Efficient Ni^II₂Ln^III₂ Electrocyclization Catalysts for the Synthesis of <i>trans</i>-4,5-Diaminocyclopent-2-enones from 2‑Furaldehyde and Primary or Secondary Amines

A series of heterometallic coordination clusters (CCs) [NiII2LnIII2(L1)4Cl2(CH3CN)2] 2CH3CN [Ln = Y (1Y), Sm (1Sm), Eu (1Eu), Gd (1Gd), or Tb (1Tb)] were synthesized by the reaction of (E)-2-(2-hydroxy-3-methoxybenzylidene-amino)­phenol) (H2L1) with NiCl2·6­(H2O) and LnCl3·x­(H2O) in the presence of Et3N at room temperature. These air-stable CCs can be obtained in very high yields from commercially available materials and are efficient catalysts for the room-temperature domino ring-opening electrocyclization synthesis of trans-4,5-diaminocyclopent-2-enones from 2-furaldehyde and primary or secondary amines under a non-inert atmosphere. Structural modification of the catalyst to achieve immobilization or photosensitivity is possible without deterioration in catalytic activity.一系列异金属配位簇（CCs）[NiII2LnIII2(L1)4Cl2(CH3CN)2]·2CH3CN [镧系金属（Ln）= 钇(1Y)、钐(1Sm)、铕(1Eu)、钆(1Gd)或铽(1Tb)]，通过(E)-2-(2-羟基-3-甲氧基苯亚氨基)苯酚（H2L1）与六水合氯化镍（NiCl2·6H2O）、水合氯化稀土（LnCl3·xH2O）在三乙胺（Et3N）存在下于室温反应合成得到。这类空气稳定的CCs可由市售原料以极高产率制备，且在非惰性气氛下可作为高效催化剂，用于由2-糠醛与伯、仲胺经室温多米诺开环电环化反应合成反式-4,5-二氨基环戊-2-烯酮。可对该催化剂进行结构修饰以实现固定化或光敏性，且不会降低其催化活性。