Organic Chemistry

Biography

Biography: Ju You Lu

Abstract

Carboranes, a class of three-dimensional relatives of benzene, having many applications in medicine as boron neutron capture therapy agents, in supramolecular design/materials as building blocks, and in coordination/organometallic chemistry as unique ligands, which have received growing interest. However, their unique structures make derivatization difficult, which results in a limited application scope. Thus, it is important and necessary to develop new methodologies for the functionalization of carboranes. It is obvious that a cross-coupling of 1-haloalkyl-o-carboranes with alkyl and aryl Grignard reagents would be an ideal methodology for the synthesis of cage C-monosubstituted o-carborane compounds. We initially investigated the reaction conditions using 1-(2-bromoethyl)-o-carborane and n-BuMgBr as model substrates. The optimal conditions for the Cu-catalyzed synthesis of mono-substituted o-carboranes are as follows: 20 mol% CuCl2 as the catalyst, 40 mol% PCy3 as the ligand, 2.0 equiv. of Grignard reagents as the coupling partners of 1-haloalkyl-o-carboranes, and the reactions were performed at 25oC under N2. After having optimized the model reaction, we were interested in extending the scope of the coupling reaction, and various o-carborane derivatives were prepared in good to excellent yields by using this copper-based procedure. The present copper-catalyzed protocol can be successfully used for the gram scale synthesis of 1-(n-hexyl)-o-carborane without an apparent decrease in the yield (4.0 g of product, 87.5% yield). The wide substrate scope makes this copper-based strategy remarkably practical for the synthesis of functional boron cluster compounds. We believe this general method will attract much attention and have broad applications in academic and industrial research.