Applications Of Oximes Cyclization Reactions In The Synthesis Of Nitrogen-Containing Heterocycles

Nitrogen-containing heterocycles,as the most abundant heterocyclic compounds,not only are important organic synthetic intermediates but also widely exist in pharmaceutical products,pesticides,dyes and some polymer materials.Therefore,the synthesis of nitrogen-containing heterocycles has drawn considerable attention of chemists for over a century,and a variety of methods have been reported.However,due to the limitations of previous methods,the development of green,efficient and atom economic protocols for the synthesis of nitrogen-containing heterocycles is still a research hotspot in synthetic chemistry.In recent years,oximes as readily available and versatile building blocks have been used to synthesize many nitrogen-containing heterocycles.In view of the application prospect of oxime in the synthesis of nitrogencontaining heterocycles,we explored the radical and ionic cascade cyclization reactions of unsaturated ketoximes in this dissertation,and a series of functionalized isoxazolines,cyclic nitrones,pyrrolones and furo[3,2-b]pyrroles with potential biological activity have been constructed.The thesis contains four chapters:Chapter 1: The Baldwin and Baldwin-Beckwith rules are briefly described,followed by the review on the research progress of oxime-mediated radical and ionic cyclizations.Chapter 2: A facile and efficient vicinal oxyalkynylation/aminoalkynylation of unactivated alkenes has been achieved by means of iminoxyl radical-promoted dichotomous cyclizations.This protocol enables the synthesis of useful alkynylfeatured isoxazolines and cyclic nitrones by using ethynylbenziodoxolone(EBX)as the oxidant as well as the alkynylating reagent.Chapter 3: An iminoxyl radical-promoted sequential catalytic cyclization strategy has been developed by the reaction of linear alkyne-tethered ketoximes with EBX reagents.By the diversification of catalytic sequences,a series of structurally novel enyne-containing isoxazolines with a single configuration,alkynyl-featured 3H-pyrrol-3-ones and chlorinated furo[3,2-b]pyrroles are divergently synthesized under the catalysis of Cu,Cu/Ir photosensitization and Cu/Ir photosensitization/Al Cl3,respectively.Simultaneously,the abovementioned reaction also presents the first example of [1,4] radical migration of oxygen-atom,which broadens the new boundary of heteroatom radical migration.Chapter 4: A cascade hydroamination/hydrocyanation of oxime-tethered alkynes has been developed by copper powder mediated ionic cyclization of alkyne-tethered ketoxime employing trimethylcyanosilane as the cyanating reagent.As a result,a series of structurally important ?-cyano cyclic nitrones were efficiently prepared.The regioselectivity of terminal alkyne and internal alkyne ketoximes in hydrocyanation process is completely different.