Photoredox-promoted Sulfonamidyl Nitrogen Radical Addition/Semipinacol Rearrangement Of Alkenylcyclobutanols:Synthesis Of Amino-spirocyclic Ketones And 2-aminomethyl-2-aryl-cyclopentanones

The semi-pinacol rearrangement reaction has received more and more attention of organic chemists in recent years.The semi-pinacol reaction is an effective method for the construction of the complicated molecular skeletons constructing of quaternary carbon center.The formation of electropositive carbocation is the key to the semipinacol rearrangement reaction.Since the 21st century,the visible light photoredox promoted reaction is receiving more and more attentions due to its mild reaction condition,higher atom conversion efficiency and good functional group compatibility.Since then,visible light mediated semi-pinacol rearrangement reactions have been reported,usually alkenylcvclobutanol compounds are used as the radical receptors.In this thesis,a photoredox-promoted radical addition/semi-pinacol rearrangem-ent reaction for the construction of amino spirocyclic ketones and 2-aminomethyl-2-aryl-cyclopentanones is presented when alkenylcyclobutanols are used as the sub-strates and sulfonamides as the nitrogen radical precursor.Firstly,when benzocycl opentallyl alcohol are used as the substrate and the N-protected 1-aminopyridinium salts are employed as the nitrogen radical precurosor under visible light irradiati-on,the desired amino-spirocyclic ketones are obtained.The reaction condition,su-ch as different photocatalysts,reaction solvents,visible light source and the ratio of reactants,are well explored,the optimized condition for the reaction is establi-shed as follows:2 mol%fac-Ir(ppy)3 was used as the photocatalyst,acetone as t-he solvent,6 W Blue LEDs as the visible lights,no base is needed,room tempe-rature.Finally,a series of benzocyclopentallyl alcohols and N-protected 1-aminop-yridinium salts are compatible for the reactions,22 amino spirocyclic ketones are obtained in 49-94%yields.(?)In addition,styrene cyclobutanols are good candidate substrates for the reaction,and 9 amino cyclopentanones are generated in 51-95% yields.(?)All the desired products were fully,characterized by IR.1H NMR,13C NMR.and HR-MS spectra,and the spectroscopic properties are well studied.Based on our mechanism investigations and other related references,a possible mechanism was proposed.(?)...