An allyl compound having a formula different from that of an allyl starting compound is prepared by a process of reacting the allyl starting compound with a nucleophilic agent in the presence of a catalyst containing at least one transition metal compound containing a transition metal selected from the group consisting of elements belonging to Group 8 to Group 10 of the Periodic Table and at least one bidentate coordinated phosphite compound selected from the group consisting of compounds having the following formulae (I) to (III): ##STR00001## wherein A.sup.1 to A.sup.3 are respectively independently a diarylene group having a branched alkyl group at the ortho-position, R.sup.1 to R.sup.6 are respectively independently an alkyl group which may have a substituent or an aryl group which may have a substituent (including a heterocyclic compound forming an aromatic 6.PI. electron cloud on the upper and lower sides of the ring, hereinafter the same), and Z.sup.1 to Z.sup.3 are respectively independently an optionally substituted alkylene group, an optionally substituted arylene group, an optionally substituted alkylene-arylene group or an optionally substituted diarylene group.