Cinnolinones preparation

Ethyl-1 -methoxycarbonylmethyl-2-(o-propylphenylhydrazono)cyclohexane (23) (prepared in situ) gave 4a-ethyl-2-(o-propylphenylhydrazono)-4,4a,5, 6,7,8-hexahydro-3(2f/)-cinnolinone (24) (20% H2SO4, reflux, 30 min 26% after separation from another product) analogs likewise. ... 

Most such cinnolinones have been made by primary synthesis (see Chapter 1), a few by hydrolysis of halogenocinnolines (see Section 3.2), and others using procedures illustrated in the examples below it is noteworthy that several useful preparative routes, such as hydrolysis of alkylthiocinnolines or other types of thiocinnoline, appear to be unrepresented in the 1972-2004 literature. 

The Yang group synthesized indeno[l,2-c]cinnolinone (15) in 93% yield by treating indenone 16, previously prepared from 2-(2-arylethynylphenyl) acetonitrile 17 via a palladium(II)-catalyzed oxidation/condensation... 

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