The use of small organic molecules as catalysts has gained increasing importance recently. These substances, the so-called organocatalysts, present a lot of advantages, like being less toxic, less polluting, and more economically viable than the organometallic catalysts that dominate asymmetric synthesis. This work intends to briefly show some classic works and recent publications, explaining the advantages of organocatalysis and the different types of compounds used in this field, as well as their course of action.

para‐Quinone methides (p‐QMs) are naturally occurring molecules that have been finding increasing synthetic applications in the last few years. The presence of two electronically different exocyclic conjugate substituents in their structure, carbonyl and methylidene, leads to a pronounced reactivity owing to the polarization of the molecule. In this sense, those are prone to undergo the attack of nucleophiles in the terminal carbon exocyclic double bond, behaving as vinylogous electrophiles and generating 1,6‐addition products. In this context, in the last few years the development of catalytic approaches for 1,6‐nucleophilic addition reactions involving p‐QMs has attracted considerable attention. Considering the extensive applications that such molecules have found in the last decades in 1,6‐addition reactions, in this review we comprehensively discuss the historical development of this field, starting with early approaches on natural product synthesis, going through seminal non‐stereoselective processes and progressing to cutting‐edge asymmetric‐catalyzed approaches.

Carbene transfer reactions are very important transformations in organic synthesis, allowing the generation of structurally challenging products by catalysed cyclopropanation, cyclopropenation, carbene C-H, N-H, O-H, S-H, and Si-H insertion, and olefination of carbonyl compounds. In particular, chiral and achiral metalloporphyrins have been successfully explored as biomimetic catalysts for these carbene transfer reactions under both homogeneous and heterogeneous conditions. In this work the use of synthetic metalloporphyrins (MPorph, M = Fe, Ru, Os, Co, Rh, Ir, Sn) as homogeneous or heterogeneous catalysts for carbene transfer reactions in the last years is reviewed, almost exclusively focused on the literature since the year 2010, except when reference to older publications was deemed to be crucial.

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Simple methodologies giving access to a new series of pophyrin/4-quinolone conjugates 6 and to the corresponding intracyclized derivatives 8 are described. The key steps to obtain 6 involved palladium-catalyzed amination reactions of 6bromo-4-quinolones containing N-ethyl, N-pentyl and N-ribofuransyl substituents with (2-amino-5,10,15,20tetraphenylporphyrinato)nickel(II) followed by demetallation. Compounds 8 were obtained from compounds 4, the nickel(II) complexes of 6, by an oxidative intracylization approach. The new conjugates were fully characterized and the evaluation of singlet oxygen production showed that these compounds possess good to high capability to generate singlet oxygen. The efficacy of these derivatives to photoinactivate Staphylococcus aureus, a Gram-positive bacteria, was evaluated and the best results were obtained with the N-ethyl derivatives 8a and 6a. Results and discussion Synthesis of porphyrin/4-quinolone conjugatesThe synthetic strategy to obtain the new porphyrin/4quinolone conjugates 6 and 8 involved the experimental work