Abstract
The effect of donor ligands, usually expected to enhance the reactivity of organolithiums, was studied on the addition of PhLi to E-cinnamaldehyde in THF, under conditions that lead the reaction toward the production of 1,3-diphenylpropanone. It was observed that in the presence of TMEDA and HMPT, the rate of that reaction becomes slower than in the absence of ligands; the effect of HMPA was even more spectacular, at concentration [HMPA]: [PhLi] ≥ 4 the reaction becomes almost completely inhibited. These results show the complexity of solvation effects on the reactions of organolithiums and how substrate-reagent-ligand-solvent interactions are usually specific for the system under study.
Highlights
The seminal work by Seebach in 1984, followed by a second work in 1988, alerted synthetic chemists on the effects of aggregation of organolithium compounds.[1]
We have recently reported how mixed aggregates with the amine acting as a proton donor can be constructively used for the synthesis of complex molecules.[7]
The reaction of E-cinnamaldehyde, 1, with phenyllithium in THF was studied under several reaction conditions
Summary
The seminal work by Seebach in 1984, followed by a second work in 1988, alerted synthetic chemists on the effects of aggregation of organolithium compounds.[1]. For PhLi: [1] = 2 , at room temperature and long times of reaction, a more interesting compound, the 1,3-diphenylpropanone, 3, is the main reaction product; traces of the chalcone 4, are formed in variable amounts.[9] (equation 1). The sensitivity of the reaction to concentration and solvent effects, could indicate that the subtle equilibrium between monomer and oligomers of PhLi could be responsible for the observed results.
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