Sequential 1,3‐Dipolar Cycloaddition of Nitrones to β‐(2‐Aminophenyl) α,β‐Ynones and Cyclocondensation: A New Entry to the Isoxazolino[4,5‐c]quinoline Ring

Abstract

The reaction of β-(2-aminophenyl) α,β-ynones with N-methyl nitrones provides a simple and efficient entry to the isoxazolino[4,5-c]quinoline ring system through a sequential 1,3-dipolar cycloaddition/annulation process.

Annulation of 2‐Alkynylanilines: The Versatile Chemical Compounds

“…[109] In the catalyst-free reaction of β-(2-aminophenyl)-α,βynones 57 with nitril oxides 154, a series of isoxazolo [4,5c]quinolines 156 was synthesized through domino [3 + 2] cycloaddition/imination and annulation/aromatization of 155 (Scheme 46). [110] A series of 2-alkoxyfuro[2,3-c]quinoline 163 was synthesized through a catalyst-free three component reaction of 157, aldehydes, and α-(4-nitrophenyl)-α-isocyanoacetate 158. The progress of this reaction relies on the sequential formation of imine 159, nucleophilic addition of isocyanoacetate to the latter, cyclization of 160 to give oxazole 161, Diels-Alder cycloaddition furnishing intermediate 162, retro-Diels-Alder reaction for removal of aryl nitrile, and oxidation process to access the final fused heterocycle 163 (Scheme 47).…”

Tandem Reactions of Ynones: via Conjugate Addition of Nitrogen‐, Carbon‐, Oxygen‐, Boron‐, Silicon‐, Phosphorus‐, and Sulfur‐Containing Nucleophiles

“…N ‐Oxides, including quinoline N ‐oxides or isoquinoline N ‐oxides, N ‐methylnitrones and in situ generated N ‐oxides, could be incorporated in the final products. Usually, no metal catalyst was required (Scheme ).…”

Sequential Addition and Cyclization Processes of α,β-Ynones and α,β-Ynoates Containing Proximate Nucleophiles

“…The isoxazolino[4,5-c]quinolines 44 were isolated in moderate to high yields as single regioisomers. 72 As shown in Figure 5, the reaction tolerates various functional groups, such as keto (44a,b), nitrile (44d), and ester (44h) groups; vinyl (44a-c) and heteroaryl (44f) substitu-ents are also allowed on the isoxazoline moiety. Moreover the isoxazolino[4,5-c]quinoline 44i, substituted on the benzene ring of the quinoline, was also obtained in good yield.…”