117760-41-5Relevant academic research and scientific papers
Felkin-Anh stereoselectivity in cycloadditions of acetylketene: Evidence for a concerted, pseudopericyclic pathway
Shumway,Ham,Moer,Whittlesey,Birney
, p. 7731 - 7739 (2007/10/03)
The cycloadditions of acetylketene with α-chiral aldehydes and ketones are shown to be diastereoselective, forming a tertiary or quaternary chiral center at an acetal or ketal carbon with good stereocontrol. X-ray crystallography of a minor product (5b) shows that the major products (e.g., 4b) are those predicted by the Felkin-Anh model. Transition states are reported at the MP2/6-31G* level for the addition of ethanal to formylketene and at the B3LYP/6-31G* level for the addition of 2-phenylpropanal. The ground-state conformations of the reactants and products are used to rationalize the relative energies and geometries of the transition states without the need to invoke the Cieplak hypothesis. However, chiral substituents on the α-oxoketene show no diastereoselectivity. These experimental and computational results are only consistent with the nearly planar, pseudopericyclic transition state previously proposed.
A new synthesis and application of 1-aryl-2,4-diones
Kel'in, Alexander V.,Kozyrkov, Yurii Yu.
, p. 729 - 734 (2007/10/03)
Methyl ketones or ethyl acetate react with aromatic α-bromo ketones in the presence of two equivalents of tert-butoxy or diethylaminomagnesium bromide in benzene (toluene) under reflux to produce 1-aryl-2,4-diones. The conversion, apparently, occurs via aldol condensation and subsequent [1,2]- sigmatropic rearrangement of the intermediate 3-bromo-2-hydroxy ketones. A number of fused aromatic and heteroaromatic phenols have been prepared by cyclodehydration of 1-aryl-2,4-diones.
Nucleophilic Additions to Ketenes by (Trimethylsilyl)lithium and by Enolates
Gong, Leyi,Leung-Toung, Regis,Tidwell, Thomas T.
, p. 3634 - 3639 (2007/10/02)
Reaction of t-Bu2C=C=O (5) with Me3SiLi at -78 deg C followed by trapping of the intermediate enolate with Ac2O gave t-Bu2C=C(OAc)SiMe3 (9).Other ketenes gave similar products.Reaction of ketenes PhCR=C=O (R = Me, 13; R = Et, 3) with enolates CH2=C(OLi)R1 (R1 = H, Me, t-Bu, Ph) at -78 deg C followed by warming to 25 deg C and hydrolysis gave vinyl esters PhCHRCO2C(R1)=CH2, along with 10 percent PhCHMeCOCH2COPh for R = Me, R1 = Ph.Under the same conditions the ketenes PhCR=C=O with enolates CH2=C(OK)R1 (R1 = Me, t-Bu, Ph) gave only 1,3-diketones PhCHRCOCH2COR1, but vinyl esters were the major products if the reactions were quenched at -78 deg C.It is proposed that enolates undergo preferential O-acylation by ketenes in a kinetically favored process, but that these intermediates can revert to thermodynamically more stable C-acylated products.
OXYGEN AND CARBON-ACYLATION OF ENOLATES BY KETENES
Bairgrie, Lynn M.,Leung-Toung, Regis,Tidwell, Thomas T.
, p. 1673 - 1676 (2007/10/02)
Ketenes react with lithium enolates mainly by O-acylation, thus providing a convenient route to vinyl esters and their enolates.
