Synlett

Electrosynthesis is undergoing a renaissance, but it is still far from being considered a standard method within the chemists’ synthetic toolbox. In this article, we will demystify organic electrochemistry by reviewing some practical methodologies developed in our laboratory to prepare highly reactive synthetic intermediates.1 Introduction2 Acyloxy Radicals3 Orthoesters4 Isocyanates5 Isocyanides6 Diazo Compounds7 Conclusion

Synlett 2022; 33: A118-A132DOI: 10.1055/s-0040-1720568Georg Thieme Verlag KG Rüdigerstraße 14, 70469 Stuttgart, GermanyArticle in Thieme eJournals:Table of contents

Synlett 2022; 33: V-DOI: 10.1055/s-0041-1738671Georg Thieme Verlag KG Rüdigerstraße 14, 70469 Stuttgart, GermanyArticle in Thieme eJournals:Table of contents

A direct metal- and oxidant-free photochemical decarboxylative formylation of indoles with 50% aqueous glyoxylic acid proceeds in good to moderate yields.

The photoirradiation of toluene derivatives with two equivalents of bromine in benzotrifluoride–water provided a satisfactory yield of the corresponding benzoic acid derivatives. Either a fluorescent lamp, blue LED (454 nm), or UV LED (385 nm) was used for the photoreaction. The reaction pathway might proceed through the dibromination of benzylic carbon, generation of the benzylic radical via oxidative C–H abstraction, formation of benzoyl bromide, and hydrolysis of carboxylic acid.

Various indole-containing compounds have shown impressive pharmaceutical activities against a variety of diseases. However, the functionalization of indoles usually relies on systems that use organic solvents, which do not meet the criteria for green and sustainable chemical development. To address this issue, regiospecific sulfenylation, selenylation, and telluration of indoles were developed using H2O as solvent. The highly efficient chalcogenylation of indoles was achieved utilizing CsOH as a promoter, thus avoiding the use of expensive transition-metal catalysts. This newly developed protocol is characterized by its outstanding features including simple operation, mild conditions, wide substrate scope, excellent functional group tolerance, and recyclability, leading to the convenient synthesis of 3-chalcogenyl-indoles.

A process for the synthesis of P-chiral triarylphosphine sulfides via sequential Pd-catalyzed stereospecific P–C coupling reactions of P-chiral precursors prepared by enzymatic desymmetrization was developed. Three independent aryl substituents could be introduced onto the P atom by the sequential P–C couplings under mild conditions while retaining the high enantiopurity.

As one of the most important indispensable tools, organozinc-reagents-based Negishi cross-couplings have been extensively utilized for the synthesis of biologically active molecules and feedstock commodity chemicals. However, the use of air- and moisture-sensitive organozinc halides and expensive palladium catalysis still remain drawbacks. Recently, user-friendly solid OPiv-supported C–Zn, Si–Zn reagents with enhanced air and moisture stability have been prepared, which displayed superior reactivity in various transition-metal-catalyzed cross-couplings, especially in the earth-abundance cobalt and nickel catalysis. Herein, we summarized the recent advances and our research work in the field of the preparation and application of solid organozinc pivalates in the present short review.1 Introduction2 Development of Organozinc Pivalates in Two-Component Cross-Couplings3 Development of Organozinc Pivalates in Three-Component Cross-Couplings4 Conclusion and Outlook

A novel, metal-free bromo-thiolation of internal alkynes with hydrobromic acid and disulfides has been developed. The reaction is promoted by commercial-grade nitric acid and is used to construct a series of unexplored β-bromoalkenyl sulfides in moderate to good yield. Most products were obtained with high stereoselectivity as syn-configured tetrasubstituted alkenes. Both sulfide groups of the disulfide reagent were used in this method.

A mild synthesis of 3,5-disubstituted nitrobenzenes from readily available 3-formylchromones is reported. The developed methodology follows a cascade process, promoted by 1,8-diazabicyclo[5.4.0]undec-7-ene. The proposed mechanism involves an initial Michael addition of nitromethane at C-2 of a 3-formylchromone. The resultant intermediate undergoes another Michael reaction with a second 3-formylchromone molecule. After ring closure through intramolecular cyclization, the aromatization is completed by deformylation, affording the 3,5-disubstituted nitrobenzenes in 52–86% yield. The reported method produces three new C–C bonds in a simple and straightforward manner, and it is consistent with gram-scale synthesis.