A Facile One Step Synthesis of 3-(3-Μετηυl-Ιsoχαζolo[4,5-B] Pyridin-N-Oxide-6-Yl)chromen-2-Ones and Their Deoxygenation

Abstract

A simple and efficient method has been developed for the synthesis of chromene substituted isoxazolo[4,5-i]pyridine-A-oxides 3 from 3,5-dimethyl-4-nitroisoxazole 1 and substituted 3-acetyl-2-oxo-2//-3-chromenes 2 in presence of piperidine. Pyridin-A'-oxides 3 are deoxygenated to corresponding pyridines 4 by treatment with PC1 3 .'H NMR spectrum of the product 3a showed three singlets δ 2.2, 7.2 and 8.1 due to methyl and C-7 and C-5 protons of Α-oxide ring. Chromene ring proton appeared as a singlet at δ 8.4. IR spectrum showed the Α-oxide peak at 1420 cm" 1 . The mass spectrum showed the molecular ion peak at m/z 294 indicating the formation of pyridine-N-oxide.