PRIMARY SYNTHESES FROM OTHER HETEROCYCLIC SYSTEMS

Primary Syntheses from Other Heterocyclic Systems 

The primary synthesis of pyrazines from other heterocyclic systems has a body of literature that is quite modest by comparison with those for pyridazines1687 and pyrimidines.1688 Earlier information on such syntheses has been summarized in Barlin s original book1686 and some more recent data have been reviewed thoughtfully from time to time.1677,1689 

The present treatment of post-1978 literature is divided according to the nature of the heterocyclic substrate (monocyclic, bicyclic, tricyclic, or spiro) each of these broad categories is then subdivided alphabetically, with reduced substrates included with their aromatic counterparts. Cyclic anhydrides, cyclic imides, lactones, and the like are classified as the appropriate heterocyclic derivatives. A glance index to the main product types is appended as Section 2.5. 

Such syntheses can occur by ring expansion, ring contraction, rearrangement, ring fission (with or without subsequent elaboration), fragmentation with subsequent elaboration, or combination with a second synthon followed by other reactions. 

---

Primary Syntheses from Other Heterocyclic Systems... 

---