Asymmetric enamine catalysis.

A wide array of forms of palladium has been utilized as precatalysts for Heck and Suzuki coupling reactions over the last 15 years. Historically, nearly every form of palladium used has been described as the active catalytic species. However, recent research has begun to shed light on the in situ transformations that many palladium precatalysts undergo during and before the catalytic reaction, and there are now many suggestions in the literature that narrow the scope of types of palladium that may be considered true “catalysts” in these coupling reactions. In this work, for each type of precatalyst, the recent literature is summarized and the type(s) of palladium that are proposed to be truly active are enumerated. All forms of palladium, including discrete soluble palladium complexes, solid-supported metal ligand complexes, supported palladium nano- and macroparticles, soluble palladium nanoparticles, soluble ligand-free palladium, and palladium-exchanged oxides are considered and reviewed here. A considerable focus is placed on solid precatalysts and on evidence for and against catalysis by solid surfaces vs. soluble species when starting with various precatalysts. The review closes with a critical overview of various control experiments or tests that have been used by authors to assess the homogeneity or heterogeneity of catalyst systems.

On the Nature of the Active Species in Palladium Catalyzed Mizoroki–Heck and Suzuki–Miyaura Couplings – Homogeneous or Heterogeneous Catalysis, A Critical Review

Green solvents for sustainable organic synthesis: state of the art

https://www.researchgate.net/file.PostFileLoader.html?id=53e9e550d3df3edb538b45ab&assetKey=AS%3A273579713728525%401442237896090

Polyethylene glycol and solutions of polyethylene glycol as green reaction media

http://www.rsc.org/suppdata/gc/c0/c0gc00797h/c0gc00797h.pdf

Ch. Narsihmulu

Papers

Poly(ethylene glycol) (PEG) as a reusable solvent medium for organic synthesis. Application in the Heck reaction.

Three component coupling catalyzed by TaCl5–SiO2: synthesis of α-amino phosphonates

Osmium tetroxide in poly(ethylene glycol)(PEG): a recyclable reaction medium for rapid asymmetric dihydroxylation under Sharpless conditions

l-Proline catalysed asymmetric aldol reactions in PEG-400 as recyclable medium and transfer aldol reactions

Asymmetric aldol reactions in poly(ethylene glycol) catalyzed by L-proline