Lewis Acids Mediated Cyclization Of Alkene

Heterocyclic compounds play a crucial role in the fields of pharmaceutical research,materials science,bioscience and so on.For their characteristic chemical structure,heterocyclic compound drugs show good to excellent pharmaceutical activity and become one of the most important active drugs that researchers focus on.Also,heterocyclic compounds display specific physical properties in material chemistry.In organisms,N-heterocycles build up the basic group of RNA and this is an example to explain the importance of N-heterocycles.Thus,the study on N-heterocycles attracts much attention of researchers.1,3-Benzoxazines are important compounds in N-,O-heterocycles.The 1,3-Benzoxazines possess the excellent drug activities and the potential to transform into more complex compounds.Besides,the application of benzoxazines in materials lead to the obtaining of antioxidant and corrosion resistance materials.In recent years,benzoxazines attract much attention from the word and the methods to synthesis of the compounds were developed rapidly.In a typical process,benzoxazines could be synthesized through the reaction between 2-aminobenzyl alcohol and various aldehydes & ketones under certain conditions.Transition metal-catalyzed or the cyclization reaction of O-alkynylbenzamide under metal-free conditions were alternative methods to obtain benzoxazines.However,the methods that reported showed up some disadvantages,such as long reaction time,harsh and complex reaction conditions.Therefore,this dissertation introduced a “green” process to synthesize3,1-benzoxazines.The 3,1-benzoxazines were obtained through the intramolecular cyclization of amide and double bond in the presence of Lewis-acid.In the current method of introducing a-F atom,electrophilic fluorination has been developed to be quite mature,while nucleophilic fluorination has been reported relatively less.Therefore,we designed a benzoxazine derivative while introducing a fluorine atom into the molecule using a nucleophilic fluorine reagent.The distinct advantages such as method simple operation,mild reaction conditions,metal-free,functional group tolerance,low cost,short reaction time and high yields of our process made it a promising process in future applications.