Outer layer scintillating fiber for low-energy β-ray detection.

Standard plastic scintillating fiber cannot detect low-energy β-rays as the cladding prevents them from reaching the fiber core. We developed an outer-layer scintillating (OLS) fiber with a plastic scintillator on the outermost layer for low-energy β-ray detection. The concept of fiber construction is presented.

Enantioselective Lewis acid-catalyzed Mukaiyama-Michael reactions of acyclic enones. Catalysis by allo-threonine-derived oxazaborolidinones.

allo-Threonine-derived O-aroyl-B-phenyl-N-tosyl-1,3,2-oxazaborolidin-5-ones 1g,n catalyze the asymmetric Mukaiyama-Michael reaction of acyclic enones with a trimethylsilyl ketene S,O-acetal in high enantioselectivity. A range of alkenyl methyl ketones is successfully employed as Michael acceptors affording ee values of 85-90% by using 10 mol % of the catalyst. The use of 2,6-diisopropylphenol and tert-butyl methyl ether as additives is found to be essential to achieve high enantioselectivity in these reactions.