Reaction of 2-methyl-2,3,5,6,7,8-hexahydro-4H-1,3-benzoxazin-4-one with diazonium salts

Abstract

We found that the interaction of 2-methyl-2,3,5,6,7,8-hexahydro-4H-1,3-benzoxazin-4-one with various activated and non-activated diazonium salts in hydrochloric and acetic acids leads to the formation of corresponding previously unknown arylhydrazones with high yields, independent of the structure of the diazo component. The azo coupling reaction proceeds at the non-activated sp3-hybrid C-8 atom due to the activating action of the acid medium with the formation of 2-methyl-6,7-dihydro-2H-1,3-benzoxazine-4,8(3H,5H)-dione 8-arylhydrazone. This reaction proceeds regioselectively at the C-8 atom due to steric hindrances, namely the large size of the diazonium salts. The structures of the synthesized arylhydrazones were confirmed by modern physicochemical methods of analysis including 1Н NMR spectroscopy and mass spectrometry. The discovered reaction allows synthesizing arylhydrazones, which are difficult to access by other methods in one step. Isolation of the reaction products is not difficult and can be achieved by simple filtration after neutralization. The resulting arylhydrazones can be used as building blocks in organic synthesis and as ligands for binding metal ions.