Synthesis of acetyl-substituted tetrahydrobenzofuran and tetrahydronaphthalene via cascade Diels-Alder cycloadditions and dehydration of renewable furanics

A acetyl-substituted tetrahydrobenzofuran, 1-(4,5,6,7-tetrahydro-1-benzofuran-6-yl)ethenone (6-AcBZOF) and a acetyl-substituted tetrahydronaphthalene, 1-(1,2,3,4-tetrahydronaphthalen-2-yl)ethenone (2-AcTNAPH) were conveniently synthesized from renewable furanics by cascade Diels-Alder and dehydration reactions. The Diels-Alder cycloaddition of 4-(2-Furyl)-3-buten-2-one (4-FB) with ethylene followed by dehydration in presence of zeolites was studied. Sn grafted Beta zeolite exhibited high performance with 69% yield of 2-AcTNAPH starting from 4-FB. In this reaction, 6-AcBZOF was produced as intermediate. Further, it was found that this acetyl substituted tetrahydrobenzofuran could be formed in high yield, 86%, in the absence of catalyst. For the first time in the literature, we report the synthesis of a renewable acetyl-substituted tetrahydronaphthalene in high yield from biomass-derived 4-FB in a tandem approach. While a acetyl-substituted tetrahydrobenzofuran could be prepared without a catalyst, catalyst was essential for the successful synthesis of the acetyl-substituted tetrahydronaphthalene