Stereoselective cyclo-addition reactions of azomethine ylides catalysed by in situ generated Ag(I)/bisphosphine complexes

Article abstract of DOI:10.2298/JSC1001001G

Stereoselective cyclo-addition reactions of azomethine ylides promoted by in situ generated Ag(I)/bisphosphine complexes were studied. Under the optimised conditions, the pyrrolidine products were isolated in up to 84 % yield and with up to 71 % e.e. The

Full text of DOI:10.2298/JSC1001001G

J. Serb. Chem. Soc. 75 (1) 1–9 (2010)
JSCS–3935
UDC 547.416:547.235.2’211+
546.571:66.095.252.091.7
Original scientific paper
Stereoselective cyclo-addition reactions of azomethine ylides
catalysed by in situ generated Ag(I)/bisphosphine complexes
1
#
RONALD GRIGG , SUREN HUSINEC2# and VLADIMIR SAVIĆ1,3
*
*
1Molecular Innovation, Diversity and Automated Synthesis (MIDAS) Centre, Department of
Chemistry, Leeds University, Woodhouse Lane, Leeds LS2 9JT, UK, 2Institute of Chemistry,
Technology and Metallurgy, Centre for Chemistry, P.O. Box 815, Njegoševa 12, 11000
Belgrade, and 3Department of Organic Chemistry, Faculty of Pharmacy,
University of Belgrade, Vojvode Stepe 450, 11000 Belgrade, Serbia
(Received 15 October 2008, revised 10 November 2009)
Abstract: Stereoselective cyclo-addition reactions of azomethine ylides pro-
moted by in situ generated Ag(I)/bisphosphine complexes were studied. Under
the optimised conditions, the pyrrolidine products were isolated in up to 84 %
yield and with up to 71 % e.e. The effects of various reaction variables on the
stereoselectivity were also investigated.
Keywords: azomethine ylides; stereoselectivity; chiral phosphine; Ag(I).
INTRODUCTION
1,3-Dipolar cyclo-addition reactions of metallo-azomethine ylides to elec-
tron deficient alkenes constitute a powerful tool for the preparation of substituted
1
pyrrolidine derivatives. If the metallo-ylide is generated in the presence of a chi-
ral ligand, the pyrrolidine product can be obtained in a stereoselective manner,
Scheme 1.
Scheme 1. Metal catalysed cycloaddition reactions of azomethine ylides.
Pioneering studies of stereoselective cyclo-additions of these ylides employ-
2a
ed the stoichiometric amount of chiral cobalt complexes or a chiral auxilia-
*Corresponding authors. E-mails: r.grigg@leeds.ac.uk; vladimir.savic@pharmacy.bg.ac.rs
# Serbian Chemical Society member.
doi: 10.2298/JSC1001001G
1
Available online at www.shd.org.rs/JSCS/
___________________________________________________________________________________________________________________________
2009 Copyright (CC) SCS

2
GRIGG, HUSINEC and SAVIĆ
1a,b,d,2b–j
3a–p
3q,r
ry.
Recently, more efficient metal
and organo-catalytic
variations
of this transformation have been developed. Various metal salts have been em-
2a
2a
3a–e
3g–l
3m
3n
ployed, such as Co (II), Mn(II), Ag(I),
Cu(I/II),
Au(I), Zn(II),
3o
3p
Ca(II), Ni(II) in conjunction with a range of chiral ligands.
Of particular interest are the Ag(I)-based methods, which afford pyrrolidines
with a high level of enantioselectivity and in good yield, invariably via an endo
transition state. Under the standard conditions (Scheme 1), the use of base is
necessary in order to generate the azomethine ylide, but this may be avoided by
4
employing AgOAc as a Lewis acid. In addition, the selection of a ligand in
conjunction with an Ag(I) salt provides access to both enantiomeric pyrrolidine
5
products. In recent years, the development of Cu(I)/Cu(II) methods provided ad-
ditional valuable synthetic methods, which is reflected in the high level of enan-
3g–l
3h
tioselectivity
and the potential to rationally control exo/endo selectivity.
RESULTS AND DISCUSSION
In this paper, initial results obtained in Ag(I)-promoted, stereoselective cyc-
lo-addition reactions of metallo-azomethine ylides employing the bisphosphine
ligand 1:
6
easily accessible from tartaric acid, are discussed.
The cyclo-addition reactions of azomethine ylides generated from imines
were performed using equimolar amounts of imine, dipolarophile, AgOTf and the
ligand 1 in CH Cl as the solvent in the presence of NEt as a base, Scheme 2
2
2
3
and Table I. The products were isolated by flash chromatography and the e.e. was
1
determined by H-NMR spectroscopy using the chiral shift reagent, (+)-tris[(3-
7
-heptafluoropropylhydroxymethylene)camphorato]europium(III).
Scheme 2. Ag(I)/1 catalysed cyclo-addition reactions of azomethyne ylides.
Available online at www.shd.org.rs/JSCS/
___________________________________________________________________________________________________________________________
2009 Copyright (CC) SCS

REACTIONS OF AZOMETHINE YLIDES
3
Most of the reactions afforded the products in good yields (Table I), with
reaction times of 3–4 h, suggesting that presence of the ligand did not signi-
ficantly affect either the yield or the reaction time. The reaction employing the
S-methylcysteine-derived imine, Table I, entry e, surprisingly, resulted in the re-
covery of the starting materials only. This may be the result of Ag(I) coordination
by the thioether moiety, forming a complex which excluded either N or O coor-
8
dination of the metal centre. Chelate formation involving the iminoester func-
tionality (see Scheme 1) is essential for lowering the pK of the α-C–H bond and
a
1a
the generation of the ylide, a process potentially disrupted by a competitive
coordination of Ag(I) by an additional donor atom. Interestingly, when the thio-
ether containing imine 2f was used, the expected product was isolated in good
yield. This may suggest that the aromatic thioether is a weaker coordinating
agent than the aliphatic one, allowing equilibrium between different species, in-
cluding those leading to the ylide.
TABLE I. Stereoselective Ag(I) catalysed 1,3-dipolar cycloaddition reactions
Entry
a
R (imine 2)
R (product 4)
e.e., %a Yield, %b
2a: R1 = 2-naphthyl
R2 = H
4a: R1 = 2-naphthyl
R2 = H
49
66
64
67
–
69
80
72
84
–
b
c
d
e
2b: R1 = 2-naphthyl
R2 = CH3
4b: R1 = 2-naphthyl
R2 = CH3
2c: R1 = 2-naphthyl
R2 = benzyl
4c: R1 = 2-naphthyl
R2 = benzyl
2d: R1 = 2-naphthyl
R2 = 3-indolylmethyl
2e: R1 = 2-naphthyl
R2 = methylthiomethyl
4d: R1 = 2-naphthyl
R2 = 3-indolylmethyl
4e: R1 = 2-naphthyl
R2 = methylthiomethyl
f
2f: R1 = 2-(methylthio)phenyl 4f : R1 = 2-(methylthio)phenyl
61
74
R2 = CH3
R2 = CH3
a
b
Assigned by 1H-NMR using chiral shift reagent; isolated yield
The observed enantioselectivity ranged from 49 to 67 %. Although the enan-
tioselectivity was lower for the glycine imine 2a compared to the other substi-
tuted imines, 2b, 2c, 2d and 2f, there was no significant difference in the e.e.
between the later ones. This puzzling result could be due to the Thorpe–Ingold
effect which decreases the =N–C–CO angle and increases the steric congestion in
9
the transition state.
The absolute stereochemistry of product 4a (2R, 4R, 5S) was established by
comparison of its optical rotation ([α] –11.3°) with the optical rotation of (2R,
D
4R, 5S)-dimethyl 5-(2-naphthyl)pyrrolidine-2,4-dicarboxylate ([α] –19.5°) syn-
D
10
thesized by a different method. Based on all these results, a transition state was
proposed, Fig. 1. It was assumed that the Ag(I) complex has a 4-coordinate square
planar geometry. The donor atoms comprise the two phosphorus atoms from the
Available online at www.shd.org.rs/JSCS/
___________________________________________________________________________________________________________________________
2009 Copyright (CC) SCS

4
GRIGG, HUSINEC and SAVIĆ
ligand and the nitrogen and the oxygen atoms from the imine. The approach of
the dipolarophile to the re face of the imine via an endo transition state is less
favoured due to steric interactions between the pseudo-axial phenyl group on the
phosphorus and the ester group of the dipolarophile. The si face of the imine is
less shielded due to pseudo-equatorial orientation of the phenyl substituent and,
therefore, the approach of the dipolarophile from this side leads to the observed
product.
Fig. 1. Proposed transition state for the Ag(I)/1 catalysed cycloaddition reactions (the
pyrrolidine ring of the ligand omitted for clarity).
After these initial results, the effects of various reaction parameters on the
enantioselectivity were investigated. Performing the reaction of imine 2b and
acrylate 3 at a lower temperature, Table II, entry a, slightly improved the e.e.
without influencing the reaction yield. At –78 °C, Table II, entry b, the reaction
was very slow and it is likely that the major part of the reaction occurred as the
reaction mixture was gradually warmed up.
TABLE II. The effect of temperature on enantioselectivity
Entry
a
b
Imine
2b
2b
Product
4b
t / °C
–20
–78 to r.t.
e.e., %a
71
71
Yield, %b
78
78
4b
a
b
Assigned by 1H-NMR using chiral shift reagent; isolated yield
Variation of the base gave some unexpected results, Table III. When (R)- or
(S)-N,N,α-trimethylbenzylamine or pyridine (Table III, entries d and e) were
1
used instead of triethylamine, no cyclo-adduct was obtained. The H-NMR spec-
trum of the crude reaction mixture indicated the presence of starting materials
only. This may suggest that the formation of Ag(I) complexes containing these
bases as ligands prevented the coordination of the imine and subsequent forma-
tion of the ylide. Ag(I)/pyridine complexes are known and their stability depends
11
on the coordination number. On the other hand, the benzylamine derivatives
may act as bidentate ligands. The 1:1 complexes of Ag(I) with 2-allylpyridine and
vinyldiphenylphosphine, as well as related complexes, have been reported in the
12
literature. When stronger bases than triethylamine were used, such as DBU,
Available online at www.shd.org.rs/JSCS/
___________________________________________________________________________________________________________________________
2009 Copyright (CC) SCS

REACTIONS OF AZOMETHINE YLIDES
5
sparteine and tetramethyl-t-butylguanidine, Table III, entries a–c, the reaction
times were shorter but, unfortunately, the e.e. slightly decreased. This might indi-
cate that apart from the phosphine/Ag(I) complex catalysed reaction, a reaction
promoted by the base/Ag(I) complex occurred as well. Although steric factors
play an important role in the stability of amine/Ag(I) complexes, increased amine
bulk may stabilise the complex and, therefore, promote the competitive non-ste-
11c,13
reoselective process.
TABLE III. The effect of base on enantioselectivity
Entry
Imine
Product
Base
e.e., %a
Yield, %b
a
b
c
2b
2b
2b
4b
4b
4b
DBU
57
57
49
87
80
88
Sparteine
N t
Bu
Me2N
NMe2
d
2b
2b
4b
4b
–
–
–
–
Ph
NH2c
e
Pyridine
a
b
c
Assigned by 1H-NMR using chiral shift reagent; isolated yield; both (R)- and (S)- enantiomers were surveyed
The proposed transition state model, Fig. 1, suggests that the approach of the
dipolarophile to the dipole is controlled by steric interactions involving the phe-
nyl substituent on the phosphorus and the ester group on the dipolarophile. This
prompted evaluation of bulkier ester functionalities of both the dipole and the
dipolarophile, Scheme 3, Table IV. When imine t-butyl ester 5 was used (Table
IV, entry a), the e.e. was similar to that observed for imine methyl ester 2a
(Scheme 2, Table I, entry a). This may indicate that the imine ester group does
not play a crucial role in inducing the stereoselectivity, which would be expected
based on the proposed transition state. On the other hand, t-butyl acrylate 6b
(Table IV, entry b) was shown to be ineffective in this reaction, affording the
product in only 28 % yield after 4 days. The use of benzyl ester 6a resulted in a
slightly lower e.e. (Table IV, entry c).
Scheme 3. Ag(I)/1 catalysed cycloaddition reactions of azomethine ylides.
Available online at www.shd.org.rs/JSCS/
___________________________________________________________________________________________________________________________
2009 Copyright (CC) SCS

6
GRIGG, HUSINEC and SAVIĆ
In conclusion, the effect of chiral bisphosphine 1 in stereoselective cyclo-ad-
dition reactions of metallo-azomethine ylides generated in the presence of AgOTf
was studied. Under the optimized conditions, pyrrolidine products were obtained
in good yields with up to 71 % e.e.
TABLE IV. Effect of steric factors on the e.e.
Entry
Imine
Acrylate
Product
e.e., %a
Yield, %b
a
b
5
2b
2b
3
6b
6a
7a
7b
7c
c
48
–
57
91
28c
67
c
a
b
Assigned by 1H-NMR using chiral shift reagent; isolated yield; reaction time: 4 days
EXPERIMENTAL
Melting points were determined on a Kofler hot-stage apparatus and are uncorrected.
Microanalyses were obtained using a Carlo Erba Elemental Analyser MOD 1106. Mass spec-
tral data were recorded using a VG-AutiSpec spectrometer operating at 70 eV. Nuclear mag-
netic resonance spectra were recorded at 300 MHz using a General Electric QE300 instrument
and at 400 MHz using a Bruker WP400 instrument. Chemical shift are given in parts per mil-
lion (δ) downfield from tetramethylsilane as the internal standard. Unless otherwise specified,
deuterochloroform was used as the solvent. Silica gel 60 (230–400mesh) was employed for
flash chromatography.
Of the prepared compounds, the imines 2a,14a 2b,14b 2c14c and 2d14c and pyrrolidines
4a–d14c are reported in the literature. Some analytical and spectral data of the newly syn-
thesised compounds are given below.
1
All e.e. values reported in this study were established by H-NMR spectroscopy using
the chiral shift reagent tris[(3-heptafluoropropylhydroxymethylene)-(+)-camphorato]euro-
pium(III). The reagent was added in small portions (2–3 mg) to the CDCl3 solution (NMR
tube) of the product until a good baseline separation of the enantiomeric signals for the methyl
Fig. 2. Separation of the enantiomeric
signals.
Available online at www.shd.org.rs/JSCS/
___________________________________________________________________________________________________________________________
2009 Copyright (CC) SCS

REACTIONS OF AZOMETHINE YLIDES
7
protons of the ester was observed. The experiment was performed using the products dis-
cussed above and the corresponding racemic mixtures. A typical example, Fig. 2, shows the
separation of the COOMe signals for the racemic 4a (Fig. 2a) and the same product obtained
with 49 % e.e. (Fig. 2b).
General procedure for the preparation of imines
A mixture of aldehyde (0.010 mol), amino ester hydrochloride (0.012 mol), triethylamine
(0.018 mol) and anhydrous MgSO4 (3–4 g) in dichloromethane (30 mL) was stirred for 12 h.
The obtained solid was separated by filtration and the filtrate washed with water (2×20 mL).
The organic layer was then dried (MgSO4) and the solvent evaporated under reduced pressure.
When possible, the imines were further purified by distillation or crystallisation. The imines
2f and 5, obtained as colourless oils, were used without further purification.
1
Methyl N-[2-(methylthio)benzylidene]alaninate (2f). H-NMR (CDCl3, δ / ppm): 1.58
(3H, d, J = 7.9 Hz, CCH3), 2.47 (3H, s, SCH3), 3.77 (3H, s, COOCH3), 4.22 (1H, q, J = 7.8
Hz, CH), 7.20–7.42 (3H, m, ArH), 7.98 (1H, d, ArH), 8.82 (1H, s, N=CH). MS (EI) (m/z (%)):
236, M+–1 (1), 205 (8), 182 (26), 167 (33), 141 (11), 128 (22), 119 (28), 98 (59), 85 (63), 72
(33), 55 (79), 43 (100).
t-Butyl N-(2-naphthalenylmethylene)glycinate (5). 1H-NMR (CDCl3, δ / ppm): 1.52 (9H,
s, t-Bu), 4.38 (2H, s, CH2), 7.51 (2H, m, ArH), 7.83 (3H, m, ArH), 8.25 (2H, m, ArH) 8.40
(1H, s, N=CH). MS (EI) (m/z (%)): 269, M+ (8), 212 (28), 168 (100), 154 (21), 141 (83), 127
(22), 115 (19), 84 (6), 57 (71), 41 (56).
General procedure for the cyclo-addition reactions in the presence of AgOTf/phosphine 1
AgOTf (0.10 mmol) was added to a stirred solution of phosphine 1 (0.10 mmol) and
imine (0.10 mmol) in dry CH2Cl2 (5.0 mL). The reaction mixture was stirred at room
temperature for 20 min. Methyl acrylate (0.2–0.3 mmol) was then added followed by base
(0.15–0.2 mmol) and the mixture was stirred at room temperature until thin layer
chromatography indicated the absence of the starting material. The reaction mixture was then
filtered through celite, the filtrate washed with water (2×), dried (MgSO4) and the solvent
evaporated under reduced pressure. The residue was purified by flash chromatography (SiO2,
petroleum ether/ /diethyl ether) to afford the product. The enantiomeric excess was
determined by 1H-NMR spectroscopy using tris[3-(heptafluoropropylhydroxymethylene)-(+)-
camphorato]europium (III) as the chiral shift reagent.
Dimethyl 2-methyl-5-[2-(methylthio)phenyl]pyrrolidine-2,4-dicarboxylate (4f). Flash chro-
matography (SiO2, 1:1 v/v petroleum ether–diethyl ether) afforded the product in 74 % yield
as a pale yellow oil, which solidified upon standing; m.p. 76–80 °C. Anal. Calcd. for
1
C16H21NO4S: C, 59.45; H, 6.50; N, 4.35 %. Found: C, 59.65; H, 6.60; N, 4.2 %. H-NMR
(CDCl3, δ / ppm): 1.58 (3H, s, SCH3), 2.10 (1H, dd, J = 13.8 and 7.5 Hz, 3-H), 2.49 (3H, s,
CH3C), 2.77 (1H, dd, J = 13.7 and 3.0 Hz, 3-H), 3.12 (3H, s, COOCH3), 3.51 (1H, m, 4-H), 3.83
(3H, s, COOCH3), 5.01 (1H, d, J = 7.8 Hz, 5-H), 7.20 (3H, m, ArH), 7.41 (1H, d, J = 7.6 Hz,
ArH). MS (EI) (m/z (%)): 323, M+ (5), 264 (100), 237 (24), 223 (18), 204 (22), 188 (11), 162
(53), 150 (15), 121 (10), 91 (7), 77 (8).
t-Butyl 4-methoxycarbonyl-5-(2-naphthyl)pyrrolidine-2-carboxylate (7a). Flash chroma-
tography (SiO2, 1:1 v/v petroleum ether–diethyl ether) afforded the product in 91 % yield as a
colourless oil which solidified upon standing; m.p. 67–69 °C. Anal. Calcd. for C21H25NO4: C,
70.95; H, 7.05; N, 3.95 %. Found: C, 70.65; H, 7.15; N, 3.70 %. 1H-NMR (CDCl3, δ / ppm):
1.77 (9H, s, t-Bu), 2.45 (2H, m, 3-H), 2.67 (1H, br s, NH), 3.15 (3H, s, COOCH3), 3.42 (1H,
q, J = 7.5 Hz, 4-H), 3.93 (1H, t, J = 7.6 Hz, 2-H), 4.67 (1H, d, J = 7.6 Hz, 5-H), 7.45 (3H, m,
Available online at www.shd.org.rs/JSCS/
___________________________________________________________________________________________________________________________
2009 Copyright (CC) SCS

8
GRIGG, HUSINEC and SAVIĆ
ArH), 7.82 (4H, m, ArH). MS (EI) (m/z (%)): 269, M+ (8), 212 (28), 168 (100), 154 (21), 141
(83), 127 (22), 115 (19), 84 (6), 57 (71) 41 (56).
Benzyl 2-methoxycarbonyl-2-methyl-5-(2-naphthyl)pyrrolidine-4-carboxylate (7c). Flash
chromatography (SiO2, 3:7 v/v petroleum ether-ether) afforded the product in 74 % yield as a
colourless oil which solidified upon standing; m.p. 85.5–87 °C. Anal. Calcd. for C25H25NO4:
C, 74.45; H, 6.20; N, 3.45 %. Found: C, 74.35; H, 6.1; N, 3.25 %. 1H-NMR (CDCl3, δ / ppm):
1.56 (3H, s, CCH3), 2.17 and 2.83 (2×1H, 2×m, 3-H), 3.35 (1H, br s, NH), 3.48 (1H, br m,
4-H), 3.83 (3H, s, COOCH3), 4.39 and 4.61 (2×1H, 2×d, J = 12.0 Hz, CH2Ph), 4.82 (1H, d,
J = 6.6 Hz, 5-H), 6.65 (2H, d, ArH), 7.00 (2H, t, ArH), 7.15 (1H, m, ArH), 7.41 (1H, d, ArH),
7.47 (2H, m, ArH), 7.76 (4H, m, ArH). MS (EI) (m/z (%)): 404, M++1 (4), 344 (100), 298
(11), 241 (65), 208 (36), 181 (70), 155 (11), 140 (20), 91 (97), 65 (12), 42 (20).
Acknowledgement. We thank Leeds University (RG, VS) and the Ministry of Science
and Technological Development of the Republic of Serbia (VS, SH, project numbers: 142071
and 142072) for support.
И З В О Д
СТЕРЕОСЕЛЕКТИВНЕ ЦИКЛОАДИЦИОНЕ РЕАКЦИЈЕ АЗОМЕТИНСКИХ ИЛИДА
КАТАЛИЗОВАНЕ IN SITU ГЕНЕРИСАНИМ Аg(I)/БИСФОСФИНСКИМ КОМПЛЕКСИМА
RONALD GRIGG1, СУРЕН ХУСИНЕЦ2 и ВЛАДИМИР САВИЋ1,3
1Molecular Innovation, Diversity and Automated Synthesis (MIDAS) Centre, Department of Chemistry, Leeds
University, Woodhouse Lane, Leeds LS29JT, UK, 2Institut za hemiju, tehnologiju i metalurgiju, Centar
za hemiju,p. pr. 815, Wego{eva 12, 11000 Beograd i 3Institut za organsku hemiju, Farmaceutski
fakultet, Univerzitet u Beogradu, Vojvode Stepe 450, 11000 Beograd
Проучаване су стереоселективне циклоадиционе реакције азометинских илида катали-
зоване комплексима сребра и бисфосфинског лиганда генерисаних in situ. Пиролидински
деривати изоловани су у добрим приносима и са енантиоселективношћу до 71 %. Проучавани
су такође и ефекти реакционих услова на стереоселективност ових реакција.
(Примљено 15. октобра 2008, ревидирано 10. новембра 2009)
REFERENCES
1. a) R. Grigg, V. Sridharan, Adv. Cycloadditions 3 (1993) 161; b) S. Kanemasa, Synlett
(2002) 1371; c) S. Husinec, V. Savic, Tetrahedron: Asymmetry 16 (2005) 2047; d) G.
Pandey, P. Banerjee, S. Gadre, Chem. Rev. 106 (2006) 4484
2. a) P. Allway, R. Grigg, Tetrahedron Lett. 32 (1991) 5817; b) R. Grigg, Tetrahedron
Asymmetry 6 (1995) 2475; c) G. Pandey, J. K. Laha, G. Lakshmaiah, Tetrahedron 58
(2002) 3525; d) S. Carlsson, H. Hoegberg, J. Chem. Soc. Perkin Trans. 1 (2002) 1076; e)
G. Cravotto, G. B. Giovenzana, T. Pilati, M. Sisti, G. Palmisano, J. Org. Chem. 66 (2001)
8447; f) S. Karlsson, H.-E. Hogberg, Tetrahedron Asymmetry 12 (2001) 1975; g) P. Gar-
ner, O. Dogan, J. W. Youngs, V. O. Kennedy, J. Protasiewicz, R. Zaniewski, Tetrahedron
57 (2001) 71; h) D. Alker, G. Hamblett, L. M. Harwood, S. M. Robertson, D. J. Watkin,
C. E. Williams, Tetrahedron 54 (1998) 6089; i) H. Waldmann, E. Blaeser, M. Jansen, H.
P. Letschert, Chem. Eur. J. 1 (1995) 150; j) R. M. Williams, W. Zhai, D. J. Aldous, S. C.
Aldous, J. Org. Chem. 57 (1992) 6527; k) S. Kanemasa, H. Yamamoto, E. Wada, T.
Sakurai, K. Urushido, Bull. Chem. Soc. Jpn. 63 (1990) 2857; l) D. M. Cooper, R. Grigg,
S. Hargreaves, P. Kennewell, J. Redpath, Tetrahedron 51 (1995) 7791
Available online at www.shd.org.rs/JSCS/
___________________________________________________________________________________________________________________________
2009 Copyright (CC) SCS

REACTIONS OF AZOMETHINE YLIDES
9
3. a) J. M. Longmire, B. Wang, X. Zhang, J. Am. Chem. Soc. 124 (2002) 13400; b) C. Chen,
X. Li, S. Schreiber, J. Am. Chem. Soc. 125 (2003) 1017; c) C. Alemparte, G. Blay, K. A.
Jorgensen, Org. Lett. 7 (2005) 4569; d) W. Zeng, Y. G. Zhou, Tetrahedron Lett. 48
(2007) 4619; e) C. Najera, M. de Gracia Retamosa, J. M. Sansano, Org. Lett. 9 (2007)
4025; f) Y. Oderaotoshi, W. Cheng, S. Fujitomi, Y. Kasano, S. Minakata, M. Komatsu,
Org. Lett. 5 (2003) 5043; g) S. Cabrera, R. G. Arrayas, J. C. Carretero, J. Am. Chem. Soc.
127 (2005) 16394; h) W. Gao, X. Zhang, M. Raghunath, Org. Lett. 7 (2005) 4241; i) X.
Yan, Q. Peng, Y. Zhang, K. Zhang, W. Hong, X. Hou, Y. Wu, Angew. Chem., Int. Ed. 45
(2006) 1979; j) T. Llamas, R. G. Arrayas, J. C. Carretero, Org. Lett. 8 (2006) 1795; k) S.
Cabrera, R. G. Arrayas, B. Martin-Matute, F. P. Cosio, J. C. Carretero, Tetrahedron 63
(2007) 6587; l) S. Fukuzawa, H. Oki, Org. Lett. 10 (2008) 1747; m) A. D. Melhado, M.
Luparia, F. D. Toste, J. Am. Chem. Soc. 129 (2007) 12638; n) A. S. Gothelf, K. V. Got-
helf, R. G. Hazell, K. A. Jorgensen, Angew. Chem. Int., Ed. 41 (2002) 4236; o) S. Saito,
T. Tsubogu, K. Seki, Y. Yamashita, S. Kobayashi, J. Am. Chem. Soc. 130 (2008) 13321;
p) J. Shi, M. Zhao, Z. Lei, M. Shi, J. Org. Chem. 73 (2008) 305; q) L. J. Vicario, S.
Reboredo, D. Badia, L. Carrillo, Angew. Chem., Int. Ed. 46 (2007) 5168; r) M. Xue, X.
M. Zhang, L. Z. Gong, Synlett (2008) 691
4. W. Zeng, Y. Zhou, Org. Lett. 7 (2005) 5055
5. W. Zeng, G. Chen, Y. Zhou, Y. Li, J. Am. Chem. Soc. 129 (2007) 750
6. U. Nagel, E. Kinzel, J. Andrade, G. Prescher, Chem. Ber. 119 (1986) 3326
7. R. R. Fraser in Asymmetric Synthesis, vol. 1, J. D. Morrison, Ed., Academic Press, New
York, 1983, p. 173
8. a) L. D. Petit, K. F. Siddiqui, H. Kozlowski, T. Kowalik, Inorg. Chim. Acta 55 (1981) 87;
b) C. A. McAuliffe, Inorg. Chem. 12 (1973) 1699; c) D. F. S. Natusch, L. J. Porter, J.
Chem. Soc. A (1971) 1527
9. M. E. Jung, G. Piizzi, Chem. Rev. 105 (2005) 1735
10. P. Allway, R. Grigg, Tetrahedron Lett. 32 (1991) 5817, and references cited therein
11. a) G. Popa, C. Luca, V. Magearu, J. Chim. Phys. 62 (1965) 449; b) J. E. House, Ill. State
Acad. Sci. 60 (1967) 312; c) R. J. Lancashire in Comprehensive Coordination Chemistry,
Vol. 5, G. Wilkinson, Ed., Pergamon Press, Oxford, 1987, p. 775
12. R. E. Yingst, B. E. Douglas, Inorg. Chem. 3 (1964) 1177
13. R. D. Hanckok, J. Chem. Soc. Dalton Trans. (1980) 416
14. a) D. A. Barr, R. Grigg, N. H. Q. Gunaratne, J. Kemp, P. McMeekin, V. Sridharan, Tetra-
hedron 44 (1988) 557; b) K. Amornraksa, D. Barr, G. Donegan, R. Grigg, P. Ratananu-
kul, V. Sridharan, Tetrahedron 45 (1989) 4649; c) R. Grigg, D. M. Cooper, S. Holloway,
S. McDonald, E. Millington, M. A. B. Sarker, Tetrahedron 61 (2005) 8677.
Available online at www.shd.org.rs/JSCS/
___________________________________________________________________________________________________________________________
2009 Copyright (CC) SCS

Copyright of Journal of the Serbian Chemical Society is the property of National Library of Serbia and its
content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's
express written permission. However, users may print, download, or email articles for individual use.