869653-86-1Relevant academic research and scientific papers
Efforts directed toward the synthesis of colchicine: Application of palladium-catalyzed siloxane cross-coupling methodology
Seganish, W. Michael,Handy, Christopher J.,DeShong, Philip
, p. 8948 - 8955 (2005)
Colchicine is an important and synthetically challenging natural product. The key synthetic step in this approach to the synthesis of colchicine involved a palladium-catalyzed cross-coupling reaction between 5-bromotropolone (4) and an aryl siloxane to form the aryl-tropolone bond. The coupling of a variety of highly functionalized aryl siloxane derivatives was investigated and optimized coupling conditions were developed. It was discovered that a palladium catalyst with a high degree of phosphine ligand coordination (5 equiv of phosphine/mol Pd) was necessary to efficiently couple aryl siloxanes with 5-bromotropolone (4). In addition, the coupling approach has provided a direct comparison between siloxane and boronic acid coupling technologies that demonstrated that aryl siloxanes and boronic acids produce similar yields of highly functionalized biaryl products.
