Functionalization of Csp3–H bond—Sc(OTf)3-catalyzed domino 1,5-hydride shift/cyclization/Friedel–Crafts acylation reaction of benzylidene Meldrum’s acids

Under Sc(OTf)3 catalysis, benzylidene Meldrum’s acids bearing a tethered p-methoxyphenethyl group were observed to undergo a [1,5]-hydride shift/cyclization at room temperature, representing a mild Csp3–H bond functionalization. The resulting spiro Meldrum’s acid intermediates then underwent intramolecular Friedel–Crafts acylation, completing the one-pot, domino reaction. The reported protocol generates the 6-6-5-6 tetracyclic core of tetrahydrobenzo[b]fluoren-11-ones.