A FACILE APPROACH FOR THE SYNTHESIS OF NOVEL XANTHENE DERIVATIVES WITH VILSMEIER–HAACK REAGENT

Abstract

A series of new derivatives of formylxanthenes have been synthesized via the reaction of substituted 1,3-benzoxazines with Vilsmeier–Haack reagent. It has been shown that 1,3-benzoxazines unsubstituted in the aromatic part and 6-bromo-1,3-benzoxazines are rearranged into xanthene derivatives under heating at 80°C for 1.5 h. Substitution at the C-8 position of 1,3-benzoxazines, especially with electronegative groups significantly inhibits the reaction. So, the presence of iodine atoms at the C-6 and C-8 positions leads to increase in reaction time up to 8 h, the presence of bromine atom in the C-8 position requires heating up to 100°C for 11 h.