72617-62-0Relevant academic research and scientific papers
Sodium Diisopropylamide in Tetrahydrofuran: Selectivities, Rates, and Mechanisms of Arene Metalations
Algera, Russell F.,Ma, Yun,Collum, David B.
, p. 15197 - 15204 (2017)
Sodium diisopropylamide (NaDA)-mediated metalations of arenes in tetrahydrofuran (THF)/hexane or THF/Me2NEt solutions are described. A survey of >40 benzenoid- and pyridine-based arenes with a range of substituents demonstrates the efficacy and regioselectivity of metalation. Metalations of activated disubstituted arenes and selected monosubstituted arenes are rapid at -78 °C. Rate studies of 1,3-dimethoxybenzene and related methoxylated arenes show exclusively monomer-based orthometalations with two or three coordinated THF ligands. Rate studies of the isotopic exchange of benzene and monosubstituted arenes with weakly activating groups reveal analogous di- and trisolvated monomer-based metalations. Cooperative inductive, mesomeric, steric, and chelate effects are discussed.
Photochemistry of Dimethoxybenzenes in Aqueous Sulfuric Acid
Pollard, Renee,Wu, Susan,Zhang, Guangzhong,Wan, Peter
, p. 2605 - 2613 (2007/10/02)
The photochemistry of the three isomeric dimethoxybenzenes (1-3) has been studied in aqueous sulfuric acid.Two processes were found to take place: (i) photoprotonation of the ring resulting in exchange of the ring protons, which was observed for all three compounds and (ii) ipso substitution of the methoxy group by water, which was observed only for 1,2-dimethoxybenzene (3).Both of these photochemical reactions were catalyzed by acid, requiring acidities stronger than pH(D)2 for observable reaction.Quantum yields for proton exchange and ipso substitution are reported as a function of medium acidity.The fluorescence emissions of all three compounds were quenched by acid, to give sigmoid type quenching curves, that have a complementary relationship with the corresponding plots of quantum yield of exchange vs acidity, consistent with protonation of the benzene ring in S1 as the primary photochemical step, to give cyclohexadienyl cation intermediates.Stern-Volmer analysis of fluorescence quenching by proton gave photoprotonation rates in the range 0.09-2.2*109 M-1 s-1.The results of this work demonstrate unambiguously that methoxy-substituted benzenes are much stronger bases in S1 (pKBH+ ca. 1 to -2) than in the ground state.This enhanced basicity is manifested in regioselectivity of exchange of 1 and 3 and ipso substitution chemistry of 3, processes not observed in the ground states of these compounds.
