Bicyclic 5-6 Systems: Three Heteroatoms 1:2

Abstract

The literature of 5/6 fused ring systems with one heteroatom in the five-membered ring and two heteroatoms in the six-membered ring is reviewed. The period covered is from the beginning of 1994 through the end of 2005. During this span of years, the number of citations has more than doubled since the appearance of the review found in CHEC-II(1996) dealing with these same ring systems. Because of this expansion and the necessity of controlling the number of pages devoted to this topic in this edition, certain limitations have been imposed on the extent of coverage. These limitations have resulted in coverage of only the journal literature, excluding nearly all of the patent literature, and those ring systems that bear two nitrogen atoms in the six-membered ring. The vast majority of these ring systems are aromatic in nature. The formerly known miscellaneous ring systems (CHEC-II(1996)) that possess combinations of nitrogen, oxygen, and sulfur atoms in the six-membered ring have, regrettably, been excluded. The literature covered in this chapter is focused mainly on syntheses of specific compounds. Consequently, this occupies the large majority of the pages devoted to this chemistry. Reactions of the rings and their substituents are covered where the chemistry is determined to be either unique or beyond ‘standard reactions’ found in most textbooks or other similar treatises. Finally, very little has been explored outside of synthesis and reactions and so this is reflected in the paucity of coverage in the remaining sections.