Using monobenzylated malononitrile, the chiral amine 2 h having adjacent quaternary carbon center was obtained in 97% yield with 93% ee. This suggests the strong catalyst activity of the dinuclear L1-Pd2 complex. We assumed that the highly active dinuclear L1-Pd2 catalyst would facilitate the conversion of the Mannich adducts (2a–d) to the second Mannich reaction for giving the 1,3-diamines 3. Actually, the use of L1-Pd2 with a Zn(OAc)2 catalyst system resulted in the production of a significant amount of the 1:2 adduct 3, as desired. For the synthesis of 2f and 2g, co-production of the same amount of diamines was observed even when 1.5 equiv. of malononitrile was applied to the imine substrate24,25. For the double Mannich reaction, the reaction conditions were modified so that 2.5 equiv. of N-Boc imine were used with respect to the malononitrile. L1-Pd2 with Zn(OAc)2 catalyzed the double Mannich reaction quite smoothly to give the 1,3-diamine 3a in quantitative yield with high diastereoselectivity (dl/meso = 93/7)26–43. The major dl-isomer was obtained in 99% ee. The results of 1,3-diamine synthesis by the double Mannich reaction are summarized in Fig. 5.Figure 5Catalytic asymmetric double Mannich reaction.