Halogen–lithium exchange versus deprotonation: regioselective mono- and dilithiation of aryl benzyl sulfides. A simple approach to α,2-dilithiotoluene equivalents

✍ Scribed by Tomasz Kliś; Janusz Serwatowski; Grzegorz Wesela-Bauman; Magdalena Zadrożna

• Book ID: 104097399
• Publisher: Elsevier Science
• Year: 2010
• Tongue: French
• Weight: 900 KB
• Volume: 51
• Category: Article
• ISSN: 0040-4039
• DOI: 10.1016/j.tetlet.2010.01.074

✦ Synopsis

Halogen-lithium exchange and deprotonation reactions between aryl benzyl sulfides and alkyllithiums were investigated. The resultant mono-and dilithiated intermediates were converted into the corresponding aldehydes and boronic, or carboxylic acids in good yields. It was found that diethyl ether stabilizes the ortho-lithiated compounds toward isomerisation to the benzylic derivatives. The process occurs easily in THF at low temperature and is a facile route to the a,2-dilithiotoluene derivative which can be transformed into a dicarboxylic acid on treatment with CO 2 .