2.7. Hydroxylation Reactions of Allenes 3282 2.8. Hydroamination Reactions of Allenes 3284 2.9. Hydrothiolation of Allenes 3284 2.10. Hydroalxoxylation of Alkenes and 1,3-Dienes 3286 2.11. Hydroamination of Alkenes and 1,3-Dienes 3287 2.12. Hydrothiolation of Conjugated Olefins 3289 3. Activation of Carbonyl/Imine Groups and Alcohols 3289 3.1. Condensation Reactions 3289 3.2. Addition Reactions 3291 3.3. Aldol Reactions 3294 3.4. Hydroand Carbosilylation Reactions 3295 3.5. Nucleophilic Substitution Reactions of Alcohols 3297 4. Gold-Catalyzed C-H Bond Functionalization 3297 4.1. Csp3-H Bond Functionalization 3298 4.2. Csp2-H Bond Functionalization 3299 4.3. Csp-H Bond Functionalization 3304 5. Gold-Catalyzed Selective Reductions 3305 5.1. Catalytic Hydrogenation of Alkenes 3306 5.2. Selective Reductions of R, -Unsaturated Carbonyl Groups and 1,3-Dienes 3306

Alternative synthetic methods through new developments in catalysis by gold.

For a long time multi-component syntheses of heterocycles have undeniably been a domain of classical carbonyl condensation chemistry. However, the advent of transition-metal catalysis not only has fertilized strategies in heterocyclic synthesis by uni- and bimolecular transformations but the past decade has also witnessed a rapid development of transition-metal catalysis in new multi-component reactions (MCR). Expectedly, palladium catalyzed processes have received a dominant position, yet, other transition-metal complexes are catching up implying organometallic elementary steps that reach even further than cross-coupling and carbometallation. Besides domino MCRs that are purely based upon organometallic catalysis the sequential and consecutive combination with condensation, addition and cycloaddition steps opens a vast playground for the invention of new sequences in heterocyclic synthesis. This tutorial review outlines the underlying reaction based principles of transition-metal catalysis in multi-component syntheses of heterocycles, summarizes recent developments of palladium catalyzed MCR, and highlights the more recent contributions to MCR based heterocyclic synthesis by virtue of rhodium, ruthenium, and copper catalysis.

Multi-component syntheses of heterocycles by transition-metal catalysis

Advances in the chemistry of tetrahydroquinolines.

Nucleophilic ring opening of aziridines

Chemical and biochemical transformations in ionic liquids

Aziridines react smoothly with arenes in the presence of a catalytic amount of indium triflate at ambient temperature to afford the corresponding β-aryl amine derivatives in excellent yields with high regioselectivity.

First Examples of C-Arylation of Aziridines Catalyzed by Indium Triflate.

The synthesis includes the Crimmins protocol for the non-Evans anti-aldol reaction of aldehyde (II), a stereoselective Grignard reaction, and Grubbs′ ring-closing metathesis as the key steps.

A Stereoselective Aldol Approach for the Total Synthesis of Herbarumin I (VIIIb) and Stagonolide A (IX).

An efficient conversion of β-diketones into corresponding β-keto enol ethers with catalytic amount of PMA-SiO 2 has been achieved.

PMA‐SiO2 Catalyzed Synthesis of β‐Keto Enol Ethers.

β-Enamino derivatives have been synthesized by the condensation of amines and β-dicarbonyl compounds in the presence of 1 mol% of phosphomolybdic acid (PMA) at room temperature in good to excellent yields.

Phosphomolybdic Acid (PMA) Catalyzed Highly Efficient and Rapid Synthesis of β-Enaminones.

Pyrrole and its derivatives react smoothly with acid chlorides and sulfonyl chlorides in the presence of zinc metal in toluene at ambient temperature to afford the corresponding 2-acetyl and 2-sulfonyl pyrrole derivatives in high yields with high regioselectivity.

R. Srinivasa Rao

Papers

First Examples of C-Arylation of Aziridines Catalyzed by Indium Triflate.

A Stereoselective Aldol Approach for the Total Synthesis of Herbarumin I (VIIIb) and Stagonolide A (IX).

PMA‐SiO2 Catalyzed Synthesis of β‐Keto Enol Ethers.

Phosphomolybdic Acid (PMA) Catalyzed Highly Efficient and Rapid Synthesis of β-Enaminones.

Zinc-Mediated Acylation and Sulfonation of Pyrrole and Its Derivatives.