Palladium-Catalyzed Dehydrogenation Of Saturated Aldehydes And Ketones

Unsaturated carbonyl structural motif is not noly embedded in numerous natural products,drug molecules and bulk chemicals,but also used as versatile synthetic intermediates for diverse organic transformations.Here,We develop a new type of dehydrogenation strategy for synthesis of ?,?-unsaturated aldehydes and ketones,and ?,?,?,?-conjugated(E,E)-dienones and(E,E)-dienals,using palladium acetate as the catalyst,and trifluoroacetic acid as an important additive.Notably,the approach has been applied into the synthesis of a natural product.This dissertation includes four chapters as below:Chapter 1.Review for recent dehydrogenations of saturated aldehydes and ketonesThis chapter mainly introduces the research on the dehydrogenation of saturated aldehydes and ketones in recent years.Compared to the other dehydrogenation strategies,palladium-catalyzed dehydrogenation has been widely studied and applied.As for the substrates,cyclic ketones,especially cyclohexanones,has been well studied.But for linear substrates,there are only few reports.Moreover,these catalytic dehydrogenative reaction systerm usually had a narrow substrate scope for linear ketones and aldehydes.Therefore,the development of a facile,economic and efficient catalytic dehydrogenative method with a broad substrate scope is still highly desirable but challenging.Chapter 2.Synthesis of enones and enals via dehydrogenation of saturated ketones and aldehydes.A general,efficient and economic palladium-catalyzed dehydrogenation to form enones or enals was developed.The method shows extremely broad substrate scope including various linear or cyclic saturated ketones and aldehydes.The protocol is ligand-free,and molecular oxygen is used as the sole clean oxidant in the reaction.Due to mild reaction conditions,good functional group compatibility,and versatile utilities of enones and enals,the approach can be found many applications in the synthesis and the late-stage functionalization of pharmaceuticals and fine chemicals.Chapter 3.Palladium-catalyzed ?,?-dehydrogenation of enals and enones to synthetize conjugated(E,E)-dienones and(E,E)-dienalsThe first palladium-catalyzed ?,?-dehydrogenation to produce dienones and dienals with E,E-configuration selectivity in high yield has been successfully developed.The protocol is ligand-free,and molecular oxygen is used as the sole clean oxidant in the reaction.The approach possesses extremely broad substrate scope including various(E,E)-dienones and different kinds of(E,E)-dienals.Notably,we employed the ?,?-dehydrogenation as a key step to finish the total synthesis of natural product piperine.Chapter 4.Synthesis of dienones and dienals via palladium-catalyzed domino-dehydrogenation of saturated ketones and aldehydes.The first palladium-catalyzed ?,?,?,?-domino-dehydrogenation to produce dienones and dienals has been successfully developed.In this protocol,the ?-C-H,?-C-H,?-C-H,and ?-C-H bonds of the linear aldehyde ketone carbonyl are simultaneously cleaved and eliminated,resulting in two consecutive double bonds.The protocol is ligand-free,and molecular oxygen is used as the sole clean oxidant in the reaction.The approach provides a new synthetic method for the synthesis of conjugated(E,E)-dienones and(E,E)-dienals.