Access to cyclopropanes with geminal trifluoromethyl and difluoromethylphosphonate groups.

A synthetic route to the bench-stable fluorinated masked carbene reagent diethyl 2-diazo-1,1,3,3,3-pentafluoropropylphosphonate, bearing a trifluoromethyl and a difluoromethyl group is reported for the first time. Its application in CuI-catalyzed cyclopropanation reactions with aromatic and aliphatic terminal alkenes under mild reaction conditions is demonstrated. In total, sixteen new cyclopropanes were synthesized in good to very good yields.

Ru-Catalyzed Hydrogen Atom Transfer/C-F Bond Cleavage of Difluoroalkyl Diazos with Hantzsch Ester via a Photocatalytic Radical Process.

A Ru-catalyzed reaction of difluoroalkyl diazo compounds with Hantzsch ester under visible light to achieve the formation of α-fluorovinylphosphonates via a radical process has been developed. Mechanistic experiments and density functional theory calculations reveal that the generation of a carbon radical is directly through the hydrogen atom transfer (HAT) by Hantzsch ester. This system represents the first example of generation of carbon radicals from diazo compounds via Hantzsch-ester-assisted HAT and also demonstrates a new radical-involved pathway for the difluoroalkyl diazo compounds.

Hypervalent-iodine mediated one-pot synthesis of isoxazolines and isoxazoles bearing a difluoromethyl phosphonate moiety.

A one-pot, regioselective 1,3-dipolar cycloaddition of in situ generated (diethoxyphosphoryl)difluoromethyl nitrile oxide toward selected alkenes and alkynes is reported. This protocol enables facile access to 3,5-disubstituted isoxazolines and isoxazoles bearing a CF2P(O)(OEt)2 moiety in good to excellent yields, under mild reaction conditions.

In Situ Generation of Unstable Difluoromethylphosphonate-Containing Diazoalkanes and Their Use in [3 + 2] Cycloaddition Reactions with Vinyl Sulfones.

A [3 + 2] cycloaddition reaction of unstable difluoromethylphosphonate-containing diazoalkanes with vinyl sulfones under simple reaction conditions is developed, which provides an efficient route toward functionalized fluorinated pyrazolines derivatives in good chemical yields. The difluoro diazoalkanes are generated in situ using t-BuONO for the diazotization of (ß-amino-α,α-difluoroethyl)phosphonates, and their stabilities and reactivities were carefully investigated.

A Selectfluor-promoted oxidative reaction of disulfides and amines: access to sulfinamides.

An unprecedented transition-metal-free oxidative reaction of disulfides and amines with Selectfluor as a mild oxidant under aerobic conditions was developed. This reaction was conducted under mild conditions and tolerated a wide range of coupling partners including disulfides and amines, affording the corresponding sulfinamide products in good chemical yields. Furthermore, this reaction could be used in gram-scale synthesis. This reaction enriches the research content of Selectfluor and provides a valuable vista for the convenient synthesis of sulfinamides.

The self-disproportionation of enantiomers (SDE) via column chromatography of ß-amino-α,α-difluorophosphonic acid derivatives.

This work presents the first study of the self-disproportionation of enantiomers via chromatography (SDEvC) of ß-aminophosphonic acid esters, several of which have been synthesized for the first time. Three types of structures were examined, N-acetylated, dipeptide construction with N-Cbz glycine, and a free amine. In the latter case, this is the first time that SDEvC has been reported for free amine amino acids. In all the three types of structures, significant SDE magnitudes (Δee's up to 55%) were exhibited underscoring the ubiquitous nature of the SDE phenomenon. Chemical models of homo- versus heterochiral intermolecular interactions are proposed to rationalize the SDE magnitude differences amongst these new ß-aminophosphonic acid derivatives. In addition, the incorporation of additional, competing binding modes to a molecule, was found to lead to a reduction of the SDE magnitude by shifting the intermolecular binding away from the stereogenic center and/or by leading to a convoluted binding system that disrupts the structured and relatively stable assemblies that give rise to the SDE.

Synthesis and Characterization of Oxazaborinin Phosphonate for Blue OLED Emitter Applications.

A blue-light emitting material based on a boron complex containing heteroaromatic phosphonate ligand is synthesized and characterized. The Phospho-Fries rearrangement is used in the synthesis route of the ligand as a convenient method of introducing phosphonate groups into phenols. Structural, thermal and photophysical properties of the resulting oxazaborinin phosphonate compound have been characterized. DFT geometry optimizations were studied as well as the spatial position and symmetry of the HOMO and LUMO. Good thermal stability up to 250 °C enables vacuum deposition methods next to solution processing. Combining the work function with the optical band gap from UV-Vis measurements shows that band alignment is possible with standard contact materials. Photoluminescence reveals an emission peak at 428 nm, which is suitable for a blue light-emitter.

New Chiral Reagent for Installation of Pharmacophoric (S)- or (R)-2-(Alkoxyphosphono)-1-amino-2,2-difluoroethyl Groups.

A new chiral reagent has been developed for generalized installation of pharmacophoric (S)- or (R)-2-(alkoxyphosphono)-1-amino-2,2-difluoroethyl group into organic compounds. The original synthetic application of this new reagent is exemplified by Friedel-Crafts reactions with indoles, which proceed efficiently with excellent diastereoselectivity to give enantiomerically pure products.

Synthesis of (α,α-difluoropropargyl)phosphonates via aldehyde-to-alkyne homologation.

An efficient synthetic methodology to a series of novel alkynes bearing a difluoromethylenephosphonate function via a Corey-Fuchs-type sequence starting from (diethoxyphosphoryl)difluoroacetic aldehyde is described. Dehydrobromination of the intermediate (3,3-dibromodifluoroallyl)phosphonate with potassium tert-butoxide gave rise to the corresponding bromoalkyne, whereas upon treatment with lithium base, the generation of ((diethoxyphosphoryl)difluoropropynyl)lithium has been achieved for the first time. The synthetic potential of this lithium reagent was further demonstrated by its reactions with selected electrophiles such as aldehydes, ketones, triflates, chlorophosphines, and chlorosilanes, leading to the corresponding propargyl phosphonates in good to excellent yields. However, in the case, of sterically hindered aldehydes, (α-fluoroallenyl)phosphonates were the solely isolated products.