D2-symmetric chiroporphyrins derived from (1R)-cis-hemicaronaldehydic acid: Preparation and spectral characterization

Article abstract of DOI:10.1002/(sici)1099-0690(200002)2000:4<583::aid-ejoc583>3.0.co;2-e

Esters, N,N-disubstituted amides, and a N-acylurea derived from the enantiopure industrial intermediate (1R)-cis-hemicaronaldehydic acid (or biocartol) are convenient synthons for the preparation of a series of chiroporphyrins by condensation with pyrrole

Full text of DOI:10.1002/(sici)1099-0690(200002)2000:4<583::aid-ejoc583>3.0.co;2-e

FULL PAPER
D2-Symmetric Chiroporphyrins Derived from (1R)-cis-Hemicaronaldehydic
Acid: Preparation and Spectral Characterization
[a]
[a]
[a]
[a]
´
´
Celine Perollier, Marinella Mazzanti, Jean-Pierre Simonato, Franck Launay,
[a]
[a]
´
Rene Ramasseul, and Jean-Claude Marchon*
Keywords: Porphyrins / Chiral auxiliaries / Macrocycles / Pyrethroids
Esters, N,N-disubstituted amides, and a N-acylurea derived
from the enantiopure industrial intermediate (1R)-cis-hem- mono-N-substituted amide groups. 1H-NMR spectroscopy in-
icaronaldehydic acid (or biocartol) are convenient synthons dicates that the ester, amide, and urea stereogenic groups sit
lysis of the urea substituents affords a chiroporphyrin with
for the preparation of a series of chiroporphyrins by con- on the porphyrin close to the metal binding site and restrict
densation with pyrrole. These chiral meso-tetracyclopro- substrate or ligand access along a C2-symmetric groove. This
pylporphyrins are obtained exclusively as the D2-symmetric
α,β,α,β atropisomer, generally in low to moderate yields (2–
structural feature of chiroporphyrins and of their metal com-
plexes is of high potential interest in asymmetric catalysis
20%), and in the urea case in excellent yield (60%). Hydro- and chiral recognition.
Introduction
ronaldehydic acid, an enantiomerically pure cyclopropylal-
dehyde (also known under the name biocartol) which is an
intermediate in the Roussel–Uclaf process for the produc-
tion of pyrethroid insecticides.[7] Our investigations have re-
vealed that biocartol methyl ester can be condensed with
pyrrole to afford a prototypic chiral porphyrin which is ob-
tained exclusively as the α,β,α,β atropisomer, and that we
have called tetramethylchiroporphyrin.[8] We describe here
the preparation and characterization of a series of D2-sym-
metric analogs, or chiroporphyrins, derived from various
other esters and amides of biocartol, and from an urea de-
rivative. Metal complexes of these chiroporphyrins have
been shown to be useful as catalysts in enantioselective
epoxidation and aziridination,[6,9] as hosts in chiral recogni-
tion of alcohols and β-amino alcohols,[10,11] and as chiral
NMR shift reagent for amines.[12]
During the last decade extensive work has been devoted
to the development of efficient catalytic methods for the
enantioselective epoxidation of non functionalized alkenes.
Apart from recent work on dioxirane-mediated epoxid-
ation,[1,2] most studies deal with chiral transition metal
complexes as catalysts, especially metalloporphyrins[3] and
metallosalens.[4] The latter catalysts provide excellent en-
antiomeric excesses (ee) in enantioselective epoxidation of
substituted aromatic alkenes, and they are considered for
industrial applications. However their turnover numbers are
low due to the oxidative degradation of the salen ligands.
Thus, chiral metalloporphyrins remain good candidates as
catalysts for enantioselective epoxidation due to their
stability towards oxidation, as illustrated by some recent pa-
pers.[5,6]
When we started our own investigations, most of the por-
phyrin complexes designed as epoxidation catalysts were de-
rived from the meso-tetraphenylporphyrin moiety by at-
taching elaborated chiral substituents on ortho position on
the phenyl groups before or after porphyrin ring formation.
This type of construction necessarily places the potentially
stereogenic elements at a distance from the reactive metal
center. Inasmuch as close proximity of these groups is be-
lieved to be beneficial to the asymmetric induction, we have
looked for alternative synthetic strategies using easily avail-
able chiral aldehydes of natural or industrial origin as syn-
thons. Our goal was to find an aldehyde synthon which
could place chiral groups near the center of the porphyrin
ring, and at the same time provide substituent flexibility.
These requirements have been fulfilled by (1R)-cis-hemica-
Results and Discussion
Syntheses of Chiroporphyrins 2a–l
The chiral synthons 1a–k were synthesized in three steps
starting from biocartol.[13,14] The (1R,3S) configuration of
biocartol is retained in esters and amides 1a–k and no epi-
merization was seen by NMR. Urea 1l was obtained by
condensation of biocartol with N,N’-dicyclohexylcarbodii-
mide (DCC) in DMF in the presence of triethylamine.[15]
An alternative one-step preparation of the methyl ester 1a
by methylation of the sodium salt of biocartol was also
worked out,[16] and it is described in the Experimental Sec-
tion.
The chiroporphyrins were prepared using the classical
Lindsey conditions[17] for the synthesis of meso-tetraal-
kylporphyrins, i.e. condensation of pyrrole (1 equiv.) with
the chiral aldehyde 1a–l (1 equiv.) in dichloromethane in the
presence of trifluoroacetic acid (TFA, 1 equiv.), followed by
in situ oxidation of the intermediate porphyrinogen by 2,3-
[a]
Laboratoire de Chimie de Coordination
Service de Chimie Inorganique et Biologique
´
`
Departement de Recherche Fondamentale sur la Matiere
´
Condensee, CEA-Grenoble,
38054 Grenoble, France
E-mail: jemarchon@cca.fr
Eur. J. Org. Chem. 2000, 583Ϫ589
WILEY-VCH Verlag GmbH, D-69451 Weinheim, 2000
1434Ϫ193X/00/0204Ϫ0583 $ 17.50ϩ.50/0
583

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C. Perollier, M. Mazzanti, J.-P. Simonato, F. Launay, R. Ramasseul, J.-C. Marchon
FULL PAPER
then with water leads to the corresponding N-cyclohexyla-
cylamides RCONHC6H11.[18] This reaction applied to 2l af-
forded the tetra-N-cyclohexylchiroporphyrin 2m in 60%
yield (Scheme 2).
Scheme 1. One-pot, two-step synthesis of chiroporphyrins 2a–l
Scheme 2. Access to chiroporphyrin 2m with mono-N-substituted
amide groups
dichloro-5,6-dicyano-1,4-benzoquinone (Scheme 1). Lind-
sey et al.[17] reported a beneficial effect of dilution and a
26% yield of meso-tetrapentylporphyrin with a 10–3  con-
centration of the reactants. Nevertheless in their general
procedure for meso-tetraalkylporphyrins, they recom-
mended a 10–2  concentration for convenience. Following
their experimental conditions we obtained porphyrins 2a–l
in yields varying from from 2% for 2b to 60% for 2l. The
lower yields were obtained for alcohol esters of biocartol.
Tetramethylchiroporphyrin 2a[8] (also called H2TMCP) and
its metal complexes were needed in large amounts to screen
their potential in enantiocontrol,[6,9–12] so its yield was
optimized to 20% using a 10–3  concentration of reactants
and a longer reaction time for porphyrinogen formation.
Chiroporphyrin 2l was obtained in a surprisingly excellent
yield (60%), which has been accounted for by the presence
of complementary intramolecular hydrogen-bonding inter-
actions between N-acylurea substituents which direct the
cyclisation of the tetrapyrrolic intermediate.[15]
α,β,α,β Conformation of Porphyrins 2a–m
Each of the synthons 1a–l affords only one porphyrin
product, as indicated by the presence of a single spot in
TLC (Soret band near 430 nm) and highly symmetric
1
NMR signatures (vide infra).[19] The H-NMR spectra of
porphyrins 2a–m at room temperature show two singlets
in the 9 ppm region for the β pyrrolic protons; likewise,
their 13C spectra show two pairs of peaks for Cα and Cβ
(Figure 1 and Figure 2). This indicates that the meso
groups are not freely rotating at room temperature and
that each of the chiroporphyrins 2a–m is present as the
D2-symmetric α,β,α,β atropisomer (Scheme 3). The cis
configuration of the starting chiral synthons 1a–l is re-
tained in the chiroporphyrins, as indicated by the charac-
teristic NMR signature of protons H1 and H2 as two
doublets at ca. 2.7 and ca. 4.8 ppm with a coupling con-
stant Jcis ϭ 8.8 Hz; this value would be Jtrans ϭ 5.6 Hz for
the trans configuration.[20]
Our experience with ortho-substituted tetraphenylpor-
phyrins had led us to anticipate that all four atropisomers
would form in the synthesis of a given chiroporphyrin, and
Preparation of Porphyrin 2m
Chiroporphyrins 2j and 2k possess N,N-disubstituted that tedious chromatographic separation of the desired
meso substituents derived from disubstituted biocartol α,β,α,β would be required. Thus the finding that a single
amides 1j and 1k. As we have reported earlier, access to α,β,α,β atropisomer product is formed for each of the com-
chiroporphyrins from N-monosubstituted biocartol amides pounds 2a–m was indeed a very pleasant surprise. Among
by the Lindsey method is prevented since the latter exist in several possible determinants which may contribute to the
a cyclic form in which the aldehyde function is masked.[14] atroposelective character of this reaction, we favor the fol-
This difficulty was circumvented by controlled hydrolysis of lowing factors after examination of molecular models of
2l which afforded the desired chiroporphyrin with mono-N- the intermediate porphyrinogen. Steric exclusion apparently
substituted amide substituents. It has been reported that disfavours the cyclisation of linear tetrapyrroles having cis
treatment of acylureas of general formula RCON(C6H11)- cyclopropyl substituents on neighbouring meso carbons,
CONHC6H11 with phosphorus oxychloride in benzene and which therefore will lead to tars upon further polymeris-
584
Eur. J. Org. Chem. 2000, 583Ϫ589

Preparation and Spectral Characterization
FULL PAPER
Scheme 3. Symmetry elements and NMR of chiroporphyrins;
homochiral substitutents are depicted as left hands
Figure 1. H (top) and 13C (bottom) NMR spectra of tetramethyl-
chiroporphyrin 2a
1
ation. On the other hand, an α,β,α,β substituted linear
tetrapyrrole is preorganised for cyclisation by weak C–H O
hydrogen bonding between opposite meso substituents,
leading to facile porphyrinogen cyclisation as shown in Fig-
ure 3 for tetramethylchiroporphyrinogen. Similar argu-
ments have been used to explain the high yield synthesis
of 2l.[15]
Figure 3. Conformation of an α,β,α,β substituted tetrapyrrole in-
termediate, preorganised by weak C–H O hydrogen bonds be-
tween methyl ester substituents, which leads to facile cyclisation to
the porphyrinogen. For the sake of clarity, only the H-bonding pat-
tern on the top face is shown, and each of the two meso substituents
on the bottom face is abbreviated as R
UV/Visible Spectroscopy
In Table 1 are collected the wavelengths of absorption
Figure 2. 1H (top) and 13C (bottom) NMR spectra of tetra-N- maxima for the Soret and Q bands of chiroporphyrins 2a–
methyl-N-phenylchiroporphyrin 2j
m, and those of H2TPP (meso-tetraphenylporphyrin),
Eur. J. Org. Chem. 2000, 583Ϫ589
585

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C. Perollier, M. Mazzanti, J.-P. Simonato, F. Launay, R. Ramasseul, J.-C. Marchon
FULL PAPER
Table 1. Wavelengths (nm) of the absorption band maxima of for those derived from esters (11–14 nm). However it is
chiroporphyrins 2a–2m in dichloromethane
smaller than that observed for the highly distorted
H2TtBuP (29 nm) which exhibits anomalous porphyrinic
properties.[22]
Compound
Soret
Q bands
2a
428
428
428
428
430
428
431
428
431
432
434
434
432
417
422
420
446
528
528
528
536
530
528
529
537
536
532
533
534
532
515
525
522
552
565
565
565
565
567
565
567
565
565
563
564
574
569
552
562
557
596
605
605
605
605
605
605
608
605
605
609
610
608
608
594
603
602
628
663
663
662
660
664
663
666
665
670
663
663
662
667
650
2b
1H NMR Spectroscopy
2c
2d
In Table 2 the 1H-NMR chemical shifts of the pyrrole NH
and β protons for chiroporphyrins 2a–m are listed and com-
pared to those of porphine, H2TMP (meso-tetramesitylpor-
phyrin), H2TiPrP, and H2TtBuP. Due to the aromatic ring
current, the resonance of the β pyrrolic protons of porphine
(δ ϭ 9.74) are shifted to lower field by about 4 ppm relative
to those of pyrrole, whereas its inner NH protons (δ ϭ
2e
2f
2g
2h
2i
2j
2k
2l
2m
H2TPP[a]
H2TCHP[a]
H2TiPrP[b]
H2TtBuP[b]
660 –3.76) are shifted to higher field by about 11 ppm. For chir-
658
691
oporphyrins 2a–m the resonances of the NH protons (δ ϭ
–1.66 to –1.15) are also upfield shifted, but to a lower extent
consistent with their less planar porphyrin ring and reduced
ring current. Furthermore these shifts are correlated to the
[a]
[b]
Ref.[21]
–
Ref.[22]
H2TCHP (meso-tetracyclohexylporphyrin),[21] H2TiPrP molecular volume of the R substituent[6] and are larger for
(meso-tetra-isopropylporphyrin) and H2TtBuP (meso-tetra- the amides. The largest shift (2.61 ppm between 2m and
tert-butylporphyrin)[22] are included for comparison. The porphine) remains small compared to the 11 ppm difference
small red shift of the Soret (10–17 nm) and Q bands of the between porphine and pyrrole. Thus the aromaticity of the
chiroporphyrins relative to H2TPP can be explained by the chiroporphyrin is not strongly affected, as confirmed by the
non planar distortion of the porphyrin induced by the steric small red shift observed in UV-visible spectroscopy.
bulk of the meso substituents.[23] The red shift is larger for
This conclusion is corroborated by the chemical shifts of
the chiroporphyrins derived from amides (15–17 nm) than the singlet pair for the β pyrrolic protons, which are not
1
Table 2. H-NMR data (δ values) in CDCl3 for chiroporphyrins 2a–2m and the starting biocartol derivatives 1a–1m[a]
δNH
'
δH pyrrolic
δH1 (∆δH1)
δH2
δMeC2 (∆δMe)
δOthers (∆δ)
2a
2b
2c
2d
2e
2f
–1.66
–1.60
–1.58
–1.36
–1.27
–1.51
–1.45
–1.50
–1.41
–1.29
–1.21
–1.39
9.17–9.18
9.07–9.19
9.06–9.27
9.06–9.15
9.03–9.17
9.11–9.18
9.10–9.45
9.13–9.60
9.14–9.38
9.01–9.13
9.01–9.15
9.03–9.13
2.69 (ϩ0.56)
2.71 (ϩ0.62)
2.61 (ϩ0.60)
2.75 (ϩ0.61)
2.71 (ϩ0.63)
2.86 (ϩ0.70)
2.95 (ϩ0.60)
3.05 (ϩ0.66)
3.00 (ϩ0.64)
2.53 (ϩ0.70)
2.38 (ϩ0.64)
2.83 (ϩ1.04)
2.44
4.75
4.78
4.72
4.83
4.78
4.86
4.95
5.16
5.05
4.58
4.56
4.77
4.62
0.79; 1.87 (–0.46,
ϩ0.34)
3.07 (–0.64) (OMe)
0.82; 1.92 (–0.48,
ϩ0.40)
3.5 (–0.66) (OCH2); 0.75 (–0.46) (Me)
0.44 (–0.98) (tBu)
0.83; 1.92 (–0.38,
ϩ0.42)
0.77; 1.93 (–0.52,
ϩ0.39)
2.85, 3.18 (–0.94,–0.61) (OCH2); 0.32 (–0.59) (tBu)
0.77; 1.92 (–0.45,
ϩ0.45)
4.1 (–0.75) (OCHexo); –0.45, 0.41, 0.42
(ca. –1.2, –0.4, –0.4) (Me)
0.87; 1.97 (–0.37,
ϩ0.44)
4.38, 4.48 (–0.74, –0.63) (OCH2); 6.3, 6.47, 6.85
(ca. –0.8) (o,m,p-Haro
)
2g
2h
2i
0.9; 2.05 (–0.40,
ϩ0.45)
3.55 (–0.15) (OMe); 6.45 (ca. –0.5) (mult Haro)
0.88; 2.05 (–0.50,
ϩ0.42)
6.64, 7.06, 7.5, 7.73 (–0.82, ca. –0.5, ca. –0.5, –0.38)
(Haro
)
0.88; 2.05 (–0.50,
ϩ0.42)
6.51, 7.77 (–0.78, –0.49) (Haro
)
2j
0.95; 1.74 (ϩ0.05,
ϩ0.20)
2.88 (–0.41) (NMe); 7.42–7.66 (ca. ϩ0.22) (Haro)
2k
2l
0.9; 1.72 (ϩ0.06,
ϩ0.21)
3.37 (–0.2); 0.80 (–0.3) (NCH2CH3);
7.42–7.65 (ϩ0.22) (Haro
)
0.86; 1.98 (–0.43,
ϩ0.53)
6.45 (–0.81) (NH), 3.56, 3.88 (–0.05, ϩ0.02) (CHN),
0.87–1.81 (Cy)
2m
–1.15
–3.76
–2.53
–1.60
1.52
9.06–9.21
9.74
0.72; 1.92
4.34 (NH); 3.13 (CHN); 0.81–1.30 (Cy)
porphine[b]
H2TMP
H2TiPrP[c]
H2TtBuP[c]
8.61
9.48
5.34
9.08
[a]
The numbers in parentheses show the difference ∆δ between the chemical shifts of the relevant proton in the chiroporphyrin 2 and the
corresponding biocartol derivative 1. – Ref.[25]
–
Ref.[22]
[b]
[c]
586
Eur. J. Org. Chem. 2000, 583Ϫ589

Preparation and Spectral Characterization
FULL PAPER
10 °C and sodium hydride (60% dispersion of in mineral oil, 1.42 g,
35.4 mmol) was slowly added under gentle argon flow. The reaction
mixture was stirred for 30 minutes, and 4.7 mL (75.4 mmol, 2.1
equiv.) of methyl iodide and DMF (50 mL) were added. The reac-
tion mixture was then warmed to room temperature and stirred for
two more hours. Upon addition of diethyl ether (100 mL), sodium
iodide precipitated and was filtered off. The mixture was washed
by water (6 ϫ 100 mL) and dried with Na2SO4. Column chromato-
graphy (silica gel, CH2Cl2) gave the pure product. Yield: 81%.
NMR and IR spectra were identical to those previously de-
very different from that of porphine (δ ϭ 9.74). The chem-
ical shift difference for each pair of singlets remains smaller
than 0.21 ppm, except for chiroporphyrins 2g–i for which
the four β pyrrolic protons are subjected to the additional
ring current of four phenyl rings. It has been possible to
show by NOE-difference experiments on H2TMCP 2a that
the singlet at lower field effectively belongs to the four Hβ2
protons neighbouring the four ester carbonyl groups.[24]
Our goal was to introduce stereogenic substituents close
to the center of the porphyrin ring, and a comparison of scribed.[13]
corresponding chemical shifts between starting synthons
Optimized Procedure for the Synthesis of meso-Tetrakis[(1R,3S)-1-
and chiroporphyrins can be illustrative of the actual con-
formations (Table 2). The magnetic shielding resulting from
the porphyrin ring current is positive for nuclei located in-
side and negative for nuclei located outside a doubly flared
cylinder passing by the eight pyrrolic β-carbons.[25] The H1
protons, with an average downfield shift of 0.65 ppm relat-
ive to the starting aldehyde, lie outside the nodal cylinder,
and the methyl groups CH3e alike (downfield shift of ca.
0.4 ppm). On the other hand, the CH3i groups with a
0.4 ppm upfield shift are inside the cylinder. All the other
protons belonging to the R groups show upfield shifts of
0.2 to 1.2 ppm. This suggests that the axial areas above and
under the center of the porphyrins remain vacant and that
the stereogenic groups sit on the porphyrin ring close to its
periphery, thus restricting substrate or ligand access to the
metal center along a C2-symmetric groove in the corres-
ponding catalysts. Such a dissymmetric environment is po-
tentially very interesting for enantioselective catalysis.
methoxycarbonyl-2,2-dimethylcycloprop-3-yl]porphyrin (2a): A 2.5-
L commercial brown bottle filled with CH2Cl2 (containing 0.2%
ethanol), equipped with a gas inlet, and shielded from ambient light
by aluminum foil, was purged for one hour with argon. The flask
was further charged with 1.8 g of aldehyde ester 1a (11.5 mmol)
and 0.96 mL of pyrrole (13.8 mmol, 1.2 equiv.) under argon, fol-
lowed 10 minutes later by the addition of 1.08 mL of TFA
(14.0 mmol, 1.2 equiv.). The resulting mixture was magnetically
stirred at room temperature under gentle argon flow for 5 days. At
this time, the reaction mixture was divided in three 2.5-liter bottles
which were completed to a total volume of 7.5 L with CH2Cl2. A
0.86 g sample of DDQ (3 ϫ 3.8 mmol, 0.83 equiv.) was added to
each of the bottles which were magnetically stirred at room temper-
ature under argon for 4 hours. The content of the three flasks was
evaporated to dryness. The residue was chromatographed on 300 g
of alumina (neutral, act. I), eluted with CH2Cl2 containing rising
percentages of ethyl acetate (0, 2, 4, 6, 10%) under UV-visible spec-
troscopic control. The initial impure fractions were discarded and
0.472 g of pure porphyrin 2a was obtained (20% yield relative to
1a). MS (EI, Fe complex generated in situ) m/z: found. 868.810
(M – 2 H ϩ Fe), calcd. for C48H52N4O8Fe: 868.808; (FABϩ) m/z:
814. – UV/Vis (CH2Cl2) λmax/nm (log ε) ϭ 428 (5.56), 528 (4.15),
Experimental Section
1
565 (2.65), 605 (3.71), 663 (3.18). – H NMR (400 MHz, CDCl3)
δ ϭ –1.66 (s, NH), 0.79 (s, 12 H, CH3i ), 1.87 (s, 12 H, CH3e), 2.69
[d, 4 H, J ϭ 8.9 Hz, CH-C(O)], 3.07 (s, 12 H, OCH3), 4.75 [d, 4
H, J ϭ 8.9 Hz, CH-CH-C(O)O], 9.07 (1s, 4 H, Hβ1), 9.18 (s, 4 H,
General Methods and Materials: Solvents and chemicals were used
without purification unless indicated. Dichloromethane was stabil-
ized either by ethanol (Carlo Erba Reagent, ACS for analysis,
C2H5OH 0.2%) or 2-methyl-2-butene (SDS, ‘‘Purex pour analyses’’,
2-methyl-2-butene 0.002%). Pyrrole was purified by filtration on
silica before use. Biocartol ester 1c was a gift from Hoechst–Ma-
rion-Roussel. Esters 1a,b,d–i[13] and amides 1j,k[14] were prepared
according to previously published procedures. Thin-layer chroma-
tography was performed using Merck precoated silica plates 60F-
254. Silica gel (230–400 mesh) and alumina (neutral, act. I) were
used for column chromatography.
H
β2). – 13C NMR (50 MHz, CDCl3) δ 18.2 (CH3), 27.7 (CIV), 29.3
(CH3), 33.2 (CH), 38.3 (CH), 51.0 (OCH3), 110.1 (Cmeso), 127.2
(Cβ), 131.1 (Cβ), 143.7 (Cα), 148.6 (Cα), 170.9 [C(O)]
Typical Procedure for the Synthesis of Porphyrins 2b–l: 14 mmol of
ester or amide 1b–l (0.88 equiv.) and 1.1 mL of pyrrole (1 equiv.)
were dissolved in 1.5 L of CH2Cl2 (stabilized with 0.2% ethanol)
which was degassed with argon for 10 minutes. A 1.23 mL amount
of TFA (1 equiv.) dissolved in 50 mL of CH2Cl2 was then added
under argon. The resulting solution, kept under argon and shel-
tered from light, was stirred for 18 hours at 20 °C. A 3.63 g amount
of DDQ (1 equiv.) was then added, an the mixture was stirred for
three more hours. The solution was evaporated under vacuum and
the residue diluted in CH2Cl2 (150 mL, stabilized with amylene).
Spectroscopy: UV-visible spectra were recorded on a Perkin–Elmer
Lambda 9 instrument. Nuclear magnetic resonance spectra were
obtained with Bruker AC 200, AM 300, and AM 400 instruments.
Spectra are tabulated in the following order: chemical shift (δ
values), multiplicity (s ϭ singlet, d ϭ doublet, t ϭ triplet, q ϭ
quadruplet, m ϭ multiplet, b ϭ broad), coupling constant (J, Hz),
number of protons, assignment [CHaro (aromatic proton), Hβ (β-
pyrrolic protons of chiroporphyrins)]. Mass spectra were deter-
mined on a VG ZAB2-SEQ instrument.
Note: The presence of polymeric material and tar in the crude
product leads to a tedious purification of the porphyrin. The pro-
cedure given thereafter can be modified as necessary.
The resulting suspension was filtered over celite (20 g) or sodium
sulfate to remove the precipitated tars. The filtrate was passed suc-
cessively through three glass frit Buchner funnels containing each
100 g of silica. Several 200 mL aliquots of CH2Cl2, and of CH2Cl2/
AcOEt mixtures (up to 70:30) were used to elute the porphyrin
Synthetic Procedures
Alternative One-Step Procedure for the Synthesis of Methyl
(1R,3S)-2,2-Dimethyl-3-formylcyclopropane-1-carboxylate (1a, bio-
cartol methyl ester): A flask equipped with a magnetic stirring bar (followed by UV-visible spectroscopy). These impure fractions were
was charged with biocartol (5.0 g, 35.2 mmol) and dry THF
(120 mL) under an argon atmosphere. The solution was cooled to
evaporated and the porphyrin further purified over silica plates
with CH2Cl2 as eluent. Occasionnally at the end of the process the
Eur. J. Org. Chem. 2000, 583Ϫ589
587

´
C. Perollier, M. Mazzanti, J.-P. Simonato, F. Launay, R. Ramasseul, J.-C. Marchon
FULL PAPER
free base porphyrin was obtained as a mixture with its zinc complex
(presumably due to inorganic additives on silica plates). In that
case the mixture was dissolved in CH2Cl2, washed with 0.2  HCl
7% yield. MS-FABϩ m/z: 1183 [MHϩ]. – UV/Vis (CH2Cl2) λmax
/
nm (log ε) ϭ 431 (5.47), 529 (4.11), 567 (3.64), 608 (3.59), 666
1
(2.95). H NMR (200 MHz, CDCl3) δ ϭ –1.45 (s, NH), 0.9 (s, 12
(3 ϫ 25 mL) and with a saturated aqueous NaHCO3 solution (3 ϫ H, CH3), 2.05 (s, 12 H, CH3), 2.95 [d, 4 H, J ϭ 8.8 Hz, CH-C(O)],
25 mL). After drying (Na2SO4) and solvent evaporation, the pure
porphyrin was obtained in 2–15% yield.
3.55 (s, 12 H, OCH3), 4.95 [d, 4 H, J ϭ 8.8 Hz, CH-CH-C(O)O],
6.45 (m, 16 H, Haro), 9.1 (s, 4 H, Hβ), 9.45 (s, 4 H, Hβ).
meso-Tetrakis[(1R,3S)-1-(m-nitrophenoxycarbonyl)-2,2-dimethyl-
cycloprop-3-yl]porphyrin (2h): Chiroporphyrin 2h was obtained in
14% yield. MS-FABϩ 1243 [MHϩ]. – UV/Vis (CH2Cl2) λmax/nm
(log ε) ϭ 428 (5.2), 537 (4), 565 (3.5), 605 (3.5), 665 (3.1). – 1H
NMR (200 MHz, CDCl3) δ ϭ –1.5 (s, NH), 0.88 (s, 12 H, CH3),
2.05 (s, 12 H, CH3), 3.05 (d, 4 H, J ϭ 8.8 Hz, CH-C(O)), 5.16 (d,
4 H, J ϭ 8.8 Hz, CH-CH-C(O)O), 6.64 (ddd, 4 H, CHaro, J ϭ 8.17,
J ϭ 2 and J ϭ 1 Hz), 7.06 (dd, 4 H, CHaro, J ϭ 8.2, 2 and 1 Hz),
7.5 (dd, 4 H, CHaro, J ϭ 8.2 and 2 Hz), 7.73 (ddd, 4 H, CHaro, J ϭ
8.1, 2 and 1 Hz), 9.13 and 9.60 (2s, 8 H, Hβ).
meso-Tetrakis[(1R,3S)-1-ethoxycarbonyl-2,2-dimethylcycloprop-3-
yl]porphyrin (2b): Chiroporphyrin 2b was obtained in 2% yield. –
UV/Visible (CH2Cl2) λmax/nm ϭ 428, 528, 565, 605, 663. – 1H
NMR (300 MHz, CDCl3): δ ϭ –1.6 (s, NH), 0.75 (t, 12 H, J ϭ
7.05 Hz), 0.82 (s, 12 H, CH3), 1.92 (s, 12 H, CH3), 2.71 [d, 4 H,
J ϭ 8.8 Hz, CH-C(O)], 3.55 (m, 8 H, OCH2), 4.78 [d, 4 H, J ϭ
8.8 Hz, CH-CH-C(O)O], 9.07 (1s, 4 H, Hβ1), 9.19 (s, 4 H, Hβ2). –
13C NMR (50 MHz, CDCl3): δ ϭ 13.7 (CH3), 18.1 (CH3), 27.5
(CIV), 29.2 (CH3), 33.2 (CH), 37.9 (CH), 59.5 (OCH2), 110.0
(Cmeso), 127.6 (Cβ pyr.), 130.9 (Cβ), 145.8 (Cα pyr.), 153.7 (Cα),
170.3 (CϭO).
meso-Tetrakis[(1R,3S)-1-(p-nitrophenoxycarbonyl)-2,2-dimethyl-
cycloprop-3-yl]porphyrin (2i): Chiroporphyrin 2i was obtained in
5.5% yield. Crystallization of the pure product was induced by slow
addition of n-hexane to a concentrated dichloromethane solution
of the crude product. UV/Vis (CH2Cl2) λmax /nm (log ε) ϭ 431
meso-Tetrakis[(1R,3S)-1-tert-butoxycarbonyl-2,2-dimethylcyclo-
prop-3-yl]porphyrin (2c): Chiroporphyrin 2c was obtained in 5%
yield. MS-FABϩ m/z: 983.2 [MHϩ]. – UV/Vis (CH2Cl2) λmax/nm
1
428, 528, 565, 605, 662. – H NMR: δ ϭ –1.58 (s, NH), 0.44 (s, 36
1
(5.5), 536 (4), 565 (3.6), 605 (3.6), 670 (3). – H NMR (200 MHz,
H, tBu), 0.83 (s, 12 H, CH3), 1.92 (s, 12 H, CH3), 2.61 [d, 4 H, J ϭ
8.8 Hz, CH-C(O)], 4.72 [d, 4 H, J ϭ 8.8 Hz, CH-CH-C(O)O], 9.06
(1s, 4 H, Hβ1), 9.27 (s, 4 H, Hβ2). – 13C NMR 50 MHz, CDCl3, δ
18.4 (CH3), 27.2 (CH3 tBu), 29.4 (CH3), 30.7 (CIV tBu) 34.7 (CH),
37.7 (CH), 79.4 (CIV tBuO), 110.4 (Cmeso), 127.5 (Cβ pyr.), 131.1
(Cβ), 142.9 (Cα pyr.), 149.2 (Cα), 169.8 (CϭO).
CDCl3) δ ϭ –1.41 (s, NH), 0.88 (s, 12 H, CH3), 2.05 (s, 12 H, CH3),
3.0 [d, 4 H, J ϭ 8.8 Hz, CH-C(O)], 5.05 [d, 4 H, J ϭ 8.8 Hz, CH-
CH-C(O)O], 6.51 (d, 8 H, J ϭ 8.6 Hz, CHaro), 7.77 (d, 8 H, J ϭ
8.6 Hz, CHaro), 9.14 and 9.38 (2s, 8 H, Hβ).
meso-Tetrakis[(1R,3S)-1(N-methyl-N-phenyl)carbamoyl-2,2-dimeth-
ylcycloprop-3-yl]porphyrin (2j): Chiroporphyrin 2j was obtained in
meso-Tetrakis[(1R,3S)-1-neopentoxycarbonyl-2,2-dimethyl-
cycloprop-3-yl]porphyrin (2d): Chiroporphyrin 2d was obtained in
1.5% yield. MS-FABϩ m/z: 1039.6 [MHϩ]. – UV/Vis (CH2Cl2)
λmax/nm (log ε) ϭ 428 (5.5), 536 (4), 565 (3.6), 605 (3.5), 660(3). –
1H NMR (200 MHz, CDCl3) δ ϭ –1.36 (s, NH), 0.32 (s, 36 H,
tBu), 0.77 (s, 12 H, CH3), 1.93 (s, 12 H, CH3), 2.75 [d, 4 H, J ϭ
8.8 Hz, CH-C(O)], 2.85 (d, 4 H, J ϭ 10.5 Hz, OCH), 3.18 (d, 4 H,
J 10.5 Hz, OCH), 4.83 [d, 4 H, J ϭ 8.8 Hz, CH-CH-C(O)O], 9.06
and 9.15 (2s, 8 H, Hβ).
7% yield. MS-FABϩ m/z: 1114 [M•ϩ] [exact mass of MHϩ
ϭ
1115.5868 (∆ ϭ 3.8 ppm); exact mass of M•ϩ ϭ 1114.5602 (∆ ϭ
21 ppm)]. – UV/Vis (CH2Cl2) λmax/nm ϭ 432, 532, 563, 609, 663. –
1H NMR (400 MHz, CDCl3) δ ϭ –1.29 (br. s, 2 H, NH), 0.95 (s,
12 H, CH3), 1.74 (s, 12 H, CH3), 2.53 [d, J ϭ 8.2 Hz, 4 H, CH-
C(O)N], 2.88 (s, 12 H, N-CH3), 4.58 [d, J ϭ 8.2 Hz, 4 H, CH-CH-
C(O)N], 7.42–7.66 (m, 20 H, CHaro), 9.01 and 9.13 (2s, 8 H, Hβ). –
13C NMR (100 MHz, CD2Cl2) δ ϭ 18.0 (Me), 27.6 (CIV), 28.6
(CH3), 32.5 (CH), 37.1 (CH), 38.0 (N-CH3), 111.3 (CIV meso),
127.4 (CHaro), 128.0 (CHaro), 128.2 (Cβ), 130.0 (CHaro), 130.5
(Cβ), 145.6 (CIV aro), 146.3 (b, Cα), 169.3 (CϭO).
meso-Tetrakis[(1R,3S)-1-(1(S)-endo-bornoxy)carbonyl-2,2-dimeth-
ylcycloprop-3-yl]porphyrin (2e): Chiroporphyrin 2e was obtained in
5% yield. MS-FABϩ m/z: 1303.8 [MHϩ]. – UV/Vis (CH2Cl2) λmax
/
meso-Tetrakis[(1R,3S)-1(N-ethyl-N-phenyl)carbamoyl-2,2-di-
methylcycloprop-3-yl]porphyrin (2k): Chiroporphyrin 2k was pre-
pared in 6% yield using the ‘‘typical procedure’’. By adding Et3N
(1 equiv.) after reaction with DDQ, the yield rose to 12%. MS-
FABϩ m/z: 1171.7 [MHϩ]. – UV/Vis (CH2Cl2) λmax/nm ϭ 434, 533,
nm (log ε) ϭ 376 (4.1), 430 (5.4), 530 (4), 567 (3.6), 605 (3.6), 664
1
(3). – H NMR (200 MHz, CDCl3) δ ϭ –1.27 (s, NH), –0.45 (s, 12
H, bornyl CH3 ), 0.41 (s, 12 H, bornyl CH3), 0.42 (s, 12 H, bornyl
CH3), 0.77 (s, 12 H, CH3), 1.92 (m, bornyl H), 1.92 (s, 12 H, CH3),
2.71 [d, 4 H, J ϭ 8.8 Hz, CH-C(O)], 4.10 (m, 4 H, bornyl OCH),
4.78 [d, 4 H, J ϭ 8.8 Hz, CH-CH-C(O)O], 9.03 and 9.17 (2s, 8
H, Hβ).
1
564, 610, 633. – H NMR (400 MHz, CDCl3) δ ϭ –1.21 (b, 2 H,
NH), 0.80 (t, J ϭ 6.8 Hz, 12 H, CH3), 0.90 (s, 12 H, CH3), 1.72 (s,
12 H, CH3), 2.38 [d, J ϭ 8.3 Hz, 4 H, CH-C(O)N], 3.37 (m, 8 H,
N-CH2), 4.56 [d, J ϭ 8.3 Hz, 4 H, CH-CH-C(O)N], 7.42–7.65 (m,
20 H, CHaro), 9.01 and 9.15 (2s, 8 H, Hβ). – 13C NMR (100 MHz,
CD2Cl2) δ 12.7 (Me), 17.4 (Me), 26.8 (CIV), 27.9 (CH3), 32.2 (CH),
37.2 (CH), 43.2 (N-CH2), 110.7 (CIV meso), 126.9 (CHaro), 127.5
(Cβ), 128.4 (CHaro), 129.2 (CHaro), 130.0 (Cβ), 143.4 (CIV aro),
144.4 (Cα), 146.1 (Cα), 168.0 (CϭO, CIV).
meso-Tetrakis[(1R,3S)-1-benzyloxycarbonyl-2,2-dimethylcycloprop-
3-yl]porphyrin (2f): Chiroporphyrin 2f was obtained in 2% yield. –
1
UV/Vis (CH2Cl2) λmax/nm ϭ 428, 528, 565, 605, 663. – H NMR
(300 MHz, CDCl3) δ ϭ –1.51 (s, NH), 0.87 (s, 12 H, CH3), 1.97 (s,
12 H, CH3), 2.86 [d, 4 H, J ϭ 8.9 Hz, CH-C(O)O], 4.38 (d, 4 H,
J ϭ 12.2 Hz, benzylic OCH), 4.48 (d, 4 H, J ϭ 12.2 Hz, OCH),
4.86 [d, 4 H, J ϭ 8.8 Hz, CH-CH-C(O)O], 6.30 (d, 8 H, CHaro-o
,
(1R,3S)-N-(N’-cyclohexyl)carbamoyl-N-cyclohexyl-3-formyl-2,2-di-
methylcyclopropane-1-carboxamide (1l): (1R)-cis-hemicaronal-
dehydic acid (7.1 g, 50 mmol), Et3N (8.4 mL, 1.2 equiv.), and DCC
(12.4 g, 60 mmol, 1.2 equiv.) were mixed and stirred in DMF
(100 mL) for 12 hours. After addition of CH2Cl2 (25 mL), the reac-
tion mixture was washed successively with an aqueous HCl (10%)
solution (3 ϫ 25 mL), with a saturated aqueous NaHCO3 solution
(3 ϫ 25 mL) and with water (8 ϫ 25 mL). The organic layer was
dried with Na2SO4 and the solvent was removed in vacuo. The
J ϭ 7.6 Hz), 6.47 (t, 8 H, CHaro-m, J ϭ 7.6 Hz), 6.85 (t, 4 H, CHaro-p
,
J ϭ 7.3 Hz), 9.11(s, 4 H, Hβ), 9.18 (s, 4 H, Hβ). – 13C NMR
75 MHz, CDCl3 δ 18.2 (CH3), 28.1 (CIV), 29.2 (CH3), 33.6 (CH),
38.4 (CH), 66.0 (OCH2), 110.7 (Cmeso), 127.9 (CHaro), 128.0
IV
(CHaro), 128.1 (CHaro et Cβ), 131.3 (Cβ), 136.0 (C ), 144.7 (Cα),
aro
147.8 (Cα), 170.6 (CϭO).
meso-Tetrakis[(1R,3S)-1-(p-methoxyphenoxycarbonyl)-2,2-dimeth-
ylcycloprop-3-yl]porphyrin (2g): Chiroporphyrin 2g was prepared in
588
Eur. J. Org. Chem. 2000, 583Ϫ589

Preparation and Spectral Characterization
FULL PAPER
[3]
[3a]
For recent reviews, see:
J. P. Collman, X. Zhang, V. J. Lee,
residue was purified by silica gel chromatography. Elution with a
CH2Cl2/AcOEt mixture (90:10) gave 8.6 g of 1l (50% yield). NMR
and IR spectra were identical to those previously described.[13]
E. S. Uffelman, J. I. Brauman, Science 1993, 261, 1404–1410. –
[3b]
Y. Naruta, in: Metalloporphyrins in Catalytic Oxidations
(Ed.: R. A. Sheldon), Marcel Dekker, New York, 1994, pp.
[3c]
241–259. –
L. A. Campbell, T. Kodadek, J. Mol. Catal. A:
meso-Tetrakis{(1R,3S)-1[N-(N’-cyclohexyl)carbamoyl-N-cyclo-
hexyl]carbamoyl-2,2-dimethylcycloprop-3-yl}porphyrin (2l): Chiro-
porphyrin 2l was prepared in 34% yield using the ‘‘typical proced-
ure’’. By adding Et3N (1 equiv.) after reaction with DDQ, the yield
rose to 60%. MS-FABϩ m/z: 1583.8 [MHϩ]. – UV/Vis (CH2Cl2)
λmax/nm ϭ 434, 534, 574, 608, 662. – 1H NMR (200 MHz, CDCl3)
δ ϭ –1.39 (br. s, 2 H, NH) 0.86 (s, 12 H, CH3), 0.87–1.81 (m,
cyclohexyl), 1.98 (s, 12 H, CH3), 2.83 [d, J ϭ 8.3 Hz, 4 H, CH-
C(O)N], 3.56 (m, 4 H, N-CH), 3.88 (m, 4 H, N-CH), 4.77 [d, J ϭ
8.3 Hz, 4 H, CH-CH-C(O)N], 6.45 (br. s, 4 H, NH), 9.03 and 9.13
(2s, 8 H, Hβ). – 13C NMR (100 MHz, CD2Cl2) δ ϭ 18.1 (Me), 24.8
(CH2), 25.5 (CH2), 25.7 (CH2), 26.6 (CH2), 28.6 (CIV), 29.5 (CH
or CH3), 29.9 (CH2), 31.4 (CH2), 31.7 (CH2), 32.8 (2 CH2), 34.1
(CH or CH3), 39.1 (CH or CH3), 49.6 (CH or CH3), 53.6 (CH2),
55.6 (CH or CH3), 110.3 (CIV meso), 127.7 (Cβ), 130.9 (Cβ), 143.9
(Cα), 147.9 (Cα), 154.8 (CϭO), 170.8 (CϭO).
[3d]
Chem. 1996, 113, 293–310. –
K. S. Suslick, S. Van Deusen-
Jeffries, in: Comprehensive Supramolecular Chemistry (Eds.: J.
L. Atwood, J. E. D. Davies, D. D. MacNicol, F. Vögtle, J. M.
Lehn), Elsevier, Oxford, 1996; vol. 5, pp. 141–170. – [3e] E. Rose,
A. Lecas, M. Quelquejeu, A. Kossanyi, B. Boitrel, Coord.
Chem. Rev. 1998, 178–180, 1407–1431.
For recent reviews, see: [4a] E. N. Jacobsen, in: Catalytic Asym-
[4]
[5]
metric Synthesis (Ed.: I. Ojima), VCH, New York, 1993, pp.
[4b]
159–202. –
87–107.
T. Katsuki, J. Mol. Catal. A: Chem. 1996, 113,
[5a]
See, for example:
J. P. Collman, Z. Wang, A. Straumanis,
M. Quelquejeu, E. Rose, J. Am. Chem. Soc. 1999, 121, 460–
461. – [5b] E. Rose, M. Quelquejeu, R. P. Pandian, A. Lecas, A.
Vilar, C. Avaritsioti, J. P. Collman, Z. Wang, A. Straumanis,
Polyhedron, in press.
[6]
[7]
[8]
´
´
C. Perollier, J. Pecaut, R. Ramasseul, J.-C. Marchon, Inorg.
Chem. 1999, 38, 3758–3759.
J. Martel, in: Chirality in Industry (Eds.: A. N. Collins, G. N.
Sheldrake, J. Crosby), Wiley, Chichester, 1992, chapter 4.
M. Veyrat, O. Maury, F. Faverjon, D. E. Over, R. Ramasseul,
J.-C. Marchon, I. Turowska-Tyrk, W. R. Scheidt, Angew. Chem.
Int. Ed. Engl. 1994, 33, 220–223.
meso-Tetrakis[(1R,3S)-1(N-cyclohexyl)carbamoyl-2,2-dimethyl-
cycloprop-3-yl]porphyrin (2m): Compound 2l (100 mg) was dis-
solved in dry benzene (10 mL) under argon, POCl3 (212 µL) was
added, and the mixture was stirred for 5 days. Water (5 mL) was
then added. After stirring for one more day, the reaction mixture
was washed with a saturated aqueous NaHCO3 solution (3 ϫ
25 mL). The organic layer was dried with Na2SO4 and the solvent
removed under vacuum. After TLC (CH2Cl2/MeOH: 96:4) of the
residue, 40 mg of chiroporphyrin 2m were obtained (yield 60%).
MS-FABϩ m/z: 1082.7 [M•ϩ]. – UV/Vis (CHCl3) λmax/nm ϭ 432,
[9]
´
J.-P. Simonato, J. Pecaut, W. R. Scheidt, J.-C. Marchon, Chem.
Commun. 1999, 989–990.
[10]
[11]
[12]
[13]
M. Mazzanti, M. Veyrat, R. Ramasseul, J.-C. Marchon, I. Tu-
rowska-Tyrk, W. R. Scheidt, Inorg. Chem. 1996, 35, 3733–3734.
J.-P. Simonato, J. Pecaut, J.-C. Marchon, J. Am. Chem. Soc.
´
1998, 120, 7363–7364.
´
D. Toronto, F. Sarrazin, J. Pecaut, J.-C. Marchon, M. Shang,
W. R. Scheidt, Inorg. Chem. 1998, 37, 526–532.
M. Veyrat, L. Fantin, S. Desmoulins, A. Petitjean, M. Maz-
zanti, R. Ramasseul, J.-C. Marchon, R. Bau, Bull. Soc. Chim.
Fr. 1997, 134, 703–711.
1
532, 569, 608, 667. – H NMR (200 MHz, CDCl3) δ ϭ –1.15 (b, 2
[14]
[15]
´
´
C. Perollier, J. Pecaut, R. Ramasseul, J.-C. Marchon, Bull. Soc.
H, NH), 0.72 (s, 12 H, CH3), 0.81–1.30 (m, cyclohexyl), 1.92 (s, 12
H, CH3), 2.44 [d, J ϭ 8.8 Hz, 4 H, CH-C(O)N], 3.13 (m, 4 H, N-
CH), 4.34 (d, J ϭ 7.3 Hz, 4 H, NH), 4.62 [d, J ϭ 8.8 Hz, 4 H, CH-
CH-C(O)N], 9.06 and 9.21 (2s, 8 H, Hβ); 1H NMR (200 MHz,
CD2Cl2) δ ϭ –1.27 (b, 2 H, NH), 0.75 (s, 12 H, CH3), 0.68–1.30
(m, cyclohexyl), 1.93 (s, 12 H, CH3), 2.38 [d, J ϭ 9.1 Hz, 4 H, CH-
C(O)N], 3.15 (m, 4 H, N-CH), 5.12 (d, J ϭ 7.9 Hz, 4 H, NH), 4.71
[d, J ϭ 8.5 Hz, 4 H, CH-CH-C(O)N], 9.14 and 9.22 (2s, 8 H, Hβ). –
13C NMR (50 MHz, CD2Cl2) δ 18.3, 24.5, 25.6, 26.6, 29.8, 30.1,
33.0, 35.6, 36.9, 47.5, 110.3 (CIV meso), 129.9 (Cβ), 130.8 (Cβ),
146.1 (Cα), 146.8 (Cα), 168.9 (CϭO).
Chim. Fr. 1997, 134, 517–523.
´
´
C. Perollier, J. Pecaut, R. Ramasseul, R. Bau, J.-C. Marchon,
Chem. Commun. 1999, 1597–1598.
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In some cases the zinc complex of the porphyrin is also ob-
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purification.
H. Frauenrath, T. Philipps, Liebigs Ann. Chem. 1985, 1303–
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[18]
[19]
[20]
[21]
Acknowledgments
[22]
[23]
We thank Dr. Jean Buendia of Hoechst–Marion Roussel for a gen-
erous supply of biocartol, Marc Veyrat for breaking new ground in
the synthesis of 2a, Patrick Dubourdeaux and Nathalie Gon for
help with the syntheses, Colette Lebrun for providing the mass
spectra.
W. Jentzen, M. C. Simpson, J. D. Hobbs, X. Song, T. Ema, N.
Y. Nelson, C. J. Medforth, K. M. Smith, M. Veyrat, M. Maz-
zanti, R. Ramasseul, J.-C. Marchon, T. Takeuchi, W. A. God-
dard III, J. A. Shelnutt, J. Am. Chem. Soc. 1995, 117, 11085–
11097.
[24]
[25]
´
M. Veyrat, Doctoral Thesis, Universite de Grenoble, 1994.
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D. Yang, M.-K. Wong, Y.-C. Yip, X.-C. Wang, M.-W. Tang,
H. Scheer, J. J. Katz, in: Porphyrins and Metalloporphyrins (Ed.:
K. M. Smith), Elsevier, Amsterdam, 1975, chapter 10.
Received July 6, 1999
J.-H. Zheng, K.-K. Cheung, J. Am. Chem. Soc. 1998, 120,
5943–5952.
[2]
A. Armstrong, B. R. Hayter, Chem. Commun. 1998, 621–622.
[O99435]
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589