In this dissertation,we focused on the novel cascade reactions mediated by hypervalent iodine reagents.Generally,five kinds of new cascade reactions with high efficiency have been developed as follows:?1?Firstly,the reaction of 1,2-darylalkynes with phenyliodine?III?bis?trifluoroacetate??PIFA?resulted in 35 structurally novel spiro[indoline-2,1'-isoindoline]-3,3'-diones.This unprecedented process encompasses not only two sequential C-N/C-O bond formations,but also the insertion of a carbonyl oxygen,all in one pot under metal-free conditions.Two reasonable mechanisms were proposed after further investigation on the insight of the effective transformation.?2?Secondly,it was discolosed that an exclusive trans-aminocarboxylation and oxoaminocarboxylation of 2-??2-?sulfonamido?phenyl?ethynyl?benzoic acid can be converted to 17 fused and 12 spiro polycyclic heterocycles in the presence of lewis acid and phenyliodine?III?diacetate?PIDA?.This novel protocol features not only a BF3·Et2O-catalyzed selective lactonization but also an intramolecular oxidative C-N bond formation process.Notably,both of the products could be obtained through a“one-pot”strategy.?3?Then the isochromenoindolones obtained above can undergo a ring-contraction process involving saponification?or amidation?,disproportionation and spirocyclization to give N-unsubstituted spiro[indoline-2,1?-isobenzofuran]-3,3?-diones and spiro[indoline-2,1?-isoindoline]-3,3?-diones.The advantage of this method includes one-pot,mild conditions,simple operation,transition-metal-and oxidant-free,excellent yields at gram-scale with no column chromatography purification necessary.18 N-H polycyclic products further improved the compound library of spiroindolones.?4?Further study on the aboved mentioned BF3·Et2O-catalyzed selective lactonization shows various readily available 2-alkynyl benzoic acids are of high efficiency,affording 21 isochromenone derivatives.In this project,we can control the electronic effect to selectively form the five-membered and six-membered products.?5?In addition,it was found that enamines can be transferred to2-aryl-indole-3-carboxamides,which could realize the final oxidative C–N bond formation to give 16 cytotoxic bioactive molecules indoloquinolinones. |