87 research outputs found
Recent Progresses in the Catalytic Stereoselective Dearomatization of Pyridines
1,2- and 1,4-dihydropyridines and N-substituted 2-pyridones are very important structural motifs due to their synthetic versatility and vast presence in a variety of alkaloids and bioactive molecules. In this article, we gather and summarize the catalytic and stereoselective synthesis of partially hydrogenated pyridines and pyridones via the dearomative reactions of pyridine derivatives up to mid-2023. The material is fundamentally organized according to the type of reactivity (electrophilic/nucleophilic) of the pyridine nucleus. The material is further sub-divided taking into account the nucleophilic species when dealing with electrophilic pyridines and considering the reactivity manifold of pyridine derivatives behaving as nucleophiles at the nitrogen site. The latter more recent approach allows for an unconventional entry to chiral N-substituted 2- and 4-pyridones in non-racemic form
Regio- and Stereodivergent Allylic Reductions of Bicyclic Piperidine Enecarbamate Derivatives
The
particular nature of tetrahydropyrido[4,3-e]-1,4,2-dioxazines of type 1 allows the regio-
and stereoselective obtainment of substituted N-carbamoyl
tetrahydropyridines by common reducing agents. A completely
novel, biologically active, bicyclic 1,3-diaza-4-oxa-[3.3.1]-nonene
scaffold can be generated by the use of lithium triethylborohydride
through unprecedented cascade syn-SN2′
reduction/carbamate reduction/cyclization reactions. The remarkable
regioselectivity switches in the allylic reduction process have been
rationalized with the aid of computational studies
Copper-Catalyzed Ring-Opening Reactions of Alkyl Aziridines with B2pin2: Experimental and Computational Studies
The possibility to form new C–B bonds with aziridines using diboron derivatives continues to be a particularly challenging field in view of the direct preparation of functionalized β-aminoboronates, which are important compounds in drug discovery, being a bioisostere of β-aminoacids. We now report experimental and computational data that allows the individuation of the structural requisites and of reaction conditions necessary to open alkyl aziridines using bis(pinacolate)diboron (B2pin2) in a regioselective nucleophilic addition reaction under copper catalysis
New Coumarin Dipicolinate Europium Complexes with a Rich Chemical Speciation and Tunable Luminescence
Europium (III) luminescent chelates possess intrinsic photophysical properties that are
extremely useful in a wide range of applications. The lack of examples of coumarin‐based lantha‐
nide complexes is mainly due to poor photo‐sensitization attempts. However, with the appeal of
using such a versatile scaffold as antenna, especially in the development of responsive molecular
probes, it is worth the effort to research new structural motifs. In this work, we present a series of
two new tris coumarin‐dipicolinate europium (III) complexes, specifically tailored to be either a
mono or a dual emitter, tuning their properties with a simple chemical modification. We also en‐
countered a rich chemical speciation in solution, studied in detail by means of paramagnetic NMR
and emission spectroscopy
New 1,3-Disubstituted Benzo[h]Isoquinoline Cyclen-Based Ligand Platform: Synthesis, Eu3+ Multiphoton Sensitization and Imaging Applications
The development of lanthanide-based luminescent probes with a long emission lifetime has the potential to revolutionize imaging-based diagnostic techniques. By a rational design strategy taking advantage of computational predictions, a novel, water-soluble Eu3+ complex from a cyclen-based ligand bearing 1,3-disubstituted benzo[h]isoquinoline arms was realized. The ligand has been obtained overcoming the lack of reactivity of position 3 of the isoquinoline moiety. Notably, steric hindrance of the heteroaromatic chromophore allowed selective and stoichiometry-controlled insertion of two or three antennas on the cyclen platform without any protection strategy. The complex bears a fourth heptanoic arm for easy conjugation to biomolecules. This new chromophore allowed the sensitization of the metal center either with one or two photons excitation. The suitability as a luminescent bioprobe was validated by imaging BMI1 oncomarker in lung carcinoma cells following an established immunofluorescence approach. The use of a conventional epifluorescence microscope equipped with a linear structured illumination module disclosed a simple and inexpensive way to image confocally Ln-bioprobes by single photon excitation in the 350–400 nm window, where ordinary confocal systems have no excitation sources
- …