Herein, an overview of the most important developments and concepts related to the 1,6-conjugate addition reactions are reviewed. 1 Introduction 2 Transition-Metal-Catalyzed 1,6-Conjugate Additions 2.1 Copper-Mediated Reactions 2.2 Iron-Mediated Reactions 2.3 Rhodium- and Iridium-Mediated Reactions 3 Organocatalyzed 1,6-Conjugate Additions 4 Other Methods 5 Conclusions

This review provides a comprehensive compilation of available literature concerning the synthesis of 1,2-dihydropyridines. The most important recent developments and concepts re­lated to this topic are emphasised. 1 Introduction 2 Synthesis of 1,2-Dihydropyridines 2.1 Condensation Reactions 2.2 Reduction of Pyridines and Pyridinium Salts 2.3 Nucleophilic Addition to Pyridines and Pyridinium Salts 2.4 Pericyclic Reactions 2.5 Other Methods 3 Conclusions

The analysis and interpretation of data retrieved from Oxygen Radical Absorbance Capacity (ORAC) assays represent a challenging task. ORAC indexes originate from different mathematical approaches often lacking correct elucidation of kinetic features concerning radical scavenging reactions by antioxidant compounds. In this work, the expression of ORAC values as area under fluorescein (FL) decay curves (AUC) and lag time are critically compared. This multi-parametric analysis showed the extension of radical scavenging reactions beyond the lag time period for caffeic acid, gallic acid, reduced glutathione and quercetin, extending their antioxidant protection of FL. Ethanol delayed the reaction of both FL and antioxidant compounds with free radical species generated from 2,2′-azobis(2-amidinopropane) dihydrochloride thermolysis. Trolox equivalent values, commonly used to express ORAC values, were more affected by the differences in radical scavenging kinetics between the reference and the tested antioxidant compounds when calculated from AUC than from lag time. These findings stressed the importance of choosing calibrator compounds presenting ORAC kinetics similar to samples to prevent biased estimation of the antioxidant capacity. Additionally, the framework proposed here provides a sustainable analytical method for the evaluation of antioxidant capacity, with an AGREE score of 0.73.

The Diels–Alder reaction of 1,2-dihydropyridines with different dienophiles is a well-established and straightforward method for the synthesis of isoquinuclidines. Nevertheless, the enantioselective preparation of isoquinuclidines using organocatalysts or organometallic catalysts is rather unexplored. This succinct review offers readers an overall perspective of the most important recent developments and concepts related to this topic.1 Introduction2 Asymmetric Diels–Alder Reaction of 1,2-Dihydropyridines2.1 Transition-Metal-Catalyzed Reactions2.2 Organocatalyzed Reactions3 Diels–Alder Reaction of 1,2-Dihydropyridines in the Synthesis of Biologically Valuable Compounds4 Conclusion