The intermolecular Pauson-Khand reaction of meso-substituted porphyrins

Article abstract of DOI:10.1002/ejoc.200800488

The intermolecular Pauson-Khand reaction is often limited by the poor reactivity and selectivity of simple alkenes. Here we expanded the range of reagents to simple alkenyl- and alkynyl-substituted porphyrins. The two expected regioisomers could be obtained in a combined yield of up to 72%. In addition, use of the Pauson-Khand reaction provides a simple and novel pathway for the preparation of porphyrin dimers in a nearly quantitative yield. Wiley-VCH Verlag GmbH & Co. KGaA, 2008.

Full text of DOI:10.1002/ejoc.200800488

FULL PAPER
DOI: 10.1002/ejoc.200800488
The Intermolecular Pauson–Khand Reaction of meso-Substituted Porphyrins
Sabine Horn[a] and Mathias O. Senge*[a]
Keywords: Porphyrins / Pauson–Khand reaction / Intermolecular reactions / Cyclizations / Porphyrin dimers
The intermolecular Pauson–Khand reaction is often limited
by the poor reactivity and selectivity of simple alkenes. Here
we expanded the range of reagents to simple alkenyl- and
addition, use of the Pauson–Khand reaction provides a sim-
ple and novel pathway for the preparation of porphyrin di-
mers in a nearly quantitative yield.
alkynyl-substituted porphyrins. The two expected regioiso- (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
mers could be obtained in a combined yield of up to 72%. In
Germany, 2008)
Hence, the intermolecular Pauson–Khand reaction has
been restricted to strained alkenes, such as norbornene and
norbornadiene, and there is a continuing need to widen the
scope of this reaction. As part of our ongoing studies on
the development of new reactions for the functionalisation
of porphyrins[9] we have undertaken an initial study of the
Pauson–Khand reaction of porphyrins.
The most common pathways for cyclisation reactions at
the porphyrin ring system involve Diels–Alder and 1,3-di-
polar cycloaddition reactions. These synthetic methods
have mostly been applied to the β-position of the aromatic
system.[10] Just recently, the Huisgen 1,3-dipolar cycload-
dition for the formation of heterocyclic five-membered rings
has been carried out at substituents located at the meso-
position.[11] Herein, we report an alternative pathway for
cyclisation reactions involving meso-substituents. We de-
scribe the extension of the intermolecular Pauson–Khand
reaction to simple alkene- as well as alkyne-substituted por-
phyrins and illustrate its utility for the preparation of por-
phyrin dimers in high yields.
Introduction
The range of applications for porphyrins continues to
grow, and the development of new synthetic routes presents
a crucial step in several application areas. While design
pathways using total synthesis of novel porphyrins continue
to be developed, they often require numerous steps. There-
fore, the functionalisation of simple porphyrin substituents
offers a complementary and perhaps more wide-ranging ap-
proach that may be applied to various substitution patterns
of different tetrapyrroles. Ideally, these new synthetic meth-
ods involve simple starting materials, one reaction step and
high yields without the formation of any by-products.
The Pauson–Khand reaction has these features and has
to the best of our knowledge not been used with porphyrins
previously. Since its discovery by Pauson and Khand in
1971[1] this reaction has remained the most flexible and
atom-economical method for the synthesis of five-mem-
bered rings.[2] It involves the reaction of an alkene, an al-
kyne and a carbon monoxide molecule in a transition-
metal-mediated coupling to form a cyclopentenone system.
The reaction mechanism proposed by Magnus and co-
workers[3,4] has been widely accepted, and many five-mem-
bered carbocycles thus prepared have been shown to exhibit
biological activity.[5,6]
Results and Discussion
For studies in analogy to the investigations of Pauson
and co-workers on the reactivity of styrene[12] we prepared
[5,10,15-tris(4-methylphenyl)-20-vinylporphyrinato]nickel-
(II) (4). The synthesis of this compound involved Suzuki
cross-coupling[9b] of 5-bromo-10,15,20-tris(4-methylphen-
yl)porphyrin (2), obtained by bromination[13] of 1 with vi-
nylboronic acid pinacol ester to afford 3, followed by metal-
lation with nickel(II) acetate.[14] The vinylporphyrin 4 was
treated with phenylacetylene and Co2(CO)8 in THF under
heating at reflux for 4 d. Unfortunately, the only product
that could be isolated was the formyl-substituted porphyrin
analogue 5 in 11% yield. Most likely the double bond of
compound 4 was too close to the porphyrin macrocycle and
consequently sterically too hindered to take part in the re-
action. Therefore, the allyl-substituted porphyrin 6[9b] with
Although the first intramolecular version of the Pauson–
Khand reaction was reported by Schore[7] only ten years
after the initial discovery, it has received most attention.[8]
This variation is thermodynamically more favored, and the
formation of regioisomers can be excluded. On the other
hand, the intermolecular version appears to be synthetically
more demanding as has been limited by the poor reactivity
and selectivity of simple alkenes. Sterically hindered alkenes
are disfavored, and in many cases yields are only moderate.
[a] School of Chemistry, SFI Tetrapyrrole Laboratory, Trinity Col-
lege Dublin,
Dublin 2, Ireland
Fax: +353-1-8968537
E-mail: sengem@tcd.ie
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S. Horn, M. O. Senge
FULL PAPER
an extra carbon atom between the porphyrin moiety and 5,10,15-trihexylporphyrin (8), bromination[13] of 8 to afford
the double bond was chosen as starting material. Indeed, 9 followed by reaction with allylboronic acid pinacol ester
the Pauson–Khand reaction of 6 with phenylacetylene pro- under Suzuki cross-coupling conditions[12] to afford 10 and
ceeded cleanly, and the two products 22 and 23 could be subsequent metallation to the nickel(II) complex 11.[14] The
obtained in 19 and 34% yield, respectively (Scheme 1). The Pauson–Khand reaction of 11 led to the formation of prod-
reaction could also be carried out with the (porphyrinato)- ucts 26 and 27, albeit in lower yields (14 and 19%, respec-
zinc(II) complex 7 to afford compounds 24 and 25 in lower tively) compared to the meso-arylporphyrins.
yields.
Various possibilities have been reported to improve the
yield of the Pauson–Khand reaction;[15] notably replace-
ment of Co by a different transition metal or use of addi-
tives. Hence, Mo(CO)6 was used instead of Co2(CO)8 in the
reaction of 6 with phenylacetylene.[16] However, no reaction
was observed, and only starting material was recovered.
Use of N-methylmorpholine N-oxide as an additive gave the
same result.[17] Addition of molecular sieves (4 Å) resulted
in the formation of compounds 22 and 23 without improve-
ment of the yield.[18] As no starting material could be reco-
vered or detected by TLC in the initial Pauson–Khand reac-
tion of 6, we assumed that the remaining equivalents of
allylporphyrin were inserted in the (alkyne)Co2(CO)6 com-
plex I, as shown in the reaction mechanism (Scheme 2).
Scheme 1. Pauson–Khand reaction of allylporphyrins. Reaction
conditions: (i) Co2(CO)8, THF, ∆, overnight; (ii) Co2(CO)8, THF,
Schlenk tube, 3 d. [a] Reaction carried out under condition (ii).
Next, we examined whether the reaction is also appli-
cable to alkyl-substituted porphyrins by using (5-allyl-
10,15,20-trihexylporphyrinato)nickel(II) (11) as test com-
pound. Its synthesis involved the nucleophilic substitution
Scheme 2. Postulated mechanism for the Pauson–Khand reaction.
of 5,15-dihexylporphyrin with n-hexyllithium to obtain the RL = larger group, RS = smaller group.
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Intermolecular Pauson–Khand Reaction of meso-Substituted Porphyrins
However, the (alkyne)Co2(CO)5(alkenylporphyrin) complex zinc(II) belongs to one of the metals that induce the highest
II could not be isolated.[19] In an attempt to “force” this negative charge in the porphyrin periphery.[25] Again, no
intermediate to proceed in the reaction, the reaction of product was obtained when compounds 15 and 18 were
compound 6 with phenylacetylene and Co2(CO)8 was again treated with norbornene under Pauson–Khand conditions.
carried out in THF, however, this time in a Schlenk tube. Attempts to isolate the presumed complex I failed. Possibly,
The solution was degassed, and the reaction mixture was the alkyne group is sterically too hindered by the macro-
heated to 80 °C until no change was observed by TLC. In- cycle for the reaction to proceed, similar to the situation
deed, the yield could be improved, and products 22 and 23 found with the vinylporphyrins. It appears that the mecha-
were obtained after 3 d in 39% and 33%, respectively.
nism of the Pauson–Khand reaction seems to be sterically
Compounds 22 and 23 are the two regioisomers expected quite demanding, which is conceivable when imagining
from the reaction mechanism, in analogy to compounds III complexes I and II 3-dimensionally.
and IV in Scheme 2 with the larger residue RL of the alkyne
Consequently, a spacer was introduced between the por-
partner in 2-position of the cyclopentenone. As the smaller phyrin macrocycle and the terminal alkyne. The most
alkyne residue is RS = H, complex II is non-selective and straightforward procedure to synthesise such a compound
the residue originating from the alkene partner can add to was the introduction of a 4-ethynylphenyl substituent by
the 4-position or, alternatively, the 5-position of the cyclo- nucleophilic reaction of 5,15-bis(4-methylphenyl)porphyrin
pentenone. The ratio of the two regioisomers from this reac- with the organolithium analogue[26] to afford the 4-ethyn-
tion is approximately 1:1, which is typical for reactions of ylphenyl-substituted porphyrin 19. Thus, compounds 20
terminal alkynes with monosubstituted alkenes.[20] How- and 21 were prepared through metallation and treated with
ever, it is also known that the regioselectivity can be quite norbornene to obtain the Pauson–Khand products 28 and
random. When the reaction was stopped after 1 d, the main 29 in very good yields (Scheme 3).
isomer obtained was the one according to IV, whereas after
3 d the isomer according to III was obtained in a slightly
higher yield. This kind of reversal of regioselectivity has
previously been described for promoters,[21] different sol-
vents[22] and thermolyses, but the reason for this unexpected
selectivity remains unclear.[23]
Other alkyne partners were also treated with 6, namely
ethynyltrimethylsilane, hexyne, dimethyl ethylacetylened-
icarboxylate and propargyl toluene-4-sulfonate. Unfortu-
nately, these attempts were unsuccessful.
Next, we investigated the reaction with the porphyrin
bearing the alkyne group by using porphyrin 14 and allyl-
benzene.[24] Preparation of compound 14 involved the syn-
thesis of 12 from 2 by Sonogashira reaction with ethynyltri-
methylsilane, followed by deprotection to afford 13, and
metallation. However, no product was formed by using the
standard Pauson–Khand conditions. This can be related to
the poor reactivity of the alkene partner mentioned above,
as it was found that terminal alkenes usually result in low
yields. It has been shown that insertion of the alkene into
the Co–C bond is the rate-determining reaction step and is
Scheme 3. Pauson–Khand reaction of (ethynylphenyl)porphyrins.
related to the back-donation of electrons from the d-orbit-
als of the cobalt atom to the π*-orbitals of the alkene;[24]
de Bruin et al. showed that the lower the LUMO of the
The regioselectivity of the products with regard to the
alkene, the higher the reactivity and suggested the following cyclopentenone is in agreement with the theoretical expec-
order of reactivity for the thermal version of the Pauson– tation. The larger group of the alkyne partner is located in
Khand reaction: cyclohexene Ͻ cyclopentene Ͻ norbor- the 2-position of the cyclopentenone, and several studies
nene.
have shown the reaction of norbornene to be completely
Hence, cyclohexene, norbornene and compound 6 were exo-face-selective.[27] The yield of the reaction of 20 with
treated with 14; again unsuccessfully. To create a more elec- norbornadiene for the formation of 30 was only moderate.
tron-rich alkyne, the zinc(II) compound 15 and the trialkyl- Possibly the product 30 reacted further with the starting
substituted porphyrin 18 were synthesised. Compound 18 material 20 by a double Pauson–Khand reaction,[28] but the
was prepared by Sonogashira reaction of 9 with ethynyltri- product mixture could not be analysed.
methylsilane to afford 16, followed by deprotection of the
Based on these observations, compound 20 was directly
ethynyl group to give 17 and metallation to 18. Alkyl sub- treated with 30 in an attempt to prepare a porphyrin dimer
stituents on the porphyrin increase the electron density of by the Pauson–Khand reaction. Indeed, the two fractions
the macrocycle due to the electron-donating effect, and obtained were identified as the dimers 31 and 32 in excellent
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S. Horn, M. O. Senge
FULL PAPER
yields of 50% and 47%, respectively (Scheme 4).[28] Com-
pounds 31 and 32 are the two expected regioisomers of the
double Pauson–Khand reaction. The stereochemistry of the
second addition is also known to be exo-selective. The tetra-
cyclic linker unit has been detected previously when the re-
action was carried out with an excess of alkyne.[28] Accord-
ingly, norbornadiene was treated with a two-fold excess of
porphyrin 20. The main product obtained was compound
30; however, the amount of the other fractions was again
shift, multiplicity (s: singlet, d: doublet, dd: doubledoublet, t: trip-
let, m: multiplet, br: broad), coupling constants (J in Hz), integra-
tion and assignment. High resolution mass spectrometry was car-
ried out with a Micromass/Waters Corp., USA liquid chromatog-
raphy time-of-flight spectrometer equipped with an electrospray
source or a MALDI Q TOF Premier MS system. Melting points
were acquired with a Stuart SMP10 melting point apparatus and
are uncorrected. Thin layer chromatography (TLC) was performed
on silica gel 60 F254 (Merck) precoated aluminum sheets.
Chromatography on silica gel was carried out by using a forced
too small for analysis. Hence, the two-step strategy for pro- flow of the indicated solvent system on Fluka Silica Gel 60 (230–
400 mesh). Tetrahydrofuran (THF) and diethyl ether were distilled
from sodium/benzophenone under nitrogen. All commercial chemi-
cals were supplied and used without further purification. Com-
pounds 8[29a] and 15[29b] were prepared as reported previously.
ducing the dimers 31 and 32 is the more promising pathway
and affords the combined products nearly quantitatively.
Synthesis of Starting Materials
5,10,15-Tris(4-methylphenyl)porphyrin (1): A 1-L 3-necked round-
bottom flask was charged with p-bromotoluene (5 g, 29.25 mmol,
14 equiv.) in dry diethyl ether (100 mL) under Ar. n-Butyllithium
(14 mL, 35.1 mmol, 17.2 equiv.) was added dropwise at –70 °C over
30 min. After the addition was complete, the reaction mixture was
warmed to room temp. and was stirred for 1 h (colour change to
white). Next, 5,15-bis(4-methylphenyl)porphyrin (1 g, 2.04 mmol,
1 equiv.) dissolved in THF (500 mL) under Ar and cooled to
–20 °C was added. The combined reaction mixture was stirred at
room temp. for 1 h (colour change to brown), then water (5 mL,
colour change to emerald green) and DDQ (2.1 g, 9.25 mmol,
4 equiv.) were added (colour change to red). After 1 h, the crude
product was filtered through a layer of silica gel and recrystallised
from CH2Cl2/MeOH. The product was obtained as purple crystals
in 1.08 g (1.86 mmol, 91%) yield. Analytical data were as reported
by Lindsey et al.[30]
Scheme 4. Synthesis of porphyrin dimers by double Pauson–Khand
reaction.
5,10,15-Tris(4-methylphenyl)-20-vinylporphyrin (3):
A
50-mL
Conclusions
Schlenk-tube was filled with Ar and charged with 5-bromo-
10,15,20-tris(4-methylphenyl)porphyrin (300 mg, 0.455 mmol,
1 equiv.) in dry THF (50 mL). K3PO4 (2.0 g, 9.1 mmol, 20 equiv.)
was added, and the solution was degassed by three freeze-pump-
thaw cycles and put under Ar again. Vinylboronic acid pinacol es-
ter (0.8 mL, 4.55 mmol, 10 equiv.) and Pd(PPh3)4 (53 mg,
0.0455 mmol, 0.1 equiv.) were added, and the reaction mixture was
heated to 80 °C overnight. Then the solvent was removed under
reduced pressure, and the residue was dissolved in CH2Cl2. The
crude product was washed with a saturated solution of NaHCO3,
water and brine and dried with Na2SO4. Purification was carried
out by dry-loaded column chromatography on silica gel (CH2Cl2/
C6H14, 1:2, v/v). The product was obtained after recrystallisation
from CH2Cl2/MeOH as purple crystals in 144 mg (0.24 mmol,
52%) yield. M.p. Ͼ 300 °C. Rf = 0.43 (CH2Cl2/C6H14, 1:1, v/v). 1H
NMR (400 MHz, CDCl3, 25 °C): δ = –2.67 (br., 2 H, NH), 2.73 (s,
We have shown that the Pauson–Khand reaction offers
an alternative pathway for cyclisation reactions with por-
phyrin substituents in the meso-position. The intermo-
lecular Pauson–Khand reaction is applicable to alkene- as
well as alkyne-substituted porphyrins. Steric considerations
require the reaction centre to be in a certain distance to the
macrocycle, and the reaction is somewhat limited with re-
gard to the non-porphyrin reactants; e. g., allylporphyrins
could serve as the alkene partner to obtain the expected two
regioisomers in a combined yield of up to 72%. Likewise,
(ethynylphenyl)porphyrins were treated with norbornene
and norbornadiene in moderate to high yields. In addition
to expanding the scope of the Pauson–Khand reaction to
technically and medicinally relevant complex heterocycles,
the simple formation of porphyrin dimers through a se-
quential double Pauson–Khand reaction in quantitative
(combined) yield indicates the potential of this method for
the coupling of porphyrin-based units.
3
3 H, C6H4CH3), 2.73 (s, 6 H, C6H4CH3), 6.15 (dd, JH,H = 17.5,
2JH,H = 1.8 Hz, 1 H, CH=CH2), 6.59 (dd, 3JH,H = 11.7, 2J = 1.8 Hz,
3
3
1 H, CH=CH2), 7.57 (d, JH,H = 8.2 Hz, 4 H, HAr), 7.59 (d, JH,H
3
= 7.6 Hz, 2 H, HAr), 8.09 (d, JH,H = 7.6 Hz, 4 H, HAr), 8.12 (d,
3JH,H = 7.6 Hz, 2 H, HAr), 8.84 (s, 4 H, β-H), 8.95 (d, JH,H
=
3
3
3
4.7 Hz, 2 H, β-H), 9.26 (dd, JH,H = 17.0, JH,H = 11.1 Hz, 1 H,
CH=CH2), 9.50 (d, JH,H = 5.3 Hz, 2 H, β-H) ppm. 13C NMR
3
(100.6 MHz, CDCl3, 25 °C): δ = 21.6, 117.0, 120.1, 120.2, 127.3,
127.4, 127.6, 131.1 (br.), 134.5, 137.4, 137.5, 139.2 ppm. UV/Vis
(CH2Cl2): λmax (lg ε) = 421 (6.0), 521 (5.0), 556 (4.9), 596 (4.87),
653 (4.86) nm. HRMS (ES+): calcd. for C43H34N4 [M + H]+
607.2862, found 607.2861.
Experimental Section
1
General Methods: H and 13C NMR spectra were recorded with a
Bruker DPX 400 MHz (400.13 MHz for 1H NMR; 100.61 MHz
for 13C NMR) and/or a Bruker AV 600 MHz (600.13 MHz for H
1
NMR; 150.90 MHz for 13C NMR) NMR spectrometer. Chemical
shifts are reported in ppm. Data are reported as follows: chemical
[5,10,15-Tris(4-methylphenyl)-20-vinylporphyrinato]nickel(II) (4): A
50-mL 2-necked round-bottomed flask was charged with 5,10,15-
4884
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Intermolecular Pauson–Khand Reaction of meso-Substituted Porphyrins
tris(4-methylphenyl)-20-vinylporphyrin (3, 70 mg, 0.116 mmol,
1 equiv.) and Ni(acac)2 (45 mg, 0.174 mmol, 1.5 equiv.) in toluene
(30 mL). The reaction mixture was heated to reflux until comple-
tion (ca. 30 min, TLC control). The solvent was removed under
reduced pressure, and the residue was dissolved in CH2Cl2. The
crude product was filtered through a layer of silica gel and washed
with CH2Cl2. After recrystallisation from CH2Cl2/MeOH, the
product was obtained as dark red needles in 54.6 mg (0.08 mmol,
C3H6CH2CH2CH3), 1.82 (m, 6 H, C2H4CH2C2H4CH3), 2.51 (m, 6
H, CH2CH2C3H6CH3), 4.91 (m, 6 H, CH2C4H8CH3), 9.45 (d,
3JH,H = 5.2 Hz, 2 H, β-H), 9.46 (d, 3JH,H = 5.8 Hz, 2 H, β-H), 9.50
(d, JH,H = 5.2 Hz, 2 H, β-H), 9.67 (d, JH,H = 4.7 Hz, 2 H, β-H)
ppm. 13C NMR (100.6 MHz, CDCl3, 25 °C): δ = 14.2, 22.8, 30.2,
30.3, 31.9, 35.4, 35.8, 38.7, 38.8, 101.1, 119.9, 120.4, 128.7 (br.),
131.9 (br.) ppm. UV/Vis (CH2Cl2): λmax (lg ε) = 420 (6.3), 521 (5.2);
557 (5.2), 602 (5.1), 661 (5.1) nm. HRMS (ES+): calcd. for
3
3
71%) yield. M.p. 212 °C. Rf = 0.85 (CH2Cl2/C6H14, 1:1, v/v). 1H C38H49BrN4 [M + H]+ 641.3219, found 641.3227.
NMR (400 MHz, CDCl3, 25 °C): δ = 2.65 (s, 3 H, C6H4CH3), 2.66
5-Allyl-10,15,20-trihexylporphyrin (10): A 50-mL Schlenk-tube was
filled with Ar and charged with 5-bromo-10,15,20-trihexylporphy-
rin (9, 300 mg, 0.468 mmol, 1 equiv.) in dry THF (50 mL). K3PO4
(2.0 g, 9.36 mmol, 20 equiv.) was added, and the solution was de-
gassed by three freeze-pump-thaw cycles and put under Ar again.
Allylboronic acid pinacol ester (0.9 mL, 4.68 mmol, 10 equiv.) and
Pd(PPh3)4 (54 mg, 0.0468 mmol, 0.1 equiv.) were added, and the
reaction mixture was heated to 80 °C overnight. Then the solvent
was removed under reduced pressure, and the residue was dissolved
in CH2Cl2. The crude product was washed with a saturated solu-
tion of NaHCO3, water and brine and dried with Na2SO4. Purifica-
tion was carried out by dry-loaded column chromatography on sil-
ica gel (CH2Cl2/C6H14, 1:2, v/v). After recrystallisation from
CH2Cl2/MeOH, the product was obtained in 170 mg (0.28 mmol,
60%) yield as purple crystals. M.p. 114 °C; Rf = 0.49 (CH2Cl2/
C6H14, 1:1, v/v). 1H NMR (400 MHz, CDCl3, 25 °C): δ = –2.59
3
2
(s, 6 H, C6H4CH3), 5.64 (dd, JH,H = 17.5, JH,H = 1.8 Hz, 1 H,
CH=CH2), 5.68 (dd, 3JH,H = 17.5, 2JH,H = 1.8 Hz, 1 H, CH=CH2 ),
7.48 (d, JH,H = 7.6 Hz, 4 H, HAr), 7.50 (d, JH,H = 7.6 Hz, 2 H,
HAr), 7.88 (d, JH,H = 5.9 Hz, 4 H, HAr), 7.89 (d, JH,H = 5.9 Hz,
2 H, HAr), 8.71 (d, JH,H = 4.7 Hz, 2 H, β-H), 8.72 (d, JH,H
3
3
3
3
3
3
=
3
5.3 Hz, 2 H, β-H), 8.84 (d, JH,H = 5.3 Hz, 2 H, β-H), 8.96 (dd,
3JH,H = 17.0, JH,H = 11.0 Hz, 1 H, CH=CH2), 9.35 (d, JH,H
=
3
3
4.7 Hz, 2 H, β-H) ppm. 13C NMR (100.6 MHz, CDCl3, 25 °C): δ
= 21.0, 114.5, 118.2, 127.2, 127.6, 130.9, 131.6, 131.7, 132.1, 133.0,
133.1, 135.4, 136.9, 137.3, 140.8, 141.5, 141.9 ppm. UV/Vis
(CH2Cl2): λmax (lg ε) = 420 (5.5), 535 (4.7) nm. HRMS (ES+):
calcd. for C43H32N4Ni [M + H]+ 663.2059, found 663.2031.
5,10,15-Trihexylporphyrin (8): A 1-L 3-necked round-bottom flask
was filled with Ar and charged with 5,15-dihexylporphyrin
(940 mg, 1.967 mmol, 1 equiv.) in dry THF (500 mL). The solution
was cooled to –78 °C, and n-hexyllithium (5.13 mL, 11.8 mmol,
6 equiv.) was added dropwise over 20 min. After complete addition,
the reaction mixture was stirred at –78 °C for 15 min, before it was
warmed to room temp. (colour change to brown). After 1 h, water
(4 mL, colour change to emerald green) and DDQ (2.7 g,
11.8 mmol, 6 equiv.) were added (colour change to red). Triethyl-
amine (3 mL) was added after an additional 1 h of stirring, and the
3
(br. s, 2 H, NH), 0.97 (t, JH,H = 7.3 Hz, 6 H, C5H10CH3), 0.99 (t,
3JH,H = 7.6 Hz, 3 H, C5H10CH3), 1.43 (m, 6 H, C4H8CH2CH3 ),
1.54 (m, 6 H, C3H6CH2CH2CH3), 1.85 (m, 6 H, C2H4CH2C2H4-
CH3), 2.54 (m,
6 H, CH2CH2C3H6CH3), 4.95 (m, 6 H,
CH2C4H8CH3), 5.18 (d, 3JH,H = 17.0 Hz, 1 H, CH2CH=CH2), 5.25
3
3
(d, JH,H = 9.9 Hz, 1 H, CH2CH=CH2), 5.74 (d, JH,H = 5.3 Hz, 2
3
H, CH2CH=CH2), 6.88 (m, 1 H, CH2CH=CH2), 9.48 (d, JH,H
=
4.8 Hz, 4 H, β-H), 9.50 (d, JH,H = 5.2 Hz, 4 H, β-H) ppm. 13C
NMR (100.6 MHz, CDCl3, 25 °C): δ = 14.2, 22.8, 30.4, 31.9, 35.5,
35.6, 38.8, 39.0, 113.9, 115.9, 118.6, 118.9, 126.6 (br.), 128.2 (br.),
141.7 ppm. UV/Vis (CH2Cl2): λmax (lg ε) = 419 (5.6), 520 (4.6), 555
(4.5), 600 (4.5), 659 (4.5) nm. HRMS (ES+): calcd. for C41H54N4
[M + H]+ 603.4427, found 603.4423.
3
crude product was filtered through
a layer of silica. After
recrystallisation from CH2Cl2/MeOH, the product was obtained in
290 mg (0.516 mmol, 26%) yield as purple needles. M.p. 142 °C. Rf
= 0.22 (CH2Cl2/C6H14, 1:2, v/v). 1H NMR (400 MHz, CDCl3,
3
25 °C): δ = –2.84 (br. s, 2 H, NH), 0.97 (t, JH,H = 7.3 Hz, 6 H,
3
C5H10CH3), 0.99 (t, JH,H = 7.6 Hz, 3 H, C5H10CH3), 1.44 (m, 6
H, C4H8CH2CH3), 1.56 (m, 6 H, C3H6CH2CH2CH3), 1.84 (m, 6
H, C2H4CH2C2H4CH3), 2.56 (m, 6 H, CH2CH2C3H6CH3), 4.99 (t,
[5-Allyl-10,15,20-trihexylporphyrinato]nickel(II) (11): A 50-mL 2-
necked round-bottom flask was charged with 5-allyl-10,15,20-tri-
hexylporphyrin (10, 170 mg, 0.28 mmol, 1 equiv.) and Ni(acac)2
(108 mg, 0.42 mmol, 1.5 equiv.) in toluene (50 mL). The reaction
mixture was heated to reflux until completion (ca. 30 min, TLC
control). The solvent was removed under reduced pressure, and the
residue was dissolved in CH2Cl2. The crude product was filtered
through a layer of silica gel and washed with CH2Cl2. The product
was obtained in 132 mg (0.20 mmol, 71%) yield as a red low-melt-
ing solid. Rf = 0.67 (CH2Cl2/C6H14, 1:2, v/v). 1H NMR (400 MHz,
3
3JH,H = 8.2 Hz, 4 H, CH2C4H8CH3), 5.08 (t, JH,H = 8.2 Hz, 2 H,
3
3
CH2C4H8CH3), 9.31 (d, JH,H = 4.7 Hz, 2 H, β-H), 9.52 (d, JH,H
3
= 4.7 Hz, 2 H, β-H), 9.55 (d, JH,H = 4.7 Hz, 2 H, β-H), 9.62 (d,
3JH,H = 4.7 Hz, 2 H, β-H) ppm. 13C NMR (150.9 MHz, CDCl3,
25 °C): δ = 13.9, 22.6, 30.1, 30.2, 31.7, 31.8, 34.9, 35.3, 36.1, 38.5,
38.7, 38.9, 102.8, 118.5, 119.8, 119.9, 120.2, 127.7, 128.1, 128.5,
131.1, 145.1 (br.), 146.6 (br.) ppm. UV/Vis (CH2Cl2): λmax (lg ε) =
412 (5.5), 512 (4.6), 545 (4.5), 591 (4.4), 647 (4.4) nm. HRMS
(ES+): calcd. for C38H50N4 [M + H]+ 563.4114, found 563.4124.
3
CDCl3, 25 °C): δ = 0.93 (t, JH,H = 7.3 Hz, 6 H, C5H10CH3),
3
0.95 (t, JH,H
= 7.5 Hz, 3 H, C5H10CH3), 1.34 (m, 6 H,
5-Bromo-10,15,20-trihexylporphyrin (9): A 250-mL round-bottom
flask was charged with 5,10,15-trihexylporphyrin (8, 222 mg,
0.39 mmol, 1 equiv.) in chloroform (100 mL). N-Bromosuccinimide
(NBS, 83 mg, 0.468 mmol, 1.2 equiv.) and pyridine (0.2 mL) were
added, and the reaction mixture was stirred at room temp. until
completion (ca. 30 min, TLC control). The solvent was removed
under reduced pressure, and the residue was dissolved in CH2Cl2.
The crude product was filtered through a layer of silica gel and
washed with CH2Cl2. After recrystallisation from CH2Cl2/MeOH,
the product was obtained in 220 mg (0.34 mmol, 88%) yield as
brown needles. M.p. 133 °C; Rf = 0.41 (CH2Cl2/C6H14, 1:2, v/v).
1H NMR (400 MHz, CDCl3, 25 °C ): δ = –2.66 (br. s, 2 H, NH),
C4H8CH2CH3 ), 1.43 (m, 6 H, C3H6CH2CH2CH3), 1.59 (m, 6 H,
C2H4CH2C2H4CH3), 2.26 (m, 6 H, CH2CH2C3H6CH3), 4.48 (m, 6
3
H, CH2C4H8CH3), 5.18 (d, JH,H = 5.9 Hz, 2 H, CH2CH=CH2),
3
3
5.23 (d, JH,H = 10.0 Hz, 1 H, CH2CH=CH2), 5.31 (d, JH,H
=
17.5 Hz, 1 H, CH2CH=CH2), 6.71 (m, 1 H, CH2CH=CH2), 9.25
3
3
(d, JH,H = 4.8 Hz, 4 H, β-H), 9.26 (d, JH,H = 5.2 Hz, 4 H, β-H)
ppm. 13C NMR (100.6 MHz, CDCl3, 25 °C): δ = 14.2, 22.7, 30.1,
31.8, 33.9, 37.3, 37.9, 112.6, 115.6, 117.1, 117.3, 129.7, 129.8, 129.9,
141.0, 141.1, 141.2 ppm. UV/Vis (CH2Cl2): λmax (lg ε) = 420 (5.4),
539 (4.5), 570 (4.3) nm. HRMS (ES+): calcd. for C41H52N4Ni [M
+ H]+ 659.3624, found 659.3593.
3
3
0.97 (t, JH,H = 7.3 Hz, 6 H, C5H10CH3), 0.99 (t, JH,H = 7.6 Hz, 5,10,15-Tris(4-methylphenyl)-20-[(trimethylsilyl)ethynyl]porphyrin
3 H, C5H10CH3), 1.43 (m, 6 H, C4H8CH2CH3), 1.54 (m, 6 H, (12): A 100-mL Schlenk-tube was filled with Ar and charged with
Eur. J. Org. Chem. 2008, 4881–4890
© 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
4885

S. Horn, M. O. Senge
FULL PAPER
5-bromo-10,15,20-tris(4-methylphenyl)porphyrin (200 mg, 96.9, 119.8, 120.8, 127.6, 127.7, 131.4, 132.1, 132.5, 133.3, 133.5,
0.30 mmol; 1 equiv.) in dry THF/triethylamine (60 mL, 1:3, v/v). 133.6, 137.5, 137.6, 137.7, 142.5, 142.6, 143.4, 145.1 ppm. UV/Vis
The solution was degassed by five freeze-pump-thaw cycles and put
under Ar again. Ethynyltrimethylsilane (0.4 mL, 3.0 mmol,
10 equiv.), copper(I) iodide (14 mg, 0.075 mmol, 0.25 equiv.) and
Pd(PPh3)2Cl2 (25 mg, 0.036 mmol, 0.12 equiv.) were added, and the
reaction mixture was stirred at room temp. overnight. Then CH2Cl2
(60 mL) was added, and the solution was washed with water and
dried with Na2SO4. After purification by dry-loaded column
chromatography on silica gel (CH2Cl2/C6H14, 1:2, v/v), the product
was obtained in 146 mg (0.216 mmol, 72%) yield as purple crystals.
M.p. Ͼ 300 °C. Rf = 0.41 (CH2Cl2/C6H14, 1:2, v/v). 1H NMR
(400 MHz, CDCl3, 25 °C): δ = –2.40 (br. s, 2 H, NH), 0.63 (s, 9 H,
SiCH3), 2.72 (s, 3 H, C6H4CH3), 2.74 (s, 6 H, C6H4CH3), 7.56 (d,
3JH,H = 8.2 Hz, 2 H, HAr), 7.59 (d, 3JH,H = 8.2 Hz, 4 H, HAr), 8.07
(CH2Cl2): λmax (lg ε) = 423 (5.5), 537 (4.7), 571 (4.6) nm. HRMS
(ES+): calcd. for C43H30N4Ni [M + H]+ 661.1902, found 661.1870.
10,15,20-Trihexyl-5-[(trimethylsilyl)ethynyl]porphyrin (16): A 50-
mL Schlenk-tube was filled with Ar and charged with 5-bromo-
10,15,20-trihexylporphyrin (9, 100 mg, 0.156 mmol, 1 equiv.) in dry
THF/triethylamine (40 mL, 3:1, v/v). The solution was degassed by
five freeze-pump-thaw cycles and put under Ar again. Ethynyltri-
methylsilane (0.2 mL, 1.56 mmol, 10 equiv.), copper(I) iodide
(8 mg, 0.039 mmol, 0.25 equiv.) and Pd(PPh3)2Cl2 (13 mg,
0.019 mmol, 0.12 equiv.) were added, and the reaction mixture was
stirred at room temp. overnight. Then CH2Cl2 (30 mL) was added,
and the solution was washed with water and dried with Na2SO4.
The product was obtained as purple crystals in 69 mg (0.10 mmol,
67%) yield. M.p. 119 °C. Rf = 0.71 (CH2Cl2/C6H14, 1:1, v/v). 1H
NMR (400 MHz, CDCl3, 25 °C): δ = –2.40 (br. s, 2 H, NH), 0.68
3
3
(d, JH,H = 8.2 Hz, 2 H, HAr), 8.10 (d, JH,H = 8.2 Hz, 4 H, HAr),
3
8.80 (s, 4 H, β-H), 8.93 (d, JH,H = 4.7 Hz, 2 H, β-H), 9.66 (d,
3JH,H = 4.7 Hz, 2 H, β-H) ppm. 13C NMR (100.6 MHz, CDCl3,
25 °C): δ = 0.4, 21.6, 29.7, 98.7, 101.7, 107.2, 121.1, 121.2, 127.4,
127.5, 130.6 (br.), 131.9 (br.), 134.4, 134.5, 137.5 ppm. UV/Vis
(CH2Cl2): λmax (lg ε) = 429 (5.7), 529 (4.6), 568 (4.6), 604 (4.4), 657
(4.5) nm. HRMS (ES+): calcd. for C46H40N4Si [M + H]+ 677.3101,
found 677.3095.
3
(s, 9 H, SiCH3), 0.97 (t, JH,H = 7.3 Hz, 6 H, C5H10CH3), 0.99 (t,
3JH,H = 7.6 Hz, 3 H, C5H10CH3), 1.43 (m, 6 H, C4H8CH2CH3),
1 . 5 3 ( m , 6 H , C 3 H 6 C H 2 C H 2 C H 3 ) , 1 . 7 9 ( m , 6 H ,
C2H4CH2C2H4CH3), 2.47 (m, 6 H, CH2CH2C3H6CH3), 4.81 (t,
3
3JH,H = 8.1 Hz, 4 H, CH2C4H8CH3), 4.86 (t, JH,H = 8.1 Hz, 2 H,
3
3
CH2C4H8CH3), 9.33 (d, JH,H = 5.1 Hz, 2 H, β-H), 9.38 (d, JH,H
3
{5,10,15-Tris(4-methylphenyl)-20-[(trimethylsilyl)ethynyl]-
porphyrinato}nickel(II) (13): A 50-mL 2-necked round-bottomed
flask was charged with 5,10,15-tris(4-methylphenyl)-20-[(trimethyl-
silyl)ethynyl]porphyrin (12, 100 mg, 0.148 mmol; 1 eqiv.) and Ni-
(acac)2 (57 mg, 0.222 mmol, 1.5 equiv.) in toluene (30 mL). The re-
action mixture was heated to reflux until completion (ca. 30 min,
TLC control). The solvent was removed under reduced pressure,
and the residue was dissolved in CH2Cl2. The crude product was
filtered through a layer of silica gel and washed with CH2Cl2. After
the solvent was removed under reduced pressure, the product was
obtained in a quantitative yield (107 mg, 0.146 mmol, 99%) as pur-
ple crystals. M.p. Ͼ 300 °C. Rf = 0.86 (CH2Cl2/C6H14, 1:1, v/v). 1H
NMR (400 MHz, CDCl3, 25 °C): δ = 0.56 (s, 9 H, SiCH3), 2.65 (s,
= 4.2 Hz, 2 H, β-H), 9.40 (d, JH,H = 4.2 Hz, 2 H, β-H), 9.65 (d,
3JH,H = 4.8 Hz, 2 H, β-H) ppm. 13C NMR (100.6 MHz, CDCl3,
25 °C): δ = 0.5, 14.2, 22.8, 30.3, 30.4, 31.9, 36.3, 37.0, 38.6, 38.9,
96.8, 100.7, 107.6, 120.3, 121.8, 128.6 (br.), 130.7 (br.) ppm. UV/
Vis (CH2Cl2): λmax (lg ε) = 428 (5.8), 532 (4.7), 571 (4.8), 611 (4.6),
669 (4.7) nm. HRMS (ES+): calcd. for C43H58N4Si [M + H]+
659.4509, found 659.4494.
{10,15,20-Trihexyl-5-[(trimethylsilyl)ethynyl]porphyrinato}nickel(II)
(17): A 50-mL 2-necked round-bottom flask was charged with
10,15,20-trihexyl-5-[(trimethylsilyl)ethynyl]porphyrin (16, 44 mg,
0.066 mmol, 1 equiv.) and Ni(acac)2 (25 mg, 0.1 mmol, 1.5 equiv.)
in toluene (20 mL). The reaction mixture was heated to reflux until
completion (ca. 2 h, TLC control). The solvent was removed under
reduced pressure, and the residue was dissolved in CH2Cl2. The
crude product was filtered through a layer of silica gel and washed
with CH2Cl2. After the solvent was removed under reduced pres-
sure, the product was obtained in 46 mg (0.064 mmol, 98%) yield
3
3 H, C6H4CH3), 2.68 (s, 6 H, C6H4CH3), 7.49 (d, JH,H = 8.0 Hz,
3
3
4 H, HAr), 7.51 (d, JH,H = 8.0 Hz, 2 H, HAr), 7.88 (d, JH,H
=
4.8 Hz, 4 H, HAr), 7.90 (d, 3JH,H = 5.2 Hz, 2 H, HAr), 8.69 (d, 3JH,H
= 5.3 Hz, 2 H, β-H), 8.71 (d, JH,H = 4.7 Hz, 2 H, β-H), 8.83 (d,
3
3JH,H = 4.7 Hz, 2 H, β-H), 9.51 (d, 3JH,H = 4.7 Hz, 2 H, β-H) ppm.
13C NMR (100.6 MHz, CDCl3, 25 °C): δ = 1.1, 29.7, 102.2, 119.5,
119.6, 126.9, 127.1, 127.8, 127.9, 132.5, 132.6, 133.2, 133.4, 133.5,
133.6, 133.7, 140.4, 140.5, 142.4, 142.8, 143.0, 143.1 ppm. UV/Vis
(CH2Cl2): λmax (lg ε) = 417 (5.2), 533 (4.5) nm.
1
of a red low-melting solid. Rf = 0.95 (CH2Cl2/C6H14, 1:1, v/v). H
NMR (400 MHz, CDCl3, 25 °C): δ = 0.59 (s, 9 H, SiCH3), 0.92 (t,
3
3JH,H = 7.2 Hz, 6 H, C5H10CH3), 0.94 (t, JH,H = 7.2 Hz, 3 H,
C5H10CH3), 1.34 (m, 6 H, C4H8CH2CH3 ), 1.43 (m, 6 H,
C3H6CH2CH2CH3), 1.60 (m, 6 H, C2H4CH2C2H4CH3), 2.26 (m, 6
H, CH2CH2C3H6CH3), 4.42 (m, 6 H, CH2C4H8CH3), 9.18 (d,
3JH,H = 5.0 Hz, 2 H, β-H), 9.20 (d, 3JH,H = 2.1 Hz, 2 H, β-H), 9.22
[5-Ethynyl-10,15,20-tris(4-methylphenyl)porphyrinato]nickel(II)
(14): A 100-mL round-bottom flask was charged with {10,15,20-
tris(4-methylphenyl)-5-[(trimethylsilyl)ethynyl]porphyrinato}-
nickel(II) 13 (108 mg, 0.146 mmol, 1 equiv.) and tetrabutylammo-
nium fluoride (61 mg, 0.234 mmol, 1.6 equiv.) in CH2Cl2 (50 mL).
The reaction mixture was stirred at room temp. until completion
(ca. 30 min, TLC control). The crude product was filtered through
a short layer of silica and washed with CH2Cl2. After the solvent
was removed under reduced pressure, the product was obtained in
a quantitative yield (97 mg, 0.146 mmol, 100%) as dark red crys-
3
3
(d, JH,H = 2.0 Hz, 2 H, β-H), 9.42 (d, JH,H = 5.0 Hz, 2 H, β-H)
ppm. 13C NMR (100.6 MHz, CDCl3, 25 °C): δ = 0.4, 14.2, 22.7,
29.8, 30.1, 30.2, 31.8, 34.0, 34.2, 37.4, 37.5, 96.4, 101.2, 105.5,
118.4, 119.6, 129.3, 129.8, 130.2, 131.7, 140.9, 141.4, 142.2,
143.9 ppm. UV/Vis (CH2Cl2): λmax (lg ε) = 428 (5.3), 548 (4.4), 585
(4.3) nm. HRMS (ES+): calcd. for C43H56N4NiSi [M + H]+
715.3706, found 715.3718.
1
tals. M.p. Ͼ 300 °C. Rf = 0.63 (CH2Cl2/C6H14, 1:2, v/v). H NMR
(5-Ethynyl-10,15,20-trihexylporphyrinato)nickel(II) (18): A 50-mL
round-bottomed flask was charged with {10,15,20-trihexyl-5-[(tri-
methylsilyl)ethynyl]porphyrinato}nickel(II) (17, 46 mg,
0.064 mmol, 1 equiv.) and tetrabutylammonium fluoride (25 mg,
0.1 mmol, 1.6 equiv.) in CH2Cl2 (20 mL). The reaction mixture was
stirred at room temp. until completion (ca. 30 min, TLC control).
The crude product was filtered through a short layer of silica gel
(400 MHz, CDCl3, 25 °C): δ = 2.66 (s, 3 H, C6H4CH3), 2.68 (s, 6
3
H, C6H4CH3), 4.08 (s, 1 H, CϵCH), 7.49 (d, JH,H = 8.8 Hz, 2 H,
3
3
HAr), 7.52 (d, JH,H = 8.2 Hz, 4 H, HAr), 7.88 (d, JH,H = 6.5 Hz,
3
3
2 H, HAr), 7.90 (d, JH,H = 7.6 Hz, 4 H, HAr), 8.71 (d, JH,H
=
3
4.7 Hz, 2 H, β-H), 8.73 (d, JH,H = 5.3 Hz, 2 H, β-H), 8.85 (d,
3JH,H = 4.7 Hz, 2 H, β-H), 9.54 (d, 3JH,H = 4.7 Hz, 2 H, β-H) ppm.
13C NMR (100.6 MHz, CDCl3, 25 °C): δ = 21.5, 29.8, 84.1, 84.2, and washed with CH2Cl2. After the solvent was removed under
4886
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© 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2008, 4881–4890

Intermolecular Pauson–Khand Reaction of meso-Substituted Porphyrins
reduced pressure, the product was obtained in 41 mg (0.06 mmol,
99%) yield of a red low-melting solid. Rf = 0.89 (CH2Cl2/C6H14,
143.0 ppm. UV/Vis (CH2Cl2): λmax (lg ε) = 409 (5.4), 523 (4.6), 550
(4.4) nm. HRMS (ES+): calcd. for C42H28N4Ni [M + H]+ 647.1746,
found 647.1755.
1
3
1:1, v/v). H NMR (400 MHz, CDCl3, 25 °C): δ = 0.94 (t, JH,H
=
3
7.2 Hz, 6 H, C5H10CH3), 0.96 (t, JH,H = 7.2 Hz, 3 H, C5H10CH3),
1.37 (m, 6 H, C4H8CH2CH3 ), 1.43 (m, 6 H, C3H6CH2CH2CH3),
1 . 5 9 ( m , 6 H , C 2 H 4 C H 2 C 2 H 4 C H 3 ) , 2 . 2 5 ( m , 6 H ,
[5-(4-Ethynylphenyl)-10,20-bis(4-methylphenyl)porphyrinato]zinc(II)
(21): A 100-mL round-bottomed flask was charged with 5-(4-ethyn-
ylphenyl)-10,20-bis(4-methylphenyl)porphyrin (19, 76 mg,
0.03 mmol, 1 equiv.) in CH2Cl2 (50 mL). Zn(OAc)2 (10 mg,
0.045 mmol, 1.5 equiv.) dissolved in MeOH (5 mL) was added, and
the reaction mixture was stirred at room temp. until completion
(ca. 1 h, TLC control). The crude product was filtered through a
layer of silica gel. After the solvent was removed under reduced
pressure, the product was obtained quantitatively (84 mg,
0.03 mmol, 99 %) as pink crystals. M.p. Ͼ 300 °C. Rf = 0.46
3
CH2CH2C3H6CH3), 4.04 (s, 1 H, CϵCH), 4.32 (t, JH,H = 8.1 Hz,
3
2 H, CH2C4H8CH3), 4.37 (t, JH,H = 8.0 Hz, 4 H, CH2C4H8CH3),
9.12 (d, 3JH,H = 5.0 Hz, 2 H, β-pyrrole-H), 9.14 (d, 3JH,H = 5.0 Hz,
3
3
2 H, β-H), 9.19 (d, JH,H = 4.8 Hz, 2 H, β-H), 9.42 (d, JH,H
=
4.8 Hz, 2 H, β-H) ppm. 13C NMR (100.6 MHz, CDCl3, 25 °C): δ
= 14.2, 22.7, 29.8, 30.0, 30.1, 31.8, 33.9, 34.2, 37.4, 37.6, 83.6, 84.2,
94.9, 118.4, 119.7, 129.3, 129.8, 130.3, 131.4, 140.8, 141.4, 142.2,
143.9 ppm. UV/Vis (CH2Cl2): λmax (lg ε) = 425 (5.6), 545 (4.6), 581
(4.5) nm. HRMS (ES+): calcd. for C40H48N4Ni [M + H]+ 643.3311,
found 643.3282.
1
(CH2Cl2/C6H14, 1:1, v/v). H NMR (400 MHz, CDCl3, 25 °C): δ =
3
2.76 (s, 6 H, C6H4CH3), 3.34 (s, 1 H, CϵCH), 7.61 (d, JH,H
=
7.6 Hz, 4 H, HAr), 7.92 (d, 3JH,H = 7.6 Hz, 2 H, HAr), 8.14 (d, 3JH,H
3
= 8.2 Hz, 4 H, HAr), 8.21 (d, JH,H = 8.2 Hz, 2 H, HAr), 8.97 (d,
5-(4-Ethynylphenyl)-10,20-bis(4-methylphenyl)porphyrin (19): A
250-mL 3-necked round-bottom flask was filled with Ar and
charged with p-bromobenzene (1.113 g, 6.15 mmol, 15 equiv.) in
dry diethyl ether (3 mL). n-Butyllithium (4.9 mL, 12.3 mmol,
30 equiv.) was added dropwise at –78 °C over 1 h. After the ad-
dition was complete, the reaction mixture was warmed to –45 °C
(by addition of cooling solvent to the cooling bath), and dry THF
(2 mL) was added until a white solid was formed. 5,15-Bis(4-meth-
ylphenyl)porphyrin (1, 200 mg, 0.41 mmol, 1 equiv.) dissolved in
dry THF (150 mL) was added quickly, and the reaction mixture
was stirred at room temp. overnight (colour change to brown).
Then water (2 mL, colour change to emerald green) and DDQ
(1.4 g, 6.15 mmol, 15 equiv.) were added (colour change to red).
After 1 h, the crude product was filtered through a layer of silica
gel and recrystallised from CH2Cl2/MeOH. The product was ob-
tained in 95 mg (0.16 mmol, 39%) yield as purple crystals. M.p.
Ͼ 300 °C. Rf = 0.24 (CH2Cl2/C6H14, 1:4, v/v). 1H NMR (400 MHz,
CDCl3, 25 °C): δ = –2.99 (br. s, 2 H, NH), 2.75 (s, 6 H, C6H4CH3),
3JH,H = 4.7 Hz, 2 H, β-H), 9.06 (d, 3JH,H = 4.7 Hz, 2 H, β-H), 9.13
3
3
(d, JH,H = 4.7 Hz, 2 H, β-H), 9.38 (d, JH,H = 4.1 Hz, 2 H, β-H),
10.23 (s, 1 H, meso-H) ppm. 13C NMR (100.6 MHz, CDCl3,
25 °C): δ = 21.6, 83.8, 105.9, 120.2, 120.8, 121.3, 127.4, 130.3,
131.5, 131.7, 132.1, 132.7, 134.4, 134.5, 137.2, 139.6, 143.7, 149.3,
149.7, 150.3 ppm. UV/Vis (CH2Cl2): λmax (lg ε) = 415 (5.7), 542
(4.8) nm. HRMS (ES+): calcd. for C42H30N4 [M]+ 652.1605, found
652.1588.
Pauson–Khand Reaction of Allylporphyrins
General Procedure: Phenylacetylene (10 equiv.) was placed into a
round-bottom flask under Ar in dry THF (20 mL). Co2(CO)8
(10 equiv.) was added, and the reaction mixture was stirred at room
temp. until formation of the complex (ca. 1 h, monitored by TLC).
Then the allylporphyrin (6, 7, 11) (40–45.5 mg; 1 equiv.) was added,
and the reaction mixture was heated at reflux for 12 h. The crude
products were purified by dry-loaded column chromatography on
silica gel (CH2Cl2/C6H14, 1:1, v/v). The first fraction of the column
was assumed to be the remaining (phenylacetylene)(porphyrin)Co
complex. Recrystallisation was carried out from CH2Cl2/MeOH.
3
3.35 (s, 1 H, CϵCH), 7.01 (d, JH,H = 7.6 Hz, 4 H, HAr), 7.91 (d,
3JH,H = 8.2 Hz, 2 H, HAr), 8.15 (d, 3JH,H = 7.6 Hz, 4 H, HAr), 8.21
3
3
(d, JH,H = 7.6 Hz, 2 H, HAr), 8.86 (d, JH,H = 4.7 Hz, 2 H, β-H),
3
3
8.97 (d, JH,H = 4.7 Hz, 2 H, β-H), 9.08 (d, JH,H = 4.1 Hz, 2 H,
β-H), 9.37 (d, JH,H = 4.7 Hz, 2 H, β-H), 10.25 (s, 1 H, meso-H)
[5-Formyl-10,15,20-tris(4-methylphenyl)porphyrinato]nickel(II) (5):
The product was obtained from the Pauson–Khand reaction of
[5,10,15-tris(4-methylphenyl)-20-vinylporphyrinato]nickel(II) (20,
55 mg, 0.08 mmol, 1 equiv.) and phenylacetylene in 6 mg (9 µmol,
11%) yield as bright green crystals. M.p. 81 °C. Rf = 0.66 (CH2Cl2/
3
ppm. 13C NMR (100.6 MHz, CDCl3): δ = 21.1, 77.8, 83.3, 104.5,
118.8, 119.4, 121.1, 127.2, 129.9, 130.5, 133.9, 134.2, 137.0, 138.3,
142.9, 145.3 (br.), 146.7 (br.) ppm. UV/Vis (CH2Cl2): λmax (lg ε) =
414 (5.7), 509 (4.6), 543 (4.4), 582 (4.4), 639 (4.4) nm. HRMS
(ES+): calcd. for C42H30N4 [M + H]+ 591.2549, found 591.2524.
1
C6H14, 1:2, v/v). H NMR (400 MHz, CDCl3, 25 °C): δ = 2.65 (s,
3
3 H, C6H4CH3), 2.67 (s, 6 H, C6H4CH3), 7.50 (t, JH,H = 8.0 Hz,
3
3
6 H, HAr), 7.85 (d, JH,H = 8.0 Hz, 6 H, HAr), 8.60 (d, JH,H
=
[5-(4-Ethynylphenyl)-10,20-bis(4-methylphenyl)porphyrinato]nickel-
(II) (20): A 100-mL 2-necked round-bottom flask was charged with
5-(4-ethynylphenyl)-10,20-bis(4-methylphenyl)porphyrin (19,
176 mg, 0.3 mmol, 1 equiv.) and Ni(acac)2 (116 mg, 0.45 mmol,
1.5 equiv.) in toluene (50 mL). The reaction mixture was heated to
reflux until completion (ca. 4 h, TLC control). The solvent was
removed under reduced pressure, and the residue was dissolved in
CH2Cl2 and filtered through a layer of silica gel. After recrystalli-
sation from CH2Cl2/MeOH, the product was obtained as red need-
3
4.7 Hz, 2 H, β-H), 8.68 (d, JH,H = 4.7 Hz, 2 H, β-H), 8.88 (d,
3JH,H = 5.2 Hz, 2 H, β-H), 9.80 (d, 3JH,H = 5.2 Hz, 2 H, β-H), 12.0
(s, 1 H, CHO) ppm. 13C NMR (100.6 MHz, CDCl3, 25 °C): δ =
21.0, 120.6, 127.3, 130.1, 131.4, 132.9, 135.0, 136.5, 137.3, 140.5,
141.5, 143.9, 192.3 ppm. UV/Vis (CH2Cl2): λmax (lg ε) = 426 (4.8),
552 (3.8), 593 (3.9) nm.
{5,10,15-Tris(4-methylphenyl)-20-[(2-oxo-3-phenylcyclopent-3-en-1-
yl)methyl]porphyrinato}nickel(II) (22): By using [5-allyl-10,15,20-
tris(4-methylphenyl)porphyrinato]nickel(II) (6, 40 mg, 0.059 mmol,
les in 166 mg (0.257 mmol, 86%) yield. M.p. Ͼ 300 °C. Rf = 0.77
1
(CH2Cl2/C6H14, 1:1, v/v). H NMR (400 MHz, CDCl3, 25 °C): δ = 1 equiv.) as starting material, the reaction was carried out in a
3
2.69 (s, 6 H, C6H4CH3), 3.30 (s, 1 H, CϵCH), 7.53 (d, JH,H
=
Schlenk-tube, and the solution was degassed by three freeze-pump-
7.6 Hz, 4 H, HAr), 7.84 (d, 3JH,H = 8.2 Hz, 2 H, HAr), 7.94 (d, 3JH,H thaw cycles and refilled with Ar. The product was obtained as the
3
= 7.6 Hz, 4 H, HAr), 8.01 (d, JH,H = 7.6 Hz, 2 H, HAr), 8.76 (d,
second fraction by column chromatography followed by recrystalli-
3JH,H = 4.7 Hz, 2 H, β-H), 8.84 (d, 3JH,H = 5.3 Hz, 2 H, β-H), 8.95 sation as red crystals in 18.8 mg (0.023 mmol, 39%) yield. M.p.
3
3
1
(d, JH,H = 4.7 Hz, 2 H, β-H), 9.16 (d, JH,H = 4.7 Hz, 2 H, β-H),
146 °C. Rf = 0.21 (CH2Cl2/C6H14, 1:1, v/v). H NMR (400 MHz,
9.86 (s, 1 H, meso-H) ppm. 13C NMR (100.6 MHz, CDCl3, 25 °C): CDCl3, 25 °C): δ = 1.97 (m, 1 H, C=CHCH2CHCH2), 2.25 (m,
δ = 21.5, 78.2, 83.6, 104.7, 118.2, 118.9, 121.6, 127.6, 130.6, 131.6,
132.2, 132.3, 132.7, 133.6, 133.7, 137.9, 141.8, 141.9, 142.8, 142.9,
1 H, C=CHCH2CHCH2), 2.66 (s, 3 H, C6H4CH3), 2.67 (s, 6 H,
3
C6H4CH3), 3.24 (m, 1 H, C=CHCH2CHCH2), 4.55 (dd, JH,H
=
Eur. J. Org. Chem. 2008, 4881–4890
© 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
4887

S. Horn, M. O. Senge
FULL PAPER
14.0, 2JH,H = 11.1 Hz, 1 H, C=CHCH2CHCH2), 5.69 (dd, JH,H
=
=
{5,10,15-Tris(4-methylphenyl)-20-[(4-oxo-3-phenylcyclopent-2-en-1-
yl)methyl]porphyrinato}zinc(II) (25): The product was obtained as
5.9 Hz, 1 H, HAr), 7.43 (m, 2 H, HAr), 7.49 (d, JH,H = 7.0 Hz, 4 the third fraction of the reaction above by column chromatography
3
2
3
14.6, JH,H = 4.1 Hz, 1 H, C=CHCH2CHCH2), 7.39 (d, JH,H
3
3
3
H, HAr), 7.49 (d, JH,H = 7.6 Hz, 2 H, HAr), 7.55 (dd, JH,H = 2.9,
followed by recrystallisation as purple crystals in 7.3 mg (9 µmol,
15%) yield. M.p. Ͼ 300 °C. Rf = 0.12 (CH2Cl2/C6H14, 1:1, v/v). 1H
NMR (400 MHz, CDCl3, 25 °C): δ = 2.74 (s, 3 H, C6H4CH3), 2.75
(s, 6 H, C6H4CH3), 2.88 (m, 2 H, COCH2CH), 4.14 (m, 1 H,
3JH,H = 1.8 Hz, 1 H, C=CHCH2CHCH2), 7.73 (d, JH,H = 6.4 Hz,
3
3
3
2 H, HAr), 7.88 (d, JH,H = 3.5 Hz, 4 H, HAr), 7.89 (d, JH,H
=
3
3.5 Hz, 2 H, HAr), 8.74 (d, JH,H = 4.1 Hz, 2 H, β-H), 8.74 (d,
3JH,H = 4.6 Hz, 2 H, β-H), 8.88 (d, 3JH,H = 4.7 Hz, 2 H, β-H), 9.44 COCH2CH), 5.07 (dd, JH,H = 14.7, JH,H = 9.8 Hz, 1 H,
3
2
3
2
(d, 3JH,H = 5.3 Hz, 2 H, β-H) ppm. 13C NMR (150.9 MHz, CDCl3, COCH2CHCH2), 5.35 (dd, JH,H = 14.7, JH,H = 6.9 Hz, 1 H,
25 °C): δ = 14.1, 21.5, 22.7, 29.4, 29.7, 31.9, 32.8, 35.0, 52.3, 114.5,
118.6, 127.0, 127.6, 128.4, 129.7, 131.6, 132.3, 133.1, 133.6, 137.4,
142.2, 142.4, 142.8, 157.3, 207.8 ppm. UV/Vis (CH2Cl2): λmax (lg ε)
COCH2CHCH2), 7.29 (s, 2 H, HAr), 7.50 (m, 3 H, HAr), 7.56 (s, 1
3
3
H, CH=CCO), 7.59 (d, JH,H = 3.9 Hz, 4 H, HAr), 7.60 (d, JH,H
3
= 1.9 Hz, 4 H, HAr), 8.10 (d, JH,H = 7.9 Hz, 4 H, HAr), 8.13 (d,
= 419 (5.4), 523 (4.7) nm. HRMS (ES+): calcd. for C53H40N4NiO 3JH,H = 2.9 Hz, 2 H, HAr), 8.96 (d, 3JH,H = 3.9 Hz, 2 H, β-H), 8.96
[M + H]+ 807.2634, found 807.2648.
(d, JH,H = 3.9 Hz, 2 H, β-H), 9.04 (d, JH,H = 3.9 Hz, 2 H, β-H),
3
3
9.44 (d, JH,H = 4.9 Hz, 2 H, β-H) ppm. 13C NMR (150.9 MHz,
3
{5,10,15-Tris(4-methylphenyl)-20-[(4-oxo-3-phenylcyclopent-2-en-1-
yl)methyl]porphyrinato}nickel(II) (23): The product was obtained as
the third fraction by column chromatography of the reaction above.
Recrystallisation gave 15.7 mg (0.019 mmol, 33%) yield of red crys-
tals. M.p. 182 °C. Rf = 0.16 (CH2Cl2/C6H14, 1:1, v/v). 1H NMR
(400 MHz, CDCl3, 25 °C): δ = 2.63 (m, 1 H, COCH2CH), 2.66 (s,
CDCl3, 25 °C): δ = 13.9, 21.4, 22.5, 29.2, 29.5, 31.8, 40.5, 43.3,
45.4, 53.2, 115.9, 120.9, 121.1, 127.1, 127.2, 128.2, 128.3, 128.4,
131.2, 131.9, 132.0, 132.6, 134.2, 134.3, 136.9, 137.0, 139.6, 139.7,
142.2, 149.8, 150.2, 150.5, 161.6, 206.5 ppm. UV/Vis (CH2Cl2):
λmax (lg ε) = 422 (5.6), 552 (4.5), 588 (4.4) nm. HRMS (ES+): calcd.
for C53H40N4OZn [M + H]+ 813.2572, found 813.2585.
3
3 H, C6H4CH3), 2.68 (s, 6 H, C6H4CH3), 2.77 (dd, JH,H = 18.7,
{5,10,15-Trihexyl-20-[(2-oxo-3-phenylcyclopent-3-en-1-yl)-
methyl]porphyrinato}nickel(II) (26): By using [5-allyl-10,15,20-tri-
hexylporphyrinato]nickel(II) (11, 45.5 mg, 0.069 mmol, 1 equiv.) as
starting material, the product was obtained as the second fraction
by column chromatography followed by recrystallisation as red
crystals in 7.4 mg (9 µmol, 14 %) yield. M.p. 102 °C. Rf = 0.15
2JH,H = 6.4 Hz, 1 H, COCH2CH), 3.70 (m, 1 H, COCH2CH), 4.80
2
(dd, 3JH,H = 14.0, JH,H = 9.4 Hz, 1 H, COCH2CHCH2), 5.10 (dd,
2
3JH,H = 14.0, JH,H = 7.0 Hz, 1 H, COCH2CHCH2), 7.28 (m, 5 H,
3
HAr), 7.49 (s, 1 H, CH=CCO), 7.50 (d, JH,H = 4.7 Hz, 4 H, HAr),
3
3
7.51 (d, JH,H = 7.6 Hz, 2 H, HAr), 7.89 (d, JH,H = 5.3 Hz, 4 H,
3
3
HAr), 7.91 (d, JH,H = 7.0 Hz, 2 H, HAr), 8.76 (d, JH,H = 4.7 Hz,
2 H, β-H), 8.76 (d, JH,H = 5.3 Hz, 2 H, β-H), 8.88 (d, JH,H
1
(CH2Cl2/C6H14, 1:1, v/v). H NMR (600 MHz, CDCl3, 25 °C): δ =
3
3
=
3
3
0.92 (t, JH,H = 7.2 Hz, 6 H, C5H10CH3), 0.92 (t, JH,H = 7.2 Hz,
3 H, C5H10CH3), 1.35 (m, 6 H, C4H8CH2CH3 ), 1.43 (m, 6 H,
C3H6CH2CH2CH3), 1.58 (m, 6 H, C2H4CH2C2H4CH3), 1.89 (m, 1
H, C=CHCH2CHCH2), 2.12 (m, 1 H, C=CHCH2CHCH2), 2.26
(m, 6 H, CH2CH2C3H6CH3), 3.12 (m, 1 H, C=CHCH2CHCH2),
5.3 Hz, 2 H, β-H), 9.28 (d, JH,H = 5.3 Hz, 2 H, β-H) ppm. 13C
NMR (150.9 MHz, CDCl3, 25 °C): δ = 13.9, 21.3, 22.5, 29.5, 30.8,
31.8, 43.1, 43.5, 113.3, 118.6, 118.7, 127.0, 127.5, 128.2, 128.3,
129.0, 131.0, 132.2, 132.22, 132.9, 133.4, 133.5, 137.3, 137.6,
137.63, 142.0, 142.2, 142.4, 142.5, 142.8, 160.9, 206.1 ppm. UV/Vis
(CH2Cl2): λmax (lg ε) = 419 (5.6), 531 (4.6) nm. HRMS (ES+):
calcd. for C53H40N4NiO [M + H]+ 807.2634, found 807.2663.
3
3
2
4.42 (dd, JH,H = 14.3, JH,H = 11.3 Hz, 1 H, C=CHCH2CHCH2),
3
2
4.51 (m, 6 H, CH2C4H8CH3), 5.61 (dd, JH,H = 14.7, JH,H
4.1 Hz, 1 H, C=CHCH2CHCH2), 7.37 (t, JH,H = 7.2 Hz, 1 H,
HAr), 7.42 (dd, JH,H = 7.5, JH,H = 7.2 Hz, 2 H, HAr), 7.52 (m, 1
H, C=CHCH2CHCH2), 7.73 (d, JH,H = 7.5 Hz, 2 H, HAr), 9.28
=
3
3
3
{5,10,15-Tris(4-methylphenyl)-20-[(2-oxo-3-phenylcyclopent-3-en-1-
yl)methyl]porphyrinato}zinc(II) (24): By using [5-allyl-10,15,20-
bis(4-methylphenyl)porphyrinato]zinc(II) (7, 40 mg, 0.059 mmol,
1 equiv.) as starting material, the product was obtained as the sec-
ond fraction by column chromatography followed by recrystalli-
sation as purple crystals in 3.8 mg (4 µmol, 8 %) yield. M.p.
Ͼ 300 °C. Rf = 0.19 (CH2Cl2/C6H14, 1:1, v/v). 1H NMR (600 MHz,
CDCl3, 25 °C): δ = 2.31 (m, 1 H, C=CHCH2CHCH2), 2.73 (s, 3
H, C6 H4 CH3 ), 2. 76 (s, 6 H, C6 H4 CH3 ), 2. 95 (m, 1 H,
C=CHCH2CHCH2), 3.83 (m, 1 H, C=CHCH2CHCH2), 4.94 (dd,
3
3
3
(d, JH,H = 5.3 Hz, 2 H, β-H), 9.28 (d, JH,H = 6.4 Hz, 2 H, β-H),
3
3
9.30 (d, JH,H = 5.3 Hz, 2 H, β-H), 9.37 (d, JH,H = 4.9 Hz, 2 H,
β-H) ppm. 13C NMR (150.9 MHz, CDCl3, 25 °C): δ = 13.9, 22.5,
29.9, 31.6, 32.6, 33.8, 34.6, 37.0, 37.1, 51.8, 112.6, 117.0, 117.2,
126.9, 128.3, 129.7, 129.8, 130.1, 131.5, 140.9, 141.0, 141.1, 142.1,
157.2, 207.7 ppm. UV/Vis (CH2Cl2): λmax (lg ε) = 421 (5.3), 540
(4.5), 574 (4.3) nm. HRMS (ES+): calcd. for C50H58N4NiO [M +
H]+ 789.4042, found 789.4028.
2
3JH,H = 14.7, JH,H = 11.0 Hz, 1 H, C=CHCH2CHCH2), 5.98 (dd,
{5,10,15-Trihexyl-20-[(4-oxo-3-phenylcyclopent-2-en-1-yl)methyl]-
2
3JH,H = 14.7, JH,H = 4.4 Hz, 1 H, C=CHCH2CHCH2), 7.41 (t, porphyrinato}nickel(II) (27): The product was obtained as the third
3
3
3JH,H = 7.3 Hz, 1 H, HAr), 7.48 (dd, JH,H = 7.3, JH,H = 7.3 Hz,
fraction of the reaction above by column chromatography followed
by recrystallisation as red crystals in 10.3 mg (0.013 mmol, 19%)
3
3
2 H, HAr), 7.58 (d, JH,H = 7.3 Hz, 2 H, HAr), 7.58 (d, JH,H
=
3
1
5.9 Hz, 2 H, HAr), 7.60 (d, JH,H = 5.1 Hz, 2 H, HAr), 7.75 (dd,
yield. M.p. 136 °C. Rf = 0.23 (CH2Cl2/C6H14, 1:1, v/v). H NMR
3JH,H = 2.8, JH,H = 2.4 Hz, 1 H, C=CHCH2CHCH2), 7.86 (d,
(600 MHz, CDCl3 , 25 °C): δ = 0.92 (t, 3J = 7.3 Hz, 6 H,
3
3JH,H = 7.4 Hz, 2 H, HAr), 8.10 (d, 3JH,H = 7.3 Hz, 2 H, HAr), 8.11
C5H10CH3), 0.92 (t, JH,H = 7.3 Hz, 3 H, C5H10CH3), 1.35 (m, 6
3
3
3
(d, JH,H = 5.9 Hz, 2 H, HAr), 8.13 (d, JH,H = 7.3 Hz, 2 H, HAr),
8.95 (d, JH,H = 5.2 Hz, 2 H, β-H), 8.95 (d, JH,H = 5.2 Hz, 2 H,
β-H), 8.88 (d, JH,H = 4.7 Hz, 2 H, β-H), 9.69 (d, JH,H = 4.4 Hz, (m, 1 H, COCH2CH), 2.74 (m, 1 H, COCH2CH), 3.59 (m, 1 H,
H, C4H8CH2CH3 ), 1.44 (m, 6 H, C3H6CH2CH2CH3), 1.59 (m, 6
H, C2H4CH2C2H4CH3), 2.28 (m, 6 H, CH2CH2C3H6CH3), 2.60
3
3
3
3
2 H, β-H) ppm. 13C NMR (150.9 MHz, CDCl3, 25 °C): δ = 13.9,
21.4, 22.5, 29.2, 29.5, 30.7, 33.0, 36.3, 54.6, 117.3, 120.7, 127.0,
127.1, 128.4, 128.8, 131.6, 131.8, 131.9, 132.6, 134.2, 136.9, 139.7,
142.2, 149.8, 149.9, 150.1, 150.4, 157.1, 207.9 ppm. UV/Vis
(CH2Cl2): λmax (lg ε) = 422 (5.9), 551 (4.8), 589 (4.6) nm. HRMS
(ES+): calcd. for C53H40N4OZn [M + H]+ 813.2572, found
813.2590.
COCH2CH), 4.51 (m, 6 H, CH2C4H8CH3), 4.71 (dd, 3JH,H = 13.9,
2JH,H = 9.4 Hz, 1 H, COCH2CHCH2), 4.99 (dd, 3JH,H = 14.3, 2JH,H
= 7.2 Hz, 1 H, COCH2CHCH2), 7.26 (s, 1 H, CH=CCO), 7.26 (d,
3JH,H = 1.9 Hz, 2 H, HAr), 7.27 (d, 3JH,H = 1.5 Hz, 1 H, HAr), 7.51
3
3
(m, 2 H, HAr), 9.23 (d, JH,H = 5.3 Hz, 2 H, β-H), 9.29 (d, JH,H
3
= 4.9 Hz, 2 H, β-H), 9.30 (d, JH,H = 5.7 Hz, 4 H, β-H) ppm. 13C
NMR (150.9 MHz, CDCl3, 25 °C): δ = 13.9, 22.5, 29.5, 29.9, 31.6,
4888
www.eurjoc.org
© 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2008, 4881–4890

Intermolecular Pauson–Khand Reaction of meso-Substituted Porphyrins
33.9, 37.2, 38.8, 43.1, 43.2, 111.6, 117.2, 117.4, 127.0, 128.1, 128.2,
129.3, 129.8, 129.9, 131.1, 131.1, 140.9, 141.2, 141.3, 142.3, 161.1,
206.2 ppm. UV/Vis (CH2Cl2): λmax (lg ε) = 421 (5.5), 538 (4.8), 570
(4.6) nm. HRMS (ES+): calcd. for C50H58N4NiO [M + H]+
789.4042, found 789.4020.
128.1, 130.5, 131.5, 131.7, 131.8, 132.4, 132.5, 134.3, 134.4, 135.6,
136.9, 139.6, 139.7, 142.9, 134.1, 145.3, 145.9, 148.7, 149.5, 149.8,
150.2, 150.3, 1501.4, 160.6, 186.0, 209.2 ppm. UV/Vis (CH2Cl2):
λmax (lg ε) = 415 (6.2), 543 (5.1), 582 (4.9) nm. HRMS (ES+): calcd.
for C50H38N4OZn [M]+ 774.2337, found 774.2338.
{5,15-Bis(4-methylphenyl)-10-[4-(3-oxotricyclo[5.2.1.02,6]dec-4,8-
dien-4-yl)phenyl]porphyrinato}nickel(II) (30): By using [5-(4-ethyn-
ylphenyl)-10,20-bis(4-methylphenyl)porphyrinato]nickel(II) (20,
50 mg, 0.077 mmol) and norbornadiene as starting materials, after
recrystallisation the product was obtained as red crystals in 22.2 mg
Pauson–Khand Reaction of (4-Ethynylphenyl)porphyrins
General Procedure: The (4-ethynylphenyl)porphyrin (20, 21) (26–
50 mg; 1 equiv.) was placed into a Schlenk tube under Ar in dry
THF (20 mL). The solution was degassed by three freeze-pump-
thaw cycles and refilled with Ar. Next Co2(CO)8 (10 equiv.) was
added, and the reaction mixture was stirred at room temp. until
formation of the complex (ca. 1 h, monitored by TLC). Then nor-
bornene or norbornadiene (2 equiv.) was added, and the reaction
mixture was heated at 80 °C for 12 h. The crude products were
purified by dry-loaded column chromatography on silica gel
(CH2Cl2/C6H14, 1:1, v/v). The first fraction of the column was as-
sumed to be the remaining (norbornene/norbornadiene)(porphy-
rin)Co complex, and the product was obtained as the second frac-
tion. Recrystallisation was carried out from CH2Cl2/MeOH.
(0.028 mmol, 38%) yield. M.p. Ͼ 300 °C. Rf = 0.21 (CH2Cl2/C6H14,
3
1:1, v/v). 1H NMR (400 MHz, CDCl3, 25 °C): δ = 1.56 (d, JH,H
=
3
1.2 Hz, 2 H, CHCH2 CH), 2.64 (d, JH , H = 5.3 Hz, 2 H,
COCHCH), 2.69 (s, 6 H, C6H4CH3), 2.94 (s, 1 H, C=CHCHCH),
3.01 (m, 1 H, C=CHCHCH), 3.17 (d, JH,H = 1.2 Hz, 1 H,
3
3
3
COCHCH), 6.35 (dd, JH,H = 5.3, JH,H = 2.9 Hz, 1 H, CH=CH),
6.43 (dd, 3JH,H = 5.3, 3JH,H = 2.9 Hz, 1 H, CH=CH), 7.53 (d, 3JH,H
3
= 7.6 Hz, 4 H, HAr), 7.94 (d, JH,H = 8.2 Hz, 4 H, HAr), 7.99 (d,
3JH,H = 2.9 Hz, 1 H, C=CH), 8.06 (d, JH,H = 8.8 Hz, 2 H, HAr),
3
3
3
8.06 (d, JH,H = 8.8 Hz, 2 H, HAr), 8.80 (d, JH,H = 4.7 Hz, 2 H,
β-H), 8.83 (d, JH,H = 4.7 Hz, 2 H, β-H), 8.94 (d, JH,H = 5.3 Hz,
2 H, β-H), 9.16 (d, JH,H = 4.7 Hz, 2 H, β-H), 9.86 (s, 1 H, meso-
{5,15-Bis(4-methylphenyl)-10-[4-(3-oxotricyclo[5.2.1.02,6]dec-4-en-4-
yl)phenyl]porphyrinato}nickel(II) (28): By using [5-(4-ethyn-
ylphenyl)-10,20-bis(4-methylphenyl)porphyrinato]nickel(II) (20,
40 mg, 0.062 mmol, 1 equiv.) and norbornene (2 equiv.) as starting
materials, the product was obtained after recrystallisation as purple
crystals in 40.4 mg (0.053 mmol, 85%) yield. M.p. Ͼ 300 °C. Rf =
0.24 (CH2Cl2/C6H14, 1:1, v/v). 1H NMR (400 MHz, CDCl3, 25 °C):
3
3
3
H) ppm. 13C NMR (150.9 MHz, CDCl3, 25 °C): δ = 21.3, 41.4,
43.4, 44.2, 49.3, 53.6, 104.4, 118.6, 125.3, 127.5, 130.9, 131.7, 131.8,
131.9, 132.5, 133.5, 133.7, 137.1, 137.3, 137.9, 138.5, 141.3, 142.1,
142.6, 142.7, 142.8, 146.9, 160.2, 207.8 ppm. UV/Vis (CH2Cl2):
λmax (lg ε) = 409 (5.7), 523 (4.7), 548 (4.5) nm. HRMS (MALDI
LD+): calcd. for C50H36N4NiO [M]+ 766.2243, found 766.2251.
3
3
δ = 1.14 (d, JH,H = 10.5 Hz, 1 H, CHCH2CH), 1.31 (dd, JH,H
=
11.7, 3JH,H = 10.5 Hz, 1 H, CHCH2CH), 1.46 [m, 2 H, C=CH(CH)2-
CH2], 1.77 [m, 2 H, CO(CH)2CH2], 2.42 (s, 1 H, COCHCHCH2),
10,10Ј-[(3,11-Dioxotetracyclo[5.2.1.02,6.08,12]trideca-4,9-dien-4,10-
diyl)bis(4,1-phenylene)]bis{[5,15-bis(4-methylphenyl)porphyrinato]-
nickel(II)} (31): By using [5-(4-ethynylphenyl)-10,20-bis(4-meth-
ylphenyl)porphyrinato]nickel(II) (20, 26 mg, 0.039 mmol) and
{5,15-Bis(4-methylphenyl)-10-[4-(3-oxotricyclo[5.2.1.02,6]dec-4,8-
dien-4-yl)phenyl]porphyrinato}nickel(II) (30, 30 mg, 0.039 mmol)
as starting materials, the product was obtained as the second frac-
tion of the column chromatography after recrystallisation in 28 mg
(0.019 mmol, 50%) yield as red crystals. M.p. Ͼ 300 °C. Rf = 0.69
(CH2Cl2). 1H NMR (400 MHz, CDCl3, 25 °C): δ = 1.31 (s, 2 H,
CHC H2 C H ) , 2 . 6 9 ( s, 1 2 H , C6 H4 CH3 ), 2. 84 (m, 4 H,
C = C H C H C H C H C H = C , C H 2 C H ) , 3 . 1 6 ( m , 2 H ,
3
2.54 (d, JH,H = 5.3 Hz, 1 H, COCHCHCH2), 2.64 (s, 1 H,
3
C=CHCHCHCH2), 2.69 (s, 6 H, C6H4CH3), 2.87 (d, JH,H
=
3
2.9 Hz, 1 H, C=CHCHCHCH2), 7.53 (d, JH,H = 7.0 Hz, 4 H,
HAr), 7.94 (d, 3JH,H = 5.9 Hz, 4 H, HAr), 7.96 (s, 1 H, C=CH), 8.06
3
3
(s, 4 H, HAr), 8.81 (d, JH,H = 5.9 Hz, 2 H, β-H), 8.83 (d, JH,H
=
3
4.7 Hz, 2 H, β-H), 8.95 (d, JH,H = 4.7 Hz, 2 H, β-H), 9.16 (d,
3JH,H = 4.7 Hz, 2 H, β-H), 9.86 (s, 1 H, meso-H) ppm. 13C NMR
(100.6 MHz, CDCl3, 25 °C): δ = 21.1, 28.0, 28.8, 31.0, 28.1, 39.2,
45.5, 54.7, 104.1, 118.3, 118.4, 125.0, 127.2, 130.5, 131.5, 131.6,
131.7, 137.2, 133.2, 136.9, 137.5, 140.9, 141.8, 142.3, 142.5, 145.5,
160.4, 208.9 ppm. UV/Vis (CH2Cl2): λmax (lg ε) = 409 (5.8), 522
(4.9), 550 (4.7) nm. HRMS (ES+): calcd. for C50H38N4NiO [M +
H]+ 769.2477, found 769.2479.
3
COCHCHCHCO), 7.54 (d, JH,H = 7.6 Hz, 8 H, HAr), 7.95 (d,
3
3JH,H = 8.2 Hz, 8 H, HAr), 8.02 (d, JH,H = 2.34 Hz, 2 H, C=CH),
8.09 (s, 8 H, HAr), 8.81 (d, 3JH,H = 5.3 Hz, 4 H, β-H), 8.84 (d, 3JH,H
{5,15-Bis(4-methylphenyl)-10-[4-(3-oxotricyclo[5.2.1.02,6]dec-4-en-4-
yl)phenyl]porphyrinato}zinc(II) (29): By using [5-(4-ethynylphenyl)-
10,20-bis(4-methylphenyl)porphyrinato]zinc(II) (21, 40 mg,
0.061 mmol) and norbornene as starting materials, after recrystalli-
sation the product was obtained as pink crystals in 36.7 mg
3
= 4.7 Hz, 4 H, β-H), 8.95 (d, JH,H = 4.7 Hz, 4 H, β-H), 9.17 (d,
3JH,H = 4.7 Hz, 4 H, β-H), 9.86 (s, 2 H, meso-H) ppm. 13C NMR
(100.6 MHz, CDCl3, 25 °C): δ = 21.5, 29.7, 41.3, 47.2, 55.1, 104.6,
118.6, 118.8, 125.6, 127.6, 130.4, 131.9, 132.1, 132.2, 132.7, 133.7,
133.9, 137.5, 141.8, 142.2, 142.8, 142.9, 143.0, 146.6, 159.2,
207.8 ppm. UV/Vis (CH2Cl2): λmax (lg ε) = 410 (5.6), 521 (4.9), 551
(4.7) nm. HRMS (MALDI LD+): calcd. for C93H64N8O2Ni2 [M]+
1440.3859, found 1440.3795.
(0.047 mmol, 78%) yield. M.p. Ͼ 300 °C. Rf = 0.31 (CH2Cl2/C6H14,
1:1, v/v). 1H NMR (400 MHz, CDCl3, 25 °C): δ = 0.99 (d, JH,H
=
3
3
6.4 Hz, 1 H, CHCH2CH), 1.14 (d, JH,H = 11.1 Hz, 1 H,
CHCH2CH), 1.46 [m, 2 H, C=CH(CH)2CH2], 1.78 [m, 2 H,
CO(CH)2CH2], 2.44 (d, 3JH,H = 2.3 Hz, 1 H, COCHCHCH2), 2.48 10,10Ј-[(3,9-Dioxotetracyclo[5.2.1.02,6.08,12]trideca-4,10-dien-4,10-
3
(d, JH , H = 5. 3 Hz, 1 H, COCHCHCH2 ), 2.58 (s, 1 H, diyl)bis(4,1-phenylene)]bis{[5,15-bis(4-methylphenyl)porphyrinato]-
C=CHCHCHCH2), 2.76 (s, 6 H, C6H4CH3), 2.88 (s, 1 H, nickel(II)} (32): The product was obtained as the third fraction of
3
C=CHCHCHCH2), 7.61 (d, JH,H = 7.6 Hz, 4 H, HAr), 7.98 (d, the reaction above after recrystallisation in 26.5 mg (0.018 mmol,
3
1
3JH,H = 2.9 Hz, 1 H, C=CH), 8.07 (d, JH,H = 8.2 Hz, 2 H, HAr), 47%) yield as red crystals. M.p. Ͼ 300 °C. Rf = 0.19 (CH2Cl2). H
3
3
8.15 (d, JH,H = 7.6 Hz, 4 H, HAr), 8.25 (d, JH,H = 7.6 Hz, 2 H,
HAr), 9.01 (d, JH,H = 4.7 Hz, 2 H, β-H), 9.04 (d, JH,H = 4.7 Hz,
NMR (400 MHz, CDCl3, 25 °C): δ = 1.22 (s, 2 H, CHCH2CH),
2.69 (s, 12 H, C6 H4 CH3 ), 2.72 (d, JH , H = 5.3 Hz, 2 H,
CHCH2CH), 3.06 (m, 4 H, COCHCH), 7.53 (d, JH,H = 7.6 Hz, 8
3
3
3
3
3
3
2 H, β-H), 9.15 (d, JH,H = 4.7 Hz, 2 H, β-H), 9.43 (d, JH,H
=
4.7 Hz, 2 H, β-H), 10.29 (s, 1 H, meso-H) ppm. 13C NMR
(150.9 MHz, CDCl3, 25 °C): δ = 21.0, 21.4, 22.5, 23.7, 26.9, 28.4,
34.7, 38.4, 39.5, 47.9, 54.9, 105.7, 120.6, 120.7, 124.9, 125.4, 127.2,
H, HAr), 7.89 (d, JH,H = 1.8 Hz, 2 H, C=CH), 7.95 (d, JH,H =
3
3
8.2 Hz, 8 H, HAr), 8.06 (d, 3JH,H = 8.8 Hz, 4 H, HAr), 8.09 (d, 3JH,H
3
= 8.2 Hz, 4 H, HAr), 8.81 (d, JH,H = 5.3 Hz, 4 H, β-H), 8.85 (d,
Eur. J. Org. Chem. 2008, 4881–4890
© 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
4889

S. Horn, M. O. Senge
FULL PAPER
3JH,H = 5.3 Hz, 4 H, β-H), 8.95 (d, 3JH,H = 4.7 Hz, 4 H, β-H), 9.17
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(d, JH,H = 4.7 Hz, 4 H, β-H), 9.86 (s, 2 H, meso-H) ppm. 13C
NMR (100.6 MHz, CDCl3, 25 °C): δ = 21.1, 29.3, 40.5, 41.2, 47.7,
53.5, 104.2, 118.2, 118.3, 125.1, 127.2, 129.9, 131.4, 131.6, 131.8,
132.2, 133.3, 133.5, 137.0, 137.5, 141.3, 141.7, 142.3, 142.4, 142.5,
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[17]
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[19]
Acknowledgments
This work was generously supported by a Science Foundation Ire-
land Research Professorship grant (SFI/04/RP1/B482). We are
grateful to the Centre for Synthesis and Chemical Biology (CSCB)
for HRMS measurements.
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Received: May 20, 2008
Published Online: July 30, 2008
4890
www.eurjoc.org
© 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2008, 4881–4890