Diastereoselective Electrophilic Amination of Chiral 1‐Benzoyl‐2,3,5,6‐tetrahydro‐3‐methyl‐2‐(1‐methylethyl)pyrimidin‐4(1H)‐one for the Asymmetric Syntheses of α‐Substituted α,β‐Diaminopropanoic Acids

The chiral compounds (R)‐ and (S)‐1‐benzoyl‐2,3,5,6‐tetrahydro‐3‐methyl‐2‐(1‐methylethyl)pyrimidin‐4(1H)‐one ((R)‐ and (S)‐ 1 ), derived from (R)‐ and (S)‐asparagine, respectively, were used as convenient starting materials for the preparation of the enantiomerically pure α‐alkylated (alkyl=Me, Et, Bn) α,β‐diamino acids (R)‐ and (S)‐ 11 – 13 . The chiral lithium enolates of (R)‐ and (S)‐ 1 were first alkylated, and the resulting diasteroisomeric products 5 – 7 were aminated with ‘di(tert‐butyl) azodicarboxylate’ (DBAD), giving rise to the diastereoisomerically pure (≥98%) compounds 8 – 10 . The target compounds (R)‐ and (S)‐ 11 – 13 could then be obtained in good yields and high purities by a hydrolysis/hydrogenolysis/hydrolysis sequence.     

The structure,magnetic and spectral properties of 4-acetylpyridine N-oxide complexes of copper(II) propionates

The synthesis and characterization of CuX₂L; (X = CH₃CH₂COO^?, ClCH₂CH₂COO^?, CH₃CHClCOO^? or CH₃CCl₂COO^?; and L = 4-acetylpyridine N-oxide) is reported. The characterization of these compounds was based on electronic, infrared and EPR spectra, as well as magnetic measurements over the temperature range. Several correlations between the spectral and magnetic data as well as pK_a values of the respective acids were found and discussed. On the basis of spectral and magnetic data the structures of the compounds are discussed.     

Hazard in reaction of titanium raw materials with sulphuric acid

The reaction of ilmenite titanium raw material with sulphuric acid was investigated in ‘hazard’ type calorimetric system. The investigations show the essential influence of initial temperature, particle size distribution and concentration of sulphuric acid on rate and heat power of reaction and determine the limits of safety of the process and also its efficiency.     

Intensity analysis of f-f transitions and correlation with conductivity and ultrasonic absorption for holmium solvates

Absorption spectra of holmium nitrate in MFA and DMF have been measured in the range 8000–42000 cm^?1. The τ_λ parameters were evaluated from the experimental oscillator strengths using the Judd equation. For Ho(NO₃)₃ in DMF a considerable increase in τ₂ was observed, suggesting the existence of inner-sphere species in this system. This suggestion was verified by ultrasonic absorption and conductivity measurements.