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.

Quantitative Photodeprotection Assessment of Caged Resveratrol by Fluorescence Measurement

For monitoring the regenerated bioactivity of a masked bioactive compound, resveratrol (a luciferase inhibitor) was selected to target such a compound. Caged resveratrol, masked by thiochromone-type photolabile-protecting groups was synthesized in the study. Each caged resveratrol showed lower bioactivity when compared to that shown by the original molecule. After photoirradiation, the original bioactivity was found to be regenerated. Furthermore, the fluorescent compound derived from the thiochromone-type photolabile-protecting groups was generated simultaneously. A linear correlation was observed between the regenerated bioactivity and generated fluorescence intensity. Thus, we quantitatively monitored the recovered bioactivity successfully by measuring the fluorescence.

Convenient Phenacene Synthesis by Sequentially Performed Wittig­ Reaction and Mallory Photocyclization Using Continuous-Flow Techniques

Various phenacenes possessing chrysene, picene, and fulminene frameworks were prepared by using a continuous-flow synthetic protocol in which Wittig reaction affording diarylethenes and their Mallory­ photocyclization producing phenacene skeletons were sequentially performed. The Wittig reaction solution, containing the diaryl­ethene obtained from an arylaldehyde and an arylmethyltriphenylphosphonium salt, was mixed with an iodine solution in the flow system and, subsequently, the solution was subjected to the photoreaction. Desired phenacenes were obtained with high to moderate chemical yield. For the present protocol, isolation of the intermediary diarylethene, which is the key precursor of the phenacene, is unnecessary. The approach provides a convenient method to supply a variety of phenacene samples, which are needed for initial systematic surveys in material science.

Extended germa[N]pericyclynes: synthesis and characterization

We herein describe the syntheses and characterization of extended germa[N]pericyclynes, which are macrocycles composed of germanium-butadiyne units. The obtained novel extended germa[4]-[8]pericyclynes were characterized by X-ray crystallography, UV-Vis spectroscopy, fluorescence and phosphorescence emission spectroscopy, and cyclic voltammetry, and exhibited characteristic absorptions and emissions. Density functional theory (DFT) calculations suggested smaller HOMO-LUMO gap energy compared to that of general germapericyclynes.

Rh(I) -Catalyzed Intramolecular Carbonylative C-H/C-I Coupling of 2-Iodobiphenyls Using Furfural as a Carbonyl Source

Synthesis of fluoren-9-ones by a Rh-catalyzed intramolecular C-H/C-I carbonylative coupling of 2-iodobiphenyls using furfural as a carbonyl source is presented. The findings indicate that the rate-determining step is not a C-H bond cleavage but, rather, the oxidative addition of the C-I bond to a Rh(I) center.

Stereospecific cyclization reaction of alkenyl esters and amides of ethenetricarboxylate

The stereospecificity of the cyclization reaction of (E)- and (Z)-2-alkenyl esters and amides of ethenetricarboxylate has been examined. The reaction of (E)/(Z)-2-butenyl esters with AlCl3 or FeCl3 gave trans-substituted chlorinated γ-lactone diastereomers stereospecifically. (E)/(Z)-2-butenyl and pentenyl amides undergo an intramolecular ene reaction at room temperature gradually. At 80 °C, the (Z)-alkenyl amides were transformed to cis-substituted ene adducts and the (E)-amides were transformed to cis- and trans-substituted ene adduct mixtures. The reaction of (E)/(Z)-2-alkenyl amides with ZnI2 gave trans-substituted γ-lactam diastereomers stereospecifically along with the ene adducts.

Stepwise synthesis and characterization of germa[4], [5], [8], and [10]pericyclynes

The stepwise syntheses of germa[N]pericyclynes, including [5]pericyclynes, and their characterization are described. The yields of germa[4] and [8]pericyclynes were improved significantly compared to those obtained in previous studies. The routes reported herein afforded the novel germa[5] and [10]pericyclynes, which were characterized by X-ray crystallography, UV-Vis spectroscopy, and fluorescence emission spectroscopy. A unique fluorescence emission was observed for the large germa[10]pericyclyne ring.