Regio‐ and stereoselective synthesis of 1‐benzopyrano[2,3‐b]pyrrolo[2,3‐d]pyridines: A microwave‐accelerated intramolecular [3+2] cycloaddition reaction of azomethine ylide

Abstract

in Wiley Online Library (wileyonlinelibrary.com).Regio-and stereoselective syntheses of tetracyclic compounds having chromone, pyrrolidine, and piperidine rings have been accomplished by an intramolecular [3þ2] cycloaddition reaction involving azomethine ylide. The reactions were carried out thermally as well as by irradiation with microwave. The latter process accelerates the reaction. The selectivities were investigated by density functional theory computation.

Amine-Controlled Reduction of 2-Aminochromone-3-Carbaldehyde with Zn and Acetic Acid

“…60-80 o C. 2-Aminochromone-3-carbaldehydes 1 were prepared following a literature procedure. 27 All other chemicals used were of commercial grade and were used as such.…”

“…During the last few years we have been engaged in synthesising various polycyclic heterocycles using 2-aminochromone-3carbaldehydes 1 as a building block. [26][27][28] We have reported the deformylation of 1(R 2 = alkyl, R 3 = H) by heating with 70% aqueous H 2 SO 4 , where the C-2 amino group in the chromone ring initiates the reaction. 29 This observation prompted us to study the reduction of 1 where the C-2 amino group may participate in the reduction process.…”

A One-Pot Rearrangement of 2-(N-Alkyl-N-aryl)aminochromone-3-carbaldehyde to N-Alkyl-3-salicyloyl-2-quinolone - An Antileishmanial Agent

“…Nitrobenzenes having varying substituents were employed for the synthesis of 3, which on subsequent methylation (→ 4a-e) and rearrangement by heating in acetic acid containing a few drops of water produced 6a-e in excellent yields (Table 1, entries 1-5). Alkylation was also performed using allyl or crotyl bromide to obtain N-allylated products 4f-h, 18,19 which, on subsequent heating in acetic acid, produced 6f-h (entries 6-8). Functionalgroup tolerance was tested using ester, nitro, or methoxy substituents, and the mode of cyclization was tested using a wide range of electron-donating and electron-withdrawing groups at the meta position of the N-aryl moiety in 4.…”

“…14 Latterly, we have utilized 3 for the synthesis of bischromones involving a deformylative Mannich reaction, 15 to prepare chromeno[2,3-b]pyridines with varying substituents at their 3-position. 16 2-(N-allyl-N-aryl)aminochromone-3-carbaldehyde has also been used for intramolecular [3+2]-nitrone cycloaddition reaction at low temperature involving N-methylhydroxylamine, 17 while we have utilized the same compound for intramolecular [3+2]-azomethine ylide cycloaddition reaction 18 and for domino Knoevenagel-hetero Diels-Alder reaction. 19 Different methods for the synthesis of the 2-quinolone moiety have been reported.…”

Lewis Acid‐Catalyzed Intramolecular [3+2] Cross‐Cycloaddition of Aziridine 2,2‐Diesters with Conjugated Dienes for Construction of Aza‐[n.2.1] Skeletons

“…The IMPC regioselectivities of azomethine ylides are inherently attributed to the intramolecular nature of the reactions . An effort to switch the regioselectivity to IMCC failed, and theoretical calculations also indicate that the [3+2]IMPC is much preferred both kinetically and thermodynamically …”