Regioselectivity of the Reactions of Heteroatom-Stabilized Allyl Anions with Electrophiles

Metallations and Reactions with Electrophiles of 4-Isopropyl-5,5-diphenyloxazolidin-2-one (DIOZ) with N-Allyl and N-Propargyl Substituents: Chiral Homoenolate Reagents

“…This information led to the configurational assignment of compounds 9a ± c by analogy. 13 ) When transmetallation was carried out at À 788 or the aldehyde was added at À 258, all four possible diastereoisomeric allenyl adducts were obtained with significantly reduced diastereoselectivity (ds % 75%).…”

“…3 contains a stereogenic center). The generation and reaction of −heteroatom-stabilized allyl anions× have been the subject of an extensive review article by Katritzky et al [13], and we refer the reader to publications by Hoppe et al [14] for diastereoselective reactions of heterosubstituted propargylic organometallic reagents. As we will show in the following sections, the N-allyl-, N-cinnamyl-, and Npropargyl-oxazolidinones 4 ) 2 ± 4 (Scheme 1) can be used for the synthesis of (Z)-enyloxazolidinones, allenyl-oxazolidinones, and enantiomerically pure homoaldol products 5 ).…”

Total Synthesis of Rapamycin

“…Recognising that the stereochemical configuration of the C26 alcohol is ultimately of no consequence, reaction of acetate derived aldehyde 87 with a gmethoxyallylzinc reagent [65] (derived from transmetallation of zinc onto the lithio anion of allyl methyl ether) [66] was explored. This transformation was high yielding but poorly selective, slightly favouring the undesired diastereomer (89).…”

A Study on the Reaction of Lithiated Allyl Systems with CO2, Isocyanates and Isothiocyanates

“…The acidified proton in Li-8 is most probably removed with the assistance of another molecule of lithiated Li-6 (Scheme 3). A [1,3] shift followed by reprotonation at the 3-position then yields lithiated Li-7. Support for this mechanism was found when n-butyl iodide was employed as a competing electrophile.…”

“…In addition to the 1:1 adduct, a small quantity of the 2:2 compound 25 was found. The formation of the latter can be explained by a Michael addition of lithiated amide Li-22 to the β-carbon atom of the allylic Scheme 5 backbone of already protonated amide 21, followed by a [1,3]-thioallyl rearrangement to give 25. A racemic pair of diastereomers was isolated, thus providing evidence for a diastereoselective reaction.…”