Cobalt-Catalyzed Asymmetric 1,4-Reduction of β,β-Dialkyl α,β-Unsaturated Esters with PMHS

A cobalt-catalyzed asymmetric reduction of beta,beta-dialkyl alpha,beta-unsaturated esters with polymethylhydrosiloxane (PMHS) was reported to deliver the corresponding esters containing a chiral trialkyl carbon center at beta-position with up to 97 % yield and 98 % ee. The chiral tridentate ligand oxazoline iminopyridine (OIP) could perform well for the asymmetric reduction instead of chiral bidentate ligands. This operationally simple protocol shows a broad scope of substrates using one equivalent of readily available PMHS as a cheap and easy-to-handle reductive reagent.

Automated summary

A cobalt-catalyzed asymmetric reduction of β,β-dialkyl α,β-unsaturated esters using PMHS as a reductive reagent was reported, delivering esters with a chiral trialkyl carbon center at the β-position with high yield and high enantioselectivity. The chiral tridentate ligand OIP showed excellent performance in the asymmetric reduction, replacing the need for chiral bidentate ligands. This simple protocol utilizes readily available PMHS as a cost-effective and easy-to-handle reductive reagent for a wide range of substrates.