反应详情

In step d of Scheme 2, 3-chloro-1-(pyridin-3-yl)-1H-pyrazole-5-carboxylic acid (6e) is decarboxylated in the presence of copper (II) oxide in polar solvents such as N,N-dimethylformamide at temperatures from about 80° C. to about 140° C. to yield 3-(3-chloro-1H-pyrazol-1-yl)pyridine (5b). It was surprisingly discovered that this decarboxylation only occurs in the presence of copper (II) oxide. Several known decarboxylation agents from the literature such as, for example, hydrochloric acid (See alternate synthetic route, Example 14), sulfuric acid, and palladium (II) trifluoroacetate/trifluoroacetic acid (Pd(TFA)2/TFA) (See “CE-5”) did not yield the desired product.