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Novel Synthesis of Octaalkyl- and Octaisoalkylporphyrins.

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Interestingly, in the related [Pt(SnC13)3(PEt3)2]e,which
we assume has the same structure as 1, 1J('9sPt,3'P)is only
1460 Hz. The Pt- and Sn-NMR parameters are similar to
those for 1 and 2. This 'J('95Pt,3'P) value is quite modest
when compared to the values of 2400-2600 Hz often
found in tran~-[PtCl~(PR,)~]
complexes and still much
smaller than the value 2014 Hz found in the five-coordinate tetradentate chelate complex [Pt(SnCl,){P(oAsPhzC6H4),}]in which P and Sn occupy pseudoaxial positions. This suggests a relatively weak Pt-P bond in the
anion [Pt(SnC13)3(PEt3)21".
Novel Synthesis of Octaalkyl- and
By Henry Jacques Callor*, Abderrazak Louati, and
Maurice Gross
Octaalkylporphyrins and particularly octaethylporphyrin l a are the simplest and most useful models for natural
porphyrins, and are accessible through multistep syntheses[']. We have now found an alternative reaction sequence (Scheme 1) which takes advantage of the symmetry
of the products and their precursors, and which permits for
the first time, the synthesis of an octaisoalkylporphyrin,
the isopropyl derivative lc.
Fig. 1. Structure of anion 1 in crystals of the PPN salt of 1. Bond lengths
[pm]: PtAsl 244.5(2), PtAs2 242.7(2), PtSnl 261.2(1), PtSn2 261.4(2), PtSn3
257.9(1), SnCl 238.0+ 1.0(7) (average value).-Bond angles I"]: AsIPtAs2
177.7(6), SnlPtSn2 117.1(4), SnlPtSn3 122.9(4), Sn2PtSn3 119.9(5), AslPtSnl
88.6(1), AslPtSn2 90.7(1), AslPtSn3 88.4(1), As2hSnl 92.5(1), As2PtSn2
90.6(1), As2PtSn3 89.2(1).
The coordination geometry around the Pt atom in 1
(Fig. I ) is distorted trigonal bipyramidal, with the AsMe,
ligands in axial positions. The average PtSn bond length is
260.2 f 2.0( 1) pm. This is slightly larger than the average
equatorial PtSn bond lengths in [Pt(SnC13)s]3e3 (257.2)["],
but considerably longer than the PtSn bond in
[PtC1(SnC13)(PhC(NH2)=NOH)(PEt3)] 4 (250.1)1"1. The
average PtAs distance in 1 is also quite long (243.6 f 1.3(2)
pm) relative to that in the complexes sym-trans[Pt,C14(As M e3)J (230.8) and trans-[ PtCI,N(C H3)=C H--(pCH3C6H4)(AsEt3)] (234.6). The SnCl bonds in 1 average 238.0f 1.0(7) pm and are in good agreement with the
value of 237.2 pm found for the equatorial SnCI, ligands in
3, but longer than the SnCl bonds in 4 (234.0).
Given the rather long PtSn and PtAs bond lengths in 1
and the small coupling constant 'J('9sPt,3'P) for the PEt3
complex, ligand dissociation is not unexpected. It is probable but not certain that an SnCIF ligand leaves the coordination sphere of Pt to produce the known [Pt(SnCI,),L2]
Received: October 7, 1981 [Z 42 IE]
German version: Angew. Chern. 94 (1982) 310
The complete manuscript of this communication appears in:
Angew. Chem. Suppl. 1982, 755-760
[I] H. Itatani, J. C. Bailar Jr., Ind. Eng. Chem. Prod. Res. Deu. I 1 (1972)
[4] P. S. Pregosin, S. N. Sze, Helu. Chim. Acta 61 (1978) 1848.
[6] K. A. Ostoja Starzewski, P. S. Pregosin, Angew. Chem. 92 (1980) 323; Angew. Chem. In[. Ed. Engl. 19 (1980) 316.
[lo] J. H. Nelson, N. W. Alcock, Inorg. Chem.. in press.
[ I I] A. B. Goel, S . Goel, 0. Vanderveer, Inorg. Chim. Acfo 54 (1981) L5.
Angew. Chem. Int. Ed. Engl. 21 (1982) No. 4
R\ CH-C$
-d?- R'O-Ck
Scheme I (Section). Synthesis of octaalkylporphyrins l a and l b and octaisoalkylporphyrin l c [a, R=C2H5; b. R=n-C4Hu; c, R=CH(CH3)2]. A :
anodic oxidation in methanol/NaClO4/2,6-lutidine;
B: benzyl carbamate in
acetic acid (isolation of 3 not necessary); C : HJPd in methanol; D: formaldehyde/02/acetic acid/pyridine. R = CIH5.
Anodic oxidation['] of alkenyl alkyl ethers 2a-c gave
acetals 3a-c, which were cyclized to afford pyrroles 4a-c
using benzyl carbamate in acetic acid [4a, yield 27%,
m.p. <20"C, 'H-NMR (CDCI,): 6 = 1.15 (t; 6H), 2.36 (q,
4H), 5.28 (s, 2H), 6.99 (s, 2H), 7.35 (s, SH)]. The unstable
acids 5a-c obtained by removal of the protecting groups
react with formaldehyde in presence of air[,] to furnish octaethyl- la, octabutyl- lb, and octaisopropylporphyrin l c
(yields relative to 4 : 52, 35, and 43%, respectively).
Received : January 26, 198I ,
revised form: February 17, 1982 [Z 44 IEl
German version: Angew. Chem. 94 (1982) 297
The complete manuscript of this communication appears in:
Angew. Chem. Suppl. 1982. 718-721
[*I Dr. H. J. Callot
Laboratoire associe au C.N.R.S. 31
Dr. A. Louati, Prof. M. Gross
Equipe de recherche associee au C.N.R.S. 468
lnstitut de Chimie, Universite Louis Pasteur
1 rue Blaise Pascal, F-67008 Strasbourg Cedex (France)
[I] Most recently published syntheses of (a) octaethyl- and (b) octaalkylporphyrins: a) J. B. Paine 111, W. B. Kirshner, D. W. Moskowitz, D. Dolphin,
J. Org. Chem. 41 (1976) 3857; C . B. Wang, C. K. Chang, Synfhesis 1979,
548. b) K. S . Chamberlin, E. Legoff, Heterocycles 12 (1979) 1567.
(21 D. Koch, H. SchBfer, E. Steckhan, Chem. Ber. 107 (1974) 3640.
131 A. Treibs, N. Haberle, Jusrus Liebigs Ann. Chem. 718 (1968) 183.
D Verlag Chemie GmbH. 6940 Weinheim. 1982
0570-0833/82/0404-028S $ 02.50 o
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synthesis, octaisoalkylporphyrins, octaalkyl, novem
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