| 摘要 |
<p>The invention provides a method of carrying out the cyclization of the compound of formula (14) to the compound (15), wherein first a non-cyclic intermediate (16) is prepared by the treatment with 1 to 1.5 equivalents of 1,1'-carbonyldiimidazole of formula (8), which further converts into the cyclic product (15) by treatment with heat or a base. The present method of cyclization of the compound (14) to the compound (15) is preferred and distinguished from the prior methods by the use of a lower amount of the expensive carbonylation agent, which is compensated by use of a cheap base (17), wherein R means an alkyl and M means an alkali metal.</p> |
