A Versatile Synthetic Method of 1-Alkylazulenes and Azulene by the Reactions of 3-Methoxycarbonyl-2H-cyclohepta[b]furan-2-one with in situ Generated Enamines

Abstract Methyl 3-alkylazulene-1-carboxylates were synthesized in high yields by the reaction of 3-methoxycarbonyl-2H-cyclohepta[b]furan-2-one with in situ generated morpholine enamines of aldehydes. Treatment of the esters with 100% phosphoric acid gave 1-alkylazulenes in excellent yields. Azulene was also synthesized in a good yield via methyl azulene-1-carboxylate with a modification of this method.