Cleavage And Transformation Of 2,3-allenol C-O Bonds And Thiol Ester C-S Bonds

This dissertation focuses on the investigation of cleavage and transformation of the C-O bonds of 2,3-allenols and the C-S bonds of thiol esters.Chapter 1 summarizes the research progress in the transformation of 2,3-allenols and their derivatives via the C-O bond cleavage.Considering type of products and reaction mechanism in the cleavage of C-O bond,we reviewed the progress in synthesis of 1,3dienes/enones,synthesis of enynes,synthesis of allenes and synthesis of cyclization products respectively.Chapter 2 describes the study on palladium-catalyzed silylation/borylation of 2,3allenols with unactivated disilanes/diboronate.At first,the reaction of unactivated disilanes with 2,3-allenols under catalysis of Pd2(dba)3/P(o-MeOC6H4)3 is discussed.In the presence of CS2CO3,the reaction afforded 2-silyl-1,3-dienes.Reaction of 1-aryl2,3-allenols yields the products with excellent E stereoselectivity.Reaction of αalkylallenols or α-alkyl-α-arylallenols results in the products with moderate Z/E selectivity and E-isomers are the major products.Without a base,the reaction producesα-silyl-β-hydroxyl vinylsilanes,which can be converted to 2-silyl-1,3-dienes upon treatment with Cs2CO3.Next,the reaction of 2,3-allenols with diboronate under catalysis of Pd2(dba)3/PCy3 is presented.A range of 2-boryl,3-dienes were obtained.The reaction does not require the presence of a base and is presumed to proceed via αboryl-β-hydroxyl vinylboranes.Chapter 3 presents copper-catalyzed reaction of 2,3-allenols with silylzinc reagents.Regioselective silylation of 2,3-allenols with silylzinc reagents was carried out under catalysis of IPr-CuCl or SIPr-CuCl,achieving 2-silyl-1,3-dienes stereospecifically.Reaction of secondary 2,3-allenols gave(E)-2-silyl-1,3-dienes as sole products.Compared with the palladium-catalyzed silylation of 2,3-allenols,this protocol features the use of inexpensive copper catalysts and high stereoselectivity of products.Chapter 4 introduces palladium-catalyzed reaction of 2,3-allenols with amines to afford[3]dendralenes and 1,3-dienes selectively.When the reaction was performed using[Pd(π-allyl)Cl]2/P(2-furyl)3 as catalyst and MeOH as solvent,(Z)-configurated[3]dendralene derivatives were obtained.When the reaction was carried out using Pd(OAc)2/P(2,furyl)3 as catalyst and iPrOH as solvent,(1Z,3E)-1,3-diene derivatives were formed as sole products or major isomers.Chapter 5 deals with palladium-catalyzed coupling reaction of thiol esters with azoles via C-S/C-H bond cleavage.In the presence of Pd2(dba)3/P(m-MeC6H4)3,CuCl and tBuONa,reaction of ethanethiol esters with azoles was performed to afford di(hetero)aryl ketones.Functional groups including CF3,CN,NO2,F,Cl,COOR,and SMe are tolerated.It is the first example of C-H acylation of azoles with thiol esters as acylating agents.In addition,Pd2(dba)3/dcype-catalyzed decarbonylative reaction of dodecanethiol esters with benzoxazoles to afford 2-arylbenzoxazoles was also carried out.