Synthesis of some heteroarylated dioxopiperazines

Abstract

Section 1 (Introduction) provides a short history of pigment development through selected examples. It also details some of the requirements which have to be considered during the formulation of new coloured materials. A brief outline of some synthetic routes towards arylated amino acids and substituted 2,5-dioxopiperazines is also described with the aim of including some of these ideas into the project. Section 2 (Results and Discussion) develops some of the ideas outlined in Section 1. This Section is split into two parts, namely synthetic approaches to some arylated amino acids and some 3,6-disubstituted-2,5-dioxopiperazines. The former part covers the possible routes towards the desired amino acids and deals with the search for a suitable N-protecting group for glycine ethyl ester. It was shown that the propensity for the arylated amino acids either to polymerise or decarboxylate greatly hindered the removal of the various protecting groups examined. The second part covers the search for a suitable N-acyl protecting group to allow the coupling of the 1,4-diprotected-2,5-dioxopiperazine with an aromatic heterocycle. Synthesis of 3,6-bis(benzoxazol-2-yl)-1,4-dibenzyl-2,5-dioxopiperazine was successful; however all attempts at debenzylation failed. The synthesis of 3-(1-t-butoxycarbonyl- benzimidazol-2-yl)-2,5-dioxopiperazine gave rise to some very interesting spectroscopic data which are discussed in this Section. Section 3 (Experimental) details the synthetic procedures used and this is then followed by the Bibliography.