Oxidation of the α-ketol and enone derivatives of cyclohexanone by tetrazolium salts

A new red-ox reaction, leading to the respective keto derivatives from α-ketol and enone derivatives of cyclohexanone, is reported.     

Synthesis of fluorinated α-amino ketones part I: α-benzamidoalkyl mono- di- and trifluoromethyl ketones

2-Phenyl-5(4H)-oxazolones, obtained from α-amino acids, are reacted with di- and trifluoro acetic anhydride by a modified Dakin-West procedure to yield in a one-pot reaction α-benzamidoalkyl-di- and trifluoromethyl ketones in good yields. The monofluoromethyl analogues were also prepared from α-amino acids, however the use of the highly toxic fluoroacetic anhydride was avoided. The key step is the halogen exchange reaction on the corresponding bromomethyl ketone.     

Enantioselective α-arylation of aldehydes via the productive merger of iodonium salts and organocatalysis

The enantioselective α-arylation of aldehydes has been accomplished using diaryliodonium salts and a combination of copper and organic catalysts. These mild catalytic conditions provide a new strategy for the enantioselective construction and retention of enolizable α-formyl benzylic stereocenters, a valuable synthon for the production of medicinal agents. As one example, this new asymmetric protocol has been applied to the rapid synthesis of (S)-ketoprofen, a commercially successful oral and topical analgesic.     

Reaction of α-hydroxyiminoacetonitrile oxides with potassium thiocyanate

Potassium thiocyanate reacts with substituted -hydroxyiminoacetonitrile oxides in acetic acid to give, unexpectedly, 5-(carbamoyl)imino-²-1,4,2-oxathiazo-lines. The structure of 3-(1-adamantyl)-5-(carbamoyl)imino-²-1,4,2-oxathiazo-line has been confirmed by x-ray diffraction.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 4, pp. 885–889, April, 1991.     

Reduction and N-Alkylation of α-Methylene-indolines with Sodium Cyanoborohydride in Carboxylic Acids

The reaction of α-methylene-indolines with NaCNBH₃ in carboxylic acids at room temperature can yield either 2β,3β-dihydro-indolines or their N-alkyl derivatives as main products with high selectivity, depending mainly on the carboxylic acid and on the reaction time when using a large excess of NaCNBH₃.     

Cascade synthesis of new aryl 2-phenylallyl sulfones from α-methylstyrene and aromatic mono- and bis-sulfonyl chlorides

Addition products of arenesulfonyl chlorides to α-methylstyrene in the presence of catalytic amounts of copper(II) chloride and triethylamine hydrochloride underwent fast dehydrochlorination (according to Hofmann’s rule) on heating in boiling acetonitrile to give the corresponding aryl 2-phenylallyl sulfones with high selectivity. This reaction underlay a one-pot procedure for the synthesis of new compounds that attract interest as potential biologically active substances, monomers, and cross-linking agents for polymeric materials from accessible starting compounds.     

An approach to the synthesis of α-l-fucopyranosyl phosphoric mono- and diesters via phosphite intermediates

The reagent chloro-β-cyanoethyl-N,N-diisopropylamino-phosphoramidite reacts smoothly with the anomeric hydroxyl group of a properly protected (benzyl) α-L-fucopyranose to afford a relatively stable phosphite intermediate in high yield. The latter can easily be converted into valuable α-L-fucopyranosyl phosphoric mono- and diesters.     

Synthesis of chiral α-ethylphenylamine salts of tartaric acid and novel application to cyanosilylation of prochiral ketones

Abstract  

Chiral α-ethylphenylamine tartaric acid salts were synthesized from α-ethylphenylamine by direct reaction with chiral tartaric acid. The crystal structure of S-(−)-α-ethylphenylamine-(2R,3R)-(−)-dihydroxybutanedioic acid was determined. The crystal is monoclinic, of space group P2_1/n , with a = 6.331(5) ?, b = 14.209(11) ?, c = 7.495(6) ?, α = 90.00o, β = 107.000(13)o, γ = 90.00o, λ = 0.7103 Ǻ, V = 644.7(9), Z = 2, D _c = 1.397 g/cm³, M _r  = 271.27 and F(000) = 288, R = 0.0477, and ωR = 0.0838 for 1388 observed reflections with I > 2σ(I). We then used the chiral α-ethylphenylamine tartaric acid salts as catalysts in the cyanosilylation of prochiral ketones, and moderate conversions were obtained.     

Ammonium carbamate type self-derivative salts of (R-)- and racemic α-methylbenzylamine

Two different compounds have formed from liquid enantiomeric (R-) and racemic α-methylbenzylamine (α-MBA, named also as 1-phenylethylamine, 1-FEA) with supercritical fluid CO₂. The crystalline solids have been characterized by elemental CHN analysis, X-ray diffraction (XRD), FTIR, ¹H, and ¹³C NMR spectroscopy, and found to be α-methylbenzylammonium α-methylbenzylcarbamate self-derivative ionic salts 1 (R/R) and 2 (rac RS), respectively, of the corresponding amines. Compound 2 (rac RS) has shown different XRD pattern from that of enantiomerically pure 1 (R/R), indicating a preferential formation of a 1:1 mixture of (R/S-) and (S/R-) or rather a racemate compound of (RS/SR-) ammonium carbamate salt (2 (rac RS)) from racemate. For thermal stability, the compounds have been checked by differential scanning calorimetry (DSC), simultaneous thermogravimetry and differential thermal analysis (TG/DTA), and in situ coupled evolved gas analysis by mass spectroscopy (TG/DTA?EGA?MS) and FTIR-gas cell (TG?FTIR). No melting point is observed because of the low thermal stability of the compounds. Decomposition stages are tried to be separated with using semi-closed (sealed with a pinhole on the top) crucibles, thus different evolution courses of CO₂ and organic vapors could be followed by MS and FTIR spectroscopy. The α-MBA vapors themselves, evolved from open crucibles could be identified by FTIR-gas cell, while vapors up to m/z = 164 have been detected by MS from semi-closed Al crucible.     

Vicarious nucleophilic substitution of hydrogen in aldehydes and Knoevenagel reaction of iminium salts with α-halocarbanions

Iminium salts derived from aromatic aldehydes react with -chlorocarbanions via two different pathways: reaction with secondary carbanion of halomethyl sulfones proceeds as the Knoevenagel condensation, while tertiary -chlorocarbanions gave products of vicarious nucleophilic substitution of hydrogen in parent aldehydes.     

An efficient synthesis of 2-isoxazolines from α-haloketone oximes and dimethyl sulfonium salts

2-Isoxazolines were synthesized efficiently from a formal [4+1] cycloaddition of nitrosoalkenes and sulfur ylides, which were generated in situ from α-haloketone oximes and dimethyl sulfonium salts. This approach provides a new method to synthesize a range of 2-isoxazolines in high yields and high regioselectivity.     

Inhibition of β-galactosidases with mono- and disaccharides

It was demonstrated that, in reactions of the hydrolysis of model substrate 2-nitrophenyl-β-D-galactopyranoside (2-NPGP) monosaccharides D-fructose and D-xylose with hydroxyl substituents oppositely directed at the neighboring carbon atoms in the furan ring, as in D-glucose, act as noncompetitive inhibitors of β-galactosidase from E. coli; for mushroom, β-galactosidases from P. canescens and A. oryzae D-galactose is a stronger inhibitor. It was also found that the inhibition constant is the highest in the case of the most active enzyme (E. coli) and is the lowest for the least active one (P. canescens).     

Indium-promoted chemo- and diastereoselective allylation of α,β-epoxy ketones with potassium allyltrifluoroborate

A practical method for the chemo- and diastereoselective allylation of α,β-epoxy ketones has been developed by using the convenient air and moisture stable reagent potassium allyltrifluoroborate. Indium metal was found to promote addition in stoichiometric or catalytic amounts, to afford α,β-epoxyhomoallylic tertiary alcohols in high yields and diastereoselectivities, without competing ring-scission of the epoxide.     

Reaction of diazonium salts with transition metals: XII. Palladium-catalyzed aryldestannylation of α-styrylstannanes by arenediazonium salts

Under palladium(0) catalysis, Ph(R₃Sn)CCH₂ (R = Me, Et and Bu) easily reacted with ArN₂BF₄ (Ar = XPh, X = H, 4-Me, 4-I, 4-MeCO, 4-EtOCO, 3-NO₂ and 4-NO₂) and selectively produced (Z)-PhCHCHAr but not Ph(Ar)CCH₂. An addition-elimination mechanism instead of the transmetallation from tin to palladium is postulated for this unusual regiochemistry.     

Synthesis of some mono- and bis-spiro-β-lactams of benzylisatin

Some new mono- and bis-spiro-β-lactams of benzylisatin were prepared by Staudinger’s ketene-imine [2+2] cycloaddition reaction. The cycloadducts were characterized by spectral data including ¹H NMR, ¹³C NMR, IR and mass spectra. The configuration of benzylisatin and one of mono-spiro-β-lactams (5a) was established by X-ray crystal analysis.     

Hydro-Dehalogenation of α-Haloketones by Tin (II) Chloride and Sodium Hydrogen Sulfide

Aromatic and aliphatic α-haloketones were effectively dehalogenated by binary systems of sodium hydrogen sulfide (soft base) and a metal chloride such as tin (II) chloride, iron (II) chloride or chromium (III) chloride (hard acid).     

Synthesis and structural study on α-substituted-1-styrylpyridinium salts : Reinvestigation of krohnke condensation

Kröhnke condensation of several cycloimmonium salts with p-dimethylaminobenzaldhyde has been studied. X-Ray diffraction, IR and Raman spectra, ¹H-and ¹³C-NMR and UV spectra of the products are discussed, being compared, when necessary, with the starting pyridinium salts. All compounds showed the Z configuration, corresponding to the more stable structure, except one, in which steric factors were predominant.     

Enantioselective α-arylation of N-acyloxazolidinones with copper(II)-bisoxazoline catalysts and diaryliodonium salts

A new strategy for the catalytic enantioselective α-arylation of N-acyloxazolidinones with chiral copper(II)-bisoxazoline complexes and diaryliodonium salts is described. The mild catalytic conditions are operationally simple, produce valuable synthetic building blocks in excellent yields and enantioselectivities, and can be applied to the synthesis of important nonsteroidal anti-inflammatory agents and their analogues.     

Generation of sulfur ylides by the desilylation of α-trimethylsilylbenzyl sulfonium salts

The [2,3]-sigmatropic rearrangement of sulfur ylides derived via the desilylation of several α-trimethylsilylbenzyl sulfonium salts has been studied. The initially formed ylide was found to rapidly equilibrate with the thermodynamically more stable ylide. In the absence of trapping reagents, a Sommelet-Hauser type rearrangement occurs.