The model compounds related to the fundamental coal structure are introduced and their chemical behavior under coal liquefaction condition is described. The selected structures are aryl ethers, aryl alkyl hydrocarbons, ketones, heterocycles, and tricyclic hydrocarbons. Effects of coal minerals on the reaction course and the role of tetralin are also briefly reviewed.
Recent progress in regioselective carbon-carbon bond forming reactions involving “ambident substrates” has been reviewed with 308 selected references. This article is divided into two parts, Part 1 concerns the reactions of ambident nucleophiles which mainly include the di-anions of enolates and the asymmetric allylic carbanions. Part 2 involves the reactions of ambident electrophiles which are represented by α, β-unsaturated carbonyl systems, the SN2'reactions of allylic alcohol derivatives and the epoxy compounds containing a nucleophile in the same molecule. Some plausible explanations and controlling factors of these regioselectivities are summarized.
Recent progress in developing new methods for the epoxidation of unsaturated compounds has been reviewed. Newly developed epoxidizing reagents as well as modified methods utilizing conventional epoxidizing reagents are described. These include epoxidations with (1) peracids, (2) activated hydrogen peroxide, (3) molecular oxygen, and (4) miscellaneous reagents. Particularly, stereocon-trolled epoxidations and asymmetric synthesis of epoxides are emphasized.
Synthesis of C-nucleosides starting with non-carbohydrate precursors is reviewed. Most entries described herein utilize 2+4- or 3+4-type cycloaddition reaction in the key step, which allows strict stereochemical control of the four chiral centers.
The majority of animals and plants are marine. The intensity of natural products research that has been spent on land forms is now extended significantly to the marine forms. Among the most active areas has been reseach on substances that are toxic to man or other land forms. Tetrodotoxin, saxitoxin, kainic acid and holotoxins are substances whose activity is elicited by the transfer from the sea to the land. Hormones such as 1-methyladenine in the starfish gonad and pheromones such as bonellin are substances that are biologically active in the marine environment. By using marine eggs as test materials, aphidicolin produced by a fungus was shown to be a direct and selective inhibitor of cellular DNA replication. Thus, aphidicolin was transferred from the land to the sea. In due course, the anti-cancer effect of aphidicolin has been shown. We should strive to detect the highest possible range of activity in all natural products...... including the activity toward a suitable marine organism.
Utility of metallacycles for organic synthesis is briefly reviewed. The syntheses and applications of 3, 4 and 5-membered ring metallacycles of transition metals and main group metals together with some of the large membered ring metallacycles are illustrated.
The mesomorphic states such as liquid crystalline, discotic or carbonaceous, plastic, paracrystalline and viscous crystalline mesophases were classified and discussed on the light of the characteristics of the states. Historical developments of liquid crystals were reviewed briefly from their discovery to technical applications like a display technology, covering scientific, medical and technological researches and applications : Mesogenic compounds were used as solvents for NMR, ESR and optical spectroscopies such as IR and UV, and chemical reactions such as degradation, Claisen rearrangement, photoreaction, polymerization, hydrolysis, oxidation or reduction, carbonization and photoelectrochemical reaction, and also in gas-liquid chromatography. Technical application included many types of displays such as digital, signal, advertising, analog, color displays, image converter and large-area screens. Liquid crystals were used in coherence optics and for medical applications such as diagnoses of vascular diseases and cancer, localizing the placenta, pharmacological tests and skin grafting. The first period from the middle of the 19th century until 1922 comprised the discovery of liquid crystals and work of predominantly descriptive character, followed with the first theoretical work and the foundation of systematology of the phase. The second was known with the development of quantitative theory and the investigation of the effects of outer forces and fields on liquid crystals, beginning from 1922 to 1945. Severe interruption and even complete collapse of international communication continued until the end of the war. During the last period from 1945 technical application and scientific research made a strong revival which lasts until today, achieved successfully the combination of material (liquid crystals), energy and systems (electronics).
Nine 3-cinnamoyltropolones 1 a-i were oxidized with hydrogen peroxide in the presence of alkali to afford 2-benzylidene-3, 8-dihydro-2H-cyclohepta [b] furan- 3, 8 -diones 4 a-i, which have an aurone-like structure. In some cases, methoxy-substituted benzaldehydes and/or phenols were isolated, besides 4.