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The porphyrin handbook - Kadish K.M.

Kadish K.M. The porphyrin handbook - Academic press, 2000. - 368 p.
Download (direct link): kadishsmishgulilard2000.djvu
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Groves et al. from the TPP-type porphyrin and a chiral binaphthyl
derivative.53
Recent work has improved enantiomeric excess of epoxida-tion reaction by
use of metalloporphyrins having two chiral naphthyl groups, one above and
one below the porphyrin plane.54 This asymmetric reaction seems to arise
from chiral interaction between the chiral element of the catalyst and
the achiral substrate in the transition state. Doubly strapped chiral
porphyrins 17 are obtainable from the coupling of
a,/?,a,/?-tetrakis-(2-aminopheny])porphyrin and amino-acid derivative.55
Chiral space above and below the porphyrin plane results in moderately
enantio-selective epoxidation. Since then, various kinds of chiral
porphyrins have been synthesized as catalysts for the oxygenation of
organic substrates.
A similar type of chiral rhodium porphyrin was found to be effective
for the carbene-insertion reaction to olefins, where formation of the
carbene complex takes place. Chiral rhodium complexes for catalytic
stereoselective-carbene addition to olefins were prepared by condensation
of a chiral aldehyde and pyrrole. Formation of the metal-carbene complex
and substrate access to the catalytic center are crucial to the
production of optically active cyclopropane derivatives.56 Optically
active a-methoxy-a-(trifluoro-methyDphenylacetyl groups are linked with
the amino groups of ,, isomers of tetrakis-(2-aminophenyl)por-phyrin
through amide bonds. Oxidation reactions of the
R* =
16
Bzl
- CHNHCO-^ - CONHCH-
Bzl
CO'
286
Ogoshi et al.
racemic benzyl(methyl)(phenyl)phosphine lead to the formation of
optically active phosphine oxide ( 41%) and proceed with retention of
the configuration of the phosphorus atom. It is suggested that chiral
recognition of catalyst to substrate is operative in asymmetric
oxidation.57
Metal complexes of dimers linked with flexible spacers give rise to
polymeric complexes at a higher concentration of diamine. Two
metalloporphyrins with C2 symmetry linked with a rigid chiral amine
spacer (Troger's base) show diastereomeric recognition for optically
active, basic amino acids.58-59 Chiral diamine derivatives such as basic
amino-acid esters are tightly bound with moderate enantioselec-tivity to
the zinc porphyrin "tweezers" in the inner-homochiral cavity of the host
(Figure 7). It is noted that
the histidine-methyl ester shows higher enantioselective recognition. A
bis-metalloporphyrin linked with a chiral binaphthyl group shows similar
strong binding with the a,a>-diaminoalkanes in the chiral molecular cleft
at the zinc ions.fi0
2. Intrinsic Chiral Porphyrins and Metalloporphyrins
Ogoshi and coworkers have developed a new strategy for synthesis of a
chiral porphyrin, in which an achiral porphyrin is modified to have C2
symmetry (an intrinsic chiral porphyrin) by introducing achiral
substituents. In Figure 8 the C2 symmetric intrinsic chiral porphyrins
are shown.61-62 A series of chiral porphyrins were prepared in
Bu1
Bu'
-L = Diamines
18
19
Figure 7. Extrinsic chiral porphyrin dimers.
23 24
Figure 8. Intrinsic chiral porphyrins.

46/Porphyrins and Metalloporphyrins as Receptor Models
which the interaction free energy can be separated into contributions
from recognition pairing. These hosts 23,24 were designed as receptors
for amino-acid esters. Host 23 has three recognition groups: a zinc ion,
a hydroxy group and a carbomethoxy group.17 These porphyrins were
prepared by the coupling of two dipyrromethanes. Host ( + )-23 was
designed to bind amino-acid derivatives ihusly: (I) the zinc ion binds
the amino group of the guesl through coordination interaction; (2) the
hydroxy group binds the carbonyl group of the guest through a hydrogen-
bonding interaction; and (3) the carbomethoxy group interacts favorably
or unfavorably with the side-chain group of the guest.
The zinc complex of a chiral double-strapped porphyrin with Ci
symmetry 24 was obtained from coupling of 2,2,/j,/j-tetrakis(2-
ammophenyl)porphyrin and 3-nitro-phenyl-2,5-dicarbonyl chloride/'' Three
different interactions-coordination of the amino group to the zinc,
hydrogen bonding of ester carbonyl, and steric hindrance between the
side-chain group of amino-acid ester and the strapping group of 24-are
operating in diastereomeric recognition of the chial porphyrin. It was
noted that hydrogen bonding between the amido proton and ester carbonyl
in the strapped cavity was effectively determined by the asymmetrically
substituted nitro group at the phenyl.
Strapped N-alkylporphyrin zinc complexes were prepared for molecular
recognition of the carboxylate anions of N-protected amino-acid
carboxylate anion. Highly enantio-selective binding of substrates was
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