5674-03-3Relevant articles and documents
Allylbarium reagents: Unprecedented regio- and stereoselective allylation reactions of carbonyl compounds
Yanagisawa, Akira,Habaue, Shigeki,Yasue, Katsutaka,Yamamoto, Hisashi
, p. 6130 - 6141 (2007/10/02)
The first direct preparation of allylbarium reagents by reaction of in situ generated reactive barium with various allylic chlorides and their new and unexpected selective allylation reactions with carbonyl compounds are disclosed. Highly reactive barium was readily prepared by the reduction of barium iodide with 2 equiv of lithium biphenylide in dry THF at room temperature. A variety of carbonyl compounds reacted with barium reagents generated from (E)- or (Z)-allylic chlorides in THF at -78 °C. All reactions resulted in high yields with remarkable α-selectivities not only with aldehydes but also with ketones. The double bond geometry of the starting allylic chloride was completely retained in each case. Stereochemically homogeneous (E)- and (Z)-β,γ-unsaturated carboxylic acids were easily prepared in good yields by highly α-selective carboxylation of allylic barium reagents with carbon dioxide. A selective Michael addition reaction with α,β-unsaturated cycloalkanone was also achieved using an allylbarium reagent. Treatment of 2-cyclopentenone (1 equiv) with allylbarium chloride (2 equiv) in THF at -78 °C for 20 min afforded 3-allylcyclopentanone in 94% yield with a 1,4/1,2 ratio of >99/1. Furthermore, the in situ generated barium enolate was efficiently trapped with various kinds of electrophiles (Me2C=CHCH2Br, nC5H11CHO, and CH3COCl).
TRANSPOSITION OXY-COPE ASSISTEE PAR LE TRIFLUOROACETATE MERCURIQUE EN QUANTITE STOECHIOMETRIQUE ET EN QUANTITE CATALYTIQUE
Bluthe, Norbert,Malacria, Max,Gore, Jacques
, p. 3277 - 3284 (2007/10/02)
Tertiary 1,5-hexadien-3-ols are transformed at room temperature into δ-ethylenic ketones in 35-90percent yields under two sets of conditions: treatment with one molar equivalent of mercuric trifluoroacetate followed by demercuration of the intermediate α-mercuro ketone with sodium borohydride; and treatment with 0.2 molar equivalent of the same salt in the presence of one molar equivalent of lithium trifluoroacetate or trifluoromethansulfonate.The reactions are highly stereoselective, the E isomer of the ketone forming 80-95percent of the product.The highest selectivity was observed under the second conditions.
