Synthesis of Monocyclic Rings with Two or More Heteroatoms

Synthesis of Monocyclic Rings with Two or More Heteroatoms 

In this chapter, synthetic methods are classified by the ring that is being formed. We deal successively with rings containing two, three and four or more heteroatoms. Within each category, classification is first by the relative orientation of the heteroatoms, and then by the ring size. 

However, we commence with two brief sections dealing with preparative methods involving substituent introduction and modification for the two large and important classes of monocyclic compounds those with five and six members and with various heteroatoms. 

As explained in Chapter 3.2, the reactivity of six-membered rings containing two heteroatoms bears the same relationship to six-membered rings containing one heteroatom as do the latter to benzene. Hence many of the methods listed for the preparation of pyridines by substituent introduction and modification in Table 1 of Section 4.2.4.1 are also applicable to the preparation of analogous azines. 

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