NEW MATERIAL:The compound of formula I (R1 is aryl or polycyclic aromatic aryl).

USE: A dye easily forming 4-phenylazo-1-naphthol and 2-phenylazo-1-naphthol which are red azo dyes. It generates aryl radical and naphthoxy radical in high yield and is useful in the field of synthetic chemistry.

PREPARATION: An α-azohydroperoxide of formula II (R2 and R3 are H, 1W4C alkyl, aryl or polycyclic aromatic aryl or R2 and R3 together form -(CH2)4W7-; R4 is aryl or polycyclic aromatic aryl) is dissolved in a solvent and a crystalline solid or liquid of α-azohydroperoxide containing solvent molecule is separated from the solution. The obtained solid or liquid is mixed with 1-naphthol and the solvent is removed from the mixture to obtain the objective compound of formula I.