Search results for "craft"

1975

In the polymerization of isobutene catalyzed by aluminium tribromide and in the polymerization of styrene catalyzed by trifluoromethanesulphonic acid it is supposed that an inactive catalyst monomer complex is formed which is in equilibrium with other active species. The monomer complexation of the catalyst explains the S-shaped conversion curves and the complex kinetics of the polymerization. The value of the equilibrium constant Km (complexation constant) expresses what part of the catalyst may take part in the polymerization process as an active initiating species. For the system isobutene/AlBr3, Km was found to be 0,62 1/mol. In the system styrene/CF3SO3H, the high value of the complexa…

Organocatalytic enantioselective aza-Friedel–Crafts reaction of 2-naphthols with benzoxathiazine 2,2-dioxides

2015

An organocatalytic enantioselective aza-Friedel–Crafts addition of 2-naphthols to benzoxathiazine 2,2-dioxides is described using a quinine-derived bifunctional catalyst. The method allows the use of a wide range of aromatic compounds as nucleophiles, including 1-naphthol and sesamol, and benzoxathiazines 2,2-dioxides, expanding the existing state of the art enantioselective synthesis of aminomethylnaphthol derivatives.

ChemInform Abstract: Organocatalytic Enantioselective Aza-Friedel-Crafts Reaction of 2-Naphthols with Benzoxathiazine 2,2-Dioxides.

2015

An organocatalytic enantioselective aza-Friedel–Crafts addition of 2-naphthols to benzoxathiazine 2,2-dioxides is described using a quinine-derived bifunctional catalyst. The method allows the use of a wide range of aromatic compounds as nucleophiles, including 1-naphthol and sesamol, and benzoxathiazines 2,2-dioxides, expanding the existing state of the art enantioselective synthesis of aminomethylnaphthol derivatives.

ChemInform Abstract: Catalytic Enantioselective Friedel-Crafts Reactions of Naphthols and Electron-Rich Phenols

2016

The enantioselective Friedel–Crafts reaction is a powerful tool for the construction of benzylic stereocenters in a stereodefined manner. Significant advances have already been achieved with heteroarenes such as indoles and pyrroles; however, the reaction with homoarenes is less developed. This short review covers the most relevant literature on enantioselective Friedel–Crafts reactions with naphthols and phenols. 1 Introduction 2 Friedel–Crafts Reactions Involving 1,2-Nucleophilic Addition to C=X Bonds 3 Friedel–Crafts Reactions Involving Conjugate Nucleophilic Addition to Electrophilic C=C Bonds 4 Friedel–Crafts Reactions Involving π-Allylic Complexes as Electrophiles 5 ipso-Friedel–Craft…

ChemInform Abstract: Enantioselective Zirconium-Catalyzed Friedel-Crafts Alkylation of Pyrrole with Trifluoromethyl Ketones.

2009

The first catalytic enantioselective Friedel−Crafts alkylation of pyrrole with 2,2,2-trifluoroacetophenones to give pyrroles with a trifluoromethyl-substituted tertiary alcohol moiety bearing a quaternary stereogenic center is described. The reaction is achieved in the presence of a 3,3′-dibromo-BINOL-Zr(IV) complex to give the expected products with high yields (up to 98%) and good enantioselectivities (up to 93% ee). The absolute stereochemistry of the products has been determined by chemical correlation.

Dimethoxy Aromatic Compounds. VIII. Degenerate Dealkylation-Realkylation Reaction of 1-Bis(2,4-dimethoxyphenyl)-2-methylpropane.

1994

The condensation reaction under acid condition of the benzylic alcohols 1, 2 and 3 with the hexadeutero dimethoxybenzenes 4, 5 and 6 leads to the expected hexadeutero bis(dimethoxyphenyl)-2-methylpropanes 7, 8 and 9, respectively. However, the presence of both dodecadeutero and unlabelled 1-bis(2, 4-dimethoxyphenyl)-2-methylpropanes 10 and 11 indicates that 9 undergoes a rapid degenerate dealkylation-alkylation reaction.

Construction Guilds in Southern Italy and the Islands (15th-16th Centuries): Leadership and Rivalries

2020

In the South of Italy and the big islands, in counter-trend with respect to the rest of the peninsula, construction guilds know a renewed vitality between the last decades of 15th and the beginning of 16th centuries. Rules, prerogatives and operative modes are regulated by statutes, often undersigned by the masters included in the trade organization, mentioning also the other actors involved in the approval processes. The intertwining of these and other archival documents sometimes reveals the leading role played within the guild by masters that overcome the anonymity usually considered to be inherent in the corporate system. Comparing the rules and the boundaries among specific trades esta…

Playful Hands-on Crafting for Personal Growth and Communal Well-being

2017

Crafts education in Finland has recently been exposed to considerable challenges, on both the theoretical and practical levels. The emphasis is shifting to personal expression and communal arts and crafts practices are being adapted to solidify social and cultural participation. Learning research shows us how inner motivation and multilevel objectives in comfortable learning environments induce stable and generalizable learning results. In addition, collaborative ways of working make data processing more open and turn learning into a shared effort. On the other hand, playful learning and dramatic methods offer productive ways of examining life situations in an active and empathetic way. Whe…

Production et commerce, quelques aspects dans le nord de la Gaule romaine (Ier-IIIe siècle de notre ère)

2023

L’étude de l’économie de la Gaule romaine par les archéologues a traditionnellement privilégié l’analyse des lieux de production agricole et artisanale, ainsi que la diffusion des produits manufacturés. La large diffusion de produits à l’échelle du bassin méditerranéen et jusque dans les provinces septentrionales de l’Empire, voire en dehors, suggère une économie ouverte aux échanges à longue distance. Les recherches montrent cependant que la diffusion n’atteint jamais la totalité de l’Empire, voire du Bassin méditerranéen, si ce n’est de manière marginale. Par ailleurs, à l’écart des rivages de la Méditerranée, l’examen des mobiliers provenant de sites d’habitat conduit à nuancer la place …

Functional interpretative approaches on shears at the end of the Iron Age and the beginning of the Roman Principate. The example of shears in the cem…

2011

Scheren werden häufig als multifunktionale Geräte aufgefasst, deren genauere Bestimmung schwer einzugrenzen ist. Jedoch geben deren Form und technische Eigenschaften über die vorgesehene Verwendung Aufschluss. Es ist also möglich, eine neue Gliederung dieser Objekte vorzunehmen, und zwar anhand der Funktion, die sie am besten zu erfüllen scheinen. Diese Einteilung der Scheren aus den Nekropolen der Treverer wird durch die jeweils begleitenden anderen Grabbeigaben verifiziert. Das Beispiel der Scheren aus den Gräbern der Treverer macht es zudem möglich, diese Stücke anhand der sonstigen Beigaben einerseits in die Technikgeschichte und andererseits in die Sozialgeschichte einzuordnen.