Polyynes to Polycycles: Domino Reactions Forming Polyfused Chalcogenophenes.

Polyfused chalcogenophenes are prepared in one step through polyelectrophilic cyclization of polyynes using the ambiphilic reagent MeACl (A = S, Se, or Te). Up to four new rings have been generated under mild conditions, including thiophenes, selenophenes, and tellurophenes.

Formation of Highly Substituted Indenes through Acid Promoted Cyclodehydration with Nucleophile Incorporation.

Readily accessible 3-aryl-2-carboxypropenones (by Knoevenagel condensation) undergo acid promoted cyclodehydration with nucleophile incorporation to form highly substituted indenes. For stronger nucleophiles, nucleophile incorporation precedes cyclodehydration in a nucleophilic-addition-cyclodehydration (NAC) sequence. For weaker nucleophiles, cyclodehydration precedes nucleophile incorporation in a cyclodehydrative-nucleophilic-trapping (CNT) sequence, involving a reactive allyl cation intermediate.