Chiral Ca-, Sr-, and Ba-Catalyzed Asymmetric Direct-Type Aldol, Michael, Mannich, and Related Reactions

Chiral Metal Salts as Ligands for Catalytic Asymmetric Mannich Reactions with Simple Amides

Catalytic asymmetric Mannich reactions of imines with weakly acidic simple amides were developed using a chiral potassium hexamethyldisilazide (KHMDS)-bis(oxazoline) potassium salt (K-Box) catalyst system. The desired reactions proceeded to afford the target compounds in high yields with high diastereo- and enantioselectivities. It was suggested that a K enolate interacted with K-Box to form a chiral K enolate that reacted with imines efficiently. In this system, K-Box (potassium salt of Box) worked as a chiral ligand of the active potassium species.

Highly Lewis acidic cationic alkaline earth metal complexes

Cationic Lewis base-free β-diketiminate (BDI) complexes of Mg and Ca have been isolated as their B(C₆F₅)₄^- salts. The cation (BDI)Mg⁺ shows an extraordinarily strong Lewis acidity that can compete with strong Lewis acids like B(C₆F₅)₃ and (BDI)AlMe⁺. Its highly electrophilic nature is exemplified by isolation of an 3-hexyne adduct.

Tethered cationic alkaline earth – olefin complexes

The utilisation of a specifically tailored aminofluoroalcohol possessing both a methoxy and an olefin dangling side arms enables the preparation of the first examples of discrete calcium- and strontium-olefin cationic complexes.

Calcium, Strontium and Barium Homogeneous Catalysts for Fine Chemicals Synthesis

The large alkaline earths (Ae), calcium, strontium and barium, have in the past 15 years yielded a brand new generation of heteroleptic molecular catalysts for the production of fine chemicals. However, the integrity of these complexes is often plagued by ligand redistribution equilibria in solution. This personal account retraces the paths followed in our research group towards the design of stable heteroleptic alkalino-earth complexes, including the use of intramolecular noncovalent Ae···H-Si and Ae···F-C interactions. Their implementation as homogenous precatalysts for reactions such as the intramolecular and intermolecular hydroamination and hydrophosphination of activated alkenes, the hydrophosphonylation of ketones, and the dehydrogenative coupling of amines and hydrosilanes that enable the efficient and controlled formations of CP, CN, or SiN σ-bonds, is presented in a synthetic perspective that highlights their overall outstanding catalytic performance.

Flow "Fine" Synthesis: High Yielding and Selective Organic Synthesis by Flow Methods

The concept of flow "fine" synthesis, that is, high yielding and selective organic synthesis by flow methods, is described. Some examples of flow "fine" synthesis of natural products and APIs are discussed. Flow methods have several advantages over batch methods in terms of environmental compatibility, efficiency, and safety. However, synthesis by flow methods is more difficult than synthesis by batch methods. Indeed, it has been considered that synthesis by flow methods can be applicable for the production of simple gasses but that it is difficult to apply to the synthesis of complex molecules such as natural products and APIs. Therefore, organic synthesis of such complex molecules has been conducted by batch methods. On the other hand, syntheses and reactions that attain high yields and high selectivities by flow methods are increasingly reported. Flow methods are leading candidates for the next generation of manufacturing methods that can mitigate environmental concerns toward sustainable society.

Dinuclear zinc-catalyzed desymmetric intramolecular aldolization: an enantioselective construction of spiro[cyclohexanone-oxindole] derivatives

A bis-ProPhenol zinc complex-catalyzed asymmetric desymmetrizing intramolecular aldol or aldol condensation reaction is reported, which furnishes spiro[cyclohexanone-oxindole] derivatives in good yields with moderate to high enantioselectivities.

The first calcium-catalysed Nazarov cyclisation

The first calcium-catalysed Nazarov cyclisation is described.