Chemistry of Enolates .7. Kinetics and Orientation in Dimethyl Sulfoxide - Relative Nucleophilicities of Enolates

Abstract

Lithium, sodium, and cesium enolates are prepared in dimethyl sulfoxide by titration of ketones with methylsulfinyl carbanion, CH3SOCH2-. Rates of enolate alkylation in DMSO are 103-fold greater than in glyme solvents, and 0-/C-alkylation ratios are substantially larger and more nearly independent of the cation. Carbon

Regiochemistry in alkylation, acylation and methoxycarbonylation of alkali salts from 2-substituted alkenylpropanedinitriles

“…In the alkylation of the enolate of propiophenone with n-pentyl halides the O/C-quotient is 1.2, 0.64 and 0.23, respectively, on going from Cl to Br to I. 16 We observed a similar trend in 1-Me/3-Me: Tf 3.57, Br 1.85, I 0.88 (expts. 4, 3, 1).…”

Glymes as versatile solvents for chemical reactions and processes: from the laboratory to industry

“…For example, the alkylation rates of alkali enolates in DMSO were found to be 1,000-fold faster than that in glymes (mono- and di-) although the same reaction was even slower in diethyl ether. 282 …”

Palladium catalysed aryl enol ether synthesis from vinyl triflatesElectronic supplementary information (ESI) available: experimental. See http://www.rsc.org/suppdata/cc/b3/b307574e/

“…Enol ethers are useful functional groups for exploitation in synthesis and find use in a range of processes, for example they function as nucleophiles in ene and aldol-type additions, 1 as acyl anion equivalents, 2 Diels-Alder dienophiles 3 and as monomers in the production of oxygen containing vinyl polymers. 4 Traditional methods for their preparation include the O-alkylation of enolates, 5 Wittig alkenylation employing Osubstituted phosphoranes, 6 titanium mediated alkenylation of carboxylic esters, 7 the addition of alcohols to acetylenes 8 and dehydrohalogenation of 2-haloethyl ethers. 9 The synthesis of aryl enol ethers is particularly challenging and the methods for their preparation are more limited, with transvinylation procedures being generally the most useful.…”