New methods for allylic functionalization: Selenium- and palladium-catalyzed reactions

Abstract

The selenium- and palladium-catalyzed synthesis of new carbon---carbon and carbon---heteroatom bonds is the focus of the research described in this dissertation. Specifically, oxidative halogenation of olefins was catalyzed by PhSeCl in the presence of N-chlorosuccinimde. Using sterics and electronics to bias regioselectivity, the reaction afforded a variety of functionalized allyl chlorides in good yields. Furthermore, the selenium-catalyzed bromolactonization of unsaturated carboxylic acids was also achieved with increased regioselectivities as compared to the uncatalyzed reaction. Also reported are new methods for palladium-catalyzed allylic functionalization. First, the formation of new C-N bonds is detailed in the Pd-catalyzed decarboxylative coupling of carbamates producing allylated heteroaromatic amines. A new method for the construction of C-Se bonds is also reported through the palladium-catalyzed decarboxylation of selenoformates. Using chiral ligands, high enantioselectivities of the allyl selenide products could be obtained. The cross-coupling of allyl species is also detailed in this manuscript. To begin, allyl dicyanobutenoates underwent decarboxylative coupling to afford α-allylated compounds as the kinetic hexadiene product upon treatment with palladium(0) catalysts. Isolation of the thermodynamic γ-allylation product was also possible through a Cope rearrangement or via a tandem decarboxylative allylation/Cope rearrangement. High enantioselectivities and moderate diastereoselectivities were obtained using chiral ligands and microwave irradiation. Lastly, the palladium-catalyzed allylation of heteroaromatic alkanes is also described. Unusual regioselectivities and high diastereoselectivities were observed for this process and are explained via a mechanism involving a tandem decarboxylative dearomatization/aza-Cope rearrangement.