Ketyl radicals are valuable reactive intermediates for synthesis. This review highlights exciting recent developments in the chemistry of ketyl radicals by comparing contemporary and more classical approaches for their generation and use.
Sulfonium salts are playing an increasingly significant role in contemporary organic synthesis.I n particular,t he generation of radicalsf rom sulfonium salts is af undamental process in Naturea nd has been the subject of investigation for over 50 years. However, general synthetic methods that use sulfonium salts as radical precursors are rare.T he advent of photoredox catalysis hast riggered an upsurge of interesti nt he radical chemistry of sulfonium salts and this review surveys recent applications of aryl-and alkylsulfonium saltsi nl ight-mediated, radical C À C bond formation. 1I ntroduction 2E arly Reports on the Photochemistry of Sulfonium Salts 3S ulfonium Salts in C À CB ond Formation 3.1 TheV alue of Arylsulfonium Salts in Light-Mediated C À CB ondF ormation 3.2 TheP reparation of BenzylsulfoniumSalts and their Reactivity in Light-Mediated C À CB ond Formation 3.3 TheD irect Preparation of Arylsulfonium Salts for Light-Mediated C À CB ond Formation 4C onclusion
SESAME is an instrument complex built in international co-operation and carried by the Rosetta lander Philae intended to land on comet 67P/Churyumov-Gerasimenko in 2014. The main goals of this instrument suite are to measure mechanical and electrical properties of the cometary surface and the shallow subsurface as well as of the particles emitted from the cometary surface. Most of the sensors are mounted within the six soles of the landing gear feet in order to provide good contact with or proximity to the cometary surface. The measuring principles, instrument designs, technical layout, operational concepts and the results from the first in-flight measurements are described. We conclude with comments on the consequences of the last minute change of the target comet and how to improve and to preserve the knowledge during the long-duration Rosetta mission.
A novel catalytic method for the direct C-H alkynylation of azulenes is developed. The gold catalyzed functionalization of this special carbacycle is achieved with hypervalent iodonium reagent TIPS-EBX under mild reaction conditions. With the aid of the developed procedure, several TIPS alkynylated azulene derivatives were synthesized bearing important functional groups for further functionalization.
Context. The Rosetta lander Philae successfully landed on the nucleus of comet 67P/Churyumov-Gerasimenko on 12 November 2014. Philae carries the Dust Impact Monitor (DIM) on board, which is part of the Surface Electric Sounding and Acoustic Monitoring Experiment (SESAME). DIM employs piezoelectric PZT sensors to detect impacts by submillimeter-and millimeter-sized ice and dust particles that are emitted from the nucleus and transported into the cometary coma. Aims. The DIM sensor measures dynamical data such as flux and the directionality of the impacting particles. Mass and speed of the particles can be constrained assuming density and elastic particle properties. Methods. DIM was operated during three mission phases of Philae at the comet: (1) before the separation of Philae from Rosetta at distances of about 9.6 km, 11.8 km, and 25.3 km from the nucleus barycenter. In this mission phase particles released from the nucleus on radial trajectories remained undetectable because of significant obscuration by the structures of Rosetta, and no dust particles were indeed detected; (2) during Philae's descent to its nominal landing site Agilkia, DIM detected one approximately millimeter-sized particle at a distance of 5.0 km from the nucleus' barycenter, corresponding to an altitude of 2.4 km from the surface. This is the closest ever dust detection at a cometary nucleus by a dedicated in situ dust detector; and (3) at Philae's final landing site, Abydos, DIM detected no dust impact which may be due to low cometary activity in the vicinity of Philae or due to shading by obstacles close to Philae, or both. Results. Laboratory calibration experiments showed that the material properties of the detected particle are compatible with a porous particle having a bulk density of approximately 250 kg m −3 . The particle could have been lifted off the comet's surface by sublimating water ice.
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