2042
J . Org. Chem. 1998, 63, 2042-2044
not be derivatized. This means catalysts made from
Bis-F a ced Am in op or p h yr in Tem p la tes for
these new templates always have at least one unencum-
bered approach which can serve as a chiral substrate
passage to the metal center. We are currently working
on strategies to add a variety of chiral substituents to
these porphyrin templates.
th e Syn th esis of Ch ir a l Ca ta lysts a n d
Hem ep r otein An a logu es
Eric Rose,*,† Miche`le Soleilhavoup,
Lorraine Christ-Tommasino, and Gilles Moreau
Recently, we reported the synthesis of 5,10,15,20-
tetrakis(2′,6′-diamino-4′-tert-butylphenyl)porphyrin 1b.2
This octaaminoporphyrin, which, thanks to p-tert-butyl
substituents, is slightly soluble in CH2Cl2, was obtained
by mixing pyrrole and 2,6-dinitro-4-tert-butylbenzalde-
hyde in the presence of BF3‚OEt2 followed by oxidation
of the porphyrinogen with tetrachlorobenzoquinone.
In the present paper, we report the extension of this
work to the synthesis of hexaaminoporphyrins 5c and
5d , tetraaminoporphyrins 7c and 7d , and diaminopor-
phyrin 8d (see Figure 2). These porphyrins were ob-
tained via condensation of pyrrole and a mixture of 2′,6′-
dinitro-4′-tert-butylbenzaldehyde and an unfunctionalized
benzaldehyde in the presence of BF3‚OEt2,4 followed by
reduction5 of the two, four, or six nitro groups to amines.
Incorporation of an unfunctionalized benzaldehyde
gives rise to a “blank” meso-phenyl picket. Two different
blank pickets have been used: porphyrin 5c was made
by incorporating a single 4-tert-butyl phenyl “blank”
picket into the macrocycle (eq a, Scheme 1) while one,
two, and three pentafluorophenyl groups were incorpo-
rated into porphyrins 5d , 7d , and 8d , respectively (eq b
and Figure 2). Interestingly, the condensation reaction
showed a strong preference for cis over trans arrange-
ment of two dinitrobenzaldehyde moieties: with either
“blank” picket, geometry 7 was a major product, while
geometry 6 was barely observed. These results under-
score the steric demands of o-dinitro substitution on the
porphyrin meso-phenyl groups and help explain the low
yields observed in the condensation reaction that gives
rise to the parent octanitro compound (1a ). The structure
of these compounds was confirmed by the equivalence
Laboratoire de Synthe`se Organique et Organome´tallique,
UMR CNRS 7611, Tour 44, 4, Place J ussieu, 75252 Paris
Cedex 05, France
J ames P. Collman,*,‡ Me´lanie Quelquejeu, and
Andrei Straumanis
Stanford University, Department of Chemistry, Stanford,
California 94305
Received October 10, 1997
Tetraarylporphyrins with differently substituted aryl
groups attached at the meso positions have, in the past,
been obtained through the condensation of pyrrole with
a mixture of two different benzaldehydes.1 We are
interested in making meso-(2,6-diaminophenyl)porphy-
rins that are useful in the synthesis of porphyrin com-
plexes with superstructure functionality on both faces.
Our preliminary epoxidation studies using the metalated
Mosher’s amide derivative (1c, Figure 1)2 of the parent
octaaminoporphyrin (1b) failed for the moment to pro-
duce good enantiomeric excesses and a good turnover
number. We believe this catalyst with eight Mosher’s
pickets is too bulky to perform efficient or selective
epoxidation. The results reported here provide evidence
that placing fewer chiral groups on each face of a
porphyrin can generate a more active and more selective
metal center. These results are in keeping with those of
J acobsen et al. which indicate that efficient chiral induc-
tion can be achieved with one very modest chiral di-
amine.3 The sterics of the remaining chiral passage must
be tuned so as to maximize both ∆∆G and overall
epoxidation. J ust enough chiral bulk must be present
to destabilize exactly one enantioapproach. It is our
belief that the failure of many enantioselective catalysts
stems from restriction of both enantioapproaches to the
metal center.
1
and the nonequivalence of the â-pyrrolic protons6 by H
NMR, which gave insight into the symmetry of the
molecules.
Reaction of 5d , 7d , and 8d with Mosher’s acid chloride
gave chiral porphyrins 5f, 7f, and 8f. The latter two were
directly metalated using excess FeBr2 to give 7f ′ and 8f ′
(Scheme 2). However, as with 1c2, metalation of free
base hexa-Mosher’s amide porphyrin 5f could not be
accomplished using the standard FeBr2 method. Instead,
iron(III) hexaamino porphyrin (5d ′) was made first
(Scheme 2), and this was condensed with Mosher’s acid
chloride to give 5f ′ (Figure 3).
Our new family of aminoporphyrins provides templates
for making less hindered catalysts. The “blank” picket
(the p-tert-butyl or pentafluoro-meso-phenyl group) can-
† E-mail: rose@ccr.jussieu.fr
‡ E-mail: jpc@chem.stanford.edu
Catalytic expoxidations of styrene were carried out
using these three iron porphyrins (5f ′, 7f ′, and 8f ′) as
catalysts. An interesting trend emerged. The most bulky
analogue, 5f ′, gave the lowest selectivities for the epoxi-
dation of styrene (<1% ee), while the least bulky ana-
(1) (a) Kim, J . B.; Leonard, J . J .; Longo, F. R. J . Am. Chem. Soc.
1972, 94, 3986. (b) Little, R. G.; Anton, J . A.; Loach, P. A.; Ibers, J . A.
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(4) (a) Lindsey, J . S.; Schreiman, I. C.; Hou, H. C.; Kearney P. C.;
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Wagner, R. W. J . Org. Chem. 1989, 54, 828.
(5) Lecas-Nawrocka, A.; Boitrel, B.; Rose, E. Bull. Soc. Chim. Fr.
1991, 128, 407.
(6) (a) Meng, G. G.; J ames, B. R.; Skov, K. A. Can. J . Chem. 1994,
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(2) Rose, E.; Kossanyi, A.; Quelquejeu, M.; Soleilhavoup, M.; Du-
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Published on Web 03/03/1998