Kilian Muñiz

High‐Oxidation‐State Palladium Catalysis: New Reactivity for Organic Synthesis

Recent years have seen the rapid development of a new field of palladium catalysis in organic synthesis. This chemistry takes place outside the usually encountered Pd(0)/Pd(II) cycles. It is characterized by the presence of strong oxidants, which prevent further palladium(II)-promoted reactions at a given point of the catalytic cycle by selective metal oxidation. The resulting higher-oxidation-state palladium complexes have been used to develop a series of new synthetic transformations that cannnot be realized within conventional palladium catalysis. This type of catalysis by palladium in a higher oxidation state is of significant synthetic potential.

Intramolecular aminopalladation of alkenes as a key step to pyrrolidines and related heterocycles

Palladium catalysis for the intramolecular amination of alkenes is a powerful approach in heterocycle synthesis. The initial common step in this approach consists of an aminopalladation reaction. This tutorial review describes the synthesis of 2-amino alkyl-palladium compounds and renders special attention on the subsequent manipulation of the alkyl-palladium group. By carefully choosing the appropriate conditions, a wide variety of different heterocyclic structures are accessible which arise from reactions such as hydroamination, aza-Heck coupling, aminocarbonylation or oxidative processes such as aza-Wacker reaction and 1,2-difunctionalization.

Catalyzed Asymmetric Arylation Reactions

Addition and substitution reactions with carbon nucleophiles are fundamental processes in organic synthesis, and the development of general catalytic asymmetric variants thereof is still a major challenge today. In contrast to enantioselective alkyl transfer reactions, the corresponding arylations have not yet reached a high level of maturity. The existing protocols are either of no general applicability or are limited in terms of selectivity. This article summarizes established routes for catalytic asymmetric aryl transfer together with the latest developments in this area. The scope and limitations of this reaction are discussed.

Imido-osmium(VIII) compounds in organic synthesis: aminohydroxylation and diamination reactions.

Imido complexes of osmium tetroxide are versatile compounds for olefin functionalisation. This tutorial review offers a brief historical overview on these compounds and discusses the electronic properties and reactivities of isolated imido osmium compounds in what had been the original stoichiometric aminohydroxylation reaction. The recently emerging catalytic Sharpless aminohydroxylation is discussed with special emphasis on mechanistic details. The final section deals with diamination of olefins, which relies on the chemistry of bisimido and trisimido osmium complexes.

Vicinal Difunctionalization of Alkenes with Iodine(III) Reagents and Catalysts

Hypervalent iodine(III) reagents have been known for over a century, and their reaction profile is still actively investigated. Recent years have seen impressive improvements in the area of alkene difunctionalization reactions, where new methodologies have become available. Especially chiral non-racemic hypervalent iodine(III) reagents and catalysts have emerged as versatile tools for the realization of important enantioselective transformations.

An intermolecular palladium-catalyzed diamination of unactivated alkenes.

(b) Reaction with 2 equivalents of saccharin. (c) n.d. = not determined, less than 5 % conversion. (d) Enamide product. (e) In the presence of 2 equivalents of NaOAc. (f) Yield of isolated product in parentheses. (g) Reaction at room temperature. (h) With 5 mol % catalyst. Tos = tolu- ene-4-sulfonyl.

Oxidative Interception of the Hydroamination Pathway: A Gold‐Catalyzed Diamination of Alkenes

A complimentary diamination of alkenes by using homogeneous gold catalysts is described. The reaction is one of very few examples of homogeneous gold oxidation catalysis and proceeds with high selectivity under mild conditions. Individual steps of the suggested catalytic cycle were investigated on isolated model gold complexes, and new pathways for gold-catalyzed amination reactions were established. The key step is an intramolecular alkyl-nitrogen bond formation from a gold(III) intermediate. This process validates the concept of reductive elimination from high oxidation catalyst states for this type of C-N bond forming reactions.

Direct synthesis of bicyclic guanidines through unprecedented palladium(ii) catalysed diamination with copper chloride as oxidant.

Palladium catalysed intramolecular guanidine transfer to alkenes can be accomplished with copper chloride as the oxidant to give bicyclic guanidines with complete selectivity and in high yields.

Iodine(III)-mediated intermolecular allylic amination under metal-free conditions.

A new approach to direct intermolecular allylic amination has been developed using metal-free conditions at room temperature. The reaction employs a hypervalent iodine(III) reagent as an oxidant and bistosylimide as a nitrogen source. A series of different allylic aminations are presented with up to a 99% yield. Mechanistic studies including isotope labeling and Hammett correlation suggest that depending on the substrate structure two different mechanisms can be operating.

Planar chiral arene chromium(0) complexes: potential ligands for asymmetric catalysis

Planar chiral (η6-arene) tricarbonyl chromium(0) complexes are well-studied compounds in synthetic organic chemistry. However, the number of investigations concerned with their application in asymmetric catalysis is rather low. This review aims to summarise the main approaches toward the stereoselective synthesis of planar chiral derivatives of (η6-benzene) tricarbonyl chromium(0) and to present recent applications of such complexes as ligands in enantioselective catalytic processes.