Synlett

An efficient and practical method for the bromination of electron-rich arenes and heteroarenes was developed by using S-methyl methanethiosulfonate as the oxidant. All the bromine atoms were basically transferred to the brominated products, demonstrating the exceptional atom economy and practicality of the proposed protocol. The method reduces the amount of bromine required for this reaction system and obtains products in moderate to good yields.

A tripeptide catalyst derived from natural l-amino acids was employed in the reaction of β-nitrostyrenes with cyclohexanone, serving as a model for the asymmetric Michael addition reaction. The reaction was conducted in the presence of H-Pro-Tle-Gly-OH and 2-fluoro-4-chlorobenzoic acid as co-catalysts (each at 20 mol%) in DMF-H2O (5:1) at 0 °C for 3 days. This process yielded the desired Michael adducts with excellent efficiency and good stereoselectivity (up to 98% yield, up to 92% ee).

Brønsted acid catalyzed intramolecular allylic substitution reaction of secondary and tertiary allylic alcohols has been developed. A variety of 2-vinylchromans were efficiently prepared in moderate to excellent yields. The given method features wide substrate scope, operational simplicity, and mild, metal-free reaction conditions. The practicability of the method was demonstrated by a gram-scale reaction and further derivations of the product. Preliminarily studies on a catalytic asymmetric reaction were also undertaken.

2-Amino-5-nitro-4-(tetrazol-5-yl)-1,2,3-triazole (HANTT), its corresponding energetic salts and a dimeric azo compound are successfully synthesized. Compared to 5-nitro-4-(tetrazol-5-yl)-1,2,3-triazole (H2NTT), the neutral N-amino compound HANTT exhibits excellent properties in many aspects, including a higher density (ρ = 1.86 g cm–3), a better detonation performance (D
v = 8931 m s–1, P = 32.2 GPa) and a higher thermal decomposition temperature (T
d = 237 °C). Among the prepared materials, the hydroxylammonium energetic salt exhibits the best detonation performance (D
v = 9096 m s–1, P = 32.8 GPa) and an acceptable mechanical sensitivity (IS = 12 J, FS = 144 N). HANTT, the energetic salts and the azo compound are fully characterized by infrared spectroscopy, multinuclear NMR spectroscopy, elemental analysis and differential scanning calorimetry.

A unified heteroannelation method to achieve the synthesis of 1,3-dibenzyl-3,4-dihydropyrrolo[2,3-d]imidazole-2(1H)-thione derivatives with an iron catalyst is proposed. The annelation reaction follows a C(sp3)–C(sp3) radical coupling between a thiohydantoin and an O-acetyloxime. The synthetic approach enables access to several alkynylated thiohydantoins and O-acetyloximes with controlled selectivity toward C(sp3)–C(sp3) coupling rather than C(sp3)–C(sp3)–O coupling in moderate to high yields. An optimization study has been carried out by changing the catalyst loading, oxidants, solvents, and temperature. Synthesized compounds were characterized through 1H and 13C NMR and mass spectral studies.

A highly efficient and general synthetic protocol for both Henry and Michael reactions was developed using metal-free catalyst Triton B (benzyltrimethylammonium hydroxide) and isatins and chalcones, respectively. This methodology is inexpensive, the reagents are easy to handle, and the approach offers wide functional group tolerance of isatins and chalcones. The base catalyst Triton B is less toxic, recyclable, and reusable. This efficient method reduces reaction times, minimizes reagent excess, avoids chromatography, and is aligned with sustainable chemistry principles, offering eco-friendly applications in diverse industries.

An efficient approach is reported for the direct halodecarboxylation of hydroxyaromatic acids by using a readily available N-halosuccinimide (halo = Cl, Br) as the sole promoter in ethanol at room temperature without any other catalyst or additive. This environmentally friendly route tolerates a wide substrate scope with good to excellent yields under convenient conditions.

Synlett 2024; 35: V-DOI: 10.1055/s-0043-1774859Georg Thieme Verlag KG Rüdigerstraße 14, 70469 Stuttgart, GermanyArticle in Thieme eJournals:Table of contents

Synlett 2024; 35: 833-839DOI: 10.1055/s-0043-1774827[…]Georg Thieme Verlag KG Rüdigerstraße 14, 70469 Stuttgart, GermanyArticle in Thieme eJournals:Table of contents  |  Abstract  |  Full text

Synlett 2024; 35: A70-A86DOI: 10.1055/s-0040-1720631Georg Thieme Verlag KG Rüdigerstraße 14, 70469 Stuttgart, GermanyArticle in Thieme eJournals:Table of contents