Chemistry of acetylenic ethers LIV: Addition of diazo compounds to acetylenic ethers and thioethers

Ethoxyethyne slowly adds diazomethane to yield 4‐ethoxypyrazole I, the structure of which has been proved by synthesis from 1,1,2,3,3‐pentaethoxypropane IV and hydrazine. Ethylthioethyne V, on the contrary, is converted by diazomethane into 3‐ethylthiopyrazole VI, the structure of which has been proved by synthesis from 3‐aminopyrazole X. Ethyl diazoacetate does not react with ethoxyethyne, but can be added to ethylthioethyne, yielding presumably 5‐ethoxycarbonyl‐3‐ethylthiopyrazole.