Search results for "Synthesi"
showing 10 items of 2904 documents
2015
Biphenols are important structure motifs for ligand systems in organic catalysis and are therefore included in the category of so-called "privileged ligands". We have developed a new synthetic pathway to construct these structures by the use of selenium dioxide, a stable, powerful, and commercially available oxidizer. Our new, and easy to perform protocol gives rise to biphenols and diaryl selenides depending on the solvent employed. Oxidative treatment of phenols in acetic acid yields the corresponding biphenols, whereas conversion in pyridine results in the preferred formation of diaryl selenides. As a consequence, we were able to isolate a broad scope of novel diaryl selenides, which cou…
Advances in photochemical and electrochemical incorporation of sulfur dioxide for the synthesis of value-added compounds.
2021
Organic photochemistry and electrochemistry currently receive tremendous attention in organic synthesis as both techniques enable the reagent-less activation of organic molecules without using expensive and hazardous redox reagents. The incorporation of SO2 into organic molecules is a relatively modern research topic, which likewise gains immense popularity since the discovery of the SO2 surrogate DABSO. Sulfur-containing organic molecules are omnipresent in pharmaceuticals and agrochemicals. This review covers the recent progress in electrochemical and photochemical methodologies for the incorporation and uses of SO2 in the synthesis of value-added compounds. Additionally, different work t…
Leaded Bronze: An Innovative Lead Substitute for Cathodic Electrosynthesis
2017
Acceptorless dehydrogenative condensation: synthesis of indoles and quinolines from diols and anilines.
2021
The use of diols and anilines as reagents for the preparation of indoles represents a challenge in organic synthesis. By means of acceptorless dehydrogenative condensation, heterocycles, such as indoles, can be obtained. Herein we present an experimental and theoretical study for this purpose employing heterogeneous catalysts Pt/Al2O3 and ZnO in combination with an acid catalyst (p-TSA) and NMP as solvent. Under our optimized conditions, the diol excess has been reduced down to 2 equivalents. This represents a major advance, and allows the use of other diols. 2,3-Butanediol or 1,2-cyclohexanediol has been employed affording 2,3-dimethyl indoles and tetrahydrocarbazoles. In addition, 1,3-pro…
Recent progress in the application of fluorinated chiral sulfinimine reagents
2018
Abstract The development of synthetic methodology allowing for a strategic incorporation of fluorine into target compounds is in a high demand in many areas of the chemical and pharmaceutical industries. In this regard, application of fluorinated chiral sulfinimine reagents, in particularly, N-tert-butylsulfinyl-3,3,3-trifluoroacetaldimine, is one of the most general and practical approaches for preparation of compounds containing pharmacophoric fluoro-amino-keto/hydroxy moieties. This article provides a timely and comprehensive overview of the recent synthetic applications of fluorinated chiral sulfinimine reagents for asymmetric synthesis of fluoro-containing polyfunctional amino-compound…
Synthesis of substituted piperidines by enantioselective desymmetrizing intramolecular aza-Michael reactions.
2018
An organocatalytic enantioselective intramolecular aza-Michael reaction has been described for the first time in a desymmetrization process employing substrates different from cyclohexadienones. By using 9-amino-9-deoxy-epi-hydroquinine as the catalyst and trifluoroacetic acid as a co-catalyst, a series of enantiomerically enriched 2,5-and 2,6-disubstituted piperidines have been obtained in good yields and with moderate diastereoselectivity. Depending on the catalyst/co-catalyst loading ratio, either the major or the minor diastereoisomer of the final piperidine products was achieved with high levels of enantioselectivity. Finally, some mechanistic insights have been considered by means of …
The history and future challenges associated with the hydrogenation of vinyl fluorides
2018
Abstract Catalytic hydrogenation is one of the most powerful transformations available in synthetic chemistry; there have been three Nobel Laureates rewarded for their work in the field. Despite the advances in substrate scope and the development of enantioselective versions of this transformation, vinyl fluorides remain somewhat underrepresented. Successful hydrogenation of vinyl fluorides can give rise to a fluorine-containing stereocenter, an important feature which has great potential in many areas of chemistry. This review aims to explore the history of vinyl fluorides as substrates in hydrogenation reactions, and to highlight modern day challenges and unresolved issues regarding this …
One-Pot Synthesis to Quinone-Based Diaza[3.3]cyclophanes
2017
A simple one-pot synthesis to [3.3]cyclophanes that involves quinone moieties was found. The protocol tolerates a variety of amines that include aliphatic and aromatic structures with different functional groups, such as hydroxy groups, amides, and terminal double and triple bonds. The straightforward synthesis can be performed by a twofold N-alkylation reaction with 2,5-bis(bromomethyl)-3,6-dimethyl-1,4-benzoquinone (1). Neither anhydrous nor inert conditions are required. Various amines can be employed without any activating groups, several functionalities at end groups are tolerated, and the cyclophanes generated can be easily modified or embedded into larger molecular architectures. The…
Organocatalytic enantioselective Strecker reaction with seven-membered cyclic imines
2018
[EN] A highly enantioselective Strecker reaction with dibenzo[b,f][1,4]oxazepines has been described using a dihydroquinine-derived thiourea as organocatalyst. The reaction affords chiral 10,11-dihydrodibenzo[b,f][1,4] oxazepine 11-carbonitrile derivatives in excellent yields (up to 99%) and excellent enantioselectivities (up to 98%) under mild reaction conditions.
Regioselective Metal- and Reagent-Free Arylation of Benzothiophenes by Dehydrogenative Electrosynthesis.
2018
A novel strategy for the synthesis of biaryls consisting of a benzothiophene and a phenol moiety is reported. These heterobiaryls are of utmost interest for pharmaceutical, biological, and high-performance optoelectronic applications. The metal- and reagent-free, electrosynthetic, and highly efficient method enables the generation of 2- and 3-(hydroxyphenyl)benzo[b]thiophenes in a regioselective fashion. The described one-step synthesis is easy to conduct, scalable, and inherently safe. The products are afforded in high yields of up to 88 % and with exquisite selectivity. The reaction also features a broad scope and tolerates a large variety of functional groups.