Process for preparing 2,5-dialkyl-4-hydroxy-3(2H)-furanones and 4-alkenyl-dihydro-3(2H) furanones obtained as intermediate products.

摘要

Preparation of 2,5-dialkyl-4-hydroxy-3(2H)-furanones of the formula <CHEM> wherein R and R min are alkyl with 1-3 carbon atoms. An aldol condensation of a 2,5-dialkyl-dihydro-3(2H)-furanone with an aldehyde R sec CHO is carried out in a basic medium, followed by a dehydration of the resulting aldol to the corresponding exocyclic alkene: <CHEM> and a subsequent oxonization in the presence of a participating solvent, to obtain the corresponding hydroperoxyhemiacetal; the latter is reduced to the corresponding acetal, which is converted to the desired product by heating under reflux in an acid medium and in an inert atmosphere. The furanones thus obtained may be used as flavouring substances.