2,5-Dimethyl-1,4-bis(carboxyalkyl)benzenes were prepared in almost quantitative yield by alkylation of malonic esters from 2,5-dimethyl-1,4-dibromomethylbenzene obtained by bromomethylation of 1,4-dimethylbenzene. The methyl groups on the central benzene ring induce intramolecular, regiospecific cycloeliminations leading selectively to the diketones, the precursors of the corresponding 1,5-dihydro-s-indacenes, which also were obtained in very high yield. These new ligand precursors were easily converted to the mono- or dianions, which were characterized by means of the mono- or disilylated compounds. Disilylation occurs in cis and trans position. The structure of the trans-1,5-bis(trimethylsilyl)-2,6-diethyl-4,8-dimethyl-s-indacene was obtained by X-ray diffraction. Hexaalkyl-1,5-dihydro-s-indacenes underwent regioselective monosilylation and regiospecific and stereoselective disilylation. Disilylation of the less hindered tetraalkyl-1,5-dihydro-s-indacenes was regioselective and stereoselective.

In the last decade, there has been increasing interest in investigating the impact of flavonoids on insects, specifically for pest control. In this study, we investigated the impact of isoflavonoids upon the feeding behavior of the clover root borer, Hylastinus obscurus Marsham (Coleoptera: Curculionidae), which is one of the most serious global pests associated with red clover, Trifolium pratense L. Four aglycones isoflavonoids: genistein (1), formononetin (2), daidzein (3) and biochanin A (4) were isolated and identified by HPLC, from roots of two Chilean red clover cultivars. The first two compounds, formononetin (2) and genistein (1), showed high feeding deterrent activity when they were evaluated in artificial diets. This antifeedant effect of isoflavones on feeding behavior of H. obscurus suggests that they are responsible for a decreasedin insect weight gain as compared with the control. This information could be useful respectively, to farmers and researcher to produce and create plants resistant to curculionid.

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