Abstract
The thesis delineates the palladium catalyzed addition reactions of electrophiles and nucleophiles into carbon-carbon multiple bonds. This thesis is divided into four chapters. First chapter explains the synthesis of 1,7-enyne derivatives, the second chapter describes synthesis of 1,6-enynes, 1,6-enallenes and 1,6-dienes, the third chapter deals with the synthesis of substituted 2-arylallylgermanes, cyclicallylgermanes and cyclicallylsilanes and chapter 4 explains (E)-vinylicsilanes having allylstannanes in brief way. Chapter 1 describes palladium catalyzed propargylallylation reactions of activated olefins. The three component addition reaction of allylic chlorides and allenylstannaes with activated olefins in the presence of palladium catalyst affords 1,7-enyne derivatives with high regio-, stereo and chemoselectivity in good to excellent yields. The reaction proceeds with various substituted activated olefins. Furthermore, the reaction was successfully extended to an activated dienes. A plausible mechanism based on □1-allenyl □3-allyl palladium intermediate is proposed to account for the catalytic three-component reaction. Chapter 2 demonstrates the addition reactions of allylalkynyl, allylallenyl and allylalkenyl to benzynes in the presence of palladium catalyst. The reactions of allylic chlorides and alkynylstannanes into benzynes in the presence of palladium catalyst gave various 1-allyl-2-alkynylbenzenes in excellent yield. The reaction proceeds with various substituted benzyne precursors, allylic chlorides and alkynyl, allenyl and alkenylstannanes. This method allows an efficient synthesis of various 1-allyl-2-alkynylbenzenes, 1-allyl-2-allenylbenzenes and 1-allyl-2-alkenylbenzenes in good to excellent yields. Furthermore, the utility of 1-allyl-2-alkynylbenzenes in organic synthesis were successfully demonstrated with the synthesis of multiple rings. A possible mechanism for the present catalytic reaction is proposed. Chapter 3 describes the synthesis of substituted 2-arylallylgermanes in a highly regio-, stereo- and chemoselective fashion involving a three-component assembly of allenes, aryl iodides and stannylgermane catalyzed by phosphine-free palladium complexes. The present catalytic reaction is highly regioselective in which aryl group and metal add to the middle and unsubstituted terminal carbon of the allene moiety, respectively. In addition, the reaction is highly stereoselective to give Z-isomer as an exclusive product. Furthermore, the catalytic reaction was successfully extended into partially intermolecular version to give cyclic metal reagents with excellent yields. The high chemoselectivity of the present reaction is due to a favorable SE2 cyclic pathway involved in transemetalation step. The mechanism involving a face-selective coordination of allenes is proposed to account for the high stereoselectivity. Chapter 4 explains a highly regio- and stereoselective silylstannation of allenes using phosphine free palladium complexes. The addition reaction of trimethy(tributylstannyl)silane with allenes in the presence of phosphine-free palladium catalyst provided (E)-vinylicsilane having allylstannane moieties in excellent yield. The vinylic silanes and allyl stannanes present in these products allow for a large variety of chemical modifications. The nature of the ligand on the palladium complexes has a tremendous influence on the regio- and stereochemistry of present reactions.