Synlett

Synlett 2024; 35: A22-A35DOI: 10.1055/s-0040-1720622Georg Thieme Verlag KG Rüdigerstraße 14, 70469 Stuttgart, GermanyArticle in Thieme eJournals:Table of contents

Synlett 2024; 35: III-IIIDOI: 10.1055/s-0043-1763677Georg Thieme Verlag KG Rüdigerstraße 14, 70469 Stuttgart, GermanyArticle in Thieme eJournals:Table of contents

A metallaphotoredox-catalyzed synthesis of heterodiarylmethanes using mild reaction conditions, commercially available substrates, and bench-stable catalysts is demonstrated. Moderate yields are obtained, and further derivatization of the newly formed benzylic position is shown.

The selective functionalization of 1,3-bis(boronic) esters holds the potential for creating diverse molecular structures, particularly through the late-stage functionalization of the remaining C–B bond. By employing distinct organometallic reagents, we have developed a method for regiodivergent alkynylation of 1,3-bis(boronic) esters, facilitated by unique chelation patterns. Notably, this methodology effectively overcomes limitations commonly encountered in radical chemistry, which generates only monoselective downstream targets. Furthermore, the compounds synthesized through this approach can serve as significant building blocks, contributing to the construction of molecular complexity.

Factors that might affect the removal time of high-boiling-point solvents with a rotary evaporator were examined. Considering several essential factors, the optimized conditions for removing a high-boiling-point solvent are suggested. The results and discussion from this work can serve as a reference for current and future organic chemists. Finally, two examples of fast and successful dehydration reactions are given to demonstrate that the rotary evaporator can be used to conduct organic syntheses.

We report the development of a straightforward, waste-reducing, environmentally friendly, FeIII-catalyzed domino aza-Michael/aldol/aromatization reaction in the presence of water to access high-value functionalized quinolines by using 2-aminobenzophenones and ethyl buta-2,3-dienoate as starting compounds. The tangible advantages, that is, the utilization of commercially available and/or easily accessible substrates, simplicity, mild reaction conditions, and application of water as a solvent, make this three-step domino process green and highly appealing for the direct construction of a wide variety of highly functionalized quinolines in up to 78% yield.

We present a condensation of primary aryl or alkyl amines with S-methyl thiouronium salts to obtain N,N,N′-trisubstituted amidines. High yields, short reaction times, and a fair substrate scope are the noteworthy features of this protocol. Surprisingly, the reaction of a thiouronium salt with 4-aminopyridine gave 1-(4-methoxybenzoyl)piperidine.

All living things use DNA and RNA to store, retrieve, and transmit their genetic information. The complementary Watson–Crick nucleobase-pairs (A/T and G/C base-pairs), have been documented for years as being essential for the integrity of the DNA double helix and also for replication and transcription. With only four poorly fluorescent naturally occurring nucleic acid bases (namely A, G, T/U, and C), the extraction of genetic information is difficult. Further, the chemical diversity of DNA and RNA is severely limited. Deoxyribose/ribose-phosphate backbones also constrain DNA and RNA characteristics and have poor chemical and physiological stability, which significantly restricts the practical applications of DNA and RNA. Over the years, extensively modified nucleobase pairs with novel base-pairing properties have been synthesized. Such designer nucleobases, serving as an expanded genetic alphabet, have been used for the design and synthesis of DNA and RNA analogues with tailored informational/functional properties. Recent developments in the production of synthetic unnatural base pairs pave the way for xenobiology research and genetic alphabet expansion technology. In this review, we present a brief history of the development of several hydrogen- and non-hydrogen-bonded unnatural base pairs and their applications. We also highlight our work in designing and synthesizing a new class of triazolyl unnatural nucleosides that offer a unique charge-transfer (CT) complexation force towards stabilizing DNA-duplexes when incorporated into short oligonucleotide sequences.

The present article provides a personalized account on CH-arylation reactions employed for the synthesis of heterocycles. The presence of a nitro group allowed for direct and regioselective CH-arylations of pyrazoles, imidazoles, indoles and a variety of purine analogues. Direct CH-arylations without the presence of an activating nitro-group were employed for inter- and intramolecular reactions of purine derivatives, which allowed for the synthesis of a great variety of polycyclic systems. Domino C–N coupling / hydroamination / CH-activation reactions of diarylacetylenes with anilines allowed for the synthesis of polycondensated N-heterocycles. Products include indolo- and azaindolo[1,2-f]phenanthridines, quinolino[3′,4′:4,5]pyrrolo[1,2-f]phenanthridines, pyrimido[5′,4′:4,5]pyrrolo[1,2-f]phenanthridines, and benzothieno[2′,3′:4,5]pyrrolo[1,2-f]phenanthridines. The reaction of N-heterocycles, such as indoles, with 1,1-difluoroalkenes resulted in a twofold addition-elimination reaction to give 1,1-diaminoalkenes, which were transformed by CH-arylation into various polycondensated heterocycles, such as indoloisoquinolines, thienoindolizines, oxepines and helicenes. Pyridofluoranthenes, diindenopyrene and azadiindenopyrenes were prepared by a combination of Pd-catalyzed cross-coupling reactions with acid-mediated cycloisomerizations and Pd-catalyzed intramolecular CH-arylations. Bis(carbazoles), benzodithiazoles, benzodithiophenes and 2,5-diarylpyrroles were prepared by inter- and intramolecular CH-arylation reactions.

This Account presents palladium-complex-catalyzed oxidative couplings mainly developed by the author’s group, including oxidative amination and silylation of terminal alkenes, direct oxidative arylation of aromatic compounds, and oxidative difunctionalization of 1,3-dienes. The catalytic cycles in these representative reactions feature re-oxidation of the palladium species with molecular oxygen as the terminal oxidant. Varying the combination of palladium catalyst and re-oxidant enables the formation of a variety of bonds through dehydrogenative cross-coupling reactions.1 Introduction2 Oxidative Amination of Terminal Alkenes3 Direct Oxidative Arylation of Aromatic Compounds4 Oxidative Silylation of Terminal Alkenes5 Oxidative Difunctionalization of 1,3-Dienes6 Conclusions and Perspectives