Synlett

Herein we report a method for pyrrole synthesis via iron-catalyzed carboamination/copper-mediated cyclization that is completely regioselective for the formation of 1,2,4-trisubstituted products. This two-step, one-pot process offers significant improvements to previously reported conditions including the use of a readily available copper(I) source and a markedly less arduous experimental procedure. Exploration of the substrate scope reveals a variety of arylacetylenes undergo pyrrole formation to afford single isomer products. Isotopic labelling data points to a mechanism involving activation of the alkyne moiety by the copper(I) reagent during the cyclization step.

Synlett 2022; 33: V-DOI: 10.1055/s-0042-1752338Georg Thieme Verlag KG Rüdigerstraße 14, 70469 Stuttgart, GermanyArticle in Thieme eJournals:Table of contents

Synlett 2022; 33: A151-A166DOI: 10.1055/s-0040-1720575Georg Thieme Verlag KG Rüdigerstraße 14, 70469 Stuttgart, GermanyArticle in Thieme eJournals:Table of contents

In this paper, a novel and efficient method is reported for the synthesis of novel 2-substituted 3-thioxoisoindolin-1-one derivatives. The method is based on the solvent-free reaction of 2-carboxybenzaldehyde with aliphatic amines and sulfur at 100 °C. This reaction is intensely significant, especially in pharmacy applications, due to the facile synthesis of asymmetric thioxoisoindolin-1-one derivatives with phthalimide backbones.

α-Metalated isocyanides are a versatile class of compounds that can easily be employed in various transformations, affording tangible libraries for screening campaigns. We report the ring-opening reactions of cyclic anhydrides and lactones with three different metalated isocyanides that readily give 4,5-disubstituted oxazoles, including useful drug-like synthetic intermediates with two functional groups as handles for further modifications.

A nine-step synthetic sequence to linear tetraquinanes involving [3+2] cycloaddition, chemoselective allylation, and ring-rearrangement metathesis as key steps is reported. A chemoselective allylation of 7-ketonorbornene was realized for the first time by using indium powder and allyl bromide. By this method, norbornene ketones can be selectively allylated in the presence of a cyclopentanone moiety to give good yields of monoallylated Barbier-type products.

A transition-metal-free novel route to access N-(o-halo)arylsulfoximines/sulfonimidamides is achieved by the reaction of sulfoximine/sulfonimidamide, aryne precursor, and CCl4/CBr4 in the presence of KF/18-crown-6. The in situ generated benzyne intermediate (from silyl aryl triflate) reacts with the nucleophile (sulfoximine/sulfonimidamide) and halide source (CCl4/CBr4) to yield the product in moderate to good yield. The protocol exhibits broad substrate scope. The regioisomers formed from the unsymmetric aryne precursor were separated effectively via column chromatography.

Potassium alkoxide was found to be a highly active catalyst for the nucleophilic trifluoromethylation of carbonyl compounds. The catalytic system was successfully applied to the reactions of both aldehydes and ketones, affording the corresponding trifluoromethylated products in high yields at low catalyst loadings (0.1–0.01 mol%) in several solvents, such as THF, toluene, and CH2Cl2. In addition, the potassium salt of a Ru(II) complex bearing an (S)-2,2′-bis[bis(3,5-dimethylphenyl)phosphinyl]-1,1′-binaphthalene [(S)-XylBINAP] ligand and two l-threoninate ligands, prepared in situ, catalyzed the enantioselective trifluoromethylation of aromatic aldehydes, although the ee values were not satisfactory (less than 20%).

A metal-free synthesis of useful β-keto sulfonyl fluorides has been established via radical fluorosulfonylation of ketone-derived vinyl acetates under photoredox organocatalysis by using 1-fluorosulfonyl benzoimidazolium (FABI) as the fluorosulfonyl radical source and oxygen-doped anthanthrene (ODA) as the photocatalyst. A series of aryl and alkyl β-keto sulfonyl fluorides as well as cyclic analogues can be readily obtained in moderate to high yields from widely available ketone starting materials.

4-Alkylpyridines are converted into conjugated 1,1-disubstituted alkenyl pyridines (vinyl pyridines) upon treatment with excess ethyl chloroformate, triethylamine, and Eschenmoser’s salt. The reaction proceeds under mild conditions via alkylidene dihydropyridine intermediates.