Diels–Alder\nCycloaddition of 2,5-Bis(hydroxymethyl)furan\n(BHMF) and <i>N</i>‑Phenylmaleimide Derivatives

Currently, amidst atmospheric menace where natural calamities\nsuch\nas wildfire and floods are becoming more frequent than ever, biobased\nderivatives offer a sustainable alternative to conventional ways,\nfor instance, petrochemical commodities. Biobased products, obtained\nfrom agricultural waste, including 5-(hydroxymethyl)furfural (HMF),\n2,5-bis(hydroxymethyl)furan (BHMF), and 2,5-furandicarboxylic acid\n(FDCA) are promising chemical platforms in the biorefinery, which\nis yet to be explored. The Diels–Alder cycloaddition of BHMF\nand <i>N</i>-phenylmaleimide derivatives under optimal reaction\nconditions is investigated in this report. First, HMF is reduced to\nBHMF in the presence of NaBH<sub>4</sub>, and then the Diels–Alder\nreaction of BHMF and <i>N</i>-phenylmaleimide derivatives\nis investigated to produce Diels–Alder adducts. All novel compounds\nare synthesized in acceptable yields and effectively characterized\nby employing important techniques such as one-dimensional (1D) NMR\nspectroscopy (<sup>1</sup>H, <sup>13</sup>C, DEPT-90, and DEPT- 135),\ntwo-dimensional (2D) NMR spectroscopy (<sup>1</sup>H–<sup>1</sup>H COSY, <sup>1</sup>H–<sup>13</sup>C HSQC, and <sup>1</sup>H–<sup>13</sup>C HMBC), IR spectroscopy, elemental analysis,\nmass spectrum (QTOF), and single-crystal X-ray diffraction (SC-XRD).\nFurthermore, this study underlines the necessity of sustainable synthetic\nmethodologies and gives critical insights into the progress of ecologically\nfriendly methodologies, providing a new avenue as a tunable precursor\nfor the challenging functionalized polymer in the future.