1.2- Dichloroethane deprotonation

Despite the favorable properties of acetonitrile as a solvent, its use for equilibrium acidity measurements has its definite limitations. The pK range that is tolerable is limited at the high end by onset of solvent deprotonation, and at the low end by substrate autodissociation, as has been implicated for HCo(CO)4 [14a] and TpCr(CO)3H [22b]. These limitations can be overcome by the choice of a less polar solvent, e.g. 1,2-dichloroethane (DCE), dichloromethane, or THE. To make reliable, quantitative comparisons of thermodynamic data obtained in different solvents, it is necessary to link the acidity scales and electrode potential references in the different solvents. This has all too often proven to be a far from trivial task. Although, in principle, 1 1 relationship between the acidity scales in different solvents never exists, pK differences between closely related compounds are often almost constant when compared in different solvents. This is because their solvation properties are similar, because of similarities in size and charge distribution. In less... 

Terminal alkenes react with PdCl2 in dichloroethane to give internal palladium allyls. Since deprotonation of these alkenes should lead to terminal l-S-Tj -allyls, previous isomerization of the terminal alkene to an internal one must occur in the reaction medium. This parallel reaction should be controlled to ensure the regioselectivity and yield of the 77 -allylpalladium product. ... 

The data are reproduced in Table 1.2, below. Note that chloroform seems to be the best solvent, but recall also that it can readily be deprotonated. Dichloromethane and 1,2-dichloroethane seem to be about equally effective in solvating the salts, but methylene chloride is less prone to undergo substitution than dichloroethane, although the latter s higher boiling point can be an advantage. We also note that in at least one case, special solvent properties have been attributed to ethyl acetate [56]. 

Addition to Enones. Vinylboronic acids 11 can be added in a 1,4-fashion to indole-enones 10 in the presence of 15 mol% Ugand, 10 mol% Mg(OtBu)2, 4A molecular sieves, and 1,2-dichloroethane as the solvent at 70 °C (eq 4). Both 2- or 3-substituted indoles are tolerated, as well as aryl- or alkyl-substituted boronic acids or esters. Under these mild conditions, protection of the indole NH is not necessary, although Boc or Me groups do not affect either the yields or enantioselectivities. Boronic acid 11 reacts with the BINOL ligand to form a reactive boronic ester, which is believed to form an ate complex with the carbonyl group of the electrophile. The exact role of Mg(OtBu)2 is not known, but a likely possibility is deprotonation of the BINOL ligand. 

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