We developed a novel method for synthesizing 2‐(4‐hydroxyaryl)‐3,4‐fused tricyclic dihydrobenzopyrans with 2,3‐syn and 3,4‐syn motif based on the acid‐promoted cascade cyclization via vinylidene para‐quinone methide intermediates. Using easily prepared linear substrates, TFA‐promoted cascade cyclization proceeded in the presence of triethylsilane, affording a series of five to seven‐membered ring‐fused dihydrobenzopyran derivatives in moderate to excellent yield in a highly diastereoselective manner. The developed method provided new access to potent and selective ERβ agonists.
We developed an enantioselective
synthetic method of
constructing
a seven-membered ring-fused indole skeleton with contiguous stereocenters
for the synthesis of dragmacidin E. Introduction of chirality at the
benzylic position was achieved by Ir-catalyzed asymmetric hydrogenation.
After construction of the tricyclic molecular framework using Pd-catalyzed
cascade cyclization, the tetrasubstituted carbon center was created
using the Ag nitrene-mediated C–H amination reaction. The developed
method provided access to the functionalized seven-membered ring-fused
indole skeleton with a hydroxymethyl branch in the tetrasubstituted
carbon.
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