Synthesis and Phytotoxic Activity of New Pyridones Derived from 4-Hydroxy-6-Methylpyridin-2(1H)-one

Commercial dehydroacetic acid was converted into 4-hydroxy-6-methylpyridin-2(1H)-one (3), which was then condensed with several aliphatic aldehydes to produce seven new title compounds in variable yields (35–92%). Reaction of 3 with α,β-unsaturated aldehydes resulted in the formation of condensed pyran derivatives 4g’ and 4h’. A mechanism is proposed to explain the formation of such compounds. The effects of all methylpyridin-2(1H)-one derivatives on the development of the dicotyledonous species Ipomoea grandifolia and Cucumis sativus and the monocotyledonous species Sorghum bicolor were evaluated. At the dose of 6.7 × 10(-8) mol a.i./g substrate the compounds showed some phytotoxic selectivity, being more active against the dicotyledonous species. These compounds can be used as lead structures for the development of more active phytotoxic products.