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Tetrahydropyridazines are of particular interest for their versatility as intermediates in organic synthesis and display pharmacological activity in several domains. Here, we describe the photocatalytic synthesis of different tetrahydropyridazines starting from γ,δ-unsaturated N-arylsulfonylhydrazones. Simple structural changes of substrates result into three different pathways beginning from a common N-hydrazonyl radical, which evolves through a domino carboamination/dearomatization, a HAT process, or a photoinduced radical Smiles rearrangement to afford diverse tetrahydropyridazines. All reactions are carried out in very mild conditions, and the quite inexpensive [Ru(bpy)3]Cl2 is used as the catalyst. Preliminary mechanism studies are presented, among them luminescence and electrochemical characterization of the involved species. Computational studies allow to rationalize the mechanism in accord with the experimental findings.

This review aims to summarize the development of the chemistry of π-allylpalladium complexes both as intermediates and catalysts/reagents between 2013 and early 2109. Major attention has been devoted to the synthetic aspect of these versatile intermediates.1 Introduction2 π-Allylpalladium Complexes Generated from Allyl Electrophiles2.1 Activated Allylic Compounds2.2 Unactivated Allylic Compounds: Allylic Alcohols and Hydrocarbons2.3 Total Syntheses3 π-Allylpalladium Complexes Generated from Dienes3.1 Conjugated Dienes3.2 Allenes4 π-Allylpalladium Complexes Exploited as Reactants and Precatalysts4.1 Allylpalladium-Catalyzed Dehydrogenation4.2 Allylpalladium-Catalyzed Synthesis of Alkenylboronic Esters4.3 Allylpalladium-Based Precatalysts5 Conclusions

An unprecedented efficient palladium(0)-catalyzed reaction of vinyl oxiranes with N-tosylhydrazones, affording "skipped" allylic alcohols in total regioselectivity and stereoselectivity, with excellent functional-group compatibility, is reported. In this Tsuji-Trost-like allylation, we propose the use of N-tosylhydrazones as a synthetic equivalent of α-styryl anions. More than 20 new products are described, including naturally occurring derivatives. A catalytic system involving an iodide (I

Palladium(0)-catalysed hydro-alkylation or -alkenylation of alkoxyallenes with N-tosylhydrazones gives direct access to conjugated and skipped 1-alkoxydienes with high efficiency and excellent functional-group compatibility. The reaction is proposed to involve the in situ-formed t-butanol as proton source in the key step of the allylpalladium(II) species generation. Moreover, lithium iodide or iodobenzene are employed as an unprecedented iodide (I- ) reservoir to sustain the catalytic cycle.

Polycyclic molecules featuring all-carbon quaternary bridgehead centers were synthesized through domino cyclizations between N-tosylhydrazones and boronic acids. Variations of the general cascade have been applied for the preparation of 3-quinuclidinones and related alkaloid-like scaffolds through transannular heterocyclizations. Moreover, the employment of 3-cyanopropyl and 4-cyanobutylboronic acids and α,β-unsaturated N-tosylhydrazones led to spirocycles through unprecedented formal [n+1] cyclizations, including the stereoselective spirocyclization of the Hajos-Parrish ketone. The common feature of all the new reactions described is the creation of an all-carbon quaternary center by formation of two Csp3 -C bonds on the hydrazonic carbon atom. DFT-based calculations suggested the occurrence of cascade processes, which involve a diazo compound carboborylation followed by a 1,3-borotropic rearrangement on an intermediate allylboronic acid and a novel bora-aza-ene cyclization.

Curcumin is currently being investigated for its capacity to treat many types of cancer and to prevent the neuron damage that is observed in Alzheimer’s disease (AD). However, its clinical use is limited by its low stability and solubility in aqueous solutions. In this study, we propose a completely new class of boronated monocarbonyl analogues of Curcumin (BMAC, 6a-c), in which a carbonyl group replaces the Curcumin β-diketone functionality, and an ortho-carborane, an icosahedral boron cluster, substitutes one of the two phenolic rings. BMAC antitumor activity against MCF7 and OVCAR-3 cell lines was assessed in vitro and compared to that of Curcumin and the corresponding MAC derivative. BMAC 6a-c showed efficiencies that are comparable to that of MAC and superior to that of Curcumin in both the cell lines. Moreover, the inhibition of the formation of β-amyloid aggregates by BMAC 6a-c was evaluated and it was shown that compound 6c, which contains two OH moieties, has a better efficiency than Curcumin. The presence of a second –OH group can enhance the compound’s binding efficacy with β-amyloid aggregates. For the future, the presence of at least one carborane group means that the BMAC antitumor effect can be coupled with Boron Neutron Capture Therapy.

The reactivity of metalated alkoxy-1,3-dienes and α-aryl-N-phenylnitrones in the presence of LIC-KOR base, equimolar mixture of alkyllithium (LIC) and potassium alcoxides (KOR), (Schlosser, 1994) [1] has been studied. A cascade reaction involving a E1cb process stereoselectively affords ethoxy-N-phenyl-1-arylpenta-2,4-dien-1-imines. Their acidic hydrolysis allows the synthesis of peptidomimetic 5-aryl-5-phenylaminocyclopentenones in good yields.

The reactivity of metalated alkoxy-1,3-dienes and α-aryl-N-phenylnitrones in the presence of LIC-KOR base, equimolar mixture of alkyllithium (LIC) and potassium alcoxides (KOR), (Schlosser, 1994) [1] has been studied. A cascade reaction involving a E1cb process stereoselectively affords ethoxy-N-phenyl-1-arylpenta-2,4-dien-1-imines. Their acidic hydrolysis allows the synthesis of peptidomimetic 5-aryl-5-phenylaminocyclopentenones in good yields.