Sc(OTf)3-catalyzed diastereoselective [4 + 2] cycloaddition reaction of 3-benzylideneindoline-2-thiones with alkylidene malonates

Update on thiopyran-fused heterocycle synthesis (2013–2024)

“…In this reaction, 99 and 100 underwent reaction in dichloromethane at room temperature in the presence of 20 mol% Sc(OTf) 3 , yielding product 101 (Scheme 17). 36…”

In(OTf)3-catalyzed formal (4 + 3) cycloaddition reactions of 3-benzylideneindoline-2-thiones with 2-indolylmethanols

“…16 Furthermore, the monomeric 3-benzylideneindoline-2-thione represents a rare sulfur-containing 4π building block for the synthesis of indole-based privileged scaffolds. 17 In 2023, our group achieved the first formal (4 + 3) cycloaddition reaction with donor–acceptor cyclopropanes to generate thiepino[2,3- b ]indoles (Scheme 1(e)). 18 However, 3-benzylideneindoline-2-thiones exhibited strong inherent self-dimerization and existed in the form of dimers.…”