Transfer hydrogenation of olefins catalysed by nickel nanoparticles

Nickel nanoparticles have been found to effectively catalyse the hydrogen-transfer reduction of a variety of non-functionalised and functionalised olefins using 2-propanol as the hydrogen donor. The heterogeneous process has been shown to be highly chemoselective for certain substrates, with all the corresponding alkanes being obtained in high yields. A synthesis of the natural dihydrostilbene brittonin A is also reported based on the use of nickel nanoparticles.Spanish Ministerio de Educación y Ciencia (MEC; grant no. CTQ2007-65218; Consolider Ingenio 2010-CSD2007-00006) and the Generalitat Valenciana (PROMETEO2009/039)

Nanopartículas de níquel: formación de enlaces carbono-carbono y transferencia de hidrógeno

En la presente memoria se describe la aplicación de nanopartículas de níquel a reacciones de formación de enlaces carbono-carbono y de reducción por transferencia de hidrógeno. Las nanopartículas de níquel han sido preparadas por reducción de cloruro de níquel(ll) con litio en polvo y una cantidad catalítica del areno 4,4' -di-terc-butilbifenilo en THF a temperatura ambiente. En el Capítulo 1 se estudia el comportamiento de estas nanopartículas de níquel en la reacción de homoacoplamiento de haluros de arilo. El Capítulo 2 trata sobre la actividad de las nanopartículas de níquel en reacciones de transferencia de hidrógeno, utilizando isopropanol como donador de hidrógeno. Se estudia la reducción de olefinas, compuestos carbonílicos y aminación reductora, junto con una caracterización completa de las nanopartículas aplicando distintas técnicas instrumentales. En el Capítulo 3 se aplican las nanopartículas de níquel a la α-alquilación de cetonas con alcoholes primarios. Por último, en el Capítulo 4, se estudia la aplicación de las nanopartículas de níquel a reacciones de tipo Wittig, incluyendo la síntesis de estilbenos polimetoxilados, algunos de ellos, como el DMU-212, presentan destacada actividad biológica o son precursores de productos naturales como el resveratrol

Application of metal oxide semiconductors in light-driven organic transformations

The search for greener alternatives to perform organic reactions has become the order of the day in the chemistry community. In this regard, the use of heterogeneous photocatalysts has emerged as a powerful alternative to replace transition metal-based complexes and organic dyes to enable light-driven organic transformations. Within this realm, metal oxide semiconductors (MOS) have become increasingly popular due to their recyclability, availability, energy efficiency, photo- and chemical stability and generally low toxicity. Here, we cover the most relevant literature related to the use of MOS as photocatalysts to light induce organic reactions, including oxidations, C–C and C-heteroatom bond formations. We also discuss the mechanisms involved in these processes, as well as the hitherto best known MOS modifications able to enhance their photocatalytic performance

Application of metal oxide semiconductors in light-driven organic transformations

The search for greener alternatives to perform organic reactions has become the order of the day in the chemistry community. In this regard, the use of heterogeneous photocatalysts has emerged as a powerful alternative to replace transition metal-based complexes and organic dyes to enable light-driven organic transformations. Within this realm, metal oxide semiconductors (MOS) have become increasingly popular due to their recyclability, availability, energy efficiency, photo- and chemical stability and generally low toxicity. Here, we cover the most relevant literature related to the use of MOS as photocatalysts to light induce organic reactions, including oxidations, C–C and C-heteroatom bond formations. We also discuss the mechanisms involved in these processes, as well as the hitherto best known MOS modifications able to enhance their photocatalytic performance

Nickel nanoparticles in hydrogen-transfer reductions: characterisation and nature of the catalyst

Nickel nanoparticles, readily prepared by reduction of nickel(II) chloride with lithium and a catalytic amount of DTBB, have been used in the transfer hydrogenation of carbonyl compounds and have been fully characterised by different means. The reaction rate of the transfer hydrogenation was found to be dependent on the acetophenone and isopropanol concentration but independent on the amount of lithium chloride. The deactivation of the catalyst after reuse has been mainly attributed to surface oxidation but not to coke formation. All the experiments performed are in agreement with the process being of heterogeneous nature. The nickel nanoparticles unveiled a superior behaviour in comparison with commercially available nickel catalysts.Spanish Ministerio de Educación y Ciencia (MEC; grant no. CTQ2007-65218 and Consolider Ingenio 2010-CSD2007-00006) and the Generalitat Valenciana (grant no. PROMETEO/2009/039)

Energy-efficient solar photochemistry with luminescent solar concentrator based photomicroreactors

\u3cp\u3eThe sun is the most sustainable light source available on our planet, therefore the direct use of sunlight for photochemistry is extremely appealing. Demonstrated here, for the first time, is that a diverse set of photon-driven transformations can be efficiently powered by solar irradiation with the use of solvent-resistant and cheap luminescent solar concentrator based photomicroreactors. Blue, green, and red reactors can accommodate both homogeneous and multiphase reaction conditions, including photochemical oxidations, photocatalytic trifluoromethylation chemistry, and metallaphotoredox transformations, thus spanning applications over the entire visible-light spectrum. To further illustrate the efficacy of these novel solar reactors, medicinally relevant molecules, such as ascaridole and an intermediate of artemisinin, were prepared as well.\u3c/p\u3