| 摘要 |
<p>The present invention relates to a process for the preparation of compounds of formula wherein R<sub>1</sub>, R<sub>2</sub> and R<sub>3</sub> are each independently of the others hydrogen or C<sub>1</sub>-C<sub>4</sub>alkyl, by a) reacting compounds of formula (II) wherein R<sub>1</sub>, R<sub>2</sub> and R<sub>3</sub> are as defined for formula (I) and X is bromine or chlorine, with a compound of formula (III) wherein R<sub>4</sub> is hydrogen or C<sub>1</sub>-C<sub>4</sub>alkyl, in the presence of a base and catalytic amounts of at least one palladium complex compound, to form compounds of formula (IV) wherein R<sub>1</sub>, R<sub>2</sub>, R<sub>3</sub> and R<sub>4</sub> are as defined for formula (I), and b) converting those compounds, using a reducing agent, into compounds of formula (I).</p> |
