Recent Advances in the Synthesis of Thienoquinolines (Quinoline‐fused heterocycle)

Abstract

Over the past few decades, thienoquinolines have gained considerable attention due to their biological and synthetic applications. Few reports have been disclosed on Thienoquinoline synthesis. Hence, in the present review, we provided a comprehensive update on the synthesis of Thienoquinolines. A brief description of the preparation procedure, reactivity, and mechanisms are included, where as possible. Respectively, the thienoquinoline synthesis is classified and summarized based on its reactivity, so it will help the researchers to obtain knowledge over the previous literature reports to overcome their problems in designing a new process.

Access to Thienopyridine and Thienoquinoline Derivatives via Site-Selective C–H Bond Functionalization and Annulation

“…The major synthesis of thieno­[3,2- b ]­pyridines via the sulfur cyclization reaction between 3-ethynyl-2-thiopyridines and electrophilic species such as Br 2 , I 2 , NIS, and MPHT is among the most general and versatile synthetic methodologies (Scheme a, i) . Another efficient approach for the synthesis of thienopyridines or thienoquinolines is the cyclization of 2-halo-3-ethynylpyridines or 2-haloquinolinyl ketones (Scheme a, ii) . However, to the best of our knowledge, the direct utilization of 3-ethynylpyridine and 3-ethynylquinoline derivatives as starting materials to synthesize thienopyridine and thienoquinoline has not yet been reported.…”

Mo–Catalyzed One‐Pot Synthesis of N‐Polyheterocycles from Nitroarenes and Glycols with Recycling of the Waste Reduction Byproduct. Substituent‐Tuned Photophysical Properties

“…Thienoquinolines, quinoline fused heterocycles with a sulfur atom, possess different interesting and promising biological activities [30] . The two main types of thienoquinolines depend on the fused sulfur ring position to the quinoline moiety: thieno[ b ]quinolines and thieno[ c ]quinolines [31] . For their synthesis, some methods have been reported, [32] including the reaction of 2‐(thiophen‐3‐yl)anilines with aromatic aldehydes [33] .…”

“… [30] The two main types of thienoquinolines depend on the fused sulfur ring position to the quinoline moiety: thieno[ b ]quinolines and thieno[ c ]quinolines. [31] For their synthesis, some methods have been reported, [32] including the reaction of 2‐(thiophen‐3‐yl)anilines with aromatic aldehydes. [33] Based on our previous results, we suggested (2‐nitrophenyl)‐substituted thiophenes and benzothiophenes 13 , 15 , and 17 as plausible starting materials.…”

Recent Advances in the Synthesis of Fused‐Cyclic Quinolines

“…[20] Hence, by placing emphasis on the importance of fused quinoline backbones, some reviews focus on tricyclic fused-quinoline, [21] fused tetracyclic quinoline [22] and quinoline-fused heterocycles with sulfur atom. [23] This review provides a comprehensive compilation of fused homo/heterocyclic rings to the quinoline backbone. This fused structures are classified according to the ring volume starting from four-membered up to the eight-membered cycles.…”

“…[121][122][123] There-fore, sizeable efforts have been made for construction of this valuable scaffold. [23] Rao et al introduced a cyclization reaction approach for the preparation of thienoquinolines. [124] The reaction between 2chloro-3-formyl quinoline 155 and methyl thioglycolate 156 in the presence of DBU as base gave thieno[2,3-b]quinoline derivatives 157 (Scheme 50).…”