71911-66-5Relevant academic research and scientific papers
Substrate range of the titanium TADDOLate catalyzed asymmetric fluorination of activated carbonyl compounds
Bertogg, Andreas,Hintermann, Lukas,Huber, Dominique P.,Perseghini, Mauro,Sanna, Maria,Togni, Antonio
experimental part, p. 353 - 403 (2012/05/07)
The substrate range of the [TiCl2(TADDOLate)] (TADDOL=α,α,α′,α′-tetraaryl-1,3-dioxolane-4, 5-dimethanol)-catalyzed asymmetric α-fluorination of activated β-carbonyl compounds has been investigated. Optimal conditions for catalysis are characterized by using 5 mol-% of TiCl2(naphthalen-1- yl)-TADDOLate) as catalyst in a saturated (0.14 mol/l) MeCN solution of F-TEDA (1-(chloromethyl)-4-fluoro-1,4-diazoniabicyclo[2.2.2]octane bis- [tetrafluoroborate]) at room temperature. A series of α-methylated β-keto esters (3-oxobutanoates, 3-oxopentanoates) with bulky benzyl ester groups (60-90% ee) or phenyl ester (67-88% ee) have been fluorinated readily, whereas α-acyl lactones were also readily fluorinated, but gave lower inductions (13-46% ee). Double stereochemical differentiation in β-keto esters with chiral ester groups raised the stereoselectivity to a diastereomeric ratio (dr) of up to 96.5:3.5. For the first time, β-keto S-thioesters were asymmetrically fluorinated (62-91.5% ee) and chlorinated (83% ee). Lower inductions were observed in fluorinations of 1,3-diketones (up to 40% ee) and β-keto amides (up to 59% ee). General strategies for preparing activated β-carbonyl compounds as important model substrates for asymmetric catalytic α-functionalizations are presented (>60 examples). Copyright
Stereoselective reduction of 2-methyl-3-oxo esters (or amides) with sodium borohydride catalyzed by manganese (II) chloride or tetrabutylammonium borohydride. A practical preparation of erythro and threo-3-hydroxy-2-methyl esters (or amides)
Taniguchi, Masahiko,Fujii, Hideaki,Oshima, Koichiro,Utimoto, Kiitiro
, p. 11169 - 11182 (2007/10/02)
erythro-3-Hydroxy-2-methylpropionates or erythro-3-hydroxy-2-methylpropionamides were prepared with high stereoselectivity by NaBH4 reduction of the corresponding 2-methyl-3-oxo esters or 2-methyl-3-oxo amides in the presence of a catalytic amount of manganese(II) chloride. On the other hand, reduction of these substrates with n-Bu4NBH4 provided threo-isomers selectively. erythro-Selective reduction of 2-methyl-3-oxo amides with NaBH3CN in 1N HCl-MeOH is also described.
Malonate Anion Induced Favorskii-Type Rearrangement. Reaction of Cyclic α-Halo Ketones with Sodiomalonates
Sakai, Takashi,Amano, Eiichiro,Kawabata, Akifumi,Takeda, Akira
, p. 43 - 47 (2007/10/02)
The reaction of 2-chlorocyclohexanone (1b) with ethyl sodiomalonate in benzene at 0-25 deg C gave 6-bicyclohexan-6-ol (4c), the Favorskii-type intermediate, in 49percent yield, in place of the substitution product ethyl C-(2-oxocyclohexyl)malonate (3).Derivatives of bicycloheptan-7-ol (4a,b) and those of bicyclohexan-6-ol (4d,e) were also obtained in good yields by similar means.Compound 4c was transformed into 3 readily by heating with 0.05 equiv of NaH in benzene.The hydrolysis of 4a-d with 0.2 N NaOH followed by pyrolysis at 110-120 deg C gave the ring-contracted β-keto esters 9a-d.Pyrolysis after the hydrolysis with 2N NaOH gave the corresponding ketones 11a-d in good yields.Oxidation of 4c with CrO3 and HClO4 afforded ethyl C-(2-hydroxycyclopentanecarbonyl)malonate (14) in 45 percent yield.Treatment of 4c with Br2 gave ethyl C-(1-bromocyclopentanecarbonyl)malonate (18) in 64 percent yield.
