The zinc chloride catalyzed condensation of mesityl oxide with ethyl acetoacetate resulted in the formation of two structural isomers: 3, 5, 5-trimethyl-2-cyclohexen-l-one-4-carboxylic acid ethyl ester (4) and 3, 5, 5-trimethyl-2-cyclohexen-1-one-6-carboxylic acid ethyl ester (5). Isomer 5 was readily converted into isophorone by selective hydrolysis, The syntheses of two substituted p-ionones, 3-ethylenedioxy-p-ionone (17) and 3-ethoxy-3, 4-dehydro-p- ...
