A catalytic and enantioselective synthesis of trans-2-amino-1-aryltetralins

Article abstract of DOI:10.1002/adsc.200800603

The bis-oxazoline-copper complex-catalyzed aziridination of alkenes followed by an intramolecular Friedel-Crafts alkylation of the tethered and in situ generated aziridine provides a one-pot, general and efficient method for the synthesis of trans-2-amino

Full text of DOI:10.1002/adsc.200800603

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DOI: 10.1002/adsc.200800603
A Catalytic and Enantioselective Synthesis of trans-2-Amino-1-
aryltetralins
Saumen Hajra,a,* Biswajit Maji,a and Dipakranjan Mala
a
Department of Chemistry, Indian Institute of Technology, Kharagpur 721 302, India
Fax : (+91)-3222-255303; e-mail: shajra@chem.iitkgp.ernet.in
Received: October 1, 2008; Revised: March 6, 2009; Published online: April 6, 2009
Supporting information for this article is available on the WWW under
http://dx.doi.org/10.1002/adsc.200800603.
Abstract: The bis-oxazoline-copper complex-cata-
lyzed aziridination of alkenes followed by an intra-
molecular Friedel–Crafts alkylation of the tethered
and in situ generated aziridine provides a one-pot,
general and efficient method for the synthesis of
trans-2-amino-1-aryltetralins from a mixture of 2-
arylethylstyrenes (E/Zꢀ85:15) with excellent dia-
stereo- (dr>99:1) and enantioselectivities (up to
92% ee).
Scheme 1. Retrosynthesis for the construction of hexahydro-
phenanthrene 1.
Keywords: 2-amino-1-aryltetralins; aziridination;
catalytic synthesis; enantioselectivity; Friedel–
Crafts alkylation
CuACTHNUTRGNEUNG
(OTf)2 is known to effect the aziridination[5] of
alkenes and is useful for the subsequent intramolecu-
lar Friedel–Crafts alkylation of the tethered and in
situ generated aziridines.[7] It was anticipated that the
use of a chiral catalyst of copper(II) salts might pro-
vide the non-racemic trans-2-amino-1-aryltetralins.
Hexahydrobenzophenanthrenes 1 (n=1) and their Consequently, we chose to investigate the well estab-
homologues 1 (n=2) constitute important structural lished bis-oxazoline-copper complexes, which were re-
subunits of various natural products and pharmaceuti- ported for the asymmetric aziridination of E-alkenes
cals.[1,2] There has been considerable interest in the with PhINSO2Ar.[8,9] Thus, our studies began with the
synthesis of such compounds, especially in an enantio- reaction of 4a with PhINSO2(4-NO2-C6H4) [PhINNs]
selective manner.[3] Enantioselective 1,4-conjugate ad- in the presence of Cu
ACTHNUTRGNEN(UG OTf)2 and bis-oxazoline ligands
dition of aryllithium reagents to nitroalkenes followed 5a–e (Table 1). The reaction of 4a (5.0 equiv.) with
by reduction of the nitro group and cylization is an es- PhINNs (1.0 equiv.) was carried out in the presence of
tablished protocol for the synthesis of such com- CuACTHNUGTRENUNG(OTf)2 (0.1 equiv.) and bis-oxazoline ligand 5a
pounds.[4] We, however, envisaged the asymmetric (0.12 equiv.) in CH2Cl2 at room temperature. After
synthesis of phenanthrenes 1 from trans-2-amino-1-ar- 2 h, it produced aziridine 3a as the sole product and
yltetralins 2 via stereoselective intramolecular aryla- the expected cyclized product 2a was not formed.
tion of tethered chiral aziridines 3 (Scheme 1). While When the same reaction was performed with an addi-
the study on regio- and stereoselective ring-opening tional amount of CuACTHUNRGTNEUNG(OTf)2 (0.05 equiv.) it produced,
of aziridines is well documented,[5,6] the intramolecu- after 20 min, the desired product 2a with 42% ee in
lar Friedel–Crafts alkylation with chiral non-racemic 56% of yield (entry 1). Under similar reaction condi-
tethered aziridines has not been reported to date.
tions, the other bis-oxazoline-CuACTHNGUTERNNU(G OTf)2 catalysts 5b–e
Herein, we report our results on the intramolecular were investigated. With the sterically demanding tert-
arylation of in situ generated aziridines towards a cat- butyl bis-oxazoline 5b, there was no appreciable im-
alytic, enantioselective and one-pot synthesis of trans- provement in the yield and ee (entry 2). Improved
2-amino-1-aryltetralins 2 with high diastereo- (>99:1) enantioselectivity was observed with the benzyl-sub-
and enantioselectivity (up to 92% ee).
stituted bis-oxazoline 5c (entry 3). Similar selectivity
was also obtained with bis-oxazoline 5e, derived from
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Table 1. Screening of bis-oxazoline ligands for the
CuACHTUNGTRENNUNG(OTf)2-catalyzed aziridination-Friedel–Crafts reaction.
indanolamine (entry 5). Among all the bis-oxazoline-
Cu salts, 5d was found to be the best (ee 92% and
yield 85%; entry 4). The effect of a solvent on this re-
action was substantial. Both yield and ee were better
in CH2Cl2 (yield 85% and ee 92%) than in benzene
(yield 62% and ee 68%), toluene (yield 61% and ee
65%) and acetonitrile (yield 81% and ee 43%) for the
transformation 4a!2a in the presence of 5d.
It is worth mentioning that the copper salt must be
added in two portions, at first 0.10 equivalent together
with the ligand (0.12 equivalent) to obtain the aziri-
dine and then 0.05 equivalent to achieve the Friedel–
Crafts cyclization. Prolonging the reaction by 24 h
without additional copper salt led to decomposition
of the aziridine with the formation of a mixture of
products. It seems that the ligand-complexed copper
salt is not effective for the Friedel–Crafts reaction.
Excess Cu salt, added as the second portion, remains
free from complexation and hence causes the Friedel–
Crafts reaction. When 4a was reacted with 0.15 equiv-
Entry
Ligand 5
Yield of 2a [%][a]
ee[b] [%]
1
2
3
4
5
(S)-5a
(S)-5b
(S)-5c
(R)-5d
56
61
72
85
66
42
45
alent of CuACTHUNRGTNEUNG(OTf)2 in one portion along with 0.12
equivalent of ligand 5d, the yield of 2a was 82%, but
the ee dropped to 68% from 92%. This might be due
to competitive racemic aziridination in the presence
of the uncomplexed copper salt.
Having found 5d to be the most effective, we next
investigated the scope of the catalytic asymmetric syn-
62
92[c]
69[c]
ACHTUNGTRENNUNG(1R,2S)-5e
[a]
Isolated yield after column chromatography.
Enantiomeric excess was determined by chiral HPLC.
The other enantiomer was predominantly formed.
[b]
[c]
thesis of N-protected-2-amino-1-aryltetralins
2
(Table 2). Substrates 4b and 4c smoothly underwent
Table 2. Bis-oxazoline 5d-CuACHTNUGRTNEUNG
(OTf)2 complex-catalyzed one-pot enantioselective synthesis of trans-2-amino-1-aryltetralins 2.[a]
Entry Substrate (E:Z) R1
R2
R3
R4
Time [h][b] Yield of 2 [%][c] dr of 2 (trans:cis) ee of 2 [%][d]
1
2
3
4
5
6
7
8
9
10
4a (75:25)
4b (74:26)
4c (63:37)
4d (75:25)
4e (67:33)
4f (85:15)
4g (77:23)
4h (76:24)
4i (73:27)
4j (68:32)
H
H
H
H
H
H
H
H
H
H
OMe
H
Me
H
H
H
H
H
H
1.0
3
1.5
1.0
1.5
1.0
85 (2a)
62 (2b)
77 (2c)
81 (2d)
66 (2e)
78 (2f)
76 (2g)
71 (2h)
79 (2i)
58 (2j)
>99:1
>99:1
>99:1
>99:1
>99:1
>99:1
>99:1
>99:1
>99:1
>99:1
92
59
86
76
82
74
83
60
73
66
OMe Me
OMe Cl
OMe OMe
OMe
H
OMe 1.0
1.5
OMe 2.5
Br 2.5
OMe OMe Me
H
H
H
H
H
H
H
[a]
A suspension of substrate 4 (5 equiv.), PhINNs (1.0 equiv.) and bis-oxazoline-Cu(II) complex derived from 10 mole%
Cu(OTf)2 and 12 mole% bis-oxazoline ligand 5d in CH2Cl2 was stirred at 258C. After dissolution of all the nitrenoid re-
agents, additional 5 mole% Cu(OTf)2 was added.
Total time including aziridine formation and subsequent cyclization.
Isolated yield after flash column chromatography.
ACHTUNGTRENNUNG
AHCTUNGTRENNUNG
[b]
[c]
[d]
Enantiomeric excess was determined by HPLC using Chiralcel AD-H and OD-H columns.
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A Catalytic and Enantioselective Synthesis of trans-2-Amino-1-aryltetralins
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Table 3. Two-step enantioselective synthesis of N-protected 2-amino-1-aryltetralins 2.[a]
Entry Substrate (E:Z)
Step 1 [h] Yield of dr of 3[c] (trans:cis) ee of
[b] [%] [d] [%]
Step 2 [h] Yield of dr of 2[c]
ee of
2
[d] [%]
3
3
2
[b] [%]
(trans:cis)
1
2
3
4
5
6
7
8
9
4a (75:25)
4b (74:26)
4c (63:37)
4i (73:27)
trans-4a (>99:1) 0.5
cis-4a (<1:99)
trans-4b (>99:1) 2.5
0.5
2.5
1
83
63
80
80
86
29
65
40
–
1:2.5
ND[e]
62
86
0.5
1.5
1.0
1.5
0.5
0.5
1.5
2
98
98
97
97
97
95
98
>99:1
>99:1
>99:1
>99:1
>99:1
>99:1
>99:1
90
61
87
69
90
77
61
68
–
>99:1
>99:1
50:1
2
69
1:2.5
ND[e]
80
8
<1:99
>99:1
1:1
62
cis-4b (<1:99)
–
18
–
ND[e]
35
98 (97)[f] >99:1
NR
<1:99
12
–
[a]
Step 1: A suspenstion of substrate 4 (5 equiv.), PhINNs (1.0 equiv.) and bis-oxazoline-Cu(II) complex derived from 10
mole% Cu(OTf)2 and 12 mole% bis-oxazoline ligand 5d in CH2Cl2 was stirred at 258C. Step 2: Isolated aziridine 3 in
CH2Cl2 was treated with 0.05 equiv of Cu(OTf)2 at room temperature.
ACHTUNGTRENNUNG
AHCTUNGTRENNUNG
[b]
[c]
[d]
[e]
Isolated yield after flash column chromatography.
1
Diastereomeric ratio was measured from the H NMR analysis of the crude reaction mixture.
Enantiomeric excess was determined by HPLC using chiralcel AD-H and OD-H column.
The ee could not be determined as the peaks of one trans-enantiomer and one of the cis-enantiomers could not be re-
solved under a variety of HPLC conditions.
Yield of the respective 2b based on 100% conversion of aziridine 3b. Yield in parenthesis refers to the recovered cis-aziri-
dine cis-3b. ND=not determined; NR=no reaction.
[f]
the reaction and afforded products 2b and 2c with 30 min in 83% of yield. Aziridination of pure trans-4a
59% and 86% ee, respectively (entries 2 and 3). Styr- also afforded a 1:2.5 mixture of trans- and cis-3a in
enes 4d–h having electron-donor substituents on both 86% yield within 30 min (entry 5), whereas pure cis-
the aromatic rings at either end of the alkene chain 4a gave>99:1 of cis-3a after 8 h in 29% yield with
underwent fast reactions and gave 2d–h with good 80% ee (entry 6). Similarly, aziridination of pure
yields and selectivities (entries 4–8). Substrates 4i and trans-4b provided >99:1 trans-3b after 2.5 h in 65%
4j containing meta-methoxy- and bromo-substituents yield with 62% ee (entry 7), whereas pure cis-4b gave
provided good yields with 73% and 66% ee, respec- a 1:1 mixture of trans- and cis-3b after 18 h in 40%
tively (entries 9 and 10).
yield.[10] It was found that trans-alkenes underwent
It is likely that the enantioselectivity is controlled fast aziridination (0.5–2.5 h) with good yield whereas
in the first step, i.e., aziridination step, and carried the aziridinations of cis-alkenes were slow (8–18 h)
over to the subsequent Friedel–Crafts cyclization to and low yielding (entries 6 and 8).
yield non-racemic 2-amino-1-aryltetralins 2. To sup-
All trans-aziridines 3b, 3c, 3i and mixture of
port this view, the syntheses of tetralins 2a–c and 2i cis/trans-3a underwent smooth intramolecular Frie-
were conducted in two steps from electronically dif- del–Crafts cyclization in the presence of a catalytic
ferent styrenes 4a–c and 4i (Table 3). It was found amount of CuACTHNUTRGENUG(N OTf)2 and afforded exclusively trans-2-
that the ees of the 2-amino-1-aryltetralins 2 were com- amino-1-aryltetralins 2 in excellent yields with ees
parable with the ees of isolated aziridines 3, and also comparable with those of aziridines 3. The isomeric
the overall yields of the two steps were very close to cyclized product cis-2a was not detected in the
the yields of the one-pot version.
1H NMR or HPLC analysis (entry 1). The cis-aziri-
Aziridination of 4b and 4c (E/Z=74/26 and 63/37, dine cis-3a (ee 80%) with a para-methoxyphenyl sub-
respectively) provided >99:1 selectivity towards stituent also underwent smooth cyclization within half
trans-aziridines 3b and 3c (entries 2 and 3) and 4i an hour under similar conditions and provided exclu-
(E/Z=73/27) showed trans-selectivity of 50:1 sively trans-4a in 95% of yield and 77% of ee
(entry 4), whereas 4a (E/Z=75/25) provided a 1:2.5 (entry 6). The Cu
ACHTUNGRTEN(NUNG OTf)2-catalyzed Friedel–Crafts re-
mixture of trans- and cis-aziridine 3a (entry 1) within action of cis/trans-3b provided trans-2-amino-1-aryl-
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Saumen Hajra et al.
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Alternatively, the carbocation B might undergo fur-
ther ring closure to generate the aziridine trans-3,
which subsequently undergoes an SN2 type intramo-
lecular Friedel–Crafts reaction to afford the trans-2-
amino-1-aryltetralin 2 (Scheme 3).
Chiral trans-2-amino-1-aryltetralins 2 are the ad-
vanced precursors for the synthesis of dopamine D1
agonists such as dihydrexiridine, A-86929 and sch
39166.[4] Consequently, the developed methodology
was tested on the synthesis of dihydrexiridine[2a]
(Scheme 4). To this end, styrene 4k (E/Z=78/22) was
Scheme 2. Plausible mechanism for the Friedel–Crafts cycli-
zation of trans-aziridines.
reacted with PhINNs in the presence of CuACTHNURGTNEUNG(OTf)2-5d
as catalyst. It provided exclusively trans-N-protected-
2-amino-1-phenyltetralin 2k in 85% yield with 70%
ACHTUNGTRENNUNGtetralin 2b in 98% of yield (based on 100% conver- ee. One recrystalization of the column-purified prod-
sion) after 1 h along with complete recovery of cis-3b uct from methanol at 58C afforded optically pure 2k
(entry 8). Under similar conditions, pure cis-3b was (97% ee) with 70% recovery yield. Deprotection of
separately reacted in the presence of the Cu catalyst the N-nosyl group of 2k on treatment with 4-meth-
and also in the presence of a stoichiometric amount
ACHTUNGRTNEoUNNG xythiophenol and K2CO3 in CH3CN/DMSO (49:1) at
of Cu(OTf)2. Up to 24 h, there was no sign of reaction room temperature produced trans-2-amino-1-phenyl-
ACHTUNGTRENNUNG
at room temperature (entry 9). It produced an intract- tetralin 6 in 88% yield within 2.5 h.[13] The optical ro-
able mixture when heated at 408C for 30 min. These tation of 6 {[a]2D5: ꢁ19.9 (c 1.3, CHCl3)} was compara-
results can be interpreted in terms of differential reac- ble with literature[4b] data {[a]25: ꢁ20.6 (c 1.3, CHCl3)}
tivities of the isomeric aziridines. The trans-aziridines thus confirming the absolute sDtereochemistry as 1S,2S.
undergo an SN2 type Friedel–Crafts cyclization to By analogy, the absolute stereochemistry of all com-
yield trans-tetralins 2 (Scheme 2),[11] whereas cis-aziri- pounds 2 was assumed. The Pictet–Spengler cycliza-
dines are not reactive to SN2 ring-opening and under- tion of 7 followed by demethylation to afford (ꢁ)-di-
go an SN1 ring-opening mechanism followed by intra- hydrexiridine 8 has already been reported.[4c]
molecular Friedel–Crafts reaction to give the more
In summary, we have developed an efficient bis-ox-
stable trans-product only for aziridines having elec- azoline-Cu-catalyzed one-pot protocol for the asym-
tron-rich aryl substituents such as 3a (Scheme 3).[12] metric synthesis of trans-2-amino-1-aryltetralins with
Scheme 3. Plausible mechanism for the Friedel–Crafts cyclization of cis-aziridines.
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A Catalytic and Enantioselective Synthesis of trans-2-Amino-1-aryltetralins
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Scheme 4. Asymmetric synthesis of (ꢁ)-dihydrexiridine.
13C NMR (CDCl3, 100 MHz): d=158.6, 149.5, 145.8, 136.7,
135.3, 134.5, 130.3, 129.8 (2C), 128.5, 127.9 (2C), 126.2,
125.9, 123.9 (2C), 113.8 (2C), 57.7, 55.0, 51.3, 29.4, 22.6;
HPLC analysis [Chiralcel AD-H, 10% i-PrOH/n-hexane,
1.0 mLminꢁ1, 220 nm, tr (major) 12.93 min, tr (minor)
15.84 min]; 92% ee; [a]29: ꢁ46.47 (c 1.00, CHCl3); HR-MS
(EI): m/z=461.1147, calDcd. for C23H22N2O5S: 461.1147 [M+
Na]+.
high diastereo- (>99:1) and enantioselectivity (up to
92%) from a mixture E/Z-2-arylethylstyrenes via in-
tramolecular Friedel–Crafts alkylation of in situ gen-
erated aziridines. An application of the present meth-
odology in a formal synthesis of (ꢁ)-dihydrexiridine 8
has been described.
Experimental Section
General Procedure for One-Pot Enantioselective
Synthesis of N-Protected-2-amino-1-aryltetralins (2a)
Acknowledgements
We thank DST, New Delhi for providing financial support.
BM thanks UGC, New Delhi, for his fellowship. The authors
are thankful to the referees for constructive scientific com-
ments and suggestions.
A 10-mL two-necked, round-bottom flask was charged with
bis-oxazoline ligand 5d (0.01 g, 0.03 mmol, 0.12 equiv.) and
CuACHTUNGTRENNUNG(OTf)2 (0.009 g, 0.025 mmol, 0.1 equiv.). Anhydrous di-
chloromethane (1 mL) was injected and the resulting mix-
ture was stirred for 30 min. To this solution, PhINNs (0.1 g,
0.24 mmol, 1.0 equiv.), substrate 4a (0.29 g, 1.23 mmol,
5.0 equiv.) and 0.2 g of powdered molecular sieves (4 ꢁ) References
were added and the reaction mixture was allowed to stir at
258C under an argon atmosphere. As soon as all the nitre-
[1] a) S. Peter, I. Ruben, K. Bjorn, CNS Drug Rev. 2004,
noid reagent had dissolved in the reaction medium, an addi-
10, 230–242; b) W. J. Giardina, M. Williams, CNS Drug
tional amount of CuACHTNUTRGNE(NUG OTf)2 (0.005 g, 0.013 mmol) was added.
Rev. 2001, 7, 305–316.
On completion, the reaction was quenched by diluting the
mixture with ethyl acetate (10 mL) and filtering through a
short plug of silica gel. The silica gel was washed with addi-
tional 10 mL of ethyl acetate. The filtrate was concentrated
by rotary evaporation under reduced pressure. The crude
mass was subjected to purification by flash column chroma-
tography using EtOAc/petroleum ether (60–808C) as an
eluent, which provided aminotetralin 2a; yield: 0.09 g
(85%).
[2] a) W. K. Brewster, D. E. Nichols, R. M. Riggs, D. M.
Mottola, T. W. Lovenberg, M. H. Lewis, R. B. Mailman,
J. Med. Chem. 1990, 33, 1756–1764; b) J. R. Taylor,
M. S. Lawrence, D. E. Redmont, J. D. Elsworth, R. H.
Roth, D. E. Nochols, R. B. Mailman, Eur. J. Pharmacol.
1991, 199, 389–391; c) M. P. Seiler, A. Hagenbach, H.-
J. Wꢂthrich, R. Marksteun, J. Med. Chem. 1991, 34,
303–307; d) T. A. Knoerzer, D. E. Nichols, W. K. Brew-
ster, V. J. Watts, D. Mottola, R. B. Mailman, J. Med.
Chem. 1994, 37, 2453–2460; e) M. R. Michaelides, Y.
Hong Jr. , S. DiDomenico, K. E. Asin, D. R. Britton,
C. W. Lin, M. Williams, K. Shiosaki, J. Med. Chem.
1995, 38, 3445–3447.
N-[1-(4-Methoxyphenyl)-1,2,3,4-tetrahydronaphthalen-2-
yl]-4-nitrobenzenesulfonamide (2a): White solid; mp 120–
1
1228C; H NMR (CDCl3, 400 MHz): d=8.13 (d, J=8.8 Hz,
2H), 7.67 (d, J=8.8 Hz, 2H), 7.13 (m, 2H), 7.00 (m, 1H),
6.73 (d, J=8.4 Hz, 2H), 6.62 (d, J=7.6 Hz, 1H), 6.58 (d, J=
8.4 Hz, 2H), 4.75 (d, J=7.2 Hz, 1H), 3.77 (d, J=8.4 Hz,
1H), 3.73 (s, 3H), 3.65–3.48 (m, 1H), 3.12–2.95 (m, 1H),
2.92 (m, 1H), 2.46–2.35 (m, 1H), 1.90–1.78 (m, 1H).
[3] P. P. Ehrlich, J. W. Ralston, M. R. Michaelides, J. Org.
Chem. 1997, 62, 2782–2785.
[4] a) M. Yamashita, K.-I. Yamada, K. Tomioka, J. Am.
Chem. Soc. 2004, 126, 1954–1955; b) M. Yamashita, K.-
Adv. Synth. Catal. 2009, 351, 859 – 864
ꢀ 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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Saumen Hajra et al.
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I. Yamada, K. Tomioka, Tetrahedron 2004, 60, 4237–
4242; c) Y. Asano, M. Yamashita, K. Nagai, M. Kuriya-
ma, K.-I. Yamada, K. Tomioka, Tetrahedron Lett. 2001,
42, 8493–8495.
c) J. S. Yadav, B. V. S. Reddy, R. S. Rao, G. Veerendhar,
K. Nagaiah, Tetrahedron Lett. 2001, 42, 8067–8070.
[7] S. Hajra, B. Maji, D. Sinha, S. Bar, Tetrahedron Lett.
2008, 49, 4057–4059.
[8] For recent reviews on asymmetric aziridination, see:
a) P. Muller, C. Fruit, Chem. Rev. 2003, 103, 2905–
2919; b) H. M. I. Osborn, J. Sweeny, Tetrahedron:
Asymmetry 1997, 8, 1693–1715.
[9] D. A. Evans, M. M. Faul, M. T. Bilodeau, B. A. Ander-
son, D. M. Barnes, J. Am. Chem. Soc. 1993, 115, 5328–
5329.
[10] The formation of a mixture of cis- and trans-aziridines
from pure cis-alkenes is known in literature: P. Brandt,
M. J. Sdergren, P. G. Andesson, P.-O. Norrby J. Am.
Chem. Soc. 2000, 122, 8013–8020.
[5] a) W. H. Pearson, B. W. Lian, S. C. Bergmeier, in: Com-
prehensive Heterocyclic Chemistry II, 2nd edn., (Ed.;
A. Padwa), Pergamon, Oxford, 1996, Vol. 1A, pp 1–60;
b) K. M. Lokanatha Rai, A. Hassner, in: Comprehen-
sive Heterocyclic Chemistry II, 2nd edn., (Ed.: A.
Padwa), Pergamon, Oxford, 1996, Vol. 1A, pp 61–96;
for recent reviews, see: c) X. E. Hu, Tetrahedron 2004,
60, 2701–2743; d) W. McCoull, F. A. Davis, Synthesis
2000, 1347–1365; e) R. S. Atkinson, Tetrahedron 1999,
55, 1519–1559; f) D. Tanner, Angew. Chem. 1994, 106,
625–646; Angew. Chem. Int. Ed. Engl. 1994, 33, 599–
619.
[6] Intra- and intermolecular aziridne ring opening by p-
nucleophiles for racemic mixtures: a) S. C. Bergmeier,
S. Katz, J. Huang, H. McPherson, P. J. Donoghue, D. D.
Reed, Tetrahedron Lett. 2004, 45, 5011–5014; b) S.
Roy, M. Bera, Tetrahedron Lett. 2007, 48, 7144–7146;
[11] M. K. Ghorai, K. Das, D. Shukla J. Org. Chem. 2007,
72, 5859–5862.
[12] I. Ungureanu, P. Koltz, A. Mann Angew. Chem. 2000,
112, 4790–4792; Angew. Chem. Int. Ed. 2000, 39, 4615–
4617.
[13] R. Narayan, M. VanNieuwenhze Org. Lett. 2005, 7,
2655–2658.
864
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Adv. Synth. Catal. 2009, 351, 859 – 864