The flavonoid quercetin (3,3′,4′,5,7-pentahydroxyflavone) is widely distributed in plants, foods, and beverages. This polyphenol compound exhibits varied biological actions such as antioxidant, radical-scavenging, anti-inflammatory, antibacterial, antiviral, gastroprotective, immune-modulator, and finds also application in the treatment of obesity, cardiovascular diseases and diabetes. Besides, quercetin can prevent neurological disorders and exerts protection against mitochondrial damages. Various in vitro studies have assessed the anticancer effects of quercetin, although there are no conclusive data regarding its mode of action. However, low bioavailability, poor aqueous solubility as well as rapid body clearance, fast metabolism and enzymatic degradation hamper the use of quercetin as therapeutic agent, so intense research efforts have been focused on the modification of the quercetin scaffold to obtain analogs with potentially improved properties for clinical applications. This review gives an overview of the developments in the synthesis and anticancer-related activities of quercetin derivatives reported from 2012 to 2016.

Chemistry in continuous-flow continues to attract attention from the community of synthetic organic chemists due to its now well-recognized benefits including, inter alia, quick reaction times, operational safety, rapid reaction screening/optimization, enhanced automation with possible addition of in-line reaction analysis, and easy scalability. Coupling of flow chemistry to enabling technologies (e.g. unconventional solvents, supported reagents or catalysts, microwave irradiation, photochemistry, inductive heating, microreactors) as well as to additive manufacturing (AM) technologies (i.e. 3D printing) gives additional advantages for throughput and automation, and besides this, unique opportunities are offered by compartmentalization, that allows multistep syntheses to occur reconciling incompatible reaction conditions. Based on all this, continuous-flow may itself be seen as an enabling technology which leads in the direction of process intensification meeting increasingly pressing sustainability issues (e.g. waste minimization, cost/energy reduction). As part of flow chemistry, organocatalysis represents an active research area under which there is large opportunity for re-optimizing long-standing reactions or inventing new transformations. Both homogeneous (soluble) and heterogeneous (insoluble) organic molecules have been used as catalysts for continuous-flow processing in either achiral or asymmetric fashion, any issue inherent to a homogeneous approach (high catalyst loading, difficult catalyst separation) being typically overcome with the use of heterogenized organocatalysts. This review is aimed at covering the progresses on organocatalysis in continuous-flow from 2016 to early 2020, with special attention paid to the comparison between batch and flow processes for each discussed transformation to substantiate the potential of flow technology for process intensification.

The application of the oxidative system composed of a heterogeneous triazolium pre-catalyst, iron(II) phthalocyanine and air is described for the selective conversion of 5-hydroxymethylfurfural (HMF) into the added-value 5-hydroxymethyl-2-furancarboxylic acid (HMFCA). The disclosed one-pot two-step procedure involved sequential oxidative esterifications of HMF to afford a polyester oligomer having hydroxyl and carboxyl terminal groups (M_w = 389–1258), which in turn was hydrolyzed by a supported base (Ambersep 900 OH) to yield HMFCA in 87% overall yield. The same strategy was adopted for the effective synthesis of ester and amide derivatives of HMFCA by nucleophilic depolymerization of the oligomeric intermediate with methanol and butylamine, respectively. The utilization of the disclosed oxidative system for the direct conversion of HMF and furfural into their corresponding ester, amide, and thioester derivatives is also reported.

N‐Heterocyclic carbene (NHC) catalysis is a by now consolidated organocatalytic platform for a number of synthetic (asymmetric) transformations via diverse reaction modes/intermediates. In addition to the typicalumpolungprocesses involving acyl anion/homoenolate equivalent species, implementation of protocols under oxidative conditions greatly expands the possibilities of this methodology. Oxidative NHC‐catalysis allows for oxidative and oxygenative transformations through specific manipulations of Breslow‐type species depending upon the oxidant used (external oxidant or O₂/air), the derived NHC‐bound intermediates paving the way to non‐umpolungprocesses through activation of carbon atoms and heteroatoms. This review is intended to update the state of the art in oxidative NHC‐catalyzed reactions that appeared in the literature from 2014 to present, with a strong focus to crucial intermediates and their mechanistic implications.

N-Heterocyclic carbenes (NHCs) are now well-established organocatalysts for a large number of asymmetric and non-asymmetric transformations. In the last 15 years, there has been significant interest in using NHCs in kinetic resolution (KR), dynamic kinetic resolution (DKR) and asymmetric desymmetrization reactions for the stereoselective synthesis of enantioenriched compounds, with diverse substrates and activation modes being adopted to this end. This short review brings into focus the progress made on NHC-catalyzed KR, DKR, and asymmetric desymmetrization from 2004 until December 2018. The literature discussed in this article is classified on the basis of the type of reaction involving the NHC catalyst.1 Introduction2 Acylation Strategies2.1 O-Acylation2.2 N-Acylation2.3 C-Acylation3 Aldol-Acylation Processes4 Benzoin Reactions5 Stetter Reactions6 Miscellaneous Approaches7 Conclusion