Collect. Czech. Chem. Commun. 2001, 66, 1499-1507

Cyanoethylation and (Methoxycarbonyl)ethylation of Icosahedral ortho-Carborane Derivatives at Carbon Vertices via Michael Additions

Jaromír Plešek*, Jaroslav Bačkovský, Jiří Fusek and Zbyněk Plzák

Institute of Inorganic Chemistry, Academy of Sciences of the Czech Republic, 250 68 Řež near Prague, Czech Republic


The C-H vertices of ortho-carborane and its derivatives can be smoothly cyanoethylated with acrylonitrile in the presence of benzyl(triethyl)ammonium hydroxide in a two-phase system: dichloromethane/water or 1,2-dimethoxyethane/water. The reaction is highly specific and not transferable to its meta and para isomers. No Michael addition with methyl acrylate takes place under these conditions. However, with NaH as catalyst (methoxycarbonyl)ethylation can be accomplished with ortho-carborane; meta and para isomers react neither with acrylonitrile, nor with methyl acrylate even under such forcing conditions. The syntheses, properties and constitutions of 1-(2-cyanoethyl)-ortho-carborane, 1-(2-cyanoethyl)-2-phenyl-ortho-carborane, 1,2-bis(2-cyanoethyl)-ortho-carborane, 1-[2-(methoxycarbonyl)ethyl]-ortho-carborane and 1,2-bis[2-(methoxycarbonyl)ethyl]-ortho-carborane, along with their respective acids, are described. Melting points, TLC, "heated-inlet" mass spectrometry, and the 1H and 11B NMR spectra of all compounds, are presented. The scope of cyanoethylations and (methoxycarbonyl)ethylations of other deltahedral carbaboranes and heteroboranes is considered.

Keywords: Boranes; Carboranes; Michael additions; Phase-transfer catalysis; Cyanoethylation; (Methoxycarbonyl)ethylation; 1H and 11B NMR spectroscopy; Heated-inlet mass spectrometry.

References: 12 live references.