Regioselective coupling reaction of azulene with α,β-unsaturated ketones by Mg-promoted reduction

Mg-Promoted reductive coupling of azulene with various α,β-unsaturated ketones in the presence of chlorotrimethylsilane in 1-methyl-2-pyrrolidinone brought about regioselective formation of the corresponding 6-substituted dihydroazulenes, which were easily oxidized to the corresponding 6-substituted azulenes by 2,3-dichloro-5,6-dicyano-1,4-benzoquinone in good yields. This new regioselective method enabled us to synthesize various 6-substituted azulenes from azulene in only two steps.