The Aerobic Functionalization Of Sp~3 C-H Bond In N-aryl-alaninates

According to the concept of green and sustainable chemistry,designs,preparations and applications of new catalysts attract extensive interests of organic chemists.Due to its inexpensive,and environmentally friendly nature,molecular oxygen might be one of the best oxidant in oxidation reactions,However,since the reactivity of dioxygen is limited,activation of dioxygen is still crucial in most aerobic oxidation reactions.In the past decade,we developed an new catalyst system,TBPA+·/O2,to promote C-H bond oxidation reactions,in which TBPA+.can efficiently accelerate the participation of dioxygen in aerobic oxidation reactions.This catalyst system might potentially be a candidate to replace other stoichiometric oxidants(DDQ,peroxides,Oxone,etc.),which were used extensively in the Cross-Dehydrogenative Coupling(CDC).Using this catalyst system,a series of sp3 C-H functionalization were achieved,constructing various quinoline skeletons in high yields.The details were listed as below:1.A series of 1,2-dihydroquinoline skeletons were constructed efficiently through sp3 C-H bond oxidation of N-arylallaninates under catalytic radical cation salt-promoted conditions.Investigation of the psssible mechanism shows that the reaction was mediated by a free radical intermediate.This method provides a new way to synthesize 1,2-dihydroquinoline derivatives from easily accessible starting materials.2.A dual removable activating group enabled Povarov reaction of N-arylalanine esters was developed.N-Arylalanine ester was utilized as the sole carbon source to generate N-arylimine and its tautomer,enamine,in situ by aerobic oxidation of sp3 C-H bond,and then the consecutive reaction delivered the desired quinoline-4-carboxylate esters in high yields.In this reaction,the electronic properties-forbidden[4?+2?]hetero-Diels-Alder cycloaddition was achieved by a roundabout way.