Photoelectrocatalysis for Hydrogen Evolution Ventures into the World of Organic Synthesis.

The use of light as a catalytic prompt for the synthesis of industrial relevant compounds is widely explored in the past years, with a special consideration over the hydrogen evolution reaction (HER). However, semiconductors for heterogeneous photocatalysis suffer from fast charge recombination and, consequently, low solar-to-hydrogen efficiency. These drawbacks can be mitigated by coupling photocatalysts with an external circuit that can physically separate the photogenerated charge carriers (electrons and holes). For this reason, photoelectrochemical (PEC) production of hydrogen is under the spotlight as promising green and sustainable technique and widely investigated in numerous publications. However, considering that a significant fraction of the hydrogen produced is used for reduction processes, the development of PEC devices for direct in situ hydrogenation can address the challenges associated with hydrogen storage and distribution. This Perspective aims at highlighting the fundamental aspects of HER from PEC systems, and how these can be harnessed toward the implementation of suitable settings for the hydrogenation of organic compounds of industrial value.

Organic Upgrading through Photoelectrochemical Reactions: Toward Higher Profits.

Aqueous photoelectrochemical (PEC) cells have long been considered a promising technology to convert solar energy into hydrogen. However, the solar-to-H2 (STH) efficiency and cost-effectiveness of PEC water splitting are significantly limited by sluggish oxygen evolution reaction (OER) kinetics and the low economic value of the produced O2 , hindering the practical commercialization of PEC cells. Recently, organic upgrading PEC reactions, especially for alternative OERs, have received tremendous attention, which improves not only the STH efficiency but also the economic effectiveness of the overall reaction. In this review, PEC reaction fundamentals and reactant-product cost analysis of organic upgrading reactions are briefly reviewed, recent advances made in organic upgrading reactions, which are categorized by their reactant substrates, such as methanol, ethanol, glycol, glycerol, and complex hydrocarbons, are then summarized and discussed. Finally, the current status, further outlooks, and challenges toward industrial applications are discussed.

Organoselenium Compounds: Chemistry and Applications in Organic Synthesis.

Selenium, originally described as a toxin, turns out to be a crucial trace element for life that appears as selenocysteine and its dimer, selenocystine. From the point of view of drug developments, selenium-containing drugs are isosteres of sulfur and oxygen with the advantage that the presence of the selenium atom confers antioxidant properties and high lipophilicity, which would increase cell membrane permeation leading to better oral bioavailability. In this article, we have focused on the relevant features of the selenium atom, above all, the corresponding synthetic approaches to access a variety of organoselenium molecules along with the proposed reaction mechanisms. The preparation and biological properties of selenosugars, including selenoglycosides, selenonucleosides, selenopeptides, and other selenium-containing compounds will be treated. We have attempted to condense the most important aspects and interesting examples of the chemistry of selenium into a single article.

1-[4-(2-Dimethylaminoethoxy)phenylcarbonyl]-3,5-Bis(3,4,5-Trimethoxybenzylidene)- 4-Piperidone Hydrochloride and Related Compounds: Potent Cytotoxins Demonstrate Greater Toxicity to Neoplasms than Non- Malignant Cells.

BACKGROUND: The incidence of cancer has been increasing worldwide. Unfortunately, the drugs used in cancer chemotherapy are toxic to both neoplasms and normal tissues, while many available medications have low potencies. Conjugated α,ß-unsaturated ketones differ structurally from contemporary anticancer medications , some of which have noteworthy antineoplastic properties. OBJECTIVES: This study aimed to design and synthesize highly potent cytotoxins with far greater toxicity to neoplasms than to non-malignant cells. METHODS: A series of N-acyl-3,5-bis(benzylidene)-4-piperidone hydrochlorides 4a-n were prepared and evaluated against Ca9-22, HSC-2, HSC-3, and HSC-4 squamous cell carcinomas as well as against HGF, HPLF, and HPC non-malignant cells. QSAR and western blot analyses were performed. RESULTS: The majority of compounds display submicromolar CC50 values towards the neoplasms; the figures for some of the compounds are below 10-7 M. In general, 4a-n have much lower CC50 values than those of melphalan, 5-fluorouracil, and methotrexate, while some compounds are equitoxic with doxorubicin. The compounds are far less toxic to the non-malignant cells, giving rise to substantial selectivity index (SI) figures. A QSAR study revealed that both potency and the SI data were controlled to a large extent by the electronic properties of the substituents in the arylidene aryl rings. Two representative compounds, 4f and 4g, caused apoptosis in HSC-2 cells. CONCLUSION: The compounds in series 4 are potent cytotoxins displaying tumor-selective toxicity. In particular, 4g with an average CC50 value of 0.04 µM towards four malignant cell lines and a selectivity index of 46.3 is clearly a lead molecule that should be further evaluated.

Take a "Snapshot" of New Syntheses, Reactions, and Characterizations from Unusual Unsaturated Ring Strained Group 4 Metallacycles.

Recently published syntheses, reactions and characterizations of unusual unsaturated ring strained Group 4 metallocene metallacycles like metalla-cyclocumulenes, -cycloallenes and -cycloalkynes with different ring size are updated for the last three years. There exist for some of these metallacycles, depending on the ring size, 7-, 5- and 4-membered compounds. The new results for these metallacycles are summarized here and considered in addition to the former published results. Additionally, several compounds of this type were now characterized by new reactions. For a better understanding of these compounds, some spectroscopical methods as well as theoretical calculations were published. Despite of these all-C-metallacycles, only in some cases the syntheses and reactions for the corresponding hetero-metallacycles were published too. Examples for these metallaheterocyclic compounds will not be considered in this article. All these unusual ring strained compounds have a great potential for a lot of interesting synthetic applications in the future. Additionally, they are very interesting from the theoretical point of view.