Reaction of cobalt porphyrins with aldehydes in the presence of t-butyl hydroperoxide

Article abstract of DOI:10.1016/S0022-328X(98)00921-8

Co^II porphyrin reacted with propanal in the presence of NaBH₄ under air to give a mixture of σ-(1-formylethyl)Co^III porphyrin and σ-(propanoyl)Co^III porphyrin. The latter was formed exclusively by using t-butyl hydroperoxide instead of NaBH₄ and air. Thus, various σ-(acyl)Co^III porphyrins were produced in good yields by way of generation of a t-butoxyl radical, hydrogen abstraction from aldehyde, and coupling of an acyl radical and Co^II porphyrin. This reaction was applied to acyl radical cyclization of 2-allyloxy-1-naphthaldehyde, 2-allyloxybenzaldehyde, 2-allylbenzaldehyde, and N-allylpyrrole-2-carboxaldehyde to give (organo)Co^III porphyrins with a cyclized axial alkyl ligand.

Full text of DOI:10.1016/S0022-328X(98)00921-8

Journal of Organometallic Chemistry 575 (1999) 21–32
Reaction of cobalt porphyrins with aldehydes in the presence of
t-butyl hydroperoxide
Jun-ya Watanabe, Jun-ichiro Setsune *
Department of Chemistry, Faculty of Science, and Graduate School of Science and Technology, Kobe Uni6ersity, Nada-Ku,
Kobe 657-8501, Japan
Received 12 May 1998; received in revised form 26 August 1998
Abstract
CoII porphyrin reacted with propanal in the presence of NaBH4 under air to give a mixture of s-(1-formylethyl)CoIII porphyrin
and s-(propanoyl)CoIII porphyrin. The latter was formed exclusively by using t-butyl hydroperoxide instead of NaBH4 and air.
Thus, various s-(acyl)CoIII porphyrins were produced in good yields by way of generation of a t-butoxyl radical, hydrogen
abstraction from aldehyde, and coupling of an acyl radical and CoII porphyrin. This reaction was applied to acyl radical
cyclization of 2-allyloxy-1-naphthaldehyde, 2-allyloxybenzaldehyde, 2-allylbenzaldehyde, and N-allylpyrrole-2-carboxaldehyde to
give (organo)CoIII porphyrins with a cyclized axial alkyl ligand. © 1999 Elsevier Science S.A. All rights reserved.
Keywords: Cobalt porphyrins; t-Butyl hydroperoxide; Aldehydes
1. Introduction
alkenes led to good yields of the highly functionalized
alkene products.
In this context, it is of great importance to establish
convenient methods for cobalt-carbon bond formation.
There are three ways to synthesize (organo)CoIII com-
plexes; (i) reaction of CoIII complexes with Grignard
reagents [5], (ii) reaction of CoII complexes with organic
radicals [6], and (iii) reaction of CoI complexes with
alkyl halides [7]. We have paid attention to the second
method because CoII complexes are readily prepared.
Although the coupling reaction of organic radicals and
CoII complexes occurs readily, and is a process occur-
ring in coenzyme B12-dependent biochemical reactions
[8], the direct alkylation of CoII is not widely applicable
owing to the limitation on the reaction conditions
required to generate organic radicals. We have reported
that s-(alkyl)CoIII porphyrins are produced in good
yields by the reaction of CoII porphyrin with alkene,
alkyne [9], and ether [10] in the coexistence of NaBH4
and t-BuOOH or O2. A Co–C bond is formed through
the hydrometallation of alkene and alkyne with a hypo-
thetical (hydrido)CoIII porphyrin (Scheme 1). This hy-
drometallation step is explained in terms of the addition
Recent studies on cobalt-mediated radical reactions
by Johnson [1], Pattenden [2], Branchaud [3], and Bald-
win [4] have established the synthetic methodology
which consists of the homolytic CoC bond cleavage of
a variety of alkyl and acyl cobalt reagents and the
addition of the resulting carbon-centered radical to
carbon-carbon multiple bonds. These organocobalt
reagents have been synthesized by the reaction of a
nucleophilic CoI reagent with alkyl or acyl halides.
Pattenden and co-workers have elegantly taken advan-
tage of the weakness of Co-C bonds of a variety of
organocobalt compounds using salen (N,N%-disalicyli-
dene-1,2-diaminoethane) and salophen (N,N%-disalicyli-
dene-1,2-diaminobenzene) ligands to generate a carbon
centered radical [2]. They showed that irradiation of
deaerated refluxing CH2Cl2 solutions of the s-
(acyl)CoIII salophens in the presence of non-activated
* Corresponding author.
0022-328X/99/$ - see front matter © 1999 Elsevier Science S.A. All rights reserved.
PII: S0022-328X(98)00921-8

22
J.-y. Watanabe, J.-i. Setsune / Journal of Organometallic Chemistry 575 (1999) 21–32
of a hydrogen radical to alkene and the capture of the
resulting alkyl radical by CoII porphyrin on the basis of
the high regioselectivity corresponding to the formation
of the most stable organic radical. On the other hand,
a Co–C bond is formed through the reaction of CoII
porphyrin with an ether radical caused by hydrogen
abstraction with a t-butoxyl radical or a hydrogen
radical from the a-position of ether (Scheme 2). Thus,
our redox system consisting of CoII porphyrin, NaBH4,
and an oxidizing agent may be used for generating
various organic radicals.
In view of the synthetic utility of s-(acyl)CoIII com-
plexes for functionalization of alkenes, we have investi-
gated the reaction of aldehydes with our
radical-generating system [11]. In this paper, we de-
scribe the scope and mechanism for the formation of a
variety of s-(acyl)CoIII porphyrins including some ex-
amples where an acyl radical undergoes cyclization
before the coupling with CoII porphyrin.
Scheme 2.
2. Results and discussion
other hand, (hydrido)CoIII porphyrin has never been
known so far, probably due to its rapid decomposition
to CoII porphyrin and H2. NaBH4 readily reduces
(halogeno)CoIII porphyrin to CoII porphyrin with
evolving hydrogen gas probably via a (hydrido)CoIII
intermediate. This (hydrido)CoIII species should be re-
sponsible for the formation of s-(2-hexyl)CoIIIOEP in a
40% yield, when OEPCoIII–Cl was reacted with 1-hex-
2.1. Reaction of (halogeno)CoIII porphyrin with
aldehyde in the presence of NaBH4
It has been reported that (hydrido)RhIII octaethyl-
porphyrin (OEPRhIII-H) is converted quantitatively
into s-(a-hydroxyalkyl)RhIII complexes by the hy-
drometallation of aldehydes in the presence of an excess
amounts of molecular hydrogen [12]. The latter is
needed to suppress equilibrium loss of OEPRhIII-H
leading to OEPRhII and molecular hydrogen. On the
Scheme 1.
Scheme 3.

J.-y. Watanabe, J.-i. Setsune / Journal of Organometallic Chemistry 575 (1999) 21–32
23
1
mixture by H-NMR spectroscopy (Scheme 4). These
products could not be separated because they decom-
posed during column chromatography on silica gel. The
compounds, 3b and 5b, were identified on the basis of
1
the similarity of their H-NMR spectra to those of 3a
and 5a. Substantially the same splitting pattern of the
signals due to the axial ligand of 4b as that of 3b with
very different ring current effects between 3b and 4b is
consistent with s-(1-formylethoxy)CoIII structure for
4b. Although it is well known that insertion of dioxygen
into a MIII–C bond generates s-(alkylperoxo)MIII com-
plexes especially in the cases of secondary and tertiary
s-alkyl groups [15], s-(1-formylethylperoxo)CoIII struc-
1
ture is not consistent with the H-NMR data observed
for 4b. It was reported that the axial CH2 proton signal
shifts from −2.67 to −0.45 ppm upon going from
OEPCoIII–CH2Ph to OEPCoIII–OOCH2Ph [16]. There-
fore, the observed chemical shift (−3.98 ppm) due to
the methine proton of 4b is not consistent with the
Scheme 4.
ene in the presence of NaBH4 at room temperature
under an argon atmosphere (Scheme 3). These reaction
conditions were applied to examine reaction behavior
of a hypothetical (hydrido)CoIII complex toward alde-
hyde. When TPPCoIII–Cl (1a) (TPP, meso-tetraphenyl-
porphyrin dianion) was allowed to react with propanal
and NaBH4 under argon, TPPCoIII–CH(Me)CHO (3a)
CoIII–OOCH(Me)CHO structure but with the CoIII
–
OCH(Me)CHO structure taking into account the chem-
ical shift (−3.57 ppm) of the methine proton of 3b. As
for the chemical shift of the methine proton of 4b in
comparison with that of 3b, the stronger shielding effect
due to the porphyrin ring current on the axial b-carbon
position than on the axial a-carbon position can cancel
out the deshielding effect of the oxygen atom inserted
into the CoIII–C bond. Furthermore, the chemical
shifts of the formyl proton and the methyl protons due
to the axial ligand are shifted from 2.53 to 6.33 ppm
and from −5.93 to −1.20 ppm, respectively, upon
going from 3b to 4b. These chemical shift changes (ca.
4 ppm) are just in the range expected for the differences
in the ring current effect between the protons attached
at the b-carbon position and at the g-carbon position
relative to Co [17].
The carbonyl stretching mode of 3b was observed at
1664 cm−1 in the IR spectrum. This much lower fre-
quency than the ordinary w(CꢀO) values is characteris-
tic of s-(alkyl)metal(III) complexes with a carbonyl
group at the b-position with respect to the metal and is
indicative of the overlap between the filled metal d-or-
bital and the CꢀO anti-bonding orbital [18]. The s-(1-
formylethyl)CoIII structure of 3b was confirmed by
alternative synthesis from OEPCoIII–Cl, Bu3SnH, and
acrolein, according to the method of Fukuzumi [13].
We have found 4b as a byproduct in this alternative
synthesis of 3b. We have recently shown that oxygena-
tion of s-(alkyl)CoIII porphyrins with a secondary alkyl
ligand is promoted under aerobic conditions in the light
and an oxygen atom is inserted into the Co–C bond
[18a]. Since 4b is derived from 3b, hydrogen atom was
abstracted preferentially from the a-CH2 group of
propanal and the total yield of (organo)CoIII por-
phyrins was improved under the present reaction condi-
tions. Non-selective hydrogen atom abstraction from
[13] (8%), TPPCoIII–Et (4a) [14] (8%), and TPPCoIII
–
C(O)Et (5a) (18%) besides TPPCoII (2a) have been
detected as a product mixture by 1H-NMR spec-
troscopy (Scheme 3). A similar reaction of OEPCoIII
–
Cl (1b) with propanal and NaBH4 resulted in much
lower yields of (organo)CoIII porphyrins. Since it has
been known that an acyl radical decomposes to an alkyl
radical and carbon monoxide [2b], formation of 4a in
the above reaction provides strong evidence in support
of generation of a free acyl radical. Thus, it is presumed
that a hydrogen radical derived from homolysis of a
CoIII–H bond abstracts a hydrogen from the CHO
group of propanal, giving rise to 5a. Hydrogen atom
abstraction occurred also from the a-CH2 group of
propanal in this reaction, leading to 3a via an enolate
radical.
2.2. Reaction of CoII porphyrin with aldehyde in the
presence of NaBH4 and molecular oxygen
Whereas CoII porphyrin is a main product in the
above reaction under argon, it can be oxidized to CoIII
and then converted into (organo)CoIII porphyrin. For
example, we have shown that hydrometallation of alke-
nes by using CoII porphyrin and NaBH4 is promoted by
molecular oxygen as well as t-BuOOH [9]. When
OEPCoII (2b) was allowed to react with propanal in the
presence of NaBH4 and molecular oxygen at room
temperature, three CoIII porphyrin complexes,
OEPCoIII–CH(Me)CHO (3b) (33%), OEPCoIII
–
OCH(Me)CHO (4b) (19%) and OEPCoIII–C(O)Et (5b)
(18%) besides 2b have been detected as a product

24
J.-y. Watanabe, J.-i. Setsune / Journal of Organometallic Chemistry 575 (1999) 21–32
spectrum and high-field A2B3 multiplets at l −2.29 (q)
and −1.48 (t). Ethanal, butanal, heptanal, benzalde-
hyde, and 1-naphthaldehyde similarly afforded corre-
sponding s-(acyl)CoIII porphyrins, TPPCoIII–C(O)R
(6a–10a) (Table 1, runs 2–6). The complex 2b also
afforded OEPCoIII–C(O)R (5b–10b) in good yields
(Table 1, runs 7, 12, 14, 16, 18, 20). These acyl com-
plexes were sufficiently stable so that they could be
purified by column chromatography on silica gel with
benzene as an eluent. The carbonyl stretching modes of
5b–10b appear at lower frequency by 2–10 cm−1 than
those of 5a–10a and these CO stretching frequencies of
the s-(acyl)CoIII porphyrins are higher by 10–40 cm−1
than those of the corresponding s-(acyl)RhIII por-
phyrins [19]. These observations are explained in terms
of the more electron-withdrawing effects of Co than Rh
and also of a TPP ligand than an OEP ligand. Al-
though paraformaldehyde under the present redox con-
ditions caused immediate dissolution of 2a, which is
indicative of the occurrence of a reaction, the corre-
sponding s-(formyl)CoIII porphyrin could not be ob-
tained. In the case of rhodium porphyrin, insertion of
carbon monoxide into a RhIII–H bond was demon-
strated, and the resulting s-(formyl)RhIII porphyrin,
OEPRhIII–CHO, was reported to decompose in 24 h in
degassed benzene [20]. Rapid decomposition of a cobalt
analogue, even if it is formed, would take place due to
a smaller bonding energy of a Co–C bond than a
Rh–C bond [21].
Scheme 5.
aldehyde occurred by using CoII and NaBH4 in the
presence of oxygen as well as by using CoIII and NaBH4
in the absence of oxygen.
2.3. Reaction of CoII porphyrin with aldehyde in the
presence of NaBH4 and t-BuOOH
Reaction of 2a with propanal (86 equivalents) in the
presence of NaBH4 (30 equivalents) and t-BuOOH
(three equivalents) in a mixture of benzene–methanol
gave 5a in
a 99% yield (Scheme 5). The s-
(propanoyl)CoIII structure of 5a is consistent with a
carbonyl stretching vibration at 1762 cm−1 in the IR
Table 1
The reaction of CoII porphyrin (2a and 2b) with aldehyde (RCHO) in the presence of t-BuOOHa
Run
CoII porphyrin
Aldehyde
Conditions
Product
Yield (%)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
2a
2a
2a
2a
2a
2a
2b
2b
2b
2b
2b
2b
2b
2b
2b
2b
2b
2b
2b
2b
2b
2b
Propanal
Ethanal
Butanal
Heptanal
Benzaldehyde
1-Naphthaldehyde
Propanal
Propanal
Propanal
Propanal
Propanal
Ethanal
Ethanal
Butanal
Butanal
Heptanal
Heptanal
NaBH4/C6H6–MeOH/Ar
NaBH4/C6H6–MeOH/Ar
NaBH4/C6H6–MeOH/Ar
NaBH4/C6H6–MeOH/Ar
NaBH4/C6H6–MeOH/Ar
NaBH4/C6H6–MeOH/Ar
NaBH4/C6H6–MeOH/Ar
Methylhydroquinone/C6H6/Ar
C6H6/Ar
CH2Cl2/Ar
CH2Cl2/Air
NaBH4/C6H6–MeOH/Ar
CH2Cl2/Air
NaBH4/C6H6–MeOH/Ar
C6H6/Ar
NaBH4/C6H6–MeOH/Ar
C6H6/Ar
NaBH4/C6H6–MeOH/Ar
C6H6/Ar
NaBH4/C6H6–MeOH/Ar
C6H6/Ar
C6H6/Ar
5a
6a
7a
8a
9a
10a
5b
–
5b
5b
5b
6b
6b
7b
7b
8b
8b
9b
9b
10b
11b
12b
99
56
96
92
90
98
95
0
76
84
42
65
61
89
66
83
45
78
60
98
82
72
Benzaldehyde
Benzaldehyde
1-Naphthaldehyde
Acrolein
Citronellal
a PorCoII/RCHO/t-BuOOH/NaBH4=0.08/2.4/0.24/2.3 mmol in 15.5 ml of C6H6–MeOH (30:1) or PorCoII/RCHO/t-BuOOH=0.08/2.4/0.24
mmol in 15 ml of solvent.

J.-y. Watanabe, J.-i. Setsune / Journal of Organometallic Chemistry 575 (1999) 21–32
25
We have shown that metallation of tetrahydrofuran
(THF) with CoII porphyrin proceeds through the ab-
straction of a hydrogen radical from the a-carbon of
THF probably by the action of a hydroxyl radical or a
t-butoxyl radical generated under the same reaction
conditions as the present case [10]. Since it is well
known that acyl radicals are readily produced from
aldehydes by the peroxide-induced hydrogen atom ab-
straction [22], the clean formation of s-(acyl)CoIII com-
plexes suggests that a (hydrido)CoIII intermediate does
not play a key role in the presence of t-BuOOH.
2.4. Reaction of CoII porphyrin with aldehyde and
t-BuOOH
According to the Wayland’s paper that OEPRhIII–H
reacts with aldehyde to generate s-(hydroxyalkyl)RhIII
porphyrin [12], there is a possibility that a transient
(hydrido)CoIII complex (OEPCoIII–H) reacts with alde-
hyde to generate s-(hydroxyalkyl)CoIII porphyrin and
it is then oxidized by t-BuOOH to give s-(acyl)CoIII
porphyrin. When 2b was reacted with propanal and
t-BuOOH under argon, 5b was obtained in a 76% yield
in benzene and in an 84% yield in dichloromethane
(Table 1, runs 9 and 10). The yield of 5b decreased to
42% when the reaction was carried out under air (Table
1, run 11). Similarly, ethanal, butanal, heptanal, ben-
zaldehyde, acrolein, and citronellal afforded the corre-
sponding s-(acyl)CoIII complexes in moderate yields
even in the absence of NaBH4 (Table 1, runs 13, 15, 17,
19, 21, 22). Therefore, (hydrido)CoIII porphyrin does
not take part in the formation of s-(acyl)CoIII por-
phyrins under the reaction conditions which contain
NaBH4 and t-BuOOH. It has been shown that acrolein
is hydrometallated at the CꢀC bond under the reaction
conditions where TPPCoIII–H seems to be generated by
the combination of TPPCoIII–Cl and Bu3SnH [13].
This s-(1-formylethyl)CoIII porphyrin 3b was not de-
tected, but s-(acyl)CoIII porphyrin 11b was isolated in
an 82% yield (Table 1, run 21). This means that a
hydridocobalt species does not take place in the forma-
tion of s-(acyl)CoIII porphyrins irrespective of whether
NaBH4 is present or not. Since methylhydroquinone
which is a radical scavenger has completely inhibited
the generation of 5b (Table 1, run 8), a radical species
should be a key intermediate in the formation of s-
(acyl)CoIII porphyrins. Thus, CoII porphyrin plays a
key role as an acyl radical trapping agent.
Scheme 6.
PorCoIII–C(O)R (Scheme 6, Eq. (3)). Since GLC analy-
sis indicated that aldehyde was not oxidized by t-
BuOOH in the absence of PorCoII, PorCoII catalyzes
the redox reaction between aldehyde and t-BuOOH.
This results in effective generation of an acyl radical
followed by the combination of PorCoII with an acyl
radical. Using 1,4-cyclohexadiene as a substitute for
aldehyde in the absence of NaBH4 did not afford the
corresponding (organo)CoIII porphyrin in spite of
rather weaker C–H bonds of the allylic substrates
(bond dissociation energies: 87.3 kcal mol−1 for ac-
etaldehyde, 73.0 kcal mol−1 for 1,4-cyclohexadiene
[23]). The difference in the reactivity between allylic
compounds and aldehydes towards dehydrometallation
with cobalt porphyrin can be explained by the pre-
sumption that s-(acetyl)CoIII porphyrins are much
more
porphyrins.
stable
than
s-(cyclohexa-2,5-dienyl)CoIII
This reaction sequence from Eqs. (1)–(3) means that
two equivalents of PorCoII are converted into one
equivalent each of PorCoIII–OH and PorCoIII–C(O)R
by the action of one equivalent of t-BuOOH. There-
fore, NaBH4 helps improve the yield of s-(acyl)CoIII
porphyrins by reducing PorCoIII–OH to PorCoII, al-
though ca. 70% of benzaldehyde, for example, was
converted to benzyl alcohol by NaBH4 under these
reaction conditions. Since s-(acyl)CoIII porphyrins were
formed in the yields greater than 50% even in the
absence of NaBH4, there must be another mechanism
by which PorCoIII–OH is converted to PorCoII. This is
explained in terms of the generation of a (alkylper-
oxy)CoIII complex (Scheme 6, Eq. (4)) and its decompo-
sition to PorCoII, t-butoxyl radical and molecular
oxygen (Scheme 6, Eq. (5)), as is shown for the reaction
of (salen)CoIII–OH with t-BuOOH [24]. Thus, the 1:1
reaction of PorCoIII–OH and t-BuOOH leads to s-
(acyl)CoIII porphyrin by way of acyl radical which is
generated by the reaction of t-butoxyl radical and
These experimental facts suggest the following reac-
tion sequence. It is considered that a t-butoxyl radical
and PorCoIII–OH are generated through the one-elec-
tron redox reaction between PorCoII and t-BuOOH
(Scheme 6, Eq. (1)). Then, a t-butoxyl radical would
attack on aldehyde to give t-butanol and an acyl radi-
cal (Scheme 6, Eq. (2)). The latter immediately under-
goes radical coupling with PorCoII leading to

26
J.-y. Watanabe, J.-i. Setsune / Journal of Organometallic Chemistry 575 (1999) 21–32
lective hydrogen abstraction from aldehyde to generate
both an acyl radical and an enolate radical.
aldehyde (Scheme 6, Eq. (2)). The total stoichiometry
of the reaction of PorCoII and t-BuOOH in the pres-
ence of excess aldehyde according to the above mecha-
nism is consistent with the observation that one
equivalent of t-BuOOH was sufficient to get a good
yield (82%) of 5a starting from 2a, as shown in Table 2.
On the other hand, two equivalents of t-BuOOH are
required to reach the maximum yield (68%) of 5a if
starting from 1a. Bruce and co-workers showed that
PorCoIII–Cl is oxidized by t-BuOOH to give rise to
2.5. Intramolecular cyclization of aldehyde with a C–C
multiple bond by combination of CoII porphyrin and
t-BuOOH
When three equivalents of t-BuOOH were added to a
mixture of 2a and 2-allyloxy-1-naphthaldehyde in ben-
zene under argon at ambient temperature, the conver-
sion of 2a into (organo)CoIII porphyrin was clearly
indicated by the dissolution of 2a upon addition of
t-BuOOH. The (organo)CoIII porphyrin 13a with a
3-(4-oxo-5,6-benzochromanyl)methyl group as an axial
ligand was obtained in an 81% yield. The structure of
the axial organo group of 13a was determined on the
basis of the AA%BCC% coupling pattern for the signals
(l −4.43, −3.97, −3.30, −0.34, 1.25) due to the
Por+ CoIII–Cl(OH) and a t-butoxyl radical (Scheme 6,
’
Eq. (6)) [25]. The monitoring UV–vis spectral change
III
indicated that OEP+ Co (ClO4)2 (397 nm) was re-
’
duced immediately by aldehyde to give OEPCoIII(ClO4)
(409 nm). Therefore, Por+ CoIII–Cl(OH) would be re-
’
duced by an excess of aldehyde to regenerate PorCoIII
–
Cl (Scheme 6, Eq. (7)). On the other hand, a t-butoxyl
radical would attack aldehyde to give t-butanol and an
acyl radical (Scheme 6, Eq. (2)). This acyl radical would
not only undergo radical coupling with PorCoII
(Scheme 6, Eq. (3)) but also reduce PorCoIII–Cl to give
PorCoII and acyl chloride (Scheme 6, Eq. (8)). In fact,
carboxylic acid derived from the corresponding acyl
chloride was detected by 1H-NMR analysis of the
reaction mixture started from PorCoIII–Cl [26],
whereas it was not detected in the reaction mixture
started from PorCoII. This reaction sequence (Scheme
6, Eqs. (2), (6)–(8)) means that PorCoIII–Cl is con-
verted into PorCoII by the action of one equivalent of
t-BuOOH if excess aldehyde is present. This is consis-
tent with the observation that two equivalents of t-
BuOOH are required to reach the maximum yield of 5a
from 1a.
1
–CH2CHCH2– unit bonded to CoIII in the H-NMR
1
(Fig. 1) and H-1H-COSY (Fig. 2) spectrum. The signal
at l −4.43 is assigned to the methine proton because it
is coupled to the other four signals. Since the porphyrin
ring current effect on the 1H-chemical shift of the
b-carbon position relative to CoIII is generally the
highest [9,10], this methine proton is thought to be at
the b-carbon position. The two signals at l −3.97 and
−3.30 are assigned to the protons of the axial a-carbon
position, and the two signals at much lower magnetic
fields (l −0.34 and 1.25) are assigned to those of the
axial g-carbon position according to the strength of the
ring current effect of porphyrin [9,10]. These data indi-
cate that CoIII is bonded not to the methine carbon but
to the methylene carbon in the –CH2CHCH2– moiety.
The carbonyl stretching mode of 13a was observed at
1666 cm−1 in the IR spectrum. This frequency is
On the other hand, a hydridocobalt species should be
responsible for the formation of the product 3a or 3b
derived from hydrogen abstraction from the a-CH2
group of aldehyde. That is, hydrogen radical produced
by the homolysis of a CoIII–H bond may cause non-se-
similar to that of 4-oxo-5,6-benzochroman (1672 cm−1
[27].
)
The structure of 13a is consistent with the following
reaction sequence. The acyl radical center is generated
and then adds across a C–C double bond intramolecu-
larly to give a six-membered ring. The resulting primary
alkyl radical is trapped by CoII porphyrin (Scheme 7).
Although s-(acyl)CoIII porphyrins are given in good
yields in dichloromethane as well as in benzene (see
Table 1, runs 9 and 10), the yield of 13a decreased to
31% in dichloromethane (Table 3). This is probably
because a generated primary alkyl radical is not only
trapped by CoII porphyrin but is reactive enough to
abstract chlorine or hydrogen from dichloromethane.
Reaction of 2b with 2-allyloxy-1-naphthaldehyde also
afforded (organo)CoIII porphyrin 13b in a 71% yield.
When 2-allyloxybenzaldehyde, 2-allylbenzaldehyde, and
N-allylpyrrole-2-carboxaldehyde were used in the same
fashion, the corresponding (organo)CoIII porphyrins
Table 2
Effect of the amount of t-BuOOH in the reaction of Co porphyrin
with propanala
Co porphyrin
TPPCoII–Cl
t-BuOOH (equivalents)
Yield (%) of 5a
0.5
1
2
19
25
68
66
3
TPPCoII
0.5
1
2
36
82
80
81
3
a TPPCo/RCHO=0.08/2.4 mmol in 15 ml of C6H6.

J.-y. Watanabe, J.-i. Setsune / Journal of Organometallic Chemistry 575 (1999) 21–32
27
Fig. 1. 1H-NMR spectrum of 13a in CDCl3. Signals due to TMS, H2O, CH2Cl2, CHCl3 are indicated by asterisks. Some impurities such as 2a
are observed at 8.7, 9.7, and 9.9 ppm.
1
1
the H-1H-COSY experiment. These H-NMR data are
consistent with the CoIII–CH2–CHX–CH2Y connec-
tivity which results from acyl radical cyclization. The
acyl radical cyclization of 2-allylbenzaldehyde and N-
allylpyrrole-2-carboxaldehyde did not lead to a six-
membered ring with the CoIII–CH(CH2X)–CH2Y
connectivity such as in 15b% (Scheme 8). To the con-
trary, Branchaud reported that acid catalyzed cycliza-
with a cyclized axial alkyl ligand, 14b, 15b, and 16b,
were formed in 59, 59, and 90% yield, respectively,
without generation of s-(acyl)CoIII porphyrins
1
(Schemes 7–9). The H-NMR signals due to the axial
organo group of 13b–16b were assigned according to
Fig. 2. 1H-1H-COSY spectrum of 13a in CDCl3.
Scheme 7.

28
J.-y. Watanabe, J.-i. Setsune / Journal of Organometallic Chemistry 575 (1999) 21–32
Table 3
Yield of 13a in the reaction of 2a with 2-allyloxy-1-naphthaldehydea
Solvent
Atmosphere
Yield (%) of 13a
C6H6
CH2Cl2
C6H6
Argon
Argon
Air
81
31
46
19
CH2Cl2
Air
a 2a/2-allyloxy-1-naphthaldehyde/t-BuOOH=0.08/2.4/0.24 mmol
in 15 ml of solvent.
tion of (2-hydroxy-4-N-pyrrolylbutyl)cobaloxime led to
a six-membered ring with the CoIII–CH(CH2X)–CH2Y
connectivity [28]. While a strained 5-membered ring
transition state is not preferred in the intramolecular
electrophilic substitution of the pyrrole ring, the re-
gioselectivity in the present acyl radical cyclization is
governed by a probability factor favoring 5-membered
ring formation.
Similar acyl radical cyclization occurred in the case
of N-(3-butenyl)pyrrole-2-carboxaldehyde to give
1
(organo)CoIII porphyrins 17b in a 7% yield. The H-
NMR signals (l −5.01, −4.67, −3.90, −3.05, −
1.81, 1.18, 2.00) due to the axial organo group of 17b
are consistent with a six-membered ring which consists
of CoIII–CH2–CHX–CH2CH2Y connectivity. Because,
the methine proton is assigned to the signal at the
highest magnetic field (l −5.01) characteristic of the
b-carbon position with respect to Co. However, this
reaction was accompanied by the formation of the
corresponding s-(acyl)CoIII porphyrin 18b in a 21%
yield (Scheme 9). Since these products could not be
separated because they decomposed during column
chromatography on silica gel, the yields were deter-
Scheme 9.
1
product (Scheme 9). Whereas the H-NMR signals due
to the b-pyrrole protons of the axial ligand of 16a, 16b,
and 17b appear at 5.5–6.2 ppm, one of those signals in
18b and 19a is shifted to a higher magnetic field (0.47
ppm in 18b; 1.06 ppm in 19a) due to the porphyrin ring
current effect. This indicates that the b-pyrrole proton
is forced to come close to the porphyrin plane owing to
the steric repulsion between the pyrrole N-substituent
and the porphyrin plane.
Photolysis of 13b by a xenon lamp afforded 3-
methyl-4-oxo-5,6-benzochrom-2-en (20) in an 87% yield
(Scheme 10). The methyl and the olefin protons of 20
appear at l 2.13 and 7.86, respectively, in the 1H-NMR.
The carbonyl stretching mode of 20 at 1644 cm−1 in
the IR spectrum is shifted to the lower frequency by
20–30 cm−1 than that of 4-oxo-5,6-benzochroman or
13b. These data are consistent with the enone structure
of 20. It is considered that b-elimination of CoIII–H
species from 13b gives 2b and an enone intermediate
(A) and the latter rearranges to 20 because of its
relative thermodynamic stability.
1
mined by H-NMR spectrum of the mixture. On the
other hand, N-methallylpyrrole-2-carboxaldehyde gave
s-(acyl)CoIII porphyrin 19a in a 90% yield as a single
In conclusion, acyl radicals are readily produced
from aldehydes through the reaction with Co porphyrin
and t-BuOOH. The generated acyl radicals were di-
rectly captured by CoII porphyrin or underwent radical
cyclization before the coupling with CoII porphyrin.
The yields and the reaction pathway in the formation of
s-(acyl)CoIII porphyrins are dependent on the oxida-
tion state of the starting Co porphyrin and the amount
of t-BuOOH.
Scheme 8.

J.-y. Watanabe, J.-i. Setsune / Journal of Organometallic Chemistry 575 (1999) 21–32
29
3. Experimental section
added through a syringe. Then, the reaction mixture
was stirred for 10 min. The resulting mixture was
filtered to remove the remaining NaBH4 and 2a. The
filtrate was evaporated with a rotary evaporator, and
washed with methanol. Yields of s-(alkyl)CoIII com-
plexes were determined on the basis of their signal
intensities in the 1H-NMR: 3a=8%, 4a=8%, 5a=
18%.
1H-NMR (250 MHz) spectra were recorded on a
Bruker AC-250 spectrometer in CDCl3, and chemical
shifts were referenced with respect to tetramethylsilane
as an internal standard. UV–visible spectra were mea-
sured on a Shimadzu UV-240 spectrophotometer. IR
spectra were obtained in a KBr disk on a Hitachi
I-2000 spectrophotometer. Elemental analyses were per-
formed by a Yanagimoto Model Mt-3 CHN analyzer.
Low-resolution mass spectra were measured on a Shi-
madzu GCMS-QP2000A spectrometer with a direct-in-
let method. Gel permeation chromatography was
performed by a JAI LC-908 system. Benzene and
dichloromethane were distilled from CaH2 and
methanol was distilled simply before use. Aldehydes
were obtained from commercial suppliers and used as
received. TPPCoII [29], OEPCoII [30], TPPCoIII–Cl
[31], OEPCoIII–Cl [31] were synthesized according to
the literature methods.
3.2. Reaction of CoII porphyrin with propanal in the
coexistent system of O2 and NaBH4
In a 50-ml Erlenmeyer flask, 2b (23.8 mg, 0.040
mmol), NaBH4 (45.3 mg, 1.3 mmol) and a magnetic
stirrer were placed. To the flask, benzene (15 ml),
methanol (0.5 ml) and propanal (0.5 ml) were added
and this reaction mixture were stirred for 1 h. The
mixture was filtered to remove the remaining NaBH4
and 2b. The filtrate was evaporated with a rotary
evaporator, and the residue was washed with methanol
to give a product mixture (21.2 mg). Yields of 3b, 4b
and 5b were determined on the basis of their signal
3.1. Reaction of CoIII porphyrin with propanal in the
presence of NaBH4 under an argon atmosphere
1
intensities in the H-NMR. 3b=33%, 4b=19%, 5b=
18%, and 2b was recovered.
3b: 1H-NMR (CDCl3):
l
−5.93 (d, 3H,
In
a two necked round-bottomed 50-ml flask
CH(Me)CHO), −3.57 (dq, 1H, CH(Me)CHO), 2.53
(d, 1H, CH(Me)CHO), 1.87 (t, 24H, CH2CH3), 4.12
(m, 16H, CH2CH3), 10.21 (s, 4H, meso-H).
equipped with a septum and a two-way cock connected
to an argon line, 1a (23.2 mg, 0.033 mmol), NaBH4
(44.4 mg, 1.2 mmol) and a magnetic stirrer were placed
under an argon atmosphere. To the flask, benzene (15
ml) and methanol (0.5 ml), propanal (0.5 ml) were
4b: 1H–NMR (CDCl3):
l
−3.98 (dq, 1H,
OCH(Me)CHO), −1.20 (d, 3H, OCH(Me)CHO), 6.33
(d, 1H, OCH(Me)CHO), 1.85 (t, 24H, CH2CH3), 3.96
(m, 16H, CH2CH3), 10.64 (s, 4H, meso-H).
Spectroscopic and analytical data of 5b are described
later.
3.3. Reaction of CoII porphyrin with aldehydes in the
coexistent system of t-BuOOH and NaBH4
3.3.1. General procedure
In
a two necked round-bottomed 50-ml flask
equipped with a septum and a two-way cock connected
to an argon line, 2a (ca. 0.08 mmol), NaBH4 (ca. 2.3
mmol), and a magnetic stirrer were placed under an
argon atmosphere. To the flask, benzene (15 ml),
methanol (0.5 ml) and aldehyde (0.5 ml) were added
through a syringe. Then, t-BuOOH (10 ml) was added
through a micro syringe every 5 min (three times). The
mixture was filtered to remove the remaining NaBH4
and 2a. The filtrate was evaporated under vacuum, and
the residue was washed with methanol. The crude
product was purified by column chromatography on
silica gel with benzene as an eluent and recrystallized
from dichloromethane-methanol.
5a: 1H-NMR (CDCl3):
l
−2.29 (q, 2H,
COCH2CH3), −1.48 (t, 3H, COCH2CH3), 7.74 (m,
12H, m and p-Ph–H), 8.11 (br, 8H, o-Ph–H), 8.93 (s,
Scheme 10.

30
J.-y. Watanabe, J.-i. Setsune / Journal of Organometallic Chemistry 575 (1999) 21–32
8H, b-Py–H). IR (KBr), cm−1: 1762 [w(CꢀO)]. UV–vis
(CH2Cl2), nm: 408.0, 530.0. Anal. Calc. for
C47H33N4OCo: C, 77.46; H, 4.56; N, 7.69. Found: C,
76.78; H, 4.62; N, 7.62.
for C38H47N4OCo: C, 71.91; H, 7.46; N, 8.83. Found:
C, 72.06; H, 7.67; N, 8.71.
7b: 1H-NMR (CDCl3):
l
−2.92 (t, 2H,
COCH2CH2CH3), −1.40 (m, 2H, COCH2CH2CH3),
−1.30 (t, 3H, COCH2CH2CH3), 1.86 (t, 24H,
CH2CH3), 3.92–4.12 (m, 16H, CH2CH3), 10.06 (s, 4H,
meso-H). IR (KBr), cm−1: 1738 [w(CꢀO)]. UV–vis
(CH2Cl2), nm: 389.5, 518.0, 552.5. Anal. Calc. for
C40H51N4OCo · 0.5H2O: C, 71.51; H, 7.80; N, 8.34.
Found: C, 71.74; H, 7.64; N,8.37.
1
6a: H-NMR (CDCl3): l −2.20 (s, 3H, COCH3),
7.70–7.72 (m, 12H, m and p-Ph–H), 8.10 (br, 8H,
o-Ph–H), 8.84 (s, 8H, b-Py–H). IR (KBr), cm−1: 1732
[w(CꢀO)]. UV–vis (CH2Cl2), nm: 408.0, 530.0. Anal.
Calc. for C46H31N4OCo: C, 77.30; H, 4.37; N, 7.84.
Found: C, 77.43; H, 4.59; N, 7.87.
8b: 1H-NMR (CDCl3): l −2.90 (t, 2H, COCH2CH2-
CH2CH2CH2CH3), −1.48 (m, 2H, COCH2CH2CH2-
CH2CH2CH3), −1.07 (m, 2H, COCH2CH2CH2CH2-
CH2CH3), −0.17 (m, 2H, COCH2CH2CH2CH2CH2-
CH3), 0.39–0.49 (m, 5H, COCH2CH2CH2CH2-
CH2CH3), 1.86 (t, 24H, CH2CH3), 4.02 (m, 16H,
7a: 1H-NMR (CDCl3):
l
−2.32 (t, 2H,
COCH2CH2CH3), −1.10 (m, 2H, COCH2CH2CH3),
−1.06 (t, 3H, COCH2CH2CH3), 7.72 (m, 12H, m and
p-Ph–H), 8.10 (br, 8H, o-Ph–H), 8.83 (s, 8H, b-Py–
H). IR (KBr), cm−1: 1742 [w(CꢀO)]. UV–vis (CH2Cl2),
nm: 408.0, 530.0. Anal. Calc. for C48H35N4OCo·0.5
H2O: C, 76.69; H, 4.83; N, 7.45. Found: C, 76.72; H,
4.78; N, 7.18.
CH2CH3), 10.06 (s, 4H, meso-H). IR (KBr), cm−1
:
1730 [w(CꢀO)]. UV–vis (CH2Cl2), nm: 389.5, 518.0,
552.5. Anal. Calc. for C43H57N4OCo·0.5H2O: C, 72.34;
H, 8.19; N, 7.85. Found: C, 72.40; H, 8.44; N,7.76.
9b: 1H-NMR (CDCl3): l 1.84 (t, 24H, CH2CH3),
2.13 (d, 2H, COPh, o-H), 3.98 (q, 16H, CH2CH3), 5.75
(t, 2H, COPh, m-H), 6.23 (t, 1H, COPh, p-H), 9.95 (s,
4H, meso-H). IR (KBr), cm−1: 1720 [w(CꢀO)], UV–vis
(CH2Cl2), nm: 389.5, 518.0, 552.5. Anal. Calc. for
C43H49N4OCo·0.5H2O: C, 73.17; H, 7.14; N, 7.94.
Found: C, 73.54; H, 7.25; N, 7.98.
8a: 1H-NMR (CDCl3): l −2.32 (t, 2H, COCH2CH2-
CH2CH2CH2CH3), −1.16 (m, 2H, COCH2CH2CH2-
CH2CH2CH3), −0.77 (m, 2H, COCH2CH2CH2-
CH2CH2CH3), 0.00 (m, 2H, COCH2CH2CH2CH2-
CH2CH3), 0.45–0.60 (m, 5H, COCH2CH2CH2CH2-
CH2CH3), 7.67–7.77 (m, 12H, m- and p-Ph–H), 8.10
(br, 8H, o-Ph–H), 8.83 (s, 8H, b-Py–H). IR (KBr),
cm−1: 1734 [w(CꢀO)]. UV–vis (CH2Cl2), nm: 408.0,
530.0. Anal. Calc. for C51H41N4OCo·0.5H2O: C, 77.16;
H, 5.33; N, 7.06. Found: C, 77.24; H, 5.51; N, 6.96.
1
10b: H-NMR (CDCl3): l 1.59 (d, 1H, 2-Nap–H),
1.80 (t, 24H, CH2CH3), 2.75 (d, 1H, 8-Nap–H), 3.93
(q, 16H, CH2CH3), 5.95 (t, 1H, 3-Nap–H), 6.38 (t, 1H,
7-Nap–H), 6.77 (d, 1H, 4-Nap–H), 6.83(t, 1H, 6-Nap–
H), 7.00 (d, 1H, 5-Nap–H), 10.00 (s, 4H, meso-H). IR
(KBr), cm−1: 1704 [w(CꢀO)]. UV–vis (CH2Cl2), nm:
391.0, 517.0, 552.5. Anal. Calc. for C47H51N4OCo: C,
75.58; H, 6.88; N, 7.50. Found: C, 75.52; H, 7.08; N,
7.65.
1
9a: H-NMR (CDCl3): l 2.61 (d, 2H, COPh, o-H),
6.03 (t, 2H, COPh, m-H), 6.50 (t, 1H, COPh, p-H),
7.67–7.73 (m, 12H, m- and p-Ph–H), 8.06 (br, 8H,
o-Ph–H), 8.79 (s, 8H, b-Py–H). IR (KBr), cm−1: 1728
[w(CꢀO)]. UV–vis (CH2Cl2), nm: 408.0, 528.0. Anal.
Calc. for C51H33N4OCo·0.5H2O: C, 77.95; H, 4.36; N,
7.13. Found: C, 77.82; H, 4..74; N, 7.12.
1
10a: H-NMR (CDCl3): l 2.04 (d, 1H, 2-Nap–H),
3.14 (d, 1H, 8-Nap–H), 6.13 (t, 1H, 3-Nap–H), 6.52 (t,
1H, 7-Nap–H), 6.94 (t, 1H, 6-Nap–H), 7.00 (d, 1H,
4-Nap–H), 7.19 (d, 1H, 5-Nap–H), 7.71 (m, 12H, m-
and p-Ph–H), 8.00 (br, 8H, o-Ph–H), 8.79 (s, 8H,
b-Py–H). IR (KBr), cm−1: 1714 [w(CꢀO)]. UV–vis
(CH2Cl2), nm: 408.0, 528.0. Anal. Calc. for
C55H35N4OCo·2.5H2O: C, 75.76; H, 4.62; N, 6.43.
Found: C, 75.64; H, 4.67; N, 6.44.
3.4. Reaction of CoII porphyrin with aldehydes in the
presence of t-BuOOH
3.4.1. General procedure
In
a two necked round-bottomed 50-ml flask
equipped with a septum and a two-way cock connected
to an argon line, 2a (ca. 0.08 mmol) and a magnetic
stirrer were placed under an argon atmosphere. To the
flask, benzene (15 ml), methanol (0.5 ml) and aldehyde
(0.5 ml) were added through a syringe. Then, t-BuOOH
(10 ml) was added through a micro syringe every 5 min
(three times). The mixture was filtered to remove the
remaining 2a. The filtrate was evaporated under vac-
uum, and the residue was washed with methanol. The
crude product was purified by column chromatography
on silica gel with benzene as an eluent and recrystallized
from dichloromethane–methanol.
5b: 1H-NMR (CDCl3):
l
−2.90 (q, 2H,
COCH2CH3), −1.78 (t, 3H, COCH2CH3), 1.87 (t,
24H, CH2CH3), 3.91–4.14 (m, 16H, CH2CH3), 10.07
(s, 4H, meso-H). IR (KBr), cm−1: 1756 [w(CꢀO)]. UV–
vis (CH2Cl2), nm: 389.5, 518.0, 552.5. Anal. Calc. for
C39H49N4OCo: C, 72.20; H, 7.61; N, 8.64. Found: C,
72.45; H, 7.90; N, 8.65.
1
6b: H-NMR (CDCl3): l −2.75 (s, 3H, COCH3),
1.87 (t, 24H, CH2CH3), 3.92–4.12 (m, 16H, CH2CH3),
10.07 (s, 4H, meso-H). IR (KBr), cm−1: 1730 [w(CꢀO)].
UV–vis (CH2Cl2), nm: 389.5, 518.0, 552.5. Anal. Calc.

J.-y. Watanabe, J.-i. Setsune / Journal of Organometallic Chemistry 575 (1999) 21–32
31
1
11a: H-NMR (CDCl3): l 0.66 (dd, 1H, COCH=
12H, m- and p-Ph–H), 8.09 (br, 8H, o-Ph–H), 8.41 (d,
1H, Naph–H), 8.84 (s, 8H, b-Py–H). IR (KBr), cm−1
:
CH2) (Jtrans=17.0 Hz, Jcis=10.4 Hz), 2.29 (dd, 1H,
COCH=CH2, cis) (Jgem=1.3 Hz), 2.64 (dd, 1H,
COCH=CH2, trans), 7.67–7.77 (m, 12H, m- and p-
Ph–H), 8.11 (br, 8H, o-Ph–H), 8.84 (s, 8H, b-Py–H).
IR (KBr), cm−1: 1714 [w(CꢀO)]. UV–vis (CH2Cl2), nm:
408.0, 530.0. Anal. Calc. for C47H31N4OCo·H2O: C,
75.80; H, 4.47; N, 7.53. Found: C, 75.81; H, 4.71; N,
7.51.
1666 [w(CꢀO)]. UV–vis (CH2Cl2), nm: 408.0, 530.0.
Anal. Calc. for C58H39N4Co·3H2O: C, 76.98; H, 5.01;
N, 6.19. Found: C, 76.70; H, 5.04; N, 6.23.
1
13b: H-NMR (CDCl3): −4.95 (m, 1H, axial b-H),
−4.54, −4.00 (dd×2, 1H×2, axial a-H), −0.70,
0.53 (dd×2, 1H×2, axial g-H), 1.86 (t, 24H,
CH2CH3), 4.01 (m, 16H, CH2CH3), 6.12 (d, 1H,
Naph–H), 7.01 (m, 1H, Naph–H), 7.05 (m, 1H,
Naph–H), 7.27 (d, 2H, Naph–H), 8.27 (d, 1H, Naph–
H), 10.09 (s, 4H, meso-H). IR (KBr), cm−1: 1668
[w(CꢀO)]. UV–vis (CH2Cl2), nm: 389.5, 518.0, 552.5.
Anal. Calc. for C50H55N4O2Co · H2O: C, 73.15; H, 7.00;
N, 6.83. Found: C, 73.39; H, 6.88; N, 6.97.
1
11b: H-NMR (CDCl3): l −0.03 (dd, 1H, COCH=
CH2) (Jtrans=17.0 Hz, Jcis=10.3 Hz), 1.86 (dd, 1H,
COCH=CH2, cis) (Jgem=1.6 Hz), 2.24 (dd, 1H,
COCH=CH2, trans), 1.79 (t, 24H, CH2CH3), 3.95 (m,
16H, CH2CH3), 10.00 (s, 4H, meso-H). IR (KBr),
cm−1: 1708 [w(CꢀO)]. UV–vis (CH2Cl2), nm: 389.5,
518.0, 552.5. Anal. Calc. for C39H49N4OCo·0.5H2O: C,
71.21; H, 7.66; N, 8.52. Found: C, 71.66; H, 7.56; N,
8.69.
1
14b: H-NMR (CDCl3): −5.28 (m, 1H, axial b-H),
−4.62 (t, 1H, axial a-H), −4.03 (d, 1H, axial a-H),
−0.55, 0.17 (dd×2, 1H×2, axial g-H), 1.85 (t, 24H,
CH2CH3), 4.01 (m, 16H, CH2CH3), 6.04 (d, 1H, Ph–
H), 6.29 (t, 1H, Ph–H), 6.69 (dd, 1H, Ph–H), 6.84 (t,
12b: 1H-NMR (CDCl3): l −3.21, −2.84 (dd×2,
1H×2, COCH2–), −1.51 (d, 3H, COCH2CHCH3–),
−1.08 (m, 1H, COCH2CH(CH3)CH2–), −0.90 (m,
1H, Ph–H), 10.09 (s, 4H, meso-H). IR (KBr), cm−1
:
1686 [w(CꢀO)]. UV–vis (CH2Cl2), nm: 389.5, 518.0,
552.5. Anal. Calc. for C46H53N4Co·2.5H2O: C, 72.13;
H, 7.63; N, 7.32. Found: C, 72.05; H, 7.50; N, 7.28.
1H,
COCH2CH–),
0.51
(m,
2H,
COCH2CH(CH3)CH2CH2–), 1.09, 1.37 (s×2, 3H×2,
COCH2CH(CH3)CH2CH2CHꢀC(CH3)2), 1.86 (t, 24H,
CH2CH3), 4.02 (m, 16H, CH2CH3), 4.23 (t, 1H,
COCH2CH(CH3)CH2CH2CHꢀC(CH3)2), 10.05 (s, 4H,
meso-H). IR (KBr), cm−1: 1722 [w(CꢀO)]. UV–vis
(CH2Cl2), nm: 389.5, 518.0, 552.5. Anal. Calc. for
C46H61N4OCo · 1.5H2O: C, 71.57; H, 8.36; N, 7.26.
Found: C, 71.79; H, 8.35; N, 7.28.
1
15b: H-NMR (CDCl3): −4.78 (m, 1H, axial b-H),
−4.59, −3.74 (dd×2, 1H×2, axial a-H), −2.68,
−0.89 (dd×2, 1H×2, axial g-H), 1.89 (m, 24H,
CH2CH3), 4.01 (m, 16H, CH2CH3), 6.38 (d, 1H, Ph–
H), 6.60 (m, 2H, Ph–H), 6.92 (m, 1H, Ph–H), 10.09 (s,
4H, meso-H). IR (KBr), cm−1: 1708 [w(CꢀO)]. UV–vis
(CH2Cl2), nm: 389.5, 518.0, 552.5. Anal.Calc. for
C46H53N4OCo·H2O: C, 73.19; H, 7.34; N, 7.42. Found:
C, 72.63; H, 7.32; N, 7.28.
3.5. Reaction of CoIII porphyrin with propanal in the
presence of t-BuOOH
16a: 1H-NMR (CDCl3): −4.04, −3.03 (dd×2,
1H×2, axial a-H), −3.53 (m, 1H, axial b-H), −1.22
(dd, 1H, axial g-H), 0.45 (t, 1H, axial g-H), 5.86 (d, 1H,
Py–H), 5.92 (m, 1H, Py–H), 6.13 (m, 1H, Py–H), 7.73
(m, 12H, m, p-Ph–H), 8.09 (br, 8H, o-Ph–H), 8.85 (m,
8H, b-Py–H). IR (KBr), cm−1: 1686 [w(CꢀO)]. UV–vis
(CH2Cl2), nm: 408.0, 530.0. Anal. Calc. for
C52H36N5OCo·0.2H2O: C, 77.16; H, 4.53; N, 8.65.
Found: C, 77.23; H, 4.35; N, 8.54.
In
a two necked round-bottomed 50-ml flask
equipped with a septum and a two-way cock connected
to an argon line, 1a (42.3 mg, 0.060 mmol) and a
magnetic stirrer were placed under an argon atmo-
sphere. To the flask, benzene (15 ml) and propanal (0.5
ml) were added through a syringe. Then, t-BuOOH (10
ml) was added through a micro syringe every 5 min
(three times). The resulting mixture was evaporated
with a rotary evaporator, and the residue was washed
with methanol. 5a was given in a 68% yield.
16b: 1H-NMR (CDCl3): −4.58, −3.77 (dd×2,
1H×2, axial a-H), −4.13 (m, 1H, axial b-H), −1.76
(dd, 1H, axial g-H), 0.07 (t, 1H, axial g-H), 1.88 (m,
24H, CH2CH3), 4.02 (m, 16H, CH2CH3), 5.69 (m, 1H,
Py–H), 5.76 (m, 1H, Py–H), 5.93 (m, 1H, Py–H),
10.10 (s, 4H, meso-H). IR (KBr), cm−1: 1698 [w(CꢀO)].
UV–vis (CH2Cl2), nm: 389.5, 518.0, 552.5. Anal. Calc.
for C44H52N5OCo·H2O: C, 71.04; H, 7.32; N, 9.42.
Found: C, 70.79; H, 7.55; N, 9.13.
3.6. Intramolecular cyclization of aldehyde with C–C
multiple bond by combination of CoII porphyrin and
t-BuOOH
The reactions were performed according to the
method of Section 3.4.
1
17b: H-NMR (CDCl3): l −5.01 (m, 1H, axial b-H),
1
13a: H-NMR (CDCl3): l −4.43 (m, 1H, axial b-H),
−4.67, −3.90 (dd×2, 1H×2, axial a-H), −3.05,
−1.81 (m×2, 1H×2, axial g-H), 1.18, 2.00 (m×2,
1H×2, axial l-H), 1.88 (m, 24H, CH2CH3), 4.00 (m,
16H, CH2CH3), 5.53 (m, 1H, Py–H), 5.90 (m, 2H,
Py–H), 10.04 (s, 4H, meso-H).
−3.97, −3.30 (dd×2, 1H×2, axial a-H), −0.34,
1.25 (dd×2, 1H×2, axial g-H), 6.27 (d, 1H, Naph–
H), 7.04 (t, 1H, Naph–H), 7.14 (t, 1H, Naph–H), 7.32
(d, 1H, Naph–H), 7.36 (d, 1H, Naph–H), 7.71 (m,

32
J.-y. Watanabe, J.-i. Setsune / Journal of Organometallic Chemistry 575 (1999) 21–32
1
J. Org. Chem. 53 (1988) 463.
18b: H-NMR (CDCl3): l 0.47 (dd, 1H, Py–H), 1.73
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(t, 2H, N–CH2), 1.85 (t, 24H, CH2CH3), 3.99 (m, 16H,
CH2CH3), 4.2–4.7 (m, 6H, N–CH2CH2CHꢀCH2 and
Py–H), 5.01 (t, 1H, Py–H), 9.97 (s, 4H, meso-H).
19a: 1H-NMR (CDCl3):
l
0.51 (s, 3H, N–
CH2C(Me)ꢀCH2), 1.06 (dd, 1H, Py–H), 2.30 (s, N–
CH2C(Me)ꢀCH2), 3.03, 3.94 (s×2, 1H×2,
N–CH2C(Me)ꢀCH2), 4.90 (dd, 1H, Py–H), 5.32 (t, 1H,
Py–H), 7.70 (m, 12H, m-, p-Ph–H), 8.07 (m, 8H,
o-Ph–H), 8.79 (m, 8H, b-Py–H). IR (KBr), cm−1: 1682
[w(CꢀO)]. UV–vis (CH2Cl2), nm: 408.0, 530.0. Anal.Calc.
for C53H38N5OCo: C, 77.64; H, 4.67; N, 8.54. Found: C,
77.79; H, 4.74; N, 8.75.
3.7. Photolysis of 13b by a xenon lamp
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A solution of 13b (97.0 mg) in deoxygenated benzene
(20 ml) was irradiated using a xenon lamp for 4 h under
argon. The solution was filtered to remove the generated
OEPCoII. The filtrate was evaporated under vacuum, and
the residue was separated by gel permeation chromatog-
raphy to give 20 (22.0 mg, 87%).
1
20: H-NMR (CDCl3): l 2.12 (s, 3H, CH3), 7.47 (d,
1H, Naph–H), 7.62 (t, 1H, Naph–H), 7.77 (t, 1H,
Naph–H), 7.86 (s, 1H, O–CHꢀ), 7.89 (d, 1H, Naph–H),
8.05 (d, 1H, Naph–H), 10.10 (d, 1H, Naph–H). IR
(KBr), cm−1: 1644 [w(CꢀO)]. Anal. Calc. for C14H10O2:
C, 79.98; H, 4.79. Found: C, 79.68; H, 4.78. Mass (EI),
m/z: 210 (M+).
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Acknowledgements
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This work was partly supported by a Grant-in-Aid for
Scientific Research from the Ministry of Education,
Science, Sports, and Culture, Japan. We are grateful to
Professor S. Fukuzumi (Osaka University) for providing
us a detailed synthetic procedure for 3b. We thank Ms.
M. Nishinaka (Kobe University) for microanalysis.
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Griller, R.A. Rossi, A.B. Pierini, S.M. Palacios, E.G. Janzen,
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t-BuOOH (three equivalents) in benzene under argon for 15 min,
formation of p-anisic acid (ca. 0.7 equivalents) in the reaction
mixture was confirmed by the 1H-NMR spectrum.
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