Regio- and Stereocontrol in the Reactions of α-Halo-β,γ-enoates and α-O-Phosphono-β,γ-enenitriles with Organocuprates

Autor:	Alfredo Picado, R. Karl Dieter
Rok vydání:	2014
Předmět:	chemistry.chemical_classification Substitution reaction Allylic rearrangement chemistry Stereochemistry Ligand Reagent Organic Chemistry Stereoselectivity Counterion Chemical reaction Cis–trans isomerism
Zdroj:	The Journal of Organic Chemistry. 79:11125-11138
ISSN:	1520-6904 0022-3263
DOI:	10.1021/jo502111c
Popis:	The reactions of (Z)- and (E)-ethyl 2-chloro-3-octenoate (4a and 17) and (E)- and (Z)-diethyl (1-cyano-2-heptenyl)phosphate (21a and 21b) with organocuprates were investigated as potential substrates for preparing γ-substituted α,β-enoates and enenitriles. In these copper-mediated allylic substitution reactions, the Z-isomer 4a displayed complete regio- and stereoselectivity (i.e., E:Z), while the regio- and stereoselectivity for E-isomer 17 varied as a function of solvent, cuprate reagent, transferable ligand, and cuprate counterion (e.g., Li(+) vs MgX(+)). Excellent selectivities could be achieved with 17 and (n)BuCuCNLi in Et2O. Conditions for improved selectivities in the reactions of allylic cyanophosphates over those previously reported were found. A series of relative rate and competition experiments was performed, and the degree of regio- and stereoselectivity for each system was rationalized in the light of the current mechanistic understanding of cuprate-mediated allylic substitution reactions.
Databáze:	OpenAIRE
Externí odkaz:	https://explore.openaire.eu/search/publication?articleId=doi_dedup___::a7cbbb8de26661de3b79e0ea2d90fcbe https://doi.org/10.1021/jo502111c Zobrazit plný text záznamu