聚合甲醛   、                                                                                      
6-chloro-3-dimethylamino-indazole-1-carboxylic acid ethyl ester                                                                                                                                                                                              以
                                                                                         
甲酸                                                                                  为溶剂,
                                                                                                                                                    反应 5.0h,
                                                                                                                以Analogously to Example 49, 0.1 mol of 3-amino-6-chloroindazole-1-carboxylic acid ethyl ester and 0.25 mol of 40% strength formaldehyde solution in 150 ml of formic acid give 3-dimethylamino-6-chloroindazole-1-carboxylic acid ethyl ester (melting point: 98°-100° C; 69% of theory) in 5 hours at 100° C.的产率得到3-amino-6-chloro-indazole-1-carboxylic acid ethyl ester