Silver-Catalyzed 1,3-Acyloxy Migration/Diels–Alder Reaction of 1,9-Dien-4-yne Esters to Partially Hydrogenated Isoquinolines

A synthetic method to prepare partially
hydrogenated isoquinolines
efficiently from silver-mediated [3,3]-sigmatropic rearrangement/Diels–Alder
reaction of 1,9-dien-4-yne esters is described. The reactions were
shown to be robust with a wide variety of substitution patterns tolerated
to provide the corresponding nitrogen-containing heterocyclic products
in good to excellent yields. This includes examples containing a bridgehead
sp3 quaternary carbon center as well as the cycloisomerization
of one substrate to give the corresponding bicyclic adduct in excellent
yield at the gram scale.