In 1890 Hirsch3 reported that diazo compounds can be extracted from aqueous solution by phenols and upon heating react to form hydroxybiphenyls. The reaction medium was kept acid so that no azo-type coupling occurred. Norris, Macintire and Corse4 later studied this reaction, reporting similar results together with the formation clf a black, brittle material probably formed by the introduction of several phenyl groups into the diazo nucleus. ...
