Polynitrogen heterocycles are readily available and have recently arisen as versatile synthons for the formation of various C–C and C–X bonds, and medicinally active nitrogen-containing heterocycles. Several cascade reactions, including annulation, radical cascade, and borylation reactions, have been reported in which polynitrogen heterocycles are applied as arylation reagents. The success of these exceptional reactions illustrates the great synthetic potential of polynitrogen heterocycles, which provides a direct and useful approach to arylation reactions and the synthesis of nitrogen-containing heterocycles. The use of photocatalysts to effectively transfer energy from visible light to non-absorbing compounds has gained increasing attention as this method allows for the mild and efficient generation of radicals in a controlled manner. This approach has thus led to new methods that involve unique bond formation reactions. In addition, the use of free radical intermediates stabilized by transition metal catalysts is a powerful way to construct new chemical bonds. The aim of this review is to highlight the rapidly expanding area of radical-initiated denitrogenative cascade reactions of polynitrogen heterocycles and elaborate on their mechanisms from a new perspective by using photocatalysis and metal-based catalysis.

多氮杂环很容易获得，并且最近作为多功能合成子出现，用于形成各种 C-C 和 C-X 键，以及具有药用活性的含氮杂环。已经报道了几种级联反应，包括环化、自由基级联和硼化反应，其中多氮杂环用作芳基化试剂。这些特殊反应的成功说明了多氮杂环的巨大合成潜力，它为芳基化反应和含氮杂环的合成提供了一种直接且有用的方法。使用光催化剂将能量从可见光有效转移到非吸收性化合物越来越受到关注，因为这种方法允许以受控方式温和有效地产生自由基。因此，这种方法导致了涉及独特的键形成反应的新方法。此外，使用由过渡金属催化剂稳定的自由基中间体是构建新化学键的有力方法。本综述的目的是突出自由基引发的多氮杂环脱氮级联反应的快速扩展领域，并通过使用光催化和金属基催化从新的角度阐述其机制。