A Rare Alder-ene Cycloisomerization of 1,6-Allenynes

Thermally induced cycloisomerization reactions of 1,6-allenynes gives α-methylene-γ-lactams via intramolecular Alder-ene reactions. The mechanism is supported by computational and deuterium labelling studies. This thermal, non-radical method enables the discovery of a hitherto unknown route that proceeds via a divergent mechanism distinct from the previous [2+2] cycloisomerization manifold.     

Titanium-mediated rearrangement of cyclopropenylmethyl acetates to (E)-halodienes

TiCl(4) and TiBr(4) rapidly transform cyclopropenylmethyl acetates to (E)-halodienes via ring-opening to allyl-vinyl cations. DFT calculations suggest that the regioselectivity of the halogenation of this cationic intermediate by [TiX(4)OAc](-) is under thermodynamic control, while the stereoselectivity is governed by kinetics.     

The NMR reciprocity theorem for arbitrary probe geometry

It is shown that the NMR reciprocity theorem is a variant of a problem considered by Lorentz in 1895. This formulation is quite general and applies to electric-dipole-based as well as coil-based or resonator-based magnetic resonance probes. The reasoning is related to, but different from, the proof of the reciprocity theorem for radiofrequency networks and for transmit/receive antenna systems in telecommunications. The signal-to-noise ratio of the NMR experiment is also discussed in very general terms.     

Optimal projection equations for reduced-order modelling,estimation, and control of linear systems with multiplicative white noise

The optimal projection equations for quadratically optimal reduced-order modelling, estimation, and control are generalized to include the effects of state, control, and measurement dependent noise.     

Estimation of tetrahydro, dihydro and fully oxidised pterins by high-performance liquid chromatography using sequential electrochemical and fluorometric detection

A method is described for the separation and detection of tetrahydro, dihydro and fully oxidised pterins in a single chromatographic run using ion-pair reversed-phase high-performance liquid chromatography. Tetrahydropterins are detected by electrochemical oxidation, dihydropterins by fluorescence following post-column electrochemical oxidation and the fully oxidised pterins by their natural fluorescence. The post-column electrochemical conversion of the non-fluorescent dihydropterins to fluorescent compounds is proportional to the amount injected over three orders of magnitude. Because of the relative selectivity of the fluorescence detection and the low potential required to oxidise the tetrahydropterins, all the oxidation species of the pterins may be measured in biological samples with minimal sample clean-up.     

Condensate correlations and the λ-transition in 4He

The existence of the λ-transition in liquid ⁴He implies the existence of two-point macro wave-functions in the second reduced density matrix of the system and the existence of a new bulk characteristic length.     

Chemoselective reduction of 2-acyl-N-sulfonylpyrroles: synthesis of 3-pyrrolines and 2-alkylpyrroles

The partial reduction of pyrroles is not a common practice even though it offers a potential route to pyrroline building blocks, commonly used for synthesis. We have investigated the reduction of 2-acyl-N-sulfonylpyrroles and by varying the hydride source and solvent, achieved a chemoselective reduction, leading to 3-pyrrolines and alkyl pyrroles in high yield.