Sequential catalyst phosphine/secondary amine promoted [1+4]/rearrangement domino reaction for the construction of (2H)-pyrans and 2-Oxabicyclo[2.2.2]oct- 5-ene skeletons

Article abstract of DOI:10.1002/ejoc.201301872

Sequential catalysis of a [2+4] reaction between a Baylis-Hillman carbonate and a β,γ-unsaturated α-oxo ester for the synthesis of 2-methyl-2H-pyran was developed. The use of a Morita-Baylis-Hillman carbonate as a C₂ synthon is first disclosed in this reaction. This method offers a new approach to the construction of 2-methyl-2H-pyrans and 2-oxabicyclo[2.2.2]oct-5-ene skeletons. Sequential catalysis for challenging skeletons: A phosphine/secondary amine catalyzed [1+4]/rearrangement process is developed to construct challenging (2H)-pyrans and 2-oxabicyclo[2.2.2]oct-5- enes. In this reaction, a Morita-Baylis-Hillman carbonate is first used as a C₂ synthon. The rearrangement process from 2,3-dihydrofurans to (2H)-pyrans is investigated by DFT calculations. Boc = tert-butoxycarbonyl; EWG = electron-withdrawing group. Copyright

Full text of DOI:10.1002/ejoc.201301872

SHORT COMMUNICATION
DOI: 10.1002/ejoc.201301872
Sequential Catalyst Phosphine/Secondary Amine Promoted
[1+4]/Rearrangement Domino Reaction for the Construction of (2H)-Pyrans
and 2-Oxabicyclo[2.2.2]oct-5-ene Skeletons
Peizhong Xie,[a] Jie Yang,[a] Jie Zheng,[a] and You Huang*[a]
Keywords: Phosphanes / Domino reactions / Rearrangement / Cycloaddition / Oxygen heterocycles
Sequential catalysis of a [2+4] reaction between a Baylis–
Hillman carbonate and a β,γ-unsaturated α-oxo ester for the
synthesis of 2-methyl-2H-pyran was developed. The use of
a Morita–Baylis–Hillman carbonate as a C2 synthon is first
disclosed in this reaction. This method offers a new approach
to the construction of 2-methyl-2H-pyrans and 2-oxabi-
cyclo[2.2.2]oct-5-ene skeletons.
stance, the fungal metabolites SB238569 from C. funicola
TCF6040 are inhibitors of several bacterial metallo-β-lac-
Introduction
The 2H-pyran skeleton, which is widespread in natural tamases and potential guiding structures for antibiotic re-
products[1] (Figure 1), is a rich source of inspiration for the search.[2a] In addition, the importance of 2-methyl-2H-
discovery of pharmaceutically relevant molecules and as pyrans in synthetic chemistry is also well illustrated by the
probes for the investigation of chemical biology.[1a,2] For in- general occurrence of these motifs in the synthesis of the 2-
Figure 1. 2H-Pyrans in natural products; they also serve as key intermediates in organic synthesis.
[a] State Key Laboratory and Institute of Elemento-organic
oxabicyclo[2.2.2]oct-5-ene skeleton;[1,3] this is a core skel-
Chemistry, Nankai University,
eton of many biologically active compounds, such as torrey-
anic acid, which was found to be cytotoxic against 25 dif-
ferent human cancer cell lines.[4] However, the 2H-pyran
motif is an ongoing challenging target in organic synthesis,
Tianjin 300071, China
E-mail: hyou@nankai.edu.cn
http://skleoc.nankai.edu.cn/professors/huangy/index.html
Supporting information for this article is available on the
WWW under http://dx.doi.org/10.1002/ejoc.201301872.
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© 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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P. Xie, J. Yang, J. Zheng, Y. Huang
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as it is quite reactive and has the tendency to undergo re-
versible electrocyclic ring opening or dimerization.[1,2b,5]
The synthetic challenges posed by natural products and an-
alogues intermediates thereof call for the development of
new synthetic methods. To date, a few approaches including
tandem Stille/oxo electrocyclization[6] and a myriad of for-
mal [3+3] cycloadditions involving 1,3-dicarbonyl deriva-
tives have been described.[1d,2b,7] Nonetheless, a large
number of transformation steps and limited access to start-
ing materials still restrict their widespread application.[2b]
All of these techniques offer unique opportunities to dis-
cover novel strategies for the formation of 2H-pyrans.
Recently, sequential/relay catalysts,[8a–8e] which work in
Scheme 1. The transformation from 2,3-dihydrofurans into 2H-
pyrans.
an almost biomimetic-like manner, have enabled novel dictory result (Table 1, Entry 3). To confirm whether the
transformations beyond those possible with single catalytic 2H-pyran was generated from the 2,3-dihydrofuran in the
systems and have emerged as a viable and efficient approach presence of Me2NH, the 2,3-dihydrofuran was isolated and
to complex molecular architectures.[8f–8r] Moreover, phos- then subjected to Me2NH. As expected, 4a was obtained in
phine-mediated domino reactions have shown remarkable 74% yield under these conditions (Scheme 1). Other amines
performance in the construction of cyclic and heterocyclic (Table 1, Entries 5–9) and a sterically hindered secondary
compounds,[9] but few sequential catalytic systems concern- amine (Table 1, Entry 9) were inefficient in this transforma-
ing phosphine have been realized.[10] Herein, we report the tion; pyrrolidine gave the best result. Primary amines gave
first phosphine/secondary amine sequential catalyst pro- diminished yields. Upon adding the phosphine catalyst and
moted [1+4]/rearrangement process for the construction of pyrrolidine stepwise, the yield of 4a improved to 78%.
highly functionalized 2H-pyrans and 2-oxabicyclo[2.2.2]- Decreasing or increasing the catalyst loading (Table 1, En-
oct-5-enes. Moreover, density functional theory (DFT) tries 12–14) and the reaction temperature (Table 1, En-
studies give an understanding of the mechanism of the sec- tries 15 and 16) did not further improve the overall per-
ondary amine catalyzed rearrangement process.
formance of this catalytic protocol. Tertiary amines pro-
vided lower yields or no product (Table 1, Entries 17–19).
Inorganic bases were ineffective in this reaction (Table 1,
Entries 20 and 21).
Results and Discussion
To ascertain the generality of the domino reaction, we
Morita–Baylis–Hillman carbonates 2 (Boc = tert-butoxy- examined reactions between various types of substituted
carbonyl), as a result of their convenient preparation and β,γ-unsaturated α-oxo esters 1 and Morita–Baylis–Hillman
diverse reactivity, have emerged as appealing and powerful carbonates 2. In most cases, the reactions proceeded
building blocks in phosphine-mediated reactions.[11] For ex- smoothly to afford the desired products in modest to high
ample, Lu’s pioneering work, in addition to other extensive yields (Table 2). The electronic properties (see 4a–f) and the
work, disclosed that Morita–Baylis–Hillman carbonates position of the substituents (see 4a,g–k) on 1 had a limited
could serve as 1,3-dilopar C3 synthons in [3+n] (n = 2, 3, effect on the process. Substrates with strong electron-with-
4, 6) reactions.[11a–11j] Recently, the use of Morita–Baylis– drawing or electron-donating substituents (see 4e,f,o) also
Hillman carbonates as 1,1-dipolar C1 synthons[11k–11n] was delivered the desired products, albeit in lower yields. How-
developed independently by Zhang[11k] and our group.[11l] ever, sterics on 2 were found to influence the yield and reac-
Upon further investigation, we realized the tunable domino tion time negatively (see 4n). In addition, the yields were
reaction for the selective construction of 2,3-dihydrofurans more sensitive to the size of the ester substituent of 2 than
and multiaryl compounds.[12] During the course of our that of 1 (see 4l–n). Moreover, (1E,5E)-1,6-bis(4-bromo-
study, byproduct 2H-pyrans were detected along with the phenyl)hexa-1,5-diene-3,4-dione also gave the desired
major [1+4] cycloaddition 2,3-dihydrofuran products product in good yield (see 4p). The incorporation of a phos-
(Scheme 1).[12b] This result suggested that Morita–Baylis– phonate was also well tolerated (see 4q). Heteroaryl- (i.e.,
Hillman carbonates must have a distinct reactivity (C2 syn- furanyl- and thiophenyl-) -substituted β,γ-unsaturated α-
thon) towards 2H-pyrans.
oxo esters were also employed in this domino reaction (see
Our initial investigation started with an attempt to im- 4r,s). However, if 1 was substituted with an alkyl (R1 = Me)
prove the chemoselectivity and yield of 2H-pyran 4a. Upon group [i.e., (E)-diethyl but-2-enoylphosphonate], only for-
exposure to H2O (2.0 equiv.), the desired product 4a was mal Rauhut–Currier product 4t was obtained, rather than
isolated in 29% yield. To the best of our knowledge, N,N- the ideal 2-methyl-2H-pyran (see the Supporting Infor-
dimethylformamide (DMF)[13] as a solvent is unstable in mation).
the presence of H2O and releases Me2NH and HCOOH.
The utility of the generated 2-methyl-2H-pyrans was
The effect of Me2NH and HCOOH was then investigated. demonstrated by application to the synthesis of 2-oxabi-
Me2NH was found to be a competent coupling catalyst cyclo[2.2.2]oct-5-ene skeletons, which were successfully ob-
(Table 1, Entry 4), whereas HCOOH gave a totally contra- tained in high yield from 2-methyl-2H-pyrans 4 through a
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2H-Pyrans and 2-Oxabicyclo[2.2.2]oct-5-ene Skeletons
Table 1. Determination of the optimal catalyst and conditions.[a]
Table 2. Scope of the one-pot reaction.[a]
Entry
Cat. II (mol-%)
t (t2)
[h]
Yield 3a/4a
[%][b]
1
2
3
4
5
6
7
8
9
–
4
4
4
4
10
8
7
12
8
86:4
33:29
H2O (200)
HCOOH (20)
Me2NH (20)
l-proline (20)
Et2NH (20)
pyrrolidine (20)
piperidine (20)
iPr2NH (20)
EtNH2(20)
43:trace
trace:65
68:trace
trace:61
trace:67
trace:67
83:trace
17:21
10
15
11[c]
12[c]
13[c]
14[c,d]
15[c.e]
16[c,f]
17[c]
18[c]
19[c]
20[c]
21[c]
pyrrolidine (20)
pyrrolidine (50)
pyrrolidine (10)
pyrrolidine (20)
pyrrolidine (20)
pyrrolidine (20)
DABCO (20)
NEt3 (20)
1.5 (1.0)
1.5 (10 min)
1.5 (3.5)
1.5 (30 min)
1.5 (2.0)
1.5 (1.0)
1.5 (2.0)
1.5 (5.0)
1.5 (5.0)
1.5 (2.0)
1.5 (2.0)
trace:78
trace:68
trace:77
trace:80
trace:70
trace:71
trace:65
85:/trace
83:trace
trace:trace
trace:trace
DBU (20)
Cs2CO3 (20)
K2CO3 (20)
[a] Reaction conditions: unless otherwise specified, see the Experi-
mental Section. EWG = electron-withdrawing group. [b] PPh3
(20 mol-%) was used. [c] P(p-ClC6H4)3 (20 mol-%) was used.
[d] PPh3 (10 mol-%) was used.
[a] Unless otherwise noted, the reaction was performed on a
0.5 mmol scale in solvent (3.0 mL) at 80 °C. The ratio of 1/2 was
1.0:2.0. Me2NH (33% aqueous solution). DABCO = 1,4-diazabicy-
clo[2.2.2]octane; DBU = 1,8-diazabicyclo[5.4.0]undec-7-ene; Cat. II
= 2nd catalyst in the sequential catalysis. [b] Yield of isolated prod-
uct. [c] After completing the formation of the 2,3-dihydrofuran,
Cat. II was then added. [d] 5.0 mL of solvent was used. [e] The
temperature was raised to 120 °C after Cat. II was added. [f] The
temperature changed to 50 °C after Cat. II was added.
Table 3. Sequential-catalytic/single-flask process for the synthesis
of 2-oxabicyclo[2.2.2]oct-5-ene skeletons.[a]
simple Diels–Alder reaction (Table 3; products 5a,[14] 5b,
and 5c). In addition, a three-component reaction of β,γ-
unsaturated α-oxo ester 1, Morita–Baylis–Hillman carbon-
ate 2, and 1-phenyl-1H-pyrrole-2,5-dione was preliminary
investigated. As shown in Table 2, the sequential-catalytic/
single-flask process performed well for the synthesis of 2-
oxabicyclo[2.2.2]oct-5-enes 5a,d,e.
According to our experimental results (Scheme 1) and
some related studies,[11k–11n,12] we propose the following
mechanism. Phosphine initiates this transformation
through [1+4] annulation to afford the 2,3-dihydrofur-
ans.[12b] This is followed by an isomerization process in the
presence of a secondary amine. To gain insight into the
mechanism, pyrrolidine-catalyzed isomerization from the
2,3-dihydrofurans to the 2H-pyrans was studied by DFT
calculations[15] (Figure 2, see the Supporting Information
for details). All of the DFT calculations were performed
with the Gaussian 03 program package.[16a] Geometry opti-
mization of all the minima and transition states involved
were performed at the B3LYP level of theory with the 6-
[a] Reaction conditions: see the Experimental Section. Yields in pa-
rentheses are the results of the direct Diels–Alder reactions from
31+G(d) basis set.[16b,16c] The vibrational frequencies were the 2-methyl-2H-pyrans.
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P. Xie, J. Yang, J. Zheng, Y. Huang
SHORT COMMUNICATION
Figure 2. Proposed mechanism for the rearrangement process and the DFT-computed energy surfaces.
computed at the same level of theory to check whether each 2H-pyrans could be easily converted into important biolo-
optimized structure was an energy minimum or a transition gically active 2-oxabicyclo[2.2.2]oct-5-ene molecular skel-
state and to evaluate its zero-point vibrational energy etons.
(ZPVE).
Calculations indicated that ring opening of 3 in the pres-
ence of a secondary amine was stepwise. The secondary
amine first attacks 3 by passing a barrier (see TS1) of
Experimental Section
32.9 kcalmol–1.
Resulting intermediate IM1 is
General Procedure for the Synthesis of 2H-Pyrans 4: Tris(4-
chlorophenyl)phosphine (0.05 mmol, 0.1 equiv.) was added to a
mixture of β,γ-unsaturated α-oxo ester 1 (0.5 mmol, 1.00 equiv.)
and allylic carbonate 2 (2.00 equiv.) in DMF (3.0 mL). The re-
sulting suspension was maintained at 80 °C until the formation of
2,3-dihydrofuran 3 was complete (as monitored by TLC). Pyrroli-
dine (0.1 mmol, 0.2 equiv.) was then added, and the reaction mix-
ture was maintained at 80 °C until the transformation was com-
plete [transformation of the 2,3-dihydrofuran into the (2H)-pyran
was monitored by TLC]. Dichloromethane (30 mL) was added to
the resulting mixture, which was then washed with water (3ϫ
10 mL). The organic layer was separated and dried with sodium
sulfate. After filtration and concentration, the residue was purified
by column chromatography on silica gel (gradient eluant: petro-
leum ether/ethyl acetate, 15:1–10:1) to afford 2H-pyran 4.
16.2 kcalmol–1 less stable than 3 + cat. The following ring-
opening process (i.e., IM1–TS2–IM2) crossing a barrier (see
TS2) of 28.2 kcalmol–1 is assisted by hydrogen-bonding in-
teraction. Subsequently, proton transfer from the nitrogen
atom to the oxygen atom occurs easily to give intermediate
IM3. Finally, facile rearrangement and oxa-6π electro-
cyclization delivers the final 2H-pyran product. The re-
arrangement process, which is catalyzed by the secondary
amine and which converts dihydrofurans into pyrans, is
exothermic by 19.6 kcalmol–1 and exergonic by
17.8 kcalmol–1.
Conclusions
General Procedure for the Synthesis of 2-Oxabicyclo[2.2.2]oct-5-ene
in One Pot: PPh3 (0.10 mmol, 0.2 equiv.) was added to a mixture
We developed a novel method for the construction of
functionalized 2H-pyrans. In this method, phosphine and of β,γ-unsaturated α-oxo ester 1 (0.5 mmol, 1.00 equiv.) and allylic
carbonate 2 (2.00 equiv.) in DMF (3.0 mL). The resulting suspen-
sion was maintained at 80 °C until the formation of 2,3-di-
hydrofuran 3 was complete (as monitored by TLC). Pyrrolidine
(0.025 mmol, 0.05 equiv.) and 1-phenyl-1H-pyrrole-2,5-dione
(0.75 mmol, 1.5 equiv.) were then added, and the reaction mixture
was maintained at 110 °C until the transformation was complete
(as monitored by TLC). Dichloromethane (30 mL) was then added
to the resulting mixture, which was washed with water (3ϫ 10 mL).
The organic layer was separated and dried with sodium sulfate.
After filtration and concentration, the residue was purified by col-
secondary amine catalysts worked in a sequential manner,
that is, the phosphine initiated a domino reaction of allylic
carbonates and β,γ-unsaturated α-oxo esters through [1+4]
annulation to give 2,3-dihydrofurans, which was followed
by a secondary amine catalyzed rearrangement process to
produce 2H-pyrans in one pot. The mechanism of the re-
arrangement process from 2,3-dihydrofurans to 2H-pyrans
was investigated by DFT calculations. Moreover, a Morita–
Baylis–Hillman carbonate was for the first time used as a
C2 synthon in this reaction. We also demonstrated that the umn chromatography.
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2H-Pyrans and 2-Oxabicyclo[2.2.2]oct-5-ene Skeletons
Q. Cai, Z.-A. Zhao, S.-L. You, Angew. Chem. 2009, 121, 7564–
7567; Angew. Chem. Int. Ed. 2009, 48, 7428–7431; k) S. P.
Lathrop, T. Rovis, J. Am. Chem. Soc. 2009, 131, 13628–13630;
l) H. Jiang, P. Elsner, K. L. Jensen, A. Falcicchio, V. Marcos,
K. A. Jørgensen, Angew. Chem. 2009, 121, 6976–6980; Angew.
Chem. Int. Ed. 2009, 48, 6844–6848; m) Z.-Y. Han, H. Xiao,
X.-H. Chen, L.-Z. Gong, J. Am. Chem. Soc. 2009, 131, 9182–
9183; n) M. Terade, Y. Toda, J. Am. Chem. Soc. 2009, 131,
6354–6355; o) S. Belot, K. A. Vogt, C. Besnard, N. Krause, A.
Alexakis, Angew. Chem. 2009, 121, 9085–9088; Angew. Chem.
Int. Ed. 2009, 48, 8923–8926; p) J. Zhou, B. List, J. Am. Chem.
Soc. 2007, 129, 7498–7499; q) Y. Huang, A. M. Walji, C. H.
Larsen, D. W. C. MacMillan, J. Am. Chem. Soc. 2005, 127,
15051–15053; r) K. Sorimachi, M. Terada, J. Am. Chem. Soc.
2008, 130, 14452–14453.
For reviews on phosphine-mediated domino reactions, see: a)
X. Lu, C. Zhang, Z. Xu, Acc. Chem. Res. 2001, 34, 535–544;
b) J. L. Methot, W. R. Roush, Adv. Synth. Catal. 2004, 346,
1035–1050; c) X. Lu, Y. Du, C. Lu, Pure Appl. Chem. 2005,
77, 1985–1990; d) V. Nair, R. S. Menon, A. R. Sreekanth, N.
Abhilash, A. T. Biji, Acc. Chem. Res. 2006, 39, 520–530; e)
L. W. Ye, J. Zhou, Y. Tang, Chem. Soc. Rev. 2008, 37, 1140–
1152; f) B. J. Cowen, S. J. Miller, Chem. Soc. Rev. 2009, 38,
3102–3116; g) A. Marinetti, A. Voituriez, Synlett 2010, 174–
194; h) A. Moyano, R. Rios, Chem. Rev. 2011, 111, 4703–4832;
i) S. X. Wang, X. Han, F. Zhong, Y. Wang, Y. Lu, Synlett 2011,
2766–2778; j) Q.-Y. Zhao, Z. Lian, Y. Wei, M. Shi, Chem. Com-
mun. 2012, 48, 1724–1732.
Supporting Information (see footnote on the first page of this arti-
cle): Details of the DFT calculations and spectroscopic data for all
new compounds as well as the crystal structure of 5a.
Acknowledgments
This work was financially supported by the National Natural Sci-
ence Foundation of China (21172115), the Natural Science Foun-
dation of Tianjin (10JCYBJC04000), and the Research Fund for
the Doctoral Program of Higher Education of China
(20120031110002).
[1] For the selected reviews, see: a) C. M. Beaudry, J. P. Malerich,
D. Trauner, Chem. Rev. 2005, 105, 4757–4778; b) R. P. Hsung,
A. V. Kurdyumov, N. Sydorenko, Eur. J. Org. Chem. 2005, 23–
44; c) Y. Tang, J. Oppenheimer, Z. Song, L. You, X. Zhang,
R. P. Hsung, Tetrahedron 2006, 62, 10785; for recent selected
examples, see: d) E. J. Jung, Y. R. Lee, H.-J. Lee, Bull. Korean
Chem. Soc. 2009, 30, 2833–2836 and references cited therein;
e) J. Hu, W. Dong, X.-Y. Wu, X. Tong, Org. Lett. 2012, 14,
5530–5533.
[2] a) H. Dückert, V. Khedkar, H. Waldmann, K. Kumar, Chem.
Eur. J. 2011, 17, 5130; b) Y. R. Lee, D. H. Kim, J.-J. Shim, J. H.
Park, J. S. Cha, C.-S. Lee, Bull. Korean Chem. Soc. 2002, 23,
998–1002; c) P. Magiatis, E. Melliou, A.-L. Skaltsounis, S. Mi-
taku, S. Léonce, P. Renard, A. Pierré, G. Atassi, J. Nat. Prod.
1998, 61, 982–986.
[3] For selected examples, see: a) J. P. Malerich, T. J. Maimone,
G. I. Elliott, D. Trauner, J. Am. Chem. Soc. 2005, 127, 6276–
6283; b) C. Li, R. P. Johnson, J. A. Porco Jr., J. Am. Chem. Soc.
2003, 125, 5095–5106.
[4] a) J. C. Lee, G. A. Strobel, E. Lobkovsky, J. Clardy, J. Org.
Chem. 1996, 61, 3232–3233; b) G. Mehta, S. C. Pan, Org. Lett.
2004, 6, 3985–3988.
[5] a) J. D. Hepworth, Comprehensive Heterocyclic Chemistry
(Eds.: A. R. Katritzky, C. W. Rees, A. J. Boulton, A. McKil-
lop), Pergamon, Oxford, U.K. 1984, vol. 3, p. 737; b) Y. Zhu,
S. Ganapathy, R. S. H. Liu, J. Org. Chem. 1992, 57, 1110–1113;
c) H. Menz, S. F. Kirsch, Org. Lett. 2006, 8, 4795–4797.
[6] a) C. Li, E. Lobkovsky, J. A. Porco Jr., J. Am. Chem. Soc. 2000,
122, 10484–10485; b) M. Shoji, J. Yamaguchi, H. Kakeya, H.
Osada, Y. Hayashi, Angew. Chem. 2002, 114, 3324–3326; An-
gew. Chem. Int. Ed. 2002, 41, 3192–3194; c) J. P. Malerich, D.
Trauner, J. Am. Chem. Soc. 2003, 125, 9554–9555; d) J. P. Ma-
lerich, T. J. Maimone, G. I. Elliott, D. Trauner, J. Am. Chem.
Soc. 2005, 127, 6276–6283; e) U. K. Tambar, T. Kano, J. F. Zep-
ernick, B. M. Stoltz, Tetrahedron 2007, 48, 345–350.
[7] For selected examples, see: a) K. P. Cole, R. P. Hsung, Chem.
Commun. 2005, 5784–5786; b) A. V. Kurdyumov, N. Lin, R. P.
Hsung, G. C. Gullickson, K. P. Cole, N. Sydorenko, J. J.
Swidorski, Org. Lett. 2006, 8, 191–194; c) C. Hubert, J. Mo-
reau, J. Batany, A. Duboc, J.-P. Hurvois, J.-L. Renaud, Adv.
Synth. Catal. 2008, 350, 40–42; d) J. Peña, R. F. Moro, P. Bas-
abe, I. S. Marcos, D. Díez, RSC Adv. 2012, 2, 8041–8049.
[8] For selected recent reviews, see: a) Z. Du, Z. Shao, Chem. Soc.
Rev. 2013, 42, 1337–1378; b) R. C. Wende, P. R. Schreiner,
Green Chem. 2012, 14, 1821–1849; c) C. C. J. Loh, D. Enders,
Chem. Eur. J. 2012, 18, 10212–10225; d) Ł. Albrecht, H. Jiang,
K. A. Jørgensen, Angew. Chem. 2011, 123, 8642–8660; Angew.
Chem. Int. Ed. 2011, 50, 8492–8509; e) J. Zhou, Chem. Asian
J. 2010, 5, 422–434; for some selected recent examples, see: f)
Z.-Y. Han, D.-F. Chen, Y.-Y. Wang, R. Guo, P.-S. Wang, L.-Z.
Gong, J. Am. Chem. Soc. 2012, 134, 6532–6535; g) H. Wu, Y.-
P. He, L.-Z. Gong, Adv. Synth. Catal. 2012, 354, 975–980; h)
Q.-A. Chen, M.-W. Chen, C.-B. Yu, L. Shi, D.-S. Wang, Y.
Yang, Y.-G. Zhou, J. Am. Chem. Soc. 2011, 133, 16432–16435;
i) Q.-A. Chen, D.-S. Wang, Y.-G. Zhou, Y. Duan, H.-J. Fan, Y.
Yang, Z. Zhang, J. Am. Chem. Soc. 2011, 133, 6132–6139; j)
[9]
[10]
[11]
Y. C. Fan, O. Kwon, Org. Lett. 2012, 14, 3264–3267.
Served as a C3 synthon in [3+n] reactions, see: a) Y. Du, X.
Lu, C. Zhang, Angew. Chem. 2003, 115, 1065–1067; Angew.
Chem. Int. Ed. 2003, 42, 1035–1037; b) Y. Du, J. Feng, X. Lu,
Org. Lett. 2005, 7, 1987–1989; c) L.-W. Ye, X.-L. Sun, Q.-G.
Wang, Y. Tang, Angew. Chem. 2007, 119, 6055–6058; Angew.
Chem. Int. Ed. 2007, 46, 5951–5954; d) J. Feng, X. Lu, A.
Kong, Tetrahedron 2007, 63, 6035–6041; e) L.-W. Ye, X. Han,
X.-L. Sun, Y. Tang, Tetrahedron 2008, 64, 1487–1493; f) S.
Zheng, X. Lu, Org. Lett. 2008, 10, 4481–4484; g) S. Zheng, X.
Lu, Tetrahedron Lett. 2009, 50, 4532; h) S. Zheng, X. Lu, Org.
Lett. 2009, 11, 3978–3981; i) H.-P. Deng, Y. Wei, M. Shi, Org.
Lett. 2011, 13, 3348–3351; j) R. Zhou, J. Wang, C. Duan, Z.
He, Org. Lett. 2012, 14, 6134–6137; served as a 1,1-dipolar-
type C1 synthon in [1+4] reactions, see: k) Z. Chen, J. Zhang,
Chem. Asian J. 2010, 5, 1542–1545; l) P. Xie, Y. Huang, R.
Chen, Org. Lett. 2010, 12, 3768–3771; m) J. Tian, R. Zhou, H.
Song, Z. He, J. Org. Chem. 2011, 76, 2374–2378; n) X.-N.
Zhang, H.-P. Deng, L. Huang, Y. Wei, M. Shi, Chem. Commun.
2012, 48, 8664–8666; for examples of phosphine-catalyzed al-
lylation, see: o) C.-W. Cho, J.-R. Kong, M. J. Krische, Org.
Lett. 2004, 6, 1337–1339; p) C.-W. Cho, M. J. Krische, Angew.
Chem. 2004, 116, 6857–6859; Angew. Chem. Int. Ed. 2004, 43,
6689–6691; q) Y.-Q. Jiang, Y.-L. Shi, M. Shi, J. Am. Chem.
Soc. 2008, 130, 7202–7203.
a) P. Xie, Y. Huang, R. Chen, Chem. Eur. J. 2012, 18, 7362–
7366; b) P. Xie, E. Li, J. Zheng, X. Li, Y. Huang, R. Chen,
Adv. Synth. Catal. 2013, 355, 161–169.
S. Ding, N. Jiao, Angew. Chem. 2012, 124, 9360–9371; Angew.
Chem. Int. Ed. 2012, 51, 9226–9237.
CCDC-942013 (for 5a) contains the supplementary crystallo-
graphic 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.
For selected examples in the field of organocatalysis concerning
DFT calculations, see: a) Y. Liang, S. Liu, Y. Z. Xia, Y. H. Li,
Z. X. Yu, Chem. Eur. J. 2008, 14, 4361–4373; b) Y. Z. Xia, Y.
Liang, Y. Y. Chen, M. Wang, L. Jiao, F. Huang, S. Liu, Y. H.
Li, Z. X. Yu, J. Am. Chem. Soc. 2007, 129, 3470–3471; c) E.
Mercier, B. Fonovic, C. Henry, O. Kwon, T. Dudding, Tetrahe-
dron Lett. 2007, 48, 3617–3620; d) T. Dudding, O. Kwon, E.
Mercier, Org. Lett. 2006, 8, 3643–3646; e) L. Zhao, M. Wen,
[12]
[13]
[14]
[15]
Eur. J. Org. Chem. 2014, 1189–1194
© 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
1193

P. Xie, J. Yang, J. Zheng, Y. Huang
SHORT COMMUNICATION
Z.-X. Wang, Eur. J. Org. Chem. 2012, 3587–3597; f) X.-Y.
Chen, W.-W. Wen, S. Ye, Z.-X. Wang, Org. Lett. 2011, 13,
1138–1141.
Morokuma, G. A. Voth, P. Salvador, J. J. Dannenberg, V. G.
Zakrzewski, S. Dapprich, A. D. Daniels, M. C. Strain, O.
Farkas, D. K. Malick, A. D. Rabuck, K. Raghavachari, J. B.
Foresman, J. V. Ortiz, Q. Cui, A. G. Baboul, S. Clifford, J. Cios-
lowski, B. B. Stefanov, G. Liu, A. Liashenko, P. Piskorz, I. Ko-
maromi, R. L. Martin, D. J. Fox, T. Keith, M. A. Al-Laham,
C. Y. Peng, A. Nanayakkara, M. Challacombe, P. M. W. Gill,
B. Johnson, W. Chen, M. W. Wong, C. Gonzalez, J. A. Pople,
Gaussian 03, revision E.01, Gaussian, Inc., Wallingford, CT,
2004; b) A. D. Becke, J. Chem. Phys. 1993, 98, 5648; c) C. Lee,
W. Yang, R. G. Parr, Phys. Rev. B 1988, 37, 785.
[16] a) The DFT calculations were performed by using the
Gaussian 03 program: M. J. Frisch, G. W. Trucks, H. B. Schle-
gel, G. E. Scuseria, M. A. Robb, J. R. Cheeseman, J. A. Mont-
gomery Jr., T. Vreven, K. N. Kudin, J. C. Burant, J. M. Millam,
S. S. Iyengar, J. Tomasi, V. Barone, B. Mennucci, M. Cossi, G.
Scalmani, N. Rega, G. A. Petersson, H. Nakatsuji, M. Hada,
M. Ehara, K. Toyota, R. Fukuda, J. Hasegawa, M. Ishida, T.
Nakajima, Y. Honda, O. Kitao, H. Nakai, M. Klene, X. Li,
J. E. Knox, H. P. Hratchian, J. B. Cross, V. Bakken, C. Adamo,
J. Jaramillo, R. Gomperts, R. E. Stratmann, O. Yazyev, A. J.
Austin, R. Cammi, C. Pomelli, J. W. Ochterski, P. Y. Ayala, K.
Received: December 17, 2013
Published Online: January 23, 2014
1194
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© 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2014, 1189–1194