Extended Aromatic and Heteroaromatic Ring Systems in the Chalcone–Flavanone Molecular Switch Scaffold

Pd-Catalyzed Hydroxyl-Directed Cascade Hydroarylation/C-H Germylation of Nonterminal Alkenes and Aryl Iodides

Pd-catalyzed cascade hydroarylation and C-H germylation of nonterminal alkenes and aryl iodides enabled by hydroxyl assistance have been developed. The key step in this C-H germylation cascade is the formation of a highly reactive oxo-palladacycle intermediate, which markedly restrained the β-H elimination process. Mechanistically, control experiments indicated that the hydroxyl group played an important role in this process. This transformation shows excellent reactivity and selectivity for most substrates investigated.

Synthesis and antiproliferative activity of 6-naphthylpterocarpans

The Heck-oxyarylation of racemic 2-(1-naphthyl)- and 2-(2-naphthyl)-2H-chromene derivatives were carried out resulting diastereoselectively in (6S*,6aR*,11aR*)-6-(1-naphthyl)- and 6-(2-naphthyl)-pterocarpans as major products and bridged (6R*,12R*)-6,12-methanodibenzo[d,g][1,3]dioxocine derivatives as minor products. Antiproliferative activity of two 6-naphthylpterocarpans was identified by MTT assay against A2780 and WM35 human cancer cell lines with low micromolar IC50 values. The measured 0.80 and 3.51 μM IC50 values of the (6S*,6aR*,11aR*)-6-(1-naphthyl)pterocarpan derivative with 8,9-methylenedioxy substitution represent the best activities in the pterocarpan family. Enantiomers of the pterocarpan and dioxocine derivatives and their chiral 2-naphthylchroman-4-one and 2-naphthyl-2H-chromene precursors were separated by HPLC using chiral stationary phase. HPLC-ECD spectra were recorded and absolute configuration and low-energy solution conformations were determined by TDDFT-ECD calculations. Characteristic ECD transitions of the separated enantiomers were correlated with their absolute configuration.

[1,5]-Hydride Shift-Cyclization versus C(sp2)-H Functionalization in the Knoevenagel-Cyclization Domino Reactions of 1,4- and 1,5-Benzoxazepines

Domino cyclization reactions of N-aryl-1,4- and 1,5-benzoxazepine derivatives involving [1,5]-hydride shift or C(sp2)-H functionalization were investigated. Neuroprotective and acetylcholinesterase activities of the products were studied. Domino Knoevenagel-[1,5]-hydride shift-cyclization reaction of N-aryl-1,4-benzoxazepine derivatives with 1,3-dicarbonyl reagents having active methylene group afforded the 1,2,8,9-tetrahydro-7bH-quinolino [1,2-d][1,4]benzoxazepine scaffold with different substitution pattern. The C(sp3)-H activation step of the tertiary amine moiety occurred with complete regioselectivity and the 6-endo cyclization took place in a complete diastereoselective manner. In two cases, the enantiomers of the chiral condensed new 1,4-benzoxazepine systems were separated by chiral HPLC, HPLC-ECD spectra were recorded, and absolute configurations were determined by time-dependent density functional theory- electronic circular dichroism (TDDFT-ECD) calculations. In contrast, the analogue reaction of the regioisomeric N-aryl-1,5-benzoxazepine derivative did not follow the above mechanism but instead the Knoevenagel intermediate reacted in an SEAr reaction [C(sp2)-H functionalization] resulting in a condensed acridane derivative. The AChE inhibitory assays of the new derivatives revealed that the acridane derivative had a 6.98 μM IC50 value.

Interactions in flavanone and chalcone derivatives: Hirshfeld surface analysis, energy frameworks and global reactivity descriptors

The present study examines a series of flavanone and chalcone derivatives substituted with electron-withdrawing groups (Cl or Br) and electron-donating groups (OH, CH₃ and OCH₃), namely, 7-methoxy-2-phenyl-3,4-dihydro-2H-1-benzopyran-4-one, C₁₆H₁₄O₃, 2-(4-methoxyphenyl)-3,4-dihydro-2H-1-benzopyran-4-one, C₁₆H₁₄O₃, 2-(4-methoxyphenyl)-6-methyl-3,4-dihydro-2H-1-benzopyran-4-one, C₁₇H₁₆O₃, 2-(4-chlorophenyl)-3,4-dihydro-2H-1-benzopyran-4-one, C₁₅H₁₁ClO₂, 8-bromo-6-methyl-2-phenyl-3,4-dihydro-2H-1-benzopyran-4-one, C₁₆H₁₃BrO₂, (2E)-1-(2-hydroxyphenyl)-3-(4-methoxyphenyl)prop-2-en-1-one, C₁₆H₁₄O₃, and (2E)-1-(2-hydroxyphenyl)-3-(4-hydroxyphenyl)prop-2-en-1-one, C₁₅H₁₂O₃. It compares the two groups of derivatives with regard to their intermolecular interactions in the crystal lattice and lattice energy calculations, together with energy framework visualization and global reactivity descriptors (chemical hardness, chemical potential and electrophilicity index). It also discusses the relationships between different noncovalent interactions derived from Hirshfeld surface analysis, crystal lattice energy and global reactivity descriptors of the compounds.

Synthesis of 2-(1,2,4-oxadiazol-5-yl)-2,3-dihydro-4H-chromen-4-ones

Simple and efficient synthesis of 2-(1,2,4-oxadiazol-5-yl)-2,3-dihydro-4H-chromen-4-ones is elaborated. The method relies on CDI-mediated cyclocondensation of substituted 4-oxochromane-2-carboxylic acids and amidoximes. The protocol allows the preparation of 2-oxadiazolylchromanones decorated with two pharmacophores (2,3-dihydro-4H-chromen-4-one and 1,2,4-oxadiazole) that are in high demand in drug discovery.

Influence of spatial distribution of molecule on the switching behavior: A first-principles study

We perform first-principles calculations to investigate the electronic transport properties of chalcone and flavanone molecules sandwiched between graphene electrodes. These two molecules can be reversibly converted between open and closed states induced by pH, and the significant switching behaviors are observed. The currents and switching ratios are influenced by rotating molecules around the [Formula: see text] axis, which are discussed by the transmission eigenstates, electrostatic potential distributions and transmission spectra. The observed negative differential resistance effect is explained in chalcone configuration. The results suggest that spatial distributions of molecules will influence the performance of devices, indicating a potential application in future molecular circuits.