C3-Symmetric Luminescent Diketone with Amido-Linkage as a Polymorphic Fluorescence Emitter.

The study introduces a novel C3-symmetric ß-diketone compound, BTA-D3, and its monomeric counterpart, D, with a focus on their synthetic procedure, photophysical properties and aggregation behavior. Both compounds exhibit characteristic absorption and weak fluorescence in solution, with BTA-D3 displaying higher absorption coefficients due to its larger number of diketone units. Density Functional Theory (DFT) calculations suggest increased co-planarity of diketone groups in BTA-D3. A significant finding is the Aggregation-Induced Emission (AIE) property of BTA-D3, as its fluorescence intensity increases dramatically when exposed to specific solvent ratios. The AIE behavior is attributed to intermolecular excitonic interaction between BTA-D3 molecules in self-organized aggregates. We also studied fluorescence anisotropy of BTA-D3 and D. Despite its larger size, BTA-D3 showed reduced anisotropy values because of efficient intramolecular energy migration among three diketone units. Furthermore, BTA-D3 demonstrates unique polymorphism, yielding different emission colors and structures depending on the solvent used. A unique approach is presented for promoting the growth of self-organized aggregate structures via solvent evaporation, leading to distinct fluorescence properties. This research contributes to the understanding of C3-symmetric structural molecules and provides insights into strategies for controlling molecular alignment to achieve diverse fluorescence coloration in molecular materials.

Synthetic Utilization of 2H-Heptafluoropropane: Ionic 1,4-Addition to Electron-Deficient Carbon-Carbon Unsaturated Bonds.

We have found a novel method for introducing heptafluoro-2-propyl CF(CF3)2 groups into carbon-carbon unsaturated bonds via a nucleophilic reaction using 2H-heptafluoropropane as the source of CF(CF3)2 groups. The reaction involves the nucleophilic addition of a heptafluoro-2-propyl anion, generated by treating 2H-heptafluoropropane with a fluoride ion, to various electron-deficient unsaturated compounds. This allows the easy synthesis of various aliphatic compounds containing heptafluoro-2-propyl groups.

Intramolecular cyclization reactions of arylpropargyl amides of electron-deficient α,ß-alkenyl carboxylates and related compounds.

Intramolecular cyclization reactions of arylpropargyl amides of electron-deficient α,ß-alkenyl carboxylates such as fumarates and ethenetricarboxylates were investigated. The reaction of the fumaramides with a base, Et3N or DBU in xylenes at 140 °C under air gave benz[f]isoindoline derivatives in 21-63% yields. The benz[f]isoindolines may be produced via the formation of an allenic intermediate, intramolecular Diels-Alder reaction, proton transfer, and dehydrogenation by oxygen. The suitable bases and the product yields depend on the substituents on the benzene ring. On the other hand, the reaction of the amides of fumarate and ethenetricarboxylate by heating in DMSO gave aroyl-substituted pyrrolidine derivatives as major products, probably via addition of water under metal-free conditions. Furthermore, cyclization reactions of H and Me substituted alkyne derivatives were investigated for comparison. The selective formation of various types of products, such as ethyl 2-(1-benzyl-4-formyl-2-oxopyrrolidin-3-yl)acetate and diethyl 2-(1-benzyl-2-oxo-4-vinylidenepyrrolidin-3-yl)malonate, was found, depending upon the alkyne substituents and the reaction conditions. The reaction mechanisms have been discussed using density functional theory (DFT) calculations.

Intramolecular Diels-Alder Reactions of α-Bromostyrene-Functionalized Unsaturated Carboxamides.

Intramolecular cycloaddition reactions of α-bromostyrene-functionalized amides of monomethyl fumarate were investigated. The reaction of the amides with Et3N in toluene at 110 °C gave 1,4-dihydronaphthalenes. The 1,4-dihydronaphthalenes may be produced via the intramolecular Diels-Alder reaction, proton transfer, and dehydrobromination by a base, along with C═C bond isomerization by proton transfer. The reaction of amide derivatives with halogen on a benzene ring and alkali metal carbonates in toluene at 110 °C gave naphthalene derivatives directly. Dehydrogenation of various 1,4-dihydronaphthalenes with cesium or rubidium carbonate in toluene at 110 °C gave naphthalene derivatives. The retardation by TEMPO, acceleration by air for some substrates, and density functional theory calculations suggest a radical mechanism caused by intervention of molecular oxygen.

Curcumin Derivatives Verify the Essentiality of ROS Upregulation in Tumor Suppression.

BACKGROUND: Curcumin has been shown to exert pleiotropic biological effects, including anti-tumorigenic activity. We previously showed that curcumin controls reactive oxygen species (ROS) levels through the ROS metabolic enzymes, to prevent tumor cell growth. In this study, we synthesized 39 novel curcumin derivatives and examined their anti-proliferative and anti-tumorigenic properties. METHODS AND RESULTS: Thirty-nine derivatives exhibited anti-proliferative activity toward human cancer cell lines, including CML-derived K562 leukemic cells, in a manner sensitive to an antioxidant, N-acetyl-cysteine (NAC). Some compounds exhibited lower GI50 values than curcumin, some efficiently induced cell senescence, and others markedly increased ROS levels, efficiently induced cell death and suppressed tumor formation in a xenograft mouse model, without any detectable side effects. A clustering analysis of the selected compounds and their measurement variables revealed that anti-tumorigenic activity was most well-correlated with an increase in ROS levels. Pulldown assays and a molecular docking analysis showed that curcumin derivatives competed with co-enzymes to bind to the respective ROS metabolic enzymes and inhibited their enzymatic activities. CONCLUSIONS: The analysis of novel curcumin derivatives established the importance of ROS upregulation in suppression of tumorigenesis, and these compounds are potentially useful for the development of an anti-cancer drug with few side effects.

Site-Selective Conversion of Azido Groups at Carbonyl α-Positions to Diazo Groups in Diazido and Triazido Compounds.

This paper reports on the selective conversion of alkyl azido groups at the carbonyl α-position to diazo compounds. Through ß-elimination of dinitrogen, followed by hydrazone formation/decomposition, α-azidocarbonyl moieties were transformed into α-diazo carbonyl groups in one step. As these reaction conditions do not involve aryl or general alkyl azides, site-selective conversions of di- and triazides were achieved. Through this method, the successive site-selective conjugation of the triazido molecule with three different components is demonstrated.

Nitrosoallene-Mediated endo-Cyclizations for the Synthesis of (Hetero)cyclic α-Substituted exo-Unsaturated Oximes.

Nitrosoallene-mediated endo-dig cyclization reactions producing (hetero)cyclic exo-unsaturated oximes (enoximes) are described. The intramolecular 1,4-type addition to in situ generated nitrosoallenes afforded α-substituted cyclic enoximes with exo-methylene units, which are the favored conformation for further cyclizations. The strong electron-withdrawing ability of the nitroso group facilitated the construction of five-to-seven-membered ring systems via C-O, C-N, C-S, and C-C bond formations, including a quaternary carbon center, at low temperatures.

Synthesis, photophysical properties, and photodynamic activity of positional isomers of TFPP-glucose conjugates.

The synthesis and characterization of a 'complete set' of positional isomers of tetrakis(perfluorophenyl)porphyrins (TFPP)-glucose conjugates (1OH, 2OH, 3OH, 4OH, and 6OH) are reported herein. The cellular uptake and photocytotoxicity of these conjugates were examined in order to investigate the influence of location of the TFPP moiety on the d-glucose molecule on the biological activity of the conjugates. An In vitro biological evaluation revealed that the certain of these isomers have a greater effect on cellular uptake and cytotoxicity than others. The TFPP-glucose conjugates 1OH, 3OH, and 4OH were found to exert exceptional photocytotoxicity in several types of cancer cells compared to 2OH and 6OH substituted isomers.

Arene-Inserted Extended Germa[n]pericyclynes: Synthesis, Structure, and Phosphorescence Properties.

This report describes the synthesis and characterization of arene-inserted extended (ArEx) germa[n]pericyclynes composed of germanium and 1,4-diethynylbenzene units. These novel cyclic germanium-π unit materials were synthesized with diethynylbenzene and germanium dichloride. X-ray crystallographic analysis revealed their structures, and the planar conformation of ArEx germa[4]pericyclyne along with the regular aromatic rings. UV/Vis absorption spectra and fluorescence emission spectra showed considerably unique and highly improved character compared to previously reported germa[n]pericyclynes. Even in the absence of transition metal components, phosphorescence emissions were observed, and the emission lifetimes were dramatically improved. ArEx germa[n]pericyclynes showed high photoluminescence quantum yields, whereas low photoluminescence quantum yields were observed for acyclic compounds. Density functional theory calculations show delocalized orbitals between skipped alkyne units through a germanium tether, and an increase in the HOMO energy level, leading to a small HOMO-LUMO energy gap.

Formal [3+2] Cycloaddition of Nitrosoallenes with Carbonyl and Nitrile Compounds to Form Functional Cyclic Nitrones.

The synthesis of functional cyclic nitrones via [3+2] cycloadditions of allenamide-derived nitrosoallenes with carbonyl/nitrile compounds, including ketones, esters, and nitriles, is presented herein. Rapid carbon-carbon, carbon-oxygen, and carbon-nitrogen bond formations were achieved with in situ prepared nitrosoallenes, and densely substituted oxacyclic and carbocyclic nitrones containing tetrasubstituted carbon centers were successfully synthesized. The spirocyclic nitrone products synthesized from cyclic dicarbonyl compounds underwent the unique skeletal rearrangements to cyclic α-ketonitrones.

Synthesis of α-Substituted Enoximes with Nucleophiles via Nitrosoallenes.

This paper reports nitrosoallene-mediated synthesis of α-substituted enoximes. Nucleophilic substitution of nitrosoallenes, a novel chemical species prepared from allenyl N-hydroxysulfonamides, afforded α-functionalized enoximes. Introduction of various nucleophiles proceeded smoothly to form C-N, C-O, C-S, C-F, and C-C bonds in the presence of azodicarboxylates.

Accessible protocol for asymmetric hydroformylation of vinylarenes using formaldehyde.

We report herein on an accessible protocol for the asymmetric hydroformylation of vinylarenes using formaldehyde as a substitute for syngas. The regioselectivity (branched/linear = up to 96/4) and enantioselectivity (up to 95% ee) can be attributed to the use of chiral Ph-bpe as a ligand.

Diastereoselective [2 + 2] photocycloaddition of cyclohexenone derivative with olefins in supercritical carbon dioxide.

We performed diastereoselective [2 + 2] photocycloaddition of the cyclohexenone derivative with olefins in supercritical carbon dioxide (scCO2). A dramatic enhancement of conversion was observed at around critical density when ethylene gas was employed as a coupling partner. Furthermore, we elucidated that the pressure dependence of the diastereomeric excess (de) was discontinuous at critical density owing to the difference of substrate solubility between near-critical carbon dioxide (ncCO2) and scCO2; both the reaction conversion and de values obtained were lower than those in conventional organic solvent. On the contrary, when cyclopentene (liquid) was utilized as a coupling partner, moderate conversion was always observed irrespective of CO2 pressure, because the substrate could be dissolved in cyclopentene. Furthermore, we could accomplish de enhancement in scCO2, in particular around critical density, compared to that in organic solvent. This highly selective photoreaction is due to the unique solvent property of scCO2, which is called the clustering effect.

Diastereoselective [2+2] photocycloaddition of chiral cyclic enones with olefins in aqueous media using surfactants.

We conducted diastereodifferentiating [2+2] photocycloadditions of cyclo-hexenones modified with a chiral 8-(p-methoxy phenyl)menthyl auxiliary with olefins in water. Although the photoreaction didn't proceed at all in pure water owing to very low solubility, the use of surfactants [sodium dodecyl sulfate (SDS) or dodecylamine hydrochloride (DAH)] and additive (organic solvent) enabled the reactions to progress with moderate to high conversions and yields. Furthermore, we synthesized a new menthol derivative substrate containing a (p-octyloxy)phenyl group for enhancing hydrophobicity, and elucidated that this new substrate was found to be a suitable chiral auxiliary in this asymmetric photoreaction in aqueous system. The additive effect of organic molecules on the yield and diastereoselectivity of the photo-adducts is also discussed.

Cationic Rhodium(I)-Catalyzed Asymmetric Cyclohydroformylation of 1,6-Enynes with Formaldehyde.

We report a rhodium(I)-catalyzed asymmetric cyclohydroformylation reaction of 1,6-enynes with formaldehyde. The reaction of 1,6-enynes with formaldehyde in the presence of a cationic Rh(I) catalyst, such as [Rh(cod)2 ]+ OTf- , and a chiral biaryl diphosphine led to asymmetric cyclohydroformylation to produce aldehydes with higher-order structures highly enantioselectively. This transformation procedure is applicable to a variety of enynes, with wide compatibility in various atoms liking between the alkyne and alkene parts, substituents at the alkyne terminus, and substituents at the alkene part, being converted to newly formed aldehydes in 14% to 90% yields with 50% to 98% ee. The products were further transformed with various nucleophiles to alcohols, an amine, and a diene without loss of chirality at their γ-position.

Rh(I)-catalyzed asymmetric synthesis of 3-substituted isoindolinones through CO gas-free aminocarbonylation.

A highly efficient and accessible synthesis of chiral 3-substituted isoindolinone frameworks is described. The synthesis involved the Rh(I)-catalyzed asymmetric arylation of boronic acids to 2-halobenzaldimines and the subsequent Rh(I)-catalyzed intramolecular aminocarbonylation of the resulting 2-halobenzylamines using an aldehyde as the carbonyl source. The method tolerates a variety of functional groups, yielding isoindolinone derivatives in moderate to high yields with high ee-values. In addition, two Rh(I)-catalyzed transformations could be efficiently accomplished in a one-pot sequence to give chiral isoindolinones by the simple addition of a ligand and an aldehyde after the Rh(I)-catalyzed asymmetric arylation.

To photodeprotect or not: effect of the oxidation state of the sulfur atom of thiochromone derivatives.

Time-resolved spectroscopic experiments, assisted with DFT calculations, were employed to study the photochemical reaction mechanism of (4-oxo-3-phenyl-4H-thiochromen-2-yl) methoxycarbonyl-caged ethanol (TC) and (1,1-dioxido-4-oxo-3-phenyl-4H-thiochromen-2-yl) methoxy carbonyl-caged ethanol (TS-PPG) in different solvents. TC went through an intersystem crossing to form the triplet state with π-π* character in acetonitrile (MeCN) and protic solvents. While the n-π* triplet state was generated for TS-PPG in MeCN, which further underwent Paternò-Büchi reaction to give a biradical intermediate. Then, the C-O bond was cleaved, followed by deprotonation. Besides the similar deprotection route in MeCN, another reaction pathway existed in protic solvents, where the C-O bond heterolysis took place via the singlet excited state. The unambiguous mechanism would not only guide the efficient application of TS-PPG, but also help develop more excellent PPGs based on the thiochromone framework.

Photodissociation of the Product from a Transition-Metal Center Allows the Catalytic Cycle to Proceed: The Rhodium(I)-Catalyzed [2+2+1] Carbonylative Cycloaddition of Diynes.

We describe the effective rhodium(I)-catalyzed [2+2+1] carbonylative cycloaddition of diynes, yielding cyclopentadienes (CPDs), under photoirradiation. The catalysis involves the promotion of the photodissociation of the product CPD, with the simultaneous production of an essential vacant coordination site on the rhodium for an unreacted substrate. The combined use of cationic [Rh(cod)2]BF4 as a catalyst and photoirradiation was also found to give various CPDs in high yields (≤96%).

Sulfonium ion-promoted traceless Schmidt reaction of alkyl azides.

Schmidt reaction by sulfonium ions is described. General primary, secondary, and tertiary alkyl azides were converted to the corresponding carbonyl or imine compounds without any trace of the activators. This bond scission reaction through 1,2-migration of C-H and C-C bonds was accessible to the one-pot substitution reaction.

Sequential Knoevenagel Condensation/Cyclization for the Synthesis of Indene and Benzofulvene Derivatives.

Sequential Knoevenagel condensation/cyclization leading to indene and benzofulvene derivatives has been developed. The reaction of 2-(1-phenylvinyl)benzaldehyde with malonates gave benzylidene malonates, cyclized indenes, and dehydrogenated benzofulvenes. The product selectivity depends on the reaction conditions. The reaction with piperidine, AcOH in benzene at 80 °C for 1.5 h gave a benzylidene malonate in 75% yield as a major product. The reactions with piperidine, AcOH in benzene at 80 °C for 17 h and with TiCl4-pyridine at room temperature gave an indene derivative in 56 and 79% yields, respectively, as a major product. The reaction with TiCl4-Et3N gave a benzofulvene in 40% yield selectively. Indene was transformed to a benzofulvene derivative using the reagents TiCl4-Et3N and 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ). The reaction of variously substituted aryl derivatives with dimethyl malonate gave indene and benzofulvene derivatives. The reactions of 2-(1-phenylvinyl)benzaldehyde with Meldrum's acid or malononitrile also gave cyclized compounds in the suitable sequential or stepwise conditions. Furthermore, the reaction of 2-arylbenzaldehydes has been investigated. The limitation and scope have been described. The reaction mechanism of the cyclization steps has been examined by DFT calculations.