Hydrogen exchange at ring carbon in neutral azoles

2 Hydrogen exchange at ring carbon in neutral azoles 

Reactivity of Five-membered Rings with Two or More Heteroatoms 

1-Substituted tetrazoles readily exchange the 5-hydrogen for deuterium in aqueous solution. A major rate-enhancing effect is observed with copper(II) or zinc ions due to a-complexation with the heterocycle. The rate of base-induced proton-deuterium exchange of 1-methyltetrazole is 105 times faster than 2-methyltetrazole (77AHC(2l)323). 

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