Richard F. Heck
Bio: Richard F. Heck is an academic researcher from University of Delaware. The author has contributed to research in topic(s): Palladium & Aryl. The author has an hindex of 43, co-authored 95 publication(s) receiving 8431 citation(s).
Richard F. Heck1•Institutions (1)
Abstract: The palladium-catalyzed vinylation of organic halides provides a very convenient method for forming carboncarbon bonds at unsubstituted vinylic positions. Generally the reaction does not require anhydrous or anaerobic conditions although it is advisable to limit access of oxygen when arylphosphines are used as a component of the catalyst. The transformation is valuable because it cannot be carried out in a single step by any other known method (except in certain Meerwein reactions). The organic halide employed is limited to aryl, heterocyclic, benzyl, or vinyl types, with bromides and iodides seen most often. Halides with an easily eliminated beta-hydrogen atom (i.e., alkyl derivatives) cannot be used since they form only olefins by elimination under the normal reaction conditions. The base needed may be a secondary or tertiary amine, sodium or potassium acetate, carbonate, or bicarbonate. When nucleophilic secondary amines are used as coreactants with most vinylic halides, a variation occurs that often produces tertiary allylic amines as major products. The catalyst is commonly palladium acetate, although palladium chloride or preformed triarylphosphine palladium complexes, as well as palladium on charcoal, have been used. A reactant, product, or solvent may serve as the ligand in reactions involving organic iodides, but generally a triarylphosphine or a secondary amine is required when organic bromides are used. The reaction, which occurs between ca. 50° and 160° proceeds homogeneously. Solvents such as acetonitrile, dimethylformamide, hexamethylphosphoramide, N-methylpyrrolidinone, and methanol have been used, but are often not necessary. The procedure is applicable to a very wide range of reactants and yields are generally good to excellent. Several variations of the reaction are known in which the organic halide is replaced by other reagents such as organometallics, diazonium salts, or aromatic hydrocarbons. These reactions are not discussed in detail, but are only briefly compared with the halide reaction. Other related reactions such as the palladium-catalyzed replacement of allylic substituents with carbanionic reagents, the palladium-promoted nucleophilic substitutions at olefinic carbons, and the numerous palladium-catalyzed coupling reactions of halides and organometallics are also beyond the scope of this review. The palladium-catalyzed vinylic substitution reaction has not yet received much attention from organic chemists, but its broad scope and simplicity demonstrate that it is a useful method for the synthesis of a variety of olefinic compounds. Keywords: palladium catalyst; vinylation; organic halides; scope; limitations; experimental procedures; vinylic substitution; ethylene; acrylic acid; butenol; methyl acrylate; styrene; pentadiene; acrolein dimethyl acetal; olefins
01 Jan 2022
••01 Jan 2022
Abstract: Utilizing CuxO nanoparticles supported on carbon nanotube as catalyst, visible-light could efficiently transform Glaser homo-coupling into Sonogashira cross-coupling. The isolated Sonogashira product yield is up to 0.58 mmol (sel. 97%) under visible-light irradiation while the Glaser product achieves 0.45 mmol (sel. 92%) in the dark for phenylacetylene and iodobenzene. We also discover that the active species under light irradiation is different from that in the dark. The visible light-driven adsorption of aromatic iodides on CuxO nanoparticles and light-excited copper(I) phenylacetylide intermediates together enables the high selectivity of Sonogashira product. The synergistic effect between Cu(II) and Cu(I) acetylide dimer complex enhances the Glaser product yield in the dark.
01 Jan 2022
Abstract: A series of 4-exo-dig cyclocarbopalladations has been efficiently used to produce molecular complexity in a straightforward manner. Strained 1,2-cyclobutanediols are rapidly obtained, usually under microwave irradiation, in high yields. In many cases, the cyclocarbopalladation cascade reaction is associated with 6π- or 8π-electrocyclic reactions. Polycyclic skeletons of unnatural or natural products can be prepared in a few steps from simple starting materials. Very strained aromatic polycycles, the taxane framework, cyclooctatrienes, cyclooctatetraenes, fenestranes, and fenestrenes have been obtained using this methodology.
••01 Jan 2022
Abstract: The tetrapetalones were pursued for well over a decade by numerous research groups. Herein, we detail our motivations and findings, which we imagine are very different from the many others who tackled this extremely challenging problem. In this chapter, we explain how our many failures caused us to revise our strategy eight times. Although we failed to reach the genuine natural product, we hope the reader will conclude that we nevertheless developed several valuable methods and that we gained important strategic insights from our trials and tribulations. At the very least, we can emphatically state that we developed a great appreciation of the wonderful ways in which our chemistry community is interconnected, and the great benefit we all enjoy from one another's achievements.
Author's H-index: 43