| 摘要 |
<p>The present invention relates to a process for the preparation of a compound of the general formula (I), which comprises converting a compound of the general formula (II), in an aprotic organic solvent in the presence of a catalytically active amount of a strong acid (catalyst) or of an agent that liberates a strong acid or of an ammonium salt of a strong acid, it also being possible for the catalyst to be part of the starting material/product, into a compound of formula I, wherein R?5, R6 and R8¿ are each independently of the others a hydrogen atom, a nitro group, a sulfo group, a halogen atom, a pseudohalogen, a group COOR1 or CONHR2 or a C¿1-8? alkyl, C1-8 alkoxy or aryloxy radical, an amide group, a thioalkyl or thioaryl radical, an alkyl- or aryl-sulfonyl radical, an alkyl- or aryl-sulfinyl radical, a trifluoromethyl group or a phosphono group, R?1 and R2¿ being a hydrogen atom or a C¿1-8? alkyl radical or an aryl or aralkyl radical, R?10¿ is a group -C(O)CH¿2?C(O)CH3 and R?11¿ is a hydrogen atom or an acyl radical, or R?10 and R11¿ are a group -C(O)CH¿2?C(O)CH3. The process according to the invention is simple to perform and results in products of high chemical purity and high isomeric purity in a high yield.</p> |
