Gamma-p-toluenesulfonyl-alpha,beta-epoxysilane: a new and practical acrolein beta-anion equivalent

[reaction: see text] Reaction of gamma-p-toluenesulfonyl-alpha,beta-epoxysilane with alkyl halides and aldehydes followed by treatment with n-Bu4NF affords alpha,beta-unsaturated aldehydes via a Brook rearrangement-mediated tandem process under extremely mild conditions.     

A new practical one-pot access to sulfonimidates

Sulfonimidates were prepared from sulfinamides and iodosobenzene in a very mild one-pot procedure in good to excellent yields. This reaction allows quick and efficient access to a class of molecules of important synthetic as well as biological and industrial interest. [reaction: see text]     

A new, practical access to amidyl radicals

Amidyl radicals are readily generated from N-allylsulfonimides by the action of a xanthate and a small amount of a peroxide as initiator. The process involves extrusion of sulfur dioxide from an N-amidosulfonyl radical by rupture of the nitrogen-sulfur bond; in some cases, the N-amidosulfonyl radical is prematurely captured by the internal olefinic trap.     

A new practical one-pot conversion of phenols to anilines

A novel one-pot synthesis of anilines from phenols was developed. Using this methodology, anilines are produced in good yield (86%) by a reaction of phenols with 2-bromo-2-methylpropionamide and NaOH in DMA via Smiles rearrangement. Phenols, which are substituted electron-withdrawing groups, are more reactive for Smiles rearrangement. Thiophenols are also converted to anilines. The process is a convenient, safe, and inexpensive method for large-scale preparation of anilines. [reaction: see text]     

On the validity of the BEBO method

The use of tha BEBO method proposed by Johnston and Parr is considered, taking into account the observations of Jordan and Kuafman. It is found that the original formulation is applicable even when the new values for noble gas pairs are employed,if an appropriate choice of the constant in Pauling's relation is made.     

On the validity of single atom chemistry

This study is intended to apply to the many experiments in which small numbers of radioactive isotopes are artificially produced whose half lives are approximately the same time as that required for chemical identification. Conventional chemical kinetics combined with radioactive decay yields equations that were analyzed for their applicability to regimes containing much less than a statistical ensemble of atoms. Deviations from the predicted most-probable value for the concentration of a given chemical species are calculated using standard probability functions. It was found that a surprisingly small number of atoms is required to establish chemical identity under the usual conditions of experimentation.     

On establishing the validity of enthalpy-entropy relationships

All the methods so far proposed for deriving enthalpy-entropy relations fail to take into consideration the physical reasons for implied functional dependence between the activation parameters. In order to avoid spurious results it is essential to establish first the physical basis upon which the variation in the specific reaction rate itself depends, and then to carry that information through to the enthalpy-entropy plane.The proposals made here are of general application for establishing valid functional enthalpy-entropy relations, whatever their form, and in this context linear correlations are merely a subset.     

Preliminary results of a small X-ray irradiator for equivalent dose estimation

In most established method for luminescence dating, the ratio of ⁹⁰Sr/⁹⁰Y radionuclides has been employed to provide reference laboratory doses to sample. Recently a small X-ray irradiator (Varian VF-50J) was introduced as an alternative to the traditionally used radioactive sources. Test results are presented whether the use of the small X-ray irradiator is possible in the dating technique. Aspects of the assessment of the X-ray irradiator include consideration of the measured optically stimulated luminescence signal and the relationship between X-ray tube currents and dose rates, as well as the dependence of equivalent dose for various dose rates. The test performances are assessed in relation to use with heated quartz.     

A practical access to new pyrrolizine carboxylates via KHMDS-catalyzed carbocyclizations

Easy and effective preparation of new 1H-pyrrolizine carboxylates was achieved with high efficiency via KHMDS-induced carbocyclization of N-alkynyl proline carboxylates under substantially mild conditions. Meanwhile, some trans-diiodoallylic N-proline carboxylates were obtained from N-propargyl proline carboxylates using molecular I₂ with or without KHMDS. This method is quite feasible in terms of practical and quick access to the pyrrolizines and their derivatives over the formation of carbanions.     

On the validity of the giant spin approximation and its application to single-molecule magnets

A giant spin Hamiltonian is often used to describe the low temperature magnetic behavior in single-molecule magnets (SMMs). By addressing only the ground state multiplet, the Hilbert space is reduced significantly allowing for numerical simulation of a wide body of experimental data. Analysis of the [Ni(hmp)(dmb)Cl]₄ SMM using the giant spin model is compared to a four-ion model which addresses the local anisotropy associated with each of the magnetic Ni²⁺ ions, as well as the isotropic Heisenberg coupling between these ions. Higher-order giant spin Hamiltonian parameters that are absent in the individual ion parameterization appear when exchange coupling between the Ni²⁺ ions is introduced. Thus, a parameterization under the giant spin approximation is not purely a measure of anisotropic spin–orbit coupling, but instead a combination of interactions. Furthermore, the obtained parameters do not provide adequate insights into the physical processes within a SMM.     

A new route to the phosphindole system

A new and possibly general route to the hitherto relatively inaccessible simple substituted phosphindoles, utilizing the extreme readiness of simple phosphole sulfides to undergo Diels-Alder dimerization, is described. The synthesis reported here is that of 3,6-dimethyl-l-phenylphosphin-dole sulfide which is prepared in good yield in two simple steps from the readily available 3-methyl-l-phenylphosphole.     

A new and practical synthesis of pyrroles

Heating γ-nitroketoncs bearing an electron-withdrawing group such as an ester geminal to the nitro group with formamidinesulfinic acid and triethylamine in isopropanol produces pyrroles in good yield.     

On the validity of Langmuir adsorption on supported nanoparticles

The general form for adsorption on nanoparticles is presented. Conditions for the validity of Langmuir adsorption isotherm for supported nanoparticles are discussed.     

On the validity and applicability of the connected moments expansion

The theoretical justification, and typical convergence properties, of Cioslowski's connected moments expansion for the ground-state energy of a quantum-mechanical system are considered. This size extensive expansion is an alternative to Rayleigh-Schrodinger perturbation theory, and is expected to be useful in electronic structure calculations based on many-determinant reference functions, where perturbation theory is not applicable. It is found from example molecular electronic structure calculations that, in some cases, the expansion does not converge correctly to the true energy. An im- proved expansion derived from a padé approximant, and an analysis of its validity, is presented here.     

A new practical strategy for the synthesis of long-chain phosphopeptide

A new practical strategy has been developed for the synthesis of long-chain phosphopeptide. Both the 2-chlorobenzyloxycarbonyl (CIZ) group for Lys and methyl (Me) for phosphoamino acids remained intact, while other commonly used side-chain protecting groups were cleaved quantitatively, during the reaction using a highly acidic trifluoromethanesulfonic acid (TFMSA)-based reagent system (High TFMSA: TFMSA-TFA-m-cresol=1:9:1, v/v). Selective deprotection of the CIZ and Me group-containing protected phosphopeptide resin with the High TFMSA gave a partially protected phosphopeptide fragment suitable for thioester-mediated fragment condensation. A deprotection protocol of the 9-fluorenylmethyloxycarbonyl (Fmoc) group, which evades significant side reaction toward the protected phosphoamino acid, was also developed. These two new findings enabled us to synthesize long-chain phosphopeptide via thioester-mediated fragment condensation.