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A new synthesis of porphyrins via a putative trans-manganese(iv)-dihydroxide intermediate

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Abstract

A new method for the synthesis of meso-substituted porphyrins was developed. In this two-step methodology, the first step involves the condensation of pyrroles/dipyrromethanes with aldehydes in a water–methanol mixture under acidic conditions. The second step involves manganese induced cyclization followed by oxidation via PhIO/O2. This methodology has been useful for the synthesis of a wide range of trans-A2B2 porphyrins and also symmetric porphyrins in moderate to good yields. A detailed investigation of the manganese induced cyclization reaction has allowed us to characterize a Mn–porphyrinogen complex. A series of analytical and spectroscopic techniques and DFT calculations have led us to the conclusion that the putative intermediate species are trans-manganese(IV)-dihydroxide complexes. EPR and magnetic susceptibility measurements helped us to assign the oxidation state of the manganese complexes in their native state. The assumption of trans-manganese(IV)-dihydroxide as the true intermediate for this porphyrin synthesis has been authenticated via in situ UV-Vis experiments. This new methodology is certainly different from other previously reported methodologies in many aspects and most importantly these reactions can be easily performed on a gram scale for the synthesis of porphyrins.

Graphical abstract: A new synthesis of porphyrins via a putative trans-manganese(iv)-dihydroxide intermediate

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Article information


Submitted
04 Sep 2019
Accepted
20 Dec 2019
First published
23 Dec 2019

Dalton Trans., 2020, Advance Article
Article type
Paper

A new synthesis of porphyrins via a putative trans-manganese(IV)-dihydroxide intermediate

S. Mondal, K. Sahu, B. Patra, S. Jena, H. S. Biswal and S. Kar, Dalton Trans., 2020, Advance Article , DOI: 10.1039/C9DT03573G

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