A theoretical study of the ligand-controlled palladium-catalysed regiodivergent synthesis of dibenzosilepin derivatives

• Published in: Dalton transactions : an international journal of inorganic chemistry 2023-01, Vol.52 (3), p.737-746
• Main Authors: Yan, Xueyuan, Yang, Miao, She, Yuan-Bin, Yang, Yun-Fang
• Format: Article
• Language: English
• Subjects: Alkynes; Chemical synthesis; Density functional theory; Insertion; Ligands; Naphthalene; Palladium; Regioselectivity; Silicon compounds; Silicon substrates; Tethering
• ISSN: 1477-9226; 1477-9234
• DOI: 10.1039/d2dt03767j

Palladium-catalysed ligand-controlled 1, n -palladium migration of silicon-tethering substrates provides a regiodivergent synthesis strategy for constructing silicon-bridged π-conjugated compounds possessing a 6,6-fused or a 5,7-fused scaffold. Density functional theory (DFT) calculations were carried out to elucidate the detailed mechanism of this 1, n -palladium migration involving syn - or anti -carbopalladation. The computational results suggest that alkyne insertion is the regioselectivity-determining step. Upon catalysis without the BINAP ligand, the 1,2-insertion of an alkyne into the Pd-aryl bond leads to the formation of 6,6-fused benzophenanthrosiline, which is more favorable than the 2,1-insertion of alkyne by 4.2 kcal mol −1 . The selective formation of 5,7-fused benzofluorenosilepins via the 2,1-alkyne insertion is facilitated by the BINAP ligand. The 1,2-alkyne insertion with the BINAP ligand is disfavoured due to the steric repulsion between the phenyl group of the substrate and the naphthalene group of the BINAP ligand. The 2,1-alkyne insertion with the BINAP ligand orients the ligand away from the phenyl group of the substrate, which can avoid steric repulsion. The mechanism and origin of the regioselectivity of ligand-controlled palladium-catalysed reigodivergent synthesis of silicon-bridged π-conjugated compounds were elucidated with density functional theory calculations.