SYNTHETIC APPROACHES AND N-FUNCTIONALIZATION OF 1,4,7-TRIAZACYCLONONANES: A REVIEW

Abstract

Several synthetic approaches have been developed by researchers toward the synthesis and functionalization of 1,4,7-Triazacyclononanes (TACN) in the last decade. Results obtained in this qualitative study have shown that different approaches described in the literature used often protective groups that make it possible to vary the nature of the functions grafted onto the macrocycle according to the intended application. However, the existing methods require harsh reaction conditions (acid treatment) at the final step for the deprotection step. Unfortunately, results compiled in this review paper have shown that despite the increased interest in TACN and its derivatives in the last decade, only a few synthetic methodologies have been reported in the literature, of which some have been reviewed in this current work, with a special emphasis on their advantages and disadvantages as well as the N-functionalization of TACN and its derivatives therefore. Research Methods: In this bibliographic survey, our approach focused on the literature on synthetic approaches and n-functionalization of 1,4,7-triazacyclononanes. Several results were retrieved from articles, dissertations, and theses addressing this study. These results were retrieved using Google, which was considered our search engine. In short, it was the documentary technique that was used. We have covered almost all reports in this review with a detail of synthetic Figures and respective pathways with different reagents and conditions. Regarding the results, Results obtained in this qualitative study have shown that different approaches described in the literature used often protective groups that make it possible to vary the nature of the functions grafted onto the macrocycle according to the intended application. However, the existing methods require harsh reaction conditions (acid treatment) at the final step for the deprotection step. In general, these approaches were mostly multi-steps and resulting in poor yields. Apart from a direct commercial and economic impact, the adoption of green chemistry principles would have many benefits, including minimization of waste, reduction in eco-pollution, and the potential for higher yields through the use of fewer synthetic steps. Unfortunately, results compiled in this review paper have shown that despite the increased interest in TACN and its derivatives in the last decade, only a few synthetic methodologies have been reported in the literature, of which some have been reviewed in this current work, with a special emphasis on their advantages and disadvantages as well as the N-functionalization of TACN and its derivatives therefore.