JPH05247010

PURPOSE:To obtain a new 7-hydroxy-2-methyl-2H-1,4-benzoxazin-3-one derivative, having high selectivity for noxious weeds and useful as an intermediate for phenoxybenzoxazine-based herbicides effectively usable in a small amount. CONSTITUTION:The objective compound is expressed by formula I (R is lower alkoxycarbonyl, lower aliphatic acyl or CN), e.g. 3-ethoxycarbonyl-7-hydroxy-3- methyl-2H-1,4-benzoxazin-3-one. This compound can readily be produced by reacting a 2-(3-hydroxyphenoxy)propionic acid derivative expressed by formula II (R is lower alkyl) with a diazonium salt of aniline or its derivative such as p-aminobenzoic acid or sulfanilic acid, especially the diazonium salt obtained by reacting the sulfanilic acid with sodium nitrite, providing a diazo compound, then reducing the resultant diazo compound with a reducing agent, especially Na2S2O4 and cyclizing the prepared compound.