Studies Of Transition-Metal-Catalyzed Construction Of Carbon-Carbon And Carbon-Hetero Bond

Alkynes are widely distributed in a vast array of natural products, bioactive compounds and drugs, as well as being ubiquitous units in material science, but also one of the most exciting research topics in organic chemistry and have been paid sustained attention. Transition-metal-catalyzed organic reactions involving alkynes have recently aroused considerable interest because of the reactivity of alkynes have been greatly enhanced in the presence of transition metals thus broaden the research scopes of alkynes in organic synthesis. In the presenting dissertation, we investigated a variety of transition-metal-catalyzed coupling reactions involving terminal alkynes, which include:1. Copper-Catalyzed Coupling Reaction of C-OMe Bonds Adjacent to a Nitrogen Atom with Terminal AlkynesWe have developed a CuBr/dppp-catalyzed process for the cross-coupling of N,N-dimethylformamide dimethyl acetalthe with terminal alkynes. The simple and efficient catalytic system worked well with a broad range of terminal alkynes and allowed the facile synthesis of symmetrical and unsymmetrical 3-amino-1,4-diynes in moderate to good yield. It was found that 3-amino-1,4-diynes were interesting building blocks in the straightforward synthesis of various useful molecules such as (E)-1,5-diarylpent-1-en-4-yn-3-ones and 1,5-Diphenylpent-2-en-4-ynylimine. Notably, the as prepared 3-amino-1,4-diynes can be used as a Michael donor to addition toward the electron-deficient triple bonds to give the Michael adducts. Compared to the reported methods, the starting materials are commercially available or readily prepared, the reaction is easy to handle and avoid using organometallic reagents.2. Copper-Catalyzed Three-component Reactions of Terminal Alkynes, Sulfonyl Azides and N,N-Dialkyloxyformamide Dialkyl AcetalsA facile synthesis of regioselectiveα,β-unsaturated sulfonyl amidines via CuBr-Catalyzed multicomponent reaction of terminal alkynes, sulfonyl azides, and N,N-dialkyloxyformamide dialkyl acetals have been successfully developed. Various terminal alkynes, sulfonyl azides and N,N-dialkyloxyformamide dialkyl acetals were employed to extend the scope of the reaction substrates under the standard reaction conditions and afforded the corresponding products in good to excellent yield. Phosphoryl azides also tolerated in this reaction system and provided an alternative method for the synthesis of unsaturated phosphoryl amidine compounds. A plausible mechanism has been postulated. The starting materials used are commercially available or readily prepared, the procedure is mild and easy to handle, and could be broadly utilized in the highly efficient preparation of unsaturated amidine compounds.3. Iron-Catalyzed Coupling Reaction of Alkynyl Bromides with N-NucleophilesWe have developed an efficient and convenient method for the preparation of ynamides by FeCl3·6H2O-catalyzed coupling reaction of alkynyl bromides and N-nucleophiles. Various nitrogen nucleophiles such as oxazolidinones, sulfonamides, pyrrolidin-2-one. electronic-poor indoles and a variety of substituted alkynyl bromides were tolerated in this catalyst system and afforded the corresponding ynamides in good to excellent yield. Furthermore, the reusability of iron catalyst was tested in the coupling reaction. The catalytic system showed high efficiency of reusability and could be recycled nine times only with a small decrease in efficiency. Compared to the reported copper-catalyzed system, the reactions did not require the protection of inert gases and no Glaser coupling side-products were detected, the catalyst is cheap, environmentally benign and reusable. This work has been highlighted by SynFacts and Organic Chemistry Portal.4. Ni-Catalyzed Intramolecular Cycloaddition of Methylenecyclopropanes to Alkvnes We have developed a new nickel-catalyzed intramolecular cycloaddition of methylenecyclopropanes with arylalkynes for the preparation of cyclopenta[a]indenes. The cyclization precursor,1-(2-(2-(cyclopropylidenemethyl)phenyl)ethynyl)benzene, which is easily assembled by Sonogashira coupling and a subsequent Wittig reaction. The structure of the product was further confirmed by X-ray single-crystal diffraction. A kind of mechanism containing the cleavage of proximal C-C bond of MCPs has been postulated. The procedure is atom-economical and a variety of functional groups substituted substrates such as chlorine and fluorine could be tolerated in this reaction, substrate derived from 2-bromopyridine-3-carbaldehyde also tolerated and provided an alternative route for fused heterocyclic molecules. The procedure provided a general and efficient method for the synthesis of cyclopenta[a]indenes.5. Sulfonylation of Arenes with Sulfonamides Activated by Triflic AnhydrideWe have described an unusual process of arenes with sulfonamides to produce arylsulfones in the presence of triflic anhydride. Substrates such as chlorobenzene, bromobenzene, iodobenzene and 2-thiophenyl sulfonylamide tolerated well in this reaction system and provided the corresponding sulfones in good yields. Activated arenes such as anisole and toluene afforded the corresponding sulfones in good yields, and isomers were observed. The stability of sulfonamides to air and moisture requires no special caution to handle and is amenable to long-term storage. In these aspects sulfonamides have a clear advantage as the sulfonylation substrates over the sulfonchlorides and sulfonanhydrides. The transformation is a useful alternative to the commonly accepted sulfonylation procedures.