Systems containing Nitrogen

In contrast to the saturated azlactones, the Friedel-Crafts reaction of 2-substituted-4-arylidene-5-oxazolones is quite complex and may follow several different courses, often concurrently, depending on both reaction conditions and structural variations in the arylidene ring. This behavior is readily interpreted in terms of the a,)S-unsaturated carbonyl moiety and the cross-conjugated system containing nitrogen, both of which provide potential reaction sites in addition to the lactone carbonyl group. The reaction has been investigated " ... 

Organic chemistry is based on carbon, but nitrogen is fundamental to heterocyclic chemistry. Although there are many important aromatic heterocycles without nitrogen atoms (thiophene, furan, pyrylium salts, etc.), it is clear that the majority of heterocyclic systems contain nitrogen atoms. Thus, NMR spectroscopy ( " N NMR yields the same chemical shifts... 

This review chapter focuses on the syntheses and reactions of these 5-membered heterocyclic ring systems containing nitrogen and sulfur (or selenium) (reported during 2006). The importance of these 71-rich heterocycles in medicinal chemistry and natural products is also covered. 

The intimate relationship between NMR parameters such as chemical shifts and spin-spin coupling constants and molecular geometry is particularly evident for derivatives with rigid frameworks. Therefore, structural and conformational effects are treated first as a separate topic and then in conjunction with specific compounds. As data on hydroxylamines, oximes and hydroxamic acids are not as extensive as those for other types of systems containing nitrogen or oxygen, comparisons with their respective parameters or effects have also been included wherever they are considered relevant. 

Scheme 6 Six-membered monocyclic systems containing nitrogen with oxygen and/or sulfur (the name printed corresponds...

Benzils, like other 1,2-diones, react with 1,2-benzenediamines to form diaza-arenes known as quinoxalines. This kind of reaction is an important general procedure for the synthesis of aromatic ring systems containing nitrogen ... 

The parent saturated three-membered ring systems containing nitrogen, or oxygen, or sulphur as the heteroatom are known as aziridine (1), oxirane (2) and thiirane (3). 

Crystalline dicobalt octacarbonyl or its solutions should be stored in a closed bottle in the cold, preferably under 1 atm. of carbon monoxide because the carbonyl reacts with oxygen. If left in a closed system containing nitrogen, the carbonyl decomposes until a partial pressure of about 0.2 atm, of carbon monoxide has been developed. 

Somait, F.A. and Kidnay, A.J. 1978. "Liquid-Vapor Equilibria at 270.00 K for Systems Containing Nitrogen, Methane, and Carbon Dioxide", /. Chem. Eng. Data, 23 301-305. 

Xu, N., J. Dong, Y. Wang, and J. Shi. 1992. "High Pressure Vapor Liquid Equilibria at 293 K for Systems Containing Nitrogen, Methane and Carbon Dioxide", Fluid Phase Equil., 81 175-186. 

An extensive range of hetero 1-oxabutadiene systems containing nitrogen (Section 4.3.4) and sulfur (Section 4.3.3) have been investigated and found to function as 4ir components of Diels-Alder reactions. In general, the incorporation of an additional heteroatom into the 1-oxabutadiene system increases its electrophilic character and facilitates its 4tt participation in LUMOdiene-controlled Diels-Alder reactions with electron-rich dienophiles. Examples of such systems are presented in Figure 4. ... 

Comparable to the 1-oxabutadienes, the azabutadienes constitute a class of widely investigated heterodienes capable of productive 4tr participation in [4 + 2] cycloaddition reactions. TMs work has been the subject of several comprehensive reviews including recent accounts " that should be consulted for a thorough treatment of the mechanism, scope and applications of the [4 + 2] cycloaddition reactions of azabutadienes. Conjugated systems containing nitrogen characteristically are electron-deficient ir-systems (Table 8) and exhibit an expected diminished Diels-Alder reactivity toward representative electron-deficient dienophiles and a modest Diels-Alder reactivity toward electron-rich dienophiles. 

PART II Systems containing Nitrogen and Sulphur, Selenium, or Tellurium... 

PART I Systems containing Nitrogen by S. D. Carter and G. W. H. Cheeseman... 

Six-Membered Rings Systems containing nitrogen H CgH4N02-o MeOOC COOMe... 

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