173031-53-3Relevant articles and documents
Chiral Carbanions, 1. - Configurational Stability and Reactions of α-Acyloxy-Substituted α-Methylbenzyllithium Compounds
Hammerschmidt, Friedrich,Hanninger, Achim
, p. 1069 - 1078 (2007/10/03)
Racemic and optically active 1-phenylethyl esters of pivalic, (-)-camphanic and 2,4,6-triisopropylbenzoic acid were prepared.The esters 7a of pivalic acid were deprotonated with lithium 2,2,6,6-tetramethylpiperidide (Li-TMP) to form α-oxy-α-methylbenzyllithium compounds which are partly configurationally stable prior to acylation with starting material.Camphanic ester (-)-7b cannot be deprotonated by Li-TMP and t-BuLi is added to the ester function to afford ketone (-)-12a. 1-Phenylethyl 2,4,6-triisopropylbenzoates 16 were transformed within minutes to carbanions 19 by using s-BuLi/TMEDA in THF, hexane, toluene and s-BuLi without TMEDA in toluene/20percent diethyl ether at -78 deg C.The carbanions are configurationally stable only in toluene/20percent diethyl ether and racemise partly in the other solvents.They react with a variety of electrophiles with either retention or inversion (Me3SnCl) of configuration.Carbanions 19 rearrange on warming to -20 deg C to hydroxy ketone 24 with racemisation. - Keywords: Esters, 1-phenylethyl; Carbanions, α-methyl-α-oxybenzyl, configurational stability; Ester-hydroxy ketone rearrangement