Studies on difficult intramolecular hydroaminations in the context of four syntheses of alkaloid natural products.

Examples of intramolecular alkene hydroaminations forming six-membered ring systems are rare, especially for systems in which the double bond is disubstituted. Such cyclizations have important synthetic relevance. Herein we report a systematic study of these cyclizations using recently developed Cope-type hydroamination methodologies.

Efficacy of commercial vaccines in protecting chickens and ducks against H5N1 highly pathogenic avian influenza viruses from Vietnam.

Highly pathogenic (HP) H5N1 avian influenza (AI) viruses continue to circulate in Asia and have spread to other regions of the world. Though attempts at eradication of the viruses during various outbreaks have been successful for short periods of time, new strains of H5N1 viruses continue to emerge and have become endemic in parts of Asia and Africa. Vaccination has been employed in Vietnam as part of AI control programs.

Simple reaction conditions for the formation of ketonitrones from ketones and hydroxylamines.

The condensation of ketones and hydroxylamines to form ketonitrones was reinvestigated by using thermal conditions previously found to minimize hydroxylamine decomposition (t-BuOH, 110 degrees C). This simple approach allows the formation of exocyclic, acyclic, and alpha,beta-unsaturated ketonitrones with benzylic, linear, and branched nitrogen substituents in modest to excellent isolated yields.

Ketonitrones via Cope-type hydroamination of allenes.

The synthesis of ketonitrones from N-alkylhydroxylamines and monosubstituted allenes is accomplished via a Cope-type hydroamination reaction in moderate to good yields. Allenes also undergo a similar reaction with aqueous hydroxylamine to give oximes in excellent yield. DFT calculations support a proposed concerted, five-membered hydroamination process, and calculated transition state energies are in excellent agreement with experimental observations.