Catalytic Transformation of Alkynes by Late Transition Metals and Double Heck Reaction by Palladium Complexes

Abstract

Part I. Catalytic Transformation of Alkynes by Late Transition Metals Chapter 1. The cycloisomerization reaction of N-allyl-2-(2'-arylethyne-2-yl)amides or allylic 2-alkynoates in the presence of cationic triphenylphosphinegold(I) produced bicyclo[3.2.0]hept-6-en-2-ones under mild conditions. Computational investigations with a density functional theory (DFT) revealed that a stepwise 6-endo-dig cyclization of 1,6-enyne systems, followed by a skeletal rearrangement to form bicyclo[3.2.0]hept-6-en-2-one species represents the most probable reaction pathway. Chapter 2. A silver(I)-catalyzed facile formation of pyrazoles from propargyl N-sulfonylhydrazones has been disclosed. During the reaction, a migration of sulfonyl groups (Ts, Ms) was observed. Good functional group compatibility was observed under mild reaction conditions (at room temperature for 3-5 h). This methodology allows for the efficient and regioselective synthesis of 1,3- and 1,5-disubstituted and 1,3,5-trisubstituted pyrazoles. Chapter 3. Applying microwave irradiation to palladium-catalyzed cyanothiolation of alkynes dramatically shortened the reaction time with good to excellent isolated yields. Keywords : Gold, Silver, Palladium, Alkyne, Cycloisomerization, Migration, Pyrazole, Regioselective, Cyanothiolation Part II. (NHC)Pd(allyl)Cl Complex-Catalyzed Double Heck Reaction: Diarylation of Acrylates We have studied double-Heck arylation of acrylate in the presence of (NHC)Pd(allyl)Cl catalysts (NHC = N-heterocyclic carbene). We confirmed that the double Heck arylation occurred by excess aryl halides after a mono-arylation had completely done. Double-Heck arylation of acrylate was highly dependent upon the substrate, the catalyst, the base, and the solvent. Keywords : Palladium, N-Heterocyclic carbine, Heck reaction, Arylation, Electron-withdrawing Group, Electron-donating Group, Imidazolium, Perimidinium