α-Diketones as acyl anion equivalents: A non-enzymatic thiamine-promoted route to aldehyde-ketone coupling in PEG400 as recyclable medium

Article abstract of DOI:10.1016/j.tet.2011.08.056

By mimicking the peculiar behavior of thiamine diphosphate-dependent acetylacetoin synthase, it has been demonstrated that thiamine hydrochloride 2a and its simple analogue thiazolium salt 2b are able to activate α-diketones as acyl anion equivalents in nucleophilic acylations, such as the homo-coupling of α-diketones and the hitherto unreported cross-coupling between α-diketones and α-ketoesters. These carboligation reactions were optimized under stoichiometric (2a) and catalytic conditions (2b) by using eco-friendly PEG₄₀₀ as the reaction medium, thus allowing both solvent and thiazolium salt recycling.