Taking into account the hurdles of climate change and environmental pollution, through the years, the development of sustainable protocols in catalysis stands as a cornerstone to answer those issues. Carbon dots (CDs) have recently proven to be efficient in various types of catalysis, including photocatalytic reactions, while being a green and economic alternative for metal catalysts. In this paper, we present a new catalytic system for the photoredox functionalization of indoles and heteroarenes derivatives based on CDs as nano-photocatalysts. This reaction, based on the cooperation between our catalyst and 2,6-lutidine, shows the ability to functionalize these compounds up to 88%, it is effective on 1 mmol scale, and shows a recyclability potential at least to 5 cycles. This system also demonstrated the capacity of obtaining rare types on indoles, having two electron withdrawing groups (EWG), both on the carbon 2 (C2) and carbon 3 (C3). Furthermore, careful studies led to the partial resolution of the mechanism, and to explanations on the regioselectivity of the reaction, which has been studied through the nature of both reagents and substrates, but also through the light's wavelength used in the reaction.

Carbon dots (CDs) are privileged carbon‐based nanomaterials which they have been extensively studied in recent years in catalysis. In fact, their peculiar photoluminescence features have found applications in nanophotocatalysis as well as bioimaging and sensing. Nevertheless, their application as nanophotoredox catalysts in stereoselective transformations is still unexplored. Herein, this study reports the combination of carbon dots as nanophotocatalysts and asymmetric organocatalysis for the stereoselective α‐functionalization of aldehydes. Employing various bromo‐derivatives as alkylating agents, it achieves the corresponding enantioenriched α‐alkylated derivatives with excellent yields (up to 94%) and enantioselectivities (up to 98:2 e.r.). With a series of control experiments, cyclic voltammetry and fluorescence quenching studies, it is possible to postulate a synergistic dual catalytic cycle that involves a photo‐oxidative quenching of the excited stated of CDs paired with an enamine activation promoted by the MacMillan organocatalyst followed by radical alkylation. This study successfully demonstrates that carbon dots can efficiently replace metal‐based photocatalysts, promoting photoredox catalytic stereoselective transformations even at low concentrations (down to 0.1 mg mL −1 ), paving the way to more sustainable and possibly recyclable catalytic systems.

Carbon dots (CDs) represent an emerging class of nanomaterials that combine outstanding photoluminescent properties with low toxicity and excellent biocompatibility. These unique features have garnered significant interest for potential applications in sensing as well as nanovectors for bioactive compounds. Within this context, the possibility of synthesizing chiral carbon dots (CCDs) has paved the way for a plethora of bioapplications in their interaction with chiral biomolecules. In this study we report the synthesis and characterization of CCDs with opposite chiralities and their selective interaction with nucleic acids. A systematic study on their interaction with different oligonucleotides (ODNs) using UV-vis, photoluminescence, and circular dichroism analyses highlighted how the chiral surface of the CCDs induces distinct spectroscopic responses in CCDs-ODN conjugates. These findings establish the foundation for innovative applications of CCDs as nanosensors and nanocarriers for nucleic acids. Additionally, the antioxidant properties of CCDs were investigated, highlighting their dual potential as both sensing and preservative nanomaterials for genetic material. Our results suggest significant implications for the development of chiral-specific diagnostic tools, drug delivery systems, and therapeutic agents. Furthermore, these properties open new avenues for the use of CCDs in antibiotic residue detection, fluorescence imaging, and photodynamic therapy.

Herein, we report a photochemical organocatalytic method for the asymmetric introduction of perfluoroalkyl fragments (including the valuable trifluoromethyl moiety) at the remote γ-position of α-branched enals. The chemistry exploits the ability of extended enamines (dienamines) to form photoactive electron donor-acceptor (EDA) complexes with perfluoroalkyl iodides, which under blue light irradiation generate radicals through an electron transfer mechanism. The use of a chiral organocatalyst, derived from cis-4-hydroxy-l-proline, secures a consistently high stereocontrol while inferring complete site selectivity for the more distal γ position of the dienamines.

Photocyclization of carbonyl compounds (known as the Norrish-Yang reaction) to yield cyclobutanols is, in general, accompanied by fragmentation reactions. The latter are predominant in the case of aldehydes so that secondary cyclobutanols are not considered accessible via the straightforward Norrish-Yang reaction. A noteworthy exception has been reported in our laboratory, where cyclobutanols bearing a secondary alcohol function were observed upon UV light irradiation of 2-(hydroxyimino)aldehydes (HIAs). This reaction is here investigated in detail by combining synthesis, spectroscopic data, molecular dynamics, and DFT calculations. The synthetic methodology is generally applicable to a series of HIAs, affording the corresponding cyclobutanol oximes (CBOs) chemoselectively (i.e., without sizable fragmentation side-reactions), diastereoselectively (up to >99:1), and in good to excellent yields (up to 95%). CBO oxime ether derivatives can be purified and diastereomers isolated by standard column chromatography. The mechanistic and stereochemical picture of this photocyclization reaction, as well as of the postcyclization E/Z isomerization of the oxime double bond is completed.

A highly stereoselective procedure for the synthesis of spiro-polycyclic oxindoles bearing five contiguous stereogenic centers including two tetrasubstituted carbons has been developed. Under sequential organocatalysis performed by a pyrrolidine-based organocatalyst and DBU, a highly atom-economical Michael–domino Michael/aldol reaction sequence was optimized, yielding variously functionalized spiro-decalin oxindoles with excellent stereoselectivity (>99:1 dr, up to 92% ee).

Click chemistry is used to functionalize simple lipophilic and water-soluble molecules, a complex PEGylated phospholipid (DSPE-PEG2000), and two benzylic substrates with the 2-(hydroxyimino)aldehyde (HIA) group. To this end, two terminal alkynes bearing the HIA moiety were synthesized and coupled to different azides through copper(I)-catalyzed azide alkyne cycloaddition (CuAAC). Norrish–Yang photoisomerization (λ= 365 nm, LED source) is successfully obtained, with no interference by the triazole linker, except when the forbidden n-π* carbonyl transition is screened by a remote substituent such as salicylaldehyde. UV-Vis spectrometry suggests a specific interaction of HIAs with Cu(II), whereas no such evidence is found with Cu(I). We thereby show that the CuAAC methodology can be used successfully to obtain HIA-based UV-responsive hydrophilic or lipophilic ligands, phospholipidic components for the construction of liposomes, and macrocycle precursors.

Benzazetidines are highly strained and inherently unstable heterocycles. There are only few methodologies for assembling these compounds. Here, a protocol is presented to trap an elusive cyclic, four-membered hemiaminal structure. This method affords several benzazetidines in moderate to good yields (up to 81%), and it uses inexpensive materials and does not require catalysts based on transition metals. The high ring strain energy of these benzazetidine systems was estimated by density functional theory calculations to be about 32 kcal mol-1. This synthesis can be applied also on gram scale with reaction yield essentially unchanged.

Simple quinine as an organocatalyst mediates the addition of various naphthols to halogenated quinones to afford non-C2 -symmetrical, axially chiral biaryl products, which are promising compounds as chiral ligands and organocatalysts. The rotational barrier required to have two distinct atropisomers has been evaluated in the products generated from the addition of naphthols to various quinones by means of DFT calculations and HPLC. The use of halogenated quinones as reagents was necessary to have configurationally stable enantiomeric products which can be obtained in good yield and stereoselectivity. These compounds have also been prepared in gram quantities and recrystallized to near enantiopurity.