Regioselective Synthesis of 2H-Benzopyrano[3,2-c]quinolin-7(8H)-ones by Radical­ Cyclization

Abstract

Different 4-hydroxyquinolin-2(1H)-ones were treated with 2-bromobenzyl bromide and 2-bromo-5-methoxybenzyl bromide in the presence of anhydrous potassium carbonate in acetone to afford a number of 4-(2′-bromobenzyloxy)quinolin-2(1H)-one derivatives in 80-85% yield. These 4-(2′-bromobenzyloxy)quinolin-2-(1H)-ones were then refluxed with tributyltin chloride and sodium cyanoborohydride in benzene under nitrogen, in the presence of a catalytic amount of AIBN, for 4-5 hours to give 2H-benzopyrano[3,2-c]quinolin-7(8H)-ones in 70-80% yields.

2-bromobenzyl bromide - sodium cyanoborohydride - radical cyclization - tributyltin chloride - 2H-benzopyrano[3,2-c]quinolin-7(8H)-ones

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