Stereospecific alkylation of 3,5,5-trisubstituted-4-hydroxy-1-p-tosyl-2-pyrazolines by trimethylaluminum. An efficient synthesis of 3,3,5,5-tetrasubstituted-1-pyrazolin-4-ones
Stereospecific alkylation of 3,5,5-trisubstituted-4-hydroxy-1-p-tosyl-2-pyrazolines by trimethylaluminum. An efficient synthesis of 3,3,5,5-tetrasubstituted-1-pyrazolin-4-ones
Triethylgallium deprotonated cyclic and acyclicketones at 125-175 degrees C without forming carbonyl addition products, and the resulting gallium enolates underwent facile C-benzoylation and an aldol reaction. Unsymmetrical ketones were preferentially enolized at the methylene moiety, which was under kinetic control. [reaction: see text]
Dialkylaluminium aryloxide in combination with a tertiary amine was found to be a good reagent for regioselective aldol condensation of methyl ketones at the methyl side. Regioselective aldol condensation of 2-octanone was carried out using diisobutylaluminium phenoxide–pyridine. The intramolecular aldol condensation of 2,15-hexadecanedione promoted by the same reagent gave a mixture of dehydromuscones