In:
Journal of Porphyrins and Phthalocyanines, World Scientific Pub Co Pte Ltd, Vol. 06, No. 11 ( 2002-11), p. 685-694
Abstract:
An investigation of the reactions of metallo-5-nitro-2,3,7,8,12,13,17,18-octaethylporphyrins with Grignard reagents, benzyl oxide, phenoxide and benzenethiolate nucleophiles shows that, except for benzenethiolate reactions, they are less efficient than related reactions of metallo-2-nitro-5,10,15,20-tetraarylporphyrins. Treatment of free-base and nickel(II) 5-nitro-octaethylporphyrin with the “soft” nucleophile benzenethiolate in DMF affords the corresponding 5-phenylthioporphyrins in 61 and 72% yield, respectively, by ipso-substitution of the nitro group. In contrast, with methylmagnesium iodide and benzyl oxide, “hard” nucleophiles, attack is at the diagonally opposite 15-position of the ring to give 15-substituted 5-nitroporphyrin while with phenoxide and more substituted Grignard reagents, electron-transfer reactions lead to denitration to (metallo)-octaethylporphyrin or reduction to the corresponding 5-aminoporphyrin. The lower efficiency of the latter reactions, compared to those on 2-nitro-tetraarylporphyrin analogues, is a consequence of two factors, higher energies being required for initial nucleophilic attack as macrocyclic aromaticity is lost in intermediates and the susceptibility of the resultant “non-aromatic” intermediates to further attack.
Type of Medium:
Online Resource
ISSN:
1088-4246
,
1099-1409
DOI:
10.1142/S1088424602000816
Language:
English
Publisher:
World Scientific Pub Co Pte Ltd
Publication Date:
2002
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