C(α),O‐Dilithiooximes, C(α), N‐dilithiophenylhydrazones, or C(α), N‐dilithioacylhydrazones were prepared in an excess of lithium diisopropylamide (LDA) and condensed with a variety of esters followed by acid‐cyclization to give substituted isoxazoles and pyrazoles.
The 1,4‐dianions of C(α),N‐carboalkoxyhydrazones and C(α),N‐phenylhydrazones were prepared in an excess of lithium diisopropylamide (LDA). These dilithiated intermediates resulted from metalation of substituted hydrazones of several all‐aliphatic cyclic ketones, aliphatic‐aromatic cyclic ketones phenylacetaldehyde, and several substituted propiophenones or acetophenones. The esters utilized for Claisen‐type condensations of these dianion intermediates included methyl salicylate, methyl p‐hydroxybenzoate, methyl nicotinate and related materials. The condensations were followed by acid‐cyclizations to give a variety of N‐phenylpyrazoles and N‐carboalkoxypyrazoles, most of which are new.
Certain hydrazones having an a-hydrogen atom were treated with 3 rnol. equiv. of n-butyl-lithium to give (presumably) the C(a)NN-trianions. These trianions were aroylated with esters a t the a-carbanionic centre and cyclized with acid to give pyrazoles.
C(α),O‐Dilithiooximes and C(α),N‐dilithiophenylhydrazones were prepared using an excess of lithium diisopropylamide (1:3). Condensation with esters followed by acid cyclization gave isoxazoles and pyrazoles.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.