Verfahren zur Herstellung von 2-Coumaranon

摘要

Prodn. of 2-coumaranone (I) is by: (1) vapour-phase reaction of glyoxylic acid (II) with cyclohexanone (III) in the presence of a dehydrogenation catalyst; (2) vapour-phase contacting a crude reaction mixt. with a dehydrogenation catalyst, the reaction mixt. being obtained by condensn. of (II) with (III) in known manner; or (3) vapour-phase contacting a cyclohexanone-2-acetic acid (IV) and/or cyclohexanol-2-acetic acid (V) soln. with a dehydrogenation catalyst. Carrier gas comprising N2 and/or H2 is used. Reaction temp. is at least 150 deg.C. Catalyst comprises Pd or Pt on inert support with surface area above 1 (esp. above 50) m2/g. In processes (1) and (2), soln. of (II) and (III) in HOAc or HOAc/H2O is used and by-produced (IV) and (V) are recycled.