Co-operative effect of Lewis acids with transition metals for organic synthesis

Abstract

Transition metal-mediated or -catalyzed carbon-carbon bond or carbon-heteroatom bond forming reactions are among the most powerful tools in organic synthesis. In addition, Lewis acid-mediated or -catalyzed organic transformations are widely used. In this context, an effective combination of these two powerful protocols or an efficient cooperation of transition metals with Lewis acids should open a new era in synthetic chemistry. This tutorial review summarizes representative synthetic methodologies developed in the past decades employing this co-operative effect.

Betti Reaction of Cyclic Imines with Naphthols and Phenols – Preparation of New Derivatives of Betti's Bases

“…Usually this type of reactions takes place in the presence of catalysts such as transition metal complexes, for example palladium, [1,2] nickel, [2] or copper salts, [3] Lewis acids, [4] or a combination of them. [5] Among others, the reaction between 2-naphthol and a N-phenyltetraisoquinoline to form an aminoalkylnaphthol was studied by Li et al [6] This approach requires the use of Cu I salts, and the reaction is not selective, affording a relevant amount of BINOL as byproduct too. Subsequent studies of this group [7] show that analogues of this aminoalkylnaphthol can be obtained through an aza-FriedelCrafts reaction, an approach that allows the preparation of these Betti base derivatives [8] in good yields, without metal catalysts and with 100 % atom economy.…”

Oxide‐Bridged Heterobimetallic Aluminum/Zirconium Catalysts for Ethylene Polymerization

“…[1][2][3][4][5][6] Cooperation of two neighboring metals enables attractive new reactivities or physical properties. [7][8][9] Homogeneous olefin polymerization by metallocenes is an interesting playground for such heterobimetallic catalysts: Cp 2 MCl 2 (Cp = C 5 H 5 ; M = Ti, Zr, Hf) type precatalysts are usually activated by a cocatalyst that is generally a compound containing a Lewis acidic boron or aluminum center. [10][11][12] Owing to its capability to fulfil multiple functions, methylalumoxane (MAO) is the most widely used cocatalyst (Scheme 1).…”

p‐Toluenesulfonylmethyl Isocyanide (TosMIC) and Indium Manifold Strategy to Access β‐Keto‐(E)‐enamino Esters from 1,3‐Dicarbonyl Compounds

“…However, when ethyl 4,4-dimethyl-3-oxopentanoate 7 was the test substrate, an unusual product 16 resembling the selfcoupling of TosMIC resulted. It is pertinent to mention that the self-condensation did not occur in the absence of 7 or even in the presence of other carbonyl compounds (1)(2)(3)(4)(5). From this result, one can conclude that the normal C À C coupling reaction was less feasible when a sterically crowded compound like 7 was the substrate.…”

“…[2b] Similarly, owing to the ability of metal complex formation with p-bonds, [3] nucleophilic attack maybe accomplished for the same enol to generate C À C bond formation. [4] The reactivity of a metal-complexed isonitrile bearing an active methylene group is different from that of a metal-ligated isonitrile without an active methylene group.…”