An efficient and expeditious synthesis of novel 2,2-dialkyl-2,3-dihydrobenzofurans from phenols and 2,2-dialkylacetaldehydes

Reactions of 2,2-dialkylaldehydes with electron-rich 2-naphthols and para-substituted phenols in presence of catalytic amount of -TSA under closed vessel solvent-free microwave irradiation conditions resulted in formation of corresponding 2,2-dialkyl-1,2-dihydronaphtho[2,1-]furans and 2,2-dialkyl-2,3-dihydrobenzofurans, respectively, in good to excellent yields. The effect of stoichiometry, temperature, and catalyst in reaction progress was systematically investigated. 14-Alkyl--dibenzo[]xanthenes was obtained as minor products when 2-naphthol and 6-bromo-2-naphthols were used as starting phenols. Simple phenols gave a lower yield of the 2,2-dialkyl-2,3-dihydrobenzofurans products than their electron-rich naphthalene counterparts. Also, xanthene-type products were not detected in case of simple phenols by GC-MS or column chromatography.