4- Bromo-5- furanones, preparation

A rapid synthesis of carbon-14 labeled [l-14C]levulinic acid from simple building blocks has been demonstrated by Johansen and coworkers (Scheme 6.172) [324], In all three of the synthetic steps, starting from bromo[l-14C]acetic acid, microwave heating was used to accelerate the reactions, allowing a total preparation time of less than 1 h. The labeled levulinic acid was subsequently transformed into (5Z)-4-bromo-5-(bromomethylene)-2(5H)-furanone in a bromination/oxidation sequence (not shown), a potent quorum sensing inhibitor. 

Padwa and Dehm62 have prepared furanones (36) by reaction of carbox-ylates with bromo aldehydes, catalyzed by 18-crown-6. The first step of the reaction is also an esterification of the potassium phenylacetate the next step is equivalent to an intermolecular addition of a carbanion to an aldehyde, followed by elimination. 

Hoffinann HMR, Schmidt B, Wolff S (1989) Preparation of 5-Bromotetronates [4-Alkoxy-5-bromo-2(5/7)-furanones] and a New Concept for the Synthesis of Aflatoxins and Related Structure Types. Tributyltin Hydride versus Palladium-Promoted Intramolecular Hydroarylation. 

Likewise a-keto and a-aldehydo esters have been prepared by the reaction of potassium phenylacetate with a-bromo ketones or aldehydes by an 18-crown-6 catalyzed displacement reaction in acetonitrile or benzene solution. These compounds could be isolated after short reaction times, or they could be converted on continued heating to 2(5H)furanones, the product of intramolecular aldol condensation and... 

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