Photocatalysis as a green alternative toolkit for the construction of nitrogen-enriched heterocycles via the direct and indirect activation of alkynes/alkenes

Abstract

Alkenes and alkynes are among the most fundamental and valuable synthons utilized to create atom- and step-efficient heterocyclic compounds, which are crucial components of many drugs, natural products, and essential intermediates in contemporary synthetic organic chemistry. Furthermore, because of their many physical, chemical, and biological properties, nitrogen-based motifs have become crucial building blocks in materials and pharmaceutical chemistry. Consequently, nitrogen heterocycles have been decorated with numerous chromophores and fine chemicals via novel synthetic techniques and procedures to enhance their functional properties. Traditional reactions require predetermined reagents and appropriate interacting catalysts. Alternatively, photoinduced techniques do not require these conditions as light may directly interact with molecules and increase their reactivity. Since nitrogen scaffolds are present in >50% of all medicinal and functional materials, creating an effective synthetic process employing a photo-induced approach has become a valuable tool in recent years. This study summarizes and presents photocatalytic processes for the synthesis of nitrogen-enriched heterocycles from saturated and unsaturated alkynes and alkenes. Alternative methods involving the activation of nitrogen precursors are also discussed and compared.