Reinvestigation of the sulfuric acid-catalysed cyclisation of brominated 2-alkyllevulinic acids to 3-alkyl-5-methylene-2(5H)-furanones

Add time:07/16/2019    Source:sciencedirect.com

A synthesis of ethyl-, butyl-, hexyl- and dodecyl-substituted fimbrolides from alkyl-substituted levulinic acid derivatives through bromination and acid promoted lactonisation is described. The underlying reactions have been investigated using levulinic acid as a model, and the effects of varying the bromination conditions and changing acid concentration on product distribution are discussed. Dibromination proceeds best in CHCl3 and proceeds in EtOH-free CHCl3 without the complication of ester formation. Cyclisation occurs with concomitant oxidation in 98–100% H2SO4 but gives highest yields of fimbrolides in 100% H2SO4. The formation of related beckerelide substances is also described.

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