Saturated heterocycles and stereoelectronics

It may seem strange that heterocycles—rings containing not just carbon atoms, but oxygen, nitrogen, or sulfur as well—deserve three whole chapters, but you will soon see that this is justified both by the sheer number and variety of heterocycles that exist and by their special chemical features. We dealt with the special stereochemical features of aromatic heterocycles 

The saturated heterocyclic rings are shown in black, and names for the most important ring types are given some (like piperidine, morphoiine) you wiil need to remember others (tetrahydrofuran, pyrrolidine) are more obviously derived from the names for aromatic heterocycies you met in the last chapter. Some of these compounds (nicotine, coniine, cocaine) are plant products falling into the class called alkaloids which are discussed in Chapter 42. Another important class of saturated heterocycies, sugars, will also appear in Chapter 42. 

But what are the special chemical features of saturated heterocycies Putting a heteroatom into a ring does two important things, and these lead to the most important new topics in this chapter. 

Saturated nitrogen heterocycies amines, but more nucleophilic 

In many reactions the simple saturated nitrogen heterocycies—piperidine, pyrrolidine, piperazine, and morpholine—behave simply as secondary amines that happen to be cyclic. 

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Background Needed for this Chapter Reference to Clayden, Organic Chemistry Chapter 42 Saturated Heterocycles and Stereoelectronics. 

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