Coupling of Azomethine Ylides with Nitrilium Derivatives ofcloso-Decaborate Clusters: A Synthetic and Theoretical Study
The azomethine ylides p-R3C5H4N+CH−COC6H4R2-p (3 a: R3=H, R2=H, X=Br; 3 b: R3=H, R2=Me, X=I; 3 c: R3=H, R2=OMe, X=I; 3 d: R3=H, R2=F, X=I; 3 e: R3=Me, R2=Me, X=Br) react with the nitrile functionality of the closo-decaborate clusters [Bun4N][B10H9(NCR1)] (1 a: R1=Me; 1 b: R1=Et; 1 c: R1=Ph) in a CH3NO2 solution under mild conditions (20–25 °C, 2 min) to afford selectively products of the nucleophilic addition (ca. quantitative yields based on NMR analysis in [D6]DMSO, 71–87 % yield of isolated products). These products are the borylated enamino ketones as the salts bearing exclusively a tetrabutylammonium cation [Bun4N][B10H9{NCR1=C(N+C5H4R3-p)COC6H4R2-p}] (4 a–h,k–n) or the mixed salts [Bu…