Invention relates to prepare 2-amino-5-nitrophenol

A process for efficiently preparing 2-amino-5-nitrophenol derivatives in which benzoxazole derivatives are subjected to nucleophilic substitution reaction at the 5 position thereof to obtain corresponding benzoxazole derivatives, and the oxazole ring of the benzoxazole derivatives is then subjected to ring-opening to obtain 2-amino-5-nitrophenol(CAS NO: 121-88-0) derivatives.

The 2-amino-5-nitrophenol derivatives are useful as industrial starting materials, reducing agents or antioxidants and intermediates for cyan-image-forming couplers.

This invention relates to a process for preparing 2-amino-5-nitrophenol derivatives and more particularly, to a process for preparing 2-amino-5-nitrophenol(CAS NO: 121-88-0) derivatives in which an appropriate nucleophilic group is introduced at the 4 position of the derivative.

2-Amino-5-nitrophenol derivatives are generalpurpose compounds for use as industrial starting materials, and can be converted into synthetic intermediates of higher added value by the reduction of the nitro group. 

The compounds have the o-aminophenol structure which may serve as a reducing agent, and the degree of reducibility can be arbitrarily controlled by the introduction of a suitable substituent and the conversion of the nitro group into another functional group. In this sense, the derivatives are important as diversity of reducing agents or antioxidants or synthetic intermediates which are convertible into physiologically active compounds by the modification of the nitrogen atom.

Moreover, 2-amino-5-nitrophenol derivatives are also important as synthetic intermediates for cyan-imageforming couplers in the field of photographic chemistry. In recent years, it has been found that 2,5-diacylaminophenol cyan-couplers show good color restoration upon development and the resulting dyes have good fastness to heat and/or humidity . 

It has been also found that dyes produced from 2-phenylureido-5-acylaminophenol cyancouplers are excellent in color restoration upon development, absorption wavelength, and fastness to heat and/or humidity. Accordingly, 2-amino-5-nitrophenol derivatives have attracted attention for use as synthetic intermediates for those couplers.

Photographic couplers may be broadly classified with respect to the hue of developed dye. They may also be stoichiometrically classified into two broad classes, i.e. 2-equivalent couplers and 4-equivalent couplers. While 4-equivalent couplers require four moles of silver halide to be developed into one mole of dye, 2-equivalent couplers have a split-off group at the coupling position thereof and can form one mole of dye using two moles of silver halide. 

For this reason, it is known that 2-equivalent couplers are more beneficial from the standpoint of silver saving. With regard to cyan-developing couplers, for instance, 2-equivalent couplers have such a high colordeveloping speed that photographic senistivity is much improved.

As explained above, 2-amino-5-nitrophenol derivatives in which substituents are introduced into the benzene ring are important as industrial starting materials, reducing agents, and intermediates for preparing cyan couplers in photographic chemistry. 

It is a primary object of the present invention to provide a process for preparing 2-amino-5-nitrophenol derivatives, into which various nucleophilic groups are introduced at the 4 position, from inexpensive, readily available starting materials.

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