Conformational consequences of the dynamic processes in the stereolabile atropisomers of acyl-substituted m-terphenyl derivatives.

By means of low-temperature NMR spectroscopy, conformers (stereolabile atropisomers) due to the restricted rotation about the Ar-Ar and Ar-C(O)R bonds were detected in a number of acylphenyl derivatives, substituted in positions 2 and 6 by the 3-isopropylphenyl moiety (compounds 1-3, R=H, Me, and t-Bu, respectively). The conformational assignment was accomplished on the basis of the symmetry of the low-temperature 13C NMR spectra with the added support of ab initio calculations. The interconversion barriers were also determined by complete line shape simulation of the NMR spectra, and the experimental values were satisfactorily reproduced by ab initio calculations.

Unexpected stereodynamic consequences of the restricted rotations in ortho-acyl- and ortho-vinyl biphenyls.

Surprisingly, the aryl-aryl rotation barriers of biphenyl derivatives ortho-substituted by the "small" HC=O and HC=CH2 groups (10.0 and 8.4 kcal mol-1, respectively) were found greater than those observed in biphenyls ortho-substituted by the "large" t-BuC=O and t-BuC=CH2 groups (6.

Rotation in biphenyls with a single ortho-substituent.

Barriers to rotation in a range up to 15.4 kcal mol(-1) were determined by dynamic NMR spectroscopy for a series of biphenyl compounds 1a-1h and 2a-2d with a single ortho-substituent. Ab initio calculations reproduce these barriers satisfactorily and indicate the ground-state conformation of these molecules.

A general procedure for the synthesis of stereochemically pure conduritol derivatives practical also for solid-phase chemistry.

A straightforward synthetic protocol apt to synthesize a library constituted by all conduritol stereoisomers in solution phase is described and successfully applied to some polymer-supported substrates. During the solid-phase sequence, an unprecedented rearrangement of a resin-bound sulfone performed under the Ramberg-Bäcklund conditions appears of particular interest. Upon treatment with Me(3)Si-I, thiepanes supported on resin are found to undergo regio- and stereospecific ring contraction to a six-membered ring system with traceless cleavage from the solid support.

Static and dynamic stereochemistry of the conformational atropisomers of tetra(o-tolyl)benzene.

[graph: see text] Whereas only one atropisomer of 1,2,4,5-tetra(o-tolyl)benzene was observed by X-ray diffraction in the solid, five conformational atropisomers were detected by low-temperature NMR in solution. Their structures were assigned by a combination of NOE experiments, solvent effect, and ab initio calculations. Variable temperature dynamic NMR and bidimensional EXSY experiments allowed the barrier for the interconversion of these atropisomers to be determined (deltaG(double dagger) = 15.

Structure, conformation, and dynamic processes of the stereolabile atropisomers of hindered terphenyl hydrocarbons.

[reaction: see text] Ortho-substituted p-terphenyl hydrocarbons exist as trans and cis atropisomers that were identified by low-temperature NMR spectroscopy. The interconversion barriers increase with the dimensions of the ortho substituents, the experimental values being matched by ab initio calculations. X-ray diffraction shows that only the trans atropisomer is present in the solids.

Stereomutations of two-bladed propeller derivatives: ortho-substituted diaryl ethylene and diaryl ketone.

Stereochemical analysis, supported by ab initio computations, predicts the existence of three possible stable helical conformers for o,o'-diisopropyl-1,1'-diphenylethylene (1) and o,o'-diisopropylbenzophenone (2). At low temperature the NMR spectra of 1 showed distinct sets of signals for these conformers, thus allowing the measurement of the three barriers involved in the related stereomutation processes to be obtained (DeltaG=6.45, 4.

[Tools and procedures for research in psychiatric nursing. III - Nursing personnels activities list and perceptions of their functions test].

Two instruments for investigation about psychiatric intervention are presented. One is about the attitude of nursing personnel towards the patient and the care he should receive. The other is described in a study armed at finding how this personnel see the nursing functions they performs.

[Tool and procedures for research in psychiatric nursing. II - Inventory of possible situations in psychiatric nursing].

The author lists situations in which psychiatric patients' basic needs are affected and possible activities of the nursing personnel to meet them.

[Tool and procedures for research in psychiatric nursing. I - Classification of the activities performed by nursing personnel].

This is a study of the activities of nursing personnel in psychiatric hospitals, in which the observation method was employed.

[Some aspects of teaching-service integration].

This article analyzes the situation of the nursing educator and the three roles she should carry out: teaching, nursing service and research. Besides these roles are those she should carry out as human being in a social context. The internal and external motivation and the conflicts and feelings that cause an educator to avoid carrying out some of these roles are analyzed.