Studies On Transition-metal Catalyzed Diazo Compounds Involved Organic Reactions

Diazo compounds have already been widely employed for more than100years, while diazo chemistry has also been broadenly investigated in organictransformations. Generally, diazo compounds can be prepared in a very safeand easy way. In addition, α-diazocarbonyl compounds can give the formationof Fisher-type metal carbenes in the presence of transition metal complex.Subsequently, these active intermediates can undergo cyclopropanation, X-Hinsertion reactions as well as novel cross-coupling reactions andmulticomponent reactions. The first part of this dissertation is the overallintroduction to the above-mentioned contents.In the second section, we have described an excellent regioselective andenantioselective Darzens reaction between aldehydes and diazoacetamidescatalyzed by a chiral titanium complex formed in situ from (+)-pinanediol andTi(OiPr)4. Under the optimized reaction conditions, the cis-epoxides wereobtained in high isolated yields (up to92%) with excellent ee values (up to>99%).Metal catalyzed X-H bond insertion of diazo compounds is one mostimportant approach to construct C-X bonds (X=C, N, O etc). Althoughrhodium and copper complexes have been widely utilized, the X-H bondinsertions of diazo compounds catalyzed by palladium complexes have notbeen reported till now. So the third part of this dissertation mainly focused onthe development of Pd-catalyzed N-H bond insertion between diazo esters andanilines. Under the optimized reaction conditions, the insertion products wereobtained in74-93%isolated yields. Moreover, upon using a suitable chiralauxiliary, the chiral α-phenyl-amino esters were obtained in high yields andwith excellent diastereoselectivities. This is the first example ofpalladium-catalyzed X-H insertion of diazo compounds and will furtherbroaden the utilization of Pd-carbene in diazo involved transformations.C2-(carboxylate methyl) substituted indoles have been found in manybiologically natural products. Also, α-diazo compounds have been used asuseful precursors to access a variety of heterocycles. The fourth part hasdemonstrated the discovery of copper-catalyzed annulations between α-aryl orbenzyl diazoacetates and2-ethynylanilines. As a result, C2-functionalized indoles have been synthesized in45-88%isolated yields under relatively mildreaction conditions.In the last part of this dissertation, we have described a Pd-catalyzedcarbenoid based N-H bond insertions of ortho-triflateanilines withvinyldiazoacetates. This one-pot strategy featured a cascade procedure in thecombination of N-H insertion with base-promoted cyclization to afford thelactones in one step.