Synthesis of value-added N-containing aromatic products from lignins: a review.

Abstract

The simultaneous degradation and valorization of the most abundant renewable aromatic lignin provide significant benefits for synthesizing complex N-containing aromatic products, which are used in various applications ranging from pharmaceuticals to materials. Therefore, broadening the range of N-containing aromatic products derived from lignin is one of the key objectives in fulfilling future biorefinery and green chemistry needs. Enormous research efforts have been directed toward lignin depolymerization since the structural analysis of lignin has become increasingly understood. Over the past decade, significant progress has been made in N-participated degradation strategies utilizing lignin models and extracts as raw materials. This review focuses on various activation strategies for cleaving the lignin C-C/C-O bonds while forming new C-C/C-N bonds in the presence of transition-metal and metal-free catalysts. Additionally, insights into the fundamentals of reaction control, understanding reaction pathways, and their applications in the synthesis of active pharmaceutical ingredients and functionalized materials are discussed.