A new class of herbicides that are derivatives of 8-oxabicyclo[3.2.1]oct-6-en-3-one

Treatment of 8-oxabicyclo[3.2.1]oct-6-en-3-one with a catalytic amount of osmium tetraoxide and excess hydrogen peroxide resulted in the formation of the acetonide exo-6,exo-7-isopropylidenedioxy-8-oxabicyclo[3.2.1]oct-3-one (2), in 96% yield. This acetonide was converted into several aromatic alcohols (4a-k) through a Grignard reaction. The alcohols were treated with aqueous HCl in acetone, and the corresponding alkenes (5a-c,e-g,j,k) were obtained in 26-46% overall yield, from the ketone (2). The herbicidal activity of the alkenes was evaluated at a concentration of 6.6 mu g g(-1). All compounds showed an inhibitory effect (21-66%) on the Sorghum bicolor radicle growth. The inhibition of the accumulation of fresh and dried weight of the aerial parts of Cucumis sativus, after 14 days, varied from 7.1 to 60.7% and from 0.0 to 41.6%, respectively. Compounds (5a,e-g) caused 100% mortality of C. sativus, after 20 days. Compound (5g) (exo-6,exo-7-isopropylidenedioxy-3-(3-methylphenyl)-8-oxabicyclo[3.2.1]oct-2-ene) was evaluated against several weeds, and it caused 100% mortality of Desmodium tortuosum and Pennisetum setosum.