Studies On The Synthesis Of N-vinylindoles Based On Palladium-catalyzed Oxidative Cross-coupling Of Tosylhydrazones With Indoles

Metal carbene has attracted enormous attention due to its wide application inorganic synthesis. Transition-metal-mediated decomposition of α-carbonyl diazocompounds is a reliable method to obtain metal carbene species. However, diazocompounds without an electron-withdrawing group are usually unstable and difficultto handle, which significantly limits the application of this type of precursor.N-Tosylhydrazones, which are readily obtained by the condensation of aldehydes orketones with commercially available tosylhydrazides, represent a class of stablenitrogenated-compounds, and has emerged as a new type precursor for the in-situgeneration of metal carbene species.Barluenga’s first employment of N-tosylhydrazones in the Pd-catalyzedcross-coupling reaction in2007, which proceeded via the Bamford-Stevensintermediate, has significantly reinvigorated the use of N-tosylhydrazones, whichwere derived from the corresponding aldehydes or ketones, as the precursors of insitu-generated nonstabile diazo compounds in the formation of C-C, C-O, C-P, C-S,C-B, and C-N bonds through both metal-catalyzed and metal-free processes.Migratory insertion involving a palladium carbene was proposed to constitute the keystep in these processes. To the best of our knowledge, C-N bond formation usingN-tosylhydrazone as a carbonyl surrogate has been rarely reported. Based on that, wehave reported a novel approach to N-vinylindoles via Pd-catalyzed oxidativecross-coupling of N-tosylhydrazones with indoles. The reaction proceeded in astereo-controlled manner. And a wide variety of N-vinylindoles were obtained up to99%yields for26examples.Apart from that， we have further explore the hydroxylation of arylboronicpromoted by benzoquinone in water to provide an alternative efficient and practicalmethod.