4-Chloroethynyl-1,3-dimethylpyrazole

In 1973, the unexpected transformation of 4-chloroethynyl-l,3,5-trimethylpy-razole under the action of sodium amide in liquid ammonia into 5-aminomethyl-4-ethynyl-l,3-dimethylpyrazole in 85% yield was reported (73IZV2166). Within... 

From 4-chloroethynyl-l,3-dimethylpyrazole 80% of 4-ethynyl-5-chloro-l,3-dimethylpyrazole was obtained. There is simultaneous formation of about 10% of 4-ethynyl-l,3-dimethylpyrazole (76IZV2148 77IZV2306) (Scheme 106). 

It should be noticed that N-unsubstituted 4-chloroethynyl-3,5-dimethylpyrazole under the action of both NaNH2 and n-butyllithium leads only to 4-ethynyl-3,5-dimethylpyrazole (69IZV927) (Scheme 104). 

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