Fused Five-Membered Heterocycles

Due to the migration of C=C bond, the conjugated esters formed can accept the attack of a second nucleophile. Thus, by applying different difunctionalized benzenes, benzo-fused five-membered heterocyclic compounds 526 can be prepared... 

Chimichi et al. have reported the synthesis and spectroscopic data for all four thiazolopyridine isomers in order to examine how the differently substituted fused five-membered heterocycle influences the chemical and spectroscopic properties <1997MRG601>. The unambiguous assignment of the chemical shifts of these systems was reported and coupling constants showed that azole ring fusion on the pyridine system is responsible for a significant... 

This chapter reviews the systems where account is taken of the size of the central carbocyclic ring, the relative orientation of the fused five-membered heterocyclic rings, the types of heteroatoms, their number, and, in rings with more than one heteroatom, their relative situations. 

Two Fused Five-membered Heterocyclic Rings (i) Classical Systems... 

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