Hindered biaryls have been simply prepared using diazonium salt precursors and an intramolecular free radical [1,5] ipso substitution protocol. The introduction of an additional substituent ortho to the diazonium group in the sigma aryl radical donor further enforces the formation of ipso substitution products and hence fully hindered biaryls are the favoured products.

The addition of a tri n-butylstannyl radical to arene and heteroarene sulfonate esters of homopropargyl alcohol triggers a sequence of [1,6] ipso-substitution followed by 6-endo addition and elimination to yield unusual 4-aryl-5,6-dihydro-1,2-oxathiin-2,2-dioxides and related heterocyclic systems.

The structure determination of C16H18O3S by single-crystal X-ray diffraction revealed the para regiochemistry of the title compound.

alpha-Lithiated (+)-(R)-para-tolyl vinyl sulfoxide reacts with alpha-selanylcarbonyl compounds to give the corresponding beta-hydroxy selenides. Subsequent Krief-Reich elimination affords enantiomerically pure mono-, di- and trisubstituted 2-sulfinylbuta-1,3-dienes.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

The title compound, C 16 H 17 NO 3 S, is the single adduct obtained by cycloaddition of (E)-(+)-(R)-2-p-toluenesulfinyl-1,3-pentadiene with maleimide. The absolute configuration of the stereocentres is established and some mechanistic aspects are deduced

Reaction of (E)-(+)-(R)-2-p-tolylsulfinyl-1,3-pentadiene 1 with maleimide afforded 3 as a single, enantiomerically pure adduct under very mild conditions. 3 resulted from exclusive endo approach by a completely diastereofacialselective route. On the other hand, heterodiene (+)-(S)-3-p-tolylsulfinyl-3-buten-2-one 2 smoothly reacted with sensitive 2-methylenetetrahydrofuran yielding 1:1 diastereomeric dioxaspirodducts 4a and 4b, readily separated by liquid chromatography.

Condensation of (R)-vinyl-p-tolylsulfoxide anion on carbonyl compounds led directly to chiral allylic sulfinylalcohols 1. By treatment with NBS/Me2S, these alcohols 1 were converted into the rearranged primary allylic bromides 2 via SN2' displacement. Optically pure (R)- and (S)-2-p-tolylsulfinyl-1,3-alkadienes 3 resulted from the action of KOH/ROH upon these bromides 2 via E2' eliminations.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

The title compounds were readily prepared respectively from (S)-3-p-tolylsulfinylbut-3-en-2-ol 3 and (S)-3-p-tolylsulfinylbul-3-en-2-one 4.

view Abstract Citations (11) References (31) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS A Study of E > 4 MeV Gamma Radiation from the Galactic Disk in the Region -20 degrees < L < 20 Lavigne, J. M. ; Mandrou, P. ; Niel, M. ; Agrinier, B. ; Bonfand, E. ; Parlier, B. Abstract Gamma radiation with E > 4 MeV was measured in the galactic disk region -20° < l < 20° in the course of two balloon flights launched during the 1976 - 1977 CNES Brazilian balloon campaign. The energy spectrum of the galactic disk gamma-ray emission was determined between 4 and 25 MeV. The results suggest that the gamma-ray emission from the galactic disk extends to energies of several MeV, implying a strong contribution from cosmic-ray electrons. Publication: The Astrophysical Journal Pub Date: September 1986 DOI: 10.1086/164507 Bibcode: 1986ApJ...308..370L Keywords: Balloon-Borne Instruments; Galactic Radiation; Galactic Structure; Gamma Ray Astronomy; Milky Way Galaxy; Electromagnetic Radiation; Electron Radiation; Statistical Analysis; X Ray Telescopes; Astrophysics; GALAXIES: MILKY WAY; GAMMA RAYS: GENERAL; RADIATION MECHANISMS full text sources ADS |

The field of gamma-ray astronomy in the energy range from ten to several hundred MeV is severely limited by the angular resolution that can be achieved by present instruments. The identification of some of the point sources found by the COS-B mission and the resolution of detailed structure existing in those sources may depend on the development of a new class of instrument. The coded aperture mask telescope, used successfully at X-ray energies hold the promise of being such an instrument. A prototype coded aperture telescope was operated in a tagged photon beam ranging in energy from 23 to 123 MeV. The purpose of the experiment was to demonstrate the feasibility of operating a coded aperture mask telescope in this energy region. Some preliminary results and conclusions drawn from some of the data resulting from this experiment are presented.

The application of the coded aperture mask to high energy gamma-ray astronomy will provide the capability of locating a cosmic gamma-ray point source with a precision of a few arc-minutes above 20 MeV. Recent tests using a mask in conjunction with drift chamber detectors have shown that the expected point spread function is achieved over an acceptance cone of 25 deg. A telescope employing this technique differs from a conventional telescope only in that the presence of the mask modifies the radiation field in the vicinity of the detection plane. In addition to reducing the primary photon flux incident on the detector by absorption in the mask elements, the mask will also be a secondary radiator of gamma-rays. The various background components in a CAMTRAC (Coded Aperture Mask Track Chamber) telescope are considered. Monte-Carlo calculations are compared with recent measurements obtained using a prototype instrument in a tagged photon beam line.

The Agathe experiment is a 1 m2 spark chamber sensitive in the 5–50 MeV energy range designed for use on a stratospheric balloon. The different methods used to determine the efficiency, angular resolution and energy are described. Efficiency calibrations are made in gamma ray beams at different energies. The results are verified by a Monte Carlo calculation then extended to higher energies. The photon energy is determined by calibrations in electron beams and in gamma ray beams; two methods are compared and discussed.

view Abstract Citations (12) References (30) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Study of diffuse cosmic and atmospheric gamma radiation using a spark chamber in the energy range 4 MeV-100 MeV Lavigne, J. M. ; Niel, M. ; Vedrenne, G. ; Agrinier, B. ; Bonfand, E. ; Parlier, B. ; Rao, K. R. Abstract An attempt is made to report results obtained during two flights of the Agathe Balloon experiment in Brazil. The experiment was apparently carried out to determine the total atmospheric and cosmic gamma-ray flux in various energy ranges between 4 and 100 MeV by means of flux measurements with a spark chamber during the balloon's ascent. The atmospheric component in the energy ranges of 4-10 MeV, 10-25 MeV, and 25-100 MeV is estimated and compared with previous results; the spectrum of the total diffuse component for the same energy ranges is also measured. Publication: The Astrophysical Journal Pub Date: October 1982 DOI: 10.1086/160382 Bibcode: 1982ApJ...261..720L Keywords: Atmospheric Radiation; Cosmic Rays; Diffuse Radiation; Gamma Rays; Balloon Flight; Flux (Rate); Spark Chambers; Space Radiation full text sources ADS |