To obtain the subject new compound consisting of a hydroxybiarylphosphine produced by the reaction of a specific oxaphosphorin with an organometallic compound and useful e.g. as an intermediate for a ligand for an enantio-selective hydroformylation reaction.

This new hydroxybiarylphosphine is expressed by formula I [Ar-Ar is biphenyl, 1-phenylnaphthyl or 1,1'-binaphthyl; R1 and R2 are each F, Cl, a 1-8C alkyl, alkoxy or a (substituted)aryl; (a) and (b) are each an integer of 0-4; R3 and R4 are each a 1-8C alky, a 4-10C cycloalkyl, a 7-9C alkaryl, etc.] and is useful e.g. as a synthetic intermediate for a phosphinophosphite which is a ligand of a catalyst to be used in an enantio-selective hydroformylation reaction. The compound can be produced by reacting an oxaphosphorin expressed by formula II (X is Cl or Br) with compounds of the formula R3-Me (Me is a univalent metal) and the formula R4-Me.