Stepwise trimethylsilyl and trimethylgermyl substitutions at tetraborylmethane.

Abstract In 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) 2 CB(pg) 2 and (TMG) 2 CB(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 abstract Diboryldisilyl- 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. Image 1 Highlights • Diboryldisilyl- 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. [ABSTRACT FROM AUTHOR]