Asymmetric reactions in water and in aqueous solutions have become an area of fast growing interest recently. Although for a long time neglected as a medium for organic reactions, water has attracted attention as the most widely distributed solvent in the world. Indeed, water is the solvent used by nature for biological chemistry including aldol reactions being essential for glycolysis, gluconeogenesis and related processes. Consequently, artificial catalysts designed and used for aldol reactions in water can be promising for the synthesis of enantiopure molecules and are also important for the understanding of complex chemistry of life. This tutorial review summarizes recent developments in the area of aqueous asymmetric aldol reactions highlighting two fundamental directions – development of water compatible chiral Lewis acids and amine-based organocatalysts.

The structures and magnetic properties of photoresponsive magnets can be controlled or fine-tuned by visible light irradiation, which makes them appealing as candidates for ternary memory devices: photochromic and photomagnetic at the same time. One of the strategies for photoresponsive magnetic systems is the use of photochromic/photoswitchable molecules coordinated to paramagnetic metal centers to indirectly influence their magnetic properties. Herein, we present two erbium(III)-based coordination systems: a trinuclear molecule {[Er^III(BHT)₃]₃(dtepy)₂}^.4C₅H₁₂ (1) and a 1D coordination chain {[Er^III(BHT)₃(azopy)}_n·2C₅H₁₂ (2), where the bridging photochromic ligands belong to the class of diarylethenes: 1,2-bis((2-methyl-5-pyridyl)thie-3-yl)perfluorocyclopentene (dtepy) and 4,4'-azopyridine (azopy), respectively (BHT = 2,6-di-tert-butyl-4-methylphenolate). Both compounds show slow dynamics of magnetization, typical for single-molecule magnets (SMMs) as revealed by alternating current (AC) magnetic susceptibility measurements. The trinuclear compound 1 also shows an immediate color change from yellow to dark blue in response to near-UV irradiation. Such behavior is typical for the photoisomerization of the open form of the ligand into its closed form. The color change can be reversed by exposing the closed form to visible light. The chain-like compound 2, on the other hand, does not show significant signs of the expected trans-cis photoisomerization of the azopyridine in response to UV irradiation and does not appear to show photoswitching behavior.

Discovery of new types of reactions is essential to organic chemistry because it expands the scope of accessible molecular scaffolds and can enable more economical syntheses of existing structures. In this context, the so-called multicomponent reactions, MCRs, are of particular interest because they can build complex scaffolds from multiple starting materials in just one step, without purification of intermediates. However, for over a century of active research, MCRs have been discovered rather than designed, and their number remains limited to only several hundred. This work demonstrates that computers taught the essential knowledge of reaction mechanisms and rules of physical-organic chemistry can design – completely autonomously and in large numbers – mechanistically distinct MCRs. Moreover, when supplemented by models to approximate kinetic rates, the algorithm can predict reaction yields and identify reactions that have potential for organocatalysis. These predictions are validated by experiments spanning different modes of reactivity and diverse product scaffolds.