Accessing a key intermediate for sub(oxa)porphyrins from a sustainable raw-material—Cashew apple bagasse

Furan-2,5-diylbis(phenylmethanol) is a key intermediate to access sub(oxa)porphyrins. Previously, this key intermediate was accessible from fossil-derived furan using highly dangerous lithium reagents. Presently, we have produced this key intermediate from cashew apple bagasse (CAB), via the formation of 5-hydroxymethylfurfural (HMF). CAB is non-food biomass containing cellulose and hemicellulose. From the CAB, we have obtained the HMF in the yield of 310 mg/g of CAB. The Response Surface Methodology (RSM) optimized condition for efficient conversion of CAB to HMF is (i) temperature at 180 °C, (ii) 1:1 mol ratio of catalysts (ZnSO4/NaHSO4), and (iii) reaction duration of 3 h. CAB-derived HMF is treated with an oxidizing agent pyridinium chlorochromate (PCC) to obtain 2,5-diformylfuran (DFF). DFF is converted into furan-2,5-diylbis(phenylmethanol) in a reaction with phenylmagnesium bromide. Based on the TD-DFT analysis of sub(oxa)porphyrins, it is concluded that the absorption behavior of sub(oxa)porphyrins can be tuned by introducing electron-withdrawing groups into the phenyl ring of the sub(oxa)porphyrins.