Ring-opening hydrofluorination of 2,3- and 3,4-epoxy amines by HBF4·OEt2: application to the asymmetric synthesis of (S,S)-3-deoxy-3-fluorosafingol

Treatment of a range of 2,3- and 3,4-epoxy amines with HBF(4)·OEt(2) at room temperature results in fast and efficient S(N)2-type ring-opening hydrofluorination to give stereodefined amino fluorohydrins. Operational simplicity, scalability, and short reaction time at ambient temperature are notable features of this method. The utility of this methodology is exemplified in a concise asymmetric synthesis of (S,S)-3-deoxy-3-fluorosafingol.     

Axiomatising the Prior Future in Predicate Logic

Prior investigated a tense logic with an operator for ‘historical necessity’, where a proposition is necessary at a time iff it is true at that time in all worlds ‘accessible’ from that time. Axiomatisations of this logic all seem to require non-standard axioms or rules. The present paper presents an axiomatisation of a first-order version of Prior’s logic by using a predicate which enables any time to be picked out by an individual in the domain of interpretation.     

Consistent Composition of Bäcklund Transformations Produces Confined Maps

We prove that difference equations arising from consistent compositions of Bäcklund transformations of the continuous Painlevé equations possess the singularity confinement property.     

Existence of dual mass: Experimental evidence

This second article on dual mass investigates the physical evidence for the existence of dual mass. We discuss three possible observations that could be used to bound the amount of dual mass in the solar system: the Eotvos experiment, the relativistic pendulum, and planetary orbits. The Eotvos experiment is used to conclude that the ratio of dual mass to ordinary mass is a constant. Under this assumption the dual mass effects are proportional to a dimensionless parameter which is proportional to the ratio of dual to ordinary mass. We consider two effects: First we show that a pendulum swinging in the gravitational field of the earth would be subject to a precession of the plane of oscillation; second, we show that dual mass in the solar system creates a lifting of planetary orbits. Observations of a pendulum should yield to an accuracy of 10^–4 and limits on the detectability of the planetary lifting puts an upper bound on of about 10^–1.     

New colorimetric reagents for determination of trace amounts of oxidants and reductants

The mixed-ligand complexes H[Fe(phen)(CN)(4)] and K(2)[Fe(phen)(CN)(4)] (where phen represents 1,10-phenanthroline) have been found useful as colorimetric reagents for trace determination of reductants and oxidants. Their properties and some representative applications are described.     

The systematics of h112 proton alignment in 157, 158, 159Er

Rotational bands have been observed in ^{157, 158, 159}Er to very high spin ($\text{J ～ 41}\text{h}\text{?}$). Upbends are found, due to the alignment of two h_{$\text{11}\text{2}$} protons at $\text{0.40 ?}\text{h}\text{?}\text{ω ? 0.46}\text{MeV}$ in all bands. A systematic shift with neutron number of the band-crossing frequency is observed and is related to a change in quadrupole deformation ?₂.