Reevaluating ortho-Carborane Synthesis: Success with Mono-Substituted Acetylenes in the Presence of Silver Salts

Abstract

The study shows that traditional methods for synthesizing ortho-carboranes from nido-B10H14 and its complexes (B10H12L2) using donor- and acceptor-disubstituted acetylenes yielding low efficiencies (yields 0 - 12%). Attempts to improve yields with ionic liquids and silver salts as catalysts were unsuccessful with disubstituted acetylenes. However, it has been found that the use of mono-substituted acetylenes (phenylacetylene, ethyl propiolate) in the presence of silver salts in the reaction with B10H12L2 substrates produces ortho-carboranes in high yields (~90%). This suggests that the key step is the formation and subsequent addition of silver acetylenides, and not the donor-acceptor π-complexes previously assumed. This finding allows us to better understand the mechanisms of the ortho-carboranes formation and offers an efficient pathway for their synthesis.

Keywords

• ortho-carborane
• decaborane
• acetylenes
• silver
• synthesis