Silica-supported copper-iron catalysts for hydrogenolysis reactions characterized by Mössbauer spectroscopy

A special preparation procedure has been developed to provide a very uniform distribution of iron throughout the copper precursor supported on silica. The best performance for hydrogenolysis of methyl acetate has been obtained for a catalyst prepared in a one-step procedure, in which iron(III) and copper(II) were injected together into a suspension of silica at a constant pH level. It is found that the main part of the iron has been incorporated into the formed copper hydrosilicate. After reduction and under reaction conditions, only about 6% of the iron atoms are in the Fe⁰ state. This Fe⁰ is expected to be responsible for the enhancement of the catalyst activity in hydrogenation and hydrogenolysis reactions.     

Structural colour in animals—simple to complex optics

Over the past 30 years, optics well known to the physicist have been identified in their multitudes in nature. Multilayer reflectors, diffraction gratings, liquid crystals and structures that scatter light—devices explained using “simple” optical theory—have been found in animals with a diversity of designs. For many years the potential to employ these designs commercially has been clear, although only one optical device in animals has been taken through to the manufacture stage—the fly-eye antireflector. Now, with the beginnings of “complex” optical study in biological specimens, and consequent identification of photonic band gaps, animal reflectors are being taken seriously as promising first stages in the design process of optical engineers. However, natural photonic crystals are often highly complex structures at the nano-scale that may lie beyond the limits of current engineering. This in turn justifies the study of cellular engineering—maybe we can also exploit the flawless processes of manufacture employed by animals.     

The Wittig Reaction in Industrial Practice

The effects of a scientific discovery on industrial practice are illustrated with reference to the Wittig reaction. The aim of utilizing the Wittig reaction of linking terpenoid building blocks to give vitamin A and carotenoids on an industrial scale prompted extensive research and development work of a synthetic and chemical engineering nature. The importance of the Wittig reaction and its variants in the synthesis of active compounds and fine chemicals in industrial research is demonstrated in the present article.     

Synthesis and 20π-electrocyclisation of heptahendecafulvadiene - An unusual sequence of pericyclic processes

Upon thermal activation the newly synthesised heptahendecafulvadiene E ( 3) is isomerised into the pentacyclic hydrocarbons 9/11 (xylene,t_1/2(150°C) ca.5min), the formation of which is explained by initial conrotatory 20-electron electrocyclisation followed by a cascade of 10π/6π-pericyclic processes.     

2D-NMR: Part VI. 2D-INADEQUATE spectral analysis and crystal structure of tricyclo[7.3.1.02,7]tridecane

2-Hydroxy-13-oxo-tricyclo[7.3.1.0^2,7]tridecane derivatives can be obtained by reaction of cyclohexanone with alcohols under alkaline conditions. The unambiguous assignment of all signals of the¹H-NMR- and¹³C-NMR-spectrum is possible by 2D-¹H-¹³C-shift correlation and 2D-INADEQUATE. Compound1 crystallizes in space group P2₁/n witha=8.518 (1),b=14.789 (2),c=19.321 (2) Å, =94.91 (1)°,Z=8,D _c =1.22 Mg cm^–3. The structure refined toR=0.100 andR _w =0.097 for 1719 observed reflections. Two independent molecules form centrosymmetric hydrogen-bonded dimers.Part V:Haslinger E.,Kalchhau-ser H.,Robien W.,Steindl H., Monatsh. Chem.115, 597 (1984).     

2-(2-pyridyl-)ethyl esters A new carboxyl protecting group in peptide synthesis

2-(2-pyridyl-)ethyl esters are used as chemically inert, highly selective protecting groups that are removable under mild conditions via a two step procedure.     

Tris-[2.21]- and tris-[2.2.2]-σ-homobenzenes

Tris-[2.2.1]- and tris-[2.2.2]-σ-homobenzenes are synthesised by reaction of 1,1′-bicyclobutenyl with appropriate dienophiles and hydrogenation of the adducts.