I Metalli alcalini in sintesi organica: attivazione e selettività del sodio metallico in reazioni di metallazione riduttiva

This work mainly report the results obtained in the application of a new methodology , in organic synthesis, mediated by alkali metals, especially sodium metal. The reaction of 1,2-diarylethenes with Na metal in dry THF allows the generation of a wide array of 1,2-diaryl-1,2-disodioethanes, and we showed that these vic-diorganometallics are very effective reductive elimination reagents, useful in several applications. We investigated the reductive dehalogenation of several vicdisubstituted compounds, and halogenated aromatic compounds. Our procedure is tolerant of several functional groups, and shows promising applications as a new and selective protocol to be employed in the reductive removal of protecting groups. We can say that 1,2-diaryl-1,2- disodioethanes can be considered as synthetic equivalents of an activated, selective, and highly reactive form of Na metal, functioning under homogeneous reaction conditions. Finally, following our interest in the generation of polar organometallic reagents by the reductive cleavage of aromatic and benzylic ethers as well as the employment of the resulting carbanions in the synthesis of biologically active compounds, we investigated the effect of different alkali metals, namely Na and Li, on the reductive metalation of 3,4,5-trimethoxybenzyl methyl ether, Indeed, this ether can be considered as a cheap starting material allowing either the synthesis of 2,5-dialkylresorcinols, a class of naturally occurring compounds endowed with cytotoxic and antibiotic activities, or of 1,2,3- trimethoxyarenes, a class of compounds endowed, inter alia, with interesting anticancer properties.