A new finding in selective Baeyer-Villiger oxidation of α-fluorinated ketones; a new and practical route for the synthesis of α-fluorinated esters

α-Fluorinated esters were effectively prepared by the Baeyer-Villiger oxidation of α-fluorinated ketones with m-chloroperbenzoic acid (m-CPBA) under mild conditions. The yield of the esters was influenced by the choice of solvent, base, and substituent on the aryl group of the ketones. 4-Methoxyphenyl substituted fluoroketones were oxidized almost quantitatively with m-CPBA within 10 min to 12 h at room temperature using 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP) as a cosolvent with CH₂Cl₂ (1:1, v/v) and aqueous buffer (KH₂PO₄-NaOH, pH 7.6) as an additive base. The oxidation reaction rates of α-fluorinated ketones were higher than those of the corresponding non-fluorinated ketones. The fluorine atom at α-position of fluoromethyl aryl ketones enhanced the reactivity in the Baeyer-Villiger oxidation.     

Intermolecular-medium and intramolecular-weak hydrogen bonding chains in the crystals of chiral trifluoromethylated amino alcohols

A structural feature of hydrogen bonding chains found in the crystals of trifluoromethylated amino alcohols is reported. Hydrogen bondings of 3-(N,N-dialkylamino)-1,1,1-trifluoro-2-propanols construct chiral spiral hydrogen bonding chains. Lone pairs on the nitrogen atoms of the amino alcohols participate in two hydrogen bondings. Detailed structural analysis of the hydrogen bonds of the 3-(N,N-dimethylamino)-1,1,1-trifluoro-2-propanol suggested that the chain built up with alternating intermolecular-medium and intramolecular-weak hydrogen bonds. The medium intermolecular hydrogen bond, which transfers a proton from the hydroxy group to the amino nitrogen, would make a tentative zwitterionic form of the molecule. Then, electrostatic attraction between the charges in the zwitterion centers induced a weak intramolecular hydrogen bond.     

Cu-deposits on Mg metal surfaces promote electron transfer reactions

The enhancement of the electron transfer processes in the Grignard reagent formation-type ring silylation and the defluorination–silylation of perfluoroalkyl benzenes by Cu(0)-deposited Mg metal were confirmed. Microscopic analysis and substituent effects implied a different reduction process in the presence of Cu-deposited Mg metal than in the presence of bare Mg metal.     

A facile access to α-phenylselenenyl carbonyl compounds by electrochemical oxidation

A novel α-phenylselenenylation of carbonyl compounds has been performed by electrolysis of a solution of ketones, diphenyl diselenide, tetraethylammonium bromide, and magnesium bromide in polar solvents (MeOH, AcOH, MeCN). The electrolysis enables us to prepare the desired seleno-carbonyl compounds without employing strong bases and the activated selenenyl reagents PhSeX.     

Unusual reactions of N-allylic difluoroenamines under thermal conditions

N-Allylic difluoroenamines exhibited unusual behaviors under thermal conditions; N-allyl difluoroenamines in refluxing xylene afforded not only aza-Claisen rearrangement products, but also 2-azabicyclo[2.1.1]hexanes, whose formation could be explained via intramolecular [2+2]-cycloaddition, whilst N-prenyl difluoroenamine underwent an ene reaction to give the pyrrolidine as a sole product.     

Mg-promoted double silylation of trifluoroacetimidoyl chlorides. A new entry to the fluorinated dianion equivalents

[reaction: see text] A Mg(0)/Me(3)SiCl system was found to be effective for the preparation of a novel fluorinated dianion equivalent. A one-pot reaction sequence involving reductive C-F and C-Cl bond cleavage reactions of trifluoroacetimidoyl chlorides afforded bis-silylated difluoroenamines. Subsequent carbon-carbon bond-forming reactions of the bis(silyl)enamines with two kinds of electrophiles gave a variety of difluorinated imines.     

Towards novel difluorinated sugar mimetics; syntheses and conformational analyses of highly-functionalised difluorinated cyclooctenones

Highly-functionalised difluorinated cyclooctenones were synthesised from trifluoroethanol using either metallated difluoroenol acetal or carbamate chemistry, followed by a [2,3]-Wittig rearrangement or aldol reaction. Efficient RCM reactions afforded the title compounds which showed rather restricted fluxional behaviour by VT (19)F NMR. Topological characterisation by molecular modelling and NOESY/ROESY experiments offered a number of challenges, but allowed the identification of two favoured boat-chair conformers which interconverted by pseudorotation with relatively large activation barriers.     

A novel selenium-mediated spiroannelation : one-step preparation of d1-theaspirane fron α-dihydroionol

d1-Theaspirane (1) was prepared by the selenium-mediated electrochemical oxidation of α-dihydroionol (3), via a novel selenium-mediated spiroannelation.     

Functionalized fluoroalkyl and alkenyl silanes: Preparations, reactions, and synthetic applications

Preparations, reactions, and synthetic applications of functionalized fluoroalkyl and alkenyl silanes have been summarized. This review focuses mainly on the chemistries of (1) 1-substituted difluoromethylsilanes (XCF₂SiR₃), (2) 1-substituted 2,2-difluorovinylsilanes (CF₂CXSiR₃), (3) trifluoroisopropenyl, trifluoroacetimidoyl, and trifluoroacetyl silanes [CF₃C(SiR₃)X, XCH₂, NAr, O] and (4) other fluorinated alicyclic silanes.     

One-pot synthesis of 3-fluoro-4-(trifluoromethyl)quinolines from pentafluoropropen-2-ol and their molecular modification

Pentafluoropropen-2-ol (PFP) was prepared by the reaction of hexafluoroacetone (HFA) with Mg/TMSCl. The one-pot tandem sequential reactions of PFP via Mannich addition with aldimines followed by Friedel-Crafts cyclization and aromatization afforded the title quinolines. A variety of corresponding 3-substituted quinolines were derived from the title quinoline by nucleophilic substitution of 3-fluorine with nucleophiles. A defluorinative transformation of the 4-trifluoromethyl group of the title quinoline with hydrazine afforded pyrazoloquinoline.