CONVENIENT SYNTHESIS OF 5-ALKYLIDENE-2(5H)-FURANONES, 2(5H)-FURANONES AND 2-ETHOXYFURANS

Article abstract of DOI:10.1016/S0040-4020(01)86013-0

Starting from enolizing 1,2-diketones 5 and (2,2-diethoxyvinylidene)triphenylphosphorane (2) or from 5 and (2,2-diethoxyvinyl)triphenylphosphonium tetrafluoroborate (6) the orthoesters 9 are prepared. 9 can be hydrolyzed under acidic conditions to give 5-alkylidene-2(5H)-furanones 10.Reaction of 1,2-hydroxyketones 11 and (2,2-ditehoxyvinylidene)triphenylphosphorane (2) via Michael addition and Wittig reaction yields orthoesters 15, which can be hydrolyzed to give 2(5H)-furanones 16 and 2-ethoxyfurans 17 respectively.A considerable variation of the substitens (R⁴)can be achieved starting from 11 and (2,2-diethoxyvinyl)triphenylphosphonium tetrafluoroborates 12.