Ruthenium(II) porphyrin catalyzed imine aziridination and crystal structures of (meso-tetrakis(pentafluorophenyl)porphyrinato)ruthenium(II) complexes containing PhN=CH(p-ClPh), CPh2, and pyridine ligands

Article abstract of DOI:10.1021/om034128b

A (meso-tetrakis(pentafluorophenyl)porphyrinato)ruthenium(II) complex of PhN=CH(p-ClPh) is prepared by reacting [Ru(F₂₀-TPP)(CO)] (1) with a benzene solution of N-(p-chlorobenzylene)aniline. The crystal structure of {Ru(F₂₀-TPP)(CO)[PhN=CH(p-ClPh)]} (10) shows the coordinated imine ligand in a cis configuration. Comparison with X-ray crystallographic data for [Ru(F₂₀-TPP)(py)₂] (11) revealed the axial Ru-N bond length of the imine complex (2.203 A) to be slightly longer than that of the bis(pyridine) complex (2.108 A). Spectral and structural data revealed the Ru-N(imine) bond to have single-bond character, and the Ru=C bond in [Ru(F₂₀-TPP)(CPh₂)] (7) has a bond distance of 1.842 A, indicative of multiple-bond character. In the presence of diazo compounds, {Ru(F₂₀-TPP)(CO)[PhN=CH-(p-ClPh)]} (10) and other related complexes mediated diastereoselective imine aziridination with product yields up to 86%. The mechanism is suggested to involve activation of the imine and diazo compounds by the ruthenium(II) porphyrin catalyst followed by nucleophilic addition of the imine to the diazo ester and subsequent cyclization to give the aziridine.

Full text of DOI:10.1021/om034128b

54
Organometallics 2004, 23, 54-66
Ru th en iu m (II) P or p h yr in Ca ta lyzed Im in e Azir id in a tion
a n d Cr ysta l Str u ctu r es of
(m eso-Tetr a k is(p en ta flu or op h en yl)p or p h yr in a to)r u th en iu m (II)
Com p lexes Con ta in in g P h NdCH(p-ClP h ), CP h 2, a n d
P yr id in e Liga n d s
Yan Li,† Philip Wai Hong Chan,† Nian-Yong Zhu,† Chi-Ming Che,*,† and Hoi-Lun
Kwong‡
Department of Chemistry and Open Laboratory of Chemical Biology of the Institute of
Molecular Technology for Drug Discovery and Synthesis, The University of Hong Kong,
Pokfulam Road, Hong Kong, People’s Republic of China, and Department of Biology and
Chemistry and Open Laboratory of Chirotechnology of the Institute of Molecular Technology
for Drug Discovery and Synthesis, City University of Hong Kong, Tat Chee Avenue, Kowloon,
Hong Kong, People’s Republic of China
Received August 25, 2003
A (meso-tetrakis(pentafluorophenyl)porphyrinato)ruthenium(II) complex of PhNdCH(p-
ClPh) is prepared by reacting [Ru(F20-TPP)(CO)] (1) with a benzene solution of N-(p-
chlorobenzylene)aniline. The crystal structure of {Ru(F20-TPP)(CO)[PhNdCH(p-ClPh)]} (10)
shows the coordinated imine ligand in a cis configuration. Comparison with X-ray crystal-
lographic data for [Ru(F20-TPP)(py)2] (11) revealed the axial Ru-N bond length of the imine
complex (2.203 Å) to be slightly longer than that of the bis(pyridine) complex (2.108 Å).
Spectral and structural data revealed the Ru-N(imine) bond to have single-bond character,
and the RudC bond in [Ru(F20-TPP)(CPh2)] (7) has a bond distance of 1.842 Å, indicative of
multiple-bond character. In the presence of diazo compounds, {Ru(F20-TPP)(CO)[PhNdCH-
(p-ClPh)]} (10) and other related complexes mediated diastereoselective imine aziridination
with product yields up to 86%. The mechanism is suggested to involve activation of the
imine and diazo compounds by the ruthenium(II) porphyrin catalyst followed by nucleophilic
addition of the imine to the diazo ester and subsequent cyclization to give the aziridine.
In tr od u ction
In comparison to alkene aziridination, the addition
of metallocarbenoids to imines has been less successful.
J acobsen and co-workers showed that a copper-cata-
lyzed protocol gave aziridines either with high enantio-
selectivity or as a racemate.13 Wulff et al. demonstrated
that a similar outcome could be accomplished from
Lewis acid mediated cyclopropanation of imines with
The ability of aziridines to undergo regio- and ste-
reoselective ring-opening reactions renders them in-
valuable building blocks in organic synthesis.1 Aziri-
dines are found in a number of biologically active
products such as mitomycins and azinomycins.1,2 How-
ever, in contrast to extensive investigations on organic
oxidations and C-C bond formation reactions, studies
on stereoselective C-N bond formations remain sparse.
Recent studies by us3 and others4-12 demonstrated the
simplicity and versatility of transition-metal catalysts
for nitrene transfer reactions. Works by Du Bois11 and
in our laboratory3i,j recently described examples of such
processes for the intramolecular amidation of saturated
C-H bonds and aziridination of alkenes catalyzed by
rhodium(II,II) dimers in high product yields and en-
antioselectivity.
(3) (a) Au, S.-M.; Zhang, S.-B.; Fung, W.-H.; Yu, W.-Y.; Che, C.-M.;
Cheung, K.-K. Chem. Commun. 1998, 2677. (b) Au, S.-M.; Huang, J .-
S.; Yu, W.-Y.; Fung, W.-H.; Che, C.-M. J . Am. Chem. Soc. 1999, 121,
9120. (c) Zhou, X.-G.; Yu, X.-Q.; Huang, J .-S.; Che, C.-M. Chem.
Commun. 1999, 2377. (d) Yu, X.-Q.; Huang, J .-S.; Zhou, X.-G.; Che,
C.-M. Org. Lett. 2000, 2, 2233. (e) Au, S.-M.; Huang, J .-S.; Che, C.-M.;
Yu, W.-Y. J . Org. Chem. 2000, 65, 7858. (f) Liang, J .-L.; Yu, X.-Q.;
Che, C.-M. Chem. Commun. 2002, 124. (g) Liang, J .-L.; Huang, J .-S.;
Yu, X.-Q.; Zhu, N.; Che, C.-M. Chem. Eur. J . 2002, 8, 1563. (h) Liang,
J .-L.; Yuan, S.-X.; Huang, J .-S.; Yu, W.-Y.; Che, C.-M. Angew. Chem.,
Int. Ed. 2002, 41, 3465. (i) Liang, J .-L.; Yuan, S.-X.; Chan, P. W. H.;
Che, C.-M. Org. Lett. 2002, 4, 4507. (j) Liang, J .-L.; Yuan, S.-X.; Chan,
P. W. H.; Che, C.-M. Tetrahedron Lett. 2003, 44, 5917.
(4) (a) Breslow, R.; Gellman, S. H. Chem. Commun. 1982, 1400. (b)
Breslow, R.; Gellman, S. H. J . Am. Chem. Soc. 1983, 105, 6728. (c)
Yang, J .; Weinberg, R.; Breslow, R. Chem. Commun. 2000, 531.
(5) (a) Mu¨ller, P.; Baud, C.; J acquier, Y. Tetrahedron 1996, 52, 1543.
(b) Na¨geli, I.; Baud, C.; Bernardinelli, G.; J acquier, Y.; Moran, M.;
Mu¨ller, P. Helv. Chim. Acta 1997, 80, 1087. (c) Mu¨ller, P.; Baud, C.;
J acquier, Y. Can. J . Chem. 1998, 76, 738.
* To whom correspondence should be addressed. Fax: (852) 2857
1586. Tel: (852) 2859 2154. E-mail: cmche@hku.hk.
† The University of Hong Kong.
‡ City University of Hong Kong.
(1) (a) Tanner, D. Angew. Chem., Int. Ed. 1994, 6, 625. (b) Osborn,
H. M. I.; Sweeney, J . Tetrahedron 1997, 8, 1693. (c) Stamm, H. J . Prakt.
Chem. 1999, 4, 319. (d) Atkinson, R. S. Tetrahedron 1999, 55, 1519.
(e) Dodd, R. H. Molecules 2000, 5, 293. (f) McCoull, W.; Davis, F. A.
Synthesis 2000, 10, 1347. (g) Sweeney, J . B. Chem. Soc. Rev. 2002,
31, 247.
(6) (a) Levites-Agababa, E.; Menhaji, E.; Perlson, L. N.; Rojas, C.
M. Org. Lett. 2002, 4, 863. (b) Padwa, A.; Stengel, T. Org. Lett. 2002,
4, 2137.
(7) (a) Mahy, J . P.; Bedi, G.; Battioni, P.; Mansuy, D. Tetrahedron
Lett. 1988, 29, 1927. (b) Mahy, J . P.; Bedi, G.; Battioni, P.; Mansuy,
D. New J . Chem. 1989, 13, 651.
(2) Kasai, M.; Kono, M. Synlett 1992, 778.
10.1021/om034128b CCC: $27.50 © 2004 American Chemical Society
Publication on Web 12/09/2003

Ru(II) Porphyrin Catalyzed Imine Aziridination
Organometallics, Vol. 23, No. 1, 2004 55
ethyl diazoacetate (EDA) using a biaryl boronate cata-
lyst.14 Other Lewis acids such as boron, iron, molybde-
num, and tin complexes have been less successful in
asymmetric aziridination.15,16 More recently, Aggarwal
and co-workers reported an alternative approach that
utilized the reaction of sulfur ylides with imines. The
rhodium(II,II) dimer catalyzed aziridination procedure
afforded a variety of aziridines in excellent enantio-
selectivity, albeit with modest diastereoselectivity.17
Ruthenium(II) porphyrin catalyzed carbenoid trans-
formations using diazo compounds have been receiving
growing interest (Figure 1).18,19 We recently described
a highly regio- and enantioselective ruthenium porphy-
rin catalyzed alkene cyclopropanation reaction that both
gives good yields and is accomplished with high product
turnovers.18a,d In light of this work, we wondered
whether ruthenium(II) porphyrin catalysts could be
applied to the catalytic cyclopropanation of imines.
(8) (a) Evans, D. A.; Faul, M. M.; Bilodeau, M. T. J . Org. Chem.
1991, 56, 6744. (b) Li, Z.; Conser, K. R.; J acobsen, E. N. J . Am. Chem.
Soc. 1993, 115, 5326. (c) Evans, D. A.; Faul, M. M.; Bilodeau, M. T. J .
Am. Chem. Soc. 1994, 116, 2742. (d) Sodergren, M. J .; Alonso, D. A.;
Anderson, P. G. Tetrahedron: Asymmetry 1997, 8, 3563. (e) Ando, T.;
Minakata, S.; Ryu, I.; Komatsu, M. Tetrahedron Lett. 1998, 39, 4715.
(f) Simonato, J .-P.; Pecaut, J .; Scheidt, W. R.; Marchon, J .-C. Chem.
Commun. 1999, 989. (g) Kohmura, Y.; Katsuki, T. Tetrahedron Lett.
2001, 42, 3339. (h) Bach, T.; Schlummer, B.; Harms, K. Chem. Eur. J .
2001, 7, 2581. (i) Gillespie, K. M.; Sanders, C. J .; O’Shaughnessy, P.;
Westmoreland, I.; Thickitt, C. P.; Scott, P. J . Org. Chem. 2002, 67,
3450.
(9) (a) Dauban, P.; Dodd, R. H. Org. Lett. 2000, 2, 2327. (b) Chenna,
P. H. D.; Dauban, P.; Ghini, A.; Burton, G.; Dodd, R. H. Tetrahedron
Lett. 2000, 41, 7041. (c) Dauban, P.; Dodd, R. H. Tetrahedron Lett.
2001, 42, 1037. (d) Dauban, P.; Sanie`re, L.; Tarrade, A.; Dodd, R. H.
J . Am. Chem. Soc. 2001, 123, 7707. (e) Duran, F.; Leman, L.; Ghini,
A.; Burton, G.; Dauban, P.; Dodd, R. H. Org. Lett. 2002, 4, 2481.
(10) (a) Cotton, F. A.; Walton, R. A. Multiple Bonds Between Metal
Atoms; Clarendon Press: Oxford, U.K., 1993. (b) Doyle, M. P.; Forbes,
D. C. Chem. Rev. 1998, 98, 911. (c) Mu¨ller, P.; Fruit, C. Chem. Rev.
2003, 103, 2905.
(11) (a) Espino, C. G.; Du Bois, J . Angew. Chem., Int. Ed. 2001, 40,
598. (b) Espino, C. G.; Wehn, P. M.; Chow, J .; Du Bois, J . J . Am. Chem.
Soc. 2001, 123, 6935. (c) Wehn, P. M.; Du Bois, J . J . Am. Chem. Soc.
2002, 124, 12950. (d) Guthikonda, K.; Du Bois, J . J . Am. Chem. Soc.
2002, 124, 13672. (e) Fleming, J . J .; Fiori, K. W.; Du Bois, J . J . Am.
Chem. Soc. 2003, 125, 2028.
(12) (a) Woo, L. K.; Goll, J . G.; Czapla, D. J .; Hays, J . A. J . Am.
Chem. Soc. 1991, 113, 8478. (b) Woo, L. K. Chem. Rev. 1993, 93, 1125.
(c) Chen, J .; Woo, L. K. Inorg. Chem. 1998, 37, 3269. (d) Thorman, J .
L.; Woo, L. K. Inorg. Chem. 2000, 39, 1301.
(13) Hansen, K. B.; Finney, N. S.; J acobsen, E. N. Angew. Chem.,
Int. Ed. 1995, 34, 676.
(14) (a) Antilla, J . C.; Wulff, W. D. J . Am. Chem. Soc. 1999, 121,
5099. (b) Antilla, J . C.; Wulff, W. D. Angew. Chem., Int. Ed. 2000, 39,
4518.
F igu r e 1. Ruthenium porphyrin catalysts 1-9. Abbrevia-
tions (*): H2(F20-TPP) ) meso-tetrakis(pentafluorophe-
nyl)porphyrin; H2(TTP) ) meso-tetrakis(tolyl)porphyrin;
H2(p-F-TPP) ) meso-tetrakis(p-fluorophenyl)porphyrin; H2(p-
Cl-TPP) ) meso-tetrakis(p-chlorophenyl)porphyrin. For
1-3 and 5-7, the complexes could be five-coordinate or Y
) solvent molecule.
Ruthenium(II) porphyrins have previously been shown
to catalyze the enantio- and diastereoselective aziridi-
nation of CdC bonds using (N-(p-tolylsulfonyl)imino)-
phenyliodinane as the nitrogen source.3b,c,g,18f Herein,
we report the first Ru-catalyzed aziridination reactions
of aryl imines with diazo compounds and, in the course
of this work, the isolation and characterization by X-ray
crystallography of a stable (porphyrinato)ruthenium(II)
imine complex (Scheme 1).
(15) (a) Moran, M.; Bernardinelli, G.; Mu¨ller, P. Helv. Chim. Acta
1995, 78, 2048. (b) Casarrubios, L.; Pe´rez, J . A.; Brookhart, M.;
Templeton, J . L. J . Org. Chem. 1996, 61, 8358. (c) Mohan, J . M.;
Uphade, B. S.; Ravindranathan, T.; Sudalai, A. Chem. Commun. 1997,
1429. (d) Gunnoe, T. B.; White, P. S.; Templeton, J . L.; Casarrubios,
L. J . Am. Chem. Soc. 1997, 119, 3171. (e) Nagayama, S.; Kobayashi,
S. Chem. Lett. 1998, 7, 685. (f) Wright, D. L.; McMills, M. C. Org. Lett.
1999, 1, 667. (g) Kubo, T.; Sakaguchi, S.; Ishii, Y. Chem. Commun.
2000, 625. (h) Mayer, M. F.; Wang, Q.; Hossain, M. M. J . Organomet.
Chem. 2001, 630, 78. (i) Morales, D.; Pe´rez, J .; Riera, L.; Corzo-Sua´rez,
R.; Garc´ıa-Granda, S.; Miguel, D. Organometallics 2002, 21, 1540. (j)
Mayer, M. F.; Hossain, M. M. J . Organomet. Chem. 2002, 654, 202.
(k) Heuss, B. D.; Mayer, M. F.; Dennis, S.; Hossain, M. M. Inorg. Chim.
Acta 2003, 342, 301.
(16) (a) Rasmussen, K. G.; J ørgensen, K. A. Chem. Commun. 1995,
1401. (b) Rasmussen, K. G.; Hazell, R. G.; J ørgensen, K. A. Chem.
Commun. 1997, 1103. (c) Rasmussen, K. G.; J uhl, K.; Hazell, R. G.;
J ørgensen, K. A. J . Chem. Soc., Perkin Trans. 2 1998, 1347. (d) Mayer,
M. F.; Hossain, M. M. J . Org. Chem. 1998, 63, 6839. (e) J uhl, K.; Hazell,
R. G.; J ørgensen, K. A. J . Chem. Soc., Perkin Trans. 1 1999, 2293.
(17) (a) Aggarwal, V. K.; Ferrara, M.; O’Brien, C. J .; Thompson, A.;
J ones, R. V. H.; Fieldhouse, R. J . Chem. Soc., Perkin Trans. 1 2001,
1635. (b) Aggarwal, V. K.; Alonso, E.; Fang, G.; Ferrara, M.; Hynd, G.;
Porcelloni, M. Angew. Chem., Int. Ed. 2001, 40, 1433. (c) Aggarwal, V.
K.; Stenson, R. A.; J ones, R. V. H.; Fieldhouse, R.; Blacker, J .
Tetrahedron Lett. 2001, 42, 1587.
Resu lts a n d Discu ssion
A. Syn th esis, Isola tion , a n d Sp ectr a of {Ru (F 20
-
TP P )(CO)[P h NdCH(p-ClP h )]} (10). In contrast to the
vast number of metal complexes with chelating imines20
and simple monodentate imines15e,21 reported in the
literature, studies examining the binding behavior of
(18) For selected examples, see: (a) Lo, W.-C.; Che, C.-M.; Cheng,
K.-F.; Mak, T. C.-W. Chem. Commun. 1997, 1205. (b) Huang, J .-S.;
Sun, X.-R.; Leung, S. K.-Y.; Cheung, K.-K.; Che, C.-M. Chem. Eur. J .
2000, 6, 334. (c) Huang, J .-S.; Leung, S. K.-Y.; Cheung, K.-K.; Che,
C.-M. Chem. Eur. J . 2000, 6, 2971. (d) Che, C.-M.; Huang, J .-S.; Lee,
F.-W.; Li, Y.; Lai, T.-S.; Kwong, H.-L.; Teng, P.-F.; Lee, W.-S.; Lo, W.-
C.; Peng, S.-M.; Zhou, Z.-Y. J . Am. Chem. Soc. 2001, 123, 4119. (e)
Zheng, S.-L.; Yu, W.-Y.; Che, C.-M. Org. Lett. 2002, 4, 889. (f) Zhang,
J .-L.; Che, C.-M. Org. Lett. 2002, 4, 1911. (g) Zhou, C.-Y.; Yu, W.-Y.;
Che, C.-M. Org. Lett. 2002, 4, 3235. (h) Zheng, S.-L.; Yu, W.-Y.; Xu,
M.-X.; Che, C.-M. Tetrahedron Lett. 2003, 44, 1445. (i) Zhou, C.-Y.;
Chan, P. W. H.; Yu, W.-Y.; Che, C.-M. Synthesis 2003, 9, 1403. (j)
Zhang, J .-L.; Chan, P. W. H.; Che, C.-M. Tetrahedron Lett. 2003, 44,
8733.

56 Organometallics, Vol. 23, No. 1, 2004
Li et al.
Figure 2 depicts the 1H NMR spectrum of 10 in
deuteriochloroform. This spectrum features the pyrrole
protons of the porphyrinato ligand shifted slightly
upfield to 8.65 ppm relative to that of 1 (8.71 ppm). The
aryl proton signals of the imine are significantly shifted
upfield, assignable to the porphyrin ring current effect.
A similar effect can be seen for the aryl proton signals
of [Ru(F20-TPP)(CPh2)] (7) and [Ru(F20-TPP)(py)2] (11)
(Table 1). In contrast, the proton resonance of (p-ClPh)-
CHdN in N-(p-chlorobenzylene)aniline shifts downfield
to 8.73 ppm relative to that of free (p-chlorobenzylidene)-
aniline (8.38 ppm). This is similar to the data observed
for [(η5-C5H5)Fe(CO)2(PhNdCHPh)]16d and monosubsti-
tuted carbene-ligated metalloporphyrins.20 However, for
other reported imine-coordinated ruthenium(II) porphy-
rins, the opposite was found for the proton resonance
of the imino carbon.18c The 13C NMR of 10 exhibits a
carbon resonance for PhCHdN at 176.7 ppm. In the free
imine, the corresponding signal is at 160.4 ppm. For the
imine-ligated SnCl4 and BF3 complexes,16c the imino
carbon resonance was found further upfield, whereas
for [(η5-C5H5)Fe(CO)2(PhNdCHPh)], it is downfield at
186.4 ppm.16d
The UV/vis absorption spectrum of 10 exhibits a
slightly red shifted Soret band at λ 406 nm. The
spectrum, shown in Figure 3, is characteristic of ruthe-
nium(II) porphyrins with σ-donating axial ligands, such
as amines and nitriles. This Soret band is slightly lower
in energy than those observed for [Ru(F20-TPP)(CO)] (1;
λ 402 nm) and [Ru(F20-TPP)(py)2] (11; λ 399 nm). As is
evident from the inset in Figure 3, the spectrum of 10
is similar to that of 1 but significantly different from
those of 7 and 11.
Sch em e 1
ruthenium porphyrins to imines are sparse. In fact, only
a few mononuclear cationic metal complexes that con-
tain two or three simple imine ligands have been
reported.21c,d,g,h Simonneaux and co-workers observed
the formation of ruthenium porphyrins bearing imino
and amino ester groups as axial ligands.19a,d In these
metalloporphyrin species the strongly electron-with-
drawing groups on the imino carbon were suggested to
enhance imine coordination to Ru due to a π-back-
bonding interaction. More recently, we reported the
crystal structures of air-stable bis(imine)(porphyrinato)-
ruthenium(II) complexes obtained through an unprec-
edented oxidative N-dealkylation of triethylamine by
dioxoruthenium(VI) porphyrins.18c The CdN bond ge-
ometries of the coordinated imines in these complexes
were shown to exclusively adopt a cis configuration.
In this work, the addition of [Ru(F20-TPP)(CO)] (1)
to a C6H6 solution containing N-(p-chlorobenzylene)-
aniline gave {Ru(F20-TPP)(CO)[PhNdCH(p-ClPh)]} (10)
in 80% yield. Complex 10 is stable in solution and in
the solid state for several weeks. As expected, it is
diamagnetic with well-resolved 1H NMR signals at
normal fields, consistent with known literature data for
ruthenium(II) porphyrins. The spectral data are sum-
marized in Table 1. For comparison, the data for [Ru-
At this juncture, it is worth mentioning the effect of
axial imine ligation on the MfNdC π-back-bonding
interaction. In general, the strength of MfL increases
with increasing π-acidity of L. Previous works by us18c,23
and Gouterman et al.24 showed that, for iron, ruthe-
nium, and osmium meso-tetraaryl- and octaethylpor-
phyrins, both the â band wavelength in the UV/vis
(F20-TPP)(CO)] (1), free PhNdCH(p-ClPh), [Ru(F20
-
TPP)(CPh2)] (7), [Ru(F20-TPP)(py)2] (11; py ) pyridine),
and pyridine are also included in the table. Complexes
7 and 11 were obtained from the reaction of diphenyl-
diazomethane with [Ru(F5-TPP)(CO)] and [Ru(F5-TPP)-
(CPhCO2Et)]22 with pyridine, respectively.
1
spectrum and the Hmeso chemical shift in the H NMR
spectrum systematically decrease as the π-acidity of the
axial ligand decreases. Thus, while a comparison of the
â band wavelengths and Hmeso chemical shifts of [Ru-
(F20-TPP)(CO)] (1) with those of 11 reveals that there
might be weak Rufpy back-bonding in 11, the same
comparison made for 1 and 10 reveals that the RufNd
C back-bonding in 10 is negligible (see Table 1 and
Figure 3).
The IR spectrum of 10 gives an absorption at 1967
cm-1 for ν(CO) that is at a frequency slightly higher
than that observed for 1 (1963 cm-1). A similar change
in ν(CO) stretching frequency has previously been
reported for [Ru(TTP)(CO)] (2) and [Ru(TTP)(CO)(py)]
(ν(CO) 1934 and 1939 cm-1, respectively).25 The “oxida-
tion state marker” band of 10 at ν 1011 cm-1 is identical
with that observed for 1, 7, and 11. Interestingly, for
all these complexes bearing a meso-tetrakis(pentafluo-
(19) For selected examples, see: (a) Morice, C.; Maux, P. L.;
Simonneaux, G. Tetrahedron Lett. 1996, 37, 6701. (b) Frauenkron, M.;
Berkessel, A. Tetrahedron Lett. 1997, 38, 7175. (c) Galardon, E.; Le
Maux, P.; Simonneaux, G. Chem. Commun. 1997, 927. (d) Morice, C.;
Maux, P. L.; Moinet, C.; Simonneaux, G. Inorg. Chim. Acta 1998, 273,
142. (e) Klose, A.; Solari, E.; Floriani, C.; Geremia, S.; Randaccio, L.
Angew. Chem., Int. Ed. 1998, 37, 148. (f) Galardon, E.; Le Maux, P.;
Toupet, L.; Simonneaux, G. Organometallics 1998, 17, 565. (g) Gross,
Z.; Galili, N.; Simkhovich, L. Tetrahedron Lett. 1999, 40, 1571. (h)
Galardon, E.; Le Maux, P.; Simonneaux, G. Tetrahedron 2000, 56, 615.
(i) Chen, Y.; Huang, L.; Ranade, M. A.; Zhang, X. P. J . Org. Chem.
2003, 68, 3714.
(20) Comprehensive Coordination Chemistry; Wilkinson, G., Gillard,
R. D., McCleverty, J . A., Eds.; Pergamon: Oxford, U.K., 1987.
(21) For selected examples, see: (a) King, R. B.; Douglas, W. M.
Inorg. Chem. 1974, 13, 1339. (b) Cross, R. J .; Davidson, M. F.;
Rocamora, M. J . Chem. Soc., Dalton Trans. 1988, 1147. (c) Becalski,
A. G.; Cullen, W. R.; Fryzuk, M. D.; J ames, B. R.; Kang, G.-J .; Rettig,
S. J . Inorg. Chem. 1991, 30, 5002. (d) Wong, K.-Y.; Che, C.-M.; Li, C.
K.; Chiu, W.-H.; Zhou, Z. Y.; Mak, T. C. W. J . Chem. Soc., Chem.
Commun. 1992, 754. (e) Francisco, L. W.; White, P. S.; Templeton, J .
L. Organometallics 1996, 15, 5127. (f) Bohanna, C.; Esteruelas, M. A.;
Lo´pez, A. M. Oro, L. A. J . Organomet. Chem. 1996, 526, 73. (g)
Schneider, W.; Bauer, A.; Schmidbaur, H. Chem. Ber. Recl. 1997, 130,
947. (h) Schneider, W.; Bauer, A.; Schmidbaur, H. J . Chem. Soc., Dalton
Trans. 1997, 415. (i) Albeniz, M. J .; Buil, M. L.; Esteruelas, M. A.;
Lo´pez, A. M. J . Organomet. Chem. 1997, 546, 495. (j) Stark, G. A.;
Gladysz, J . A. Inorg. Chim. Acta 1998, 269, 167.
(22) Unpublished work.
(23) Li, Z.-Y.; Huang, J .-S.; Chan, M. C.-W.; Cheung, K.-K.; Che,
C.-M. Inorg. Chem. 1997, 36, 3064.
(24) (a) Antipas, A.; Buchler, J . W.; Gouterman, M.; Smith, P. D. J .
Am. Chem. Soc. 1978, 100, 3015. (b) Antipas, A.; Buchler, J . W.;
Gouterman, M.; Smith, P. D. J . Am. Chem. Soc. 1980, 102, 198.
(25) Bonnet, J . J .; Eaton, S. S.; Eaton, G. R.; Holm, R. H.; Ibers, J .
A. J . Am. Chem. Soc. 1973, 95, 2141.

Ru(II) Porphyrin Catalyzed Imine Aziridination
Organometallics, Vol. 23, No. 1, 2004 57
F igu r e 2. 1H NMR spectrum of {Ru(F20-TPP)(CO)[PhNdCH(p-ClPh)]} (10) in CDCl3.
Ta ble 1. 1H NMR Sp ectr u m of Com p lex 10 As
Com p a r ed w ith Th ose of [Ru (F 20-TP P )(CO)] (1),
F r ee P h NdCH(p-ClP h ), [Ru (F 20-TP P )(CP h 2)] (7),
[Ru (F 20-TP P )(p y)2] (11), a n d P yr id in e
PhNdCH(p-ClPh)
Hâ
Ha
Hb
Hc
Hd
He
Hf
(s, 8H) (s, 1H) (d, 2H) (d, 2H) (d, 2H) (t, 2H) (t, 1H)
1
8.71
10
8.65
8.73 4.66
8.38
6.35
2.45
6.09
6.43
PhNdCH-
(p-ClPh)
7.18-7.25 (m, 3H), 7.35-7.43 (m, 4H),
7.80-7.82 (m, 2H)
Hâ
(s, 8H)
Ph Hp
(t, 2H)
Ph Hm
(t, 4H)
Ph Ho
(d, 4H)
7
8.32
6.39
6.14
3.14
Hâ
(s, 8H)
py Hp
(t, 2H)
py Hm
(t, 4H)
py Ho
(d, 4H)
11
pyridine
8.08
6.07
7.67
5.20
7.28
2.55
8.61
F igu r e 3. UV/vis spectrum of {Ru(F20-TPP)(CO)[PhNd
CH(p-ClPh)]} (10) in CH2Cl2. A comparison of the spectral
data with those of Ru(II) complexes 1, 7, and 11 is shown
in the inset.
rophenyl)porphyrin ligand, the “oxidation state marker”
bands are identical with related values observed for
ruthenium(IV) meso-tetraarylporphyrin complexes.18c
Furthermore, they are at a higher frequency than the
“oxidation state marker” bands typically observed for
ruthenium(II) meso-tetraarylporphyrins (ca. 1000 cm-1),
reflecting the effect of the electron-withdrawing fluorine
substituent on the ruthenium(II) porphyrin core.18c The
positive ion FAB spectrum of 10 exhibits three signals
that can be attributed to the parent ion [M]+ and the
[M - CO]+ and [M - C13H10ClN - CO]+ fragments.
B. X-r a y Cr ysta l Str u ctu r e of {Ru (F 20-TP P )(CO)-
[P h NdCH(p-ClP h )]} (10).26 Complex 10 was recrys-
tallized from CH2Cl2/n-hexane at room temperature. A
perspective view of 10 is depicted in Figure 4. The
crystal data and structural refinement details are given
in Table 2.26 For comparison, the crystal structures of
[Ru(F20-TPP)(CPh2)] (7) and [Ru(F20-TPP)(py)2] (11) are
included. Perspective views of 7 and 11 are shown in
Figures 5 and 6, respectively.26
As shown in Figure 4, the PhNdCH(p-ClPh) ligand
adopts a cis configuration, presumably to minimize
unfavorable steric interaction with the porphyrinato
ligand.27 The Ru-N(imine) bond is nearly perpendicular
to the plane of the porphyrin ring, with the N(imine)-
Ru-C(CO) angle being 178.5°. As expected for sp2-
hybridized N atoms, the sum of the C(2)-N(5)-C(9),
Ru-N(5)-C(2), and Ru-N(5)-C(9) angles is 358°,
which is close to the 360° value required for a planar
configuration. For the coordinated imine, both the
aniline and benzylidene rings reside in planes that
traverse the plane of the CdN moiety. The dihedral
(26) The files CCDC 211007, 211008, and 211189 contain the
supplementary crystallographic data for this paper. These data can
be obtained free of charge via www.ccdc.cam.ac.uk/conts/retrieving-
.html (or from the CCDC, 12 Union Road, Cambridge CB2 1EZ, U.K.;
fax +44 1223 336033; e-mail deposit@ccdc.cam.ac.uk).
(27) In solution, free imines preferentially occupy the more stable
trans configuration; see: Bjørgo, J .; Boyd, D. R.; Watson, C. G. J . Chem.
Soc., Perkin Trans 2 1974, 1081.

58 Organometallics, Vol. 23, No. 1, 2004
Li et al.
F igu r e 4. Perspective view of {Ru(F20-TPP)(CO)[PhNdCH(p-ClPh)]} (10). Hydrogen atoms and solvent molecules have
been omitted for clarity. Selected bond lengths (Å) and angles (deg): Ru-N(5) ) 2.203(7), Ru-C(1) ) 1.860(10), Ru-N(1)
) 2.059(6), Ru-N(2) ) 2.050(6), Ru-N(3) ) 2.059(6), Ru-N(4) ) 2.045(6), C(1)-O(1) ) 1.130(1), N(5)-C(2) ) 1.300(1),
N(5)-C(9) ) 1.4500(1); C(2)-N(5)-C(9) ) 117.9(7), Ru-N(5)-C(2) ) 120.9(6), Ru-N(5)-C(9) ) 120.2(5), N(5)-Ru-C(1)
) 178.5(3), N(5)-Ru-N(1) ) 88.2(2), N(5)-Ru-N(2) ) 90.2(3), N(5)-Ru-N(3) ) 88.7(2), N(5)-Ru-N(4) ) 86.8(3), N(1)-
Ru-N(3) ) 177.0(3), N(2)-Ru-N(4) ) 177.0(3).26
Ta ble 2. Cr ysta l Da ta a n d Str u ctu r e Refin em en t Deta ils for [Ru (F 20-TP P )(CP h 2)] (7),
{Ru (F 20-TP P )(CO)[P h NdCH(p-ClP h )]} (10), a n d [Ru (F 20-TP P )(p y)2] (11)
7‚0.5C4H9OH
10‚C6H14‚C2H5OH
11‚2CH2Cl2‚2H2O
empirical formula
formula wt
cryst syst
space group
a, Å
b, Å
c, Å
C
57H18F20N4Ru‚0.5C4H9OH
C58H18ClF20N5ORu‚C6H14‚C2H5OH
C54H32F20N6O2Ru‚2CH2Cl2‚2H2O
1276.88
monoclinic
P21/n
18.768(4)
14.491(3)
18.936(4)
90
90.64(3)
90
5149.6(18)
4
1449.55
triclinic
P1h
1437.70
monoclinic
Cc
26.593(3)
8.8500(10)
27.101(3)
90
113.669(2)
90
5841.7(12)
4
10.399(3)
14.908(4)
23.480(5)
100.24(2)
101.51(2)
107.83(2)
3282(1)
2
R, deg
â, deg
γ, deg
V, Å3
Z
F(000)
2532
1452
2880
density (calcd), g/cm3
abs coeff, cm-1
cryst size, mm-3
no. of rflns collected
no. of indep rflns
no. of data/restraints/params
1.647
0.424
1.467
3.83
1.644
0.564
0.25 × 0.2 × 0.1
0.25 × 0.15 × 0.1
0.14 × 0.12 × 0.06
33 747
12 068
9202
8699
6119
9202
8699/0/763
0.047/0.13 (I > 2σ(I))
0.08/0.14
0.97
6119/0/711
0.06/0.09 (I > 3σ(I))
0.06/0.09
2.4
9202/36/803
0.048/0.12 (I > 2σ(I))
0.088/0.15
0.81
Ra/Rw
b
Ra/Rw (all data)
b
goodness of fit
largest diff peak/hole, e Å-3
0.508/-0.573
0.97/-0.60
0.504/-0.594
a
b
2
R ) ∑||Fo| - |Fc||/∑|Fo|. Rw ) [∑w(||Fo| - |Fc|)2|/∑w|Fo| ]1/2
.
angle between the plane of the aniline ring and the
plane of the CdN moiety is 36°, and that between this
latter plane and the plane of the benzylidene ring is
106°. This would suggest π-conjugation between the
aromatic rings and the imine CdN bond that would be
present in the free imine is negligible upon ligation to
ruthenium. Despite this, coordination of the imine
ligand results in minimal distortion of the Ru atom from

Ru(II) Porphyrin Catalyzed Imine Aziridination
Organometallics, Vol. 23, No. 1, 2004 59
F igu r e 5. Perspective view of [Ru(F20-TPP)(CPh2)] (7). Hydrogen atoms and solvent molecules have been omitted for
clarity. Selected bond lengths (Å) and angles (deg): Ru-C(45) ) 1.842(4), Ru-N(1) ) 2.046(3), Ru-N(2) ) 2.054(3), Ru-
N(3) ) 2.047(3), Ru-N(4) ) 2.045(3), C(45)-C(46) ) 1.491(5), C(45)-C(52) ) 1.509(6); C(45)-Ru-N(1) ) 99.94(14), C(45)-
Ru-N(2) ) 94.26(13), C(45)-Ru-N(3) ) 95.05(14), C(45)-Ru-N(4) ) 94.30(14), N(1)-Ru-N(3) ) 165.0(1), N(2)-Ru-
N(4) ) 171.44(11), C(46)-C(45)-C(52) ) 113.4(3), C(46)-C(45)-Ru ) 125.1(3), C(52)-C(45)-Ru ) 121.5(3).26
the calculated least-squares plane of the porphyrinato
ring (0.0544 Å), offsetting the metal slightly toward the
CO ligand. A similar mode of coordination is found in
both 7 and 11. For [Ru(F20-TPP)(py)2] (11) the two axial
pyridine ligands are close to right angles to the plane
of the porphyrin ring with N(py)-Ru-N(pyrrole) angles
ranging from 87.23 to 93.35°. The two pyridine rings
are located in the same plane with respect to each other,
with a dihedral angle between these two planes equal
to 1.28°. For both 10 and 11, the dihedral angles
between the C(2)-N(5)-C(9) and N(5)-Ru-N(1)-N(3)
planes in 10 and C(45)-N(5)-C(49) and N(5)-Ru-
N(1)-N(3) planes in 11 are 43.1 and 47.8°, respectively.
Thus, there is no apparent unfavorable steric interaction
between the porphyrin ring and the axial ligands; the
imine and bis pyridine ligands are located in planes that
bisect the Ru-N bonds of the porphyrin ring in 10 and
11, as shown in parts a and b of Figure 7, respectively.
As shown in Figure 5, the carbon donor atom of the
diphenylcarbene ligand in 7 adopts an sp2-hybridized
configuration, as evidenced by the sum of the C(46)-
C(45)-C(52), C(46)-C(45)-Ru, and C(52)-C(45)-Ru
angles equal to 360°. In contrast to 10 and 11, coordina-
tion of the carbene ligand results in greater distortion
of the ruthenium atom from the calculated least-squares
plane of the porphyrin ring in a direction toward the
carbene ligand (0.2099 Å). This results in the ruthenium
atom adopting a slightly distorted-square-pyramidal
coordination sphere with the carbene C atom at the
vertex site. Furthermore, with the dihedral angle be-
tween the C(46)-C(45)-C(52) and C(45)-Ru-N(2)-
N(4) planes equal to 20.8°, the axial ligand is situated
much more closely to the C(45)-Ru-N(2)-N(4) plane
in comparison to that found in 10 and 11. Presumably
in this conformation any unfavorable steric interaction
with the porphyrin ring is kept to a minimum (Figure
7c).
The N(imine)-Ru distance in 10 is 2.203 Å. This is
comparable to the Ru-N distances in [Ru(TPP)(CO)-
(py)] (2.193 Å) and [Ru(TPP)(CO)(1-MeIm)] (2.187 Å) (1-
MeIm ) 1-methylimidazole)29 but longer than those
observed for [Ru(F20-TPP)(py)2] (11; 2.108 and 2.1085
Å),26 [Ru(TTP)(EtNdCHMe)2] (2.115 Å), and [Ru(p-Cl-
TPP)(NdCPh2)2] (1.896 Å).18c The imine CdN distance
(1.30 Å) is the same as that in [Ru(TTP)(EtNdCHMe)2]
(1.30 Å) but slightly longer than those in free imines
(ca. 1.28 Å), [SnCl4(o-MeOPhNdCHPh)] (1.285 Å),16b
and [SnCl4(p-ClPhNdCHPh)] (1.288 Å).16c In addition,
the Ru-C(carbonyl) distance of 1.86 Å is longer than
those in [Ru(TPP)(CO)(EtOH)] (1.72 Å),29 [Ru(TFPPCl8)-
(CO)(H2O)] (H2(TFPPCl8) ) octa-â-chlorotetrakis(pen-
tafluorophenyl)porphyrin; 1.828 Å),30 [Ru(TPP)(CO)(py)]
(1.838 Å), and [Ru(TPP)(CO)(1-MeIm)] (1.828 Å).29
C. [Ru (F 20-TP P )(CO)] (1) Ca ta lyzed Azir id in a -
tion Rea ction s of Im in es w ith EDA. When EDA (1
equiv) was slowly added to a C6H6 solution containing
N-(benzylidene)aniline (2 equiv), [Ru(F20-TPP)(CO)] (1;
0.5 mol %), and 4 Å molecular sieves at room temper-
(28) Scheidt, W. R.; Lee, Y. J . Struct. Bonding (Berlin) 1987, 64, 1.
(29) (a) Little, R. G.; Ibers, J . A. J . Am. Chem. Soc. 1973, 95, 8583.
(b) Slebodnick, C.; Seok, W. K.; Kim, K.; Ibers, J . A. Inorg. Chim. Acta
1996, 243, 57.
(30) Birnbaum, E. R.; Schaefer, W. P.; Labinger, J . A.; Bercaw, J .
E.; Gray, H. B. Inorg. Chem. 1995, 34, 1751.

60 Organometallics, Vol. 23, No. 1, 2004
Li et al.
F igu r e 6. Perspective view of [Ru(F20-TPP)(py)2] (11). Hydrogen atoms and solvent molecules have been omitted for clarity.
Selected bond lengths (Å) and angles (deg): Ru-N(5) ) 2.1085(19), Ru-N(6) ) 2.108(2), Ru-N(1) ) 2.0368(17), Ru-N(2)
) 2.028(3), Ru-N(3) ) 2.0441(18), Ru-N(4) ) 2.056(2), N(5)-C(45) ) 1.436(4), N(5)-C(49) ) 1.317(3), N(6)-C(50) )
1.438(5), N(6)-C(54) ) 1.281(4); N(5)-Ru-N(6) ) 178.87(1), N(5)-Ru-N(1) ) 91.78(7), N(5)-Ru-N(2) ) 92.12(8), N(5)-
Ru-N(3) ) 87.63(7), N(5)-Ru-N(4) ) 88.11(8), N(6)-Ru-N(1) ) 87.23(8), N(6)-Ru-N(2) ) 88.45(9), N(6)-Ru-N(3) )
93.35(8), N(6)-Ru-N(4) ) 91.33(9), N(1)-Ru-N(3) ) 179.41(9), N(2)-Ru-N(4) ) 179.32(8), C(45)-N(5)-Ru ) 117.14-
(17), C(45)-N(5)-C(49) ) 119.9(2), C(49)-N(5)-Ru ) 122.8(2), C(50)-N(6)-Ru ) 116.1(2), C(50)-N(6)-C(54) ) 120.0-
(2), C(54)-N(6)-Ru ) 123.7(2).26
F igu r e 7. Ball-and-stick drawings showing the orientations of the axial ligands in (a) {Ru(F20-TPP)(CO)[PhNdCH(p-
ClPh)]} (10), (b) [Ru(F20-TPP)(py)2] (11), and (c) [Ru(F20-TPP)(CPh2)] (7). The φ angle is defined as described in ref 28.
ature, ethyl 1,3-diphenylaziridine-2-carboxylate was
isolated in 69% yield and with a cis:trans ratio of 2.7:1.
Under these conditions, the pyrrolidine 12, presumably
from 1,3-dipolar cycloaddition of the imine intermediate
and EDA dimer generated in situ, was also furnished
in 10% isolated yield (Table 3, entry 1). The analogous
reactions conducted in CH2Cl2 and the same solvent
system in the absence of molecular sieves gave markedly
lower yields, while higher yields of the cycloadduct 12
were found (entries 2 and 3). Similarly, when the
reaction was conducted at 50 °C, the aziridine product
was afforded in lower yield and cis selectivity along with
an increased isolated yield of 12 (entry 4).
In turning our attention to exploring the generality
of the present procedure, we examined the Ru-catalyzed
aziridination of a series of aryl imines under similar
conditions. These reactions afforded the corresponding
ethyl 1-phenyl-3-(substituted phenyl)aziridine-2-car-
boxylate products in moderate to good yields and
stereoselectivity (entries 5-16). It was interesting to
note that in all these reactions competitive formation
of the corresponding pyrrolidine 12 in yields up to 31%
was also isolated or detected by 1H NMR analysis of the
crude reaction mixtures. Other reaction side products
detected by GC-MS analysis include the corresponding
ArCHO, ArNCHCO2Et, and ArNHCH2CO2Et. In one

Ru(II) Porphyrin Catalyzed Imine Aziridination
Organometallics, Vol. 23, No. 1, 2004 61
Ta ble 3. [Ru (F 20-TP P )(CO)] (1) Ca ta lyzed
Cyclop r op a n a tion of Im in es w ith EDAa
Ta ble 4. Azir id in a tion Rea ction s of Im in es w ith
EDA by [Ru (P or )(X)] (1-9) Ca ta lystsa
aziridineb
pyrroli-
imine
en-
try
cis:
yield
(%)c
dine 12
catalyst
R1 R2 trans
yield (%)
1
2
3
[Ru(4-F-TPP)(CPh2)] (5)
[Ru(4-Cl-TPP)(CPh2)] (6)
[Ru(F20-TPP)(CPh2)] (7)
Ph Ph 1.7:1 1d
Ph Ph 1.5:1 2e
Ph Ph
Ph Ph 1:1
Ph Ph 2.5:1 60 (36)
Ph Ph 2:1 43 (31)
3
5
8
<1f
32 (44)
4g [Ru(F20-TPP)(CPh2)] (7)
22h
8
5
6
7
[Ru(4-F-TPP)(CO)] (3)
[Ru(TTP)(CO)] (2)
[Ru(F20-TPP)(NO)(OH)] (4)
10
2
1
aziridineb
Ph Ph 7.2:1 77 (45)
Ph Ph 2.7:1 86 (46)
pyrrolidine
8i [Ru(4-F-TPP)(O)2] (8)
imine
en-
try
conversion cis: yield
12
9i [{Ru(4-F-TPP)(OH)}2(O)] (9) Ph Ph 2.5:1 75 (48)
1
R1
R2
(%)c
trans (%)
yield (%)d
a
Reaction conditions: catalyst:EDA:imine) 1:200:400, C6H6, 4
1
Ph
Ph
39
32
35
44
41
31
45
41
40
37
74
38
38
40
33
36
2.7:1
2.5:1
2.5:1
1.4:1
2.3:1
2.5:1
2.2:1
3.8:1
7:1
6.5:1
6.5:1
j
3:1
2:1
69
20
30
37
72
13
74
83
78
79
58
12k
76
69
57
80
10
25
31
24
6
2e Ph
Ph
Ph
Ph
Ph
Å molecular sieves, room temperature, addition of EDA over 18 h
b
3f
4g Ph
5
6
7
8
9
10 p-BrPh
11i p-BrPh
12 o-ClPh
13 Ph
Ph
and then stirring for 3 h. Cis:trans ratios and yields were
determined by 1H NMR of the crude product using bibenzyl as a
standard and based on imine conversion (maximum 50%). c Yields
p-CH3Ph
p-C(CH3)3Ph Ph
p-OCH3Ph
p-FPh
p-ClPh
d
15h
3
in parentheses denote conversion. Diethyl maleate isolated as
the main product in 85% yield. e Diethyl maleate isolated as the
main product in 82% yield. f Diethyl maleate isolated as the main
product in 76% yield. g Reaction carried out at reflux. h Ph2CHNHPh
Ph
Ph
Ph
Ph
Ph
Ph
5
8
27
21
3
i
detected by GC analysis. Addition of EDA over 12 h.
of solutions of “7 + PhNdCH(p-ClPh)” (molar ratios 1:1
and 1:10) in deuteriochloroform (Figure 8). The 1H NMR
spectrum shows the aryl proton resonances of N-(p-
chlorobenzylidene)aniline as multiplets at 7.15-7.20,
7.32-7.45, and 7.80-7.85 ppm and the imino-carbon
proton resonance as a singlet at 8.40 ppm. These
chemical shifts are consistent with those observed for
the free imine as reported in Table 1. Imine coordination
would be expected to result in the aryl proton signals
to significantly shift upfield as a result of the porphyrin
ring current effect in a manner similar to that observed
p-ClPh
6
14 Ph
15 Ph
16 Ph
p-CH3Ph
p-OCH3Ph
o-OCH3Ph
10
19h
13
1.8:1
1.6:1
a
Reaction conditions: catalyst:EDA:imine ) 1:200:400, ben-
zene, 4 Å molecular sieves, room temperature, addition of EDA
b
for 18 h and then stirring for 3 h. Cis:trans ratios, product yields,
and conversions were determined by 1H NMR of the crude product
using bibenzyl as a standard and based on imine conversion.
c Maximum conversion 50%. 1H NMR yield. e CH2Cl2 solvent and
d
no 4 Å molecular sieves. f CH2Cl2 solvent. g Reaction conducted at
h
i
j
50 °C. Isolated yield. Catalyst:EDA:imine ) 1:200:200. Could
not be determined by 1H NMR analysis. Diethyl maleate isolated
k
1
in the H NMR spectrum of {Ru(F20-TPP)(CO)[PhNd
as the main product in 63% yield along with recovery of PhNdCH(o-
ClPh) in 63% yield.
CH(p-ClPh)]}(10), shown in Figure 2. It is conceivable
the degree of distortion of the Ru atom from the
porphyrin ring toward the axial carbene ligand is
sufficient to prevent or at least contribute to preventing
effective coordination of the sterically bulky imine. The
low yields and conversions observed for the reactions
of N-p-tert-butyl- and N-(o-chlorobenzylidene)aniline
(Table 3, entries 6 and 12) are consistent with this
suggestion. With [Ru(4-F-TPP)(CO)] (3) as catalyst,
ethyl 1-phenyl-3-phenylaziridine-2-carboxylate was af-
forded in a slightly lower yield (entry 5). The same
reaction catalyzed by [Ru(TTP)(CO)] (2) gave the aziri-
dine in 43% yield (entry 6). In contrast, higher product
yield and cis selectivity were observed for the analogous
reaction catalyzed by [Ru(F20-TPP)(NO)(OH)] (4)31 (en-
try 7). Presumably, this systematic increase in product
yields as the electrophilicity of the Ru atom increases
suggests product formation would be affected by axial
ligand to ruthenium coordination. For reactions cata-
lyzed by ruthenium porphyrins 8 and 9,32 markedly
higher product yields (up to 86%) were obtained (entries
8 and 9). Interestingly, while attempts to isolate the bis-
(imine) complex of 8 were unsuccessful, the reaction of
this catalyst (1 equiv) in the presence of excess N-(p-
chlorobenzylidene)aniline (4 equiv) in C6H6 at room
temperature gave [{Ru(p-F-TPP)(OH)}2(O)] (9) in 88%
instance, the employment of equimolar quantities of
imine and EDA was also found to result in markedly
higher substrate conversion, although no significant
increase in product yield was observed (entry 11). More
notably, imines bearing an electron-withdrawing sub-
stitutent at the para position of the benyzlidene ring
were found to undergo aziridination with higher cis
selectivity (cis:trans ratios up to 7:1) (entries 8-11).
However, for imines bearing either an electron-with-
drawing or -donating group at the para position of the
aniline ring or electron-donating substituents at the
para position of the benzylidene ring, the effect of
substitution on reaction diastereoselectivity was found
to be minimal (entries 5-7 and 13-16). The aziridina-
tions of the sterically demanding imines N-(p-tert-butyl)-
and N-(o-chlorobenzylidene)aniline are the only ex-
amples that gave low product yields and conversions
(entries 6 and 12).
The effect of the porphyrinato ring and axial ligand
on the yield and selectivity of the present protocol was
examined (Table 4). Reactions catalyzed by ruthenium-
(II) porphyrins where the axial CO ligand was replaced
with diphenylcarbene preferentially gave diethyl male-
ate in yields up to 85% (entries 1-3). The desired
aziridine product was only afforded in 32% yield under
reflux conditions along with the pyrrolidine 12 in 22%
yield (entry 4). The difference in reactivity among
catalysts 5-7 could be the absence of imine ligation at
(31) Ho, C.; Leung, W.-H., Che, C.-M. J . Chem. Soc., Dalton Trans.
1991, 2993.
(32) Collman, J . A.; Barnes, C. E.; Brothers, P. J .; Collins, T. J .;
Ozawa, T.; Gallucci, J . C.; Ibers, J . A. J . Am. Chem. Soc. 1984, 106,
5151.
1
room temperature, as suggested by H NMR analysis

62 Organometallics, Vol. 23, No. 1, 2004
Li et al.
F igu r e 8. 1H NMR spectrum of a CDCl3 solution of [Ru(F20-TPP)(CPh2)] (7) and PhNdCH(p-ClPh) (molar ratio 1:1).
yield. In this instance, rather than undergoing axial
ligation, the imine seems to act as an electron source
for the reduction of Ru(VI) to Ru(IV), leading to the
formation of the dimeric ruthenium(IV) complex 9.
These results suggest a mechanism involving ruthe-
nium porphyrin activated imine aziridination.13-16
Thought to involve ylide formation as a result of initial
nucleophilic addition of the imine to EDA, the newly
formed intermediate is also thought to subsequently
cyclize to give the aziridine. Indeed, this is supported
by the following experiments. In the absence of Ru
catalyst, the reaction of PhCHdNPh with EDA resulted
in the recovery of both starting materials in near-
quantitative yields. The addition of either (p-ClPh)CHd
added to a C6H6 solution containing dimethyl fumerate
(1.2 equiv), N-(p-chlorobenzylidene)aniline (1.2 equiv),
and 1 (0.5 mol %) at room temperature, pyrrolidine 14a
was afforded as the sole product in 90% yield (Table 5,
entry 1). The structure of 14a was confirmed by com-
1
paring its H NMR data with the literature data.35-37
Under similar conditions, trapping of the imino ylide
derived from PhNdCHPh with dimethyl acetylenedi-
carboxylate (DMAD) gave 14b in 92% yield and as a
single diastereomer (entry 2). The structure of 14b was
established by X-ray crystallography.38 1H NMR analy-
sis of the crude reaction mixture detected 14b as a
single diastereomer under our experimental conditions,
the stereochemistry of which was determined to be trans
on the basis of comparison with known literature
data.35-37 Slightly lower product yields were obtained
for the analogous cycloaddition reactions of DMAD with
either (p-tBuPh)CHdNPh or {3,4,5-(MeO)3Ph}CHdNPh
as the imine source (entries 3 and 4). In these last two
cases, exclusive trans product selectivity was deter-
NPh or (p-MePh)CHdNPh to a solution of [Ru(F20
-
TPP)(CHCO2Et)] generated in situ from the stoichio-
metric addition of EDA to 1 was also examined. These
reactions gave PhNdCHCO2Et33 in up to 93% yield
along with recovery of the corresponding benzaldehydes
in 90-92% yield. The formation of {Ru(F20-TPP)[PhNd
CH(p-ClPh)]} was also detected by 1H NMR analysis
and mass spectrometry (FAB).34 Aziridine product
formation would have suggested a mechanism similar
to that proposed for the analogous copper-catalyzed
reactions, whereby the azomethine ylide is derived from
addition of the imino nitrogen to a carbene intermedi-
ate.13 Furthermore, when 1.2 equiv of EDA was slowly
(35) (a) Deyrup, J . A. J . Org. Chem., 1969, 34, 2724. (b) Dostal, J .;
Potacek, M.; Humpa, O.; Marek, J . Bull. Soc. Chim. Belg. 1994, 103,
343.
(36) Li, G.-Y.; Chen, J .; Yu, W.-Y.; Hong, W.; Che, C.-M. Org. Lett.
2003, 5, 2153.
(37) Galliford, C. V.; Beenen, M. A.; Nguyen, S. B. T.; Scheidt, K.
A. Org. Lett. 2003, 5, 3487.
(38) See the Supporting Information for full X-ray crystallographic
details. Also: CCDC 217583 contains the supplementary crystal-
lographic data for this paper. These data can be obtained free of charge
via www.ccdc.cam.ac.uk/conts/retrieving.html (or from the CCDC, 12
Union Road, Cambridge CB2 1EZ, U.K.; fax +44 1223 336033; e-mail
deposit@ccdc.cam.ac.uk).
(33) Borrione, E.; Prato, M.; Scorrano, G.; Stivanello, M. J . Hetero-
cycl. Chem. 1988, 25, 1831.
(34) See the Supporting Information for full experimental details.

Ru(II) Porphyrin Catalyzed Imine Aziridination
Organometallics, Vol. 23, No. 1, 2004 63
Ta ble 5. 1,3-Dip ola r Cycloa d d ition of Ar yl Im in es w ith Dip ola r op h iles A-B Ca ta lyzed by
[Ru (F 20-TP P )(CO)] (1)a
a
Reaction conditions: catalyst:EDA:imine:dipolarophile A-B ) 1:200:240:240, C6H6, 4 Å molecular sieves, room temperature, addition
b
of EDA for 12 h and then stirring for 1 h. Isolated yield.
mined on the basis of 1H NMR analysis of the respective
crude reaction mixtures. With N-phenylmaleimide as
the dipolarophile, the corresponding cycloadduct 14d
was obtained in 86% yield and as a single isomer on
the basis of 1H NMR analysis of the crude reaction
mixture (entry 5). At this juncture, it is worth noting
that the present 1,3-dipolar cycloaddition procedure
provides a powerful method for the regio- and stereo-
selective synthesis of highly functionalized nitrogen
heterocycles such as pyrrolidine alkaloids.39 Further-
more, among the various literature procedures to gener-
ate reactive azomethine ylides in situ,40 the present
methodology provides an attractive approach because
of the mild reaction conditions employed and excellent
regio- and stereocontrol achieved by catalyst design.36
Indeed, works in our laboratory36 and by Scheidt and
co-workers37 recently demonstrated ruthenium(II) por-
phyrins and copper(I) salts as efficient catalysts for
Sch em e 2
effecting this one-pot, three-component transformation
with high yields and diastereoselectivity.
The delivery of 14 in all these reactions thus supports
a mechanism for the present imine aziridination reac-
(40) (a) Huisgen, R.; Grashey, R.; Steingruber, E. Tetrahedron Lett.
1963, 4, 1441. (b) Huisgen, R. Angew. Chem., Int. Ed. Engl. 1963, 2,
565. (c) Heine, H. W.; Peavy, R. Tetrahedron Lett. 1965, 6, 3123. (d)
Padwa, A.; Hamilton, L. Tetrahedron Lett. 1965, 6, 4363. (e) Huisgen,
R.; Scheer, W.; Ma¨der, H. Angew. Chem., Int. Ed. Engl. 1969, 8, 602.
(f) Grigg, R.; Kemp, J .; Sheldrick, G.; Trotter, J . J . Chem. Soc., Chem.
Commun. 1978, 109. (g) Grigg, R.; Kemp, J . Tetrahedron Lett. 1980,
21, 2461. (h) Vedejs, E.; West, F. G. Chem. Rev. 1986, 86, 941.
(39) Selected examples: (a) Katritzky, A. R.; Cui, X.-L.; Yang, B.;
Steel, P. J . J . Org. Chem. 1999, 64, 1979. (b) Chan, P. W. H.; Cottrell,
I. F.; Moloney, M. G. J . Chem. Soc., Perkin Trans. 1 2001, 2997. (c)
Chan, P. W. H.; Cottrell, I. F.; Moloney, M. G. J . Chem. Soc., Perkin
Trans. 1 2001, 3007. (d) Amat, M.; Llor, N.; Hidalgo, J .; Escolano, C.;
Bosch, J . J . Org. Chem. 2003, 68, 1919. (e) Harris, J . M.; Padwa, A. J .
Org. Chem. 2003, 68, 4371.

64 Organometallics, Vol. 23, No. 1, 2004
Li et al.
Ta ble 6. Va r ia tion of log KR w ith σI a n d σ+ for th e
[Ru (F 20-TP P )(CO)] (1) Ca ta lyzed Azir id in a tion of
P a r a -Su bstitu ted Im in es (p-XP h CHdNP h ) w ith
EDA
p-X
KX/KH
log(KX/KH)
σI
σ+
log KR(calcd)a
MeO
Me
H
0.588
1.034
0
-0.231
0.014
0
0.30
-0.01
0
-0.78
-0.31
0
-0.192
0.011
0
Cl
Br
NO2
0.627
0.532
0.315
-0.203
-0.274
-0.502
0.43
0.49
0.64
0.11
0.15
0.79
-0.291
-0.332
-0.501
a
log KR(calcd) ) -0.67σI - 0.01σ+.
Sch em e 3
F igu r e 9. Hammett correlation studies for the ruthenium-
mediated aziridination of para-substituted arylimines.
tion that involves the formation of the ylide intermedi-
ate 13 (Scheme 2). However, in contrast to the reaction
pathway proposed by J acobsen et al. involving imino
attack onto a carbene intermediate,13 we postulate the
generation of 13 to occur via substitution of EDA by the
imino nitrogen under the present conditions. Recall that
no aziridine products were detected from the reaction
of either (p-ClPh)CHdNPh or (p-MePh)CHdNPh with
a stoichiometric solution of [Ru(F20-TPP)(CHCO2Et)]
and when the Ru catalyst was removed from the
reaction conditions. While currently unclear, the role
of the ruthenium catalyst here seems to be in some
capacity other than that for facilitating carbenoid
formation. Furthermore, the triethyl pyrrolidine species
12 was isolated as a side product in all the Ru-catalyzed
imine aziridination reactions with EDA (Table 3). The
ylide is achiral. In the case of Cu catalysts, the ylide
may remain closely associated to the catalyst and allow
a limited degree of asymmetric induction to be achieved.13
However, this appears not the case in the present
ruthenium-catalyzed imine aziridination protocol. As
with the analogous Lewis acid catalyzed reactions,15,16
the ylide is thought to be weakly associated to the Ru
catalyst. This is supported by the marked influence of
different porphyrinato ring systems on reaction diaste-
reoselectivity, as shown in Tables 3 and 4. Presumably,
this systematic increase in stereoselectivity as the
electrophilicity of the Ru atom increases suggests the
effect of the spatial distance between the metal center
and the imino carbon on the extent of stereochemical
control exerted by the catalyst.
(by the least-squares method) the log KX/KH data in
Table 6 to the σI scale results in a linear correlation (R
) 0.96) with the F value calculated to be -0.69 ((0.1).
The Hammett σF correlation with a negative value for
F supports a mechanism where imines having electron-
donating substituents coordinated more efficiently to the
ruthenium atom than electron-withdrawing substituted
imines. Furthermore, the negative F value is indicative
of the electronic nature of the active ruthenium species.
The results of the correlation studies and the trapping
experiments suggest that a metal-bound ylide interme-
diate is generated upon addition of EDA to the ruthe-
nium(II) imine complex. The electronic nature of the
imine should have an influence on the cis:trans ratio of
the aziridines formed; however, the present results
indicate that there is no simple correlation between this
ratio and the electronic structure of the imine. Never-
theless, preferential cis product selectivity is thought
to arise from the metal-bound ylide intermediate favor-
ing to reside in the conformer 16 upon formation.
Intramolecular attack of the carbanion onto the imino
carbon atom resulting in ring closure is thought to give
the aziridine with the observed stereochemistry as
shown in Scheme 3.
A series of competition experiments were performed
to investigate the product ratios of the aziridines formed
by reaction of PhCHdNPh vs p-X-PhCHdNPh (X )
OMe, Me, Br, Cl, NO2) with EDA in the presence of 1
(imine:EDA:1 ) 100:100:1) as the catalyst. The ratios
of the corresponding aziridines were determined on the
1
basis of H NMR spectroscopy. The formation of these
aziridines was found to correlate with the Hammett σI
values as shown in Figure 9.
The Hammett plot in Figure 9 shows that, in general,
aziridines derived from imines substituted with an
electron-donating group formed much more quickly than
those with an electron-withdrawing substituent. Fitting
Con clu sion
In this article, we describe a (tetrakis(pentafluorophen-
yl)porphyrinato)ruthenium(II) complex of PhNdCH(p-

Ru(II) Porphyrin Catalyzed Imine Aziridination
Organometallics, Vol. 23, No. 1, 2004 65
J ) 8.7 Hz), 6.09 (t, 2H, J ) 7.8 Hz), 4,66 (d, 2H, J ) 8.6 Hz),
2.45 (d, 2H, J ) 7.9 Hz). 13C NMR (CDCl3) δ 176.70, 161.43,
148.08, 144.45, 143.82, 143.58, 140.48, 140.25, 139.31, 135.77,
132.11, 130.75, 127.86, 127.62, 127.06, 124.97, 116.34, 116.01,
115.03, 105.03. UV/vis (9.72 µM, CH2Cl2): λmax/nm (log ꢀ) 406
(5.36), 527 (4.20), 555 (sh, 3.48). IR (KBr, cm-1): 1967 (CO),
1011 (oxidation state marker band). MS (FAB): m/z 1319 [M]+,
1290 [M - CO]+, 1074 [M - C13H10ClN - CO]+. Anal. Calcd
for C58H18ClF20N5ORu: C, 52.88; H, 1.38; N, 5.32. Found: C,
52.39; H, 1.24; N, 5.65.
ClPh) prepared from the direct addition of [Ru(F20-TPP)-
(CO)] (1) to a C6H6 solution containing N-(p-chloroben-
zylene)aniline. The crystal structure of {Ru(F20-TPP)-
(CO)[PhNdCH(p-ClPh)]} (10) reveals the coordinated
imine ligand to be in a cis configuration. When treated
with EDA, complex 10 and other closely related imine
ligated ruthenium(II) porphyrins undergo aziridination
in moderate to good yields and cis selectivity. Our
studies suggest activation of the imine by the ruthenium
catalyst followed by nucleophilic substitution of the
imine to the diazo compound and subsequent cyclization
to give the aziridine. Product formation was shown to
occur more quickly for reactions derived from imines
with electron-donating substituents compared to electron-
withdrawing substituted imines.
Syn th esis of [Ru (F 20-TP P )(p y)2] (11).26 To a CH2Cl2
solution (5 mL) of the complex [Ru(F5-TPP)(CPhCO2Et)] (20
mg, 0.016 mmol) was added 1 drop of pyridine, and the mixture
was evaporated immediately. The residue was purified by
chromatography on a silica gel column using a 1:2 solution of
CH2Cl2 and n-hexane as eluent to give the desired product in
1
72% yield. H NMR (CDCl3): δ 8.08 (s, 8H), 6.07 (t, 2H, J )
7.4 Hz), 5.20 (t, 4H, J ) 7.0 Hz), 2.55 (d, 4H, J ) 5.3 Hz). 13C
NMR (CDCl3): δ 148.66, 147.18, 143.97, 143.28, 142.41,
139.14, 138.50, 135.15, 131.80, 131.38, 120.36, 115.32, 105.02.
UV/vis (CH2Cl2): λmax/nm (log ꢀ) 399 (5.24), 501 (4.13), 526
(4.16). IR (KBr, cm-1): 1011 (oxidation state marker band).
MS (FAB): m/z 1233 [M]+, 1154 [M - C5H5N]+, 1075 [M -
C5H5N - C5H5N]+. Anal. Calcd for C54H18F20N6Ru: C, 52.65;
H, 1.47; N, 6.82. Found: C, 52.93; H, 1.80; N, 6.57.
Exp er im en ta l Section
Gen er a l Con sid er a tion s. All (porphyrinato)ruthenium(II)
carbonyl complexes were prepared according to literature
methods.41 The imines were prepared from the corresponding
amines and aldehydes.42 The imines were recrystallized from
ethanol. EDA was purchased from Aldrich and used as
received. Molecular sieves (4 Å) were dried over 48 h at 350
°C and stored in a drybox prior to use. Benzene was dried over
sodium and benzophenone and distilled prior to use. UV-
visible spectra were recorded on a HP 8453 diode array
spectrophotometer. Infrared spectra were obtained on a BIO-
RAD FTS 165 spectrometer. Mass spectra were recorded on a
Gen er a l P r oced u r e for Ca ta lytic Cyclop r op a n a tion of
Im in es w ith EDA. A flask containing imine (2 mmol), catalyst
(0.005 mmol), and 4 Å molecular sieves was evacuated and
filled with Ar. C6H6 (10 mL) was added, and the mixture was
stirred for 10 min at room temperature. EDA (1 mmol, in 6
mL of benzene) was then added to the flask by syringe pump
over 18 h, and then the mixture was stirred for another 3 h.
After addition of bibenzyl (0.2 mmol), the reaction mixture was
filtered and eluted with CHCl3. The solution was evacuated
1
Finnigan MAT 95 mass spectrometer. H NMR and 13C NMR
spectra were obtained on a Bruker DPX-300 FT-NMR spec-
trometer; the chemical shifts (δ, ppm) are relative to tetra-
methylsilane (J values are given in Hz). Elemental analyses
were performed by the Institute of Chemistry, Chinese Acad-
emy of Sciences.
1
and analyzed by H NMR. The crude product was purified by
flash chromatography on silica gel using 2% EtOAc in n-
pentane as eluent to give the pure aziridine.16e,f
Syn th esis of [Ru (F 20-TP P )(CP h 2)] (7).26 To a CH2Cl2
solution (5 mL) of [Ru(F5-TPP)(CO)] (50 mg, 0.045 mmol) was
slowly added a CH2Cl2 solution (10 mL) containing diphenyl-
diazomethane (17.5 mg, 0.09 mmol) by syringe pump for 8 h
at room temperature. The resulting solution was further
stirred for 2 h and then evacuated under reduced pressure.
The residue was purified by chromatography on a silica gel
column using a CH2Cl2/n-hexane mixture (1:2 v/v) as eluent
to give the desired product in 95% yield. Crystals suitable for
X-ray structure determination were isolated from a solution
of CH2Cl2 and n-hexane. 1H NMR (CDCl3): δ 8.32 (s, 8H), 6.39
(t, 2H, J ) 7.4 Hz), 6.14 (t, 4H, J ) 7.7 Hz), 3.14 (d, 4H, J )
8.0 Hz). 13C NMR (CDCl3): δ 328.70 (RudC). 19F NMR
(CDCl3): δ -136.2 (d), -137.1 (d), -152.3 (t), -161.8 (m). UV/
vis (CH2Cl2): λmax/nm (log ꢀ) 385 (4.90), 425 (4.89), 526 (4.11),
550 (sh, 4.10), 613 (3.13). IR (KBr, cm-1): 1012 (oxidation state
marker band). MS (FAB): m/z 1239 [M]+. Anal. Calcd for
Eth yl cis-1-P h en yl-3-(p-br om op h en yl)a zir id in e-2-ca r -
boxyla te. H NMR (CDCl3): δ 7.46-7.49 (m, 2H), 7.38-7.41
1
(m, 2H), 7.25-7.30 (m, 2H), 7.02-7.05 (m, 5H), 4.01-4.07 (m,
2H), 3.53 (d, 1H, J ) 6.7 Hz), 3.20 (d, 1H, J ) 6.7 Hz), 1.05 (t,
3H, J ) 7.1 Hz). 13C NMR (CDCl3): δ 167.42, 152.04, 133.70,
131.24, 129.45, 129.27, 123.65, 121.94, 119.89, 61.22, 46.52,
45.54, 14.02. HRMS (EI): m/z calcd for C17H16BrNO2 345.0364,
found 345.0345.
E t h yl tr a n s-1-P h en yl-3-(p-b r om op h en yl)a zir id in e-2-
1
ca r boxyla te. H NMR (CDCl3): δ 7.43-7.48 (m, 2H), 7.18-
7.25 (m, 5H), 6.96-7.01 (m, 1H), 6.84-6.87 (m, 2H), 4.07-
4.15 (m, 2H), 3.76 (d, 1H, J ) 2.4 Hz), 3.18 (d, 1H, J ) 2.4
Hz), 1.15 (t, 3H, J ) 7.1 Hz). 13C NMR (CDCl3): δ 167.27,
148.17, 135.39, 131.65, 128.95, 128.44, 123.00, 122.02, 119.86,
61.48, 45.93, 45.62, 14.05. HRMS (EI): m/z calcd for C17H16
-
BrNO2 345.0364, found 345.0335.
E t h yl cis-1-P h en yl-3-(p -ter t-b u t ylp h en yl)a zir id in e-2-
ca r boxyla te. 1H NMR (CDCl3): δ 7.44 (d, 2H, J ) 8.3 Hz),
7.36 (d, 2H, J ) 8.5 Hz), 7.27-7.25 (q, 2H), 7.07-7.04 (m, 3H),
4.10-3.95 (m, 2H), 3.57 (d, 1H, J ) 6.8 Hz), 3.18 (d, 1H, J )
6.8 Hz), 1.32 (s, 9H), 0.95 (t, 3H, J ) 7.1 Hz). 13C NMR
(CDCl3): δ 167.77, 151.56, 143.96, 129.42, 129.27, 126.31,
125.10, 118.31, 113.13, 61.42, 46.00, 45.67, 31.43, 31.18, 14.30.
HRMS (EI): m/z calcd for C21H25NO2 323.1885, found 323.1877.
Eth yl tr a n s-1-P h en yl-3-(p-ter t-bu tylp h en yl)a zir id in e-
C
57H18F20N4Ru: C, 55.21; H, 1.45; N, 4.52. Found: C, 55.77;
H, 1.92; N, 4.40.
Syn t h esis of {R u (F 20-TP P )(CO)[P h NdCH (p -ClP h )]}
(10).26 To a flask containing C6H6 (50 mL) was added [Ru(F20
-
TPP)(CO)] (1; 0.05 mmol) and N-(4-chlorobenzylidene)aniline
(0.06 mmol). The mixture was stirred for 30 min and then
evacuated to give the product in 80% yield. Crystals suitable
for X-ray determination were isolated from a solution of CH2-
1
Cl2 and n-hexane at room temperature. H NMR (CDCl3): δ
1
2-ca r boxyla te. H NMR (CDCl3): δ 7.36 (d, J ) 8.4 Hz, 2H),
8.73 (s, 1H), 8.65 (s, 8H), 6.43 (t, 1H, J ) 7.3 Hz), 6.35 (d, 2H,
7.26-7.19 (m, 4H), 6.99-6.95 (m, 1H), 6.89-6.87 (q, 2H),
4.14-4.08 (q, 2H), 3.78 (d, 1H, J ) 2.5 Hz), 3.22 (d, 1H, J )
2.5 Hz), 1.31 (s, 9H), 1.15 (t, 3H, J ) 7.1 Hz). 13C NMR
(CDCl3): δ 167.78, 151.27, 148.71, 133.37, 128.96, 126.57,
125.59, 122.79, 120.06, 61.39, 46.38, 45.99, 34.70, 31.41, 14.16.
HRMS (EI): m/z calcd for C21H25NO2 323.1885, found 323.1879.
5-(4-ter t-Bu t ylp h en yl)-1-p h en ylp yr r olid in e-2,3,4-t r i-
ca r boxylic Acid Tr ieth yl Ester . 1H NMR (CDCl3): δ 7.22-
(41) (a) Adler, A. D.; Longo, F. R.; Finarelli, J . D.; Goldmacher, J .;
Assour, J .; Korsakoff, L. J . Org. Chem. 1967, 32, 476. (b) Rillema, D.
P.; Nagle, J . K.; Barringer, L. F., J r.; Meyer, T. J . J . Am. Chem. Soc.
1981, 103, 56. (c) Li, Z.-Y.; Huang, J .-S.; Che, C.-M.; Chang, C.-K. Inorg.
Chem. 1992, 31, 2670. (d) Falvo, R. E.; Mink, L. M. J . Chem. Educ.
1999, 76, 237.
(42) Biglow, L. A.; Eatough, H. Organic Syntheses; Wiley: New York,
1932; Collect. Vol. 1, p 73.

66 Organometallics, Vol. 23, No. 1, 2004
Li et al.
7.17 (m, 2H), 7.11-7.01 (m, 4H), 6.67 (t, 1H, J ) 7.3 Hz), 6.59
(d, 2H, J ) 7.8 Hz), 5.41 (d, 1H, J ) 7.9 Hz), 5.35 (d, 1H, J )
6.6 Hz), 4.19-4.14 (m, 2H), 4.08-4.03 (q, 2H, J ) 14.3, 7.1
Hz), 3.75-3.67 (m, 2H), 3.62 (t, 1H, J ) 7.6 Hz), 3.51-3.43
(m, 1H), 1.24 (s, 9H), 1.22 (t, 3H, J ) 7.6 Hz), 1.08 (t, 3H, J )
7.1 Hz), 0.74 (t, 3H, J ) 7.2 Hz). 13C NMR (CDCl3): δ 173.93,
170.75, 169.99, 150.54, 145.10, 134.22, 128.40, 126.83, 125.21,
117.44, 114.26, 65.74, 65.63, 61.40, 61.23, 60.58, 53.04, 49.71,
34.54, 31.44, 31.41, 31.28, 14.15, 14.08, 13.63. HRMS (EI): m/z
calcd for C29H37NO6 495.2021, found 495.2630.
1-(4-Meth oxyp h en yl)-5-p h en ylp yr r olid in e-2,3,4-tr ica r -
boxylic Acid Tr ieth yl Ester . 1H NMR (CDCl3): δ 7.38-7.19
(m, 5H), 6.66 (d, 2H, J ) 9.1 Hz), 6.51 (d, 2H, J ) 9.1 Hz),
5.27 (d, 1H, J ) 4.9 Hz), 5.22 (d, 1H, J ) 2.5 Hz), 4.23-4.04
(m, 6H), 3.80-3.77 (q, 1H, J ) 3.7, 2.3 Hz), 3.66 (s, 3H), 3.54-
3.51 (q, 1H, J ) 4.7, 4.0 Hz), 1.30 (t, 3H, J ) 7.1 Hz), 1.17-
1.11 (m, 6H). 13C NMR (CDCl3): δ 172.41, 171.72, 171.24,
152.56, 142.24, 139.40, 128.76, 127.42, 126.35, 116.91, 114.43,
65.97, 65.24, 61.74, 61.54, 61.24, 55.71, 55.57, 48.75, 14.27,
14.16, 14.08. HRMS (EI): m/z calcd for C26H31NO7 469.2100,
found 469.2095.
Gen er a l P r oced u r e for th e P r ep a r a tion of P yr r o-
lid in es Ca ta lyzed by [Ru (F 20-TP P )(CO)] (1). A flask con-
taining the imine (1.2 mmol), dipolarophile A-B (1.2 mmol),
catalyst 1 (0.005 mmol), and 4 Å molecular sieves was
evacuated and filled with Ar. C6H6 (10 mL) was added, and
the mixture was stirred for 10 min at room temperature. A
solution of EDA (1 mmol) dissolved in C6H6 (6 mL) was then
added to the flask by syringe pump over 12 h, and the mixture
was stirred for a further 1 h. The reaction mixture was filtered
and eluted with CHCl3. The solution was evacuated and
analyzed by 1H NMR. The crude product was purified by flash
chromatography on silica gel using 10% EtOAc in n-pentane
as eluent to give the pure pyrrolidine.
5-(4-Ch lor op h en yl)-1-p h en ylp yr r olid in e-2,3,4-t r ica r -
boxylic Acid 2-Eth yl Ester 3,4-Dim eth yl Ester (14a ).
Purification by flash column chromatography gave the title
compound in 90% yield as a 1.3:1 mixture of diastereomers.
Major stereoisomer: 1H NMR (CDCl3) δ 7.27-7.23 (m 4H),
7.11-7.07 (q, 2H), 6.71 (t, 1H, J ) 7.3 Hz), 6.49 (d, 2H, J )
7.9 Hz), 5.35 (d, 1H, J ) 4.1 Hz), 5.28 (d, 1H, J ) 2.0 Hz),
4.15-4.02 (m, 2H), 3.83 (t, 1H, J ) 2.5 Hz), 3.78 (s, 3H), 3.65
(s, 3H), 3.54 (t, 1H, J ) 3.5 Hz), 1.13 (t, 3H, J ) 7.1 Hz); 13C
NMR (CDCl3) δ 171.99, 171.79, 171.45, 144.98, 140.74, 133.13,
129.03, 128.06, 126.90, 118.80, 115.37, 65.10, 64.59, 64.40,
61.50, 55.23, 52.94, 48.40, 14.11; HRMS (EI) m/z calcd for
118.29, 113.89, 71.02, 69.73, 61.79, 52.61, 52.34, 14.05; HRMS
(EI) m/z calcd for C23H23NO6 409.1525, found 409.1518.
5-(4-ter t-Bu tylph en yl)-1-ph en yl-2,5-dih ydr o-1H-pyr r ole-
2,3,4-tr ica r boxylic Acid 2-Eth yl Ester 3,4-Dim eth yl Ester
(14c). Purification by flash column chromatography gave the
title compound in 83% yield. 1H NMR (CDCl3): δ 7.30-7.22
(m, 4H), 7.12-7.08 (m, 2H), 6.69 (t, 1H, J ) 7.3 Hz), 6.55 (d,
2H, J ) 7.9 Hz), 5.99 (d, 1H, J ) 6.9 Hz), 5.75 (d, 1H, J ) 6.9
Hz), 4.20-4.08 (m, 2H), 3.82 (s, 3H), 3.63 (s, 3H), 1.26 (s, 9H),
1.10 (t, 3H, J ) 7.1 Hz). 13C NMR (CDCl3): δ 169.69, 162.98,
162.33, 151.23, 144.07, 143.58, 134.74, 130.59, 129.00, 126.84,
125.76, 118.11, 113.87, 70.65, 69.73, 61.75, 52.57, 52.30, 34.53,
31.27, 14.04. HRMS (EI): m/z calcd for C27H31NO6 465.2151,
found 465.2150.
1-P h en yl-5-(3,4,5-t r im et h oxyp h en yl)-2,5-d ih yd r o-1H -
p yr r ole-2,3,4-t r ica r b oxylic Acid 2-E t h yl E st er 3,4-Di-
m eth yl Ester (14d ). Purification by flash column chroma-
tography gave the title compound in 80% yield. 1H NMR
(CDCl3): δ 7.14-7.10 (m, 2H), 6.73 (t, 1H, J ) 7.4 Hz), 6.58
(d, 2H, J ) 8.0), 6.53 (s, 2H), 5.94 (d, 1H, J ) 6.8 Hz), 5.76 (d,
1H, J ) 6.8 Hz), 4.19-4.06 (m, 2H), 3.83 (s, 3H), 3.80 (s, 3H),
3.79 (s, 6H), 3.67 (s, 3H), 1.08 (t, 3H, J ) 7.1 Hz). 13C NMR
(CDCl3): δ 169.70, 163.21, 162.24, 153.70, 144.55, 143.78,
137.98, 133.48, 130.29, 129.13, 118.65, 114.16, 104.18, 71.40,
69.82, 61.84, 60.90, 56.27, 52.70, 52.49, 14.12. HRMS (EI): m/z
calcd for C26H29NO9 499.1842, found 499.1831.
4,6-Dioxo-2,3,5-t r ip h en yloct a h yd r op yr r olo[3,4-c]p yr -
r ole-1-ca r boxylic Acid Eth yl Ester (14e). Purification by
flash column chromatography gave the title compound in 86%
1
yield. H NMR (CDCl3): δ 7.50-7.23 (m, 10H), 7.14-7.08 (q,
2H, J ) 8.9, 7.6 Hz), 6.77 (t, 1H, J ) 7.3 Hz), 6.68 (d, 2H, J )
7.6 Hz), 5.53 (t, 1H, J ) 3.3 Hz), 5.28 (d, 1H, J ) 9.9 Hz),
4.13-4.03 (m, 3H), 3.61-3.56 (q, 1H, J ) 13.6, 4.0 Hz), 1.04
(t, 3H, J ) 6.9 Hz). 13C NMR (CDCl3): δ 175.68, 174.06, 170.98,
144.57, 141.56, 131.73, 129.23, 129.15, 128.97, 128.87, 127.72,
126.53, 126.10, 119,97, 117.01, 65.42, 64.97, 61.75, 60.41,
54.54, 46.21, 13.90. HRMS (EI): m/z calcd for C27H24N2O4
440.1736, found 440.1734.
P r oced u r e for Azir id in a t ion Com p et it ion E xp er i-
m en ts. A flask containing the imines PhCHdNPh (0.3 mmol)
and p-X-PhCHdNPh (X ) OMe, Me, Br, Cl, NO2; 0.3 mmol),
[Ru(F20-TPP)(CO)] (0.003 mmol), and 4 Å molecular sieves was
evacuated and filled with Ar(g). The mixture was diluted with
C6H6 (10 mL) and stirred for 10 min at room temperature. EDA
(0.3 mmol, in 10 mL of C6H6) was then added to the flask by
syringe pump over 18 h. The reaction mixture was filtered,
and the 4 Å molecular sieves were eluted with CHCl3. The
solution was evacuated, and the resultant mixture was used
C
23H24ClNO6 445.1292, found 445.1288. Minor stereoisomer:
1H NMR (CDCl3) δ 7.25 (d, 2H, J ) 6.9 Hz), 7.16 (d, 2H, J )
8.5 Hz), 7.10 (t, 2H, J ) 7.4 Hz), 6.71 (t, 1H, J ) 7.3 Hz), 6.43
(d, 2H, J ) 8.0 Hz), 5.29 (d, 1H, J ) 9.5 Hz), 5.00 (d, 1H, J )
8.1 Hz), 4.25 (dd, 1H, J ) 12.6, 9.6 Hz), 4.18-4.07 (m, 2H),
4.01 (dd, 1H, J ) 12.6, 8.0 Hz), 3.75 (s, 3H), 3.40 (s, 3H), 1.20
(t, 3H, J ) 7.1 Hz); 13C NMR (CDCl3) δ 170.89, 169.68, 169.59,
144.06, 137.46, 133.87, 129.19, 128.80, 128.34, 118.34, 113.45,
63.20, 62.57, 61.64, 52.52, 51.88, 49.84, 46.20, 14.14; HRMS
(EI) m/z calcd. for C23H24ClNO6 445.1290, found 445.1290.
1,5-Dip h en yl-4,5-d ih yd r o-1H-p yr r ole-2,3,4-tr ica r boxy-
lic Acid 2-Eth yl Ester 3,4-Dim eth yl Ester (14b). Purifica-
tion by flash column chromatography gave the title compound
in 92% yield. 1H NMR (CDCl3): δ 7.35-7.22 (m, 5H), 7.11-
7.06 (q, 2H, J ) 8.6, 7.2 Hz), 6.68 (t, 1H, J ) 7.2 Hz), 6.54 (d,
2H, J ) 7.9 Hz), 6.01 (d, 1H, J ) 6.9 Hz), 5.76 (d, 1H, J ) 6.9
Hz), 4.22-4.07 (m, 2H), 3.83 (s, 3H), 3.63 (s, 3H), 1.11 (t, 3H,
J ) 7.3 Hz). 13C NMR (CDCl3): δ 169.61, 162.92, 162.27,
143.94, 143.45, 137.95, 130.88, 129.03, 128.87, 128.41, 127.30,
1
to determine aziridine product ratios by H NMR analysis.
Ack n ow led gm en t. This work was supported by the
Area of Excellence Scheme (AoE/P-10-01) established
under the University Grants Council (HKSAR), the
Hong Kong Research Grants Council (No.7099/00P), and
the University of Hong Kong (Generic Drugs Research
Program).
Su p p or tin g In for m a tion Ava ila ble: Text giving detailed
experimental procedures and characterization data for [Ru-
(F20-TPP)(CHCO2Et)] and tables giving X-ray crystallographic
data. This material is available free of charge via the Internet
at http://pubs.acs.org.
OM034128B