416 research outputs found
Oxazolidinone-Derived N-Centered Radicals: Unlocking Bioactive Compounds by Photoredox Catalysis
No full textThe recent advancements in radical chemistry have paved the way for new opportunities in synthesis, solving challenges that more conventional methodologies have historically encountered. Traditional approaches used to build C-N bonds often rely on high temperatures and pre-functionalized coupling partners, such as Cu-catalyzed Ullman type coupling or Pd-catalyzed Buchwald-Hartwig amination.1 However, in the last few years, some of these issues have been solved by the use of N-centered radicals generated by photoredox catalysis. These radicals have proven effective for building C-N bonds under mild reaction conditions. The use of N-centered radicals, when combined with flow chemistry, have proven to be effective also for large-scale productions, overcoming issues related to limited light penetration associated to batch processes. 2
In this context, we focused our attention on the development of novel synthetic methodologies for the synthesis of products of pharmaceutical interest such as Linezolid and Eperezolid3 (Figure 1a), involving the use of N-oxazolidinone radicals generated by photocatalytic approach. An easy protocol for the generation of N-oxazolidinone radicals have been developed (Figure 1b), which were successfully employed in amidation reactions of various aromatic substrates performed under traditional batch and continuous flow conditions. These initial investigations mark a significant step toward devising efficient and sustainable methods for the synthesis of APIs
Photoredox Catalysis: Innovative Reactions of N-Oxazolidinone Radicals with Indoles
No full textThe chemistry of radicals has extensively developed in recent years. These advancements have paved the way for new synthetic opportunities, which could be considered highly challenging or unapproachable if conventional methods are used. Traditional approaches used to build C-N bonds often rely on high temperatures and pre-functionalized coupling partners, such as Pd-catalyzed Buchwald-Hartwig amination/amidation or Cu-catalyzed Ullman and Goldberg couplings. However, in the last few years, some of these issues have been solved by the use of N-centered radicals generated by photoredox catalysis.1,2 These radicals have proven effective for building C-N bonds under mild reaction conditions.
In this context, we focused our attention on the development of novel methodologies for the synthesis of products of pharmaceutical interest, involving the use of the unexplored N-oxazolidinone radicals generated by photocatalytic approach. An easy protocol for the generation of the radicals have been developed (Figure 1), which were successfully employed in amidation reactions of different aromatic substrates, such as indoles. These initial investigations mark a significant step toward devising efficient and sustainable methods for the synthesis of APIs
Oxazolidinone-Derived N-Centered Radicals: in Batch and in Flow Photoredox Catalysis
No full textThe recent advancements in radical chemistry have paved the way for new opportunities in synthesis, solving challenges that more conventional methodologies have historically encountered. Traditional approaches used to build C-N bonds often rely on high temperatures and pre-functionalized coupling partners, such as Cu-catalyzed Ullman type coupling or Pd-catalyzed Buchwald-Hartwig amination.1 However, in the last few years, some of these issues have been solved by the use of N-centered radicals generated by photoredox catalysis. These radicals have proven effective for building C-N bonds under mild reaction conditions. The use of N-centered radicals, when combined with flow chemistry, have proven to be effective also for large-scale productions, overcoming issues related to limited light penetration associated to batch processes. 2
In this context, we focused our attention on the development of novel synthetic methodologies for the synthesis of products of pharmaceutical interest such as Linezolid and Eperezolid3 (Figure 1a), involving the use of N-oxazolidinone radicals generated by photocatalytic approach. An easy protocol for the generation of N-oxazolidinone radicals have been developed (Figure 1b), which were successfully employed in amidation reactions of various aromatic substrates performed under traditional batch and continuous flow conditions. These initial investigations mark a significant step toward devising efficient and sustainable methods for the synthesis of APIs
Visible Light Photoredox Catalysis: Generation of N-Oxazolidinone Radicals for the Synthesis of APIs
No full textThe recent advancements in radical chemistry have paved the way for new synthetic opportunities, solving challenges that more traditional methodologies have historically encountered. Conventional approaches used to build C-N bonds often rely on high temperatures and pre-functionalized coupling partners, such as Cu-catalyzed Ullman type coupling or Pd-catalyzed Buchwald-Hartwig amination [1]. However, in the last few years, some of these issues have been solved by the use of N-centered radicals generated by photoredox catalysis. These radicals have proven effective for building C-N bonds under mild reaction conditions.
In this context, we focused our attention on the development of novel methodologies for the synthesis of bioactive compounds such as Linezolid and Eperezolid [2] (Figure 1a), involving the use of the totally unexplored N-oxazolidinone radicals generated by photocatalytic approach. An easy protocol for the generation of the radicals have been developed (Figure 1b), which were successfully employed in amidation reactions of various aromatic substrates. These initial investigations mark a significant step toward devising efficient and sustainable methods for the synthesis of APIs
Connecting Rural Road Design to Automated Vehicles: The Concept of Safe Speed to Overcome Human Errors
No full textThe human-road-vehicle automated system is a challenge to overcome human errors. Several rural road crashes happen due to loss of friction, unlikely predictable by drivers. The friction diagram method (FDM) by the authors, described in previous papers, is able to evaluate the skidding risk taking into account vehicle, environmental, road factors. An important variable is the vehicle speed. According to the FDM, the speed corresponding to the maximum friction used can be computed. If all vehicles will travel at speeds lower than that, all other safety checks being verified, then the skidding risk can be reduced. Automated vehicles could travel at the safe speed predicted for each section, by acquiring all the necessary information directly from the road. The algorithm can be customized according to the particular vehicle, tires and road conditions. Additional remarks about the shift from traditional road design practice to the driving automation are also given
The deviation angle for one-lane roundabouts: A general mathematical formulation and application
No full textProperly designed roundabouts may lead to safety improvements based on both reducing approaching speeds and controlling traffic. Measurements of deflection of vehicle trajectories are commonly used to estimate roundabout speed control. One of these measurements is the deviation angle, which is mentioned in both the Italian and Swiss road standards and, in specific conditions, can be more effective than other methods. This article presents a general mathematical formulation for linking several geometric parameters with the deviation angle in different rural and urban one-lane roundabout configurations, which is currently missing in the literature. For urban roundabouts, refuge islands for pedestrians and cyclists were considered. Based on the proposed formulation, a sensitivity analysis of the influential geometric parameters was conducted. Results suggest that an insufficient deflection of trajectories (deviation angle less than 45°) is always present for roundabouts with inscribed circle diameter less than 25 m; for urban roundabouts with refuge islands for pedestrians and cyclists having inscribed circle diameter less than 34 m and orthogonal legs; and for roundabouts with angles between opposite legs smaller than 140°. The main parameters which are responsible for a decrease in the deviation angle are: a decrease in the inscribed circle diameter; a decrease in the angle between opposite legs; and an increase in the width of the circulatory lane. Some optimized procedures for roundabout design, the generalized application of the deviation angle method and alternative speed control measures in cases of small deviation angles are discussed
The spatial dimension of competition among airports at the worldwide level: a spatial stochastic frontier analysis
No full textThis paper analyses the potential impact of airport competition on technical efficiency by applying the spatial stochastic frontier approach (SSFA) rather than the traditional model (SFA). The SSFA allows for isolating the cross-sectional spatial dependence and evaluating the role of intangible factors in influ- encing an airport’s economic performance through the inclusion of the distance matrix and the shared destinations matrix calibrated for different distances. By analysing the statistical differences between the traditional and the spatial model, it is possible to identify the competition effects. This study includes 206 airports at the worldwide level. The results show the existence of the spatial component: we detected a different influence of airports’ efficiency levels according to the geographical distances. This could have not been captured by the traditional SFA. We conclude that when incorporating spatial spillover effects into the airport efficiency analysis, the efficiency dynamics are strongly dependent on the spatial distance among airports
La programmazione del turismo e della mobilità sostenibile nelle aree naturali protette
No full textLa relazione tra turismo e sviluppo sostenibile dei territori compresi nelle aree protette, si
è evoluta in modo significativo negli ultimi anni. In particolare, in Italia si è passati da
una situazione di contrapposizione e di reciproca esclusione, ad un graduale
riconoscimento del ruolo strategico che il turismo può rivestire nel fornire una risposta
alle esigenze delle comunità locali e nel mantenere le promesse di sviluppo sociale ed
economico che in passato hanno spesso accompagnato l’istituzione dei Parchi nazionali.
Già a partire dalla Legge Quadro n. 394/1991 si è introdotta, infatti, in queste aree la
possibilità di realizzare attività di sviluppo economico “ecocompatibile”, da attuarsi
mediante lo strumento della pianificazione pluriennale economica e sociale, nel rispetto
delle condizioni di salvaguardia ambientale che permettono di non superare i livelli oltre i
quali possano essere innescati processi irreversibili di degrado.
Alle aree protette si riconosce dunque una nuova funzione di territori di pregio in cui
sperimentare nuovi modelli di crescita economica sostenibile, integrata e rispettosa
dell’ambiente, costituendo così un luogo privilegiato per il management dello sviluppo
locale (Buongiorno e Intini, 2019).
Nell’ambito di tale evoluzione, trova giustificazione la più recente visione del turismo
quale opportunità per il territorio: è infatti emerso che un turismo di qualità, in grado di
conservare l’ambiente e sostenere il benessere delle popolazioni locali, rappresenti un
fattore di cruciale importanza per lo sviluppo non solo dei parchi, ma anche dei territori
ad essi correlati (Bergantino et al., 2020).
Tuttavia, resta evidente l’esistenza di un trade-off tra quantità di beni e servizi richiesti e
offerti per il turismo, da un lato, e qualità dell’ambiente dall’altro, la cui intensità dipende
strettamente dal tipo di risorse locali su cui è basato il turismo, dalla qualità e dimensione
dei flussi attivati e dal livello di salvaguardia e manutenzione delle risorse. È proprio la
necessità di ridurre l’intensità di questo trade-off a rendere necessaria e ineludibile
un’oculata gestione turistica del territorio, in modo tale da garantire crescita economica e
tutela ambientale, specialmente quando uno dei fattori attrattivi posto alla base della
crescita è costituito proprio dalla qualità ambientale, come nel caso delle aree protette
The influence of memory on driving behavior: How route familiarity is related to speed choice. An on-road study
No full textDifferences in driving behavior due to the presence of users familiar (or unfamiliar) with the road are considered in the road and traffic engineering. However, although considered, the matter is largely unexplored: there is a lack of theoretical foundations and data on determining the impact of route familiarity on accident rates, speed choice and risk perception. On the other hand, some literature studies confirm that route familiarity is influential on driving behavior, encouraging research in this sense.This paper reports the results of an on-road test carried out on a two lane rural road in the District of Bari in the Puglia Region (Italy) over six days of testing by following this time schedule: first four tests in four consecutive days, the fifth test in the ninth day after the first test and the sixth test in the twenty-sixth day after the first test. The main aim of the experiment was to find relationships between route familiarity and speed choice. In particular, speed data were analyzed by considering the influence of road geometry and human factors.The main finding is that speed choice seems to be affected by route familiarity: speed increases with the repetition of travels on the same route. The particular schedule used for the tests allows to consider the influence of memory on the speed behavior of the test drivers. Moreover, some relationships between changes in speed over days, road geometry and drivers' attitudes were shown
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