Lithium and magnesium enolates of cyclohexanone undergo palladium-catalyzed allylic alkylations under mild conditions. Diastereoselectivity and enantioselectivity are observed when the diphenyland dimethyl-substituted allylic substrates 1a and 1b are reacted with cyclohexanone or ethyl mesityl ketone. The lithium enolates of cyclohexanone, cyclopentanone and a-tetralone lead to the alkylations products 12-14 in an enantioselective manner. Axially chiral biphenyl-and binaphthyl-bisphosphanes provide high enantioselectivity and/or diastereoselectivity. In the case of the lithium enolates, the presence of lithium chloride is also crucial to reactivity and stereoselectivity. The stereochemical outcome of the allylic alkylation of cyclohexanone and acetophenone has been investigated by the palladium-catalyzed reaction of their lithium enolates with the cis/ trans isomeric alkenes (Z)-18 and (E)-19. It turns out that the preformed, non-stabilized enolates attack pallyl-palladium complexes generated in situ from the face opposite to the noble metal thus following the stereochemical pathway of soft, stabilized carbanions.
Tris(dibenzylideneacetone)‐dipaldium(0)‐chloroform adduct ( S) ‐(‐)‐5,5'‐Dichloro‐6,6'‐dimethoxy‐2,2’‐bis(diphenylphosphine)‐1,1'‐biphenyl Lithium chloride Allyl methyl carrbonate Diisopropylamine n‐ Butyllithium Cyclohexanone ( S) ‐(‐)‐2‐Allylcyclohexanone
N-Deprotonated five-, six-, seven, and nine-membered lactams undergo smooth palladium-catalyzed N-allylation with methyl-(pent-3-en-2-yl)-carbonate or 2-chloro-3-pentene. With axially chiral bisphosphane ligands, enantioselectivities ranging from 83 to 97% ee are reached. The configuration of one of the allylation products is assigned unambiguously by the preparation of a relay compound and by analogy to the others. Using the enantioselective allylation protocol as a key step, dvalerolactam is converted into (4S,9aR)-4-methylquinolizidine.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
customersupport@researchsolutions.com
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.