Substitution reactions at tetracoordinate boron: synthesis of N-heterocyclic carbene boranes with boron-heteroatom bonds

Andrey Solovyev; Qianli Chu; Steven J Geib; Louis Fensterbank; Max Malacria; Emmanuel Lacôte; Dennis P Curran

doi:10.1021/ja107025y

Substitution reactions at tetracoordinate boron: synthesis of N-heterocyclic carbene boranes with boron-heteroatom bonds

J Am Chem Soc. 2010 Oct 27;132(42):15072-80. doi: 10.1021/ja107025y.

Authors

Andrey Solovyev¹, Qianli Chu, Steven J Geib, Louis Fensterbank, Max Malacria, Emmanuel Lacôte, Dennis P Curran

Affiliation

¹ Department of Chemistry, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, USA.

PMID: 20886852
DOI: 10.1021/ja107025y

Abstract

Boryl halide, carboxylate and sulfonate complexes of 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene (dipp-Imd-BH(2)X, X = halide or sulfonate) have been prepared from the parent borane dipp-Imd-BH(3) by (1) substitution reactions with R-X (X = halide or sulfonate), (2) reactions with electrophiles (like I(2) or NIS), or (3) acid/base reactions with HX (provided that HX has a pK(a) of about 2 or less). Dipp-Imd-BH(2)I is most conveniently prepared by reaction with diiodine while dipp-Imd-BH(2)OTf is best prepared by reaction with triflic acid. These and other less reactive complexes behave as electrophiles and can be substituted by a wide range of heteroatom nucleophiles including halides, thiolates and other sulfur-based nucleophiles, isocyanate, azide, nitrite, and cyanide. The resulting products are remarkably stable, and many have been characterized by X-ray crystallography. Several are members of very rare classes of functionalized boron compounds (boron azide, nitro compound, nitrous ester, etc.).