Palladium-catalysed enantioselective diacetoxylation of terminal alkenes

Optically pure 1,2-diols are one of the most privileged structural motifs. They are not only frequently found in natural products and drugs, but are also regarded as very useful synthons in organic synthesis. Asymmetric dioxygenation of alkenes could potentially provide a highly efficient and straightforward method for the synthesis of enantioenriched 1,2-diols. Although enantioselective dioxygenations on different alkenes have been studied widely, those on terminal alkenes remain elusive. Herein, we report a Pd(ii)-catalysed enantioselective diacetoxylation of terminal alkenes, including challenging substrates such as 1-propene and 1-butene. Notably, ligand engineering of the simple pyridinyl oxazoline ligand is essential for substantially increasing the catalytic reactivity of Pd(OAc)2. The method exhibits an exquisite selectivity for terminal alkenes, allowing precise asymmetric diacetoxylation reactions from feedstock alkenes to complex molecules bearing multiple alkenic moieties, which provides rapid and efficient access to various synthetically useful chiral 1,2-diols. Asymmetric dioxygenation of alkenes is an attractive concept to synthesize enantioenriched diols, but the performance in the case of terminal alkenes is low with current methods. Now, this has been addressed by an asymmetric oxypalladation process that provides access to enantioenriched 1,2-diols, enabled by the chiral 6-modified pyridinyl oxazoline ligand.