Lewis Base/Brønsted Acid Co‐catalyzed Enantioselective Sulfenylation/Semipinacol Rearrangement of Di‐ and Trisubstituted Allylic Alcohols

An enantioselective sulfenylation/semipinacol rearrangement of 1,1‐disubstituted and trisubstituted allylic alcohols was accomplished with a chiral Lewis base and a chiral Brønsted acid as cocatalysts, generating various β‐arylthio ketones bearing an all‐carbon quaternary center in moderate to excellent yields and excellent enantioselectivities. These chiral arylthio ketone products are common intermediates with many applications, for example, in the design of new chiral catalysts/ligands and the total synthesis of natural products. Computational studies (DFT calculations) were carried out to explain the enantioselectivity and the role of the chiral Brønsted acid. Additionally, the synthetic utility of this method was exemplified by an enantioselective total synthesis of (?)‐herbertene and a one‐pot synthesis of a chiral sulfoxide and sulfone.     

Genaue Bestimmung des Schwefels in anorganischen Schwefelverbindungen nach dem Verbrennungsverfahren

Zusammenfassung Durch Verbrennung mit Vanadiumpentoxid als Sauerstoffüberträger im Stickstoffstrom und Herabsetzung des Sauerstoffpotentials der Verbrennungsgase über metallischem Kupfer gelingt es, 99,5% des Schwefels in leicht erfaßbares Schwefeldioxid zu überführen. Für Proben mit einem Schwefelgehalt zwischen 1 und 8 mg beträgt die Standardabweichung 5,2 g.

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Precise determination of sulphur in inorganic sulphur compounds by the combustion method

Summary By combustion with vanadium pentoxide as oxidant in a nitrogen current and after reduction of the oxygen potential of the combustion gas over metallic copper, 99,5% of the total sulphur are obtained as easily detectable sulphur dioxide. The standard deviation of the method is 5.2 g for samples containing between 1 and 8 mg of sulphur.