Lewis Acid Catalyzed Diels-Alder Reactions of (E)-1-Methyl-2-styrylquinolin-4(1H)-ones with ortho-Benzoquinodimethane: Synthesis of New 2-(3-Arylnaphthalen-2-yl)-1-methylquinolin-4(1H)-ones

Lewis acid catalyzed cycloaddition reactions of (E)-1-methyl-2-styrylquinolin-4(1H)-ones with the very reactive diene ortho-benzoquinodimethane, generated in situ by thermal extrusion of sulfur dioxide from 1,3-dihydrobenzo[c]thiophene 2,2-dioxide, afforded trans-2-(3-aryl-1,2,3,4-tetrahydronaphthalen-2-yl)-1-methylquinolin-4(1H)ones in good yields. Upon DDQ-mediated dehydrogenation these adducts were converted into the corresponding 2-(3-arylnaphthalen-2yl)-1-methylquinolin-4(1H)-ones. The influence of electron-withdrawing and electron-donating groups on the cycloaddition and dehydrogenation reactions was investigated.