92186-72-6Relevant academic research and scientific papers
Mixed crossed aldol condensation between conjugated esters and aldehydes using aluminum tris(2,6-diphenylphenoxide)
Saito, Susumu,Shiozawa, Masahito,Yamamoto, Hisashi
, p. 1769 - 1771 (2007/10/03)
The combined use of aluminum tris(2,6-diphenylphenoxide) (ATPH) and lithium 2,2,6,6-tetramethylpiperidide (LTMP) has proven to be effective for the mixed crossed aldol condensation between conjugated esters and various aldehydes. An example is shown in Eq
Anion-Catalyzed Reactions of Silyl Ester Polyenolates with Electrophiles
Hertler, Walter R.,Reddy, Gade S.,Sogah, Dotsevi Y.
, p. 3532 - 3539 (2007/10/02)
The stereochemical assignments for the trimethylsilyl ester polyenolates 1, 2, and 3 have been made.Unlike simple silyl ketene acetals, 1, 2, and 3 are obtained predominantly as the thermodynamic Z isomers.Bifluoride-catalyzed equilibration studies showed the equilibrium compositions of 1, 2, and 3 to be 89percent Z, 67percent Z, and 95percent 1-Z,3-E, respectively.The regiochemistry of the bifluoride-catalyzed Reformatsky-type reaction of benzaldehyde with 1, 2, and 4 was determined.Regiochemical control of the condensation of 1 with benzaldehyde by reaction temperature was demonstrated, with 95percent α reaction at -95 deg C and 99percent γ-reaction at +34 deg C.Mechanism studies are consistent with a dissociative process in which a dienolate reacts with benzaldehyde at the α position to give the kinetic-controlled product, and as the reaction temperature increases, increasing amounts of the thermodynamic γ product are formed.A nondissociative cyclic process leading to α product may occur at low temperatures.The naked ester dienolate prepared by reaction of 1 with TASF and removal of the resulting fluorotrimethylsilane was alkylated by benzyl bromide exclusively at the α position at -100 deg C.The bifluoride-catalyzed reverse reaction of 1 with benzaldehyde is much slower than the processes that determine the regiochemistry in the forward reaction.
Condensation of Crotonic and Tiglic Acid Dianions with Aldehydes and Ketones
Johnson, Paul R.,White, James D.
, p. 4424 - 4429 (2007/10/02)
The lithium dianions of crotonic and tiglic acids reacted with n-heptanal, benzaldehyde, isobutyraldehyde, 2,2-dimethyl-3,3-dimethoxypropionaldehyde, acetone, and cyclopentanone at -78 deg C, room temperature, and 65 deg C to give α- and γ-condensation products.The kinetically controlled pathway gives largely or entirely the β-hydroxy acid from condensation at the α-carbon, but at higher temperature the reaction is reversible leading to the more stable δ-hydroxy α,β-unsaturated acid.In addition to the reaction temperature, steric effects associated with both the carbonyl electrophile and the acid dianion were found to influence the α:γ ratio of condensation products.
