Chemoselective Acylation/Wittig or β-Acylation Reactions: Diversity-Oriented Synthesis of Indandione-Tethered Benzofurans and β-Acylated Arylidene Indandiones

An efficient, chemoselective, and switchable diversity-oriented synthesis of β-acylated arylidene indandiones and the indanedione-based formal cross-coupling benzofuran adducts is reported, which is challenging to realize by conventional strategies. It is achieved via a chemoselective acylation by altering the addition sequence of acylating agents with distinct reactivities, followed by β-acylation or chemoselective intramolecular Wittig reactions, with the in situ-generated bis-acylated phosphorus ylides as the key intermediates.