Open-face alkylation of the 8-R-nido-7,8,9-C3B8H11 tricarbollides

• General method for the alkylation of 8-R-nido-7,8,9-C3B8H11 tricarbaboranes.
• Alkylation of the open-face boron positions in the cage.
• Syntheses of tricarbollide derivatives.
• Boron-substitution methods.
• Mechanistic aspects of alkylation reactions.

Sequential methylation of the 8-R-nido-7,8,9-C3B8H11 tricarbollides (R = Ph, p-tol and 2-naphthyl (2-naph)) in the presence of NaH in THF proceeds on the open-face B(10,11) positions to generate mono and dimethyl derivatives, 8-R-nido-7,8,9-C3B8H10-10-Me and 8-R-nido-7,8,9-C3B8H9-10,11-Me2. To demonstrate the general character of the alkylation procedure, B-dialkyl derivatives 8-Ph-nido-7,8,9-C3B8H9-10,11-R12 (R1 = C3H5 (All) and CH2Ph) were prepared via analogous alkylation of 8-Ph-nido-7,8,9-C3B8H11 with allyl and benzyl bromides. The structures were substantiated by multinuclear (11B, 1H and 13C) NMR spectroscopy and that of 8-Ph-nido-7,8,9-C3B8H9-10,11-Me2 was determined by an X-ray diffraction analysis.

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