PURPOSE: To advantageously carry out conjugated addition reaction useful for producing industrial raw materials, etc., by regioselectively adding a conjugated unsaturated compound to an organolithium compound under action of an organoaluminum compound.

CONSTITUTION: A conjugated unsaturated compound having an electron attractive group, such as CO, CS, CH=N, C=N-OH, C=N or NO2, conjugated with carbon-carbon double bond or triple bond, preferably a conjugated unsaturated ketone is reacted with an organolithium compound under action of an organoaluminum compound, preferably a triorganoaluminum having a hydrocarbon group and oxyhydrocarbon group, especially alkylaluminumbis(2,6-di-tert- butyl-4-alkylphenoxide) to regioselectively afford a conjugated addition product useful for producing various industrial raw materials or physiologically active substances using an organometallic reactant, available in large amounts and readily producible as commercially available product.