Ligand-Controlled Stereodivergent Manganese-Catalyzed Hydroalkoxylation of Alkynylnitriles to Access (E)- and (Z)-3-Alkoxyvinylnitriles.

Precise stereocontrol over functionalized alkenes remains a central challenge in organic synthesis. In particular, catalytic methods enabling flexible and stereodivergent synthesis of both trans-selective and cis-selective useful enol ethers are still underdeveloped. Herein, we report a manganese-catalyzed, ligand-controlled hydroalkoxylation of alkynylnitriles with alcohols under mild conditions. Through metal-ligand cooperation, a range of (Z)- and (E)-3-alkoxyvinylnitriles were obtained in high yields and with excellent selectivity by simply tuning the steric properties of PNP-pincer ligands: bulkier tBuPNP-Mn catalyst favored Z-selectivity, while less hindered iPrPNP-Mn catalyst led to E-selectivity. This method features a broad substrate scope, high functional group tolerance and exceptional chemo-, regio-, and stereo-selectivity. Mechanistic studies revealed that Z-products are initially formed in both cases, with the iPrPNP-Mn catalyst further promoting isomerization to the thermodynamically favored E-isomers.