62155-45-7Relevant academic research and scientific papers
Water and Sodium Chloride: Essential Ingredients for Robust and Fast Pd-Catalysed Cross-Coupling Reactions between Organolithium Reagents and (Hetero)aryl Halides
Dilauro, Giuseppe,Quivelli, Andrea Francesca,Vitale, Paola,Capriati, Vito,Perna, Filippo Maria
supporting information, p. 1799 - 1802 (2019/01/25)
Direct palladium-catalysed cross-couplings between organolithium reagents and (hetero)aryl halides (Br, Cl) proceed fast, cleanly and selectively at room temperature in air, with water as the only reaction medium and in the presence of NaCl as a cheap additive. Under optimised reaction conditions, a water-accelerated catalysis is responsible for furnishing C(sp3)–C(sp2), C(sp2)–C(sp2), and C(sp)–C(sp2) cross-coupled products, in competition with protonolysis, within a reaction time of 20 s, in yields of up to 99 %, and in the absence of undesired dehalogenated/homocoupling side products even when challenging secondary organolithiums serve as the starting material. It is worth noting that the proposed protocol is scalable and the catalyst and water can easily and successfully be recycled up to 10 times, with an E-factor as low as 7.35.
Environmentally Friendly Chemistry using Supported Reagent Catalysts: Structure-Property Relationships for Clayzic
Clark, James H.,Cullen, Stephen R.,Barlow, Simon J.,Bastock, Tony W.
, p. 1117 - 1130 (2007/10/02)
Supported reagents have been widely used in organic synthesis for some 25 years and their importance is likely to increase as a result of new environmental legislation and the drive towards clean technology.While many supported reagents are stoichiometric in reactions the successful development of genuinely catalytic materials greatly enhances their value especially in liquid phase, typically fine chemical syntheses.Achieving an understanding of the nature of these fascinating materials is also an important aspect of their development and is essential if their true potential is to be realised.Solid acids are the most widely studied of supported reagents and their use as more environmentally acceptable replacements for conventional Broensted and Lewis acids is likely to become increasingly important.Clayzic is a good example of an evironmentally friendly catalyst with particular value as an alternative to the hazardous reagent aluminium chloride in Friedel-Crafts reactions.The structure and properties of this catalyst are, however, poorly understood.X-Ray diffraction studies show that thermal treatment of either clayzic or its base material K10 results in the loss of any montmorillonite crystallinity that remained after the acid treatment of tonsil 13 used to form K10.Thermal treatment of clayzic also results in a steady increase in the surface area of the material.While this is also consistent with structural changes the increase is also likely to be partly due to the dehydration allowing the non-polar adsorbate to enter more of the polar regions of the material.These polar regions can be identified as mesopores created by the acid treatment of the clay and in which the zinc ions largely reside.Spectroscopic titration of the acid sites in clayzic show these to be largely Lewis acid in character.Thus clayzic owes its remarkable Friedel-Crafts activity to the presence of high local concentrations of zinc ions in structural mesopores.Relative reaction rates for the clayzic catalysed benzylation of alkylbenzenes also reveal the importance of these highly polar mesopores.Considerable rate enhancements can be achieved by thermally activating the catalyst and this can be largely attributed to the dehydration of the catalyst enabling better partitioning of the alkylbenzenes into the mesopores.Clayzic can be considered as being a large pore molecular sieve but where the sieving of molecules is controlled more by molecular polarities/polarisibilities than by molecular shape.
