 70.3, 126.8, 127.0, 127.1, 128.2, 128.7, 129.2, 129.3, 134.1, 134.7,
136.7, 140.4, 140.6, 152.4, 158.6 ppm; IR (CH2Cl2): n˜ =2980, 2935, 1744,
General procedure for Sc
ACHTUNGTRENNUNG
1725, 1701, 1467, 1444, 1404, 1385, 1286, 1180, 1111, 1078, 751, 700 cmÀ1
;
DIAD (7): Under an argon atmosphere, VDCPs 1 (0.2 mmol), ScAHCTUNGTRENNUNG
MS (ESI): m/z: 477 [M+1]+; HRMS (MALDI): calcd for C29H36N2O4Na:
(10 mol%), and DCE (2.0 mL) were added into a Schlenk tube. DIAD
(7; 0.3 mmol) was then added. The reaction mixture was stirred at room
temperature for the time specified in Table 3, then the solvent was re-
moved under reduced pressure and the residue was purified by flash
column chromatography.
499.2567; found: 499.2570.
Compounds 10a and 11a: White solid; m.p. 234–2388C; 1H NMR
(CDCl3, 300 MHz, TMS) for 10a: d=0.12 (s, 3H; CH3), 1.03 (s, 3H;
CH3), 1.21 (s, 3H; CH3), 1.31 (s, 3H; CH3), 5.09 (s, 1H), 5.32 (s, 1H),
6.05 (d, J=8.1 Hz, 1H; Ar), 6.57 (d, J=8.1 Hz, 1H; Ar), 6.66 (t, J=
8.1 Hz, 1H; Ar), 6.90–7.47 (m, 11H; Ar), 7.90 ppm (d, J=7.5 Hz, 1H;
Ar); 13C NMR (CDCl3, 75 MHz, TMS) for 10a: d=16.1, 16.2, 18.6, 19.6,
27.1, 27.9, 62.5, 70.7, 126.4, 127.1, 127.65, 127.7, 128.1, 128.2, 128.9, 130.5,
130.6, 140.1, 142.10, 142.7, 146.8, 158.5 ppm; 1H NMR (CDCl3, 300 MHz,
TMS) for 11a: d=À0.24 (s, 3H; CH3), À0.14 (s, 3H; CH3), 0.92 (s, 3H;
CH3), 0.95 (s, 3H; CH3), 5.26 (d, J=3.9 Hz, 1H), 6.10 (d, J=3.9 Hz, 1H),
6.90–7.47 (m, 14H; Ar), 7.73 ppm (d, J=7.5 Hz, 1H; Ar); 13C NMR
(CDCl3, 75 MHz, TMS) for 11a: d=15.7, 16.4, 18.5, 19.1, 24.6, 25.5, 58.2,
68.4, 126.7, 127.2, 127.5, 127.8, 128.0, 128.4, 129.7, 130.0, 131.0, 141.4,
142.05, 143.2, 148.5, 155.9 ppm; IR (CH2Cl2): n˜ =3391, 3246, 3058, 3002,
2924, 1717, 1492, 1454, 1444, 1374, 1062, 762, 736, 699 cmÀ1; MS (ESI):
m/z: 446 [M++Na]; HRMS (ESI): calcd for C29H30NO2: 424.2271; found:
424.2287.
Compound 13a: Orange solid; m.p. 166–1688C; 1H NMR (CDCl3,
300 MHz, TMS): d=2.35 (s, 3H; CH3), 3.65 (d, J=6.6 Hz, 2H), 3.89 (t,
J=6.6 Hz, 1H; NH), 6.40 (d, J=7.8 Hz, 1H; Ar), 6.81–6.87 (m, 1H; Ar),
7.05–7.12 (m, 4H; Ar), 7.24–7.45 ppm (m, 17H; Ar); 13C NMR (CDCl3,
75 MHz, TMS): d=21.4, 40.1, 120.2, 123.5, 125.7, 126.9, 127.0, 128.1,
128.5, 128.59, 128.61, 128.9, 129.1, 129.17, 129.20, 130.5, 130.8, 131.3,
133.9, 136.5, 137.3, 137.7, 142.05, 142.09, 142.5, 142.7, 146.9, 147.6 ppm;
IR (CH2Cl2): n˜ =3282, 3058, 2923, 1596, 1487, 1442, 1407, 1328, 1160,
1093, 1029, 760, 700 cmÀ1; MS (MALDI): m/z: 562 [M+Na]+; HRMS
(MALDI): calcd for C36H29NO2SNa: 562.1811; found: 562.1827.
General procedure for TfOH-catalyzed reactions of VDCPs 1 with N-
Boc aldimine 9: Under an argon atmosphere, VDCPs 1 (0.2 mmol), N-
Boc aldimine
9 (0.3 mmol), and DCE (2.0 mL) were added into a
Schlenk tube. The reaction mixture was stirred at 808C, then TfOH
(10 mol%) was added. The reaction mixture was stirred at 808C for 5 h,
then the solvent was removed under reduced pressure and the residue
was purified by flash column chromatography.
General procedure for (CuOTf)2·C6H6-catalyzed reactions of VDCPs 1
with N-Ts-iminophenyliodinane (12): Under an argon atmosphere,
VDCPs
1
(0.2 mmol), N-Ts-iminophenyliodinane (12; 0.4 mmol),
(CuOTf)2·C6H6 (10 mol%), and CH2Cl2 (4.0 mL) were added into a
Schlenk tube. The reaction mixture was stirred at room temperature for
the time specified in Table 6, then the solvent was removed under re-
duced pressure and the residue was purified by flash column chromatog-
raphy.
Compound 3a: Yellow solid; m.p. 83–848C; 1H NMR (CDCl3, 300 MHz,
TMS): d=1.08 (s, 3H; CH3), 1.23 (t, J=6.9 Hz, 3H; CH3), 1.69 (s, 3H;
CH3), 1.86 (s, 3H; CH3), 1.92 (s, 3H; CH3), 2.30 (s, 3H; CH3), 2.37 (s,
3H; CH3), 4.08–4.25 (m, 2H; CH2), 4.45 (s, 1H), 6.60 (d, J=9.6 Hz, 2H;
Ar), 7.00–7.13 (m, 8H; Ar), 7.18–7.24 ppm (m, 2H; Ar); 13C NMR
(CDCl3, 75 MHz, TMS): d=14.1, 21.2, 21.3, 24.0, 25.0, 27.6, 60.7, 64.2,
65.6, 108.1, 115.7, 127.5, 128.4, 128.8, 129.4, 130.2, 131.4, 131.7, 136.3,
137.4, 139.4, 139.6, 140.3, 140.8, 142.8, 172.6 ppm; IR (CH2Cl2): n˜ =3022,
2982, 2924, 2869, 1739, 1588, 1496, 1445, 1387, 1365, 1345, 1316, 1263,
1235, 1174, 1156, 1111, 1083, 1025, 910, 810, 738, 707 cmÀ1; MS (EI): m/z
(%): 557 [M]+, 484 (100), 486 (95), 195 (51), 485 (31), 487 (22), 180 (7),
165 (4.2), 105 (3.5); HRMS (EI): calcd for C33H36NO2Br: 557.1929;
found: 557.1927.
Acknowledgements
Compound 4a: Pale-yellow solid; m.p. 211–2128C; 1H NMR (CDCl3,
300 MHz, TMS): d=0.55 (s, 3H; CH3), 0.65 (s, 3H; CH3), 1.01 (t, J=
7.2 Hz, 3H; CH3), 1.12 (s, 3H; CH3), 1.21 (s, 3H; CH3), 2.28 (s, 3H;
CH3), 2.31 (s, 3H; CH3), 3.34 (dq, J=18.0, 7.2 Hz, 1H), 3.70 (dq, J=18.0,
7.2 Hz, 1H), 4.57 (s, 1H), 6.55 (d, J=8.4 Hz, 1H; Ar), 6.66 (d, J=1.8 Hz,
1H; Ar), 6.90–7.06 (m, 7H; Ar), 7.12 (dd, J=1.8, 8.4 Hz, 1H; Ar),
7.23 ppm (d, J=8.4 Hz, 1H; Ar); 13C NMR (CDCl3, 75 MHz, TMS): d=
13.7, 20.0, 20.2, 20.5, 20.7, 20.8, 20.9, 24.3, 57.1, 59.8, 60.8, 110.1, 117.2,
126.6, 127.9, 128.2, 129.9, 130.3, 130.7, 131.9, 134.4, 135.4, 135.8, 140.7,
142.7, 143.4, 145.3, 172.7 ppm; IR (CH2Cl2): n˜ =3371, 3020, 2989, 2917,
2864, 1727, 1595, 1508, 1488, 1447, 1371, 1266, 1207, 1127, 1111, 1024,
967, 810, 738, 701 cmÀ1; MS (EI): m/z (%): 557 [M]+ (3), 484 (100), 486
(90), 336 (31), 338 (28), 485 (26), 487 (22), 350 (20), 468 (19); HRMS
(EI): calcd for C33H36NO2Br: 557.1929; found: 557.1918.
We thank the Shanghai Municipal Committee of Science and Technology
(grant nos.: 06XD14005 and 08dj1400100-2), the National Basic Research
Program of China (grant no.: ACTHUNRTGNEUNG(973)-2009CB825300), and the National
Natural Science Foundation of China (20872162, 20672127, and
20732008) for financial support.
[1] For the synthesis of VDCPs, see: a) K. Isagawa, K. Mizuno, H.
Sugita, Y. Otsuji, J. Chem. Soc. Perkin Trans. 1 1991, 2283–2285,
and references therein; b) T. Sasaki, S. Eguchi, M. Ohno, F. Nakata,
J. Org. Chem. 1976, 41, 2408–2411; c) T. Sasaki, S. Eguchi, T.
Ogawa, J. Org. Chem. 1974, 39, 1927–1930; d) T. Sasaki, S. Eguchi,
T. Ogawa, Heterocycles 1975, 3, 193–196; e) S. Eguchi, M. Arasaki,
970
www.chemeurj.org
ꢀ 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2009, 15, 963 – 971

Reactions of Vinylidene Cyclopropanes
FULL PAPER
J. Chem. Soc. Perkin Trans. 1 1988, 1047–1050; f) H. Sugita, K.
Mizuno, T. Mori, K. Isagawa, Y. Otsuji, Angew. Chem. 1991, 103,
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Patrick, Tetrahedron Lett. 1974, 15, 1407–1408; h) J. R. Al Dulayy-
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i) T. B. Patrick, J. Org. Chem. 1977, 42, 3354–3356; j) H. D. Hartzler,
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c) B. M. Nugent, R. A. Yoder, J. N. Johnston, J. Am. Chem. Soc.
2004, 126, 3418–3419.
[11] Crystal data for 10a: empirical formula: C29H29NO2; formula mass:
423.53; colorless, prismatic crystals; crystal size: 0.415ꢁ0.203ꢁ
0.176 mm3; orthorhombic; primitive lattice; space group
P2(1)2(1)2(1); a=9.3034(10), b=12.9069(14), c=20.000(2) ꢂ; a=
[2] a) K. Mizuno, H. Sugita, T. Hirai, H. Maeda, Y. Otsuji, M. Yasuda,
M. Hashiguchi, K. Shima, Tetrahedron Lett. 2001, 42, 3363–3366;
b) K. Mizuno, K. Nire, H. Sugita, Y. Otsuji, Tetrahedron Lett. 1993,
34, 6563–6566; c) T. Sasaki, S. Eguchi, T. Ogawa, J. Am. Chem. Soc.
1975, 97, 4413–4414.
90, b=90, g=908; V=2401.6(4) ꢂ3; Z=4; 1calcd =1.171 gcmÀ3
;
F
000 =904; R=0.0452, Rw=0.0846. Data measured on a Rigaku
AFC7R diffractometer. CCDC 669282 contains the supplementary
crystallographic data for this paper. These data can be obtained free
of charge from The Cambridge Crystallographic Data Centre via
www.ccdc.cam.ac.uk/data_request/cif.
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E. N. Jacobsen, J. Am. Chem. Soc. 1995, 117, 5889–5890; c) P.
Brandt, M. J. Sodergren, P. G. Andersson, P.-O. Norrby, J. Am.
Chem. Soc. 2000, 122, 8013–8020; d) D. A. Evans, M. M. Faul, M. T.
Bilodeau, J. Org. Chem. 1991, 56, 6744–6746; e) D. A. Evans, M. M.
Faul, M. T. Bilodeau, B. A. Anderson, D. M. Barnes, J. Am. Chem.
Soc. 1993, 115, 5328–5329; f) D. Tanner, P. G. Andersson, A.
Harden, P. Somfai, Tetrahedron Lett. 1994, 35, 4631–4634.
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127, 14552–14553; c) Y.-P. Zhang, J.-M. Lu, G.-C. Xu, M. Shi, J.
Org. Chem. 2007, 72, 509–516; d) J.-M. Lu, M. Shi, Tetrahedron
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[8] Crystal data for 6k: empirical formula: (C37H37NO2S)2·Et2O; formu-
[13] Crystal data for 13a: empirical formula: C36H29NO2S; formula mass:
539.66; colorless, prismatic crystals; 0.515ꢁ0.383ꢁ0.297 mm3; triclin-
la mass: 596.80; colorless, prismatic crystals; crystal size 0.397ꢁ
¯
0.335ꢁ0.274 mm; triclinic; primitive lattice; space group P1; a=
¯
ic; primitive lattice; space group: P1; a=9.7260(8), b=11.7625(9),
10.0732(11), b=12.0779(13), c=15.2057(17) ꢂ; a=89.065(2), b=
c=13.0513(10) ꢂ; a=84.8050(10), b=75.386(2), g=75.5150(10)8;
V=1398.27(19) ꢂ3; Z=2; 1calcd =1.282 gcmÀ3; F000 =568; R=0.0494,
Rw=0.1268. Data measured on a Rigaku AFC7R diffractometer.
CCDC 630759 contains the supplementary crystallographic data for
this paper. These data can be obtained free of charge from The
Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/
data_request/cif.
76.764(2),
g=82.639(2)8;
V=1785.8(3) ꢂ3;
Z=2;
1calcd =
1.110 gcmÀ3; F000 =638; R=0.0678; Rw=0.1805. Data measured on
a Rigaku AFC7R diffractometer. CCDC 619569 contains the supple-
mentary crystallographic data for this paper. These data can be ob-
tained free of charge from The Cambridge Crystallographic Data
Centre via www.ccdc.cam.ac.uk/data_request/cif.
[9] a) A. de Meijere, I. Erden, W. Weber, D. Kaufmann, J. Org. Chem.
1988, 53, 152–161; b) L.-X. Shao, M. Shi, Eur. J. Org. Chem. 2004,
426–430.
Received: August 30, 2008
Revised: October 11, 2008
Published online: December 12, 2008
Chem. Eur. J. 2009, 15, 963 – 971
ꢀ 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
971