Diastereoselective Three‐Step Route to o‐(6‐Nitrocyclohex‐3‐en‐1‐yl)phenol and Tetrahydro‐6H‐benzo[c]chromen‐6‐ol Derivatives from Salicylaldehydes

Abstract

AbstractThis work was aimed at preparing o‐(6′‐nitrocyclohex‐3′‐en‐1′‐yl)phenol and tetrahydro‐6H‐benzo[c]chromen‐6‐ol derivatives in three steps starting from salicylaldehydes. Initially 3‐acetylcoumarins were prepared in the absence of solvent using a solid base catalyst such as PS‐TBD. In the second step, the Diels–Alder reactions of 3‐nitrocoumarins and 3‐acetylcoumarins under thermal conditions or in the presence of hafnium chloride yielded the corresponding tetrahydrobenzo[c]chromenones. The final part of the work was dedicated to the transformation of nitro‐tetrahydrobenzo[c]chromenones into o‐(6′‐nitrocyclohex‐3′‐en‐1′‐yl)phenol derivatives in aqueous medium and to the conversion of acetyl tetrahydrobenzo[c]chromenones into the corresponding tetrahydro‐6H‐benzo[c]chromen‐6‐ol derivatives in tetrahydrofuran (THF), in the presence of tetrabutylammonium fluoride (TBAF) on silica. In every case the diastereoselectivity was complete and the reaction yields were high.