Studies on Seven-membered Ring Compounds. XXXVI. Synthesis of Azulene Derivatives by Ring Closure of β-Cycloheptatrienyl-substituted Carbonyl Compounds

Abstract

Treatment of 2-phenyl-3-(2, 4, 6-cycloheptatrien-1-yl) propionaldehyde ethylene acetal (III) with stannic chloride in benzene followed by dehydrogenation with sulfur afforded 2-phenylazulene (V) and 1-(2-hydroxyethyloxy)-2-phenylazulene (VI). Benz[a]azulene (XV) was obtained along with anthracene (XVI) when 2-(2, 4, 6-cycloheptatrien-1-yl)-benzaldehyde (XII) or its ethylene acetal (XI) was treated with stannic chloride in benzene or with hydrogen bromide in acetic acid.