Aminolysis of carbamic esters, a model of the intermediate carboxybiotin in enzymatic carboxylations was studied in organic medium in the presence of a divalent cation. This study establishes electrostatic catalysis of aminolysis, the rate determining step of which is the collapse of the tetrahedral intermediate principally by carbon-nitrogen bond breacking. The results also account for the role of the divalent cation present in the carboxytransferase subunit of carboxylases.
Synthesis of Benzoxazolones from Nitroarenes or Aryl Halides
作者:Achim Porzelle、Michael D. Woodrow、Nicholas C. O. Tomkinson
DOI:10.1021/ol902885j
日期:2010.2.19
A simple and effective method for the preparation of benzoxazolones from nitroarenes or aryl halides is described. Partial reduction of a nitro group in the presence of a chloroformate followed by a microwave-assisted rearrangement/ring closure sequence provides a convenient and practical procedure to prepare this important pharmacophore. Rearrangement precursors were also accessed from aryl halides through transition-metal-catalyzed coupling.