Binaphthyl‐Modified Quaternary Phosphonium Salts as Chiral Phase‐Transfer Catalysts: Asymmetric Amination of β‐Keto Esters

Abstract

A reliable phosphonium-based PTC: For the first time a chiral quaternary tetraalkylphosphonium salt has successfully been used as a phase-transfer catalyst (PTC) for asymmetric amination of β-keto esters, in high yield and with high ee (see scheme). Asymmetric amination of a cyclic five-membered β-keto ester is a valuable method for preparing a key intermediate for asymmetric synthesis of aldose reductase inhibitor AS-3201 (Ranirestat). Detailed facts of importance to specialist readers are published as ”Supporting Information”. Such documents are peer-reviewed, but not copy-edited or typeset. They are made available as submitted by the authors. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.