Catalytic Effect of Tertiary Amines on N, N-Dibenzoylation of Aniline

Abstract

In the presence of both pyridine and triethylamine, aniline reacted with an excess of benzoyl chloride in chloroform at its refluxing temperature to give N-phenyldibenzamide in almost 90% yield. In the absence of either pyridine or triethylamine, however, no dibenzoylation occurred and only benzanilide was produced, indicating that both pyridine and triethylamine are required to promote the facile dibenzoylation.
To investigate the role of pyridine and triethylamine on the dibenzoylation, the conversion rates of the dibenzoylation of aniline with various molar ratios of pyridine and triethylamine have been studied by high pressure liquid chromatography (HLC) (Fig.1). The optimum molar ratio of pyridine and triethylamine on the dibenzoylation was found in the range of 1: 3-1: 4 (Fig.2). From the study on the conversion rate in the benzoylation of benzanilide by HLC (Fig.3), the dibenzoylation of aniline was found to proceed via benzanilide as an intermediate. Accordingly, the dibenzoylation mechanism has been proposed as shown in Fig.5.