ChemInform Abstract: Three Types of Products Obtained Unexpectedly from the Reaction of Dimedone with Chalcones.

Abstract

The apparently simple Michael reaction of dimedone with chalcones afforded three types of products. The reaction of dimedone with chalcones in water at reflux, mediated by cetyltrimethylammonium bromide, gave the expected Michael adducts in good to excellent yields after purification by column chromatography. The attempted purification of the Michael adducts by recrystallization from ethanol in air unexpectedly generated hydroperoxidated and hydroxylated Michael adducts in low yields. The efficient synthesis of hydroperoxidated Michael adducts could be achieved in nearly quantitative yields by autoxidation of the Michael adducts in 1,2-dichloroethane at room temperature under aerobic conditions. The conversion of the hydroperoxidated Michael adducts to hydroxylated Michael adducts was facilitated by reduction with triphenylphosphane in excellent yields. Some of the reported Michael adducts in the literature need to be reassigned. Particular caution must be exerted to assign the Michael products generated from cyclic β-diketones, such as dimedone, because different purification processes may give different types of products.