Systems containing Oxygen

Synthesis.—By Cycloaddition. The Noyori cycloaddition of halogeno-ketones to furans is now sufficiently well established to provide a firm base for the successful synthesis of C-nucleosides. For example, the ketone (109) has been prepared  

The following aspects of [4 + 2] cycloaddition to furans have been studied the use of di-t-butyl acetylenedicarboxylate as a dienophile, thus providing a synthetic equivalent of acetylenedicarboxylic anhydride the use of fumaryl chloride additions to 3,4-dimethoxyfuran and examples of intramolecular addition. 

Fohlisch, W. Gottstein, R. Kaiser, and I. W anner, Tetrahedron Lett., 1980,21, 3005 P. Matzinger and C. H. Eugster, Helv. Chim. Acta, 1979, 62, 2325. 

Synthesis of those insect aggregation pheromones having bridged structures may have important economic consequences. Multistriatin (120) is an aggregation pheromone of a European elm bark beetle. A stereoselective synthesis has been reported from tartaric acid. A delightfully simple synthesis of frontalin (121), a pheromone of the pine beetle, is by photolysis of heptane-2,6-dione in methanol-titanium chloride. We also note further photochemical studies 

Development of synthetic routes to the anthracycline antibiotics is important because of the cytotoxic properties of many of these compounds. A short route to possible intermediates proceeds via double Diels-Alder addition to (16). The problem of the availability of (16) has been overcome by efficient palladium-catalysed carbomethoxylation of the furan-maleic anhydride Diels-Alder adduct to give (122) in 92% yield. Elaboration of Diels-Alder adducts of (16) to anthracyclines requires rupture of the ether bridge. Acid-catalysed ringopening in simple 7-oxabicyclo[2.2.1]heptanes has been studied. 

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It is the purpose of the present article to consider the evidence that the rate parameters offer concerning the nature of the transition states involved in the various radical reactions and how these in turn are affected by the chemical nature of the species involved. Although our principal concern shall be with alkyl radical reactions, we shall also consider some molecular reactions which are closely related and finally the behavior of some systems containing oxygen and halogen atoms as well. 

The disadvantage of this approach is that it refers to a parent system containing oxygen atoms, so that for the linear tetrapyrroles without oxygen, which are those most commonly used, it is necessary to use the prefix 1,19-dideoxy [16]. 

Oxidation of Systems Bearing Lone Pairs of Electrons 7.133.1 Systems containing oxygen... 

Vapor pressure at the flash point and the product of molecular weight and vapor pressure at the flash point were computed for 40 oxygenated solvents. Vapor pressure at the flash point varied between 7 and 58 mm Hg while the product of vapor pressure and molecular weight varied between 800 and 4200. Thus, some of the above methods of predicting flash points of mixed hydrocarbons appear unlikely to be effective for systems containing oxygenated solvents with their attendant non-ideal behavior. 

RING SYSTEMS CONTAINING OXYGEN AND PHOSPHORUS ATOMS... 

Six-Membered Rings Systems containing oxygen or sulphur 345... 

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