Carboxylation of Active Methylene Compounds Using 1, 3-Diphenylurea, Potassium Carbonate and Carbon Dioxide

Abstract

The effects of various urea derivatives on the carboxylation of fluorene with carbon dioxide were examined in the presence of potassium carbonate at room temperature under atmospheric pressure. As shown in Table 2, the carboxylation of fluorene was remakably promoted by the addition of 1, 3-diphenylurea (DPU).
Acetophenone, 1-indanone, indene, phenylacetonitrile, and 1-tetralone were effetively carboxylated by employing the similar reagent system, 1, 3-diphenylurea, potassium carbonate and carbon dioxide to produce benzoylacetic acid, 1-oxoindan-2-carboxylic acid, 1 H-indene3-carboxylic acid, a-cyanophenylacetic acid, and 1-oxo-1, 2, 3, 4-tetrahydro-2-naphthoic acid, respectively (Table 4). NMR and other investigations carried out in the carboxylation of fluorene led us to suggest that the carboxylation is initiated by the formation of a complex among 1, 3-diphenylurea, potassium carbonate and carbon dioxide (2: 1: 2), and the reaction of the complex with fluorene to form 9-fluorene carboxylate is the fast step. Rubidium carbonate and cesium carbonate proved to be better base than potassium carbonate, but l ithium carbonate and sodium carbonate were not effective (Table 3).