The structure transformation of Mg-CUK-1 due to the confinement of H₂O molecules was investigated. Powder X-ray diffraction (PXRD) patterns were collected at different H₂O loadings and the cell parameters of the H₂O-loaded Mg-CUK-1 material were determined by the Le Bail strategy refinements. A bottleneck effect was observed when one hydrogen-bonded H₂O molecule per unit cell (18% relative humidity (RH)) was confined within Mg-CUK-1, confirming the increase in the CO₂ capture for Mg-CUK-1.

A diversity-oriented synthesis (DOS) of two new polyheterocyclic compounds was performed via an Ugi-Zhu/cascade (N-acylation/aza Diels-Alder cycloaddition/decarboxylation/dehydration)/click strategy, both step-by-step to optimize all involved experimental stages, and in one pot manner to evaluate the scope and sustainability of this polyheterocyclic-focused synthetic strategy. In both ways, the yields were excellent, considering the high number of bonds formed with release of only one carbon dioxide and two molecules of water. The Ugi-Zhu reaction was carried out using the 4-formylbenzonitrile as orthogonal reagent, where the formyl group was first transformed into the pyrrolo[3,4-b]pyridin-5-one core, and then the remaining nitrile group was further converted into two different nitrogen-containing polyheterocycles, both via click-type cycloadditions. The first one used sodium azide to obtain the corresponding 5-substituted-1H-tetrazolyl-pyrrolo[3,4-b]pyridin-5-one, and the second one with dicyandiamide to synthesize the 2,4-diamino-1,3,5-triazine-pyrrolo[3,4-b]pyridin-5-one. Both synthesized compounds may be used for further in vitro and in silico studies because they contain more than two heterocyclic moieties of high interest in medicinal chemistry, as well as in optics due to their high π-conjugation.

The synthesis and characterization of one symmetrical bis-1-substituted-1H-tetrazole (69%) via a Huisgen-type 1,3-dipolar cycloaddition, as well as, one symmetrical aza-linked bis-5-substituted-1H-tetrazole (57%) via a classic Huisgen 1,3-dipolar cycloaddition followed by a reductive aza-coupling under greener reaction conditions are described. The main reason behind these tetrazole-based ligands is to construct novel Metal-Organic Framework (MOF) architectures to evaluate their CO₂ capture properties under relative humidity conditions. It is worthy to note that both herein reported products have not been synthesized nor isolated, anywhere. Besides, the synthesis of new ligands to fabricate novel MOFs with potential application in environmental remediation has become a highly valued field of opportunity for synthetic chemists and materials engineers.

A one-pot synthetic methodology that combines an Ugi-Zhu three-component reaction (UZ-3CR) with a cascade sequence (intermolecular aza Diels–Alder cycloaddition/intramolecular N-acylation/decarboxylation/dehydration) using microwave-heating conditions, ytterbium (III) triflate (Yb(OTf)₃) as the catalyst, and chlorobenzene (for the first time in a multi-component reaction (MCR)) as the solvent, was developed to synthesize twelve new fluorinated-pyrrolo[3,4-b]pyridin-5-ones containing a 4-amino-7-chloroquinoline moiety, yielding 50–77% in 95 min per product, with associated atom economies around 88%, also per product. Additionally, by in vitro tests, compounds 19d and 19i were found to effectively stop early SARS-CoV-2 replication, IC₅₀ = 6.74 µM and 5.29 µM, at 0 h and 1 h respectively, while cell viability remained above 90% relative to the control vehicle at 10 µM. Additional computer-based studies revealed that the most active compounds formed strong favorable interactions with important viral proteins (M_pro, NTDα and NTDo) of coronavirus, supporting a two-pronged approach that affects both how the virus infects the cells and how it replicates its genetic material. Finally, quantum chemistry analyses of non-covalent interactions were performed from Density-Functional Theory (DFT) to better understand how the active compounds hit the virus.

The synthesis and characterization of three new bis 1-substituted 1H-tetrazoles are described. Two products were synthesized in a single step via a direct heterocyclization of primary amines, methyl orthoester (trymethyl orthoformate), and sodium azide in 30% and 91% yields, respectively. Besides, another one was prepared via a three-step synthetic strategy: S_NAr (32%), nitro-group reduction (66%), and primary amine heterocyclization (83%), yielding 18%, overall. The aim behind the synthesis of new tetrazole-containing products is to construct novel MOF-like structures to evaluate their gas capture properties (CO₂, CO, and SO₂) under relative humidity conditions.

The new bis-heterocyclic compound ferrocenyl-bis-(1-(4-benzyl-5-morpholinooxazol-2-yl)-N-(4-(trifluoromethyl)benzyl)methanamine) (1) was synthesized in 73% overall yield in 1.5 hours via a pseudo-repetitive Ugi-Zhu five-component reaction, starting from 1,1′-ferrocenedicarboxaldehyde, 4-(trifluoromethyl)benzylamine, and 2-isocyano-1-morpholino-3-phenylpropan-1-one, in 1:2.1:2.2 proportions, respectively, using scandium(III) triflate as a Lewis-acid catalyst, microwaves as a heat source, and toluene as a solvent. The synthesized compound was characterized by 1D (¹H, ¹³C, and ¹⁹F) and 2D (COSY, HSQC, and HMBC) NMR, HRMS, and FT-IR.