The Synthesis Of Carbamates And Ketene Aminals With Hypervalent Iodine(?) Reagents

Hypervalent iodine compounds,especially Togni's reagent and Ethynylbenziodoxoles (EBXs),are widely used in the fields of organic chemistry,drug synthesis and polymer materials due to their special structure and high chemical reactivity.Most of the researches on Togni's reagent and EBXs mainly focus on trifluoromethylation and alkynylation reactions,while there are few reports on the use of the reagents as new synthon for product construction.Organic carbamates and ketene aminals are both important nitrogen-and oxygen-containing compounds.Among them,carbamates constitute an important class of biologically active compounds,which widely used in medicinal chemistry,polyurethanes as well as insecticide products and industry.Ketene aminals have been widely used as versatile building blocks for the construction of a range of medicinally relevant heterocyclic compounds.In this reagrd,this thesis studied the synthesis of carbamates and ketene aminals with hypervalent iodine(?)reagents.The details are as follows:(1)A copper-catalyzed four-component formal oxyaminalization of alkenes with Togni's reagent and amines using molecular oxygen as both the oxidant and oxygen source has been developed for the first time,offering a straightforward and efficient method for the synthesis of a range of structurally diverse?-oxoketene aminals.The use of cheap copper catalyst and readily available substrates,excellent functional group tolerance,broad substrate scope,mild conditions,and simple procedure are the attractive features of the strategy.(2)A copper-catalyzed four-component reaction of alkenes,Togni's reagent,amines and CO₂ has been successfully developed for the first time,which provides an efficient and straightforward method for the synthesis of a range of stereodefined(Z)-enol carbamates.Easily available starting materials and cheap catalyst,high stereoselectivity,good functional group tolerance and broad substrate scope are the features of the transformation.The mechanistic aspects of this transformation have been elucidated by control experiments and density functional theory calculations.(3)A copper-catalyzed cascade cyclization of 1,n-enynes with Togni's reagent,carbon dioxide,and amines has been successfully developed.The reaction provides a direct and efficient route to a range of trifluoromethyl-substituted carbamates.Mild reaction conditions,good functional tolerance,and wide substrate scope are the feactures of the protocol.(4)The first visible light-mediated stereodivergent synthesis of?-iodoenol carbamates from ethynylbenziodoxoles,CO₂ and amines is disclosed.By choosing appropriate photocatalysts,both Z-and E-isomers of?-iodoenol carbamates can be acquired selectively.This transformation also featured mild reaction conditions,excellent functional group compatibility and broad substrate scope.The potential utility of this protocol was demonstrated by elaborating the products to access a wide range of biologically relevant carbamate compounds and stereodefined trisubstituted alkenes.A series of mechanism investigations revealed that the transformation might proceed through a charge-transfer complex which might be formed through a halogen bond.