Collect. Czech. Chem. Commun. 2007, 72, 1740-1754

Preparation of Carboranyl and Dodecaborate Derivatives of Coumarin

Eugen Justusa,*, Dana T. Izteleuovab, Alexander V. Kasantsevb, Mendel M. Axartovb, Enno Lorka and Detlef Gabela,*

a Department of Chemistry, University of Bremen, D-28334 Bremen, Germany
b Department of Chemistry, E. A. Buketov's Karaganda State University, Karaganda, Kazakhstan


A series of derivatives of coumarin (2H-chromen-2-one) and 6,7-benzocoumarin (3H-benzo-[f]chromen-3-one) carrying the o-carborane, m-carborane, and dodecaborate clusters, has been obtained. X-ray structure analysis has been carried out for three of the products. The addition of o-carborane occurs in the 4-position of the coumarin ring, in a stereoselective way, independent of whether the cluster was reacted as the lithium or magnesium salt. m-Carborane gives two products, one being the result of 1,2-addition to an exocyclic ester bond and 1,4-addition to the coumarin system, the other resulting from 1,4-addition. The negatively charged dodecaborate derivatives obtained, link the cluster via oxygen or sulfur and an appropriate linker to a 7-hydroxy-substituted coumarin. For the coumarin derivatives, an o-carboranecarbonyl derivative could also be obtained.

Keywords: Boron clusters; X-Ray diffraction; Coumarins; Carboranes; Dodecaborate; Boron-neutron capture therapy; Carborane conjugates.

References: 16 live references.