Carstensengunn4932

Detailed analysis of the stereodetermining transition structures allowed us to establish the origin of the reaction enantioselectivity.Pd-catalyzed spiroannulation of 4-bromocoumarin with alkynes has been illustrated. The reaction highlights an interesting process for cascade formation of two five-membered rings through spiroannulation followed by cyclization via C-H activation. This method offers an attractive platform for the synthesis of a broad range of indane-fused spiropentadiene chromanones in good yields.In this study, using a computational approach, we are pursuing to find a proper answer about the possible application of fused TIs as superbases through the calculation and discussion of standard thermochemistry parameters, like gas-phase basicity (GB) and proton affinity (PA). In some studied cases, the role of aromaticity/antiaromaticity fluctuations supposed to be more important than mesomeric effects. In this sense, nucleus-independent chemical shift (NICS) and anisotropy of the induced current density (ACID) were utilized in this study to probe into the aromaticity-related parameters of the proposed molecules. Results revealed the highest GB/PA values for the molecules having cyclobutadiene in between two troponimines. Additional investigation was performed into the other candidates of cyclobutadiene-fused troponimines by substituting several electron donors along with the changing position of donors. Some novel superbases offered record-holding GB/PA values so that PA magnitudes higher than 300 kcal mol-1 are now feasible for nonphosphorous neutral organic superbases (NOS).A straightforward synthesis of 1-azido-2-bromo-1,1,2,2-tetrafluoroethane on a multigram scale from 1,2-dibromotetrafluoroethane and sodium azide in a novel process initiated by organomagnesium compounds (i-PrMgCl·LiCl, turbo Grignard) is reported. Synthetic utility of the title azide in the preparation of N-tetrafluoroethylated and N-difluoromethylated five-membered nitrogen heterocycles was demonstrated with azide-alkyne cycloaddition to N-bromotetrafluoroethyl 1,2,3-triazoles, subsequent reduction to N-tetrafluoroethyl triazoles, rhodium-catalyzed transannulation with nitriles to N-tetrafluoroethylated imidazoles and rhodium-catalyzed ring-opening, and cyclization to N-difluoromethylated oxazoles and thiazoles.The mechanism for the synthesis of 2,3-bismethylenechromanes obtained by the reaction between silylethynyloxyarenes and allylic pivalates and catalyzed by a palladium complex has been investigated using computational methods rooted in density functional theory. The reaction is promoted by a C-H bond activation and the consequent bond cleavage of both substrates, followed by a novel annulation. The whole mechanism of this reaction is described together with the drawbacks that could block it. The main role played by the allyl rotation, inducing selectivity, together with the lability of the phosphine ligand and base (Cs2CO3) effects are unraveled. this website Finally, the nature of the substrates was managed, confirming that ortho-allylated silylethynyloxybenzenes lead to the same type of annulated products.GIAO 13C NMR calculation plays important roles in structural assignment for small organic molecules. Especially, higher accuracy and confidence are required for the structural assignation of complex organic molecules. In this GIAO 13C NMR calculation strategy, carbons were sorted according to their type of hybridization, radii of solvation cavity, or solvent interactions. The calculated shielding tensors of carbons in each sorted training set were linear-regressed with experimental data separately, and the obtained linear parameters were used to convert calculated shielding tensors into calculated chemical shifts. This approach shows significantly improved accuracy, especially for sp2 carbons, compared to conventional GIAO 13C NMR calculation protocols. A statistic-based probability algorithm was proposed to quantify the reliability of structural assignation. With empirical linear parameters for three commonly used NMR solvents as well as an easy-to-use script and a spreadsheet, this 13C NMR calculation protocol provides a useful tool for structural validation or assignation of ambiguous organic structures.A unique and efficient formation of 3,6-dihydro-2H-1,2-oxazines starting from α,β-unsaturated nitrones has been achieved. The nucleophilic addition of dimethylsulfoxonium methylide to the C═N bond of an α,β-unsaturated nitrone to form an aziridine N-oxide followed by the Meisenheimer rearrangement affords 3,6-dihydro-2H-1,2-oxazine in up to 70% yield. Methylene was confirmed to be incorporated at the C3 position of the ring. A wide range of β-aryl-substituted α,β-unsaturated nitrones were applicable to this reaction.The absolute configuration and conformations of (-)-tert-butylphenylphosphinoamidate were determined using three different chiroptical spectroscopic methods, namely vibrational circular dichroism (VCD), electronic circular dichroism (ECD), and optical rotatory dispersion (ORD). In each of the spectroscopic methods used, experimental data for the (-)-enantiomer of tert-butylphenylphosphinoamidate were measured in the solution phase. Using the concentration-dependent experimental infrared spectra, the existence of dimers in the solution was investigated, and the monomer-dimer equilibrium constant was determined. Concomitant quantum mechanical predictions of the VCD, ECD, and ORD for monomeric tert-butylphenylphosphinoamidate were carried out using density functional theory (DFT) calculations using the B3LYP functional and the 6-31G(d), 6-311G(2d,2p) and aug-cc-pVDZ basis sets. Similar predictions for dimeric tert-butylphenylphosphinoamidate were also obtained using the B3LYP/6-31G(d) method. A comparison of theoretically predicted data with the corresponding experimental data led to the elucidation of the absolute configuration as (-)-(R)-tert-butylphenylphosphinoamidate with one predominant conformation in the solution. This conclusion was independently supported by X-ray analysis of the complex with (+)-R-2,2'-dihydroxy-1,1'-binaphthol ((+)-R- BINOL).