(Z)-Jasmone, dihydrojasmone and other 3-methylcyclo= pent-2-en-1-ones are easily synthesized starting from aldehydes and 1-(2-methyl-1, 3-dioxolane-2-yl)-2-nitroethane as reagent for 3-ketobutyl anion synthon. Nitro-aldol condensation is the chainlegthening reaction followed by oxidation and denitration via p-toluenesulfonylhydrazones of the corresponding α-nitroke= tones. Removal of protecting groups gives 1, 4-diketones which ...