The reaction of piperazine-2,5-dione with 2-formylbenzoic acid.

Abstract

Reaction of piperazine-2,5-dione with 2-formylbenzoic acid in the presence of triethylamine gives three products: 1-(3'-oxo-1',3'-dihydroisobenzofuran-1'-yl)piperazine-2,5-dione, its 1,4-bis analogue which had previously been identified as the 3,6-compound, and 2,2'-[3,6-dioxopiperazine-2,5-diylidenebis(methylidyne)]bis(benzoic acid). The latter compound is shown by ¹H and ¹³C n.m.r, spectroscopy to be the Z,Z isomer.