Preparation of α-hydroxy ketones via carbene-catalyzed umpolung reaction of aldehydes

摘要

The present invention relates to the preparation of α-hydroxy ketones of the general formula I. In particular, the invention relates to novel imidazolinium carboxylate adducts and to a novel process for using catalytic amounts of imidazolium and imidazolinium carboxylate adducts in the acyloin reaction of aldehydes to prepare hydroxy ketones of the general formula I,; where R and R′ are the same or different and are each H or a straight-chain or branched and optionally substituted C₁-C₁₂-alkyl radical, and R″═H₃CSCH₂CH₂, t-butyl, n-butyl, sec-butyl, n-propyl, i-propyl, an optionally heteroatom-substituted C₆-C₁₈-aryl, heteroaryl, C₆-C₁₈-arylalkyl, especially phenylmethyl, where phenyl may again be heteroatom-substituted, or heteroalkyl.