Synlett

The conventional synthesis of glycosyl chlorides from thioglycosides relies on sequential oxidation and chlorination. A one-pot synthesis of glycosyl chlorides is warranted as an alternative method. Here, we report a one-pot synthesis of glycosyl chlorides from thioglycoside precursors. The transformation was mediated at low temperatures by bromodiethylsulfonium bromopentachloroantimonate (BDSB) as a mild oxidant with Bu4NCl as an additive. Armed thioglycosides afforded the corresponding α-glycosyl chlorides in moderate to good yields under the optimized conditions. Low conversions and yields were obtained when the less-reactive disarmed thioglycosides were used. Unexpectedly, BDSB-mediated oxidation of thioglycosides without the addition of Bu4NCl also afforded the α-glycosyl chlorides in moderate yields. We suggest a mechanism involving the transfer of chloride ions from the nonnucleophilic bromopentachloroantimonate (SbCl5Br) anion to the oxocarbenium ion.

A convenient and practical method for the synthesis of unsymmetrical triarylmethanes was demonstrated through a one-pot three-component double Friedel–Crafts reaction of various aliphatic, aromatic, or heteroaromatic aldehydes with N,N-dialkylanilines and indoles by using a Brønsted acidic ionic liquid as the catalyst. This method was successfully applied under metal- and solvent-free conditions at 80 °C, affording the corresponding unsymmetrical triarylmethane products in moderate to high yields from a broad range of substrates. In addition, the mechanism of this reaction was studied by quantitative NMR analysis.

The Aristotelia alkaloids are a family of monoterpene indole alkaloids possessing a characteristic azabicyclononane scaffold, which has been assembled by several synthetic methods. Herein we review those approaches that have adopted a biomimetic approach to unite heterocyclic synthons with chiral-pool monoterpenes. Throughout this discussion, the tendency of monoterpenes like α-pinene and limonene to undergo racemization is highlighted, revealing the challenges in developing stereospecific syntheses of these alkaloids. Finally, we provide a brief discussion of how these synthetic efforts have enabled the structural confirmation and elucidation of the Aristotelia alkaloids’ absolute configurations, including our own recent efforts to employ bioactivity data to deduce the naturally occurring configuration of the quinoline alkaloid aristoquinoline.1 Introduction2 Mercury-Mediated Ritter-Like Reactions3 Brønsted Acid Mediated Ritter-Like Reactions4 Synthesis of Aristoquinoline: Ritter-Like Reaction Approach5 Aza-Prins-Type Reaction in the Synthesis of Aristotelia Alkaloids6 Determination of Naturally Occurring Absolute Stereochemistry7 Conclusions

A 2-iodoxybenzoic acid (IBX)–dimethyl sulfoxide (IBX-DMSO)-promoted oxidative aromatization of spiro[2.5]octa-4,7-dien-6-ones has been developed. A series of substrates with various substitutions were transformed into oxidative aromatization products in good to excellent yields. This oxidative aromatization features environmentally friendly reagents, high efficiency, a broad substrate scope, broad functional-group tolerance, and mild reaction conditions.

The construction of the successive stereogenic centers, including an all-carbon quaternary stereogenic center, of ent-kauranoid through an oxidative dearomatization/1,2-shift cascade is described. The developed cascade reaction of a substrate bearing a trans-2-(p-methoxyphenyl)vinyl group as the migrating group afforded the desired product in 83% yield. The 1,2-shift in the cascade is strongly affected by a stereoelectronic effect. The X-ray crystal structure of a compound bearing four successive stereogenic centers in the fused-ring moiety of ent-kauranoid diterpene, which was prepared by the oxidative dearomatization/1,2-shift cascade and subsequent stereoselective transformations, is also reported.

The N-oxidation of tertiary amines was achieved by using electrochemically generated peroxodicarbonate solutions as sustainable oxidizers. The presence of EDTA and 2,2,2-trifluoroacetophenone as a mediator was found to be crucial for converting water-insoluble substrates. Various tertiary amines were converted into their corresponding N-oxides in yields of up to 98%. The scope includes economically important surfactants and potential platform oxidizers.

Triarylmethane derivatives and their corresponding trityl carbocations are among the oldest chemical species synthesized and studied by chemists. The carbocationic platforms are particularly interesting due to their stability, high extinction coefficient, and tunable absorption of light in the visible spectrum, which can be achieved through structural modifications. These stable cations are traditionally obtained through heterolytic cleavage of judiciously designed, parent triarylmethanes by exposure to acids or UV light (λ < 300 nm), and methods based on electrochemistry or radiolysis. Our group has recently discovered that trityl carbocations can be generated also via mechanical stimulation of solid polymer materials featuring triarylmethane units as covalent crosslinks. In this Synpacts contribution, we expand on our previous finding by discussing some intriguing research questions that we aim to tackle in the immediate future.1 Introduction2 The Development of Our First Triarylmethane Mechanophore3 The Potential Reversibility of Triarylmethane Mechanophores4 A General Molecular Platform for Force-Induced, Scissile, Homolytic and Heterolytic Bond Cleavage?5 Conclusion

Synlett 2022; 33: A101-A117DOI: 10.1055/s-0040-1720564Georg Thieme Verlag KG Rüdigerstraße 14, 70469 Stuttgart, GermanyArticle in Thieme eJournals:Table of contents

Synlett 2022; 33: V-DOI: 10.1055/s-0041-1737721Georg Thieme Verlag KG Rüdigerstraße 14, 70469 Stuttgart, GermanyArticle in Thieme eJournals:Table of contents

Fluorinated heterocyclic compounds have been proven to exhibit interesting potential biological activities. Therefore, various fluorinated 2-benzylphthalazine-1(2H)-one and phthalazine-1-amine derivatives and nonfluorinated 1-alkoxy/benzyloxyphthalazines derivatives have been synthesized by an ultrasonication method. This protocol is more efficient than the conventional method in terms of its product yield and reaction handling and timelines.