Alkylation Of Azoles And Coumarins By C-H Functionalization

As the most basic chemical bond,C-H bond is widely present in various organic compounds.Construct C-C or C-X bonds?including C-O?C-N and C-P?by directly activation of C-H is called C-H functionalization.Compared to transition metal catalyzed cross-coupling reactions,such as Heck,Suzuki,Negishi reaction et al,C-H functionalization does not require pre-functionalization of the substrate,shortens the reaction step,and increases product yield.Therefore,it is a simple and efficient protocol in organic synthesis.Azoles and coumarins are natural compounds with good biological activity and are two important structural nucleus in drug molecules.This paper introduces two C-H functionalization reactions based on free radical processes and applies them to the synthesis of N-alkylazoles and 3-alkylcoumarins,respectively.Main content are as follows:The first part of the article developed an efficient method for the synthesis of N-alkylazoles without any metal catalyst.This strategy used PIDA?iodobenzene diacetate?as oxidant,did not require any catalyst,and a series of N-alkylazoles were synthesized by cross-dehydrocoupling of 1H-azoles with sp³ C-H adjacent to hetero atom in moderate to excellent yield?46-96%?.This transformation was suitable for a wide range of azoles,and the“C?sp³?-H”species such as ethers,thioethers,N-methylpyrrolidone with mild reaction conditions,high oxidant utilization?only 1.0eq?,good selectivity and low pollution.The second part of the article described an decarboxylation coupling between NHP esters and coumarins by using fac-Ir?ppy?₃ as photocatlyst and TFA as additive,developing a novel method for construction of C?sp²?-C?sp³?bond and affording the3-position alkylation of coumarins in moderate to excellent yield?30-90%?.This protocol owned advantages such as oxidant free,extensive substrate tolerance,mild condition,excellent regioselectivity,moreover,synthesized a series of 3-chain alkylated coumarins for the first time.