Dihydroquinolin-2(1H)-ones (DHQOs) represent a class of valuable bioactive compounds with six-membered nitrogen-containing heterocyclic structures. The development of simple, mild, and efficient synthetic methods has been widely considered by synthetic chemists. In this review, we have summarized a series of different synthetic strategies for the synthesis of DHQOs via the catalytic annulation of α,β-unsaturated N-arylamides in the past decade, including covering electrophilic cyclization, radical initiated cyclization, and photochemical cyclization reactions. Additionally, the substrate scope and mechanistic details are also discussed. This paper provides a useful reference for the development of diverse synthesis methodologies of DHQO.

Quinoline, a heterocyclic scaffold of paramount importance in medicinal and industrial chemistry, has garnered significant attention due to its versatile applications. Traditional synthetic methods, dating back over a century, have evolved into innovative strategies leveraging catalytic C–H bond activation, transition-metal-free protocols, and photo-induced oxidative cyclization. Recent advancements highlight the synergistic roles of catalysts, oxidants, and solvents in enhancing molecular reactivity and reaction efficiency. This review systematically summarizes state-of-the-art oxidative annulation techniques for quinoline synthesis, emphasizing mechanistic insights and practical applications.

A concise and efficient protocol for the synthesis of various 2-alkenylindole derivatives is developed through [4 + 1] annulation starting from aminobenzyl phosphonium salts and cinnamaldehydes.

Phosphazene superbases have emerged as a pivotal class of metal-free organic catalysts, demonstrating remarkable versatility and efficiency in modern synthetic chemistry. This review systematically summarizes the catalytic applications of P4-t-Bu, a prominent member of the phosphazene superbase family, across diverse organic transformations over the past fifteen years. Key reactions include copolymerization of epoxides with dihydrocoumarins, cyclization processes (e.g., benzofuran synthesis and iodoaminocyclization), and nucleophilic substitutions of fluorinated and methoxylated aromatics. Through a comprehensive analysis, we highlight P4-t-Bu’s unique advantages as a green catalyst, such as its exceptional basicity, broad substrate compatibility, and operational simplicity under mild conditions. Mechanistic insights into its high regio- and stereoselectivities are also discussed. By critically evaluating recent advances and current limitations, this review aims to serve as a valuable resource for researchers developing sustainable catalytic methodologies in organic synthesis, while outlining future directions for phosphazene superbase applications.

3,4-Dihydroquinolin-2(1H)-ones represent a class of valuable bioactive compounds with six-membered nitrogen-containing heterocyclic structures. The development of simple, mild and efficient synthetic methods has been widely concerned by synthetic chemists. In this review, we have summarized a series of different synthetic strategies for the synthesis of dihydroquinoline-2(1H)-ones via catalytic annulation of α,β-unsaturated N-arylamides in the past decade, including covering electrophilic cyclization, radical initiated cyclization and photochemical cyclization reactions. Besides, the substrate scope and mechanistic details are also discussed. This paper will provide a useful reference for the development of diverse synthesis methodologies of 3,4-dihydroquinolin-2(1H)-ones.