Lithiated ambident anions derivedfrom (1-alkyl-2-propenyl)- or (1-phenyl-2-propenyl)-pentamethyl phosphoric triamides undergo regioselectively γ-reaction with various alkylating reagents and isobutyraldehyde. Further hydrolysis of adducts releases the ketone under acid conditions. Number of synthetic applications clearly show the ketone homoenolate behaviour of these new carbanions.
Control of chemo- and stereoselectivity in the reactions of organocuprates with .alpha.-oxoketene dithioacetals
作者:R. Karl Dieter、Louis A. Silks、Jeffrey A. Fishpaugh、M. E. Kastner
DOI:10.1021/ja00302a014
日期:1985.8
Les α-oxocetene dithioacetals subissent une substitution selective par les reactifs organo-Cu-Li pour conduire a des β-alkylthio α-β-enones. On examine les effets de la structure, du coordinat de Cu transferable, du reactif Cu et du solvant sur la chimio- et la stereoselectivite de la reaction
Les α-oxocetene dithioacetals 存在未取代选择性的反应性有机-Cu-Li 倾倒导致 des β-烷硫基 α-β-烯酮。在检查les effets de la structure, du coordinat de Cu transferable, du reactif Cu et du solvant sur la chimio- et la立体选择性德拉反应
Polarized Ketene Dithioacetals; 53:<sup>1</sup>A Facile Synthesis of 2-Aryl-6-methylthio-4<i>H</i>-pyran-4-ones and a Novel Cycloaromatization Reaction
作者:L. W. Singh、H. Ila、H. Junjappa
DOI:10.1055/s-1987-28107
日期:——
A facile route to hitherto unreported 2-aryl-6-methylthio-4H-pyran-4-ones 4a-f has been developed by base-catalyzed condensation of acylketene dithioacetal 2 with substituted methyl benzoates 1a-f followed by subsequent ring closure of resulting α-aroylacylketene dithioacetals 3a-f. Acylketene dithioacetal 2 and the corresponding β-methylthioenone 9 are shown to undergo self-condensation and aromatization in the presence of sodium hydride and methylbenzoate in refluxing xylene to give 2, 6-bis(methylthio)-4-hydroxy-acetophenone (6) and 4-hydroxyacetophenone (10) respectively in good yields. A mechanistic pathway for the formation of 6 and 10 via 3 has been described.
Theα-oxoketene dithioacetals are shown to undergo conjugate 1,4-reduction in highly regio- and chemoselective manner with sodium borohydride in acetic acid to afford the corresponding β-oxodithioacetals in good yields. These results have been rationalized according to HSAB principle in terms of 'hard soft affinity inversion' concept. The reduction of with sodium cyanoborohydride also proceeds in 1