An exemplar competition between gelation and crystallisation phenomena was examined with an unusual synergistic multicomponent (organo)gelator solution (MGS), which consists of a well-defined methanolic solution of (1R,2R)-1,2-diaminocyclohexane L-tartrate containing 2.4 equiv of concentrated hydrochloric acid. The optimal composition of the MGS was determined through meticulous solubility, gelation and structural studies, which support a transient gelation mechanism based on the kinetic self-assembly of the tartrate salt driven by hydrogen-bonding interactions, involving ammonium nitrogen donors and hydroxyl oxygen acceptors, and electrostatic interactions. The hydrochloric acid is involved in the solubilisation of the salt through an ionic dissociation-exchange process, which ends up with the formation-precipitation of (1R,2R)-1,2-diaminocyclohexane dihydrochloride. As a consequence, an irreversible destruction of the gel takes place, which indicates the metastable nature of this phase that cannot be accessed from the thermodynamically equilibrated state. Gelation of a variety of oxygenated and nitrogenated solvents with moderate polarity occurred efficiently using extremely low MGS concentrations at low temperatures, and the gel phase was confirmed by dynamic rheological measurements. Several features make the described MGS unique: (1) it is a multicomponent solution where each component and its stoichiometry plays a key role in the reproducible formation and stabilization of the gels; (2) it is formed by simple, small, and commercially available chiral building blocks (dissolved in a well-defined solvent system), which are easily amenable for further modifications; (3) the gelation phenomenon takes place efficiently at low temperature upon warming up the isotropic solution, conversely to the typical gel preparation protocol; (4) the formed organogels are not thermoreversible despite the non-covalent interactions that characterize the 3D-network. 45 non-covalent bonds, predominantly hydrogen-bonding, van der Waals, charge-transfer, dipole-dipole, π-π stacking, and coordination interactions, which usually lead to reversible gel-tosol phase transitions-. Furthermore, systems based on both types of connections are also known. 12,13 The solid-like appearance of 50 gel materials is the result of the entrapment of the liquid (major component) into the compartments of a solid 3D-matrix of a large surface area (minor component), typically through surface tension

Phase selective gelation (PSG) of organic phases from their non-miscible mixtures with water was achieved using tetrapeptides bearing a side-chain azobenzene moiety. The presence of the chromophore allowed PSG at the same concentration as the minimum gelation concentration (MGC) necessary to obtain the gels in pure organic phases. Remarkably, the presence of the water phase during PSG did not impact the thermal, mechanical, and morphological properties of the corresponding organogels. In the case of miscible oil/water mixtures, the entire mixture was gelled, resulting in the formation of quasi-hydrogels. Importantly, PSG could be triggered at room temperature by ultrasound treatment of the mixture or by adding ultrasound-aided concentrated solution of the peptide in an oil-phase to a mixture of the same oil and water. Moreover, the PSG was not affected by the presence of salts or impurities existing in water from natural sources. The process could be scaled-up, and the oil phases (e.g., aromatic solvents, gasoline, diesel fuel) recovered almost quantitatively after a simple distillation process, which also allowed the recovery and reuse of the gelator. Finally, these peptidic gelators could be used to quantitatively remove toxic dyes from aqueous solutions.

Domino processes have received great attention from the chemical community because they address fundamental principles of synthetic efficiency and reaction processing. 1 Over the last four years, we have been involved in a research program aimed at developing metal-free and diversity oriented domino-based syntheses of biologically relevant heterocyclic scaffolds. 2 Our design principle is based on the expected multiplicative effect on molecular complexity achieved by a chain of two or more coupled domino processes in the same reaction vessel. This approach requires a careful design of each of the participant domino processes. To be coupled in a chain manner, each domino process must generate a suitably functionalized molecule able to be simultaneously engaged in the subsequent complexity-generating domino process and so on. Additionally, the whole process would be performed in a format amenable for application in combinatorial chemistry. Experimentally, the transformation of this concept in a one synthetic step strategy is not a simple task due to the unattainable kinetic tuning of each of the numerous chemical reactions involved. A more feasible approach should consist in the transformation of this concept in a one-pot synthetic strategy. In this new scenario, the consecutive coupled domino processes should be performed one at a time and linked in a onepot operation. In a first experimental approach, we chose the simple model shown in eq 1, addressing the synthesis of polysubstituted pyrroles. The protocol combines two coupled domino processes: the trialkylamine-catalyzed synthesis of enolprotected propargylic alcohols 1 2 (domino I) and their sequential transformation into pyrroles 3 (domino II). The key for this transformation came from a serendipitously discovered spontaneous rearrangement of 1,3-oxazolidines 2 to pyrroles 3.Polysubstituted pyrroles are common pharmacophores of numerous natural antibiotics and alkaloids 3 and they have also found applications in the field of material chemistry. 4 These properties are of considerable interest in the development of new efficient syntheses of these heterocycles. Among the plethora of methods available for pyrrole construction, 3 metal-based strategies 5 and 1,3-dipolar cycloadditions 6 have concentrated the most attention. In contrast, the number of examples reported in the literature dealing with metal-free, modular and direct syntheses of these heterocycles is scarce. 7 Therefore, there is a clear demand for new metal-free, modular and direct synthetic protocols with atom-economy, easy reaction processing, general applicability and environmental care performance.1,3-Oxazolidines 2 are readily obtained in a one-pot manner by the ytterbium-catalyzed reaction 8 of the conjugated alkynoates 1 and primary amines (eq 2). Pure 1,3-oxazolidines 2 rearrange to pyrroles 3 when they are stored on the bench without solvent (eq 2). This rearrangement is very slow at room temperature and needs months to be completed. 9 While heating speeds up this process from months to ...