Sandra Hübner

Green and Efficient Synthesis of Sulfonamides Catalyzed by Nano-Ru/Fe3O4

The environmentally benign synthesis of carbon-nitrogen bonds continues to be an active and challenging field of chemical research. Here, a novel, environmentally benign method for the direct coupling of sulfonamides and alcohols is described. Despite the importance of sulfonamide derivatives as intermediates in drug synthesis, till now such transformations are rarely known. For the first time a domino dehydrogenation-condensation-hydrogenation sequence of alcohols and sulfonamides has been realized in the presence of a nanostructured catalyst. The magnetic property of the catalyst system allows for convenient isolation of the product and efficient recycling of the catalyst. A variety of coupling reactions of benzylic alcohols and sulfonamides including various heterocycles were successfully realized, often with >80% isolated yield. Advantageously, only one equivalent of the primary alcohol is consumed in the process. Mechanistic investigations of the competitive reactions of benzyl alcohol and d(7)-benzyl alcohol with p-toluenesulfonamide revealed a kinetic isotope effect (k(H)/k(D)) of 2.86 (+/-0.109) for the dehydrogenation of benzyl alcohol and 0.74 (+/-0.021) for the hydrogenation of N-benzylidene-p-toluenesulfonamide intermediate, which suggests dehydrogenation of the alcohol to be the rate determining step.

Synthesis and antimicrobial activity of N-analogous corollosporines

Corollosporine is an antimicrobial metabolite, which was isolated from the marine fungus Corollospora maritima. Owing to its basic 4-hydroxyphthalic acid anhydride structure, it has become an attractive target for a structure/activity relationship modelling of derived compounds with potential antibiotic activity. In this regard we report on the straightforward synthesis of hetero analogous corollosporines, which were easily prepared by a three-step reaction sequence, taking advantage of a novel multicomponent reaction (AAD-reaction) and a subsequent aromatization/Grignard reaction protocol. Furthermore, the obtained products were tested in several biological assays to evaluate their antimicrobial activity.

From a spin-off to the advantageous use in Diels–Alder reactions: a combined synthetic, spectroscopic and computational approach to N-(dienyl)acylamines

The acid-catalyzed condensation of aldehydes and acetamide has been shown to provide a pool of diverse equilibrating species. For the first time, the synthesis of substituted 1-N-acylamino-1,3-butadienes has been accomplished directly in moderate yields upon telomerization of two molecules of aldehyde with one molecule of carboxamide. Detailed spectroscopic and computational investigations establish the favourable formation of all-trans aminodienes under the reaction conditions. Employment thereof as diene building blocks in Diels-Alder reactions allows for the synthesis of carbocyclic molecules with high stereocontrol.

On the selective aerobic oxidation of benzyl alcohol with Pd/Au-nanoparticles in batch and flow

Abstract Nanoparticles (NP) have specific catalytic properties, which are influenced by parameters like their size, shape, or composition. Bimetallic NPs, composed of two metal elements can show an improved catalytic activity compared to the monometallic NPs. We, herein, report on the selective aerobic oxidation of benzyl alcohol catalyzed by unsupported Pd/Au and Pd NPs at atmospheric pressure. NPs of varying compositions were synthesized and characterized by UV/Vis spectroscopy, transmission electron microscopy (TEM), and small-angle X-ray scattering (SAXS). The NPs were tested in the model reaction regarding their catalytic activity, stability, and recyclability in batch and continuous procedure. Additionally, in situ extended X-ray absorption fine structure (EXAFS) measurements were performed in order to get insight in the process during NP catalysis.

A New Efficient Synthesis of Substituted Luminols Using Multicomponent Reactions

Abstract A new general synthesis of substituted luminols (5-amino-2,3-dihydrophthalazine-1,4-diones) is presented. Diversely substituted luminol derivatives can be synthesized in three steps. The products are of interest as new materials, which exhibit chemiluminescence.