Improved Synthetic Routes to Small Carboranes. Bench-Scale Preparation of Nido-2,3-C2B4H8 Derivatives from B5H9 and from B3H8(-) Salts.
Interim technical rept.,
VIRGINIA UNIV CHARLOTTESVILLE DEPT OF CHEMISTRY
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A method has been developed for producing the C,C7-dimethyl and C-phenyl derivatives of 2,3-C2B4H8 in gram quantities and in yields of 50 without the use of heat, solvent, or large-volume gas bulb reactions. This approach involves formation of a B5H9. L2 adduct L triethylamine or dimethylsulfide which reacts with 2-butyne or phenylacetylene in situ, at or below room temperature, to give the corresponding RRC2B4H6 carborane. The carborane product is easily isolated in high purity by vacuum fractionation. The most satisfactory results are obtained with triethylamine, with B5H9 maintained in excess, and with simultaneous incremental addition of the amine and alkyne to the borane. The use of dimethysulfide in place of triethylamine gives slightly higher carborane yields but results in a much slower reaction.
- Organic Chemistry