Divergent synthesis of polysubstituted isoxazoles, isoxazoline N-oxides, and dihydroisoxazoles by a one-pot cascade reaction


Rouf A., ŞAHİN E., TANYELİ C.

TETRAHEDRON, vol.73, no.4, pp.331-337, 2017 (Journal Indexed in SCI) identifier identifier

  • Publication Type: Article / Article
  • Volume: 73 Issue: 4
  • Publication Date: 2017
  • Doi Number: 10.1016/j.tet.2016.12.005
  • Title of Journal : TETRAHEDRON
  • Page Numbers: pp.331-337
  • Keywords: Isoxazoline N-oxides, Isoxazoles, Dihydroisoxazoles, Cascade reaction, Ethyl nitroacetate, 1,3-DIPOLAR CYCLOADDITION, REGIOSPECIFIC SYNTHESIS, RING TRANSFORMATION, 4+1 ANNULATION, LEWIS-ACID, 2-OXIDES, DERIVATIVES, NITRILE, 2-ISOXAZOLINES, ANTAGONISTS

Abstract

An efficient one-pot synthesis of a new class of 3,4,5-trisubstituted isoxazoline N-oxides/isoxazoles and dihydroisoxazoles is developed by a green approach from aromatic and aliphatic aldehydes by controlling the reaction conditions. Aldehydes were reacted with ethyl nitroacetate in the presence of DABCO as a catalyst under ultrasonication. In aromatic aldehydes, isoxazoline N-oxides were obtained exclusively when the reaction was carried out at 40 degrees C, but raising the temperature to 80 degrees C isoxazoles were formed selectively. Aliphatic aldehydes, on the other hand, gave a mixture of isoxazoline N-oxides and dihydroisoxazoles where the ratio of these depended on the bulk of the aliphatic chain on the aldehyde. This is the first method for the synthesis of aliphatic 4-substituted-3,5-bis(ethoxycarbonyl)isoxazoline N-oxides and 4-substituted-3,5-bis(ethoxycarbonyl)-dihydroisoxazoles with good to excellent yields. (C) 2016 Elsevier Ltd. All rights reserved.