Palladium-Catalyzed Propargylation/Allenylation/Allylation Of Chloromethylarenes And Isomerization Of Allylarenes

In current research developing high selective methods to produce a variety of new C-C and C-heteroatom bonds are highly desirable.Among these methods regio-and chemo-selective C-H functionalization reactions under mild conditions with a wide range of substrate scope have attracted a considerable attention.Synthetic methodologies using unfunctionalized reagents have been explored as an alternative tool towards atom-and step-economical reactions.The(hetero)aromatic compounds being important skeleton structures frequently appear in pharmaceutical compounds,natural products,and functional materials.Besides this,their importance in agriculture,electronic,and polymer industry cannot be neglected.Owing to their immense significance,the derivatives of these chemical commodities have been synthesized through a number of transition-metal-catalyzed cross-coupling reactions.In this dissertation,the development of highly selective and efficient methods for the C-H functionalization of(hetero)aromatic compounds via ?-allylpalladium intermediates leading to the propargylation,allenylation,and allylation of chloromethlyarenes is described.Keeping in view the synthetic value of styrene and its derivatives in organic synthesis,this study further reports the double bond isomerization of allylarenes.The detailed research contents and results are as follows;The palladium-catalyzed solvent-dependent product distribution of the propargylative and allenylative dearomatization reaction of 2-(chloromethyl)thiophenes with allenyltributylstannane under mild conditions is described in the second chapter of this dissertation.The propargylative dearomatization reaction selectively occurred to produce only the propargylic compounds in 63%-81%yields when the coordinating solvent acetonitrile was used.While in uncoordinating solvent dichloromethane,allenic compounds were obtained as major products ranging from 43%-57%.The unprecedented remote allylation of chloromethyl(hetero)arenes with allyl pinacolborate is described in the third chapter.This palladium-catalyzed regioselective allylation reaction proceeded smoothly via ?-benzylpalladium intermediates to produce para-allylated dearomatization products or para-allylated arenes.Notably,the formation of traditional Suzuki coupling products was not observed at all.Chloromethylarenes smoothly reacted with allylpinacolborate,producing para-allylated dearomatization products or para-allylated arenes in 70%-79%yields.2-(Chloromethyl)thiophenes and 2-(chloromethyl)furans bearing substituents on 5-positions also smoothly reacted with allylpinacolborate,producing 5-position allylated dearomatization products in 50%-81%yields.This novel protocol exhibited good tolerance for various functional groups,such as ester,carbonyl,alkynyl and halides(F,Cl,and Br).The commercial availability of the catalyst,mild reaction conditions,and experimental simplicity are the features of this catalytic method.A convenient ligand free,acid mediated palladium-catalyzed isomerization of allylbenzenes into 2-alkenes(E)at room temperature in dichloromethane for a wide range of substrate scope is described in the fourth chapter.The results obtained suggest that acid is crucial in this isomerization.Pd(TFA)2 as catalyst in the presence of TsOH·H2O in DCM at room temperature under air for 12 hours were selected as standard conditions for exploring the scope of reaction.Allylbenzenes containing electron-donating groups and electron-withdrawing groups were tolerated equally under the optimized condition,and ?-methylstyrenes products were obtained in the range of 65%-90%yields.