The cyclodimerisation of 3-methyl-2-butenenitrile

3-Methyl-2-butenenitrile (1) cyclodimerised on treatment with lithium diisopropylamide in dimethoxyethane at temperatures between ?78°C and 0°C to 3-amino-4-cyano-1,5,5-trimethyl-1,3-cyclohexadiene (2) the structure of which was established by acid hydrolysis to the known 4-cyano-1,5,5-trimethyl-1-cyclohexene-3-one (3).     

Asymmetric hydrogenation of aromatic olefins catalyzed by iridium complexes of proline derived phosphine-oxazoline ligands

The synthesis of a series of phosphine-oxazoline ligands is reported. This ligands are synthesized by reaction of a phosphine chloride with the secondary nitrogen of proline. Upon coordination to iridium the resulting complexes can be used in the asymmetric hydrogenation of simple olefins. The effect of different counter ions and substitution at the oxazoline and the phosphine is reported.     

Synthesis, characterization, and isomerization of an iridabenzvalene

Metal- halogen exchange of vinylcyclopropene 4 followed by addition of [(Me3P)2Ir(CO)Cl] produced iridabenzvalene 5. The metallabenzene valence isomer was characterized by NMR and IR spectroscopy and by X-ray crystallography. Isomerization of complex 5 to iridabenzene derivatives 6 and 13 was accomplished by thermolysis and by Ag+ ions, respectively. The former transformation was a clean and quantitative process that displayed first-order kinetics.     

Effect of decision weights and internal noise on the growth of d' with N

A general finding of psychoacoustic studies is that detectability d' of a noisy signal grows less than optimally with the number N of independent observations of the signal. Competing accounts implicate internal noise common to all observations or nonoptimal decision weights given to observations. A discriminant analysis of listeners' trial-by-trial responses in a multitone level-discrimination task favored the latter account.     

Conical parametric scattering of a single extraordinary beam in BaTiO3 crystal

In this paper, the parametric scattering of a single extraordinary polarized beam of laser in BaTiO₃ photorefractive crystal has been investigated experimentally and theoretically. The resulting pattern consists of beam fanning, isotropic ring, and anisotropic one. Among all parts of scattering pattern, isotropic ring has not been studied as much as beam fanning and anisotropic ring, and there still are some differences in reports about it. Therefore, the study has mainly focused on this part. In this experimental configuration, isotropic ring is just visible in positive angles although the other parts of parametric scattering pattern can be visible from behind and in front of the crystal. In addition to steady state pattern in forward and backward directions, its transient behavior with the rotation of crystal has been studied. The results of experiments have been analyzed carefully, and their theoretical explanations have been presented based on the standard theory of parametric scattering in photorefractive crystals. It has been shown that this configuration corresponds to the so called parametric B-process scattering.     

Preparation of a library of unsymmetrical ureas based on 8-azabicyclo[3.2.1]octane scaffold

This paper reports the preparation of a library of unsymmetrical ureas based on 8-azabicyclo[3.2.1]octane scaffold. The reported synthetic route uses nortropane-8-carbonyl chlorides as key intermediates that, when treated with a slight excess of amine, give the corresponding ureas in high yield (129 examples).     

A detection-theoretic framework for modeling informational masking

There has been growing interest in recent years in masking that appears to have its origin at a central level of the auditory nervous system-so-called informational masking (IM). Masker uncertainty and target-masker similarity have been identified as the two major factors affecting IM; however, no theoretical framework currently exists that would give precise meaning to these terms necessary to evaluate their relative importance or model their effects. The present paper offers a first attempt at such a framework constructed within the doctrines of the theory of signal detection.     

An unusually robust triple bond: synthesis, structure and reactivity of 3-alkynylcyclopropenes

Several 1,2-diphenyl- and 1,2,3-triphenyl-3-alkynylcyclopropenes have been prepared in moderate to very good yields by the reaction of acetylenic nucleophiles with the appropriate cyclopropenylium salt. Single crystal X-ray structures of four of the cyclopropenes were obtained. Stereoselective reduction of the triple bond failed in all cases, whereas model compounds lacking the cyclopropene moiety were reduced successfully. A rational for this lack of reactivity is proposed. The solution-phase thermochemistry of the 3-alkynyl-1,2,3-triphenylcyclopropenes was explored, affording 3-alkynyl-1H-indenes in moderate to good yields.