Enantioselective synthesis of aminobenzazepinones

Enantioselective synthesis of constrained trans-aminobenzazepinone utilizing palladium-mediated Jeffery-Heck reaction and rhodium(II) catalyzed asymmetric hydrogenation as key steps are described. Diverse functional groups such as alkyl, aryl, basic or amino acid moieties were introduced with minimal racemization.     

Direct observation of a "devil's staircase" in wave-particle interaction

We report the experimental observation of a "devil's staircase" in a time-dependent system considered as a paradigm for the transition to large-scale chaos in the universality class of Hamiltonian systems. A test electron beam is used to observe its non-self-consistent interaction with externally excited wave(s) in a traveling wave tube (TWT). A trochoidal energy analyzer records the beam energy distribution at the output of the interaction line. An arbitrary waveform generator is used to launch a prescribed spectrum of waves along the slow wave structure (a 4 m long helix) of the TWT. The resonant velocity domain associated to a single wave is observed, as well as the transition to large-scale chaos when the resonant domains of two waves and their secondary resonances overlap. This transition exhibits a "devil's staircase" behavior for increasing excitation amplitude, due to the nonlinear forcing by the second wave on the pendulum-like motion of a charged particle in one electrostatic wave.     

Efficient synthesis of 5-substituted-4,5-dihydro-1,2,4-triazin-6-ones and 5-substituted-1,2,4-triazin-6-ones

Treatment of methyl α-(dimethylarninomethyleneamino)carboxylates 1 (from α-amino acids and dimethylformamide dimethylacetal) with hydrazine gives 5-substituted-4,5-dihydro-1,2,4-triazin-6-ones 2 , which are smoothly dehydrogenated to 5-substituted-1,2,4-triazin-6-ones 3 with potassium permanganate in acetone/acetic acid.     

Comparing the 2,2′‐Biphenylenedithiophosphinate Binding of Americium with Neodymium and Europium

Advancing our understanding of the minor actinides (Am, Cm) versus lanthanides is key for developing advanced nuclear‐fuel cycles. Herein, we describe the preparation of (NBu₄)Am[S₂P(^tBu₂C₁₂H₆)]₄ and two isomorphous lanthanide complexes, namely one with a similar ionic radius (i.e., Nd^III) and an isoelectronic one (Eu^III). The results include the first measurement of an Am?S bond length, with a mean value of 2.921(9) Å, by single‐crystal X‐ray diffraction. Comparison with the Eu^III and Nd^III complexes revealed subtle electronic differences between the complexes of Am^III and the lanthanides.     

Catalytic asymmetric syntheses of tyrosine surrogates

Amino acid esters 5-11 as tyrosine mimics have been synthesized in excellent enantioselectivity (up to 99.6% ee) and in good overall chemical yields. The key step in the sequence was the Burk's [Rh(COD)(2R,5R)-Et-DuPhos]BF4-catalyzed asymmetric hydrogenation of enamides with a variety of reactive functional groups.