Aryltriazenes as Coupling Partners in the Hiyama, Hiyama-Suzuki and Hiyama-Heck Cross-Coupling Reactions Using Conventional and Ionic Liquid Reagents and Solvents

Application of conventional and ionic liquid (IL) solvents and reagents in the Hiyama cross-coupling reactions using triazenes as coupling partners was investigated. The microwave-assisted and Pd-catalyzed reactions in ROH/HBF4, ROH/BF3 center dot Et2O and in [BMIM][X]/[BMIM(SO3H)][OTf]/[BMIM][F] proved effective and gave respectable isolated yields within minutes. The scope of the Hiyama coupling reaction with triazenes was investigated in these media. The IL reagents and solvents were successfully employed to develop stepwise and sequential/tandem HiyamaSuzuki (H S) and Hiyama-Heck (H H) methods. Study of the scope of these transformations led to facile synthesis of libraries of biaryls, hetero-biaryls, diphenylmethanes, styryl-biphenyls, and a host of biphenyl-appended heterocycles. The potential for the recycling/reuse of the IL solvents in the Hiyama reaction, and in stepwise and sequential transformations was also examined.