An important first step in making organic reactions more environmentally benign by design requires processes that are, to a first approximation, simple additions with anything else needed only catalytically. Since so few of the existing reactions are additions, synthesis of complex molecules requires the development of new atom-economic methodology. The prospect for such developments is probed in the context of ruthenium-catalyzed reactions. Using mechanistic reasoning, over 20 new processes of varying complexity have been designed and implemented. While some involved oxidation−reduction processes, most involved C−C bond-forming reactions.

On Inventing Reactions for Atom Economy

The [2 + 2] photocycloaddition is undisputedly the most important and most frequently used photochemical reaction. In this review, it is attempted to cover all recent aspects of [2 + 2] photocycloaddition chemistry with an emphasis on synthetically relevant, regio-, and stereoselective reactions. The review aims to comprehensively discuss relevant work, which was done in the field in the last 20 years (i.e., from 1995 to 2015). Organization of the data follows a subdivision according to mechanism and substrate classes. Cu(I) and PET (photoinduced electron transfer) catalysis are treated separately in sections 2 and 4, whereas the vast majority of photocycloaddition reactions which occur by direct excitation or sensitization are divided within section 3 into individual subsections according to the photochemically excited olefin.

http://pubs.acs.org/doi/pdf/10.1021/acs.chemrev.5b00723

Recent Advances in the Synthesis of Cyclobutanes by Olefin [2+2] Photocycloaddition Reactions

http://chemistry-chemists.com/chemister/Warning/Explosives/ExplosiveAbstacts/review-energetic-materials.pdf

A review of energetic materials synthesis

Hydrogen is considered as the fuel for next generation and extensive research is being pursued for search of new techniques for hydrogen production from renewable sources. There is a diverse collection of hydrogen production processes at their different stages of development. This review paper analyzes the industrial and emerging hydrogen production technologies. These processes include steam methane reformation, partial oxidation, autothermal reforming, steam iron, plasma reforming, thermochemical water splitting and biological processes. Till date, steam reformation of methane is the most used industrial technique and its efficiency can go up to 85%. It meets up to 50% of total hydrogen consumption in the world. Continuous research is going on to enhance production yield as well as to improve the process economics. Considerable work is going on about sorption enhanced reforming and membrane reactor for this purpose. Partial oxidation and autothermal reforming processes are the other two processes which are also used for industrial. The most sought process is the thermochemical water splitting using sunlight. Several research institutes are engaged in the development of hydrogen production technologies using renewable sources. Plasma reformation and biological processes are intensively worked out throughout the globe. The present article reviews the recent developments in industrial techniques which will lead to enhancement of hydrogen production. The non-conventional techniques are described in this article as emerging techniques, which are the promising approaches for hydrogen production from biomass, an abundant, clean and renewable source.

A review on development of industrial processes and emerging techniques for production of hydrogen from renewable and sustainable sources

Inspired by the concept of multivalency in living systems, two mechanically interlocked molecules have been conceived that incorporate not once or twice but thrice the features of a pH-switchable [...

Operating Molecular Elevators

[reaction: see text] The template effect exerted by tetrathiafulvalene (TTF) in the ring-closure reaction of the trication 5(3+) yielding cyclobis(paraquat-p-phenylene) has been quantitatively evaluated in acetonitrile at 62 degrees C with UV-vis spectrophotometry. The rate of ring closure of the trication 5(3+) largely increases in the presence of the template (a maximum increase of ca. 80 times at [TTF] approximately 0.14 M). The results are compared with those of other aromatic templates, 2 and 3, that were provided with polyethereal sidearms and indicate that the template ability of tetrathiafulvalene is comparable or better than that of the others.

Template effect of tetrathiafulvalene in the formation of cyclobis(paraquat-p-phenylene).

On the role of electronic and steric factors upon the formation of Meisenheimer-type adducts

The template effects exerted by bis(p-phenylene)[34]crown-10 (3) and by 1,5-dinaphto[38]crown-10 (4) in the ring-closure reaction of the trication 2(3+) to yield the [2]catenanes 7(4+) and 8(4+) have been quantitatively evaluated in acetonitrile at 62 degrees C by UV/visible spectroscopy. The rate of ring closure of the trication 2(3+) dramatically increases in the presence of the templates 3 and 4, up to approximately 230 times at [3] approximately equals 0.1 molL(-1), and up to approximately 1,900 times at [4] approximately equals 0.01 molL(-1). The outcome of kinetic selection experiments, in which the two crown ethers compete for the incorporation into the catenane structure, has been discussed in the light of the obtained results. It has been shown that the product ratio of catenanes obeys the Curtin-Hammett principle only if the concentrations of the templates are equal and much greater than that of the substrate. Analysis of the rate profiles has shown that the 1,5-dioxynaphthalene unit, present in the template 4, has a greater affinity than the 1,4-dioxybenzene unit, present in the template 3, for the electron-deficient pyridinium rings present in both the transition-state and substrate structures. Ab initio calculations at the 3-21G and 6-31G(d) levels of theory indicate that the greater affinity of the 1,5-dioxynaphthalene unit cannot be explained on the basis of greater pi-pi stacking and [C-H...pi] interactions, but rather on the basis of the model of apolar complexation in which the solvent plays a major role.

Template Effects and Kinetic Selection in the Self-Assembly of Crown Ether Cyclobis(paraquat-p-phenylene) [2]Catenanes—Effect of the 1,4-Dioxybenzene and 1,5-Dioxynaphthalene Units

Nucleophilic substitution at the pyrrole ring. Comparison with furan, thiophene, and benzene rings in piperidinodenitration

Publisher Summary This chapter deals with thiopyrylium, selenopyrylium, and telluropyrylium salts. These compounds are considered the parent structures of an important class of six-membered heteroaromatic cations. It is observed that the reactivity of thiopyrylium salts resembles that of pyrylium salts with two notable differences— namely, the lesser tendency of 2 H adducts formed on nucleophilic attack to undergo ring opening and the ability of sulfur to accommodate more than eight electrons in its valence shell, leading, in some cases, to the formation of thiabenzene derivatives. The chapter also describes the structural and physical properties, the methods of synthesis, the reactions, and the practical uses of these pyrylium salts. There are large number of patents and applicative studies making use of a chalcogenopyrylium salt. Most applications of chalcogenopyrylium salts exploit their photophysical and photochemical properties, and principally regard photographic and reprographic technologies. Another important application of chalcogenopyrylium salts is as polymerization and crosslinking photoinitiators, especially in the preparation of photoresists, printing plates, and photosensitive compositions for laser imaging.

Giancarlo Doddi

Papers

Template effect of tetrathiafulvalene in the formation of cyclobis(paraquat-p-phenylene).

On the role of electronic and steric factors upon the formation of Meisenheimer-type adducts

Template Effects and Kinetic Selection in the Self-Assembly of Crown Ether Cyclobis(paraquat-p-phenylene) [2]Catenanes—Effect of the 1,4-Dioxybenzene and 1,5-Dioxynaphthalene Units

Nucleophilic substitution at the pyrrole ring. Comparison with furan, thiophene, and benzene rings in piperidinodenitration

Thiopyrylium, Selenopyrylium, and Telluropyrylium Salts