Palladium-Catalyzed Synthesis and Transformation of Organoboranes

Abstract: This thesis presents the development of new palladium-catalyzed transformations involving synthesis and application of allylborane reagents. In these reactions various palladium sources, including pincer complexes and commonly used catalysts were applied.A new transformation for allylation of aldehyde and imine substrates was devised using allyl acetates, diboronate reagents and catalytic amounts of Pd2(dba)3. By employment of commercially available chiral diboronates enantioenriched homoallyl alcohols could be obtained.We have also developed a palladium-catalyzed method for synthesis of functionalized allylboronic acids from vinyl cyclopropane, vinyl aziridine, allyl acetate and allyl alcohol substrates using diboronic acid as reagent. In this process a highly selective selenium based pincer-complex was used as catalyst. The resulting allylboronic acid products were converted to potassium trifluoro(allyl)borates or allylboronates.The functionalized allylboronic acids generated in the above procedure were employed as reagents in two synthetic transformations. One of these transformations involves a palladium(0)-catalyzed coupling reaction between allylboronic acids and aryl iodides. The reaction was regioselective for the branched allylic product, typically difficult to prepare in the absence of directing groups. We also developed another transformation for allylation of aldehydes with allyl alcohols via allylboronic acid intermediate. This procedure can be performed as a simple one-pot sequence affording homoallyl alcohols with excellent stereo- and regioselectivity.