Intramolecular inverse electron-demand [4+2] cycloadditions of ynamidyl-tethered pyrimidines: Comparative studies in trifluorotoluene and sulfolane

International audienceThree representative 6,7-dihydro-5H-cyclopenta[b]pyridin-4-amines were synthesized using an intramolecular inverse electron demand heteroeDielseAlder/retroeDielseAlder sequence between pyrimidines (acting as azadienes) and ynamides (acting as dienophiles). Two solvents of this reaction, sulfolane and trifluorotoluene, were compared at 210 C and the former consistently led to higher yields. In addition, these studies confirmed the importance of the steric bulk of the C5-position of the pyrimidinyl cycloaddition precursor

Strategies de linearisation lors de descriptions textuelles de configurations spatiales

Projet PSYCHO ERGOA la suite de travaux sur la linearisation dans des descriptions orales de configurations spatiales, la presente recherche porte sur de telles descriptions mais a l'ecrit. Les figures de Levelt sont utilisees. Il s'agit de figures composees de cercles colores interconnectes par des segments horizontaux ou verticaux. Des sujets (n=39) ont ete invites a decrire par ecrit 16 figures de 4 types differents, de telle sorte que la description permette a une autre personne de les reproduire. Levelt expliquait l'ensemble de ses resultats par une seule strategie de description, le "circuit" sorte de parcours au regard de la figure qui respecte au plus pres la connexite entre les elements. Cette strategie est retrouvee ici, mais beaucoup moins frequente que chez Levelt. D'autres strategies sont mises en evidence : en particulier, une representation hierarchique qui decompose la figure en sous-partie avant de decrire celles-ci au niveau de leurs elements. On trouve egalement une strategie de quadrillage (sorte de matrice i*j appliquee sur la figure comme dans les mots croises) L'hypothese que le facteur mode d'expression (oral/ecrit) pourrait expliquer ces resultats tres differents est rejetee grace a une nouvelle experience (Montarnal, 93). En conclusion, d'autres hypotheses sont envisagees : une possible difference de consigne ainsi qu'un effet suppose du niveau culturel des sujets. Enfin du point de vue de theorique on insiste sur le caractere primordial d'une representation hierarchique des images chez le sujet humain

Inverse Electron-Demand [4 + 2]-Cycloadditions of Ynamides: Access to Novel Pyridine Scaffolds

Functionalized polycyclic aminopyridines are central to the chemical sciences, but their syntheses are still hampered by a number of shortcomings. These nitrogenated heterocycles can be efficiently prepared by an intramolecular inverse electron demand hetero Diels–Alder ( ih DA) cycloaddition of ynamides to pyrimidines. This ihDA/rDA sequence is general in scope and affords expedient access to novel types of aminopyridinyl scaffolds that hold great promise in terms of exit vector patterns

Design: One, but in different forms

This overview paper defends an augmented cognitively oriented generic-design hypothesis: there are both significant similarities between the design activities implemented in different situations and crucial differences between these and other cognitive activities; yet, characteristics of a design situation (related to the design process, the designers, and the artefact) introduce specificities in the corresponding cognitive activities and structures that are used, and in the resulting designs. We thus augment the classical generic-design hypothesis with that of different forms of designing. We review the data available in the cognitive design research literature and propose a series of candidates underlying such forms of design, outlining a number of directions requiring further elaboration