Recent Advances in Sustainable Organocatalysis

The recent advances on green and sustainable organocatalysis are revised in this chapter. An important focus on one of the 12 principles of green chemistry, organocatalysis pursues to reduce energy consumption as well as to optimize the use of different resources, targeting to become a sustainable strategy in organic chemical transformations. In last decades, several experimental methodologies have been performed to make organocatalysis an even greener and sustainable alternative to stoichiometric approaches as well as non-catalytic conditions by the use of benign and friendlier reaction media. In this line, several approaches using water as preferential solvent, alternative solvents such as ionic liquids including chiral ones, deep eutectic solvents, polyethylene glycol (PEG), supercritical fluids and organic carbonates or solvent-free methodologies have been reported. In this chapter, we mainly focus on the recent remarkable advancements in organocatalysis using green and sustainable protocols

Atropselective Organocatalytic Synthesis of Chiral Compounds Containing Nitrogen along the Axis of Chirality

Atropisomers, i.e., stereoisomers that are distinct because their free rotation about a single bond is hindered by steric interactions between nearby bulky groups or by electrostatics, may interact with their surroundings in different ways, and may also exhibit different properties. They may be found as natural products, as pharmaceutical or agricultural active ingredients, as chiral ligands and organocatalysts, and in functional materials. Our ability to synthesize them stereoselectively and in a sustainable way, using achiral materials and simply with the aid of an organocatalyst and mild conditions, has become a hot topic in research. This review provides an overview of recent achievements in the synthesis of atropisomers containing C-N and N-N axes of chirality

Applications of Hantzsch Esters in Organocatalytic Enantioselective Synthesis

Hantzsch esters (1,4-dihydropyridine dicarboxylates) have become, in this century, very versatile reagents for enantioselective organic transformations. They can act as hydride transfer agents to reduce, regioselectively, a variety of multiple bonds, e.g., C=C and C=N, under mild reaction conditions. They are excellent reagents for the dearomatization of heteroaromatic substances, and participate readily in cascade processes. In the last few years, they have also become useful reagents for photoredox reactions. They can participate as sacrificial electron and hydrogen donors and when 4-alkyl or 4-acyl-substituted, they can act as alkyl or acyl radical transfer agents. These last reactions may take place in the presence or absence of a photocatalyst. This review surveys the literature published in this area in the last five years

New Trends in Enantioselective Cross-Dehydrogenative Coupling

The development of cross-dehydrogenative coupling in recent years has simplified the synthesis of many materials, as a result of facile C–H activation, which, together with its greater atom economy and environmental friendliness, has made an impact on modern organic chemistry. Indeed, many C–C and C–X (X = N, O, P, S, B, or Si) coupling reactions can now be performed directly between two C–H bonds or a C–H and an X–H bond, simply by adding catalytic amounts of a metal salt to a mixture of the two and an oxidant to accept the two hydrogen atoms released. Chiral organocatalysts or chiral ligands have been joined to promote enantioselective processes, resulting in the development of efficient reaction cascades that provide products in high yields and high levels of asymmetric induction through cooperative catalysis. In recent years, photochemical oxidation and electrochemistry have widened even more the scope of cross-dehydrogenative coupling (CDC). In this review, we summarized the recent literature in this subject, hoping that it will inspire many new synthetic strategies