Enantioselective and Diastereodivergent Allylation of Propargylic C-H Bonds

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 pi-coordination, as well as the generation of a pi-allyl species from the allylic ether starting material.

Automated summary

An iridium-catalyzed stereoselective coupling reaction has been developed for the synthesis of 3,4-substituted 1,5-enynes. The reaction shows excellent regio-, diastereo- and enantioselectivities under optimized conditions, and is tolerant to various functional groups. Mechanistic studies revealed the unprecedented dual role of the iridium catalyst, enabling propargylic deprotonation of the alkyne through pi-coordination and generation of a pi-allyl species from the allylic ether starting material.