This critical review examines transition metal-catalyzed decarboxylative couplings that have emerged within recent years as a powerful strategy to form carbon–carbon or carbon–heteroatom bonds starting from carboxylic acids. In these reactions, C–C bonds to carboxylate groups are cleaved, and in their place, new carbon–carbon bonds are formed. Decarboxylative cross-couplings constitute advantageous alternatives to traditional cross-coupling or addition reactions involving preformed organometallic reagents. Decarboxylative reaction variants are also known for Heck reactions, direct arylation processes, and carbon–heteroatom bond forming reactions.

Decarboxylative coupling reactions: a modern strategy for C–C-bond formation

The borrowing hydrogen (BH) principle, also called hydrogen auto-transfer, is a powerful approach which combines transfer hydrogenation (avoiding the direct use of molecular hydrogen) with one or more intermediate reactions to synthesize more complex molecules without the need for tedious separation or isolation processes. The strategy which usually relies on three steps, (i) dehydrogenation, (ii) intermediate reaction, and (iii) hydrogenation, is an excellent and well-recognized process from the synthetic, economic, and environmental point of view. In this context, the objective of the present review is to give a global overview on the topic starting from those contributions published prior to the emergence of the BH concept to the most recent and current research under the term of BH catalysis. Two main subareas of the topic (homogeneous and heterogeneous catalysis) have been identified, from which three subheadings based on the source of the electrophile (alkanes, alcohols, and amines) have been consid...

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Advances in One-Pot Synthesis through Borrowing Hydrogen Catalysis

In this Minireview, the synthesis of amines by the amination of alcohols, by means of the so-called borrowing hydrogen methodology, is presented Compared to other synthetic methodologies for the synthesis of amines, these transformations are highly attractive because often alcohols are readily available starting materials, some of them on a large scale from renewable sources In addition, the amination of alcohols produces water as the only by-product, which makes the process potentially environmentally benign Already today, lower alkyl amines are produced in bulk by the chemical industry with this synthetic method In particular, the recent progress applying organometallic catalysts based on iridium, ruthenium, and other metals will be discussed Notable recent achievements include the conversion of challenging substrates such as diols, the development of recyclable catalysts, milder reaction temperatures, and the direct alkylation of ammonia or its equivalents with alcohols

The Catalytic Amination of Alcohols

Transition metal-catalyzed substitution of alcohols by N-nucleophiles (or N-alkylation of amines and related compounds with alcohols) avoids the use of alkylating agents by means of borrowing hydrogen (BH) activation of the alcohol substrates. Water is produced as the only by-product, which makes the “BH” processes atom-economic and environmentally benign. Diverse types of homogeneous organometallic and heterogeneous transition metal catalysts, and substrates such as N-nucleophiles including amines, amides, sulfonamides and ammonia, and various alcohols, can be used for this purpose, demonstrating the promising potential of “BH” processes to replace the procedures using traditional alkylating agents in pharmaceutical and chemical industries. Borrowing hydrogen activation of alcohols for C–N bond formation has recently been paid more and more attention, and a lot of new and novel procedures and examples have been documented. This critical review summarizes the recent advances in “BH” substitution of alcohols by N-nucleophiles since 2009. “Semi-BH” N-alkylation processes with or without an external hydrogen acceptor are also briefly presented. Suitable discussion of the “BH” strategy provides new principles for establishing green processes to replace the relevant traditional synthetic methods for C–N bond formation.

Substitution of alcohols by N-nucleophiles via transition metal-catalyzed dehydrogenation

Organosulfur compounds have long played a vital role in organic chemistry and in the development of novel chemical structures and architectures. Prominent among these organosulfur compounds are those involving a sulfur(IV) center, which have been the subject of countless investigations over more than a hundred years. In addition to a long list of textbook sulfur-based reactions, there has been a sustained interest in the chemistry of organosulfur(IV) compounds in recent years. Of particular interest within organosulfur chemistry is the ease with which the synthetic chemist can effect a wide range of transformations through either bond formation or bond cleavage at sulfur. This review aims to cover the developments of the past decade in the chemistry of organic sulfur(IV) molecules and provide insight into both the wide range of reactions which critically rely on this versatile element and the diverse scaffolds that can thereby be synthesized.

Bond-Forming and -Breaking Reactions at Sulfur(IV): Sulfoxides, Sulfonium Salts, Sulfur Ylides, and Sulfinate Salts.

Pd-catalyzed desulfitative Heck coupling with dioxygen as the terminal oxidant.

An efficient method was developed for the desulfitative arylation of indoles with sodium sulfinates using palladium as catalyst and copper chloride dihydrate as oxidant. The direct arylation occurred exclusively in the C-2 position of indoles and proceeded well for a range of different substrates.

Palladium‐Catalyzed Direct and Site‐Selective Desulfitative Arylation of Indoles with Sodium Sulfinates

A highly selective palladium bis(acetoacetonate)/copper(I) chloride [Pd(acac)2/CuCl] catalytic system for the preparation of dibenzopyranones has been developed. Tandem decarboxylative coupling and lactonization can be realized in one pot using commercially available starting materials. The reaction proceeded well for a range of different substrates.

Jiaying Luo

Papers

Pd-catalyzed desulfitative Heck coupling with dioxygen as the terminal oxidant.

Palladium‐Catalyzed Direct and Site‐Selective Desulfitative Arylation of Indoles with Sodium Sulfinates

Efficient One‐Pot Synthesis of Dibenzopyranones via a Decarboxylative Cross‐Coupling and Lactonization Sequence

Palladium-catalyzed desulfitative addition of sodium sulfinates with α,β-unsaturated carbonyl compounds

Ruthenium-catalyzed direct amination of alcohols with tertiary amines