The thesis delineates the Palladium-, Copper-, and Platinum-Catalyzed Carbocyclization, Coupling and Addition Reactions. For better clarity, this thesis has been divided into eight chapters.
Chapter 1 explains the nature and history of benzynes. Also, a quantity of methods for generating benzynes and their applications in metal catalyzed reactions are denoted.
Chapter 2 demonstrates the carbocyclization reactions of aryl iodides, bicyclic alkenes and benzynes. These three components in the presence of palladium trifurylphosphine complex gave annulated 9,10-dihydrophenanthrene in good to excellent yields. The catalytic carbocyclization reaction shows interesting product regiochemistry. The carbocyclization products from oxabenzonorbornadiene can be further applied for the synthesis of highly substituted aromatic hydrocarbons via a deoxyaromatization reaction. A possible mechanism for the present catalytic reaction is proposed.
Chapter 3 portrays the synthesis of 1-allyl-2-alkynylbenzenes. The reaction of 2-trimethylsilylphenyl triflate with allyl acetates or halides and terminal alkyne provides three component assembling products in good to excellent yields. The catalytic reaction is compatible with various functional groups. A suitable mechanism is proposed for the reaction. These types of 1,6-Enynes are highly useful synthetic intermediates in various organic reactions.
Chapter 4 depicts the palladium catalyzed three-component coupling of benzyne with allylic electrophiles and trialkyl metal reagents as the transmetallating agent in the presence of Pd(dba)2/dppp affording 1-allyl-2-alkylbenzene derivatives in good to excellent yields. So far, the organometallic reagents employed as transmetallating agent are capable of coupling only sp and sp2 bonds to benzene moiety. Groups like alkene, alkyne, allene and aryl are coupled easily. But, sp3 bond generating organometallic reagents has not been used. We attempted sp3 bond generating reaction and succeeded in it.
Chapter 5 discusses about a highly regio- and chemoselective atom-economical three-component coupling of benzynes with allylic epoxides and terminal alkynes catalyzed by cooperative palladium and copper metals. In three-component sequential coupling reactions, several allylic electrophiles such as allylic acetates, carbonates and halides are successfully used. We intended to use allylic epoxide as electrophile and we succeeded in it. The three-component reaction proceeds in the presence of palladium complex alone. But it shows low regioselectivity. In presence of palladium complex and Cu(I) bimetal catalyst system regioselectivity of the product is greatly enhanced.
Chapter 6 elucidates the copper catalyzed reaction of benzynes with activated alkenes and terminal alkynes giving 1,2 disubstituted benzenes in good to excellent yields. The product formation can be explained by alkynylcupration of benzyne with cuprous acetylide giving 2-alkynylphenylcuprous reagent followed by 1,4-addition to activated alkenes. A variety of benzynes, terminal alkynes and activated alkenes including enone, acrylate, acetonitrle and viny sulphone are employed in this reaction.
Chapter 7 narrates a highly regioselective platinum-catalyzed multi-step reaction of indoles with alkynyl alcohols. The methodology offers a simple and mild method for the preparation of 3-substituted 5-membered tetrahydrofuran and 6-membered tetrahydro-2H-pyran indole derivatives. Ring closure of these alkynyl alcohols are highly regioselective. The catalytic reaction was examined with various substituted indoles and various substituted alkynyl alcohols. The results showed that indoles with electron-donating substituents were more reactive affording higher product yields than those with electron withdrawing groups. Mechanistically, the catalytic reaction proceeds via an intramolecular hydroalkoxylation of alkynyl alcohol affording cyclic enol ether followed by the addition of C-H bond of indole to the unsaturated moiety of cyclic enol ether providing the final product. Experimental evidences to support this proposed mechanism are provided.
Chapter 8 explains a platinum catalyzed multi-step reaction of N-heteroaromatics with propargyl alcohols. Indole derivatives having a 3-oxobutyl group at the 3-position are synthesized by this method. The platinum catalyst plays dual role in this reaction. It first catalyzes the transformation of propargyl alcohol into □,□-unsaturated ketone and then the addition of heteroaromatics to the □,□-unsaturated ketone in one pot. It is significant that C3-substituted indole derivatives show a variety of biological activities and are essential building blocks for the synthesis of biologically active compounds and natural products.

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