Addition of diphenylacetylene and methylvinylketone to aluminum complex of redox-active diimine ligand

Diphenylacetylene reacts with aluminum complex (dpp-bian)AlEt(Et2O) (1) (dpp-bian = 1,2-bis[(2,6-diisopropylphenyl)imino]acenaphthene) in the absence of any solvent at 110–130 °C under vacuum to give compound [dpp-bian(PhCdouble bond; length as m-dashCPh)]AlEt (2). The reaction of methylvinylketone with complex 1 easily proceeds at ambient temperature in Et2O and results in the formation of compound [dpp-bian(CH2–CHdouble bond; length as m-dashC(Me)–O)]AlEt (3). Both reactions proceed via addition of unsaturated organic substrate across Al–N–C bond sequence in complex 1. Complexes 2 and 3 have been characterized by IR and 1H NMR spectroscopy. Molecular structures of 2 and 3 have been determined by single-crystal X-ray analysis. Complex 2 was found to be catalyst for the reaction between phenylacetylene and diphenylamine. A full conversion of the reagents was achieved with 5 mol% of complex 2 in benzene in 140 h at 110 °C resulting N-phenyl-2-(1-phenylvinyl)aniline (4a) as the major product (87%).