Solvent-free silica gel mediated decarboxylation of C–O coupling products of β-diketones and β-oxo esters with malonyl peroxides

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Extraction Properties of Oligodentate Carbamoylmethylphosphine Oxides and β-Aminophosphine Oxides Toward Lanthanides and Rhenium(VII)

Abstract

The extraction properties of a series of carbamoylmethylphosphine oxides and β-aminophosphine oxides with lanthanide metal ions is presented. Tris[bis(2-diphenyl- phosphorylethyl)-aminoethyl]amine is shown to be highly effective for extraction of Re(VII).     

New Method of Halogenation of Organophosphorus Compounds

Abstract

N-Chloroalkylamines react usually with tervalent phosphorus compounds to afford products, containing the phosphorus-nitrogen bond. We found that the sterical hindrances favour to the nucleophilic attack of the tervalent phosphorus atom on the “positive” halogen atom with the formation of phosphorus halogenated products. Sterical hindered N-halogenoalkylamines I (Hlg[dbnd]Cl,Br) possess active halogenating properties to react with tervalent phosphorus compounds similarly to methane tetrahalides. Reaction proceeds via the formation of halogenophosphonium intermediates 2, containing an anion R₂N, which reacts with alcohols to afford alkoxyphosphonium salts, transforms into halogenophosphonium salts or P-halogenoylids. Advantages of N-halogenoalkylamines 1 over methane tetrahalides are more high chemical selectivity. Moreover the inclusion of chiral substituents R into N-halogenoalkylamines gives enantioselective halogenating reagents.     

Synthesis of 1‐silacyclopent‐2‐ene derivatives using 1,2‐hydroboration, 1,1‐organoboration and protodeborylation

The reaction of di(alkyn‐1‐yl)vinylsilanes R¹(H₂C═CH)Si(C≡C―R)₂ (R¹ = Me ( 1 ), Ph ( 2 ); R = Bu (a), Ph (b), Me₂HSi (c)) at 25°C with 1 equiv. of 9‐borabicyclo[3.3.1]nonane (9‐BBN) affords 1‐silacyclopent‐2‐ene derivatives ( 3a , 3b , 3c , 4a , 4b ), bearing one Si―C≡C―R function readily available for further transformations. These compounds are formed by consecutive 1,2‐hydroboration followed by intramolecular 1,1‐carboboration. Treated with a further equivalent of 9‐BBN in benzene they are converted at relatively high temperature (80–100°C) into 1‐alkenyl‐1‐silacyclopent‐2‐ene derivatives ( 5a , 5b 6a , 6b ) as a result of 1,2‐hydroboration of the Si―C≡C―R function. Protodeborylation of the 9‐BBN‐substituted 1‐silacyclopent‐2‐ene derivatives 3 , 4 , 5 , 6 , using acetic acid in excess, proceeds smoothly to give the novel 1‐silacyclopent‐2‐ene ( 7 , 8 , 9 , 10 ). The solution‐state structural assignment of all new compounds, i.e. di(alkyn‐1‐yl)vinylsilanes and 1‐silacyclopent‐2‐ene derivatives, was carried out using multinuclear magnetic resonance techniques (¹H, ¹³C, ¹¹B, ²⁹Si NMR). The gas phase structures of some examples were calculated and optimized by density functional theory methods (B3LYP/6‐311+G/(d,p) level of theory), and ²⁹Si NMR parameters were calculated (chemical shifts δ²⁹Si and coupling constants ⁿJ(²⁹Si,¹³C)). Copyright © 2014 John Wiley & Sons, Ltd.     

Which Stereoinductor Is Better for Asymmetric Functionalization of α-Amino Acids in a Nickel(II) Coordination Environment? Experimental and DFT Considerations

The results of extended comparative investigation of nickel(II) Schiff base complexes (containing various auxiliary chiral moieties) commonly used as a methodological platform for the asymmetric synthesis of tailor-made α-amino acids are provided. The following issues are addressed: 1) redox activity (determining the possibility for electrochemically induced reactions); 2) quantitative estimation of the reactivity of deprotonated complexes towards electrophiles; and 3) quantum-chemical estimation of noncovalent interactions in the metal coordination environment (which shed light on the origin of the stereochemical outcome observed for different stereoinductors). Possible mechanisms that determine the relationship between the stereochemical configuration of a molecule and its electronic structure are discussed. The DFT-calculated HOMO–LUMO energies and localization, as well as relative energies for the (S)- and (R)-alanine derivatives, that determine the stereoinduction efficiency in thermodynamically controlled reactions in nickel(II) coordination are provided. The computational data are supported by experimental results on the monobenzylation of glycine derivatives.