A Novel Route to Isoannulated Heteroaromatic Compounds, 1. -Synthesis and Reactions of Furofurans, Thienofurans, Furobenzofurans, and BenzothienofuransA general method for the synthesis of furo-and thienofurans 4-7 has been developed. The reaction principle is based on the thermal transformation of suitably structured epoxyhexenynes (15 -19) following the general reaction sequence 1 --+ 2 --+ 3 (annulation type A). Derivatives of the so far unknown diheteropentalenes furo [3,4-b]
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