By Formation of the Cl-C8a Bond

This bond formation has been achieved, for example, by simple isomerization of the substrates, by dehydrogenation of substrates bearing an co-aryl groups, or by dehydration of substrates bearing conventional leaving groups. Examples in each category follow. 

Cinnolines and Phthalazines Supplement II, The Chemistry of Heterocyclic Compounds, Volume 64, by D.J. Brown Copyright 2005 John Wiley Sons, Inc. 

Note This can occur either by aerial ( ) oxidation with retention of the aryl group or by oxidative loss of arene. 

By Cyclization of Substrates Bearing Conventional Leaving Groups 

Note In these examples, the substrate undergoes cyclization by loss of water, an alcohol, ammonia, acetic acid, or the like. 

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