Part I : Selective heck-type reaction of cyclic olefins. Part II : Palladium-catalyzed alkylation of heteroarenes
Date of Issue2015
School of Physical and Mathematical Sciences
Palladium-catalyzed cross-coupling reaction has become an important tool in organic synthesis. The thesis describes three new methods to selectively forming new C-C bonds in the presence of palladium catalysts. In chapter one, we reported two efficient catalysts for Mizoroki-Heck reaction of cycloolefins with aryl triflates and aryl halides respectively. With our Pd/dppp catalyst, various aryl triflates and cyclic alkenes could selectively generate vinylic products in good to excellent yield. Notably, the isomeric purity of products was >95% in most cases. The Pd/PtBu3 catalyst coupled a wide array of aryl halides. Several cycloolefins, which have poor reactivity in the reaction with aryl triflates, also reacted well. Therefore, two complementary approaches successfully solved the vinylic selectivity in Mizoroki-Heck reaction of cyclic olefins and provided a simple strategy to produce 1 -arylcycloolefins. In chapter two, we developed a general protocol to selectively generate Catellani isomers. By using the bulky PtBu3 ligand, various (hetero)aryl bromides and chlorides bearing no ortho substitution can be coupled efficiently with norbornene. Moreover, other bicyclic alkenes besides norbornene can also undergo this type of transformation. Previously, the Catellani isomers were only formed from phenyl bromide and phenyl halides bearing orthogroups. In chapter three, we explored a general Pd-catalyzed alkylation method for heteroarenes. By the simple Pd/dppp catalyst, topical classes of heteroarenes including azoles, azines, furans, thiophenes, pyrroles, pyridines and even indole derivatives can efficiently be coupled with various unactivated secondary and tertiary alkyl halides in good regioselectivity. Notably, our radical-type alkylation is compatible with sensitive functional groups such as nitriles, aldehydes and ketones. Therefore, our alkylation of heteroarenes is a complementary method to other transition metal-catalyzed alkylation processes, which are based on the initial metalation of C-H bonds.