Study On The Rh(Ⅲ)-catalyzed C-H Bond Activation/Annulation To Construct Heterocyclic Compounds

In recent decades,transition-metal-catalyzed C-H bond activation/annulation and direct functionalization of C-H bonds represents as convenient synthetic strategies towards molecules with specific activities.In the presence of transition metals,C-H bonds can be transformed into various valuable chemical bonds,for the efficient synthesis of products.As a VIII group transition metal,rhodium has excellent catalytic activiries that widely used in many reactions,especially in C-H bond activation/cyclization reactions.In addition,the introduction of a certain directing group can result in precise site-selectivity in reactions.For example,imines,amides and some heterocycles are commonly used directing groups.Transition-metal-catalyzed and directing group promoted organic synthesis has become the most common and effective synthetic strategy for selective C-H bond activation.In this thesis,we studied the Rh-catalyzed C-H bond activation/cyclization to synthesize heterocyclic compounds such as polycyclic quinazolinones and quinazolines.The thesis mainly includes the following two parts:(1)Rhodium-catalyzed [4+1] annulation of 2-aryl quinazolin-4(3H)-ones with sulfoxonium ylides towards polycyclic quinazolinones.This transformation proceeds with the sequential chelation-assisted ortho-C-H functionalization and intramolecular rhodium-catalyzed α-amination of carbonyl to afford the desired products.The range and adaptability of substrates were studied,which proved that the reaction can tolerate a variety of functional groups.In addition,some 13-aroyl luotonin A derivatives were afforded by the direct construction of ring C under our conditions.The H/D exchange experiment showed that the cleavage of ortho-C-H bond was reversible.(2)Rhodium-catalyzed annulation of N-phenylbenzamidine and vinylene carbonate.This procedure proceeded with sequential ortho-acylation and [5+1]annulation,leading to 4-methylquinazolines in moderate to excellent yields.In this transformation,the vinylene carbonate served as acetylation reagent rather than ethyne surrogate.The effects of different substituents on N-phenylbenzamidines were also studied.The potential applications of the product was explored by further functionalizations.Intramolecular and intermolecular KIE experiments showed that the cleavage of ortho-C-H bond of N-phenylbenzamidine was the rate determining step in the transformation process.The reaction represents a facile and mild pathway leading to4-methylquinazolines with complexity and diversity.