Hydro-de-halogenation and consecutive deprotection of chlorinated N-amido-pyrrolidin-2-ones with Raney-Ni: an effective approach to gabapentin

The benzoylamino group was identified as a useful radical cyclization auxiliary that can be smoothly removed on hydro-de-halogenation of chlorinated N-substituted-pyrrolidin-2-ones with Raney-Ni. This methodology was successfully implemented in a new and appealing route to the anti-epileptic drug gabapentin.     

Application of refractive index mixing rules in binary systems of hexadecane and heptadecane with n -alkanols at different temperatures

Density and refractive index have been experimentally determined for binary liquid mixtures of hexadecane and heptadecane with 1-butanol, 1-pentanol, 1-hexanol and 1-heptanol at 298.15, 308.15 and 318.15 K. A comparative study of Lorentz—Lorenz (L-L), Weiner (W) and Heller (H), and Gladstone-Dale (G-D) relations for predicting the refractive index of a liquid has been carried out to test their validity for the eight binaries over the entire mole fraction range of hexadecane and heptadecane at the three temperatures. Comparison of various mixing rules has been expressed in terms of average percentage deviation. The performance of the Lorentz-Lorenz and Heller relations is relatively better than that of the Weiner and Gladstone-Dale relations.     

Desulfation and rearrangement of tigemonam to an isoxazolidin-5-one and the synthesis of the rearrangement product

The β-lactam antibiotic Tigemonam 2 undergoes desulfation to the N-hydroxyazetidinone 4 , which rearranges to the isoxazolidin-5-one 6 . The structure of the rearrangement product 6 was confirmed by synthesis.     

Problemi parabolici degeneri

We establish existence theorems for weak solutions of boundary value problems associated with degenerate parabolic operators.     

A journey through quality control

The Euroanalysis VII conference in Vienna included a two-day session: Quality Assurance in Analytical Chemistry. The contributions comprised 15 lectures devoted to: intra-laboratory quality measures, inter-laboratory control, formal aspects and accreditation and implementation. The paper presents an overview of the main items developed by the contributors.A survey on the session on Quality Assurance in Analytical Chemistry of Euroanalysis VIIThe authors thank the organizers of EUROANALYSIS VII and in particular Dr. B. Griepink and Dr. E. Maier of the Community Bureau of Reference (BCR) of the CEC for their support and considerable contributions.     

Dimers of 3,7-dehydrotropones (bicyclo[3.2.0]hepta-1(7),2,4-trien-6-ones)

2-(tert-Butyl)-3,7-dehydrotropone (7-(tert-butyl)bicyclo[3.2.0]hepta-1(7),2,4-trien-6-one; 1 ) was found to dimerize reversibly to 2A by [2 + 4]-cycloaddition/cycloreversion reaction. The equilibrium lies on the side of the highly strained dimer 2A in the solid state, and on the side of the monomer 1 in solution. The [2 + 4]-reaction is fully perisite-, regio- and stereoselective. Above room temperature, 1 irreversibly formed a decarbonylated dimer 6 , probably via the intermediate 9A or 9B , which resulted either from a dimerisation of 1 by [4 + 6]-cycloaddition or from a sigmatropic rearrangement of the originally formed dimer 2A or 2B . Similary, the 6-bromo derivative 14 afforded the corresponding decarbonylated dimer 15 . Should the formation of 6 and 15 be due to a primary cycloaddition then that reaction is fully peri-, site- and regioselective. Mild LiAlH₄-reduction of 6 and subsequent acetylation yielded the acetate 11 , the structure of which was established by an X-ray analysis. More vigorous LiAlH₄-treatment also reduced the terminal fulvenoid double bond of 6 and acetylation of the crude product led to the acetated 12 and 13 .