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Isocorroles Novel Tetrapyrrolic Macrocycles.

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CAS Registry Numbers.
4 % 130274-67-8; 6, 130248-84-9; 7. 130274-65-6; 9. 130274-66-7: 2.5-di-
formylpyrrole, 39604-60-9; 2-(2-cyano-2-ethoxycarbonylvinyl)-3,4-diethyl-5iodopyrrole), 130274-68-9.
[I] H. Scheer, J. J. Katz in K. M. Smith (Ed.): Porphyrins and Metulhporphyrins, Elsevier, Amsterdam 1975, p. 405; T.R. Janson, J. J. Katz in D.
Dolphin (Ed.): The Porphyrins, Vol. IV, Academic Press, New York 1979,
p. 1 ; J. Michl, J Am. Chem. Sor. 100 (1978) 6801 ;I. Gutman. Crour. Chem.
Actu58 (1985) 359; M. J. S. Dewar, E. F. Healy, J. Ruiz, Pure Appl. Chem.
58 (1986) 67; W. Flitsch, ibid. 58 (1986) 153.
121 a) Porphycene: E. Vogel, M. Kocher, H . Schmickler, J. Lex, Angew. Chrm.
98 (1986) 262; Angew. Chem. Int. Ed. Engl. 25 (1986) 257; E. Vogel, Pure
Appl. Chem. 62(1990) 557; h) Tetraoxaporphycene dication- E. Vogel, M.
Sicken, P. Rohrig, H. Schmickler, J Lex, 0. Ermer, Angew. Chern. 100
(1988) 450; Angew. Chem. l n t . Ed. Engl. 27 (1988) 411; c) Tetraoxaporphyrin dication: E. Vogel, W. Haas, B. Knipp, J. Lex, H. Schmickler, rhid.
100 (1988) 445 and 27 (1988) 406; W. Haas, B. Knipp, M. Sicken, J. Lex,
E. Vogel, ibid. 100 (1988) 448 and 27 (1988) 409; d)Tetrathiaporphyrin
dication: E. Vogel, P. Rohrig, M. Sicken, B. Knipp, A. Herrmann, M.
Pohl, H. Schmickler, J. Lex, ibrd. 101 (1989) 1683 and 28 (1989) 1651;
e) N,N',N",N"'-Tetramethylporphyrin dication B. Franck, rhid. 94 (1982)
327 and 21 (1982) 343; see also [2d].
[3] N,N',N",N'"Tetramethyl[26]porphyrin(3.3.3.3) dication M. GOSmdnn, B.
Franck, Angew. Chem. 98 (1986) 1107; Angew. Chem. Int. Ed. Engl. 25
(1986) 1100; N,N',N,N"'-Tetramethyl[34]porphyrin(5.5.5.5) dication: G
Kniibel, B. Franck, ibrd. 100 (1988) 1203 and 27 (1988) 1170.
[4] Representatives of porphyrrnoids that have a (4n + 2)n-electron main conjugation pathway and are not covered by formulas 1 and 2 are the sapphyrins [M. J. Broadhurst, R. Grigg. A. W. Johnson, J. Chem. SOC.Perkin
Trans. 1 1972, 2111; V.J. Bauer, D . L. J Clive, D . Dolphin, J. B. Paine 111.
F L. Harris, M. M. King, J. Loder, S.-W. Chien Wang. R. B. Woodward,
J. Am. Chem. Suc. 105 (1983)6429; J. L. Sessler, M. J. Cyr, V Lynch, J. Am.
Chem. Soc. 112 (1990) 28101, pentaphyrins [H.Rexhausen, A. Gossauer,
J. Chem. Suc. Chem. Cummun. 1983, 2751, corroles [A. W Johnson in
K. M. Smith (Ed.). Purphyrins and Metullopurphwins, Elsevier, Amsterdam 1975. p- 732, A. W. Johnson, I. T. Kay, J. Chem So<. 1965, 1620;
A. R. Battershy, G. L. Hodgson, M. Ihara, E. McDonald, J. Saunders, J
Chem. Sue. Perkin Trans. 1 1973, 29231, and texaphyrins [J. L. Sessler,
M. R. Johnson, V. Lynch, J. Org. Chem 52 (1987) 4394; J. L. Sessler, T.
Murai, V. Lynch, M. Cyr, J Am. Chem. SOC.110 (1988) 55861.
R. A. Berger, E. LeGoff, Tetrahedron Lett. 1978, 4225, E. LeGoff, 0.G.
Weaver, J. Org. Chem. 52 (1987) 710.
M. Gosmann, A. Vogt, B. Franck, Liebigs Ann. Chem. f990,163; see also
the communication by Franck et al. in this issue: H. Konig, C. Eickmeier,
M. Moller, U. Rodewald, B. Franck, Angeir. Chem. 102 (1990) 1437:
Angew. Chem Int. Ed. Engl. 29 (1990) 1393; S . Beckmann, T.Wessel, B.
Franck, W. Honle, H. Borrman, H.-G. von Schnering, ihid. 102 (1990)
1439 and 29 (1990) 1395.
For the stereoisomerism of the furan and thiophene macrocycles structurally analogous to the still unknown N,N'-dihydro[22]porphyrin(2.2.2.2), see J. A. Elix, Austr. J. Chem. 22 (1969) 1951 and A.Strand, B.
Thulin, 0.Wennerstrom, Actu Chem Scand. 831 (1977) 521, respectively.
G. Hohlneicher, Universitat Koln, personal communication.
N. Jux, P. Koch, H. Schmickler, J. Lex, E. Vogel, Angew. Chem. 102 (1990)
1429; AnKew. Chem. l n t . Ed. Engl. 29(1990) 1385
H . Scheer, J. J. Katz in K. M. Smith (Ed.): Purphyrins und Metalloporphyrins, Elsevier, Amsterdam 1975, p. 413.
J. Emsley, Chem. Soc. Rev. 9 (1980) 91
J. F. M. 0 t h . Pure Appl. Chem. 25 (1971) 573; R . Gygax, J. Wirz, J. T.
Sprague, N. L. Allinger, Helv. Chim. Acta 60 (1977) 2522; J.-M. Gilles,
J. F. M. Oth, F. Sondheimer, E. P. Woo, J. Chem. SOC.B 1971, 2177.
C,,H,,N,,
dec. above 285 "C, crystals from carbon disulfide; triclinic,
space group Pi, Z = 1, a = 8.460(2), h = 9.352(2), c = 11.021(3) A,
a = 96.27(2), = 100.19(2), 7 = 103.40(2)',
= 1.182 g ~ m - intensi~ ;
ties meassred on an Enraf-Nonius CAD-4 diffractometer [room temperature, AM- = 0.71069 & B,,(max.) = 25'1; refinement (C,N anisotropic. H
isotropic) taking into consideration 1557 reflections with Fo > 4u(F,);
R = 0.043, R, = 0.045. Further details of the crystal structure investigation may be obtained from the Fachinformationszentrum Karlsruhe.
Gesellschaft fur wissenschaftlich-technische Information mbH, W-7514
Eggenstein-Leopoldshafen 2 (FRG), on quoting the depository number
CSD-54913, the names of the authors, and the journal citation.
K. M. Smith in A R. Katritzky, C. W. Rees (Eds.): Comprehensive Heferocyclic Chemistry, Vul. 4 , Pergamon Press, Oxford 1984, p. 377; J. W.
Lauher, J A. Ihers, J. Am. Chem. SOC.95 (1973) 5148
F. R. Longo, E. J. Thorne, A. D . Adler, S. Dym, J H e f e r u q d . Chem. 12
(1975) 1305; J. B. Paine 111, W. B. Kirshner. D . W. Moskowitz, D. Dolphin,
J Org. Chem. 41 (1976) 3857.
The previously unknown pyrrole derivative 9 was obtained from 2-(2cyano-2-ethoxycarbonylvinyl)-3,4-diethyl-5-iodopyrrole
[9] by dehalogenation with zinc in acetic acid [yellow needles (ethanol), m.p. 118 C.
1390
0 VCH Verlagsgesellschuft mbH,
W-6940 Weinheim, 1990
95 %I, Vilsmeyer formylation, and removal of the aldehyde protecting
group [light brown needles (ethanol), m.p. 105- 106"C, SO%]. The expected formation of the corresponding, previously unknown 1,4:7,10: 13,16trisimino[l8]annulene of the same type as Badger's bridged [18]annulenes
[G. M. Badger, J. A. Elix. G. E. Lewis. Austr. J. Chem. 18 (1965) 70; ibid.
19 (1966) 12211 has not been observed so far
[17] Recent reviews- J. E.McMurry, Chem. Rev. 89 (1989) 1513; D. Lenoir,
Synthesis 1989, 883.
11 81 So far obtained as a microcrystalline blue powder with a metallic luster; 'H
NMR spectrum (300 MHz, CDCI,, room temperature): 6 = 11.67 (H-5).
10.19 (H-3). 9.95 (H-12). 9.86 (H-ll), 9.46 (H-8), 9.36 (H-2), 9.30 (H-91,
2.21 (NH), -7.13 (H-6). The couplings of 9 and 2,s-pyrroledicarbaldehyde were carried out by S . BBhm and W Hennig.
Isocorroles: Novel Tetrapyrrolic Macrocycles**
By Stefan Will, Afssaneh Rahbar. Hans Schmickler,
Johann Lex, and Emanuel Yogel*
Dedicated to Professor Albert Eschenmoser
on the occasion of his 65th birthday
Corrole (2), which may be regarded as the aromatic basic
structure of the ring framework of vitamin BI2[l1and which
has been investigated extensively by A . W Johnson and his
co-workers,[2]is formally derived from porphyrin (1) by contraction of the C,, perimeter with expulsion of a meso carbon atom. Compound 2, like 1, exhibits an 187t-electron
main conjugation pathway, but differs from 1 in that it contains three pyrrole-like nitrogen atoms, assumed to be responsible for the ready anion formation in the case of 2. The
spectra of corroles display a close relationship with those of
porphyrins, even though the ring framework deviates noticeably from planarity, presumably owing to steric interactions
' chemistry of corroles,
between the NH h ~ d r 0 g e n s . l ~The
which have not yet been found in nature, is dominated by
their ability to form complexes (metallocorroles) with metal
ions.[2,41
f-J.yJ
HN \
HN
\
'
/
'
\
1
2
3
4
It occurred to us that the formalism relating 1 and 2 structurally might be extended to the porphyrin isomer porphycene (3).['' Our attention was thereby directed to the
previously unknown tetrapyrrolic macrocycle 4, for which
the name isocorrole is proposed. Compound 4, in a planar
conformation, is more strained than 2, so that it was open to
[*I Prof. Dr. E. Vogel. S.Will, A. Rahhar, Dr. H. Schmickler, Dr. J. Lex
[**I
Institut fur Organische Chemie der Universitat
Greinstrasse 4, W-5000 Koln 41 (FRG)
This work was supported by the Deutsche Forschungsgemeinschaft.
0570-0833/90/1212-1390$3.50+.25/0
Angew. Chem. Int. Ed. Engl. 29 (1990) Nu. 12
question whether the compound would possess an aromatic
ring system. In our exploration of the chemistry of 2,7,12,17tetrapropylporphycene (5)J6]we have now discovered aporphycene-isocorrole rearrangemenl, which leads to a stable
isocorrole.
Because of its favorable solubility, compound 5, accessible
on a preparative scale, is a good model compound for the
study of electrophilic and other substitutions on the porphycene ring system, although the pyrrole rings in 5 each
have only one substitutable hydrogen. The expectation that
quantum-mechanical calculations would provide reliable information on the course (substitution pattern) of the reaction of 5 with electrophiles has been frustrated so far, since
the relative reactivities of the CHCH bridge carbons and the
pyrrole carbons determined by the conventional calculationa1 procedures (PPP, CNDO, AM1 , and others) are not con~istent.~']The initially studied bromination of 5 with
bromine in carbon tetrachloride had the surprising result
that halogen substitution occurred at the four available ppyrrolic positions to form the 3,6,13,16-tetrabromo compound 6 before substitution at the nonpyrrolic carbons took
place.[81 If the product of monobromination, 3-bromo2,7,12.17-tetrapropylporphycene(S),is desired, bromine on
a polymeric support is best used as the brominating agent
(see Experimental Procedure).
N(1) ..' N(2)
2.74
A
N ( 1 ) ... N(2')
2.81
A
Fig. 1. Molecular structure of 6. Top: Top view. Bottom: Side view. Selected
bond lengths and other distances (A] and bond angles ["I; standard deviations
ca. 0.009 A and 0.8". The thermal ellipsoids are drawn at the 40% probability
level.
5
-I
7a
7b
The structural proof for 6 and 8 is based on the 'H and
13C NMR spectra; in addition, an X-ray structure analysis" '1 was carried out on 6 (Fig. 1). Compound 6 is a centrosymmetric molecule, whose ring framework practically
retains the planarity found for 3 and 5, but whose bromine
atoms are markedly displaced from the plane of the framework owing to nonbonding interactions. Thus, compound 6
strikingly differs from 2,3,6,7,12,13,16,17-octaethylporphycene," 1' which has the same substitution pattern, since, in
the latter compound, the substituents in the 3,6- and 13,16positions cause a pronounced ruffling of the ring framework.
The "squeezing" of the bromine atoms, revealed in the relatively short Br . . . Br distance of 3.267 8, (sum of the van der
Waals radii: 3.9 A), causes the pyrrole rings to rotate within
the plane of the ring framework and results in angle deformations of up to 6" at the positions where the rings are
joined. Moreover, a reversal of the relative distances within
the N, core (now, N1 . . . N2 < N1 . . . N 2 ) ensues. Because
of partial disorder, the two imino hydrogens are distributed
with half occupancy over each of the four possible positions.
Angex. Chem In[. Ed. Engl. 29 (1990) No. 12
0 VCH
The supposition that steric compression of the bromine
atoms in 6 might facilitate nucleophilic substitutions leading
to a linkage of C3 and C6 was not borne out. Compound 6
reacts only very sluggishly with nucleophiles, as observed for
other hal~pyrroles.['~]
This behavior of 6 allows for the occurrence of a porphycene-isocorrole ring contraction, which
requires a basic medium and is apparently associated with
the presence of the halogen
When 6 is heated with
potassium carbonate in DMF/water (7: 1) under argon to
120 "C (4 h) and the resulting products are chromatographed
on silica gel (chloroform), two fractions are obtained. The
first consists of 6 together with unidentified, decomposable
products and the second contains the isocorrole aldehyde 7.
Crystallization from dichloromethane/hexane affords 7 as
small black-green needles (dec. above 180 "C; yield 34%).
The 'H NMR spectrum of 7 (Table 1) shows a simple
pattern, in agreement with the assumption that 7 undergoes
rapid N H tautomerism, which gives the molecule effective
C,, symmetry: singlets at 6 = 11.45 (aldehyde proton) and
8.77 (H-9,10; '4. = 12.5 Hz), six groups of signals in the
region of 6 = 1.0-3.6 (protons of four pairwise identical
propyl groups), and two strongly broadened signals at
6 = 3.5 (1 NH; involved in hydrogen bonding) and - 2.5
(2 NH), which only become sharp singlets at - 50 "C. Consistent with this spectrum, the 13CNMR spectrum shows 17
= 176.1 Hz) being
signals, that at 6 = 187.72 (CHO;
assigned to the aldehyde carbon. The aromaticity of the ring
system in 7 is apparent from the positions of the resonances
for the two perimeter protons and for the two NH protons
not involved in hydrogen bonding at relatively low and high
field, respectively. The UVjVIS spectrum of 7 contains a
moderately intense Soret band at 1 = 371 nm ( E = 53 100) as
well as a relatively complex system of Q bands. In addition,
however, there is a short-wavelength band at 260 nm
(20 300), which has no counterpart in the spectra of 1,3, and
the known corroles. In the IR spectrum, unlike in the corre-
Verlngsgesellschnfi mbH, W-6940 Weinheim, 1990
0570-0833/90/1212-f391$ 3 50f .25/0
1391
Table 1. Selected physical data for 6, 7, and 8
6 : 'H NMR (300 MHz, CDCI,): 6 = 9.48 (s. 4 H ; H-9,10,19,20), 3.80 (t, XH;
H-2a,7a,12a,17a), 3.60(br.s, 2H,NH),2.12(m, SH;H-2b,7b,12b.l7b), 1.23
(t. 12H; H - 2 ~ , 7 ~ , 1 2 ~ , 1"CNMR(75.5
7~).
MHz, CDCI,): b = 145.55, 142.38,
134.80, 112.38, 111.86, 30.02, 25.22, 14.55. MS (EI, 70eV): mjz 798/796/794/
7921790 ( M e 7 23/74/100/73/17%). 769/767/765/763/761 (14/48/77/50/17), 397
( M 2 e , 16), 82(17), SO(18). IR(Cs1). C[cm-'] = 2956, 2922, 2864, 1552, 1523,
1462.1089,1047,986,922.UV/VIS(CH,CI,): 2,,,[nm](~) = 379(107000), 387
(104000) sh, 591 (36000), 639 (20600), 684 (29000).
7:' H N M R ( ~ O O M H Z , C D C I J :=
~ 11.45(s,'J(C,H) = 176.1 H z , l H ; C H O ) ,
8.77 ( s , 3J(H,H) = 12.5 Hz. 2 H ; H-9.10), 3.55 (t. 4 H ; H-7a,l2a), 3.5 (br. s,
1 H ; NH), 3.25 (m, 4 H , H-2a,l7a), 2.02 (m. 4 H ; H-7b,12b), 1.92 (m, 4 H ;
H-2b.l7b), 1.16(t, 6 H ; H - 7 ~ 1 2 ~1.05
) . (t. 6 H ; H-2c,17c), - 2.5 (br. s, 2H;
NH). "CNMR (75.5 MHz, CDCI,): 6 = 187.72 (CHO). 142.46, 140.77,
136.14, 129.80, 129.29, 126.59, 111.94, 109.26, 108.82, 107.48, 31.25, 29.28,
25.16, 24.59, 14.53, 14.36. MS (FAB): mlz 814/812/810/808/806 ( M e , 231651
100/60/15%). IR(Cs1): C[cm-'] = 3415, 2959, 2868, 1659, 1544, 1456, 1318.
1261, 1132, 1072, 1001, 924; UV/VIS (CH,CI,): 1,, [nm] ( 6 ) = 260 (20300).
371 (53 loo), 386 (39700) sh, 409 (32700) sh, 632 (30 300) sh. 684 (40 800) sh. 708
(48 300).
8: ' H N M R (300MHz, CDCI,): 6 = 10.11 (s, 1 H ; H-6), 9.51 (m. 4 H ; H9,10,19,20), 9.18 (s, 1 H ; H-l6), 9.08 (s, 1 H ; H-13), 3.90 (m, XH; H2a,7a,12a,17a),2.32(m,9H;H-2b,7b,12b,17b,NH3),
1.98(br.s, l H ; N H l ) ,
1.31 (m, 12H; H-2c,7c312c, 17c). 13CNMR (75.5 MHz, CDCI,): b = 148.50,
147.38, 144.86, 144.69, 143.52. 142.40, 138.98, 138.30, 137.79, 133.09, 131.16,
130.57, 123.84, 122.47, 121.66, 114.64, 112.52, 111.83, 109.51, 108.53. 30.47,
30.39. 30.23,29.63,25.70. 25.42,25.11,24.99, 14.55, 14.49. MS (EI, 70eV):mJz
5581556 ( M a , 20/18%), 5291.527 (7/7), 82 (99, 80 (100). IR(Cs1):
B[cm-'] = 2950, 2918, 2855, 1555, 1455, 1210, 1035, 1012,936. 803. UVjVIS
(CH,CI,): A,,, [nm] ( B ) = 372 (121 000), 383 (101 000). 565 (34000). 608
(28600). 643 (44000).
sponding spectra of 3, 5, and 6, an NH stretching band
(341 5 cm- ') is observed and is presumably due to the imino
hydrogens not participating in hydrogen bonding. The EI
mass spectrum contains only signals of fragment ions of low
mass, whereas FAB ionization results in a single peak, due to
the molecular ion.
An X-ray structure analysis of 7[15'(Fig. 2) reveals the
nonplanarity of the isocorrole ring framework, which is
mainly due to the steric interactions between the imino hydrogens, and, in addition, confirms the porphyrinoid nature
of the compound. Whereas pyrrole rings B and C, which,
together with C-9 and C-10, form a porphycene partial structure (dipyrroethene structure), lie in the mean plane of the
ring framework, rings A and D are each twisted out of this
plane by 23" but in opposite directions. A consequence of the
torsion of rings A and D is that the N . . N contact distances are nearly equal (ca. 2.7 A). The ring framework of 7
thus deviates more strongly from planarity than that of
corroles, since a structure analysis of 8,12-diethyl2,3,7,13,17,18-hexamethylcorrole(9)[31has shown that, in
this molecule, pyrrole rings A, B, and C are arranged in a
nearly planar fashion and ring D is twisted by only 8-10'.
Interestingly, the imino hydrogens in 7 are not statistically
disordered over the four nitrogens, as observed for 9 and the
porphycenes 3,5,and 6, but rather can be localized in compliance with the NH tautomer 7a. As inferred from the situation for 3 and 5, a strong N-H . . . N hydrogen bond should
exist between N2 and N3. The similar bond lengths in the
nonpyrrolic perimeter CC bonds, especially in combination
with the length relation C,-C, > Cp-C,,['61 observed for the
pyrrole rings, support the aromatic character of 7. The isocorrole system once again corroborates the finding that the
ring frameworks of porphyrins and their analogues can be
considerably deformed without a serious loss of aromaticity.[17]
Preliminary reactions of 7 with di- and trivalent metal ions
led to metal complexes, but these usually decomposed rapidly. An exception was the complex obtained with Co" ions in
the presence of pyridine. According to NMR spectroscopic
investigations, this complex has the structure of a diamagnetic Co"' isocorrole complex with two molecules of coordinatively bound pyridine.
Experimental Procedure
8: Compound 5 (100 mg, 0.2 mmol) in 40 mL of dichloromethane and 40 mL
of acetic acid was treated at 0°C under argon with 260 mg of Amberlyst A-26
(Br, form)[9] (corresponding to 0.4 mmol of bromine). The reaction mixture
was stirred for 2 h and then filtered. The solvent was removed and the residue
chromatographed on silica gel (column: 100 x 5 cm) with hexane/dichloromethane (6: 1). The first fraction (also the main fraction) contains the monobromide 8, which, after crystallization from hexane, was obtained as violet needles
with a metallic luster; m. p. 199-200°C. yield 93 mg (80%).
6 . Bromine (225 mg, 1.4 mmol) in 20 mL of carbon tetrachloride was added
over 10 min at room temperature to a vigorously stirred mixture of 5 (100 mg,
0.2 mmol) in 40 mL of carbon tetrachloride and a buffer solution (1 g of sodium
acetate in 40 mL of water). The resulting reaction mixture was stirred for 1 h.
The organic phase was washed with a saturated solution of sodium thiosulfate
and with water and then chromatographed on silica gel (column. 100 x 4 cm)
with hexane/dichloromethane (6: 1). Three fractions were obtained: the first
contained a complex mixture of polybromides, the second 3,6,13-tribromo2,7,12,17-tetrapropylporphycene[lO],
and the third 6.Crystallization from hexaneldichloromethane afforded 6 as violet needles with a metallic luster; dec.
above 300 "C, yield 67 mg (40%).
Received: July 20, 1990 [Z 4082 IE]
German version: Angew. Chem. 102 (1990) 1434
CAS Registry numbers
5, 106562-37-2; 6, 130670-37-0; 7, 130670-40-5; 7.CH,C12, 130698-79-2; 8,
130670-39-2, porphycene, 100572-96-1; 2-bromporphycene, 130670-38-1,
3,6,13-tribromo-2,7,12,17-tetrapropylporphycene,
130698-78-1,
N(1)
N(2)
2.65
A
N(2)
N(3)
2.76A
N(l)
N(4)
2.61
A
N(3)
N(4)
2.64A
Fig. 2. Molecular structure of7. Same projections as in Fig. 1 (standard deviation ca. 0.012 A). Side view without propyl groups.
1392
0 VCH
VerlagsgeselIschafr mbH. W-6940 Weinheim, 1990
[l] A. Eschenmoser, Angew. Chem. 100 (1988) 5 ; Angew. Chem. Int. Ed. Engl.
27 (1988) 5 .
[2] A. W. Johnson, I. T. Kay, J. Chem. SOC.1965, 1620; A. W. Johnson, Pure
Appl. Chem. 23 (1970) 375; A. W. Johnson in K. M. Smith (Ed.): Porphyrins and Melalloporphyrins, Elsevier, Amsterdam 1975, p. 729; R.
Grigg in D. Dolphin (Ed.): The Porphyrins, Vol. II, Academic Press, New
York 1978, p. 327; N. S. Genokhova,T. A. Melent'eva, V. M. Berezovskii,
Usp. Khim. 49 (1980) 2132 [Russ Chem. Rev. 49 (1980) 10561; T.A.
Melent'eva, ibid. 52 (1983) 1136 [ibid. 52 (1983) 6411.
[3] For theX-ray structure analysis o f a corrole, see: H. R. Harrison, 0. J. R.
Hodder, D. C. Hodgkin, J. Chem. SOC.B 1971,640.
(41 P. 5. Hitchcock. G. M. McLaughlin, J. Chem. SOC.Dalton Trans. 1976,
0570-0833J90/1212-1392S 3.50+.25/0
Angew. Chem. In!. Ed. Engl. 29 (1990) No. 12
1927: Y. Murakami, S. Yamada, Y Matsuda, K. Sdkata, B U N . Chem. Soc.
Jpn. 51 (1978) 123; Y. Murakami, Y. Matsuda, K. Sdkata, S. Yamada, Y.
Tanaka. Y. Aoyama, [bid. S4 (1981) 163.
151 E. Vogel, M. Kocher, H. Schmickler, J. Lex, Angebv. Chem. 98 (1986) 262;
Angen.. Chem. In?. Ed. Engl. 25 (1986) 257; P. F. Aramendia, R. W. Redmond, s. Nonell, W. Schuster. s. E. Braslavsky, K. Schaffner, E. Vogel,
Phorochem. Photohiol. 44 (1986) 5 5 5 ; E. Vogel, M. Kocher, M. Balci, I.
Teichler. J. Lex. H. Schmickler, 0. Ermer, Angew. Chem. 99 (1987) 912;
Angew. Chem. Int. Ed. Engl. 26 (1987) 931; B. Wehrle, H.-H. Limbach, M.
Kocher. 0. Ermer, E. Vogel, ihid. 99 (1987) 914 and 26 (1987) 934; H.
Levanon, M. Toporowicz, H. Ofir, R. W. Fessenden, P. K. Das, E. Vogel,
M. Kocher. K. Pramod, J. Phys. Chem. 92 (1988) 2429; J. Schlupmann, M.
Huber. M. Toporowicz, M. Kocher, E. Vogel, H. Levanon, K. Mobius, J.
Am. Chem. Soc. I10 (1988) 8566; E. Vogel, M. Kocher, J. Lex, 0. Ermer,
Isr J. Chem. 29 (1989) 257; E. Vogel, Pure Appl. Chem. 62 (1990) 557.
161 E. Vogel, M. Balci, K. Pramod, P. Koch, J. Lex, 0. Ermer, Angew. Chem.
99 (1987) 909; Angew. Chem. Int. Ed. Engl. 26 (1987) 928; M. W. Renner,
A. Formdn, W. Wu, C. K. Chang, J. Fajer, J. Am. Chem. Soc. t l l (1989)
8618; L. R. Furenlid, M. W. Renner, K. M.Smith, J. Fajer, ibrd. 112(1990)
1634.
[7] We thank Prof. C . Hohlneicher (Universitlt Koln) and Prof. R. Gleiter
(Universitlt Heidelberg) for performing these calculations.
[8] In the case of the porphycene parent compound, reaction with bromine
also leads exclusively to P-pyrrolic bromination, but the bromine substituent is found in the 2-position, which is occupied by a propyl group in 5.
2-Bromoporphycene is the only isolated monobromination product (unpublished results with K . Pramod and H.-J. Dunnwuhf). This substitution
pattern for bromination is different from that of porphyrin, for which
regioselective substitution at the methine bridge leads to the formation of
5-bromoporphyrin [H. J. Callot, E. Schaeffer, J Chem. Res. ( S ) t978 51;
L. R. Nudy. H. G . Hutchinson, C. Schieber, F. R. Longo, Tetrahedron 40
(1984) 23591, even though PPP calculations indicate that electrophilic
attack on the 0-pyrrolic carbon should have occurred [J. V. Knop. J.-H.
Fuhrhop, Z. Naturforsch. B 2s (1970) 7291. The P-pyrrolic bromination of
porphyrin observed earlier by E. Samuels, R. Shuttleworth, and T. S.
Stevens [J Chem. Soc. C 1968,1451could not be reproduced by I? R . Longo
et al. (cited above).
[9] A. B0ngini.G. Cainelli, M. Contento, F. Manescalchi, Synthesis 1980,143.
[lo] Like 6 , the tribromo compound (m,p. 269-270°C), which is currently
being investigated in more detail. can be made the main product.
[ l l ] C,,H,,Br,N,,
dec. > 300”C, crystals from hexane/dichloromethane; triclinic, space group Pi, 2 = 1; u = 5.686(1), b = 10.208(2), c =
13.839(3)A, a = 96.13(2), fi = 93.27(2), y = 96.16(2)”; ecalcd
= 1.67 g
cm-3; intensities measured o n a four-circle diffractometer [room temperature. A,+ = 0.71069 A, $,,(max) = 25”]; empirical absorption correction,
refinement (C, N, Br anisotropic, H isotropic) taking into consideration
1677 reflections with Fo > 40(F0); R = 0.063, R , = 0.073 1181.
is of interest, since it reacts with
[12] 2,3,6,7,12,13,16,17-Octaethylporphycene
zinc and several other metals to afford planar complexes that are more
stable than the corresponding metal complexes of 3 and 5 : E. Vogel, P.
Koch, unpublished results.
1131 A. Gossauer: Die Chemie der Pyrrole, Springer, Berlin 1974, p. 326.
[14] The porphycene-isocorrole rearrangement suggests associations with the
ring-contraction step in the biosynthesis of the corrin ring of vitamin
B,,[l]. To the best of our knowledge, a contraction of porphyrins to
corroles has not been observed so far.
[IS] C,,H,,Br,N,OCH,CI,,
dec. > 18O”C, crystals from dichloromethane;
triclinic, space group, Pi, Z = 2; a = 8.443(2), b = 13.898(3). c =
16.034(4) A, a = 66.15(2), fi = 88.01(2), y = 87.02(2)”, ecSlcd
= 1.75
g cm-’; intensities measured on a four-circle diffractometer [room temperature, A,, = 0.71069 A, O,,(max) = 25”]; empirical absorption correction; refinement (C, N, 0, CI, Br anisotropic, H isotropic) taking into
consideration 2301 reflections with Fo > 40(F0); R = 0.074, R , =
0.063[181.
1161 K M. Smith in A. R. Katritzky, C. W. Rees(Eds.): Comprehensive Heterocwhc Chemistry, VoL 4, Pergamon Press, Oxford 1984, p. 386.
1171 Porphyrins: T. P. Wijesekera, J. B. Paine 111, D. Dolphin, F. W. B. Einstein,
T. Jones, J Am. Chem. Soc. f0S (1983) 6747; N-protonated porphyrins: N.
Hirayama, A. Takenaka, Y. Sasada, E.-I. Watanabe, H. Ogoshi, Z.-I.
Yoshida. J. Chem. Soc. Chem. Commun. 1974, 330; N-substituted porphyrins: D. K. Lavallee: The Chemistry and Biochemistry of”-Substituted
Porphyrins, VCH Publishers, New York/Weinheim 1987; N,K,N,N”-tetramethyloctaethylporphyrin dication: B. Franck, Angew. Chem. 94
(1982) 327, Angew. Chem. Int. Ed. Engl. 21 (1982) 343; M. Gosmann,
Dis.sertarion. Universitdt Munster 1986 (see also following reference); tetrdthiaporphyrin dication: E. Vogel, P. Rohrig, M. Sicken, B. Knipp, A.
Herrmann, M. Pohl, H. Schmickler, J. Lex, Angew. Chem. 10t (1989) 1683;
Angew. Chem. Inr. Ed. Engl. 28 (1989) 1651.
[18] Further details of the crystal structure investigation may be obtained from
the Fachinformationszentrum Karlsruhe, Gesellschaft fur wissenschaftlich-technische Information mbH, W-7514 Eggenstein-Leopoldshafen 2
(FRG), on quoting the depository number CSD-5491 I , the names of the
authors. and the journal citation.
Angew. Chem. inr. Ed. Engl. 29 (1990) No. 12
0 VCH
Synthesis of a Bisvinylogous Octaethylporphyrin**
By Hartmann Konig, Christian Eickmeier, Manfred Mijller,
Ute Rodewald, and Burchard Franck *
In memoriam Hans Fischer
Octaethylporphyrin (OEP, 2), first synthesized in 1929 by
Hans Fischer et al.,“’ is one of the most important and most
investigated porphyrins.[’] Here we describe an efficient synthesis of the title compound 1, which is extremely stable and
markedly aromatic. Thus, the crystal structure analysis of
the bistrifluoroacetate of 1 revealed that the conjugated
perimeter is planar and its bonds largely equal in length. The
‘H NMR spectrum indicates an intense diamagnetic ring
current. Furthermore, 1 is the first annulene for which the
protons inside and outside the aromatic system exhibit a
large difference in reactivity. According to the nomenclature
for vinylogous porphyrins,[” 1 is named [22]octaethylporphyrin(l.3.1.3).
E
t
a
E
t
E
HN
Et
\ \
/
/
Et
/
Et
Et
\‘
t N
a% E
t
/
Et
/
Et
Et
1
Et
2
An initial synthetic attempt based on the procedure of
MacDonald et al.[31was unsuccessful owing to the low stability of the required pyrromethene and pyrropropene intermediates. However, the “biladiene synthesis path”,[41which is
of less general use in porphyrin syntheses, proved to be a
more efficient route to 1. The key compound is the previously unknown bisvinylogous biladiene 5,which was obtained
in 81 % yield by condensation of 316]and 4[5b1
(Scheme l),
both of which are readily accessible from 3,4-diethylpyrr~le.[~’
Condensation of biladiene 5 to give porphyrin 1
was accomplished by heating 5 with CH,O/MeOH followed
by in situ oxidation with 2,3-dichloro-5,6-dicyano-l,4-benzoquinone (DDQ) (42% yield based on 5).[81
The ‘H NMR spectrum of 1 in CDCl,/l% trifluoroacetic
acid (TFA) (Table 1) shows that the signals for the inner and
outer bridge protons are strongly shifted upfield and downfield, respectively; the spectrum spans an unusually broad
Table 1. ‘H NMR data for [22]octaethylporphyrin 1 and for the hexadeuterdted [22]octaethyfporphyrin 6 in CDCI,/l% TFA.
1
Proton
H‘
Hb
H‘
NH
6
J
11.96(s)
12.78(d)
-9.54(t)
-6.61(s)
13.9
13.9
-
6
d
[Hzl
~
-9.71(s)
- 6.50(s)
[*] Prof. Dr. B. Franck, DipLChem. H. Konig, C. Eickmeier
Organisch-chemisches Institut der Universitat
Orleansring 23. W-4400 Munster (FRG)
Dr. M. Moiler, DipLIng. U. Rodewald
Anorganisch-chemisches Institut der Universitat Munster
[**I Novel Porphyrinoids, Part 10. This work was supported by the Deutsche
Forschungsgemeinschaft, the Fonds der Chemischen Industrie, and BASF
AG (Ludwigshafen). Part 9: [7a]
Verlagsgesellschafr mbH, W-6940 Weinheim. 1990
OS70-0833/90/t212-1393$3.50+ .25/1)
1393
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