Catalytic Enantioselective Direct Aldol Addition of Aryl Ketones to α-Fluorinated Ketones

The catalytic enantioselective synthesis of α-fluorinated chiral tertiary alcohols from (hetero)aryl methyl ketones is described. The use of a bifunctional iminophosphorane (BIMP) superbase was found to facilitate direct aldol addition by providing the strong Brønsted basicity required for rapid aryl enolate formation. The new synthetic protocol is easy to perform and tolerates a broad range of functionalities and heterocycles with high enantioselectivity (up to >99:1 e.r.). Multi-gram scalability has been demonstrated along with catalyst recovery and recycling. ¹H NMR studies identified a 1400-fold rate enhancement under BIMP catalysis, compared to the prior state-of-the-art catalytic system. The utility of the aldol products has been highlighted with the synthesis of various enantioenriched building blocks and heterocycles, including 1,3-aminoalcohol, 1,3-diol, oxetane, and isoxazoline derivatives.     

Regiospecific Synthesis of α-Alkylated Ketones

Several solutions have been developed to avoid the troublesome di- and polyalkylation encountered in ketone enolate alkylations¹, including use of the covalent Li enolate, or “additives” to tighten the metal-oxygen bond (M = Si^2,3,4, Sn^5,6, Al⁶, B^7,8,9).     

Synthesis of Vinyl and β-Phthalimido Ketones

Vinyl ketones are prepared by reaction of an aldehyde with a vinyl Grignard reagent followed by a Swern oxidation. β-Phthalimido ketones are then obtained by 1,4-addition of phthalimide.     

Homologation of α,β-Ethylenic Ketones in Substituted β,γ-Ethylenic Ketones Using Phosphoniosilylation

Among the methods described (1–4) to prepare β,γ-unsaturated ketones 2, Warren (4) recommends the Wittig-Horner procedure involving β-acetalated diphenylphosphinoxides reagents |scheme 1 (i)|.     

Origin of Ketones in Sediments of Qinghai Lake

This paper analysed the ketone fractions in sediments and living organisms of Qinghai Lake using GC-MS and discussed their origin,n-Alkan-2-ones detected in the sediments ranged from C_(12) to C_(33) with a maximum at n-C_(25) or n-C_(29) and showed a strong odd predominance, n-Alkan-2-ones in the living organisms analysed ranged from C_(15) to C_(31) with a maximum at n-C_(27).The authors believed that ketones in modern sediments may directly derive from biosynthesis.     

γ-Methylenation of α,β-Unsaturated Ketones

γ-Methylene derivatives of α,β-unsaturated ketones are obtained readily by a one-pot procedure exploiting the reaction of O-silylated dienolates with commercially available formaldehyde N, N-dimethyliminium chloride in anhydrous N, N-dimethylformamide, in situ oxidation of the Mannich reaction product with hydrogen peroxide, and elimination of N,N-dimethylhydroxylamine from the resultant N-oxide.     

New and Stereospecific Synthesis of α-Ethylenic Ketones

Abstract

H. Kise et al¹ have shown that the reaction of β-propiolactones 1 with ylides 2 give phosphonium carboxylate betaïne 3. We now report that, carried out under different conditions, reaction of lactones 1 with the same ylides proceeds through pathway (b). Thermolysis of 4 affords α-ethylenic ketones 5. The mecanism of this new extrusion reaction of triphenylphosphine oxyde probably involves the generation of an oxaphosphene as an intermediate.     

Synthesis of α‐Hydroxy Ketones from Terpene Aldehydes

Abstract

Unsymmetrically substituted α‐hydroxy ketones possessing isoprenoid units within the molecule were synthesised from commercially available terpene aldehydes. The synthesis was applicable to α,β‐unsaturated aldehydes and afforded the respective α‐hydroxy‐methyl ketones in overall good yield. Tautomerisation of these products did not occur under the conditions of reaction but was observed upon heating. Diastereoisomeric α‐hydroxy ketones have been resolved, and X‐ray analysis on one of these analogues allowed for the elucidation of the stereochemistry after conversion into its camphanate ester.     

Syntheses of β－Hydroxy Ketones by Organosamarium

An organosamarium reagent was prepared via the reaction of a-bromoacetophenone with samarium. This organosamarium reagent reacted with aldehydes to give β-hydroxy ketones. A possible reaction process was suggested.     

A Convenient Method of Synthesis of Ferrocenylethynyl Ketones

It is well known that molecules possessing extensive conjugated π-electron systems exhibit large non-linear optical properties,[1,2] but the compounds of ferrocenylethynyl ketones have not been reported so far. We now reported preparation of some ferrocenylethyl ketones. These new ethynylketones containing ferrocenyl were prepared conveniently via coupling reaction catalyzed by PdCl2(PPh3)2/PdBzCl(PPh3)2-CuI from ferrocenylethyne and acyl chlorides. This coupling reaction proceeded smoothly in argon and free-water atmosphere at room temperature and gave coupling products in satisfactory yields. All products were characterized by 1H NMR, MS, IR and UV spectra.     

Synthesis of New Thiazoles from α-Halohetaryl Ketones

Reactions of -bromoacetylphenoxathiin, -bromoacetylphenoxathiin 10,10-dioxide, or -bromoacetylthianthrene with certain p-(arylsulfonyl)thiobenzamides lead to the formation of the corresponding 2,4-disubstituted thiazoles. The new compounds were characterized through elemental analysis and spectral data (IR, ¹H NMR, and ¹³C NMR).     

Reduction of Aromatic α-Halo Ketones with Metallic Bismuth

Aromatic α-bromo ketones and α-iodio ketones can be reduced by bismuth prepared from NaBH₄ and BiCl₃ in water to their parent ketones in high yields, but aromatic α-chloro ketones should be added to sodium iodide first.     

Syntheses of New Carbonyl Derivatives from α-Halohetaryl Ketones

The Kröhnke reaction of 2-bromoacetylphenoxathiin and 2--bromophenoxathiin 10,10-dioxide, through N-ylide and S-ylide intermediates, leading to the corresponding glyoxals, was described. The condensation reaction of 2--bromoacetylphenoxathiin with aromatic o-hydroxy aldehydes and further cyclization to new furan derivatives was also performed. The new compounds were characterized through elemental analysis and spectral data (IR, ¹H NMR and ¹³C NMR).     

Transition-Metal-Free Superbase-Promoted Stereoselective α-Vinylation of Ketones with Arylacetylenes: A General Strategy for Synthesis of β,γ-Unsaturated Ketones

A wide variety of β,γ-unsaturated ketones of E configuration have been obtained in good to excellent yields via KO(t)Bu/DMSO promoted α-vinylation of aliphatic, cycloaliphatic, and alkyl aromatic (heteroaromatic) ketones with diverse arylacetylenes.     

Synthesis of α,β-Unsaturated Ketones via Enamines

Acylation of an enamine followed by acid hydrolysis constitutes the well-known Stork's reaction of synthesizing β-diketones.^1,2 This article reports that the acylated enamine 1 which corresponds to monoenamine of a β-diketone can be hydrogenated to a Mannich base 2 which on elimination by heating or treatment with acid yields the α, β-unsaturated ketone 3; further hydrogenation gives saturated ketone 4 in good yield (Scheme 1). A similar transformation effected by hydroboration has been reported by Montury and Góre.     

Enantioselective Alkynylation of Ketones Promoted by β-Sulfonamide Alcohol-Titanium Complexes

A readily available β-sulfonamide alcohol-titanium complex was found to be effective on promoting the asymmetric addition reaction of an alkynylzinc reagent to unactivated simple ketones under very mild conditions. And the corresponding chiral tertiary propargylic alcohols were obtained with enantiomeric excesses of up to 86%, which provided a simple, practical and inexpensive method to generate chiral tertiary propargylic alcohols.     

The Cyclopropanation of Unsaturated Ketones in “Super-Basic” Media

A modified cyclopropanation of unsaturated ketones using dimethyloxosulfonium methide in “super basic” media generates exclusively the trans products in high yields (86–95%).     

氨基磺酸做催化剂催化多组分反应合成β-Acetamido Ketones

氨基磺酸作为一种可回收、绿色催化剂在室温下能高效地催化合成β-乙酰氨基酮.反应产物通过红外、~1HNMR和~(13)CNMR表征,其结果证明为合成的目标分子. 特别值得强调的是二元官能团的β-乙酰氨基酮也可通过乙酰氯、苯乙酮、间苯二甲醛和腈类化合物交联得到. 而且二元官能团的β-乙酰氨基酮的催化合成很少见报导. 在氨基磺酸催化的酮、芳醛、乙酰氯和乙腈参与的多组分反应体系中,反应有条件温和、产率较高、催化剂用量少、催化剂可以回收再利用等优势.     

Reduction of Aldehydes and Ketones with Potassium Borohydride as Reductant

A series of aldehydes and ketones were reduced by potassium borohydride in an ionic liquid/water ([bmim]PF6/H2O) biphasic system to afford corresponding alcohol with high purity in excellent yields. The ionic liquid/water biphasic system could promote the chemoselectivity and the substituents such as nitro group and chlorine remained intact. Aromatic ketones were not as active as aromatic aldhydes and cyclic ketones owing to their higher steric hindrance. The ionic liquid could be recycled and reused. This protocol has notable advantages of no need of phase transfer catalyst and organic solvents, mild conditions, simple operation, short reaction time, ease work-up, high yields and recycling of the ionic liquid.     

New Synthetic Route to Ketones from Camphene and β-Pinene

Camphene or -pinene was treated with Cp₂Zr(H)Cl (Cp = h⁵-C₅H₅) in THF to give organozirconium (IV) complexes, which were trapped with acetyl chloride or benzoyl chloride in the presence of CuI to afford ketones in yields of 63% to 74%.