Quaternary Azinium Salts

The already high susceptibility of the diazines to nucleophilic addition is greatly increased by quaternisation. Addition of organometallic reagents to A-acyl quaternary salts has been achieved in some cases but is much more restricted than 

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Azines, Quaternary Azinium Salts, and Azine N-Oxides... 

This synthetic strategy also proved to be also suitable for the ring closure to the related [l,3,4]triazolo[2,3-a][l,3,5]tri-azinium salts, as shown in Scheme 33 <1994JHC535, 1995JHC1833> reaction of 169 with l-chloro-l,3-bis(dimethyl-amino)-3-phenyl-2-azaprop-2-enylium perchlorate gave the quaternary salt 170 in 37% yield. 

The general principle that activation of para substitution is greater than of ortho substitution holds true also for an azinium moiety in the one instance studied. Thus, the activation energy for the 4-chloropyridine quaternary salt 280 (Table II, line 9) is 1 kcal lower than that for the 2-isomer (line 5). The rate relation (2- > 4-isomer) is controlled by the entropies of activation in this reaction due to electrostatic attraction in the transition state (281). The reverse rate relation (4- > 2-position) is predicted for aminations of such quaternary compounds due to electrostatic repulsion (282) plus the difference in E. A kinetic study of the 2- and 4-pyridine quaternary salts... 

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