Catalytic Hydrogenation of meso ‐Octamethylporphyrinogen (Calix[4]pyrrole)

Hydrogenation of meso ‐octamethylporphyrinogen (calix[4]pyrrole) with a number of heterogeneous catalysts under different experimental conditions has been investigated. GC‐MS analyses of the reaction mixtures showed the formation of one to four products in low to moderate yields: three of them were diastereoisomers of the product derived from half‐hydrogenation of the substrate, and displayed alternating pyrrolidine and pyrrole rings, while the fourth was the all‐ cis saturated product. An acidic medium was necessary to achieve hydrogenation. However, the use of too strongly acidic solvents or additives was detrimental to the stability of the substrate and/or the catalyst.