Reaction of Polyhaloalkyl-Substituted Chromones, Pyrones, and Furanones with Salicylaldehydes as a Direct Route to Fused 2H-Chromenes

Abstract

Polyhaloalkyl-substituted chromones, gamma-pyrones, and beta-furanones react with salicylaldehydes in the presence of piperidine to give a wide variety of fused 2H-chromenes in good yields. This novel annulation reaction presumably proceeds by a tandem intermolecular oxa-Michael addition and subsequent intramolecular Mannich condensation.

Reaction of 2-(trifluoromethyl)chromones with pyridoxal: Formation of 1-benzopyranooxepino- and 1-benzopyranopyranopyridines

“…2-(Polyfluoroalkyl)chromones and oxacyclic 2-(polyfluoroalkyl)-2-en-4-ones condense with salicylaldehydes giving respectively the chromene derivatives 1 and 2 [7]. Similar reactions of the above mentioned substrates with pyridoxal are anticipated to form respectively the azachromenes 3 and 4 with fused acetal moiety ( Fig.…”

Synthetic approaches to 3H‐naphtho[2,1‐b]pyrans and 2,3‐dihydro‐1H‐naphtho[2,1‐b]pyrans

“…Sosnovskikh and coworkers reported an interesting synthesis of a fused oxygen polycycle bearing 3H- (22) in 8% yield by reacting polyhaloalkyl-substituted pyrones with 2-hydroxy-1-naphthaldehyde in presence of catalytic piperidine in refluxing benzene (Scheme 6) [18]. Similar reactions with other substituted salicyaldehydes gave higher product yields (12-94%).…”

“…Similar reactions with other substituted salicyaldehydes gave higher product yields (12-94%). The authors proposed that a threecomponent adduct is initially formed either by Michael addition/Schiff's base formation or through Baylis-Hillman protocol, which cyclizes with concomitant elimination of the secondary amine [18].…”

Synthesis and Transformation of Halochromones

“…During the last decade Sosnovskikh [128,[194][195][196][197][198][199][200][201] and his group continued to devote great attention to the chemistry of 2-(polyhaloalkyl)chromones (2-R F -chromones) 185, particularly 2-(polyfluoromethyl)chromones (2-CF 3 -chromones) [52]. Some of their possible reactions are depicted in (Scheme 60): the reaction with ketimines leading to compounds 186-189 [194,196,198]; with acetophenones in the presence of lithium diisopropylamide to give 2-aroylmethyl-2-R F -chromanones 190 [197]; and a novel annulation reaction with salicylaldehydes in the presence of piperidine that constituted a direct route to chromeno [2,3-b]chromen-11-ones 191 by a tandem intermolecular oxa-Michael addition and subsequent intramolecular Mannich condensation [195].…”

“…Some of their possible reactions are depicted in (Scheme 60): the reaction with ketimines leading to compounds 186-189 [194,196,198]; with acetophenones in the presence of lithium diisopropylamide to give 2-aroylmethyl-2-R F -chromanones 190 [197]; and a novel annulation reaction with salicylaldehydes in the presence of piperidine that constituted a direct route to chromeno [2,3-b]chromen-11-ones 191 by a tandem intermolecular oxa-Michael addition and subsequent intramolecular Mannich condensation [195].…”