Potassium tert-butoxide promoted annulation of 2-alkynylphenyl propargyl ethers: selective synthesis of benzofuran and 12H-benzoannulene derivatives.
We present here our results on potassium tert-butoxide promoted annulation reactions of 2-alkynylphenyl propargyl ethers to give two different types of heterocycles: 3-benzyl-2-alkynylbenzofurans and 12H-benzoannulenbenzo[b]furans. A series of functionalized 2-alkynylphenyl propargyl ethers were efficiently cyclized by potassium tert-butoxide to the corresponding products. The optimized reaction conditions tolerated a large variety of functional groups, including electron-rich, electron-poor, and N-heterocyclic substrates. Selective product formation was obtained by controlling the solvent and temperature. When THF was used at room temperature, 3-benzyl-2-alkynylbenzofuran derivatives were exclusively obtained, while the use of DMF at 60 °C gave selectively 12H-benzoannulen[b]benzofurans.
Laboratório de Síntese, Reatividade, Avaliação Farmacológica e Toxicológica de Organocalcogênios and ‡Laboratório de Materiais Inorgânicos, CCNE, UFSM , Santa Maria, Rio Grande do Sul, Brazil 97105-900.
Tamiris B
TB
Grimaldi
Davi F
DF
Back
Gilson
G
Zeni