Cyclizations and cycloadditions of acetylenic sulfones on solid supports

Acetylenic sulfones attached to solid supports by means of ester linkers were employed in a variety of cyclization and cycloaddition reactions, followed by cleavage of the products from the resin by ester hydrolysis or reductive desulfonylation.     

Rearrangements of the Diels-Alder cycloadducts obtained from acetylenic sulfones and 1,3-diphenylisobenzofuran

1,3-Diphenylisobenzofuran afforded Diels-Alder cycloadducts 4a,b with n-butyl- and phenyl-substituted acetylenic sulfones 3a,b, respectively. The products underwent various types of rearrangements under pyrolytic, acid-catalyzed, and photochemical conditions. In the presence of acid, or upon heating in xylenes, they afforded the ketones 5a,b. In addition, the dehydration product 7a was produced from the pyrolysis of 4a, and the unexpected transposed ketone 6b was generated under acid-catalyzed or pyrolytic conditions from 4b via a postulated epoxide intermediate. The photolysis of 4a afforded ketone 5a as the sole isolated product, whereas 5b afforded oxepin 8b and indenyl phenyl ketone 9b. The formation of the latter two products can be rationalized by a series of pericyclic reactions. These include an intramolecular [2+2] cycloaddition, followed by a 1,3-dipolar cycloreversion, for the transformation of 4b to 8b and a series of electrocyclic and [1,3]sigmatropic reactions to convert 8b into 9b.     

¹⁵C(d,p)¹⁶C reaction and exotic behavior in ¹⁶C

We have studied the 1?C(d,p)1?C reaction in inverse kinematics using the Helical Orbit Spectrometer at Argonne National Laboratory. Prior studies of electromagnetic-transition rates in 1?C suggested an exotic decoupling of the valence neutrons from the core in that nucleus. Neutron-adding spectroscopic factors give a different probe of the wave functions of the relevant states in 1?C. Shell-model calculations reproduce both the present transfer data and the previously measured transition rates, suggesting that 1?C may be described without invoking very exotic phenomena.     

Determination of the axial-vector weak coupling constant with ultracold neutrons

A precise measurement of the neutron decay β asymmetry A? has been carried out using polarized ultracold neutrons from the pulsed spallation ultracold neutron source at the Los Alamos Neutron Science Center. Combining data obtained in 2008 and 2009, we report A? = -0.119?66±0.000?89{-0.001?40}{+0.001?23}, from which we determine the ratio of the axial-vector to vector weak coupling of the nucleon g{A}/g{V}=-1.275?90{-0.004?45}{+0.004?09}.     

THE MASS SPECTRAL FRAGMENTATION OF SULFENAMIDES AND RELATED COMPOUNDS

Abstract

Plausible mechanistic interpretations of the major ions formed in the mass spectrometric fragmentation of a number of sulfenamides and related derivatives are presented. High resolution mass spectrometry was used to determine the composition of most of the ions investigated.     

Comparison of frequency,field, and time domain ferromagnetic resonance methods

We present vector network analyzer ferromagnetic resonance measurements of epitaxial Fe films having a thickness of 16 monolayers. Our objective is to test the reliability of this novel frequency domain technique with respect to frequency and damping. For this purpose we compare vector network analyzer ferromagnetic resonance to pulsed inductive microwave magnetometry, time resolved magneto-optic Kerr effect (both methods in the time domain), and conventional ferromagnetic resonance (measured in the field domain) in terms of position and width of the ferromagnetic resonance. In addition, we compare the various techniques with respect to the signal to noise ratio of the raw data. All data is obtained using the same well characterized ultrathin magnetic Fe/GaAs (0 0 1) film. Finally, we demonstrate the potential of the vector network analyzer ferromagnetic resonance technique for the investigation of nano-structured magnetic elements having nonuniform magnetization configuration. The absorption spectrum of Permalloy disks with a diameter of 200 nm and a thickness of 15 nm shows up to eight distinct resonance peaks. The spatial structure of the corresponding modes was derived from numerical calculations and reveals that azimuthal modes up to the fifth order have been observed inductively.     

Synthesis of Pyridazinones through the Copper(I)‐Catalyzed Multicomponent Reaction of Aldehydes,Hydrazines, and Alkynylesters

The copper‐catalyzed multicomponent cyclization reaction, which combined aldehydes, hydrazines, and alkynylesters, was applied in the synthesis of pyridazinones. The reaction was regioselective and gave only six‐membered pyridazinones in the complete absence of five‐membered pyrazoles or a regioisomeric mixture. During this investigation, the use of 2‐halobenzaldehyde as the starting material, under identical reaction conditions, gave 6‐(2‐ethoxyphenyl)pyridazinones after sequential Michael addition/1,2‐addition/Ullmann cross‐coupling reactions.