The reaction of 2-(tetrazol-5-yl)alkyl ketones and of 2-(tetrazol-5-yl)alkanoic acid derivatives with lead tetraacetate. A novel method of preparation of alk-2-ynyl ketones and alk-2-ynoic acid derivatives

The majority of tetrazolylacetyl derivatives 2 and 7, when treated with lea d tetraacetate in dry 1,4-dioxane at room or lower temperature, are oxidize d with elimination of molecular nitrogen mainly to the corresponding alkyno yl derivatives 4 and 8, respectively. Vinylidenes (25) have been shown to b e the intermediates of the reaction. The reaction does not take place when either the tetrazolyl group is N-substituted or the carbon atom separating the tetrazolyl and the carbonyl groups is disubstituted or these two groups are separated by two carbon atoms as in compound 17. The reaction offers a convenient method for the conversion of 2-cyanoacetyl derivatives into alk -2-ynoyl derivatives via intermediate tetrazolylacetyl derivatives. The 4-m ethoxyanilide 7o reacts differently, affording the fused heterocyclic compo unds 19o and 20o.