Synthesis and Some Chemical Transformations of Unsaturated Ketones of the Dihydropyran Series

Methods have been developed for the synthesis of unsaturated ketones of the dihydropyran series via aldolization-crotonization of 3,4-dihydro-2H-pyran-2-carbaldehyde with some unsaturated ketones. Among the proposed methods, the optimal were reactions carried out in 20% alcoholic sodium hydroxide at room temperature, which ensured higher selectivity, high yield (85-95%) of the target products, and minimization of side processes. The obtained unsaturated ketones were subjected to various chemical transformations involving the side-chain double bond, and their new derivatives were synthesized. In particular, the oxidation of unsaturated ketones with 28% hydrogen peroxide gave the corresponding epoxy ketones which reacted with secondary amines to afford amino alcohols.