Stepwise trimethylsilyl and trimethylgermyl substitutions at tetraborylmethane

Publication date: Available online 2 August 2018Source: Journal of Organometallic ChemistryAuthor(s): Zachary J. Baum, Jingtao Zhang, Rick A.L. Morasse, Joshua E. GoldbergerAbstractIn exploring the suitability of tetraborylmethane precursors as C4− synthons, we have studied the limits of stepwise trimethylsilyl and trimethylgermyl substitutions on tetrakis (1,3-propanediolatoboryl)methane. In contrast to previous reports indicating minimal silylation of tetraborylmethanes, we have shown that organolithium-mediated deborylation-metalation methodologies readily proceed for up to two substitutions. This enables the synthesis of new borylmethane derivatives including (TMS)2CB(pg)2 and (TMG)2CB(pg)2 (pg = 1,3-propanediolate, TMS = trimethylsilyl, TMG = trimethylgermyl). While further base-activated deborylation attempts lead to protodeboronation, limited reactivity, or de-esterification of the boronate ester, increasing the degree of substitution imparts air- and water-stability to the boronate esters.Graphical abstractDiboryldisilyl- and diboryldigermyl- methanes were synthesized via stepwise deborylation-metalation of a tetraborylmethane. The new compounds were characterized by NMR spectroscopy and X-ray crystallography. The disubstituted compounds are air- and water-stable and can be readily purified by column chromatography.

Source: Journal of Organometallic Chemistry - August 2, 2018 Category: Chemistry Source Type: research