In this paper an account is given of the author's use of 4-alkynoic acid derivatives in the synthesis of members of the chlorin, bacteriochlorin and corrin classes of macrocyclic tetrapyrroles. In the case of chlorins we employed a novel 2+2 condensation to prepare both C,D-symmetric and non-symmetric chlorins, made possible by the ready availability of highly substituted semicorrins derived from 4-alkynoic acids. Alkyne acids also played a prominent role in a new 16 pi-electrocyclization route to bacteriochlorins, and in iterative syntheses of semicorrins and secocorrins related to vitamin B12. Mechanistic studies provided insight into the nature of these Pd(0)-catalyzed coupling/cyclization reactions. Finally, we describe enantioselective syntheses of ring-C and ring-D alkyne acids for a projected synthesis of cobyric acid.

4-Alkynoic acids in the synthesis of biologically important porphyrinoids

ACS Spring Meeting 2021

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