Ligand and solvent control of selectivity in the C–H activation of a pyridylimine-substituted 1-naphthalene; a combined synthetic and computational study

摘要: The pyridylimine-substituted 1-naphthalenes, 2-(1-C10H7)-6-{CRN(2,6-i-Pr2C6H3)}C5H3N (R = Me HLMe, H HLH), react with Na2[PdCl4] in acetic acid at elevated temperature to afford either ortho-C–Hnaphthyl activated (LMe)PdCl (2ortho) or the unactivated adduct (HLH)PdCl2 (1b). Alternatively, 1b and its ketimine analogue (HLMe)PdCl2 (1a), can be prepared by treating (MeCN)2PdCl2 HLMe HLH chloroform room temperature. Regio-selective ortho-C–H activation form 2ortho also initiated thermolysis of 1a acid, while no reaction occurs under similar conditions 1b. Interestingly, C–H give is found reversible 100% deuteration peri-site occurring on reacting acid-d4. By contrast, heating toluene gives a 55 : 45 mixture peri-activated isomer 2peri. Pure 2peri can, however, obtained from (LMe)PdOAc (3peri) OAc/Cl exchange sequential reactions firstly silver acetate then aqueous sodium chloride. Intriguingly, peri ortho interconversion 2ortho. DFT calculations have been used investigate steps it that kinetically thermodynamically favoured but peri-CH accessible (ΔΔG‡ 2.4 kcal mol−1). contrast toluene, appears irreversible difference barrier height for ortho- peri-C–H being very small within error method 0.7 mol−1), findings are agreement empirically observed product distribution Single crystal X-ray structures reported 1a, 1b,