| Abstrakt: |
Porphyrin derivatives have found diverse applications due to their attractive photophysical and catalytic properties, but remain challenging to synthesize, particularly at scale. Porphyrin synthesis thus stands to benefit from the more controlled environment, opportunities for efficient optimization, and potential for scale-up available in flow. Here, we have transferred Lindsey porphyrin synthesis into flow, enabling controlled timing for oxidation and neutralization steps and real time monitoring of the reaction mixture with inline UV–Vis analysis. For tetraphenyl porphyrin (TPP), inline UV–Vis showed the presence of protonated TPP, formed due to residual acid. Thus, inline monitoring allowed optimization of the neutralization step to improve yield. Three further porphyrin substrates were produced in flow; in two cases, the yield from inline UV was significantly higher than the yield from post-purification, identifying further yield losses that could be recovered by modifying the purification step. The workflow presented here can be adapted to multiple substrates to systematically optimise porphyrin yield, reducing the time needed to develop scalable routes to these valuable compounds. Highlights: Four meso-substituted porphyrins are formed via a continuous flow process incorporating condensation, oxidation, and neutralization. Inline UV–Vis is used to identify the formation of unwanted protonated porphyrin and to optimise the neutralization step. Monitoring yield via inline UV–Vis highlights yield losses during work-up, highlighting the need for improved purification processes for less stable substrates. [ABSTRACT FROM AUTHOR] |
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