Study On The Environmentally Friendly Suzuki Cross-Coupling Reaction Under Microwave Irradiation Condition

The palladium-catalyzed cross-coupling of aryl halides with boronic acids in presence of base, a Suzuki type reaction, is one of the most versatile and utilized reactions for the selective construction of carbon-carbon bonds, in particular for the formation of biaryls. In recent years, developments for the Suzuki reaction have received much recent attention that involve the catalysts, solvents, bases, reaction conditions and synthetic technique, which permit the use of organoboron compounds that are thermally stable and inert to water and oxygen. The low toxicity, stability and ease of handling of boronic acids have made them among the most popular intermediates for cross coupling reaction with variety of substrates. As the biaryl motif is found in a range of Pharmaceuticals, herbicides, and natural products as well as in conducting polymers and liquid crystalline materials. The destination of this dissertation is to develop Suzuki cross-coupling reaction in green chemistry and some possibilities for improvements especially in areas of solvent replacement, catalysis recycling, reaction times reducing, energy saving, and synthetic technique improving.The polymer-supported palladium(.II) is first prepared in the presence of ultrasound. The preparation of polymer-supported catalyst using ultrasound is certainly direct, rapid, and highly efficient. The polymer-supported palladium(II) with a Pd/P ratio of 1/1 gives very high activity in the Suzuki coupling of phenylboronic acid with aryl bromide. A comparative study shows that this catalyst is considerably more efficient than Pd(PPh3)4 or PdCl2(PPh3)2. XPS studies have been used to determine that the active state of the catalyst is metallic palladium. The polymeric catalyst can be easily separated from a reaction mixture and reused more than 5 times with no decrease in activity. This suggests that a comparatively stable palladium phosphine complex is the reacting species in this special case.It is possible to prepare biaryls in good yield very rapidly from aryl bromides andarylboronic acids or sodium tetraphenylborate using toluene-H2O or benzene-H2O as a solvent and polymer-supported palladium( II ) as catalyst. The reaction can be performed equally well using microwave and conventional heating, showing that these conditions probably no nonthermal microwave effects are associated with the impressive speed of the reaction.The development of a no solvent, microwave-promoted Suzuki coupling reaction utilizing a readily recyclable polymer-supported palladium catalyst offers numerous benefits. These include the straightforward recovery of both product and catalyst, conservation of energy through the use of microwave irradiation, simple commercial scale up, and low waste protocols due to the absence of solvents. The new reaction is convenient, environmentally friendly, and generates good yields of the coupled products. The use of microwave irradiation accelerates the reaction, decreasing reaction times from hours to minutes.Water is an inexpensive and nontoxic reaction medium for the microwave-promoted Suzuki cross coupling of arylboronic acids with aryl halides. This environmentally friendly microwave protocol offers convenient operation and synthesis of variety of substituted biaryls in good yield very rapidly employing PdCl2(PPh3)2 as catalyst and potassium carbonate as the base.A rapid, efficient, and atom economical cross-coupling reaction of sodium tetraphenylborate with aryl bromides using Pd(OAc)2 as a catalyst in water under microwave irradiation conditions gives polyfunctional biaryls in high yield. According to the stoichiometry and the yields, it would appear that the four phenyl groups of the sodium tetraphenylborate are available for phenylation. The effects of the structure of functional groups in aryl bomides, including some heterocyclized species on the reaction have been investigated. The commercially available and non-toxic sodium tetraphenylborate can be used in water for a rapid and efficient phenylation of aryl bromides that c...