Marcin Kaźmierczak

Influence of fluorine substituents on the NMR properties of phenylboronic acids.

The paper presents results of a systematic NMR studies on fluorinated phenylboronic acids. All possible derivatives were studied. The experimental 1H, 13C, 19F, 11B, and 17O spectral data were compared with the results of theoretical calculations. The relation between the calculated natural bond orbital parameters and spectral data (chemical shifts and coupling constants) is discussed. The first examples of 10B/11B isotopic effect on the 19F spectra and 4JFO scalar coupling in organic compounds are reported. Copyright

17O NMR studies of substituted 1,3,4-oxadiazoles.

Three series of substituted 1,3,4‐oxadiazoles were studied by 17O NMR spectroscopy. Chemical shifts values were correlated with empirical Hammett parameters as well as calculated bond lengths and chemical shielding values. Copyright

Latest achievements in the preparation of fluorinated aminophosphonates and aminophosphonic acids

GRAPHICAL ABSTRACT ABSTRACT The goal of this mini review is to describe advances and achievements, particularly the contributions of the recent years, in synthesis and applications of α-monofluoro-, α,α-difluoro- or trifluoromethyl aminophosphonate and aminophosphonic acid derivatives. In this article the literature is covered since end of 2012.

Functionalization of α-hydroxyphosphonates as a convenient route to N-tosyl-α-aminophosphonates

Direct conversion of the α-hydroxyl group by para-toluenesulfonamide to yield α-(N-tosyl)aminophosphonates is reported. α-Aminophosphonates 23a,b–37a,b were obtained from the corresponding α-hydroxyphosphonates 6a,b–21a,b in the presence of K2CO3, via the retro-Abramov reaction of the appropriate aldehydes, 1–5. The subsequent formation of imines with simultaneous addition of diethyl phosphite provided access to the α-sulfonamide phosphonates 23a,b–37a,b with better diastereoselectivity than in the case of the Pudovik reaction. The mechanism for this transformation is proposed herein. When Cbz N-protected aziridine 9a,b and phenylalanine analogue 12a,b were exploited, intramolecular substitution was observed, leading to the corresponding epoxide 38 as the sole product, or oxazolidin-2-one 39 as a minor product. Analogous substitution was not observed in the case of proline 18a,b and serine 21a,b derivatives.

A- and B-fluorinated aminophosphonates–Synthesis and properties

GRAPHICAL ABSTRACT ABSTRACT Interest in synthesis of fluorinated aminophosphonates has grown significantly in recent years due to their promising applications in medicinal and bioorganic chemistry. We report herein efficient and general methods for the synthesis of α- and β-monofluorinated aminophosphonates. Series of β-fluoro aminophosphonates were prepared in nucleophilic DAST-mediated fluorination of α-hydroxyphosphonates. The Horner–Wadsworth–Emmons reaction between carbonyl compounds containing an amino group and lithiated tetraethyl fluoromethylenediphosphonate was used in the synthesis of α-fluorinated-γ-aminophosphonates. Futhermore, this protocol was efficiently applied in the synthesis of dipeptide analogues α-fluorinated-γ-aminophosphonates.

Multinuclear magnetic resonance studies of 2-aryl-1,3,4-selenadiazoles

2‐Aryl‐1,3,4‐selenadiazoles were studied by 1H, 13C, 15N and 77Se NMR spectroscopy. The results (chemical shifts and coupling constants) were correlated with Hammett substituent parameters as well as calculated chemical shifts and bond lengths. Copyright

The nitrogen inversion in fused isoxazolidinyl derivatives of substituted uracil: synthesis, NMR and computational analysis

A series of fused isoxazolidines have been prepared via 1,3-dipolar cycloaddition reactions of N-protected methylenenitrones with 1,3-dimethyluracil derivatives, and their NMR spectra have been recorded in TFA-d and in CDCl3 over a wide range of temperatures. The spectra indicate the presence of two invertomers for all isoxazolidines. Barriers to nitrogen inversion in the cycloadduct 6a have been determined using DFT quantochemical calculations. Our estimates have shown that the inversion proceeds at more complex path, involving four structures of local minima and four transition states.

Multinuclear magnetic resonance studies of 2-aryl-1,3,4-thiadiazoles: NMR studies of 1,3,4-thiadiazoles

The 1H, 13C and 15N spectra of aryl‐substituted 1,3,4‐thiadiazoles were recorded. The results obtained were correlated with Hammett coefficients. The experimental results were compared with DFT‐calculated chemical shifts. The results obtained were compared with those for 1,3,4‐oxadiazoles and 1,3,4‐selenadiazoles. Copyright