Synthesis of Naphthylpyridines from Unsymmetrical Naphthylheptadiynes and the Configurational Stability of the Biaryl Axis

Synthesis, stereochemical assignment, and enantioselective catalytic activity of late transition metal planar chiral complexes

Planar chirality is an important form of molecular chirality that can be utilized to induce enantioselectivity when incorporated into transition metal catalysts. However, due to synthetic constraints, the use of late transition metal planar chiral complexes to conduct enantioselective transformations has been limited. Additionally, the published methods surrounding the stereochemical assignment of planar chiral compounds are sometimes conflicting, making proper assignment difficult. This review aims to provide clarity on the methods available to assign planar chirality and provide an overview on the synthesis and use of late transition metal planar chiral complexes as enantioselective catalysts.

Dynamic Kinetic Resolution of 2-(Quinolin-8-yl)Benzaldehydes: Atroposelective Iridium-Catalyzed Transfer Hydrogenative Allylation

An atroposelective Ir-catalyzed dynamic kinetic resolution (DKR) of 2-(quinolin-8-yl)benzaldehydes/1-naphthaldehydes by transfer hydrogenative coupling of allyl acetate is disclosed. The allylation reaction takes place with simultaneous installation of central and axial chirality, reaching high diastereoselectivities and excellent enantiomeric excesses when ortho-cyclometalated iridium-DM-BINAP is used as the catalyst. The racemization of the substrates occurs through a designed transient Lewis acid-base interaction between the quinoline nitrogen atom and the aldehyde carbonyl group.

A Twenty-Year Survey in Low-Valent Cobalt-Catalyzed Transformations Comes to an End – A Farewell

In this Account, I report the start of my independent career, concerning cobalt-catalyzed carbon–carbon bond formations and the twenty-year long journey to the final decision to abandon the field. Some highlights, such as the regiodiverse neutral Diels–Alder reaction and the cobalt versus ruthenium-catalyzed Alder-ene reaction are discussed. Besides such highlights, also some aspects that led to unpleasant experiences are reported from a personal point of view.

1 Introduction

2 The Regiodivergent Neutral-Diels–Alder Reaction

3 The Chemoselective [2+2+2] Cyclotrimerization of Alkynes and Nitriles

4 The Cobalt-Catalyzed Alder-ene Reaction

5 The Isomerization of Carbon–Carbon Double Bonds

6 The Final Chord

7 Conclusion

A review for the assembly of multi-substituted pyridines via Co-catalyzed [2+2+2] cycloaddition with nitriles

In the recent years, many methods for the facile synthesis of pyridines and their derivatives have been developed. The [2+2+2] cycloaddition reaction of alkynes and nitriles catalyzed by transition metals...

Cobalt Catalysts for [2+2+2] Cycloaddition Reactions: Isolated Precatalysts and in situ Generated Catalysts

[2+2+2] Cycloaddition reactions belong to the not even large class of reactions, which can be catalyzed or mediated by a significant number of different transition metals. Cobalt complexes belong to the catalysts that paved the way for the extensive use and profound mechanistic knowledge on this particular transformation. Beside the established role, cyclopentadienyl (Cp) cobalt complexes inherit in synthetic applications of the cyclotrimerization reaction, modification of the precatalysts opened up novel reactivities and versatility for such catalytic initiators. At the same time the development of in situ generated cobalt catalysts allowed the conversion of novel substrates as well as novel reaction modes to be realized. In this personal account recent developments will be presented and the possibilities of catalysts containing cobalt atoms in different oxidation states be discussed.

A one-pot stepwise approach to axially chiral quinoline-3-carbaldehydes enabled by iminium–allenamine cascade catalysis

An organocatalytic atroposelective annulation between 2-(tosylamino)aryl ketones and 2-alkynals for the construction of enantioenriched axially chiral 4-arylquinoline-3-carbaldehydes is achieved.

Thiete Dioxides as Templates Towards Twisted Scaffolds and Macrocyclic Structures

Thiete dioxide units have been employed as a template for further functionalization through C-H activation strategies. Using simple thiete dioxide building blocks, a new library of axially chiral molecules has been synthesized that owe their stability to electrostatic interactions in the solid state. Similar starting materials were further engaged in the formation of cyclic trimeric structures, opening the pathway to unprecedented macrocyclic ring systems.

Air-Stable CpCoI-Phosphite-Fumarate Precatalyst in Cyclization Reactions: Comparing Different Methods of Energy Supply

The robust CoI precatalyst [CpCo(P{OEt}3)(trans-MeO2CHC=CHCO2Me)] was investigated in cyclotrimerizations, furnishing benzenes and pyridines from triynes, diynes and nitriles, comparing the influence of different ways of energy supply; namely, irradiation and conventional (thermal) or microwave heating. The precatalyst was found to work under all conditions, including the possibility to catalyze cyclotrimerizations at room temperature under photochemical conditions at longer reaction times. Performance of the reactions in a microwave reactor proved to be the most time-efficient way to rapidly assemble the expected reaction products; however, careful selection of reaction conditions can be required. The synthesis of pyridines and isoquinolines successfully involved the utilization of versatile functionalized nitriles, affording structurally interesting reaction products. Comparison with the known and often applied precatalyst CpCo(CO)2 demonstrated the significantly higher reactivity of the CpCoI-phosphite-olefin precatalyst.

Novel naphthylpyridines from cobalt-catalyzed cyclotrimerization of a chiral diyne

Abstract

The concise synthesis of a novel chiral diyne substrate for the assembly of chiral naphthylpyridines was described and different conditions for the cobalt-catalyzed co-cyclotrimerization with nitriles investigated. The products are novel naphthylpyridines possessing configurationally stable biaryl axes.

Graphical abstract

Electronic supplementary material

The online version of this article (doi:10.1007/s00706-017-2083-9) contains supplementary material, which is available to authorized users.

Ruthenium-Catalyzed [2 + 2 + 2] Cycloaddition Reaction Forming 2-Aminopyridine Derivatives from α,ω-Diynes and Cyanamides

A novel, efficient, and mild synthetic route for the preparation of 2-aminopyridines via ruthenium-mediated [2 + 2 + 2] cycloaddition of α,ω-diynes and cyanamides has been developed. This atom-economical catalytic process demonstrated remarkable regioselectivities to access pyridine derivatives of high synthetic utility.

Solvent-free ruthenium trichloride-mediated [2 + 2 + 2] cycloaddition of α,ω-diynes and cyanamides: a convenient access to 2-aminopyridines

A convenient access to functionalized 2-aminopyridinesviaa solventless Ru-catalyzed [2 + 2 + 2] cycloaddition reaction of α,ω-diynes and cyanamides is described.

Transition metal-catalyzed [2 + 2 + 2] cycloaddition of nitrogen-linked 1,6-diynes: a straightforward route to fused pyrrolidine systems

Transition metal-catalyzed [2 + 2 + 2] cycloadditions of nitrogen-linked 1,6-diynes with unsaturated motifs have recently attracted more attention from synthetic organic chemists because of their high efficiency in the construction of numerous pyrrolidine based systems.

Racemization barriers of atropisomeric 3,3′-bipyrroles: an experimental study with theoretical verification

The activation barrier of racemization was determined for atropisomeric 3,3′-bipyrroles and they are found to be configurationally stable.