Enantioselective organocatalytic construction of hexahydropyrroloindole by means of α-alkylation of aldehydes leading to the total synthesis of (+)-gliocladin C

Article abstract of DOI:10.1002/chem.201204522

12-Step program: The combined use of cinchona alkaloid based amine and chiral phosphoric acid enabled the asymmetric alkylation reaction of 3-hydroxyoxindoles with aldehydes to give 3,3′-disubstituted oxindoles in excellent enantioselectivities, which all

Full text of DOI:10.1002/chem.201204522

COMMUNICATION
DOI: 10.1002/chem.201204522
Enantioselective Organocatalytic Construction of Hexahydropyrroloindole
by Means of a-Alkylation of Aldehydes Leading to the Total Synthesis of
(+)-Gliocladin C
Jin Song, Chang Guo, Arafate Adele, Hao Yin, and Liu-Zhu Gong*[a]
The hexahydropyrrolo
[2,3-b]indole skeleton, which con-
ganic chemists worldwide.[1e,f,4] Overman et al.[1f,5] and Mo-
vassaghi et al.[6] have developed elegant approaches to
access these alkaloids. The first total synthesis of gliocla-
din C was accomplished by Overman et al. on the basis of
the Mukaiyama aldol reaction of 2-siloxyindoles.[7] Very re-
cently, the same group illustrated an elegant strategy for the
construction of the C3 quaternary stereogenic center incor-
porated in (+)-gliocladin C by using an organocatalytic
enantioselective Steglich-type rearrangement of indolyl car-
bonate.[5e] Stephenson et al. also achieved this molecule by
an efficient radical coupling reaction through visible-light
photoredox catalysis.[8] Most recently, Movassaghi et al. re-
ported a Friedel–Crafts-type coupling strategy that led to
the concise total synthesis of (+)-gliocladin C.[9] Trost estab-
lished a convenient protocol to the pyrrolidinoinoline core
of the gliocladins by Pd-catalyzed allene hydrocarbonation
reaction.[10] Our laboratory reported a catalytic enantioselec-
tive total synthesis of (+)-folicanthine by means of phos-
phoric acid catalysis.[11] Herein, we will describe an amine-
catalyzed highly enantioselective alkylation reaction of 3-hy-
droxyoxindoles with enalizable aldehydes, which allows for
an asymmetric catalytic total synthesis of (+)-gliocladin C.
Our retrosynthetic analysis of (+)-gliocladin C is illustrat-
ed in Scheme 1. The tetracyclic core of (+)-gliocladin C
could be prepared from the intermediates 1 and 2 as demon-
strated by Overman et al.[5e] The indoline aldehyde 2 (Over-
man intermediate) could be easily synthesized from biindo-
tains a structurally rigid tricyclic subunit, in particular a qua-
ternary stereogenic center at their C3, is a signature struc-
tural element in a wide selection of alkaloids (Figure 1) that
Figure 1. Representative natural cyclotryptamine alkaloids.
have been isolated from a variety of natural resources.[1]
These alkaloids derived from the pyrrolidineACTHNUGRTENUNG[2,3-b]indolines
have been found to exhibit remarkable biological and phar-
macological activities. For example, gliocladin C exhibited
cytotoxic activity against murine P388 lymphocytic leukemia
cells,[2] whereas (+)-chaetocin has been reported to be a
potent inhibitor of lysine-specific histone methyltransfer-
ase.[3]
The significance of structures and biological properties of
these alkaloids has drawn considerable attention from or-
[a] J. Song, C. Guo, A. Adele, Dr. H. Yin, Prof. L.-Z. Gong
Hefei National Laboratory for Physical Sciences
Microscale Joint Laboratory of Green Synthetic Chemistry and
Department of Chemistry
University of Science and Technology of China
Hefei, 230026 (P.R. China)
Fax : (+86)551-3606266
E-mail: gonglz@ustc.edu.cn
Supporting information for this article is available on the WWW
under http://dx.doi.org/10.1002/chem.201204522.
Scheme 1. Retrosynthetic analysis of (+)-gliocladin C.
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3319

Table 1. Evaluation of catalysts and optimization of reaction conditions.[a]
lin-1,2-diol 3, which would be accessed by reduction of the
corresponding aldehyde 4. The key building block 4 could
be obtained directly from the enantioselective alkylation re-
action of 3-hydroxyoxindoles 5 with aldehydes 6 catalyzed
by a chiral amine. Thus, the asymmetric catalytic alkylation
reACHTUNGTRENNUNGaction of 2-alkyloxyacetaldehyde with 3-hydroxyoxindole
turned out to be a key step in the total synthesis of (+)-glio-
cladin C and was studied initially.
Organocatalytic asymmetric alkylation reactions have
been accomplished in high levels of stereoselectivity by
using chiral secondary amine catalysts.[12] However, the ex-
tension of these protocols to the reaction between 2-alkylox-
yacetaldehyde 6 and 3-hydroxyoxindole 5a failed to give
synthetically useful results (see the Supporting Information).
The cinchona-based primary amines have been proven to be
successful in the control of stereoselectivity in either en-
Entry
7
Acid
TFA
6
4
Yield [%][b]
d.r.[c]
ee [%][d]
ACHTUNGTRENNUNG HCATUNGTREN(NUGN 9-
amine or iminium catalysis.[13] In particular, 9-amino
1
2
3
4
5
6
7a
7b
7c
7d
7d
7d
7d
7d
7d
7d
7d
7d
7d
6a
6a
6a
6a
6b
6c
6c
6c
6c
6c
6c
6c
6c
4aa
4aa
4aa
4aa
4ba
4ca
4ca
4ca
4ca
4ca
4ca
4ca
4ca
31
30
37
48
36
43
47
35
–
32
42
62
80
1:1
1:1
2:1
2:1
2:1
2:1
4:1
6:1
–
3:1
6:1
7:1
8:1
À15
À23
68
73
58
75
77
63
–
65
87
90
94
TFA
TFA
TFA
TFA
TFA
TFA
8a
deoxy) epicinchona alkaloids, easily derived from natural re-
sources, have enabled the stereoselective functionalization
of a variety of sterically demanding carbonyl compounds.[14]
Inspired by these achievements, we envisaged that the cin-
chona alkaloid-based amines would be able to catalyze the
alkylation of 3-hydroxyoxindoles 5 with aldehydes 6 in a
stereoselective manner.
Thus, we first examined the a-alkylation reaction between
3-hydroxyoxindole 5a, which can be transformed into a vi-
nylogous iminACHTUNGTRENNUNGium intermediate under acidic condi-
7[e]
8[e]
9[e]
10[e]
11[e]
12[e]
13[f]
(R)-8a
8b
8c
8d
8d
tions,[11,12c,h,15] with 2-(benzyloxy)acetaldehyde 6a by using
cinchona alkaloid-based amines as chiral catalysts (Table 1).
However, the reaction gave the desired product in only
31% yield, together with poor diastereo- and enantioselec-
tivity in the presence of 10 mol% of the primary amine 7a
and 30 mol% of trifluoroacetic acid (TFA; Table 1, entry 1).
Neither the yield nor the enantioselectivity was significantly
improved when the bifunctional primary amine 7b was em-
ployed as catalyst (Table 1, entry 2). To our delight, the use
of amine 7c, which is derived from quinidine, was able to
dramatically enhance the enantioselectivity (68% ee;
Table 1, entry 3). The stereoselectivity was further improved
by using 7d as a chiral amine catalyst (Table 1, entry 4). The
OPMB-acetaldehyde 6c (PMB=para-methoxybenzyl) pro-
vided comparably higher enantioselectivity than its counter-
parts (Table 1, entries 4–6). Conducting the reaction at 158C
gave higher levels of diastereo- and stereoselectivities
(Table 1, entry 7). Xie et al.,[16] Melchiorre et al.,[14k,17] and
List et al.[18] found that the use of chiral phosphoric acid as a
cocatalyst dramatically enhances the stereochemical control
of primary amine catalysts of type 7. Therefore, a variety of
1,1’-bi-2,2’-naphthol (BINOL)-derived phosphoric acids[19]
were evaluated as the cocatalyst in this reaction (Table 1,
entries 8–12). Indeed, the addition of chiral phosphoric acid
has considerable influence on the stereoselectivity. The (S)-
phosphoric acid was proven to be a matched cocatalyst,
whereas the R enantiomer completely inhibited the catalytic
activity of amine (Table 1, entry 9). The matched/mismatch-
ed catalyst pair combinations (Table 1, entries 8 and 9)
strongly suggest the existence of cooperative dual activa-
[a] Reaction conditions: The reaction was conducted on a 0.1 mmol scale
with 6 (2 equiv) in commercial chloroform (undistilled CHCl3). Aldehyde
6 was added to a solution of 5a and the catalyst through a syringe pump
over a period of 10 h at 308C. [b] Yield of isolated products. [c] Diaster-
eomeric ratio (d.r.) determined by 1H NMR spectroscopy. [d] The ee
value was determined by HPLC analysis. [e] At 158C. [f] At 08C.
tion.[14k] Among the phosphoric acids screened, 8d turned
out to be the best cocatalyst to give 62% yield, 7:1 d.r., and
90% ee (Table 1, entry 12). The best results (80% yield,
8:1 d.r., and 94% ee) were achieved when the reaction was
carried out at 08C (Table 1, entry 13).
More interestingly, when the model reaction of 5a with
6c was conducted in distilled chloroform, both the yield and
enantioselectivity dramatically dropped (Table 2, entries 1
and 2). Considering that the commercial chloroform (undis-
tilled) contains a trace amount of ethanol (0.3–1%) as sta-
bilizer, we suspected that the alcohol might play a certain
role in the catalysis. Thus, different alcohols were examined
as additives of the distilled chloroform solvent for the re-
AHCTUNGTREGaNNUN ction. As anticipated, the addition of ethanol gave relative-
ly higher enatioselectivity, which matches the results ob-
tained from the reactions conducted in commercial chloro-
form (Table 2, entries 1, 3–5). These results demonstrated
that the alcohol indeed plays an important role in the for-
À
mation of a new C C bond and thereby influences the ster-
eoselectivity. To gain insight into the specific role of ethanol,
an alkylation reaction of 3-ethoxyoxindole 5a’, which was
derived from 3-hydroxyoxindole 5a and ethanol under
acidic conditions [Eq. (1)], with the aldehyde 6c was carried
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Construction of Hexahydropyrroloindole
COMMUNICATION
Table 2. The effect of alcohols in the alkylation reaction.[a]
Table 3. The scope of 3-hydroxyoxindoles.[a]
Entry
5 (R, R’)
4
Yield [%][b]
d.r.[c]
ee [%][d]
Entry
5
Additive Solvent
Yield [%][b] d.r.[c] ee [%][d]
1
2
3
4
5
6
7
8
9
5a (H, H)
5b (H, 5-Me)
5c (H, 5-F)
5d (H, 5-Cl)
5e (6-Me, H)
5 f (5-F, H)
5g (5-OMe, H)
5h (6-Me, 5-Me)
5i (5-Me, 5-F)
5j (5-F, 5-Me)
4ca
4cb
4cc
4 cd
4ce
4cf
4cg
4ch
4ci
80
77
61
82
54
78
89
53
60
61
8:1
8:1
8:1
9:1
8:1
8:1
6:1
6:1
10:1
10:1
94
95
94
96
97
95
95
98
95
96
1
2
3
4
5
6
5a none
5a none
5a MeOH
5a EtOH
5a iPrOH
5a’ None
undistilled CHCl3
distilled CHCl3
distilled CHCl3
distilled CHCl3
distilled CHCl3
distilled CHCl3
80
44
65
71
65
62
8:1
8:1
8:1
9:1
8:1
8:1
94
88
91
94
91
94
[a] Reaction conditions: The reaction was conducted on a 0.1 mmol scale
with 6c (2 equiv) and additives (2 equiv; see the Supporting Informa-
tion). Aldehyde 6c was added to a solution of 5a or 5a’ with the catalyst
through a syringe pump over a period of 10 h at 08C. [b] Yield of isolated
products. [c] Determined by 1H NMR spectroscopy. [d] The ee value was
determined by HPLC analysis.
10
4cj
[a] Reaction conditions: Reaction was conducted on a 0.1 mmol scale
with 6c (2 equiv) in commercial chloroform (undistilled CHCl3). Alde-
hyde 6c was added through a syringe pump over a period of 10 h to a so-
ACHUTNGRENUlNG uACTHUNGRTENNUtG ion of 5 with catalyst at 08C. [b] Yield of isolated products. [c] Deter-
mined by 1H NMR spectroscopy. [d] The ee value was determined by
HPLC analysis.
out in the distilled chloroform. Interestingly, nearly identical
results were observed in comparison with those obtained
from the reACHTUNGTRENNUNGaction of 3-hydroxyoxindole 5a in either undistil-
led chloroform or distilled chloroform mixed with ethanol
(Table 2, entries 1, 4, and 6). On the basis of our calculations
on the mechanism of phosphoric-acid-catalyzed alkylation
reaction reported previously,[11] we proposed that the alcohol
might affect the generation rate of cis/trans vinylogous imi-
nium intermediates in the dehydration step and thereby
exerts an influence on the stereoselection.
The optimized conditions were then applied to the direct
alkylation of various 3-hydroxyoxindoles (Table 3). Signifi-
cantly, the protocol tolerated a range of 3-hydroxyoxindoles
that bore either electron-withdrawing, neutral, or electron-
donating substituents on the indole or oxindole moiety,
thereby affording products in moderate to good yields and
with excellent enantioselectivities and synthetically useful
diastereoselectivities (Table 3, entries 1–7). Moreover, the
presence of two substituents on both the indole and oxin-
dole moieties also participated in this alkylation reaction
with high levels of stereochemical outcomes (Table 3, en-
tries 8–10).
Scheme 2. Total synthesis of (+)-gliocladin C. Reaction conditions:
a) NaBH4, MeOH, 08C; b) TBSCl, imidazole, CH2Cl2, 408C; c) (Boc)2O,
4-dimethylaminopyridine (DMAP), CH2Cl2, RT; d) NaBH4, MeOH, 0 to
458C; e) HCACTHNUGTRENUNG(OMe)3, PPTS, MeOH, 658C; f) TBAF, THF, RT;
g) Pd(OH)2/C, H2, MeOH; and h) NaIO4, MeOH/H2O.
Most importantly, the organocatalytic reaction could be
applied to the enantioselective total synthesis of (+)-gliocla-
din C (Scheme 2). The reduction of the chiral aldehyde 4ca
obtained from the current alkylation reaction of 5a and 6c
Chem. Eur. J. 2013, 19, 3319 – 3323
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L.-Z. Gong et al.
[3] D. Greiner, T. Bonaldi, R. Eskeland, E. Roemer, A. Imhof, Nat.
Chem. Biol. 2005, 1, 143–145.
[4] P. Ruiz-Sanchis, S. A. Savina, F. Albericio, M. ꢁlvarez, Chem. Eur.
J. 2011, 17, 1388.
to the corresponding alcohol and followed by protection
with a tert-butyldimethylsilyl (TBS) group afforded 9 in
90% yield over two steps. The introduction of two tert-buty-
loxycarbonyl (Boc) groups on nitrogen atoms of 9 furnished
10 in a 95% yield. Then, the reduction of the oxindole car-
bonyl group with sodium borohydride (NaBH4) produced 11
in a 5:1 diastereomeric ratio. The treatment of 11 with tri-
methyl orthoformate in the presence of 10 mol% of
[5] a) A. D. Lebsack, J. T. Link, L. E. Overman, B. A. Stearns, J. Am.
Chem. Soc. 2002, 124, 9008–9009; b) L. E. Overman, E. A. Peterson,
Angew. Chem. 2003, 115, 2629–2632; Angew. Chem. Int. Ed. 2003,
42, 2525–2528; c) J. J. Kodanko, L. E. Overman, Angew. Chem.
2003, 115, 2632–2635; Angew. Chem. Int. Ed. 2003, 42, 2528–2531;
d) A. Huang, J. J. Kodanko, L. E. Overman, J. Am. Chem. Soc. 2004,
126, 14043–14053; e) J. E. Delorbe, S. Y. Jabri, S. M. Mennen, L. E.
Overman, F. Zhang, J. Am. Chem. Soc. 2011, 133, 6549–6552.
[6] a) M. Movassaghi, M. A. Schmidt, Angew. Chem. 2007, 119, 3799–
3802; Angew. Chem. Int. Ed. 2007, 46, 3725–3728; b) M. Movassa-
ghi, M. A. Schmidt, J. A. Ashehurst, Angew. Chem. 2008, 120, 1507–
1509; Angew. Chem. Int. Ed. 2008, 47, 1485–1487; c) J. Kim, J. A.
Ashenhurst, M. Movassaghi, Science 2009, 324, 238–241; d) J. Kim,
M. Movassaghi, J. Am. Chem. Soc. 2010, 132, 14376–14378; e) M.
Movassaghi, O. K. Ahmad, S. P. Lathrop, J. Am. Chem. Soc. 2011,
133, 13002–13005.
pyridineACHTUNGTRENNUNGium p-toluenesulfonate (PPTS) led to the formation
of 12 in an 89% yield. The O-protecting groups in 12 were
cleanly removed to generate diol 13 in an overall yield of
90% by treatment with tetra-n-butylammonium fluoride
(TBAF) in THF and subsequently subjecting it to hydroge-
nolysis catalyzed by Pd(OH)2/C. The indoline aldehyde 14,
the key intermediate (Overman intermediate), was success-
fully accessed by the oxidative cleavage of the diol 13 with
sodium periodate (NaIO4). Finally, (+)-gliocladin C was syn-
thesized from 14 following the Overman procedure.[5e] The
total synthesis was accomplished within 12 steps from readi-
ly available starting materials, and (+)-gliocladin C was ob-
tained in an overall 19% yield. The spectroscopy and the
optical rotation of the synthetic (+)-gliocladin C were in
agreement with the data reported in the literature.[2,5e,8,9]
In conclusion, we have established a highly enantioselec-
tive alkylation reaction of 3-hydroxyoxindoles with enaliza-
ble aldehydes promoted by the combined catalyst of a chiral
primary amine and phosphoric acid, thereby providing an
efficient approach to access multiply functionalized 3,3’-di-
[7] L. E. Overman, Y. Shin, Org. Lett. 2007, 9, 339–341.
[8] L. Furst, J. M. R. Narayanam, C. R. J. Stephenson, Angew. Chem.
2011, 123, 9829–9833; Angew. Chem. Int. Ed. 2011, 50, 9655–9659.
[9] N. Boyer, M. Movassaghi, Chem. Sci. 2012, 3, 1798–1803.
[10] B. M. Trost, J. Xie, J. D. Sieber, J. Am. Chem. Soc. 2011, 133, 20611–
20622. “
[11] G. Guo, J. Song, J. Huang, P. Chen, S. Luo, L. Z. Gong, Angew.
Chem. 2012, 124, 1070–1074; Angew. Chem. Int. Ed. 2012, 51, 1046–
1050.
[12] For review, see: a) S. Mukherjee, J. W. Yang, S. Hoffmann, B. List,
Chem. Rev. 2007, 107, 5471–5569; b) P. Melchiorre, M. Marigo, A.
Carlone, G. Bartoli, Angew. Chem. 2008, 120, 6232–6265; Angew.
Chem. Int. Ed. 2008, 47, 6138–6171. For selected examples of alky-
lation of carbonyl compounds, see: c) R. R. Shaikh, A. Mazzanti, M.
Petrini, G. Bartoli, P. Melchiorre, Angew. Chem. 2008, 120, 8835–
8838; Angew. Chem. Int. Ed. 2008, 47, 8707–8710; d) P. G. Cozzi, F.
Benfatti, L. Zoli, Angew. Chem. 2009, 121, 1339–1342; Angew.
Chem. Int. Ed. 2009, 48, 1313–1316; e) A. Gualandi, E. Emer, M. G.
Capdevila, P. G. Cozzi, Angew. Chem. 2011, 123, 7988–7992; Angew.
Chem. Int. Ed. 2011, 50, 7842–7846; f) F. Benfatti, E. Benedetto,
P. G. Cozzi, Chem. Asian J. 2010, 5, 2047; g) L. Zhang, L. Cui, X. Li,
J. Li, S. Luo, J.-P. Cheng, Chem. Eur. J. 2010, 16, 2045; h) B. Han,
Y.-C. Xiao, Y. Yao, Y.-C. Chen, Angew. Chem. 2010, 122, 10387–
10389; Angew. Chem. Int. Ed. 2010, 49, 10189–10191; i) J. Xiao,
Org. Lett. 2012, 14, 1716–1719.
ACHTUNGTRENNUNGsubstituted oxindoles, which can function as building blocks
for the total synthesis of natural products and biologically
active molecules. The enantioselective total synthesis of
(+)-gliocladin C has been accomplished in 12 steps from
3-hydroxyoxindole in 19% overall yield by means of this
synthetic method.
[13] For a review on primary amine catalysis, see: a) L.-W. Xu, J. Luo, Y.
Lu, Chem. Commun. 2009, 1807–1821; for reviews focusing on the
reasons that have brought about the development of cinchona-based
primary amines, see: b) L. Jiang, Y.-C. Chen, Catal. Sci. Technol.
2011, 1, 354–365; c) G. Bartoli, P. Melchiorre, Synlett 2008, 1759–
1771; d) Y.-C. Chen, Synlett 2008, 1919–1930; e) P. Melchiorre,
Angew. Chem. 2012, 124, 9886–9909; Angew. Chem. Int. Ed. 2012,
51, 9748–9770.
Acknowledgements
We are grateful for financial support from NSFC (21232007), MOST (973
Program, 2009CB825300), the Ministry of Education, and the Chinese
Academy of Sciences.
Keywords: alkaloids
· amines · asymmetric catalysis ·
[14] a) W. Chen, W. Du, L. Yue, R. Li, Y. Wu, L.-S. Ding, Y.-C. Chen,
Org. Biomol. Chem. 2007, 5, 816–821; b) S. H. McCooey, S. J.
Connon, Org. Lett. 2007, 9, 599–602; c) J.-W. Xie, W. Chen, R. Li,
M. Zeng, W. Du, L. Yue, Y.-C. Chen, Y. Wu, J. Zhu, J.-G. Deng,
Angew. Chem. 2007, 119, 393–396; Angew. Chem. Int. Ed. 2007, 46,
389–392; d) G. Bartoli, M. Bosco, A. Carlone, F. Pesciaioli, L.
Sambri, P. Melchiorre, Org. Lett. 2007, 9, 1403; e) F. Pesciaioli, F. D.
Vincentiis, P. Galzerano, G. Bencivenni, G. Bartoli, A. Mazzanti, P.
Melchiorre, Angew. Chem. 2008, 120, 8831–8834; Angew. Chem. Int.
Ed. 2008, 47, 8703–8706; f) X. Lu, Y. Liu, B. Sun, B. Cindric, L.
Deng, J. Am. Chem. Soc. 2008, 130, 8134–8135; g) R. P. Singh, K.
Bartelson, Y. Wang, H. Su, X. Lu, L. Deng, J. Am. Chem. Soc. 2008,
130, 2422–2423; h) G. Bencivenni, L. Wu, A. Mazzanti, B. Gianni-
chi, F. Pesciaioli, M. Song, G. Bartoli, P. Melchiorre, Angew. Chem.
2009, 121, 7336–7339; Angew. Chem. Int. Ed. 2009, 48, 7200–7203;
i) L. Wu, G. Bencivenni, M. Mancinelli, A. Mazzanti, G. Bartoli, P.
phosphoric acid · total synthesis
[1] a) G. A. Cordell, J. E. Saxton, The Alkaloids: Chemistry and Physi-
ology, Vol. 20, New York, 1981, p. 3–295; b) T. Hino, M. Nakagawa,
The Alkaloids: Chemistry and pharmacology, Vol. 34, New York,
1989, pp. 1–75; c) T. Sevenet, J. Pusset, The Alkaloids: Chemistry
and Pharmacology, Vol. 48, New York, 1996, pp. 1–73; d) U. Antho-
ni, C. Christophersen, P. H. Nielsen, Alkaloids: chemical and Biolog-
ical Perspectivese, Vol. 13, NewYork, 1999, pp. 163–236; e) D. Crich,
A. Banerjee, Acc. Chem. Res. 2007, 40, 151–161; f) A. Steven, L. E.
Overman, Angew. Chem. 2007, 119, 5584–5605; Angew. Chem. Int.
Ed. 2007, 46, 5488–5508.
[2] Y. Usami, J. Yamaguchi, A. Numata, Heterocycles 2004, 63, 1123–
1129.
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Construction of Hexahydropyrroloindole
COMMUNICATION
Melchiorre, Angew. Chem. 2009, 121, 7332–7335; Angew. Chem. Int.
Ed. 2009, 48, 7196–7199; j) P. Galzerano, F. Pesciaioli, A. Mazzanti,
G. Bartoli, P. Melchiorre, Angew. Chem. 2009, 121, 8032–8034;
Angew. Chem. Int. Ed. 2009, 48, 7892–7894; k) G. Bergonzini, S.
Vera, P. melchiorre, Angew. Chem. 2010, 122, 9879–9882; Angew.
Chem. Int. Ed. 2010, 49, 9685–9688; l) G. Bencivenni, P. Galzerano,
A. Mazzanti, G. Bartoli, P. Melchiorre, Proc. Natl. Acad. Sci. USA
2010, 107, 20642–20647.
Li, J. Tian, Y. Peng, Angew. Chem. 2012, 124, 1935–1938; Angew.
Chem. Int. Ed. 2012, 51, 1899–1902.
[16] J.-W. Xie, X. Huang, L.-P. Fan, D.-C. Xu, X.-S. Li, H. Su, Y.-H. Wen,
Adv. Synth. Catal. 2009, 351, 3077–3082.
[17] X. Tian, C. Cassani, Y. Liu, A. Moran, A. Urakawa, P. Galzerano,
E. Arceo, P. Melchiorre, J. Am. Chem. Soc. 2011, 133, 17934–17941.
[18] O. Lifchits, C. M. Reisinger, B. List, J. Am. Chem. Soc. 2010, 132,
10227–10229.
[15] a) M. Rueping, B. J. Nachtsheim, S. A. Moreth, M. Bolte, Angew.
Chem. 2008, 120, 603–606; Angew. Chem. Int. Ed. 2008, 47, 593–
596; b) F. Sun, M. Zeng, Q. Gu, S. You, Chem. Eur. J. 2009, 15,
8709–8712; c) Q.-X. Guo, Y.-G. Peng, J.-W. Zhang, L. Song, Z.
Feng, L.-Z. Gong, Org. Lett. 2009, 11, 4620–4623; d) C. Guo, J.
Song, L.-Z. Gong, Angew. Chem. 2010, 122, 5690–5694; Angew.
Chem. Int. Ed. 2010, 49, 5558–5562; e) B. Xu, Z. Guo, W. Jin, Z.
Wang, Y. Peng, Q. Guo, Angew. Chem. 2012, 124, 1083–1086;
Angew. Chem. Int. Ed. 2012, 51, 1059–1062; f) L. Song, Q. Guo, X.
[19] For review, see: a) D. Uraguchi, M. Terada, J. Am. Chem. Soc. 2004,
126, 5356–5357; b) T. Akiyama, J. Itoh, K. Yokota, K. Fuchibe,
Angew. Chem. 2004, 116, 1592–1594; Angew. Chem. Int. Ed. 2004,
43, 1566–1568; c) T. Akiyama, Chem. Rev. 2007, 107, 5744–5758;
d) A. G. Doyle, E. Jacobsen, Chem. Rev. 2007, 107, 5713–5743;
e) M. Terada, Chem. Commun. 2008, 4097–4112; f) M. Terada, Syn-
thesis 2010, 1929–1982.
Received: December 20, 2012
Published online: February 10, 2013
Chem. Eur. J. 2013, 19, 3319 – 3323
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