Catalytic [3 + 2] Cycloaddition through Ring Cleavage of Simple Cyclopropanes with Isocyanates

Article abstract of DOI:10.1021/acs.orglett.5b01905

The catalytic synthesis of γ-butyrolactams was established via [3 + 2]-cycloaddition of cyclopropanes with isocyanates. An organotin iodide ate complex, MgBr⁺[Bu₂SnBrI₂]^-, was employed as an effective catalyst. Simple cyclopropanes that lack aryl or vinyl substituents were useful precursors. Even acyl cyclopropanes were applicable. The hybrid characteristics of a tin complex, acidic MgBr⁺ with nucleophilic tin iodide, was responsible for the catalytic reaction.

Full text of DOI:10.1021/acs.orglett.5b01905

Letter
pubs.acs.org/OrgLett
Catalytic [3 + 2] Cycloaddition through Ring Cleavage of Simple
Cyclopropanes with Isocyanates
Shinji Tsunoi, Yoshiaki Maruoka, Itaru Suzuki, and Ikuya Shibata*
Research Center for Environmental Preservation, Osaka University, 2-4 Yamadaoka, Suita, Osaka 565-0871, Japan
S
* Supporting Information
ABSTRACT: The catalytic synthesis of γ-butyrolactams was estab-
lished via [3 + 2]-cycloaddition of cyclopropanes with isocyanates. An
organotin iodide ate complex, MgBr+[Bu2SnBrI2]−, was employed as
an effective catalyst. Simple cyclopropanes that lack aryl or vinyl
substituents were useful precursors. Even acyl cyclopropanes were applicable. The hybrid characteristics of a tin complex, acidic
MgBr+ with nucleophilic tin iodide, was responsible for the catalytic reaction.
[3 + 2]-Cycloadditions of cyclopropanes have proven to be a
powerful strategy for the direct synthesis of five-membered
carbo- and heterocycles, and such methodologies have been
applied to natural product syntheses.1 Cycloadditions are
typically carried out using catalysts that include a Lewis acid or
a transition metal.2−9 Donor−acceptor (D−A) cyclopropanes
with aryl or vinyl substituents have been used as the active
precursors in most cases. We established a [3 + 2]
cycloaddition using either epoxides or 2-methyleneaziridines
with isocyanates and tin iodide catalysts.10,11 In the case of 2-
methyleneaziridines,10c the combination of Bu2SnI2 with LiI
showed high catalytic activity in which an ate type of tin
complex such as Li+[SnBu2I3]− worked as an active catalytic
species. Simple cyclopropanes seem to lack utility, but in the
present study we developed a tin-catalyzed cycloaddition with
isocyanates to form γ-butyrolactams (Scheme 1).12 γ-
Table 1. Cycloaddition of Cyclopropane 1a with TsNC
a
O
entry
catalyst
none
solvent
yield of 2a/%
1
2
3
4
5
6
7
dichloroethane
dichloroethane
dichloroethane
dichloroethane
dichloroethane
CH2Cl2
0
Bu2SnI2
0
MgBr2
64
60
>99
>99
60
MgI2
Bu2SnI2-MgBr2
Bu2SnI2-MgBr2
Bu2SnI2-MgBr2
THF
a
1a, 1 mmol; TsNCO, 1 mmol; Bu2SnI2, 0.1 mmol; MgBr2, 0.1
mmol; solvent, 1 mL.
Scheme 1. Cycloadditions of Simple Cyclopropanes with
Isocyanates
obtained in a quantitative yield (entry 5). Dichloromethane and
dichloroethane were superior to THF as solvents (entries 5−7).
To date, transition metal or Lewis acid catalyzed cyclo-
addition with heterocumulenes has been applied only to
donor−acceptor (D−A) cyclopropanes.12 In a reaction with
isocyanates, Tsuji et al. reported a cycloaddition of vinyl
cyclopropane that was catalyzed via a Pd complex.12a In that
Pd-catalyzed reaction, the formation of π-allyl palladium species
was a key step. Stoltz et al. have reported a Lewis acid catalyzed
cycloaddition,12c where the reaction passed a 1,3-dipole, which
included a stable allylic or benzylic cation. In these methods,
using donor−acceptor cyclopropanes was essential for an
effective ring cleavage. Among our results, it was noteworthy
that cyclopropane 1a bears only acceptor substituents. Thus,
simple cyclopropanes that lack aryl or vinyl substituents proved
to be useful precursors.
Butyrolactams could serve as useful building blocks toward
natural products and pharmaceutically relevant heterocycles.13
Hence, the catalytic preparation of γ-butyrolactams from simple
cyclopropanes is a desirable result, particularly when using
transition-metal-free catalysts.
Initially, we performed the cycloaddition of cyclopropane
1,1-carboxylate ester 1a with tosyl isocyanate (Table 1).
Without a catalyst, no reaction proceeded at 25 °C for 1 h
(entry 1). Using 0.1 equiv of Bu2SnI2 as a catalyst afforded no
reaction (entry 2). Catalytic system Bu2SnI2−LiI was effective
for the reaction of 2-methyleneaziridines,10c but it was not
active in cases where starting cyclopropane 1a and tosyl
isocyanate were recovered quantitatively. However, using
MgBr2 and MgI2 as a catalyst gave γ-butyrolactam 2a in 64%
and 60% yield, respectively (entries 3 and 4). Furthermore, in a
system that combined Bu2SnI2 with MgBr2, product 2a was
With respect to our catalytic system, Bu2SnI2−MgBr2,14 we
have already achieved the formation of an ate complex,
MgBr+[Bu2SnBrI2]−, which works as an active catalyst in the
Received: July 3, 2015
© XXXX American Chemical Society
A
DOI: 10.1021/acs.orglett.5b01905
Org. Lett. XXXX, XXX, XXX−XXX

Organic Letters
Letter
reactions (Scheme 2). When
a
tin complex,
A plausible catalytic cycle is shown in Scheme 3. Initially, the
tin catalyst attacked 1a at the C-2 carbon to give a metal ketene
MgBr+[Bu2SnBrI2]−, was reacted with an equimolar amount
Scheme 2. Ate Tin Iodide Complex
Scheme 3. A Plausible Catalytic Cycle
of 1a at rt for 24 h, a ring-opened adduct, iodoethyl malonate,
was formed in a 45% yield, whereas, using only Bu2SnI2 or
MgBr2 afforded lower yields (<10%) for the ring-opened
adduct under the same conditions. The characteristic feature of
the tin ate complex is its hybrid makeup, in which both an
acidic magnesium cation and a nucleophilic Sn−I bond are
included in the same molecule.14a Thus, MgBr+ acted as a Lewis
acid to activate the dicarboxylate moiety and accelerate the ring
opening. Simultaneously, a prolonged Sn−I bond that occupied
the axial position in the TBP tin structure15 attacked the
cyclopropane ring in an effective manner. Although a similar
catalytic principle of MgI2 has been reported,2g,7b−d,8a the
hybrid characteristic of the tin catalyst is one of the reasons for
the higher activity than MgI2 and the accessibility of simple
cyclopropanes that lack aryl or vinyl substituents.
acetal A. The hybrid characteristics of the tin catalyst worked
well in the ring opening of cyclopropane. The preference for
dichloroethane over THF as a solvent can be explained by the
difference in their coordinating ability. A coordinating solvent
such as THF would prevent the MgBr+ activation toward 1a.
Dichloroethane did not affect the MgBr+ moiety; hence, the
effective activation of the 1,1-carboxylate esters of 1a is
possible. In a subsequent step, metal ketene acetal A was added
to an isocyanate, giving a tin amide B. To make this step
effective, the use of highly electrophilic isocyanates was
necessary. In the last stage, the intramolecular alkylation of
metal amide B afforded γ-butyrolactam 2, regenerating the tin
catalyst.
Table 2 shows the results of the reaction of cyclopropane 1a
with various isocyanates catalyzed by Bu2SnI2−MgBr2 under
Table 2. Cycloaddition of Cyclopropane 1a with ArNC
a
O
Conventionally useful donor−acceptor cyclopropanes were
also applicable in our catalytic system (Scheme 4). In the case
of vinylcyclopropane 1b, the corresponding γ-butyrolactam 3
was obtained when tosyl isocyanate was reacted (eq 1).
However, in the reaction with other aromatic isocyanates, no
entry
Ar
C6H5
time/h
product
yield of 2/%
b
1
2
3
4
5
6
7
8
24
24
48
48
48
72
48
24
2b
2c
2d
2e
2f
35
p-MeOC6H4
p-BrC6H4
trace
53
p-ClC6H4
78
p-FC6H4
52
Scheme 4. Cycloaddition of Active Cyclopropanes with
RNCO
p-CF3C6H4
p-NCC6H4
p-NO2C6H4
2g
2h
2i
66
76
82
a
1a, 1 mmol; ArNCO, 1 mmol; Bu2SnI2, 0.1 mmol; MgBr2, 0.1
b
mmol; dichloroethane, 1 mL; 40 °C. 60 °C.
the optimized conditions. The reactivity was dependent upon
the substituents of isocyanates. The reaction with PhNCO
proceeded at 60 °C for 24 h to give product 2b in a 35% yield
(entry 1). When p-methoxyphenyl isocyanate (PMPNC
O) was reacted, the desired product 2c could not be obtained,
and both substrates were recovered quantitatively (entry 2).
Other alkyl-substituted isocyanates were unreactive. However,
isocyanates with electron-withdrawing substituents were
reactive. p-Bromophenyl, p-chlorophenyl, and p-fluorophenyl
isocyanates gave the corresponding γ-butyrolactams 2d−2f
(entries 3−5). Besides halogen substituents on the aromatic
rings, CF3−, CN groups were also allowed and gave 2g and 2h
(entries 6 and 7). In particular, the reaction with p-nitrophenyl
isocyanate gave the desired product 2i in an 82% yield (entry
8).
B
DOI: 10.1021/acs.orglett.5b01905
Org. Lett. XXXX, XXX, XXX−XXX

Organic Letters
Letter
desired products could be isolated. Under the same conditions,
without isocyanates, cyclopentene derivative 4 was obtained as
a rearrangement product from 1b through an intramolecular
reaction of stannyl ketene acetal C to allylic iodide (eq 2).16
Thus, stannyl ketene acetal C reacted with only highly
electrophilic tosyl isocyanate prior to the intramolecular
reaction. As another activated cyclopropane, methylenecyclo-
propane 1c also reacted well to give 4-methylene-γ-
butyrolactam 5a (eq 3). Besides tosyl isocyanate, p-nitrophenyl
isocyanate was reactive to give 5b. The ring opening of
methylenecyclopropane 1c afforded tin dienolate D. Thus, it is
clear that the products, 5a and 5b, were derived from the α-
addition of the tin dienolate D.
One of the advantages of the presented tin-catalyzed reaction
is that simple cyclopropanes that lack an aryl or vinyl
substituent could be applicable as useful precursors. Hence,
we next tried to use other simple cyclopropanes besides 1a.
Fortunately, we found that benzoyl cyclopropane 1d was useful
for the cycloaddition (Table 3). The desired product 6a was
Scheme 5. Cycloaddition of Cyclopropane 1a with
Isothiocyanate
Product 7 was derived from the addition of isothiocyanates
across the CS bond.17
In conclusion, we demonstrated the catalytic synthesis of γ-
butyrolactams via a [3 + 2]-cycloaddition with isocyanates. The
organotin iodide complex MgBr+[Bu2SnBrI2]− was generated
from Bu2SnI2 and MgBr2 and was employed as an effective
catalyst. The hybrid character of a tin ate complex, acidic
MgBr+ and nucleophilic tin iodide, was responsible for the
catalytic reaction. Simple cyclopropanes that lack aryl or vinyl
substituents were useful precursors. Even acyl cyclopropanes
were useful. We are now planning tin-catalyzed cycloadditions
with other electrophiles.
Table 3. Cycloaddition of Cyclopropanes 1d−g with TsN
a
CO
ASSOCIATED CONTENT
* Supporting Information
■
S
The Supporting Information is available free of charge on the
ACS Publications website at DOI: 10.1021/acs.or-
glett.5b01905.
entry
R
conditions
product
yield of 6/%
b
1
2
3
4
5
6
C6H5 (1d)
1d
40 °C, 24 h
40 °C, 24 h
80 °C, 24 h
80 °C, 24 h
80 °C, 24 h
60 °C, 48 h
6a
6a
6a
6b
6c
6d
25
c
77 (15 )
Experimental procedures and spectral data (PDF)
1d
86
69
64
70
p-MeOC6H4 (1e)
p-ClC6H4 (1f)
Me (1g)
AUTHOR INFORMATION
Corresponding Author
■
a
1a, 1 mmol; TsNCO, 2 mmol; Bu2SnI2, 0.1 mmol; MgBr2, 0.1
*shibata@epc.osaka-u.ac.jp
Notes
b
c
mmol; dichloroethane, 1 mL. TsNCO, 1 equiv. Only MgBr2
cat.
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
obtained in a 25% yield at 40 °C after 24 h (entry 1). Catalytic
cycloaddition using simple acyl cyclopropanes is rare. Reactions
with enones3e or alkynes4c have been reported using a Ni
catalyst system. The cycloaddition with imines was reported via
stoichiometric MgI2.7d Hence, the presented tin-catalyzed
reaction with isocyanates is noteworthy in terms of application
to simple acyl cyclopropanes. To increase the yield of desired
product 6a, we found that using 2 equiv of isocyanate gave a
77% yield (entry 2). Furthermore, the reaction at 80 °C
attained an 86% yield (entry 3). The reaction with PhNC
O resulted in a lower yield (20%) because of low electro-
philicity of PhNCO. Besides benzoyl cyclopropane, p-
methoxyphenylcarbonyl- and p-chlorophenylcarbonyl cyclo-
propanes 1e and 1f were reactive to give the corresponding
α-acyl-γ-butyrolactams 6b and 6c in 69% and 64% yields,
respectively (entries 4 and 5). A similar product, 6d, was
obtained using acetyl cyclopropane 1g (entry 6). Products 6a,
6c, and 6d were isolated as enol compounds, and 6b was a
This research was supported by a Grant-in-Aid for Scientific
Research from the Ministry of Education, Science, Sports, and
Culture and the Naito Foundation.
REFERENCES
■
(1) For reviews of activated cyclopropanes, see: (a) Reissig, H.-U.;
Zimmer, R. Chem. Rev. 2003, 103, 1151−1196. (b) Rubin, M.; Rubina,
M.; Gevorgyan, V. Chem. Rev. 2007, 107, 3117−3179. (c) De Simone,
F.; Waser, J. Synthesis 2009, 2009, 3353−3374. (d) Campbell, M. J.;
Johnson, J. S.; Parsons, A. T.; Pohlhaus, P. D.; Sanders, S. D. J. Org.
Chem. 2010, 75, 6317−6325. (e) Shi, M.; Lu, J.-M.; Wei, Y.; Shao, L.-
X. Acc. Chem. Res. 2012, 45, 641−652. (f) Tang, P.; Qin, Y. Synthesis
2012, 44, 2969−2984. (g) Wang, Z. Synlett 2012, 23, 2311−2327.
(h) Cavitt, M. A.; Phun, L. H.; France, S. Chem. Soc. Rev. 2014, 43,
804−818. (i) De Nanteuil, F.; De Simone, F.; Frei, R.; Benfatti, F.;
Serrano, E.; Waser, J. Chem. Commun. 2014, 50, 10912−10928.
(j) Schneider, T. F.; Kaschel, J.; Werz, D. B. Angew. Chem., Int. Ed.
2014, 53, 5504−5523. (k) Grover, H. K.; Emmett, M. R.; Kerr, M. A.
Org. Biomol. Chem. 2015, 13, 655−671.
(2) Cycloaddition of D−A cyclopropane with aldehyde: For recent
example, see: BF3 cat.: (a) Christie, S. D. R.; Davoile, R. J.; Elsegood,
M. R. J.; Fryatt, R.; Jones, R. C. F.; Pritchard, G. J. Chem. Commun.
2004, 2474−2475. (b) Miyake, Y.; Endo, S.; Moriyama, T.; Sakata, K.;
Nishibayashi, Y. Angew. Chem., Int. Ed. 2013, 52, 1758−1762. AlCl3
cat.: (c) Sanders, S. D.; Ruiz-Olalla, A.; Johnson, J. S. Chem. Commun.
1
keto-type compound, all of which were detected by H NMR.
In addition to isocyanates, we next tried to use an
isothiocyanate (Scheme 5). In the reaction of 1a with PhN
CS, although the yield of the desired 1:1 adduct was
unsatisfactory, using more electrophilic p-nitrophenyl isothio-
cyanate afforded a moderate yield of the desired adduct 7.
C
DOI: 10.1021/acs.orglett.5b01905
Org. Lett. XXXX, XXX, XXX−XXX

Organic Letters
Letter
2009, 5135−5137. (d) Sathishkannan, G.; Srinivasan, K. Chem.
Commun. 2014, 50, 4062−4064. SnCl4 cat.: (e) Benfatti, F.; de
Nanteuil, F.; Waser, J. Chem. - Eur. J. 2012, 18, 4844−4849.
(f) Karadeolian, A.; Kerr, M. A. J. Org. Chem. 2010, 75, 6830−6841.
MgI2 cat.: (g) Parsons, A. T.; Johnson, J. S. J. Am. Chem. Soc. 2009,
131, 3122−3123. Sn(OTf)2 cat.: (h) Pohlhaus, P. D.; Sanders, S. D.;
Parsons, A. T.; Li, W.; Johnson, J. S. J. Am. Chem. Soc. 2008, 130,
8642−8650. R3SiOTf cat.: (i) Xing, S.; Li, Y.; Li, Z.; Liu, C.; Ren, J.;
Wang, Z. Angew. Chem., Int. Ed. 2011, 50, 12605−12609. Sc(OTf)3
cat.: (j) Xing, S.; Pan, W.; Liu, C.; Ren, J.; Wang, Z. Angew. Chem., Int.
Ed. 2010, 49, 3215−3218. (k) Smith, A. G.; Slade, M. C.; Johnson, J. S.
Org. Lett. 2011, 13, 1996−1999. Yb(OTf)3 cat.: (l) Fujino, D.;
Yorimitsu, H.; Oshima, K. J. Am. Chem. Soc. 2011, 133, 9682−9685.
Sun; Li, Y.-X.; Wang, L.-J.; Tang, Y. Angew. Chem., Int. Ed. 2013, 52,
1452−1456. Ni cat.: (h) Tombe, R.; Kurahashi, T.; Matsubara, S.
Org. Lett. 2013, 15, 1791−1793. Fe cat.: (i) Pursley, D.; Plietker, B.
Synlett 2014, 25, 2316−2318.
(8) Cycloaddition of D−A cyclopropane with nitrone: MgI2 cat.:
(a) Ganton, M. D.; Kerr, M. A. J. Org. Chem. 2004, 69, 8554−8557.
Sc(OTf)3 cat.: (b) Zhang, Y.; Liu, F.; Zhang, J. Chem. - Eur. J. 2010,
16, 6146−6150. Yb(OTf)3 cat.: (c) Humenny, W. J.; Kyriacou, P.;
Sapeta, K.; Karadeolian, A.; Kerr, M. A. Angew. Chem., Int. Ed. 2012,
51, 11088−1109. (d) Cardona, F.; Goti, A. Angew. Chem., Int. Ed.
2005, 44, 7832−7835. (e) Gorbacheva, E. O.; Tabolin, A. A.; Novikov,
R. A.; Khomutova, Y. A.; Nelyubina, Y. V.; Tomilov, Y. V.; Ioffe, S. L.
Org. Lett. 2013, 15, 350−353. (f) Ding, Q.; Wang, Z.; Wu, J.
Tetrahedron Lett. 2009, 50, 198−200. (g) Mikhaylov, A. A.; Novikov,
R. A.; Khomutova, Y. A.; Arkhipov, D. E.; Korlyukov, A. A.; Tabolin,
A. A.; Tomilov, Y. V.; Ioffe, S. L. Synlett 2014, 25, 2275−2280.
Yb(NTf2)3 cat.: (h) Yang, H.-B.; Shi, M. Org. Biomol. Chem. 2012, 10,
8236−8243. Ni(ClO4)2 cat.: (i) Kang, Y.-B.; Sun, X.-L.; Tang, Y.
Angew. Chem., Int. Ed. 2007, 46, 3918−3921. (j) Sibi, M. P.; Ma, Z.;
Jasperse, C. P. J. Am. Chem. Soc. 2005, 127, 5764−5765.
Ca(NTf ) cat.: (m) Haubenreisser, S.; Hensenne, P.; Schroder, S.;
̈
2
2
Niggemann, M. Org. Lett. 2013, 15, 2262−2265.
FeCl3 cat.
(n) Benfatti, F.; de Nanteuil, F.; Waser, J. Org. Lett. 2012, 14, 386−
389. Pd cat.: (o) Parsons, A. T.; Campbell, M. J.; Johnson, J. S. Org.
Lett. 2008, 10, 2541−2544. (p) Mei, L-y.; Wei, Y.; Xu, Q.; Shi, M.
Organometallics 2013, 32, 3544−3556. (q) Shiba, T.; Kuroda, D.;
Kurahashi, T.; Matsubara, S. Synlett 2014, 25, 2005−2008.
(9) Cycloaddition of D−A cyclopropane with nitrile: TfOH cat.:
(a) Cui, B.; Ren, J.; Wang, Z. J. Org. Chem. 2014, 79, 790−796.
(b) Huang, J. W.; Shi, M. Synlett 2004, 2343−2346. SnCl4 cat.:
(c) Chagarovskiy, A. O.; Ivanov, K. L.; Budynina, E. M.; Ivanova, O.
A.; Trushkov, I. V. Chem. Heterocycl. Compd. 2012, 48, 825−827.
TMSOTf cat.: (d) Yu, M.; Pagenkopf, B. L. J. Am. Chem. Soc. 2003,
125, 8122−8123.
(10) Epoxides: (a) Shibata, I.; Baba, A.; Iwasaki, H.; Matsuda, H. J.
Org. Chem. 1986, 51, 2177−2184. (b) Shibata, I.; Yoshimura, N.; Baba,
A.; Matsuda, H. Tetrahedron Lett. 1992, 33, 7149−7152. 2-
Methyleneaziridine: (c) Takahashi, H.; Yasui, S.; Tsunoi, S.; Shibata,
I. Eur. J. Org. Chem. 2013, 2013, 40−43.
(11) Synthetic uses of organotin compounds; for example, see:
(a) Baba, A.; Shibata, I.; Yasuda, M. In Comprehensive Organometallic
Chemistry III; Knochel, P., Ed.; Elsevier: Oxford, 2007; Vol. 9, Chapter
8, pp 341−380. (b) Pereyre, M.; Quintard, P. J.; Rahm, A. Tin in
Organic Synthesis; Butterworth: London, 1987; pp 261−285.
(c) Davies, A. G. Organotin Chemistry; VCH: Weinhelm, 1997; pp
166−193.
(12) Cycloaddition with RNC = X: Pd cat.: (a) Yamamoto, K.;
Ishida, T.; Tsuji, J. Chem. Lett. 1987, 1157−1158. AlCl3 cat.: (b) Sun,
Y.; Yang, G.; Chai, Z.; Mu, X.; Chai, J. Org. Biomol. Chem. 2013, 11,
7859−7868. Sn(OTf)2 cat.: (c) Goldberg, A. F. G.; O’Connor, N. R.;
Craig, R. A., II; Stoltz, B. M. Org. Lett. 2012, 14, 5314−5317.
(13) Ye, L.-W.; Shu, C.; Gagosz, F. Org. Biomol. Chem. 2014, 12,
1833−1845.
(14) (a) Shibata, I.; Suwa, T.; Sakakibara, H.; Baba, A. Org. Lett.
2002, 4, 301−303. (b) Shibata, I.; Suwa, T.; Ryu, K.; Baba, A. J. Org.
Chem. 2001, 66, 8690−8692. (c) Shibata, I.; Suwa, T.; Ryu, K.; Baba,
A. J. Am. Chem. Soc. 2001, 123, 4101−4102.
(15) Five-coordinate tin: (a) Davis, A. G. Organotin Chemistry; VCH:
New York, 1997; pp 18−24. (b) Harrison, P. G. Chemistry of Tin;
Blackie: London, 1989; pp 71−89. (c) Holecek, J.; Nadvornik, M.;
Handlir, K.; Lycka, A. J. Organomet. Chem. 1983, 241, 177−184.
(d) Nadvornik, M.; Holecek, J.; Handlir, K.; Lycka, A. J. Organomet.
Chem. 1984, 275, 43−51.
(16) Related ring-opening cyclization. (a) Han, Z.; Uehira, S.;
Tsuritani, T.; Shinokubo, H.; Oshima, K. Tetrahedron 2001, 57, 987−
995. (b) Coscia, R. W.; Lambert, T. H. J. Am. Chem. Soc. 2009, 131,
2496−2498.
(17) It is known that the Sn−N and Sn−S bonds add to an
isothiocyanate across the CS bond to give an adduct having a Sn−S
bond like C. (a) Itoh, K.; Lee, I. K.; Matsuda, I.; Sakai, S.; Ishii, Y.
Tetrahedron Lett. 1967, 8, 2667−2670. (b) Itoh, K.; Fukumoto, Y.;
Ishii, Y. Tetrahedron Lett. 1968, 9, 3199−3202. (c) Sakai, S.; Niimi, H.;
Kobayashi, Y.; Ishii, Y. Bull. Chem. Soc. Jpn. 1977, 50, 3271−3275.
(d) Bloodworth, A. J.; Davies, A. G.; Vasishtha, S. C. J. Chem. Soc. C
1967, 1309−1313. (e) Baba, A.; Shibata, I.; Kashiwagi, H.; Matsuda,
H. Bull. Chem. Soc. Jpn. 1986, 59, 341−343.
(3) Cycloaddition of D−A cyclopropane with Michael acceptor:
GaCl3 cat.: (a) Novikov, R. A.; Tarasova, A. V.; Korolev, V. A.;
Timofeev, V. P.; Tomilov, Y. V. Angew. Chem., Int. Ed. 2014, 53,
3187−3191. Pd cat.: (b) Trost, B. M.; Morris, P. J.; Sprague, S. J. J.
Am. Chem. Soc. 2012, 134, 17823−17831. (c) Goldberg, A. F. G.;
Stoltz, B. M. Org. Lett. 2011, 13, 4474−4476. Ni cat.: (d) Lloyd-
Jones, G. C. Angew. Chem., Int. Ed. 2006, 45, 6788−6790. (e) Liu, L.;
Montgomery, J. J. Am. Chem. Soc. 2006, 128, 5348−5349. Fe cat.:
(f) Dieskau, A. P.; Holzwarth, M. S.; Plietker, B. J. Am. Chem. Soc.
2012, 134, 5048−5051.
(4) Cycloaddition of D−A cyclopropane with alkene: Sc(OTf)3 cat.:
(a) Zhu, W.; Fang, J.; Liu, Y.; Ren, J.; Wang, Z. Angew. Chem., Int. Ed.
2013, 52, 2032−2037. Zn(OTf)2 cat. (b) Yu, Q.; Ma, S. Chem.
Commun. 2012, 48, 11784−11786. Alkyne: Ni cat.: (c) Tamaki, T.;
Ohashi, M.; Ogoshi, S. Angew. Chem., Int. Ed. 2011, 50, 12067−12070.
(d) Binger, P.; Lu, Q.-H.; Wedemann, P. Angew. Chem., Int. Ed. Engl.
1985, 24, 316−317. (e) Saito, S.; Komagawa, S.; Azumaya, I.; Masuda,
M. J. Org. Chem. 2007, 72, 9114−9120. Rh cat.: (f) Wender, P. A.;
Pedersen, T. M.; Scanio, M. J. C. J. Am. Chem. Soc. 2002, 124, 15154−
15155. Ru cat.: (g) Trost, B. M.; Toste, F. D.; Shen, H. J. Am. Chem.
Soc. 2000, 122, 2379−2380.
(5) Cycloaddition of D−A cyclopropane with Si enolate: Me3AlCl
cat.: (a) Horiguchi, Y.; Suehiro, I.; Sasaki, A.; Kuwajima, I. Tetrahedron
Lett. 1993, 34, 6077−6080. SnCl4 cat.: (b) de Nanteuil, F.; Waser, J.
Angew. Chem., Int. Ed. 2011, 50, 12075−12079. (c) Serrano, E.; de
Nanteuil, F.; Waser, J. Synlett 2014, 25, 2285−2288. (d) Komatsu, M.;
Suehiro, I.; Horiguchi, Y.; Kuwajima, I. Synlett 1991, 1991, 771−773.
Sc(OTf)3 cat.: (e) Fang, J.; Ren, J.; Wang, Z. Tetrahedron Lett. 2008,
49, 6659−6662. Cu(ClO4)2cat.: (f) Xu, H.; Qu, J.-P.; Liao, S.; Xiong,
H.; Tang, Y. Angew. Chem., Int. Ed. 2013, 52, 4004−4007.
(6) Cycloaddition of D−A cyclopropane with enamine: BF3 cat.:
(a) Venkatesh, C.; Singh, P. P.; Ila, H.; Junjappa, H. Eur. J. Org. Chem.
2006, 2006, 5378−5386. TMSOTf cat.: (b) Bajtos, B.; Yu, M.; Zhao,
H.; Pagenkopf, B. L. J. Am. Chem. Soc. 2007, 129, 9631−9634.
Yb(OTf)3 cat.: (c) England, D. B.; Kuss, T. D. O.; Keddy, R. G.; Kerr,
M. A. J. Org. Chem. 2001, 66, 4704−4709. Cu(OTf)2 cat.: (d) Xiong,
H.; Xu, H.; Liao, S.; Xie, Z.; Tang, Y. J. Am. Chem. Soc. 2013, 135,
7851−7854. Ynamide: Sc(OTf)3 cat.: (e) Mackay, W. D.; Fistikci, M.;
Carris, R. M.; Johnson, J. S. Org. Lett. 2014, 16, 1626−1629.
(7) Cycloaddition of D−A cyclopropane with imine: BF3 cat.:
(a) Christie, S. D. R.; Davoile, R. J.; Jones, R. C. F. Org. Biomol. Chem.
2006, 4, 2683−2684. MgI2 cat.: (b) Parsons, A. T.; Smith, A. G.;
Neel, A. J.; Johnson, J. S. J. Am. Chem. Soc. 2010, 132, 9688−9692.
(c) Carson, C. A.; Kerr, M. A. J. Org. Chem. 2005, 70, 8242−8244.
(d) Bertozzi, F.; Gustafsson, M.; Olsson, R. Org. Lett. 2002, 4, 3147−
3150. Yb(OTf)3 cat.: (e) Jackson, S. K.; Karadeolian, A.; Driega, A.
B.; Kerr, M. A. J. Am. Chem. Soc. 2008, 130, 4196−4201. Sc(OTf)3
cat.: (f) Kang, Y.-B.; Tang, Y.; Sun, X.-L. Org. Biomol. Chem. 2006, 4,
299−301. Ni(ClO4)2 cat.: (g) Zhou, Y.-Y.; Li, J.; Ling, L.; Liao, S.-H.;
D
DOI: 10.1021/acs.orglett.5b01905
Org. Lett. XXXX, XXX, XXX−XXX