N-Substituted Corroles

Considerable effort has been directed toward the preparation of N-substituted corroles. This research was inspired, presumably, by the fact that similar N-substituted species can be obtained in the porphyrin series. In any event, objectives associated with this line of investigation include assessing the extent to which a 

In terms of spectroscopic characteristics, it was determined that the UV-vis absorption spectrum of the 7V(21)-methyl corrole 2.194 is very similar to that of the normal, N-unsubstituted corrole. On the other hand, the UV-vis spectrum of the V(22)-methyl corrole 2.195 was found to be markedly different from that of either the N(21)-methyl-substituted species 2.194 or the N-unsubstituted corrole 2.6. Furthermore, in the relevant H NMR spectra, the signals of the internal and external protons of the AT(22)-methyl corrole 2.195 were found to be spread out compared to those of the N(21)-methyl or N-unsubstituted species. This latter finding was 

In other work involving substitution at a single nitrogen, Johnson and co- 

Interestingly, the second methyl group introduced into 2.196 or 2.197 was found to be incorporated at a greater rate than the first. This led to the suggestion that both the nucleophilicity and basicity of the mono-A -methyl corroles were greater that of the parent, N-unsubstituted corrole system. In fact, A -alkyl corroles do appear to be quite basic in that, unlike simple corroles, they do not form anions when treated with base. Moreover, the A (21),jV(22)-dimethyl corrole iodide 2.209 is reportedly so basic that it cannot be isolated in its free-base form.  

In 1968, Johnson and coworkers reported the reaction of the nickel(II) corrole 

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An alternative approach to preparing N-substituted cobalt(II) corroles was... 

The preparation of the N(21)- and N(22)-substituted methyl corroles 2.196 and 2.197 has also been described, as have the N(21)- and N(22)-ethyl- and allyl-substituted species 2.198-2.203 (Scheme 2.1.67). Additionally, methylation reactions involving 3,17-carbethoxy corrole 2.102 and methyl iodide have been carried out using diisopropylethyl amine as the base. In this instance, in contrast to what happens in the all-P-alkyl series, the A(22)-methyl corrole 2.205 forms as the major product (by a nearly 2 1 margin over the N(21)-substituted alternative, 2.204) (Scheme 2.1.68). Interestingly, the same paper that describes this latter chemistry also reports an alternative synthesis of A(21)-methyl-3,17-carbethoxy corrole 2.204. In this approach, the thiaphlorin 2.101 was methylated using methyl iodide in diisopropylethyl amine to afford the N-methylated product 2.206 (Scheme 2.1.69). This latter species was then subject to a heat-induced sulfur extrusion. This gave the A(21)-methyl corrole 2.204 in 85% yield. A clear advantage of this stepwise procedure was that it allowed the A(21)-methyl-3,17-dicarbethoxy corrole 2.204 to be prepared selectively. 

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