Advances in gold catalyzed synthesis of quinoid heteroaryls

Abstract

This review explores recent advancements in synthesizing quinoid heteroaryls, namely quinazoline and quinoline, vital in chemistry due to their prevalence in natural products and pharmaceuticals. It emphasizes the rapid, highly efficient, and economically viable synthesis achieved through gold-catalyzed cascade protocols. By investigating methodologies and reaction pathways, the review underscores exceptional yields attainable in the synthesis of quinoid heteroaryls. It offers valuable insights into accessing these complex structures through efficient synthetic routes. Various strategies, including cyclization, heteroarylation, cycloisomerization, cyclo-condensation, intermolecular and intramolecular cascade reactions, are covered, highlighting the versatility of gold-catalyzed approaches. The comprehensive compilation of different synthetic approaches and elucidation of reaction mechanisms contribute to a deeper understanding of the field. This review paves the way for future advancements in synthesizing quinoid heteroaryls and their applications in drug discovery and materials science.

Fig. 1. The structures of some gold catalysts (a–f) aid quinoid heteroaryl synthesis.

Scheme 1. (A) Gold-catalyzed synthesis of 1b, (B) proposed reaction mechanism for synthesis of 1b.

Scheme 2. Gold-catalyzed synthesis of quinazoline 1e oxide.

Scheme 3. Synthesis and proposed reaction mechanism for the synthesis of 1h at optimized conditions.

Scheme 4. (A) Divergent synthesis of quinazolines analogues (1j–1l) under optimized reaction conditions. (B) Synthesis of 1o, optimized reaction conditions.

Scheme 5. Experiments for mechanistic consideration and proposed reaction mechanism for 2c.

Scheme 6. Plausible reaction pathway and optimized reaction conditions for the synthesis of 2f.

Scheme 7. At optimized conditions proposed reaction mechanism for synthesis of 2h.

Scheme 8. Synthesis and possible reaction mechanism of 2j at optimized conditions.

Scheme 9. Synthesis and possible reaction pathways for production of 2i.

Scheme 10. Synthesis and possible reaction pathways for production of 2o.

Scheme 11. Synthesis and possible reaction route for production of 2r.

Scheme 12. Synthesis and proposed reaction mechanism for 2u at optimized conditions.

Scheme 13. (A) Synthesis of 2x at optimized reaction conditions. (B) Synthesis and catalyst-controlled divergent cycloisomerization at optimized conditions.

Scheme 14. Synthesis and proposed reaction pathways for 3g at optimized reaction conditions.

Scheme 15. Synthesis and possible reaction mechanism for 3i at optimized conditions.

Scheme 16. (A) The hydrogenation of quinoline using AuNPs/JPS. (B) Hydrogenation of quinoline into py-THQ at optimized reaction conditions. (C) Synthesis of 2l at optimized conditions.