Base-Catalyzed Intramolecular Cycloaddition of Dialkyl(4-hydroxybut-2-yn-1-yl)[3-(4-bromophenyl)prop-2-yn-1-yl]ammonuim Chlorides and Recyclization of the Products

Abstract

Dialkyl(4-hydroxybut-2-yn-1-yl)[3-(4-bromophenyl)prop-2-yn-1-yl]ammonium chlorides in the presence of 2 equiv of potassium hydroxide at room temperature underwent exothermic intramolecular cycloaddition, followed by recyclization, to give 8-bromo-4-(dialkylaminomethyl)-1,3-dihydronaphtho[1,2-c]furans. Like other 4-hydroxybut-2-yn-1-yl analogs, intramolecular cycloaddition of piperidinium and morpholinium salts occurred with heat evolution in the presence of 0.2 mol of 3 N KOH after preliminary heating at 45–50°C for 10–15 min. Under these conditions, partial recyclization of the cyclization products was observed (by 10–13%). Intramolecular recyclization of 6-bromo-4-(hydroxymethyl)-1,3-dihydrospiro[benzo[f]isoindole-2,1′-piperidin]-2-ium chloride and 6-bromo-4-(hydroxymethyl)-1,3-dihydrospiro[benzo[f]isoindole-2,4′-morpholin]-2-ium chloride by the action of 2 equiv of KOH at room temperature in 10–15 min afforded 4-(aminomethyl)-8-bromo-1,3-dihydronaphtho[1,2-c]furans.