Six-membered ring systems: with O and/or S atoms

A large variety of publications involving O- and S-6-membered ring systems have appeared in 2017. The importance of these heterocyclic compounds is highlighted by the huge number of publications on the total synthesis of natural oxygen derivatives and of other communications dedicated to synthetic derivatives. Reviews on stereoselective organocatalytic synthesis of tetrahydropyrans (17EJO4666), of tetrahydropyrans and their application in total synthesis of natural products (17CSR1661), on the synthesis of the less thermodynamically stable 2,6-trans-tetrahydropyrans (17S4899), on enantioselective synthesis of polyfunctionalized pyran and chromene derivatives (17TA1462), and on enantioselective and racemic total synthesis of camptothecins, including the formation of their pyran-2-one ring (17SL1134), have appeared. Advances in the transition metal-catalyzed synthesis of pyran-2/4-ones (17TL263), N-heterocyclic carbene (NHC)-catalyzed achiral synthesis of pyran-2-one, coumarin and (thio)chromone derivatives (17OBC4731), on the synthesis and transformation of 2H-pyran-2-ones (17T2529) and 2-styrylchromones (17EJO3115) into other heterocyclic compounds, have been surveyed. The strategies to build up the tetrahydropyranyl core of brevisamide (17H(95)81) and the reactions of ketyl radicals, generated from carbonyl derivatives under transition-metal photoredox-catalyzed conditions, leading to isochromen- and chroman-type compounds (17CC13093) were disclosed. Developments in the synthesis of pentafluorosulfanyl(chromene and coumarin) derivatives (17TL4803), photoswitchable D9-tetrahydrocannabinol derivatives (17JA18206), and aminobenzopyranoxanthenes with nitrogen-containing rings (17JOC13626) have been studied.info:eu-repo/semantics/publishedVersio

Carbene-Induced Intra- vs Intermolecular Transfer-Fluoromethylation of Aryl Fluoromethylthio Compounds under Rhodium Catalysis

The intra- vs intermolecular transfer-fluoromethylation of aryl fluoromethylthio compounds is proposed. Finely designed ArSCF₃ (<b>1a</b>) nicely releases its trifluoromethyl (CF₃) group intermolecularly under rhodium catalysis, whereas a difluoromethylated analogue, ArSCF₂H compound <b>1b</b> shows intramolecular reaction

Perfluoroalkyl Analogues of Diethylaminosulfur Trifluoride: Reagents for Perfluoroalkylthiolation of Active Methylene Compounds under Mild Conditions

Trifluoromethyl diethylaminosulfur difluoride (CF₃-DAST) was found to be an efficient reagent for the trifluoromethylthiolation of α-methylene-β-keto esters providing α-trifluoromethylthio-β-keto esters in good to high yields. α-Methylene-β-keto sulfones were also accepted as substrates by CF₃-DAST to furnish the corresponding α-trifluoromethylthio compounds. This strategy can be extended to perfluoroalkylthiolation reactions using perfluoroethyl-DAST (C₂F₅-DAST) and perfluoropropyl-DAST (C₃F₇-DAST)

Construction of Fluorinated Benzoxathiin Skeleton by Successive Perfluoro­phenyl­thiolation/Cyclization of Activated α‑Methylene Ketones by Perfluoro­phenyl Diethyl­amino­sulfur Difluoride

Pharmaceutically attractive fluorinated benzoxathiin (thiaflavan) skeleton <b>4</b> was directly constructed by the reaction of activated α-methylene ketones <b>1</b> such as β-keto esters, 1,3-diketone, and β-keto sulfones with a perfluorophenyl analogue of diethylaminosulfur trifluoride, C₆F₅-DAST, in high yields via successive perfluoro­phenyl­thiolation/cyclization reaction