Preliminary communication

Enantioselective Protonation of Ketene Bis(trimethylsilyl) Acetals Derived from α-Aryl-α-haloacetic Acids Using LBA

Kazuaki Ishihara ; Graduate School of Engineering, Nagoya University, Furo-cho, Chikusa, Nagoya 464-01, Japan
Shingo Nakamura ; Graduate School of Engineering, Nagoya University, Furo-cho, Chikusa, Nagoya 464-01, Japan
Hisashi Yamamoto ; Graduate School of Engineering, Nagoya University, Furo-cho, Chikusa, Nagoya 464-01, Japan

Abstract

Optically active α-halocarboxylic acids and derivatives are important and versatile building blocks in organic synthesis. Lewis acid assisted chiral Brönsted acid (LBA) was recently prepared in situ from tin(IV) tetrachloride and optically pure binaphthol and shown to be an effective reagent for enantioselective protonation of pro- chiral silyl enol ethers and ketene bis(trialkylsilyl) acetals. In this paper we describe highly enantioselective protonation of ketene bis(trimethylsilyl) acetals prepared from α-aryl-α-haloaeetic acids using LBA. This is a new methodology for the enantioselective synthesis of α-aryl-α-haloacetic acid derivatives, and the commercially available chiral binaphthol can be recovered efficiently for reuse.

Keywords

Hrčak ID:

136669

URI

https://hrcak.srce.hr/136669

Publication date:

3.6.1996.

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