Title

Orientation of nucleophilic substitution in π-cation radicals or π-dications from meso-substituted metalloporphyrins

Document Type

Article

Publication Date

1-1-1977

Abstract

Treatment of meso-substituted metalloporphyrins [meso -substituent = OCOCF3, OCOCH3, OMe, CHO, CN, Cl; metal = Zn(II) or Cd(II)] with thallium(III) trifluoroacetate, followed by an acidic work-up, gives the corresponding β-substituted α-oxophlorins which were either characterised as such or else further derivatised. In all cases the major (or only) disubstitution product has the αβ orientation at the meso positions, indicating that the existing meso substituent directs the incoming one (trifluoroacetate) into the flanking, rather than opposite, meso position of the intermediate π-cation radical or π-dication. In contradistinction, meso substituted zinc(II) porphyrins which are able to lose protons (e.g. α-oxophlorins or α-aminoporphyrins) react with thallium(III) trifluoroacetate, and after a work-up with HCl the corresponding γ-chloro-α-oxophlorin or γ-chloro-α-aminoporphyrin is obtained. © 1977.

Publication Source (Journal or Book title)

Tetrahedron

First Page

629

Last Page

633

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