Nucleophilic β-alkenylation of N-alkoxyenamines: An umpolung strategy for the preparation of β,γ-unsaturated ketones
An umpolung strategy has been developed for the synthesis of β,γ-unsaturated ketones utilizing nucleophilic β-alkenylation of N-alkoxyenamines, which are prepared in situ from ketones and isoxazolidine, with alkenyl aluminum reagents. Various β,γ-unsatura
Nucleophilic α-arylation and α-alkylation of ketones by polarity inversion of N-alkoxyenamines: Entry to the umpolung reaction at the α-carbon position of carbonyl compounds
A new aspect of enamine chemistry: The formation of N-alkoxyenamines from ketones has led to an efficient umpolung reaction. The alkylation of N-alkoxyenamines with trialkylaluminum compounds proceeded smoothly and gave α-alkylated ketones (see scheme). This reaction offers a simple transformation of ketones into α-substituted ketones without the need to isolate enamines and intermediary imines.
Enamine Chemistry. Part 27. The Effect of Additional α- and β-Heteroatoms on the p?-Conjugation and Reactivity of Enamines. Sub- or Super-Enamines?
Enamines derived from isoxazolidine and 1,3-dioxa-5-azacyclohexane have been prepared.The effect of the addition a α- or β-heteroatoms is to decrease the p?-conjugation between the nitrogen lone pair of electrons and the ?-electrons of the double bond, as reflected in the spectral properties of the enamines and their reactivity with electrophiles.The reasons for this are discussed.
Ahmed, Md. Giasuddin,Ahmed, S. Asghari,Hickmott, Peter W.
p. 2383 - 2386
(2007/10/02)
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