Asymmetric enamine catalysis.

Asymmetric aldol reactions are a powerful method for the construction of carbon–carbon bonds in an enantioselective fashion. Historically this reaction has been performed in a stoichiometric fashion to control the various aspects of chemo-, diastereo-, regio- and enantioselectivity, however, a more atom economical approach would unite high selectivity with the use of only a catalytic amount of a chiral promoter. This critical review documents the development of direct catalytic asymmetric aldol methodologies, including organocatalytic and metal-based strategies. New methods have improved the reactivity, selectivity and substrate scope of the direct aldol reaction and enabled the synthesis of complex molecular targets (357 references).

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The Direct Catalytic Asymmetric Aldol Reaction

This Review summarizes the advances in the construction of all-carbon quaternary stereocenters via catalytic enantioselective desymmetrization of prochiral and meso-compounds, highlights the power and potential of this strategy in the total synthesis of natural products and biologically active compounds, and outlines the synthetic opportunities still available.

Catalytic Enantioselective Desymmetrization Reactions to All-Carbon Quaternary Stereocenters.

Fundamentals of materials processes wherein a reinforcing phase is combined with bulk molten metal are reviewed. Capillary phenomena which govern the incorporation of the reinforcement into the matrix are discussed first, with focus on thermodynamics, mechanics, and chemistry of wetting. Engineering strategies that have been adopted to increase reinforcement wettability are also addressed. Relevant transport phenomena are covered next, with focus on the infiltration process and the rheology of composite slurries. The last section of this review is concerned with solidification of the matrix after it has been combined with the reinforcement, including nucleation and growth of the matrix, and particle pushing by the solidifying metal. This review places emphasis on the physical phenomena that govern the processing and the microstructural development of cast metal matrix composites.

Solidification Processing Of Metal Matrix Composites

We are grateful to the Spanish Ministerio de Educacion y
Ciencia, as well as to Generalitat Valenciana and
University of Alicante, for their continuous financial
support.

Enantioselective direct aldol reaction: the blossoming of modern organocatalysis

In recent years, the SLM process has been studied for the production of aluminum alloy parts, as these alloys demonstrate significant potential for the future, notably due to their low density which allows a considerable reduction in mass. The aim of this bibliographical study is to identify and classify the parameters and phenomena which influence the appearance of defects in aluminum alloy parts produced using the SLM process and hence the final properties of these parts. To do this, a cause tree diagram was created. For each defect or consequence identified (porosities, defects linked with hot cracking phenomena, anisotropy in the material and surface quality), we revealed the potential sources of the appearance of this defect, going back to the initial causes.

Main defects observed in aluminum alloy parts produced by SLM: From causes to consequences

An investigation on thermal, metallurgical and mechanical states in weld cracking of Inconel 738LC superalloy

Benzimidazole‐pyrrolidine/H+ (BIP/H+), a Highly Reactive Organocatalyst for Asymmetric Processes

Benzoimidazole–pyrrolidine (BIP), a highly reactive chiral organocatalyst for aldol process

In recent years, technological advancements have led to the industrialization of the laser powder bed fusion process. Despite all of the advancements, quality assurance, reliability, and lack of repeatability of the laser powder bed fusion process still hinder risk-averse industries from adopting it wholeheartedly. The process-induced defects or drifts can have a detrimental effect on the quality of the final part, which could lead to catastrophic failure of the finished part. It led to the development of in situ monitoring systems to effectively monitor the process signatures during printing. Nevertheless, post-processing of the in situ data and defect detection in an automated fashion are major challenges. Nowadays, many studies have been focused on incorporating machine learning approaches to solve this problem and develop a feedback control loop system to monitor the process in real-time. In our study, we review the types of process defects that can be monitored via process signatures captured by in situ sensing devices and recent advancements in the field of data analytics for easy and automated defect detection. We also discuss the working principles of the most common in situ sensing sensors to have a better understanding of the process. Commercially available in situ monitoring devices on laser powder bed fusion systems are also reviewed. This review is inspired by the work of Grasso and Colosimo, which presented an overall review of powder bed fusion technology.

Eric Lacoste

Papers

Main defects observed in aluminum alloy parts produced by SLM: From causes to consequences

An investigation on thermal, metallurgical and mechanical states in weld cracking of Inconel 738LC superalloy

Benzimidazole‐pyrrolidine/H+ (BIP/H+), a Highly Reactive Organocatalyst for Asymmetric Processes

Benzoimidazole–pyrrolidine (BIP), a highly reactive chiral organocatalyst for aldol process

In Situ Monitoring Systems of The SLM Process: On the Need to Develop Machine Learning Models for Data Processing