An iridium-catalyzed stereoselective coupling of allylic
ethers
and alkynes to generate 3,4-substituted 1,5-enynes is reported. Under
optimized conditions, the coupling products are formed with excellent
regio-, diastereo-, and enantioselectivities, and the protocol is
functional group tolerant. Moreover, we report conditions that allow
the reaction to proceed with complete reversal of diastereoselectivity.
Mechanistic studies are consistent with an unprecedented dual role
for the iridium catalyst, enabling the propargylic deprotonation of
the alkyne through π-coordination, as well as the generation
of a π-allyl species from the allylic ether starting material.
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