Study On The Application Of Functionalized Quaternary Ammonium In Suzuki And Heck Reactions In Aqueous Media

The palladium catalyzed Suzuki and Heck reactions are well-established methodlogies in mordern organic synthesis. The coupling products are found to have good applications as intermediates in the preparation of natural products, medicines and polymers. We have studied the application of 1-akyl-4-aza-1-azoniabicyclo[2.2.2]octane halide in Suzuki and Heck reaction. This thesis is divided into four chapters.In chapter 1, we have outlined the recently development and the significance of the Suzuki and the Heck reactions in aqueous media.In chapter 2, a practical procedure for nano-palladium catalyzed Suzuki cross-coupling reaction in the presence of 1-butyl-4-aza-1-azoniabicyclo[2.2.2]octane bromide ([BDABCO]Br) in water media was investigated. The combined nano-Pd0/[BDABCO]Br/H2O catalytic system exhibited excellent functional group tolerance for various aryl halides and arylboronic acids and afforded moderate to excellent yields of the corresponding biphenyl products under air conditions. This protocol provided several advantages such as excellent yield, short reaction time, simple experimental and work-up procedure, and benign to environment.In chapter 3, a practical procedure for nano-palladium catalyzed Heck, Suzuki cross-coupling reaction and homocoupling of phenylboronic acid in the presence of 1-dodecyl-4-aza-1-azoniabicyclo[2.2.2]octane bromide ([DDABCO]Br) in water media was investigated. The combined nano-Pd0/[DDABCO]Br/H2O catalytic system afforded good yields of the corresponding products under air conditions. Furthermore, the catalyst system can be reused for at laest 6 recycles without losing its activities.In chapter 4, we have prepared and characterized palladium complex on the surface of silica-supported 1,4-diazabicyclo[2.2.2]octane(Pd@SiO2-DABCO), and investigated its performance in Suzuki cross-coupling reactions. The as-prepared catalyst (Pd@SiO2-DABCO) afforded 36-99% yields of the corresponding biphenyl products under air conditions. This catalyst has the advantages such as simple operation, high activity, recycling and reuse of catalysts and environmentally friend.