A Comparison of the Reactions of lithium with α,β-Unsaturated Ketones and Those of Other Acyl Anion Equivalents Containing Sulfur

Article abstract of DOI:10.1021/jo00371a014

The factors influencing the site of attack of <(phenylthio)(trimethylsilyl)methyl>lithium (1) with enones were investigated.Cyclohexenone (2) was chosen as a model compound, and conjugate addition occurred in THF-HMPA or DME; this mode of addition was also promoted by a potassium counterion.When the reaction was carried out with other enones, conjugate addition in THF-HMPA or DME was only observed if the β-position or the α,β-unsaturated ketone was not disubstituted. 1,4-Addition of 1 could be accomplished by preparation of the cuprate.The use of this approach was illustrated by a preparation of 4,4-dimethylcyclopent-2-en-1-one (28).For determination of the influence of DME on the regiochemical control of the addition of other sulfur-containing anions to enones, the study was extended to the anions derived from 1,3-dithian (29), bis(phenylthio)methane (30), bis(phenylthio)(trimethylsilyl)methane (35), and bis(trimethylsilyl)(phenylthio)methane (36).With these anions, DME did not promote conjugate addition to any significant extent.