An efficient microwave-assisted synthesis of thieno[2,3- b ]quinolines under solvent-free conditions

Abstract

A novel and efficient method for the synthesis of substituted thieno[2,3-b]quinolines has been developed. A simple one-pot reaction of 3-formyl-2-mercaptoquinolines 2a-l with 1-chloroacetone, 2-chloroacetamide, ethyl chloroacetate and 2-chloro-1-phenylethanone in presence of catalytic amount of potassium carbonate under microwave irradiation and solvent-free conditions gave thieno[2,3-b]quinolin-2-ylethanone derivatives 3a-e, thieno[2,3-b]quinoline-2-carboxamide derivatives 4a-e, ethyl thieno[2,3-b]quinoline-2-carboxylate 5a-e and phenyl(thieno[2,3-b]quinolin-2-yl)methanone derivatives 6a-e compounds respectively. The structures of all the newly synthesised compounds were elucidated on the basis of elemental analysis, IR, 1 H NMR and mass spectral data.

Microwave Induced One-Pot Synthesis of Some New Thiopyrano[2,3-b]quinolin-2-ones under Solvent-Free Conditions

“…Hence, in continuation of our studies in the synthesis of condensed quinoline derivatives, [15][16][17][18] due to their significant biological activities, it appeared expedient to synthesize a condensed quinoline that is presented here in the present study.…”

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

“…[22] In this reaction, compound 14 was employed as an opening substrate and reacted with chloroacetone, chloroacetonitrile, and ethyl chloroacetate using fused sodium acetate and ethanol under reflux condition to afford 3amino-2-substituted-thieno In 2005, Mahadevan and co-workers accomplished an efficient and eco-friendly microwave-assisted approach to construct thieno[2,3-b]quinolines from 2-thioxo-1,2-dihydroquinoline-3-carbaldehyde 23 under solvent free reaction conditions. [17] Compound 23 is prepared from 3-formyl-2- chloroquinoline refluxed under acidic conditions using Na 2 S. further intermolecular annulations occurred with chloroacetone, ethyl chloroacetate, chloroacetamide, and 2-chloro-1-phenylethanone in the presence of K 2 CO 3 as a base under microwave conditions to afford various substituted thieno[2,3-b]quinolines 24, 25, 26, and 27 up to 85% yields. (Scheme 6) In 2005, Naik and co-workers successively reported a microwave method for the synthesis of thieno[2,3-b]quinoline-acid and ester analogs 30, from 2-chloro-3-formyl quinolines 28.…”

Aldo‐X Bifunctional Building Blocks for the Synthesis of Heterocycles

“…In fact, the reactivity of 3‐formyl‐2‐mercaptoquinoline is, to some extent, close to that of salicylaldehyde. For example, in the presence of inorganic base, it can react with α‐halogenated ketones to form thieno[2,3‐ b ]quinolin‐2‐ylethanone derivative 104 (Scheme ) . Under microwave irradiation, the cyclization of 3‐formyl‐2‐mercaptoquinoline and phenoxyacetic acid in the presence of a basic catalyst also proceeded very well, affording thiopyrano[2,3‐ b ]quinolin‐2‐one derivatives in good yield …”