Asymmetric reduction of perfluoroalkyl ketones with chiral lithium alkoxides

Reduction of perfluoroalkyl ketones with chiral lithium alkoxides gave chiral α-perfluoroalkyl alcohols in high enantiomeric excesses. Interestingly, reaction of 2,2,2-trifluoroacetophenone (1) with lithium (S)-1-phenylethoxide (2) gave (S)-2,2,2-trifluoro-1-phenylethanol (3), while the same reaction of perfluorooctan-1-one (7) with 2 gave (R)-1H-1-phenylperfluorooctanol (8). Based on the speculation of mechanism, the order of steric effects on this reaction is estimated as C₇F₁₅ > substituted phenyl > CF₃.     

Anti-selective and regioselective aldol addition of ketones with aldehydes using MgI2 as promoter

The first example of a direct aldehyde-ketone coupling using the secondary amine piperidine as base in the presence of MgI₂ to generate high selectivity of anti-aldol products from unmodified ethyl ketones in high yield is reported. The coupling reactions were carried out in a one-pot reaction by mixing four reaction components at room temperature. In the case of unsymmetrical ketones, addition was made to the less hindered α-side.     

Synthesis and crystal structure of polyaryl substituted diene derivatives based on the reduction of diphenylacetylene with lithium naphthalenide

The reduction of diphenylacetylene with lithium naphthalenide produced two kinds of intermediates,1 or 2,depending on the ratio of diphenylacetylene to lithium naphthalenide.A series of polyaryl substituted ethylene/diene derivatives were synthesized by reaction of electrophⅡes with the corresponding intermediates produced in situ.All new compounds were fully characterized,and their single crystal structures were determined.     

4-取代-脯氨醇催化的前手性酮不对称硼烷还原

(2S)-(二苯基羟甲基)-(4S)-苯氧基-四氢吡咯(10)由羟脯氨酸(6)经4步反应制得。用10催化6种前手性酮的不对称硼烷还原反应,其结果与(S)-二苯基脯氨醇催化的同一反应的结果进行了对比。     

Stereoselective synthesis of trifluoromethyl-substituted 1,2-diamines by aza-Michael reaction with trans-3,3,3-trifluoro-1-nitropropene

Aza-Michael addition of optically pure 4-phenyl-2-oxazolidinone to 3,3,3-trifluoro-1-nitropropene proceeds smoothly at low temperature with a high yield. Diastereoselectivity of the addition depends on the base used and lithiated species proved to be highly efficient affording 92% de. Optically pure 1,2-diamino-3,3,3-trifluoropropane is prepared in 58% yield from the aza-Michael addition product through a three-step procedure.     

Direct palladium-catalyzed allylic alkylations of alcohols with enamines: Synthesis of homoallyl ketones

An efficient, direct nucleophilic allylic substitution of α-, β- and γ-substituted alcohols with enamines, using the Pd(OAc)_2/PPh₃ catalyst system and ZnBr₂ as a promoter in CH₂Cl₂ at reflux, is reported. The reaction course was dependent on the steric hindrance at the α- or γ-positions with respect to the functionalized α-carbon, selectively affording in moderate to good yields, α- or γ-homoallyl ketones, the so-called “linear” and “branched” products, respectively.     

Enantioselective metal-free reduction of ketones by a user-friendly silane with a reusable chiral additive

1-Hydrosilatrane, a safe and easy-to-handle reducing reagent that can be inexpensively accessed, has been shown to reduce prochiral ketones asymmetrically in the presence of chiral 1,2-aminoalcohols with ees ranging from 8% to 86%. The best result was achieved using ephedrine as the source of chirality, which is readily commercially available. The additive can be recovered through extraction and reused without any erosion of enantioselectivity.     

CuI-catalyzed tandem carbomagnesiation/carbonyl addition of Grignard reagents with acetylenic ketones: Convenient access to tetrasubstituted allylic alcohols

Highly functionalized tetrasubstituted allylic alcohols were prepared conveniently by CuI-catalyzed tandem carbomagnesiation/carbonyl addition of Grignard reagents with acetylenic ketones. The obtained allylic alcohols can be further transformed to polysubstituted indenes by intramolecular cyclization.     

On the Reaction between Alkyl Isocyanides and Ethynyl Phenyl Ketone in the Presence of N,N′-Dimethylbarbituric Acid

Summary.  The reactive 1:1 intermediate produced in the reaction between alkyl isocyanides and ethynyl phenyl ketone was trapped with N,N ′-dimethylbarbituric acid to produce alkyl 1,3-dimethyl-2,4-dioxo-7-phenyl-1,3,4,5-tetrahydro-2H-pyrano[2,3-d]pyrimidine-5-carboxamides in good yields. Corresponding author. E-mail: isayavar@yahoo.com Received January 8, 2002. Accepted January 14, 2002     

新型结构聚芳亚胺的合成与热性能分析

通过傅-克酰化反应得到1,4-双（4′-溴苯酰基）苯,以1,4-双（4′-溴苯酰基）苯和α,α′-双（4′-氨基苯基）-1,4-二异丙基苯为单体,通过钯催化的胺基化反应缩聚合成了含异丙基的聚亚胺酮（pr-PIK）.再以pr-PIK和苯基锂为底物,通过亲核加成反应得到新型结构聚合物——含异丙基的聚醇胺（pr-PAI）.聚合物结构通过FT-IR、1H NMR和元素分析表征,表征结果与目标产物吻合良好.pr-PIK和pr-PAI的热性能由DSC和TG测定,结果表明pr-PIK和pr-PAI具有良好的热稳定性,玻璃化温度大于150℃,热分解温度大于480℃.     

Experimental and theoretical studies on the transannular cyclizations of 3,7-dimethylenebicyclo[3.3.1]nonane with polyfluoroalkyl radicals

Radical cyclizations of 3,7-dimethylenebicyclo[3.3.1]nonane with CF₃I, n-C₃F₇I, ICF₂COOEt and ICF₂PO(OEt)₂ selectively led to corresponding 3,7-noradamantanes, which were used for preparation of various polyfluoroalkyl substituted noradamantyl amines and carboxylates. DFT computations revealed that chemoselectivity of the radical cyclizations is realized due to the high electrophilicity of the CF₃ radical, as well as due to efficient trapping of intermediate noradamantylmethyl radicals by perfluoroiodoalkane.     

Selective reaction of camphor-derived exo-formyl [2.2.1]bicyclic carbinol with alkyl primary amines: application to the preparation of new chiral catalysts for asymmetric reduction of aryl ketones

Reaction of camphor-derived exo-formyl [2.2.1]bicyclic carbinol with various alkyl primary amines gave regio- and stereo-specific [3.2.1]bicyclic α-amino ketones. A detailed mechanism of the reaction was discussed. This reaction was further applied to the preparation of some camphor-derived oxazaborolidines, one of which proved to be an efficient chiral catalyst for the asymmetric borane reduction of prochiral aryl ketones at room temperature.     

Metalation of 1-R-2-benzyl-o-carboranes with lithium aluminum hydride

Carboranes with the general formula I-R-2-PhCH₂-1,2-C₂B₁₀H₁₀ (R = Me, Prⁱ, Ph, PhCH₂) are readily metalated with lithium aluminum hydride in a THF solution at the CH₂ group. In this case only one hydrogen atom in LiAlH₄ is substituted, and trihydride complexes 1-R-2-PhCH(AlH₃Li)-1,2-C₂B₁₀H₁₀, are formed, which are stable in a solutionTranslated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 1282–1284, May, 1996.     

ZnCl2-catalyzed hydrodefluorination of gem-difluoromethylene derivatives with lithium aluminum hydride

Hydrodefluorination of gem-difluoromethylene derivatives with lithium aluminum hydride in the presence of a catalytic amount of ZnCl₂ in good to high yields was described. A possible mechanism is also suggested.     

Effect of aniline derivatives on the extraction of cobalt with 1-phenyl-3-methyl-4-benzoylpyrazol-5-one in toluene

Summary The effect of aniline derivatives [4-methylaniline=4-toluidine, 3,4-dimethylaniline=3,4-xylidine, N,N-dimethylaniline and tribenzylamine (Am)] on the extraction of cobalt from sulphate, nitrate and perchlorate aqueous media of 1.0M ionic strength with 1-phenyl-3-methyl-4-benzoylpyrazol-5-one (HL) in toluene, has been quantitatively studied. With both primary amines a synergic effect was found owing to theAmH·CoL ₃ ion pair extraction. TheAmH·CoL ₃ average formation constant, from CoL ₂ andAmH·CoL, was logK _s =3.7 and 3.8 forAm=4-toluidine and 3,4-xylidine respectively. With N,N-dimethylaniline and tribenzylamine which are poorly protonated in the cobalt extractionpH range (4–6), no noticeable synergism was observed.On leave from: Department of Inorganic Chemistry, Chemical Faculty, Ignacy Lukasiewicz Technical University, PL-35-959 Rzeszow, Poland     

Reaction of lithium eneselenolates derived from selenoamides with ketones: a highly diastereoselective synthetic route to β,β-disubstituted β-hydroxy selenoamides

The reaction of lithium eneselenolates generated from selenoamides with a variety of ketones proceeded smoothly at −78°C to give the corresponding β,β-disubstituted β-hydroxy selenoamides in moderate to good yields. The reaction showed high diastereoselectivity. The products obtained were converted to the corresponding amides by reacting them with cyclohexene oxide.     

Synthesis,spectroscopic characterization,X-ray structure and DFT calculations of rhenium(III) complex with 1-isoquinolinyl phenyl ketone

The [ReCl₃(MeCN)(PPh₃)] complex reacts with 1-isoquinolinyl phenyl ketone (N–O) to give [ReCl₃(N–O)(PPh₃)]. The compound has been studied by IR, UV–Vis spectroscopy, magnetic measurements and X-ray crystallography. The magnetic behavior is characteristic of mononuclear octahedral Re(III) complex with d⁴ low-spin (³T_1g ground state) and arises because of the large spin–orbit coupling, which gives diamagnetic ground state. The molecular orbital diagram of [ReCl₃(N–O)(PPh₃)] has been calculated with the density functional theory (DFT) method, and time-dependent DFT (TD-DFT) calculations have been employed in order to discussion of its spectroscopic properties in more detail.     

Non-catalytic conversion of C-F bonds of gem-difluoromethylene derivatives to C-H bonds with lithium aluminum hydride under room temperature

An unexpected hydrodefluorination of unactivated aliphatic C-F bonds of CF₂ derivatives with LiAlH₄ at room temperature without any added metal catalyst was reported. Deuterium-labeling experiments suggested that the hydrogens introduced into the products originated from LiAlH₄.     

Synthesis of Novel α-Trifluorothioanisole Derivatives Containing Phenylpyridine Moieties with Herbicidal Activity

To discover novel herbicidal compounds with favorable activity, a range of phenylpyridine-moiety-containing α-trifluorothioanisole derivatives were designed, synthesized, and identified via NMR and HRMS. Preliminary screening of greenhouse-based herbicidal activity revealed that compound 5a exhibited >85% inhibitory activity against broadleaf weeds Amaranthus retroflexus, Abutilon theophrasti, and Eclipta prostrate at 37.5 g a.i./hm², which was slightly superior to that of fomesafen. The current study suggests that compound 5a could be further optimized as an herbicide candidate to control various broadleaf weeds.