Nitrogen and Sulfur Heterocycles

Condensa.tlon, This term covers all processes, not previously iacluded ia other process definitions, where water or hydrogen chloride is eliminated ia a reaction involving the combination of two or more molecules. The important condensation reactions are nitrogen and sulfur heterocycle formation, amide formation from acid chlorides, formation of substituted diphenyl amines, and misceUaneous cyclizations. 

Some nitrogen and sulfur heterocyclic systems produced in roasted coffee. 

Organic chemicals that are susceptible to oxidation and are of concern from the perspective of contamination and environmental degradation include aliphatic and aromatic hydrocarbons, alcohols, aldehydes, and ketones phenols, polyphenols, and hydroquinones sulfides (thiols) and sulfoxides nitriles, amines, and diamines nitrogen and sulfur heterocyclic compounds mono- and di-halogenated aliphatics linear alkybenzene-sulfonate and nonylphenol polyethoxylate surfactants and thiophosphate esters. Table... 

Oleg Rakitin was born in Moscow in 1952, studied at M. V. Lomonosov Moscow State University, and graduated in 1974. He has worked as a junior researcher (1974-82), senior researcher (1982— 94), principal researcher (1994-95), and since 1995 as head of the laboratory at N. D. Zelinsky Institute of Organic Chemistry. He received his Ph.D. in 1980 and his Doctor of Science in 1992. He has spent several months in the laboratory of Professor C. W. Rees at Imperial College (London, UK) being awarded a Royal Society Kapitza Fellowship (1992), a Royal Society of Chemistry Journals Grant for International Authors (1997, 2000, 2004), and Royal Society Joint Projects (1993, 1999, 2002, 2004). He has been a Fellow of the Royal Society of Chemistry since 1999. His scientific interests include the synthesis and chemistry of nitrogen and sulfur heterocyclic compounds, particularly polysulfur heterocycles. 

In a study of synthetic routes to the phorbol class of compounds, Lautens cyclised the stannane 307 (with 5 equiv MeLi, to avoid stannane reincorporation) to the 7,5-fused ring system 3 0 8.138 This reaction also works in the synthesis of analogous saturated five-membered nitrogen and sulfur heterocycles (see below). 

Professor Yates made important contributions to organic photochemistry, mechanistic organic chemistry, synthetic methods, and spectroscopy of organic compounds. His most important work in photochemistry was discovery of the photorearrangement of cyclic ketones to oxacarbenes. His studies of alpha-diazoketones led to syntheses of novel nitrogen and sulfur heterocycles. Among his many contributions to synthetic methodology was his discovery that some Oiels-Ajper reactions can be accelerated by Lewis acids. 

Disturbance of the natural surface microlayer by chronic or adventitious spills of petroleum has become an unfortunately common occurrence in the last 30 years. In areas with heavy ship traffic, as much as 85% of the surface organic matter may be petroleum hydrocarbons (Morris, 1974). Both crude and refined oils have been repeatedly spilled in large accidents. Crude petroleum is a bewilderingly complex mixture of hydrocarbons, phenols, carboxylic acids, nitrogen and sulfur heterocycles, and other constituents. During the refining process, some classes of compounds may be almost entirely removed, but others may be produced in addition, additives such as antioxidants may be introduced. 

A low concentration of nitrogen and sulfur heterocycles also can be found in various petroleums. Coal was for years the major source of pyridine-based heterocycles, obtained by pyrolysis in the absence of oxygen (destmctive distillation). An intriguing new detection of heterocycles in nature has occurred in the field of chemistry of the solar system. Pyridine carboxylic acids have been detected in a meteorite that landed in Canada (near Tagish Lake)." Nicotinic acid and its two isomers were isolated along with 12 methylated and other derivatives. 

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