Studies On Radical Tandem Cyclization Reactions Of 1,6-Enynes:Synthesis Of Carbocycles And Heterocycles

In this thesis,the synthesis of the sulfonyl cyclization products and seven-membered dihydrooxepines from free radical cyclization of 1,6-enyne was established.It was chiefly involve the following five chapters.Chapter OneIn the first chapter,various enyne cyclization reactions were briefly summarized.In general,strategies for enynes cyclization could be classified into two types,that is,transition-metal catalyzed cyclization and radical cyclization.The main process of transition metal-catalyzed enyne cyclization involved: a)metal complexed with both double and triple bonds at the seam time constructing the metallacycle complex,b)hydrometalation of the alkyne formed vinylmetal,c)via metal ?-allyl complex.On the other hand,the C(28)C bond or C?C bond as a preferred free radical acceptor depended on the regioselectivity of enyne under different conditions.Chapter TwoIn the second chapter,the development of sulfonylation reaction was introduced.The sulfonyl hydrazine,sulfonyl chloride,sodium sulfinate,sulfinic acid,mercaptan,DMSO,and some other sulfonyl sources conducted with different substrates obtained various significant sulfonyl compounds.Among these,sulfonyl hydrazides and sodium sulfinate were mainly used as the source of sulfonyl groups.Chapter ThreeIn the third chapter,an iodine-promoted/mediated one-pot radical cyclization reaction of 1,6-enynes with sulfonyl hydrazides to provide five-membered and hexatomic ring sulfonylated products under the same conditions is established.The reaction proceed smoothly in water and gave the corresponding products in good to excellent yields by using I2/TBHP instead of expensive and toxic catalysts with C-S and C-I bond formed in one-step.This method also allowed easy access to significant functional sulfones for potential applications in medicinal and organic chemistry.Chapter FourIn the fourth chapter,the progress of the formation of seven-membered rings by the enyne cyclization is established.Two different substrates of enyne were employed for the synthesis of the seven-membered ring skeleton.Among these,the main method for the enyne to construct functionalized seven-membered ring was the transition-metal catalyzed [5+2] cycloaddition reaction.Chapter FiveIn the last chapter,a copper-catalyzed [2+2+3] annulation of 1,6-enynes with ?-bromo-1,3-dicarbonyl compounds for the synthesis of dihydrooxepines,in which two new C-C bonds and one C-O bond were formed through radical process in one step is described.The seven-membered dihydrooxepine is indentified to be significant scaffold in the epidithiodiketopiperazines and widely existed in a class of important natural products.