PROCESS FOR THE PREPARATION OF 4-HALO-6-HYDROXY-2H-PYRAN-3(6H)-ONES AND THEIR USE IN THE SYNTHESIS OF GAMMA-PYRONES

摘要

Prepn. of a gamma pyrole of formula (I) comprises heating a 4-halo-dihydropyran of formula (II) or an 6,6'-oxy-bis 4-halo-2H-pyran-3(6H)-one of formula (V) in an aq. acid soln. until hydrolysis is practically complete. (where R is H, 1-4C alkyl, phenyl or benzyl; R' is H, 1-4C alkyl or -COR" where R" is methyl, ethyl or phenyl; R'" is H or 1-4C alkyl and X is Cl or Br).