Methyl 5-Imino-2-methyl-1,10a-dihydro-5H-chromeno[2,3-b]pyridine-3-carboxylate

Abstract

Multicomponent reactions are valuable synthetic tools to deliver highly functionalized motifs starting from simple building blocks in only one step and in an atom-economical way. Herein we disclose the structure of a new and unexpected compound, the methyl 5-imino-2-methyl-1,10a-dihydro-5H-chromeno[2,3-b]pyridine-3-carboxylate, which was formed in the ohmic-heating-assisted multicomponent Hantzsch reaction of 3-formylchromone with methyl acetoacetate and ammonium acetate, in aqueous medium, in the presence of tetrabutylammonium bromide as phase transfer catalyst. The title compound was isolated with no need of chromatographic separation and was analyzed by nuclear magnetic resonance (1H and 13C-NMR, HSQC and HMBC) spectroscopy, mass spectrometry (MS) and high-resolution mass spectrometry (HRMS). Its formation as the main reaction product was observed when the reaction was performed using ohmic heating, which may lead to some speculations about the possible existence of specific effects of ohmic heating in the reactivity pathway because of the passage of an alternating electric current of high frequency within the reaction media, opening new opportunities for further investigations of the potential of this thermal processing method in organic synthesis and reactivity optimization.