Study of concerted and sequential photochemical Wolff Rearrangement by femtosecond UV-vis and IR spectroscopy

Photoinduced Wolff rearrangements were studied by femtosecond time-resolved UV-vis and IR transient absorption spectroscopy. For BpCN2COCH3 in acetonitrile the IR data indicate the presence of at least two mechanisms of ketene formation. The first process is fast proceeding in either 1BpCN2COCH3*, or in a hot carbene, or in both species, while the second is slow proceeding through the intermediacy of a relaxed carbene. The slow time constant of the ketene formation dynamics obtained by ultrafast IR (700 ps) spectroscopy agrees with the relaxed carbene decay of 800 +/- 100 ps obtained by UV-vis absorption spectroscopy.     

Use of cyclohexanedimethanol as a nonflammable organic solvent for industrial scale reversed phase chromatography

This work demonstrates that cyclohexanedimethanol is an effective nonflammable organic solvent for the pilot scale reversed phase chromatography of recombinant apolipoprotein A-I(Milano). Cyclohexanedimethanol has low viscosity in water, enabling the use of conventional low pressure process scale chromatography columns and hardware. Results from pilot scale manufacturing using a 30 cm diameter CG71M packed column indicate that a 5.7 log reduction in E. coli host cell protein with >80% yield can be obtained for the purification of apolipoprotein A-I(Milano).     

Benzylic bromination catalyzed by triphenylphosphine selenide via Lewis basic activation

The synthesis of benzyl bromides was achieved under mild reaction conditions using N-bromosuccinimide as a bromine source and triphenylphosphine selenide as a catalyst. These conditions were compatible with a variety of substrates including boronic esters, protected amines to give imines, and carboxylic acids (to give phthalides when ortho to the benzylic center). A preliminary mechanistic investigation utilizing calculated bond dissociation energies (BDE) is employed to rationalize how a Lewis base can activate a radical mechanism.     

Some essentially self-adjoint Dirac operators with spherically symmetric potentials

It is shown that the one electron Dirac operator in a stationary electric field is essentially self-adjoint, on the domain of infinitely differentiable functions of compact support, for a class of spherically symmetric potentials including the Coulomb potential, for atomic numbers less than or equal to 118. In addition, the domain of the closure of the perturbed operator is the same as the domain of the closure of the unperturbed operator. We also give an abstract theorem on domain-preserving essential self-adjointness for perturbed operators, which is perhaps of independent interest. This work was initiated while both authors were guests of the Institute for Theoretical Physics, University of Geneva, Switzerland. Partially supported by N.S.F. Grant G. P. 15239 A1 Supported by N. S. F. Grant G. P. 28933.