Conjugate addition of lithium ester enolates to 1-chlorovinyl p-tolyl sulfoxides:: a novel synthesis of functionalized esters and lactones having a tertiary or a quaternary carbon at the β-position

Addition of the lithium ester enolates to 1-chlorovinyl p-tolyl sulfoxides, which were synthesized from chloromethyl p-tolyl sulfoxide and ketones or aldehydes, gave esters having a tertiary or a quaternary carbon at the 3-position, and chlorine and sulfinyl groups at the 4-position in high to quantitative yields. The adducts were converted to various esters having methyl, formyl, and hydroxycarbonyl groups at the 3-position. A novel method for the synthesis of gamma-lactones, including spiro-type gamma-lactones and alpha-methylene gamma-lactones, was realized from the adducts in good overall yields. The scope and limitations of this method and the mechanism of the reactions are also discussed. (C) 2003 Elsevier Science Ltd. All rights reserved.