Novel asymmetric and stereospecific aziridination of alkenes with a chiral nitridomanganese complex

Full text of DOI:10.1002/(SICI)1521-3773(19981231)37:24<3392::AID-ANIE3392>3.0.CO;2-G

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reaction of a chiral MnIII complex[8] with gaseous NH3 and
Chloramine-T as the oxidant in MeOH.[9]
Novel Asymmetric and Stereospecific
Aziridination of Alkenes with a Chiral
Nitridomanganese Complex**
Although trifluoroacetic anhydride (TFAA) was used by
Groves as well as Carreira for the activation of their nitrido
complexes, when we employed this reagent in the aziridina-
tion of unfunctionalized alkenes with the chiral nitridomanga-
nese complex 1 no aziridine derivatives were obtained.[10] As a
result we searched for another activating reagent and found p-
toluenesulfonic anhydride (Ts2O) to be effective for the
aziridination of alkenes (Table 1). The reaction of the nitrido
complex 1 with styrene (10 equiv) in methylene chloride at
room temperature for 3 h in the presence of Ts2O (1.2 equiv)
and pyridine (1.5 equiv) gave the corresponding N-tosylazir-
idine in 49% yield based on 1. The yield of aziridine increased
up to 63% with a decrease in the amount of pyridine and with
the enantiomeric excess (ee) of the product being 31%. The
aziridination proceeded smoothly at 08C and retained both
Satoshi Minakata, Takeya Ando, Masaaki Nishimura,
Ilhyong Ryu, and Mitsuo Komatsu*
Optically active aziridines are useful building blocks for
nitrogen-containing functional compounds.[1] They are also
found in some natural and biologically active products such as
mitomycins and azinomycins.[1, 2] Among the various routes
that have been developed thus far to give chiral aziridines,[3]
reagent-controlled asymmetric aziridinations of carbon ±
carbon double bonds are remarkable in terms of their
simplicity and convenience as a synthetic procedure.[4] The
chiral CuI or MnIII complexes discovered by Evans,[4a,b]
Jacobsen,[4c±e] and Katsuki[4f,g] represent efficient catalysts for
such reactions when [N-(p-toluenesulfonyl)imino]phenyliodi-
ˆ
nane, PhI NTs, is used as a nitrogen source. On the other
hand, it is noteworthy that an approach for direct aziridination
with nitrido(5,10,15,20-tetramesitylporphyrinato)manganese
(TMPMnN) has been reported by Groves and Takahashi,
but their study was restricted to the use of cis-cyclooctene as
the alkene.[5] Recently this type of reaction was extended by
Carreira and co-workers to the amination of silyl enol ethers
and glycols with new types of nitridomanganese complexes.[6]
An asymmetric version of this methodology, however, has not
yet been achieved. This situation prompted us to investigate a
novel chiral nitrido complex that would impart enantioselec-
tive aziridination. We report herein the first asymmetric and
stereospecific aziridination of styrene derivatives by transfer
of a nitrogen atom from a chiral nitridomanganese complex,
wherein the additives play a key role in the performance of
the reaction and its selectivity.
Table 1. Asymmetric aziridination of styrene derivatives with the nitrido
complex 1[a]
Ts
N
1
R1
R2
pyridine, Ts2O, pyridine N-oxide
R1
R2
CH2Cl2, 3 h
Ph
Ph
Substrate
Additive
T
[8C]
Yield
[%]
ee
[%]
R1
R2
H
H
Me
Me
H
H
nPr
iPr
H
H
H
H
Me
Me
H
±
RT
0
RT
0
RT
RT
0
63
78
60
72
14
34
66
53[g]
31[b,c]
41[b,c]
73[d,e]
85[d,e]
30[d,f]
25[d,f]
90[b,f]
94[b,f]
pyridine N-oxide
±
pyridine N-oxide
±
pyridine N-oxide
pyridine N-oxide
pyridine N-oxide
H
0
The chiral nitridomanganese complexes 1 and 2 were
readily prepared from literature procedures,[7] including
[a] Reaction conditions: 1 (1 equiv), pyridine (0.5 equiv), Ts2O (1.2 equiv),
additive (1.2 equiv), alkene (10 equiv), 3 h, CH2Cl2. [b] The enantiomeric
excess was determined by HPLC analysis on a Daicel Chiralcel OJ column.
[c] The absolute configuration was determined as R by comparison of the
measured optical rotations with the reported values.[4b] [d] The enantio-
meric excess was determined by 1H NMR analysis with [Eu(hfc)3]. [e] The
absolute configuration was determined as (2R,3R) by comparison of the
measured optical rotations with the reported values.[4b] [f] The absolute
configuration was not determined. [g] The reaction was run for 5 h.
H
H
H
H
N
N
N
N
N
N
Mn
Mn
tBu
O
O
tBu
O
O
tBu
tBu
the yield and enantioselectivity. In order to obtain better
enantioselectivity, we examined the reaction in the presence
of pyridine N-oxide.[11] The addition of pyridine N-oxide at
08C gave the best result (78%, 41% ee). The aziridination
proceeded even at 208C with 40% ee. Thus, the use of
pyridine N-oxide improved not only the enantioselectivity but
also the yield of the product. These results represent the first
example of the aziridination of styrene and, in addition, the
first asymmetric synthesis with a chiral nitridomanganese
complex. When complex 2, which bears Jacobsenꢁs ligand, was
tested under the best conditions the yield was very low (9%)
but the enantioselectivity of the aziridine was moderate
(50%).
1
2
Carreiraꢁs method,[6a] by the treatment of chiral ligands with
Mn(OAc)2, NH4OH, and NaOCl. An alternative procedure
for the preparation of 1 was developed by us and consists of a
[*] Prof. Dr. M. Komatsu, Dr. S. Minakata, T. Ando, M. Nishimura,
Dr. I. Ryu
Department of Applied Chemistry
Faculty of Engineering, Osaka University
Suita, Osaka 565-0871 (Japan)
Fax: (‡81)6-6879-7402
E-mail: komatsu@ap.chem.eng.osaka-u.ac.jp
[**] T. A. acknowledges the Ministry of Education, Science, Sports and
Culture of Japan for a Grant-in-Aid for JSPS Research Fellowships
for Young Scientists. We are grateful to Professor Dr. Erick M.
Carreira for helpful discussions.
The pronounced effect of pyridine N-oxide was also
observed in the aziridination of trans-b-methylstyrene. Al-
though trans-b-methylstyrene was not aziridinated below
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room temperature in the absence of pyridine N-oxide, the
addition of the N-oxide to the reaction system resulted in a
good yield and enantioselectivity (72%, 85% ee) even at 08C.
In comparison, the aziridination of cis-b-methylstyrene was
not observed at 08C in spite of the presence of pyridine N-
oxide. In the absence of the N-oxide the desired cis aziridine
was obtained in a poor yield and with a low ee value at room
temperature. The addition of pyridine N-oxide improved the
yield of aziridine, but a remarkable change in the ee value was
not observed. The fact that the use of trans-b-methylstyrene
resulted in high enantioselectivity encouraged us to inves-
tigate the asymmetric aziridination of other trans-disubstitut-
ed alkenes. The reaction of trans-1-phenyl-1-pentene with 1
under optimal conditions afforded the desired product in
good yield (66%) and with high enantioselectivity (90% ee).
Even better results were obtained when trans-3-methyl-1-
phenyl-1-butene was utilized as the substrate. However,
aziridination was not observed when a more bulky alkene,
namely trans styrene with a tert-butyl substituent in the b
position, was employed in the reaction. It is noteworthy
that high stereospecificity was observed in all the aziridina-
tions of trans- and cis-1,2-disubstituted alkenes, although
Experimental Section
General conditions for aziridination reactions: Pyridine (0.25 mmol),
alkene (5.0 mmol), and solution of p-toluenesulfonic anhydride
a
(0.6 mmol) in CH2Cl2 (3 mL) were added to a solution of 1 (0.5 mmol)
and pyridine N-oxide (0.6 mmol) in CH2Cl2 (2 mL) under nitrogen, and the
mixture was stirred for 3 h. Pentane (15 mL), silica gel (400 mg), and celite
(400 mg) were added and the mixture was stirred for 0.5 h. The reaction
mixture was then passed through a 3-cm plug of silica gel with diethyl ether
(5 Â 15 mL) as eluent. The filtrate was concentrated in vacuo, and the
residue purified by flash column chromatography on silica gel (EtOAc/
hexane). Enantiomeric excesses of the aziridines were determined by chiral
1
HPLC analysis (Daicel Chiralcel OJ) or by using the H NMR chiral shift
reagent [Eu(hfc)3].
Received: July 10, 1998 [Z12126IE]
German version: Angew. Chem. 1998, 110, 3596 ± 3598
Keywords: asymmetric synthesis ´ aziridinations ´ manganese
´ nitrides ´ N ligands
[1] a) J. A. Deyrup in The Chemistry of Heterocyclic Compounds, Vol. 42
(Ed.: A. Hassner), Wiley, New York, 1983, pp. 1 ± 214; b) A. Padwa,
A. D. Woolhouse in Comprehensive Heterocyclic Chemistry, Vol. 7
(Ed.: W. Lwowski), Pergamon, Oxford, 1984, pp. 47 ± 93; c) W. H.
Pearson, B. W. Lian, S. C. Bergmeier in Comprehensive Heterocyclic
Chemistry II, Vol. 1A (Ed.: A. Padwa), Pergamon, Oxford, 1996,
pp. 1 ± 60; d) K. M. L. Rai, A. Hassner in Comprehensive Heterocyclic
Chemistry II, Vol. 1A (Ed.: A. Padwa), Pergamon, Oxford, 1996,
pp. 61 ± 96.
ˆ
such reactions in the presence of metal catalysts and PhI NTs
did not always show high streospecificity.[4] In addition, the
allylic amination product was not produced in all the
reactions.
The present reaction was applied with the aim of using the
silyl enol ether to direct the asymmetric amination. The
amination, which is presumed to take place via an aziridine
intermediate,[6d, 12] proceeded smoothly to give the N-tosyl-
ated a-aminoketone in 76% yield and 48% ee (Scheme 1).
When 1 was tested under Carreiraꢁs conditions[6a] the N-
trifluoroacetylated a-aminoketone was obtained in moderate
yield and ee (58%, 79% ee).[13] These results are of signifi-
cance in that they suggest that additives such as Ts2O and
TFAA, which are used for the generation of the imido
complex,[5a] might control the aziridination with 1.
[2] M. Kasai, M. Kono, Synlett 1992, 778 ± 790.
[3] a) D. Tanner, Angew. Chem. 1994, 106, 625 ± 646; Angew. Chem. Int.
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V. K. Aggarwal, Chem. Rev. 1997, 97, 2341 ± 2372.
[4] a) D. A. Evans, K. A. Woerpel, M. M. Hinman, M. M. Faul, J. Am.
Chem. Soc. 1991, 113, 726 ± 728; b) D. A. Evans, M. M. Faul, M. T.
Bilodeau, B. A. Anderson, D. M. Barnes, J. Am. Chem. Soc. 1993, 115,
5328 ± 5329; c) Z. Li, K. R. Conser, E. N. Jacobsen, J. Am. Chem. Soc.
1993, 115, 5326 ± 5327; d) W. Zhang, N. H. Lee, E. N. Jacobsen, J. Am.
Chem. Soc. 1994, 116, 425 ± 426; e) Z. Li, R. W. Quan, E. N. Jacobsen,
J. Am. Chem. Soc. 1995, 117, 5889 ± 5890; f) K. Noda, N. Hosoya, R.
Irie, Y. Ito, T. Katsuki, Synlett 1993, 469 ± 471; g) H. Nishikori, T.
Katsuki, Tetrahedron Lett. 1996, 37, 9245 ± 9248; h) R. E. Lowenthal, S.
Masamune, Tetrahedron Lett. 1991, 32, 7373 ± 7376; i) D. Tanner, P. G.
Andersson, A. Harden, P. Somfai, Tetrahedron Lett. 1994, 35, 4631 ±
4634; j) A. M. Harm, J. G. Knight, G. Stemp, Synlett 1996, 677 ± 678;
k) T.-S. Lai, H.-L. Kwong, C.-M. Che, S.-M. Peng, Chem. Commun.
1997, 2373 ± 2374; l) M. J. Södergren, D. A. Alonso, P. G. Andersson,
Tetrahedron: Asymmetry 1997, 8, 3563 ± 3565; m) P. Müller, C. Baud,
Y. Jacquier, M. Moran, I. Nägeri, J. Phys. Org. Chem. 1996, 9, 341 ±
347; n) R. S. Atkinson, W. T. Gattrell, A. P. Ayscough, T. M. Rayn-
ham, Chem. Commun., 1996, 1935 ± 1936.
TMSO
O
NHZ
*
a
Z = Ts
76%, 48% ee
58%, 79% ee
CF CO
Z =
3
Scheme 1. [a] Z ˆ Ts: 1 (1 equiv), pyridine (0.5 equiv), Ts2O (1.5 equiv),
pyridine N-oxide (1.2 equiv), silyl enol ether (10 equiv), CH2Cl2, 08C, 6 h;
Z ˆ CF3CO: 1 (2 equiv), pyridine (3 equiv), (CF3CO)2O (2.4 equiv), silyl
enol ether (1 equiv), CH2Cl2, 788C !RT, 3 h.
[5] a) J. T. Groves, T. Takahashi, J. Am. Chem. Soc. 1983, 105, 2073 ± 2074;
b) J. T. Groves, T. Takahashi, W. M. Butlar, Inorg. Chem. 1983, 22,
884 ± 887.
[6] a) J. D. Bois, J. Hong, E. M. Carreira, M. W. Day, J. Am. Chem. Soc.
1996, 118, 915 ± 916; b) J. D. Bois, C. S. Tomooka, J. Hong, E. M.
Carreira, J. Am. Chem. Soc. 1997, 119, 3179 ± 3180; c) J. D. Bois, C. S.
Tomooka, J. Hong, E. M. Carreira, M. W. Day, Angew. Chem. 1997,
109, 1722 ± 1724; Angew. Chem. Int. Ed. Engl. 1997, 36, 1645 ± 1647;
d) J. D. Bois, C. S. Tomooka, J. Hong, E. M. Carreira, Acc. Chem. Res.
1997, 30, 364 ± 372.
[7] a) J. W. Buchler, C. Dreher, K.-L. Lay, Z. Naturforsch. B 1982, 37,
1155 ± 1162; b) J. W. Buchler, C. Dreher, K.-L. Lay, Y. J. A. Lee, W. R.
Scheidt, Inorg. Chem. 1983, 22, 888 ± 891; c) C. L. Hill, F. J. Hollander,
J. Am. Chem. Soc. 1982, 104, 7318 ± 7319.
The aziridination of styrene derivatives proceeds with a
chiral nitridomanganese complex 1 to give products in good
yield and with excellent enantioselectivity. In addition, this
methodology results in stereospecific aziridination. We also
conclude that additives play an important role in the reaction;
Ts2O was the most effective reagent in the activation of 1, and
the use of pyridine N-oxide was necessary to obtain high
enantioselectivity. Efforts to extend the scope of this process
to other alkenes are currently in progress.
[8] J. F. Larrow, E. N. Jacobsen, Y. Gao, Y. Hong, X. Nie, C. M. Zepp, J.
Org. Chem. 1994, 59, 1939 ± 1942.
Angew. Chem. Int. Ed. 1998, 37, No. 24
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[9] Treatment of the MnIII complex[8] (35.6 mg, 0.09 mmol) with Chlor-
amine-T (141 mg, 0.5 mmol) in MeOH (5 mL) at room temperature
for 40 h afforded complex 1 in 84% yield.
[10] The use of trifluoromethanesulfonic anhydride or p-toluenesulfonyl
chloride as an activator did not give good results relative to p-
toluenesulfonic anhydride.
[11] Katsuki and his co-workers have reported that pyridine N-oxide is an
effective additive for the asymmetric epoxidation catalyzed by salen ±
manganese(iii) complexes, and they applied these findings to the
ization of two core-modified sapphyrins synthesized by an
unprecedented coupling of a modified tripyrrane. Sapphyrins
have been shown to self-assemble in the solid state to form a
supramolecular ladder held together by weak C H ´´´ S or
C H ´´´ Se and C H ´´´ N hydrogen-bonding interactions.
Literature methods for the synthesis of sapphyrins include a
traditional [3‡2] acid-catalyzed MacDonald-type condensa-
tion between the appropriate precursors, reaction of difor-
mylbipyrrole with benzaldehyde and pyrrole under Lindsey
conditions,[4] and an acid-catalyzed condensation of a,c-
biladienes with pyrrole-2-carbaldehydes.[5] Recently, a meso-
substituted sapphyrin was isolated as a side product in 1%
yield in the Rothemund reaction of benzaldehyde and
pyrrole.[6] In all these reactions at least two precursors are
required for the condensation under different conditions.
However, our reaction of the modified tripyrranes 1 and 2 in
dichloromethane containing an appropriate acid catalyst gave
18p, 22p, and 26p macrocycles in moderate yields (Scheme 1).
The product distribution and the yields of isolated products
were dependent on the nature of the acid catalyst and its
ˆ
asymmetric aziridination of alkenes with PhI NTs: R. Irie, Y. Ito, T.
Katsuki, Synlett 1991, 265 ± 266.
[12] a) D. A. Evans, M. M. Faul, M. T. Bilodeau, J. Am. Chem. Soc. 1994,
116, 2742 ± 2753; b) A. Cipollone, M. A. Loreto, L. Pellacani, P. A.
Tardella, J. Org. Chem. 1987, 52, 2584 ± 2586; c) S. Lociuro, L.
Pellacani, P. A. Tardella, Tetrahedron Lett. 1983, 24, 593 ± 596.
[13] The chiral product could be purified to greater than 98% ee by
recrystallization from benzene/hexane.
Sapphyrin Supramolecules through C H ´´´ S
and C H ´´´ Se Hydrogen BondsÐFirst
Structural Characterization of meso-
Arylsapphyrins Bearing Heteroatoms**
Seenichamy Jeyaprakash Narayanan, Bashyam
Sridevi, Tavarekere K. Chandrashekar,* Ashwani Vij,*
and Raja Roy
Dedicated to Professors C. N. R. Rao and Jeanꢀne M. Shreeve
on the occasion of their 65th birthdays
Controlling the assembly of macromolecules in the solid
state through weak interactions such as hydrogen bonding and
van der Waals forces is currently being explored for the
synthesis of functional materials for molecular recognition
and catalysis.[1] Many supramolecules held together by weak
C H ´´´ O and C H ´´´ N hydrogen bonds are known.[2] In
contrast, molecules held together by C H ´´´ S and C H ´´´ Se
hydrogen bonds are very rare, and to the best of our
knowledge there are only three reports to date on such
interactions.[3] Here we describe the first structural character-
Scheme 1. Synthesis of various sapphyrins and rubyrins from 1 and 2.
concentration. For S- and Se-containing tripyrranes at lower
concentrations of trifluoroacetic acid (TFA), the major
product was rubyrin, while at higher concentrations of TFA,
sapphyrin and rubyrin were isolated in moderately good
yields in addition to small amounts of X2TPP (X ˆ S or Se;
TPP ˆ tetraphenylporphyrin). The formation of 5 and 6
requires partial acidolysis of tripyrranes under the reaction
conditions. We have observed that both 1 and 2 undergo
acidolysis, and the extent of acidolysis is dependent on the
TFA concentration. The higher yields of 5 and 6 at higher
concentrations of TFA is consistent with this observation. For
the formation of 7 and 8 we suggest an acid-catalyzed self-
condensation of two tripyrrane units through an oxidative
coupling,[7] forming a rubyrinogen intermediate which on
dehydrogenation gives rubyrin.[8] Attempts to isolate the
corresponding rubyrinogen proved futile because it oxidizes
readily to the corresponding aromatic congener. The sole
formation of rubyrins at the lower concentrations of TFA
(0.1 equiv) at which acidolysis is minimal suggests that the
self-coupling is preferred at this concentration.
[*] Prof. Dr. T. K. Chandrashekar, S. J. Narayanan, B. Sridevi
Department of Chemistry, Indian Institute of Technology
Kanpur 208016 (India)
Fax: (‡91)512-590-007/597-436
E-mail: tkc@iitk.ac.in
Dr. A. Vij
Single-Crystal Diffraction Laboratory
University of Idaho, Moscow, ID 83834 (USA)
E-mail: Vij@uidaho.edu
Dr. R. Roy
NMR Division, Central Drug Research Institute
Lucknow (India)
[**] This work was supported by the Department of Science and
Technology (DST; grant to T.K.C.) and by the Council of Scientific
and Industrial Research (CSIR), Government of India, New Delhi
(Senior Research Fellowship to S.J.N.). The single-crystal X-ray
facility at the University of Idaho was established with the assistance
of the NSF-Idaho EPSCoR program (NSF OSR-9350539) and the
M. J. Murdock Charitable Trust, Vancouver, WA.
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Angew. Chem. Int. Ed. 1998, 37, No. 24