Brellochs reaction

In organoboron chemistry, the Brellochs reaction provides a way to generate the monocarboranes. The Brellochs method uses formaldehyde to insert single carbon atoms into boron hydrides.^[1]

Illustrative is the synthesis of CB₉H₁₄⁻ from commercially available decaborane.^[2]

B₁₀H₁₄ + CH₂O + 2 OH⁻ + H₂O → CB₉H₁₄⁻ + B(OH)₄⁻ + H₂

Oxidation of the arachno anion gives nido-6-CB₉H₁₂⁻. Base degradation of the latter gives arachno-4-CB₈H₁₄.