Stereoselective Synthesis of (<i>E</i>)- or (<i>Z</i>)-α-Alkylidene-γ-butyrolactone from γ-Butyrolactone and Bis[ethoxy(thiocarbonyl)] Disulfide and Mechanistic Studies of the Effect of Metal Complexes on the Stereoselection
作者:Syuichi Matsui
DOI:10.1246/bcsj.60.1853
日期:1987.5
with an aldehyde to afford exclusively (E)-α-alkylidene-γ-butyrolactone. Interestingly, when the reaction was quenched below −20 °C or when it was carried out in the presence of metal complex such as zinc chloride, copper(I) iodide, or tributyltin chloride, (Z)-α-alkylidene-γ-butyrolactone was obtained as the major product. The stereoselectivity of this reaction was sensitive to the reaction temperature
New Methods for Stereoselective Synthesis of α-Alkylidene-γ-butyrolactones Using Monoanion of<i>O</i>-Ethyl<i>S</i>-(Tetrahydro-2-oxo-3-furanyl) Thiocarbonate and Dianion of α-Mercapto-γ-butyrolactone
The lithium enolates of O-ethyl S-(tetrahydro-2-oxo-3-furanyl) dithiocarbonate and thiocarbonate were found to be efficient reagents for the stereoselective synthesis of α-alkylidene-γ-butyrolactones fromcarbonylcompounds. The dianion of α-mercapto-γ-butyrolactone was successfully generated by treatment of α-mercapto-γ-butyrolactone with 2.2 equivalents of lithium diisopropylamide in the presence
The α-formylation of γ-and δ-lactones and the high yield conversion in to their respective α-methylene γ-and δ-lactones are described.
描述了δ-和δ-内酯的δ-甲酰化反应以及将其高产率转化为各自的δ-亚甲基δ-和δ-内酯的过程。
Temperature Effects on Stereocontrol in the Horner−Wadsworth−Emmons Condensation of α-Phosphono Lactones
作者:Jose S. Yu、David F. Wiemer
DOI:10.1021/jo070722+
日期:2007.8.1
The Horner−Wadsworth−Emmons condensation of some α-phosphono lactones has been examined for conditions that impact product stereochemistry. The temperature employed to quench the reaction was found to be a major factor. For example, after the diethyl phosphonate derivative of γ-butyrolactone was treated with potassium hexamethyldisilazane, 18-crown-6, and propionaldehyde at −78 °C in THF, an aliquot
Cyclic alpha,beta-unsaturated ketones, alkylidene lactones, and alkenyl ethers have been hydrogenated in high enantiomeric excesses by use of BINAP-Ru(II) complexes (BINAP = 2,2'-bis(diphenylphosphino)-1,1'-binaphthyl) as catalysts. 2-Alkylidenecyclopentanones were hydrogenated in the presence of [RuCl(BINAP)(benzene)]Cl, Ru2Cl4(BINAP)2(NEt(3)), or Ru(OCO CH3 )(2)(BINAP) in up to 98% ee, while in the case of 2-benzylidene- and 2-(3-phenylpropylidene)cyclopentanones, enantiomeric excesses of the hydrogenation were below 50% under the same conditions. The sense of asymmetric induction as well as the enantioselectivity (95% ee) obtained in the hydrogenation of (E)-2-propylidene-gamma-butyrolactone were the same as those of the (Z)-isomer. Lactones, 2- and 4-alkylidene-gamma-butyrolactones, were converted to the corresponding saturated gamma-butyrolactones in 95% ee. Hydrogenation of diketene with the catalytic system derived from RuCl[(S)-BINAP](benzene)}Cl and triethylamine or complex Ru2Cl4[(S)-BINAP](2)(NEt(3)) established a new synthetic route to (R)-4-methyl-2-oxetanone, a promising monomer of biodegradable polymers, in up to 97% selectivity and 92% ee. Alkenyl ethers, 2-methylenetetrahydrofuran, and 2-methyl-3,4-dihydrofuran have also been hydrogenated to give 2-methyltetrahydrofuran in 91 and 87% ee, respectively.