Synthesis of 2,3-dihydroquinazolinimines and 1,3-diimino isoindolines catalyzed by rare earth metal alkyl complexes through tandem addition/cyclization of nitriles with amines

Abstract

Mononuclear rare-earth metal alkyl complexes with an anilido-imino ligand were synthesized and characterized, and their catalytic ability for the formation of dihydroquinazolines and isoindolines from nitriles and amines was investigated. Reactions of rare-earth-metal trialkyl complexes RE(CH2SiMe3)3(THF)2 with the proligand HL (L= (o-(NHDipp)C6H4CH=N(CH2)2NC4H8, Dipp = 2,6-iPr2C6H3) in toluene afforded tridentate anilido-imino rare-earth metal dialkyl complexes LRE(CH2SiMe3)2 (RE = Gd (1a), Y (1b), Yb (1c), Lu (1d)) in good yields. Further study showed that these rare-earth metal catalysts could fulfill tandem addition/cyclization between ortho imine-functionalized benzonitriles and aromatic amines to afford 2,3-dihydroquinazolinimines for the first time. In addition, the catalysts are well applied to the reaction of substituted phthalonitriles with primary aromatic and aliphatic amines, producing various 1, 3-diimino isoindolines in moderate to excellent yields. During the process of mechanism study, two anilido yttrium complexes LY(NHPh)2(THF) (7b) and LY(NHDipp)2 (8b) were isolated by the reaction of 1b with aniline and 2,6-diisopropylaniline, respectively as well as their catalytic performance.