The Study Of Oxetanes As Alkylating Reagents For The Catellani Reaction

Catellani reaction,in the presence of cooperative catalysis of palladium and norbornene,enables difunctionalization both at ortho position and ipso position of aryl halides at the same time.Two types of reagents provide different functional group combinations on aryl halides,two bonds in various polysubstituted aromatic compounds are constructed in one step reaction.Catellani reaction has been widely used in the field of C-H functionalization to construct two or more carbon-carbon or hetero-carbon bonds in polysubstituted aromatic compounds due to its advantages of easy access of starting materials,selective ortho and ipso functionalization and high step economy.Among studies of Catellani reaction to date,research on nucleophile is extensive.In contrast,there are few studies on electrophiles,especially those with high atomic economy.Therefore,this thesis focuses on the combination of Catellani reaction and a ring tension-assisted system of a novel cyclic heteroatomic electrophilic reagent.For the first time,atomic economic oxetane was used as an ortho-alkylation reagent to participate in Catellani reaction with respective ipso-terminations employing olefin,alkyne,aryl boric acid,sodium formate and deuterated sodium formate.Various ipso-functionalized 3-phenylpropanols were efficiently synthesized within 2 hours.The reaction was promoted by the cooperative catalysis of Pd（OAc）₂and C5,C6-cyclohexyl ester substituted NBE derivative.More importantly,this reaction system employed the Lewis acid Al Cl₃ or Br?nsted acid HCl（aq.）as the co-catalyst for the first time,which is unusual in the conventional Catellani-type reaction.Notably,this reaction utilizes abundant and readily available reagents as the starting materials and is compatible with a wide variety of substrates（47 examples）.The reaction promotes ring opening of various C2 and C3-substituted oxetanes mostly at less hindered positions,providing the corresponding products with excellent regioselectivity and high efficiency（the yield is up to 94%in case of aryl iodides,93%in case of olefins and 93%in case of oxetanes）.Moreover,this ortho-alkylation process can be applied to a series of different termination processes including Heck reaction,Sonogashira reaction,Suzuki reaction,Protonation/Deuteration reaction and so on.