Synthesis and structure of acetyl-substituted oxocyclohexanecarboxylates

Abstract

Dicarbonyl-substituted hydroxycyclohexanones with similar substituents (Ac or COOR) have been studied in sufficient detail [1]. Much less data are available on analogous compounds having different substituent groups (COR and COOR) [2]. However, such derivatives are promising from the viewpoint of their biological activity and design of carboand heterocyclic systems with specified functionalization pattern. We now report on the synthesis of new ethyl 3-acetyl-2-aryl-4-hydroxy-4-methyl-6-oxocyclohexanecarboxylates Ia–Ic whose structure was determined by spectral methods and chemical transformations. Compounds Ia–Ic were synthesized by condensation of aromatic aldehydes with ethyl acetoacetate or acetylacetone to give ethyl 2-benzylidene-3-oxobutanoate (IIa) or 3-arylmethylidenepentane-2,4-diones IIb and IIc, followed by Michael addition. Intramolecular aldolization of intermediate A gave cyclohexanecarboxylates Ia–Ic in up to 80% yield. The spectral data (IR and H NMR) for the synthesized compounds confirmed only the presence of carbonyl-containing fragments but not their position, so