Capítulo 1. Adiciones Michael asimétricas organocatalizadas en líquidos eutécticos. Siguiendo los principios de la “Química Verde” se desarrolló un sistema catalítico basado en disolventes eutécticos y organocatalizadores quirales derivados de 2-amino benzimidazol. Este nuevo sistema fue empleado para catalizar la adición enantioselectiva de compuestos de 1,3-dicarbonílicos a β-nitroestirenos. El procedimiento evita el uso de disolventes orgánicos volátiles tóxicos como medio reacción, proporcionando acceso a moléculas quirales altamente funcionalizadas de forma selectiva y eficiente. Además, la reacción puede realizarse a una escala de gramos y a su vez este sistema catalítico es fácilmente reciclable y reutilizable durante cuatro ciclos, lo que da lugar a un procedimiento limpio, económico, sencillo y escalable que cumple la mayoría de los criterios necesarios para ser un proceso medioambientalmente benigno y sostenible. Los estudios de RMN realizados a la mezcla organocatalizador-líquido eutéctico han confirmado el papel clave de los enlaces de hidrógeno entre el disolvente y el organocatalizador quiral, que permiten su recuperación y la reciclabilidad del sistema. Capítulo 2. α-Aminación electrofílica asimétrica organocatalizada en líquidos eutécticos. Empleando el sistema catalítico basado en el uso de catalizadores quirales de 2-benzoimidazol y líquidos eutécticos se realizó la α-aminación enantioselectiva de compuestos de 1,3-dicarbonílicos. Con este procedimiento, se evita el uso de compuestos orgánicos volátiles tóxicos como medios de reacción. Las moléculas quirales altamente funcionalizadas sintetizadas, que son importantes en la síntesis de productos naturales, se sintetizaron mediante un protocolo eficiente y estereoselectivo. Además, la reacción puede llevarse a cabo para la síntesis de un gramo de producto, siendo posible el reciclaje del sistema catalítico durante al menos cinco ciclos de reacción consecutivos. Este procedimiento representa un método barato, simple, limpio y escalable que cumple con la mayoría de los principios para ser considerado un proceso medioambientalmente benigno y sostenible. Capítulo 3. Líquidos eutécticos quirales. Diferentes mezclas eutécticas basadas en prolina fueron empleadas en la adición Michael asimétrica de cetonas sobre nitroalquenos. En vista de los resultados, y los estudios de 1H-RMN realizados, se confirmó una relación entre la conversión y selectividad del proceso con la constante asociación de los componentes de la mezcla eutéctica. Con estos datos un nuevo disolvente eutéctico quiral a base de bromuro de (S)-N,N,N,-trimetil-1-(pirrolidin-2-il)-metanamina y glicerol fue diseñado y sintetizado con éxito. Este sistema catalítico se mostró eficiente en la adición Michael de ciclohexanona a β-nitroestirenos, obteniendo selectividades moderadas en condiciones suaves. El sistema catalítico eutéctico fue recuperado fácilmente y reciclado hasta cinco veces en la adición de ciclohexanona a β-nitroestireno sin pérdida significativa de actividad catalítica.

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Stereodivergent and enantiodivergent pathways for the Friedel–Crafts reactions were computationally studied with DFT methods. This study aims to explain recently observed solvent-dependent regioselectivity, and enantioselectivity when cinchona catalyst is used. Deprotonation reaction, Frontier Kohn-Sham orbitals, dual descriptors, Mulliken charges, and Hirshfeld atomic charge for reactant were calculated and analyzed. The most probable position of electrophilic attack and nucleophilic attack in-silico predicted aligns with experimental observations. The calculation of the transition states on the anionic and neutral model in a vacuum show preference for the electrophilic attack in the para position. In comparison to the anionic system, the presence of potassium cation improves ortho/para selectivity and increases the energy barrier. For the key enantioselective step, 12 transition states were calculated which covers 4 representative product such: (R)-ortho, (S)-ortho, (R)-para, and (S)-para. The computational study suggests, that the presence of the cesium cation is essential for the arrangement of the reactant and catalyst in the transition state, which leads to observed selectivity.

Ring-opening polymerization (ROP) is a promising approach to accessing well-defined polyesters with superior (bio)degradability and recyclability. However, the living/controlled polymerization of glycolide (GL), a well-known sustainable monomer derived from carbon mono/di-oxide, has never been reported due to the extremely low solubility of its polymer in common solvents. Herein, we report the first living/controlled anionic ROP of GL in strong protic fluoroalcohols (FAs), which are conventionally considered incompatible with anionic polymerization. Well-defined polyglycolide (PGA, Ð < 1.15, Mn up to 55.4 kg mol-1) and various PGA-based macromolecules are obtained at room temperature for the first time. NMR titration and computational studies revealed that FAs simultaneously activate the chain-end and monomer without being involved in initiation. Low boiling point FAs and PGA can be recycled through simple distillation and sublimation at 220 oC in vacuo, respectively, providing a promising sustainable alternative for tackling plastic pollution problems. Well-defined multicrystalline multiblock polymers are essential model polymers for advancing crystallization physics, phase separation, self-assembly, and improving the mechanical properties of materials. However, due to the different chain properties and incompatible synthetic methodology, multicrystalline multiblock polymers with more than two crystallites are rarely reported. Herein, by combining polyhomologation, ring-opening polymerization, and “catalyst switch” strategy, we synthesized the first pentacrystalline pentablock quintopolymer, polyethylene-b-poly(ethylene oxide)-b-poly(e-caprolactone)-b-poly(L-lactide)-b-polyglycolide (PE-b-PEO-b-PCL-b-PLLA-b-PGA). The novel “fluoroalcohol-assisted catalyst switch” enables the first successful incorporation of a high melting point polyglycolide into the complex multiblock polymer. Solid-state NMR spectroscopy, X-ray diffraction, and differential scanning calorimetry revealed the existence of five different crystalline phases.

This doctoral thesis focuses on applying different organocatalysts in several enantioselective reactions and aerobic photooxidations using visible light. Chapter 1 describes using a chiral primary amine-salicylamide derived from (1R,2R)-cyclohexane-1,2-diamine as chiral organocatalyst in the asymmetric conjugate Michael addition of aldehydes and ketones to maleimides, giving the corresponding enantioenriched succinimides. The same organocatalyst is used in the enantioselective Michael addition of aldehydes to nitroalkenes, yielding enantiopure γ-nitroaldehydes. Furthermore, these Michael additions of aldehydes to maleimides and nitroalkenes are carried out employing sustainable and environmentally friendly deep eutectic solvents (DES), being able to reuse the catalytic system for several cycles. Chapter 2 describes using a chiral primary-amine monocarbamate derived from (1R,2R)-cyclohexane-1,2-diamine as chiral organocatalyst in the enantioselective α-amination of aldehydes with azodicarboxylates, obtaining the corresponding α,α-disubstituted aldehydes with the absence of solvent under mild conditions. This simple orgacatalytic system’s applicability is demonstrated by preparing a chiral oxazolidinone precursor of amino acids. The reaction is also successfully scaled-up. In addition, theoretical calculations were performed to demonstrate how the absolute configuration of the final adducts is produced. Chapter 3 shows how riboflavin tetraacetate, a cheap vitamin B2 derivative, is an appropriate metal-free photocatalyst in the aerobic photooxidation of xanthenes, thioxanthenes and dihydroacridines under visible light irradiation. / This research work has been possible thanks to funding from the Spanish Ministerio de Economía y Competitividad (PGC2018-096616-B-100, CTQ201788171-P), the Generalitat Valenciana (AICO 2021/013) and the University of Alicante (VIGROB-173). The author wishes to express his gratitude to the Institute of Organic Synthesis for a research contract (I-PI/21-20) and to the University of Alicante-Banco Santander consortium for a grant to spend a three-months research period in the Chemistry Interdisciplinary Project research center (ChIP) of the University of Camerino (Italy) under the supervision of Dr. Matteo Tiecco.

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