Facts, Presumptions, And Myths On The Solvent-free And Catalyst-free Biginelli Reaction. What Is Catalysis For?

The current manuscript describes the role and importance of catalysis and solvent effects for the Biginelli multicomponent reaction. The overwhelming number of new catalysts and conditions recently published for the Biginelli synthesis, including in some manuscripts entitled catalyst-free and/or solvent-free have incentivized controversies and hot debates regarding the importance of developing new catalysts and reaction conditions to perform this very important multicomponent reaction. These so-called catalyst-free reports have generated much confusion in the field, requiring urgent elucidations. In this manuscript, we exemplify, demystify, and discuss the crucial role of catalysis, solvent effects, mechanisms, kinetics, facts, presumptions, and myths associated with the Biginelli reaction aiming to avoid current and future confusion and to stimulate new approaches. © 2014 American Chemical Society.79833833397Domling, A., Wang, W., Wang, K., (2012) Chem. 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Restinga lizards (Reptilia: Squamata) at the Imbassaí Preserve on the northern coast of Bahia, Brazil

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A time-based pheromone approach for the ant system

The ant system (AS) is a metaheuristic approach originally developed for solving the traveling salesman problem. AS has been successfully applied to various hard combinatorial optimization problems and different variants have been proposed in the literature. In this paper, we introduce a time-based pheromone approach for AS (TbAS). Due to this nature TbAS is applicable to routing problems involving time-windows. The novelty in TbAS is the multi-layer pheromone network structure which implicitly utilizes the service time information associated with the customers as a heuristic information. To investigate the performance of TbAS, we use the well-known vehicle routing problem with time-windows as our testbed and we conduct an extensive computational study using the Solomon [29] instances. Our results reveal that the proposed time-based pheromone approach is effective in obtaining good quality solutions