Lewis Acid Catalyzed Formal [3+2] Cycloaddition of Donor-Acceptor Cyclopropanes and 1-Azadienes: Synthesis of Imine Functionalized Cyclopentanes and Pyrrolidine Derivatives

Article abstract of DOI:10.1002/adsc.201700744

Lewis acid catalyzed formal [3+2] cycloadditions of 1-azadienes with donor acceptor cyclopropanes to synthesize varieties of imine functionalized cyclopentanes and pyrrolidine derivatives in moderate to high yield have been developed. Moreover, pharmaceut

Full text of DOI:10.1002/adsc.201700744

Title: Lewis Acid Catalyzed [3+2] Cycloaddition of Donor- Acceptor
Cyclopropanes and 1-Azadienes: Synthesis of Imine
Functionalized Cyclopentanes and Pyrrolidine Derivatives
Authors: Prabal Banerjee and Kamal Verma
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10.1002/adsc.201700744
Advanced Synthesis & Catalysis
UPDATE
DOI: 10.1002/adsc.201((will be filled in by the editorial staff))
Lewis Acid Catalyzed Formal [3+2] Cycloaddition of Donor-
Acceptor Cyclopropanes and 1-Azadienes: Synthesis of Imine
Functionalized Cyclopentanes and Pyrrolidine Derivatives
Kamal Verma and Prabal Banerjee*
Department of Chemistry, Indian Institute of Technology Ropar, Nangal Road, Ropar, Punjab, India, Pin 140001, Fax:
(+91)-1881-223395, e-mail: prabal@iitrpr.ac.in
Received:((will be filled in by the editorial staff))
Supporting information for this article is available on the WWW under http://dx.doi.org/10.1002/adsc.201######.((Please
delete if not appropriate))
Abstract: Lewis acid catalyzed formal [3+2]
cycloadditions of 1-azadienes with donor acceptor
cyclopropanes to synthesize varieties of imine
functionalized cyclopentanes and pyrrolidine derivatives
in moderate to high yield have been developed. Moreover,
pharmaceutically
relevant
azabicyclo[3.2.1]octane,
bearing two all-carbon quaternary stereogenic centers at
the bridgehead positions, has been synthesized by nosyl
group deprotection and intramolecular amidation of imine
functionalized cyclopentane derivative.
Keywords: Donor-Acceptor Cyclopropane; 1-Azadienes;
Imine Functionalized Cyclopentanes; Pyrrolidine;
azabicyclo[3.2.1]octane
Nitrogen-containing carbocycles and heterocycles are
ubiquitous in many biologically active natural
products and pharmaceutically relevant molecules.[1]
In this regard, imine functionalized cyclopentanes
and pyrrolidine derivatives are of particular interest.
Gababutin
analogues,
constituting
amine
Scheme 1. Cycloaddition reactions.
functionalized cyclopentanes, are having anti-
inflammatory activity.[2] In addition, 1-sulfonyl
pyrrolidine derivatives play a potential role for the
treatment of neurological disorder.[3] Azabicyclic
amino acid shows inhibitory activity against tumor
cell[4] (Figure 1). Owing to the tremendous
pharmaceutical applications, developments of
efficient and credible methodologies for the synthesis
of these structural motifs are of greater interest.
In general, donor-acceptor cyclopropanes (DACs)
consisting a versatile three-carbon synthon, offer
synthetic flexibility and atom economy in organic
synthesis.[5] In the last few decades, it is being used as
1,3-dipoles, which undergoes formal [3+n] annulation
reactions with numerous reactive partners to form
carbo- and heterocycles.[5,6] In a series of reports, the
competition between [3+2] and [4+3] annulations of
cyclopropanes and 1,3-conjugated dienes, was
recently explored by Budynina group. In addition,
they discussed Lewis acid-catalyzed formal [3+2]
cycloadditions of DACs with acyclic and cyclic
butadienes.[7] To the best of our knowledge, [4+3]
cycloaddition of DACs[8] and 1-azadienes are not
reported yet, even though Diels-Alder reactions of 1-
azadienes through [4+2] are common in literature. In
this regards, Ma et al. described a versatile path to 2-
amino-1,4-dihydropyridines through an inverse
Figure 1. Example of drugs and amino acid.
1
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10.1002/adsc.201700744
Advanced Synthesis & Catalysis
electron-demand Diels-Alder reaction of electron-
deficient azadienes[9] and ynamides.[10] Mead et al.
reported [4+2] cycloadditions between conjugated
aldimine and benzyne at elevated temperature
(Scheme 1).[11] Encouraged by these results, we
subjected the cycloaddition reaction between DACs
and 1-azadiene, divergent products were obtained,
depending upon substituent present in 1-azadiene, C-
attack of DACs to 1-azadienes furnished imine
functionalized cyclopentane derivatives, whereas N-
attack of 1-azadienes to DACs furnished pyrrolidine
derivatives through [3+2] annulations. Herein, we
wish to report an efficient method for the synthesis of
N-tosyl or nosyl imine functionalized cyclopentanes
and pyrrolidine derivatives via formal [3+2]-
cycloaddition of DACs and 1-azadiene. Further
utilization of imine functionalized cyclopentane
towards the synthesis of valuable pharmaceutical
important analog of azabicyclo[3.2.1]octane with the
generation of two quaternary carbon stereogenic
centers at the bridgehead positions also being
presented in this article.
was used as catalyst for this transformation and 45%
of 4fa was obtained (Table 1, entry 2). This
motivated us to increase the loading of MgI2 upto 20
mol%, which provided us the best yield (Table 1,
entry 4). Further increment of MgI2, gradually
decreased the yield of the reaction (Table 1, entry 5,
6). MgBr2 acted as a best catalyst on heating (Table 1,
entry 9), while others, like MgCl2 and Mg(OTf)2
produced inferior results (see supporting information
(SI)). Lewis acids, eg. Cu(OTf)2, Sc(OTf)3,
Ni(ClO4)2.6H2O, InCl3, Zn(OTf)2, FeCl2 failed to
produce the desired product (see SI). Solvents were
also screened to check feasibility of the reaction,
chlorinated solvent such as chloroform gave almost
similar efficiency like dichloromethane (Table 1,
entry 10). Coordinating solvent, like tetrahydrofuran
produced 75% of 4fa (Table1, entry 12) while in
acetonitrile, poor yield was noticed (Table 1, entry
11).
Table 2. Scope of cycloadditions between 1 and 2.[a]
Table 1. Optimization of reaction condition.[a]
En LA
try
LA
(mol
%)
Solvent Temp Tim Yield
(oC)
e (h) (%)[b]
1
2
3
4
5
6
7
8
9
None
0
5
10
20
50
100
CH2Cl2
CH2Cl2
CH2Cl2
25
25
25
24
8
8
5
4
n.r[c]
45
61
80
77
60
5
81
75
77
69
75
MgI2
MgI2
MgI2
MgI2
MgI2
MgBr2 20
MgBr2 20
MgBr2 20
CH2Cl2 25
CH2Cl2
CH2Cl2
CH2Cl2
DCE[d]
Toluene 110
CHCl3 25
CH3CN 25
THF[e]
25
25
25
25
80
2
12
10
12
5
9
4
10 MgI2
11 MgI2
12 MgI2
20
20
20
[a] All reactions were carried out under inert atmosphere: 1f
(0.10 mmol, 1 equiv.), 2a (0.10 mmol, 1 equiv.), Lewis
acid, solvent (1 mL).
[b]
Isolated yield after flash column chromatography. No
minor isomer could be isolated or detected.
[c] n.r = no reaction.
[d] DCE = 1,2-dichloroethane.
[e] THF = Tetrahydrofuran.
[a] All reactions were carried out under inert atmosphere: 1
(0.10 mmol, 1 equiv.), 2 (0.10 mmol, 1 equiv.), MgI2 (0.02
mmol, 0.2 equiv.), solvent (1 mL).
The present studies began with the optimization of
the reaction conditions for the formal [3+2]
cycloaddition reaction of DAC 1f and 1-azadiene 2a
(Table 1). Our group previously displayed the utility
of MgI2 as an effective catalyst for the ring opening
of strained rings such as epoxides, aziridines and
cyclopropanes.[12] In the beginning, 5 mol% of MgI2
[b] Isolated yield after flash column chromatography.
With the optimized reaction conditions in hand, we
focused our attention to evaluate the scope of [3+2]
2
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10.1002/adsc.201700744
Advanced Synthesis & Catalysis
cycloaddition reaction between 1 and 2 to produce
cyclopentane derivatives 4 (Table 2). A series of
DACs bearing electron-donating or electron
withdrawing groups present in variable position of
phenyl ring were examined. DACs 1e, 1f, 1g, 1h
containing electron donating methoxy substituent in
para and meta position afforded 4eb, 4fa, 4ga, 4ha,
respectively with greater yield. 2-Furan substituted
DAC 1j provided 4ja with 75% yield in 7h. Nitrogen
functionalized DAC 1i furnished the desired
cycloadduct 4ib in 3h with 77% yield. DACs
containing less electronically enriched alkyl group,
methyl 1b and isopropyl group 1c substituted at para
position in the vicinal phenyl ring gave 72% and 71%
yield of the product, respectively. 2-Styryl DAC 1d
gave good yield of 4db in 6h. Phenyl substituted
DAC gave 70% yield of 4ab at room temperature.
2,4,6-Trimethyl substituted DAC 1k was able to
produce the desired product 4kb with 69% yield.
Methyl incorporation at para position in phenyl ring
of 1-azadiene 2b, gave 4fc in good yield. As nosyl
group can be removed easily under mild condition,
we conducted the cycloaddition reactions of N-nosyl
azadienes 2d and 2e with DACs, which gave 4ad and
4be, respectively. The stereochemistry of 4eb was
determined by single crystal X-ray analysis (Table
2).[13]
the diastereomeric ratios (dr) gradually gets
converted from cis-7fb to trans-6fb isomer (Table 3,
entry 1, 2, 3, 4). While, 10 or 20 mol% loading of
Cu(OTf)2 gave good yield of cis-7fb as a major
isomer at room temperature (Table 3, entry 6, 7).
However, lower (5 mol%) and higher (50 mol%)
loading delivered inferior results (Table 3, entry 5, 8).
Table 4. Scope of cycloadditions between 1 and 3.[a]
Table 3. Optimization of reaction condition.[a]
[a] All reactions were carried out under inert atmosphere: 1
(0.15 mmol, 1 equiv.), 3 (0.15 mmol, 1 equiv.), Lewis
Acid, solvent (1 mL).
En
try
LA
LA
(mol
%)
Temp Tim
Dr[c]
Yield
(%)[b]
(oC)
e (h)
[b] Isolated yield after flash column chromatography.
[c] Sc(OTf)3 (20 mol%).
[d] Cu(OTf)2 (10 mol%).
1
2
3
4
5
6
7
8
9
Sc(OTf)3
Sc(OTf)3
Sc(OTf)3
Sc(OTf)3
Cu(OTf)2
Cu(OTf)2
Cu(OTf)2
Cu(OTf)2
MgI2
5
25
25
25
25
25
25
25
25
25
5
3
2.5
2
14
12
12
8
15:85
50:50
64:36
98:2
1:99
19:81
20:80
23:77
-
75
80
79
75
10
75
72
50
-
[e] Determined by 1H NMR.
10
20
50
5
10
20
50
20
Scope of [3+2] cycloadditions between 1 and 3 is
presented in Table 4. The annulation of N-benzyl
aldimine with DACs to form five-membered N-
benzyl pyrrolidines derivatives has been previously
reported in the literature, [14] while, to the best of our
knowledge, no reports are available with N-tosyl
substituted aldimine. After standardizing the reaction
condition, we performed the cycloaddition of 1-
azadienes 3a with DAC 1f, which gave two isomers
of pyrrolidine derivatives 6fa and 7fa with combined
81% yield. Next, we examined this reaction with
methoxy substituted at para-position of the phenyl
ring of aldimine 3b with more activated DACs
containing an electron-donating group, such as
methoxy (1e and 1f) which yielded the products 6eb
& 7eb and 6fc & 7fc. Less electronically enriched, p-
tolyl-(1b) or 2-styryl-substituted 1d cyclopropanes
gave the diastereomeric mixtures of the
corresponding products with good yield. Phenyl-
6
[a] All reactions were carried out under inert atmosphere: 1
(0.10 mmol, 1 equiv.), 2 (0.10 mmol, 1 equiv.), Lewis acid,
solvent (1 mL).
[b] Isolated yield after flash column chromatography.
[c] Determined by 1H NMR.
Initially, we tried the cycloaddition of 1f and 3a in
the presence of MgI2 (Table 3, entry 9) , but only
dimerized product of cyclopropane was obtained,
whereas other Lewis acids like Cu(OTf)2 and
Sc(OTf)3 in dichloromethane furnished the desired
products 6fb and 7fb, respectively (Table 3). As the
loading of Sc(OTf)3 was increased from 5 to 50 mol%,
3
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10.1002/adsc.201700744
Advanced Synthesis & Catalysis
substituted DAC 1a was unable to provide desired
Based on the above experimental evidence and
literature reports, plausible mechanism for the formal
cycloaddition reactions between 1 and 2 or 3 is
illustrated in Scheme 4. 1-Azadienes 2 or 3 follow
two different pathways I and II, respectively. In the
pathway I, DAC 1 undergoes iodide promoted
nucleophilic ring opening to convert into the open-
chain intermediate A. The highly unstable
intermediate A attacks the 1-azadiene 2 and then gets
converted into key intermediate B, which can adopt
two possible conformations C and D. In this case,
conformer C produced more preferably due to less
steric hindrance of two bulky groups. Further cyclizes
via SN2 fashion to give cyclopentane 4 as a major
product. In the catalytic pathway II, Cu(OTf)2
generates zwitterionic intermediate E. Lone pair of
electrons on nitrogen of 1-azadienes 3 attacks the
cationic carbon of intermediate E via SN1 fashion and
generates intermediate F. This intermediate can adopt
two possible conformational structures G and H.
Conformer G is more relevant than H because of less
steric hindrance between tosyl and aryl group. This
products.
Scheme 2. ORTEP structures of 5ha, 6fa and 9.
may be the reason for the is-isomer 6 to be major
C
than the trans-7. Stereochemistry of 6fa was
confirmed by single crystal X-ray structure analysis
(scheme 2 and see SI).[13] Previous reports have
explained that phenyl-substituted N-sulfonyl imine
was inactive in a reaction due to steric crowding[14a],
[12e]
but 2-styryl-substituted N-sulfonyl imine could
Scheme 3. [3+2] Cycloaddition of enantioenrich DAC (s)-
1b and 1-azadienes (2a or 3b).
reduce the steric effect. For this reason, N-sulfonyl
imine of 1-azadienes 3 and activated alkene ester of
1-azadienes 2 participate individually in the formal
cycloaddition process.
To gain some mechanistic insights, experiments
were carried out and the results are shown in Scheme
3. The cycloaddition reaction of enantiopure DAC
(S)-1b and both azadienes (2a and 3b) were carried
out seperately, 2a leads to optically enriched
cycloadduct 4ba, whereas, 3b gave almost racemic
adduct 6bb. This observation concluded that in 1st
case the key substitution reaction (Scheme 4)
proceeds via almost SN2 fashion and for 2nd case it
follows almost SN1 way.
Stereochemical model of trans-favored isomers
has proposed in scheme 5. Higher loading of
Sc(OTf)3, increases the coordination with tosyl group,
which reflects in the ratios of the diastereomeric
mixture. In this case, Conformer I found to be less
favourable due to the repulsion between coordinated-
scandium triflate and aryl group. On the other hand,
the conformer J featuring less steric hindrance leads
to the trans-6 as a major product.
4
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10.1002/adsc.201700744
Advanced Synthesis & Catalysis
Scheme 4. Plausible Mechanism.
Furthermore, two-step synthesis of valuable
pharmaceutically relevant azabicyclo[3.2.1]octane,
including two quaternary carbon stereogeniccenters
has been achieved. In addition, we also report
regioselective iodination of arenes of imine
functionalized cyclopentane derivatives. Further
application of this protocol towards natural product
synthesis
and
development
of
catalytic
enantioselective version of the present transformation
are in progress in our lab.
Scheme 5. Stereochemical model.
Utilizing the advantage of reactive nature of N-
nosyl amine and carbonyl ester at position 1 and 3 in
cyclopenatne 5ad, azabicyclo[3.2.1]octane 8 was
synthesized in good yield. In presence of 4-
methoxythiophenol and potassium carbonate, nosyl
deprotection followed by intermolecular amidation
took place to afford 8 with 70% yield (Scheme 6).[13]
Experimental Section
General procedure cycloadditions reaction between 1
and 2
A two-necked round bottom flask was charged with
Donor-Acceptor Cyclopropane 1 (1.0 equiv.), 1-Azadiene
2 (1.0 equiv.), MgI2 (0.2 equiv.) and DCM (1 mL) under
nitrogen atmosphere. The reaction mixture was stirred it at
room temperature until the consumption of cyclopropane
(as monitored by TLC). Solution of reaction was filtered
through thin pad of celite and solvent was concentrated in
rotary evaporator. The residue was purified by silica gel
flash column chromatography using diethyl ether/hexane
as eluent.
General procedure cycloadditions reaction between 1
and 3
Scheme 6. Imine reduction followed by nosyl deprotection
steps.
A two-necked round bottom flask was charged with
Donor-Acceptor Cyclopropane 1 (1.0 equiv.), N-tosyl
imine 3 (1.0 equiv.), 4 Å MS and Lewis acid (0.2 equiv.)
under nitrogen atmosphere. DCM was added to the
reaction mixture and solution was stirred it at room
temperature until the consumption of cyclopropane (as
monitored by TLC). Reaction mixture was filtered through
thin pad of celite and solvent was concentrated in rotary
evaporator. The residue was purified by flash column
chromatography on silica gel using ethyl acetate/hexane as
eluent.
Furthermore, to demonstrate the potential of the
developed methodology, selective reduction of imine
functionalized cycloadduct 4 was performed, using
NaBH4 to synthesize product 5 which is the structural
scaffold of gababutin (Scheme 7). Cycloadduct 5 was
subjected to a regioselective iodination of arenes[15] to
obtain iodinated product 9. ORTEP structure of 5ha
& 9 is presented in Scheme 2.[13]
Acknowledgements
KV thanks to the UGC, New Delhi, India for a senior research
fellowship. PB acknowledges the DST-India and CSIR-India for
financial support. Authors are also thankful to Dr. C. M.
Nagaraja, Department of Chemistry, IIT Ropar for solving the
single crystal X-ray structure presented in this paper.
References
Scheme 7. Imine reduction and Iodination of arenes.
[1] a) E. K. W. Tam, T. M. Nguyen, C. Z. H. Lim, P. L.
Lee, Z. Li, X. Jiang, S. Santhanakrishnan, T. W. Tan, Y.
L. Goh, S. Y. Wong, H. Yang, E. H. Q. Ong, J. Hill, Q.
Yu, C. L. L. Chai, ChemMedChem 2015, 10, 173-182;
b) D. O’Hagan, Nat. Prod. Rep. 2000, 17, 435-446.
Conclusion
In conclusion, we have demonstrated Lewis acid
catalyzed [3+2] cycloadditions reaction of DACs
with 1-azadienesto synthesize a variety of imine
[2] J. Bryans, L. Meltzer, PCT Int. Appl. WO
20030212133A1, 2003.
functionalized
cyclopentane
and
pyrrolidine
derivatives via SN2 and SN1 fashion, respectively.
5
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10.1002/adsc.201700744
Advanced Synthesis & Catalysis
[3] a) J. Zhou, Y.-Y. Yeung, Org. Biomol. Chem. 2014, 12,
7482-7485; b) V. Mutel, J. Wichmann, PCT Int. Appl,
WO 2002002554, 2002.
[9] a) J.-C. M. Monbaliu, K. G. R. Masschelein, C. V.
Stevens, Chem. Soc. Rev. 2011, 40, 4708-4739; b) R. A.
A. Foster, M. C. Willis, Chem. Soc. Rev. 2013, 42, 63-
76; c) A. -C. Knall, C. Slugovc, Chem. Soc. Rev. 2013,
42, 5131-5142.
[4] J. Qie, W. Zhou, X. Zhao, J. He, Y. Zhang, K. Liu, Int
J Pept Res Ther 2009, 15, 187-194.
[10] X. Yan, F. Ling, Y. Zhang, C. Ma, Org. Lett. 2015,
17, 3536-3539.
[5] Recent Reviews: a) A. K. Pandey, A. Ghosh, P.
Banerjee, Isr. J. Chem. 2016, 56, 512-521; b) M. A.
Kerr, Isr. J. Chem. 2016, 56, 476-487; c) S. Racine, J.
Vuilleumier, J. Waser, Isr. J. Chem. 2016, 56, 566-
577;d) L. Wang, Y. Tang, Isr. J. Chem. 2016, 56, 463-
475;e) H.-U. Reissig, R. Zimmer, Chem. Rev. 2003,
103, 1151-1196; f) C. A. Carson, M. A. Kerr, Chem.
Soc. Rev. 2009, 38, 3051-3060; g) M. A. Cavitt, L. H.
Phun, S. France, Chem. Soc. Rev. 2014, 43, 804-818; h)
T. F. Schneider, J. Kaschel, D. B.Werz, Angew. Chem.
2014, 126, 5608-5628; Angew. Chem., Int. Ed. 2014, 53,
5504-5523; i) H. K. Grover, M. R. Emmett, M. A. Kerr,
Org. Biomol. Chem. 2015, 13, 655-671 and references
cited there in.
[11] S. Stokes, M. Bekkam, M. Rupp, K. T. Mead, Synlett
2012, 23, 389-392.
[12] a) K. Verma, P. Banerjee, Adv. Synth. Catal. 2016,
358, 2053-2058; b) A. Ghosh, S. Mandal, P. K.
Chattaraj, P. Banerjee, Org. Lett. 2016, 18, 4940-4943;
c) A. K. Pandey, P. Banerjee, Asian J. Org. Chem.
2016, 5, 360-366; d) R. K. Varshnaya, P. Banerjee, Eur.
J. Org. Chem. 2016, 2016, 4059-4066; e) A. Ghosh, A.
K. Pandey, P. Banerjee, J. Org. Chem. 2015, 80, 7235-
7242; f) A. K. Pandey, A. Ghosh, P. Banerjee, Eur. J.
Org. Chem. 2015, 2015, 2517-2523; g) R. Dey, P.
Banerjee, Org. Lett. 2017, 19, 304-307; h) A. K.
Pandey, R. K. Varshnaya, P. Banerjee, Eur. J. Org.
Chem. 2017, 2017, 1647-1656; i) R. K. Varshnaya, P.
Banerjee, Org. Biomol. Chem. 2017, 15, 5182-5190.
[6] Other recent reports: a) T. Kaicharla, T. Roy, M.
Thangaraj, R. G. Gonnade, A. T. Biju, Angew. Chem.
2016, 128, 10215-10218; Angew. Chem., Int. Ed. 2016,
55, 10061-10064; b) J. Zhang, S. Xing, J. Ren, S. Jiang,
Z. Wang, Org. Lett. 2015, 17, 218-221; c) L. K. B.
Garve, M. Pawliczek, J. Wallbaum, P. G. Jones, D. B.
Werz, Chem. Eur. J. 2016, 22, 521-525; d) L. K. B.
Garve, M. Petzold, P. G. Jones, D. B. Werz, Org. Lett.
2016, 18, 564-567; e) J. R. Green, V. Snieckus, Synlett
2014, 25, 2258-2259.
[13] CCDC 1544399, CCDC 1544461, CCDC 1544463,
CCDC 1544393 and CCDC 1544391 contains the
supplementary crystallographic data of 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.
[14] a) Y.-B, Kang, Y. Tang, X.-L, Sun Org. Biomol.
Chem. 2006, 4, 299-301; b) A. T. Parsons, A. G. Smith,
A. J. Neel, J. S. Johnson, J. Am. Chem. Soc. 2010, 132,
9688-9692.
[7] E. M. Budynina, O. A. Ivanova, A. O.Chagarovskiy, Y.
K. Grishin, I. V. Trushkov, M. Y. Melnikov, J. Org.
Chem. 2015, 80, 12212-12223.
[8] a) H. Xu, J.-L. Hu, L. Wang, S. Liao, Y. Tang, J. Am.
Chem. Soc. 2015, 137, 8006-8009; b) O. A. Ivanova, E.
M. Budynina, Y. K. Grishin, I. V. Trushkov, P. V.
Verteletskii, Angew. Chem. 2008, 120, 1123-1126;
Angew. Chem., Int. Ed. 2008, 47, 1107-1110.
[15] D. T. Racys, C. E. Warrilow, S. L. Pimlott, A.
Sutherland, Org. Lett. 2015, 17, 4782-4785.
6
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10.1002/adsc.201700744
Advanced Synthesis & Catalysis
UPDATE
Lewis Acid Catalyzed Formal [3+2] Cycloaddition
of Donor- Acceptor Cyclopropanes and 1-
Azadienes: Synthesis of Imine Functionalized
Cyclopentanes and Pyrrolidine Derivatives
Adv. Synth. Catal. Year, Volume, Page – Page
Kamal Verma and Prabal Banerjee*
7
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