Studies On Diazo Compounds In Transition Metal-Catalyzed Coupling Reactions

The thesis aims at the studies on diazo compounds in palladium-catalyzed decarboxylative coupling and copper-catalyzed reductive coupling (Csp3-P) reactions. It mainly consists of the following four chapters:Chapterl.In part1, transition-metal-catalyzed coupling reactions of diazo compounds were summarized in detail. The migratory insertion of metal carbene is found to be general in terms of the migratory groups, which include benzyl, aryl, vinyl, allyl, acyl, alkynyl, and cyclopropyl. In addition, transition-metal-catalyzed X-H (X=C, N, O, S or Si) bond insertions via a metal carbene intermediate in situ generated from diazo compounds represent one of the most efficient approaches for the construction of C-X bonds. The mechanistic studies on diazo compounds in transition-metal-catalyzed reaction and their application in organic synthesis were also surveyed.In part2, transition-metal-catalyzed decarboxylative couplings were summarized in detail. Depending on the species of the caiboxylic acid compound, the decarboxylative couplings foll into two categories:1) Transition-metal-catalyzed decarboxylative couplings of caiboxylic acid were recognized as a new strategy for the construction of C-C (Csp2-Csp2, Csp2-Csp, Csp2-Csp3, and Csp-Csp) and C-X (C-O, C-N, C-S, C-P) bond;2) Transition metal-catalyzed decarboxylative allylation and benzylation reactions of carboxylic ester were also presented.Chapter2.In chapter2, we have discovered that propargylic carbonates react with N-tosylhydrazones under palladium-catalyzed conditions through a direct propargylic substitution. This is the unusual example where the nucleophilic substitution at the propargylic position is not an allenyl moiety. Furthermore, a novel palladium-catalyzed coupling of propargylic carbonates with N-tosylhydrazones to prepare multisubstituted vinylallenes is also developed. This diverse process allows the conversion of simple propargylic carbonates and N-tosylhydrazones to propargyl N-sulfonylhydrazones or multisubstituted vinylallenes depending on the proper choice of catalytic system. Chapter3.In chapter3, we have developed a new method for the formation of two different C-C bonds at the same carbon atom in a single reaction involving palladium-catalyzed decarboxylation and migratory insertion process. This reaction provides a novel method for the generation of all-carbon quaternary centers. Furthermore, a palladium-catalyzed coupling of aromatic and benzyl ic acid derivatives with a-diazocarbonyl compounds to prepare aromatic and benzylic ester derivatives with an O-substituted quaternary carbon center in moderate to excellent yields is also developed. The new approach is complementary to the previous methods for the construction of quaternary carbon centers. The reaction involves the use of starting materials that are readily available and stable, and is operationally simple.Chapter4..In chapter4, we have developed a new strategy for the formation of Csp3-P using N-tosylhydrazones as new alkyl reagents, which are easily prepared from commercially available ketones and aldehydes. The protocol is very simple and effective for the synthesis of phosphine oxide derivatives with moderate to good yields. In addition, this reaction involves an unexploited copper-catalyzed P-H insertion process. The scope and functional-group tolerance of the reaction are also wide.